BYPASS GRAFTING OPERATIONS USING CONVENTIONAL TECHNIQUE WITH OFF-PUMP

CORONARY ARTERY BYPASS GRAFTING IN TWO IDENTICAL GROUPS CONDUCTED AT THE

PENANG HOSPITAL (1999-2000)

BY

DR. V ASANTHA KASINATHAN

M.B.B.S. (MYSORE)

Dissertation Submitted In Partial Fullfilment Of The Requirement For The Degree Of Master Of Medicine (General Surgery) ,

UNIVERSITI SAINS MALAYSIA YEAR 2001

II SUPERVISORS

UNIVERSITI SAINS MALAYSIA

1. Dr Anas Sjahroeddin Ressang

Pakar Bedah Dan Pensyarah

J abatan Surgeri

Universiti Sains Malaysia

Kubang Kerian

Kelantan

2. Dr. Lin Naing

Pakar Statistics

J abatan Perubatan Masyarakat

Universiti Sains Malaysia

Kubang Kerian

Kelantan

MINISTRY OF HEALTH

1. Mr. Mohd. Hamzah KamaruIzamam Md (UKM), FReS (Edin)

Pakar Bedah Kardiothorasik

J abatan Pembedahan Kardiothorasik

Hospital Pulau Pinang

ii

III ACKNOWLEGEMENTS

I would like to express my thanks to Mr. Mohd Harnzah Bin Karnarulzarnan and Mr

Prashant Joshi for all their guidance and advice during my training in the Department of

Cardiothoracic surgery at Penang Hospital. They had suggested this topic for research and

it was subsequently presented at the Biannual Cardiothoracic Surgery Conferrence on

16th - 18th February 2001. I would also like to express a special thanks to Dr. Lin Naing

for being so helpful and guiding me with the statistical analysis of this study. I would like

to thank all the staff of the Cardiothoracic surgery clinic, CICU, Al ward, operation

theatre staff, record office staff and all my colleagues and friends for their co-operation

and valuable suggestions.

iii

IV TABLE OF CONTENTS

CONTENTS PAGE

I FRONTISPIECE ........................................................................................................... i

II SUPERVISORS ........................................................................................................... ii

m ACKNOWLEGEMENTS ........................................................................................... iii

IV TABLE OF CONTENTS ............................................................................................ iv

V LIST OF TABLES ...................................................................................................... vi

VI LIST OF FIGURES ................................................................................................... viii

VIT ABSTRACT IN BAHASA MALAYSIA .................................................................... x

VITI ABSTRACT IN ENGLISH ........................................................................................ xii

IX QUOTATIONS: ........................................................................................................ xiii

1 INTRODUCTION ........................................................................................................ 1

2 LITERATURE REVIEW ............................................................................................. 3

2.1 HISTORY ........................................................................................................ 3

2.2 ANATOMY ..................................................................................................... 7

2.3 INCIDENCE .................................................................................................. 11

2.4 INDICATIONS OF OFF-PUMP CABG ....................................................... 11

2.6 ADVERSE EFFECTS OF CPB CABG ......................................................... 12

2.6.1 Renal Failure ...................................................................................... 14

2.6.2 Cerebral Damage ................................................................................ 14

2.6.3 Hepatic Failure ................................................................................... 17

2.6.4 Hematological Disorders .................................................................... 17

2.6.5 Other Factors ...................................................................................... 19

2.7 INCIDENCE OF MAJOR POST-OPERATIVE COMPLICATIONS WITH AND WITHOUT CPB IN A STUDY DONE BY ENIO BUFFALO IN 1995 .......................................................................................................... 19

2.8 COST- EFFECTIVENESS ............................................................................ 20

3 OBJECTIVE OF STUDy .......................................................................................... 22

4 MATERIALS AND METHOD ................................................................................. 24

4.1 GENERAL DESCRIPTIONS ........................................................................ 24

4.1.1 Pre-operative preparation ................................................................... 25

4.1.2 Laboratory assessment ....................................................................... 26

4.1.3 Pre-operative checklist ....................................................................... 26

4. 1.4 Intra operative procedure ................................................................... 27

4.1.5 Post-operative monitoring at the coronary intensive care unit. .......... 38

iv

4.2 IN"CLUSION CRITERIA ............................................................................... 39

4.3 EXCLUSION CRITERIA .............................................................................. 39

4.4 STATISTICAL ANALYSIS .......................................................................... 40

4.5 NULL HYPOTHESIS (Ho) ............................................................................ 40

4.6 ALTERNATNE HYPOTHESIS (Hd ........................................................... 40

5 RESULTS .................................................................................................................. 41

5.1 Pre and post operative renal status ................................................................. 51

5.2 Renal profile ................................................................................................... 58

5.3 Duration of CICU stay ................................................................................... 60

5.4 Treatment with inotropes ............................................................................... 63

5.5 Gross neurological status ............................................................................... 67

5.6 Post operative bleeding .................................................................................. 69

5.7 Post operative blood transfusion .................................................................... 74

5.8 Post operative wound infection ...................................................................... 77

5.9 Post operative chest complications ................................................................ 82

5.10 Angina ............................................................................................................ 82

5.11 Pericardial effusion ........................................................................................ 86

5.12 Ejection fraction of the heart .......................................................................... 90

5.13 Preoperative risk factors ................................................................................. 95

6 DISCUSSION .......................................................................................................... III

7 CONCLUSION ........................................................................................................ 120

8 FUTlJRE TREND .................................................................................................... 121

9 LIMITATIONS, RECOMMENDATIONS AND SUGGESTIONS ........................ 124

10 REFERENCES ........................................................................................................ 126

11 APPENDICES ......................................................................................................... 139

11.1 Appendix I (Clinical findings related to coronary heart disease) ................. 139

11.2 Appendix IT (Clinical findings related to lung collapse) .............................. 140

11.3 Appendix ill (Risk factors of interest) ......................................................... 141

11.4 Appendix N (Definition of risk factors) ..................................................... 142

11.5 Appendix V (Radiological findings of pneumonia) ..................................... 148

11.6 Appendix VI (Radiological findings of lung collapse) ................................ 149

11.7 Appendix VII (Radiological findings of pleural effusion) ........................... 150

11.8 Appendix VIn (Coronary angiogram) .......................................................... 150

11.9 Appendix IX (A glossary of tenns used in the study) .................................. 151

11.10 Appendix X (Patients name and RIN, VC) . ................................................. 155

v

V LIST OF TABLES

Table 2.1 Incidence of major post-operative complications with and without CPB in a study done by Enio Buffalo in 1995 ............................................. 20

Table 2.2 Showing the cost of OPCAB and CPB CABG at Penang Hospital, Penang .......................................................................................................... 21

Table 5.1 Showing the age and sex distribution among the CPB and OPCAB CABG patients ............................................................................................. 42

Table 5.2 Showing the distribution of race, sex and age group among the CPB and OPCAB CABG patients ........................................................................ 43

Table 5.3 Shows the youngest and oldest patients in OPCAB and CPB CABG ......... 46

Table 5.4 Shows the mean age in the male (a) and female (b) patients in OPCAB and CPB CABG ............................................................................................ 47

Table 5.5 The univariate and multivariate analysis of OPCAB (50 cases) and CPB ( 50 cases) CABG operation performed the Cardiothoracic surgery unit at Penang Hospital, Penang ...................................................... 49

Table 5.6 Shows pre-operative serum creatinine level in OPCAB and CPB CABG patients ............................................................................................. 52

Table 5.7 Shows post operative serum creatinine level in CPB and OPCAB CABG patients ............................................................................................. 55

Table 5.8 Shows pre-operative renal failure in CPB and OPCAB CABG patients ......................................................................................................... 59

Table 5.9 Shows the extubation time in CPB and OPCAB CABG patients ............... 61

Table 5.1 0 The intra-operative use of inotrope in CPB and OPCAB CABG patients ......................................................................................................... 63

Table 5.11 Shows the age and sex distribution in pre-operative stroke in CPB and OPCAB CABG patients .............................................................................. 67

Table 5.12 Shows post-operative bleeding in CPB and OPCAB CABG patients ........ 70

Table 5.13 Shows the type of transfusion of blood products in the post-operative period in CPB and OPCAB CABG patients ............................................... 75

Table 5.14 Shows the incidence of sternal wound infection in CPB and OPCAB CABG patients ............................................................................................. 78

Table 5.15 Shows the incidence of leg wound infection in CPB and OPCAB CABG patients ............................................................................................. 80

Table 5.16 Shows a comparison of stable angina and unstable angina in pre-operative CPB and OPCAB CABG patients ................................................ 83

Table 5.17 Shows the pre-operative pericardial effusion in CPB and OPCAB CABO patients ............................................................................................. 86

vi

Table 5.18 Shows the post-operative pericardial effusion in CPB and OPCAB CABG patients ............................................................................................. 88

Table 5.19 Shows the pre-operative ejection fraction of the heart in CPB and OPCAB CABG patients ............................................................................... 91

Table 5.20 Shows the pre-operative incidence of smoking in CPB and OPCAB CABG patients ............................................................................................. 96

Table 5.21 Shows the comparison of pre-operative risk of family history of heart disease in CPB and OPCAB CABG patients ............................................... 99

Table 5.22 Shows the comparison of pre-operative risk of diabetes mellitus in CPB and OPCAB CABG patients .............................................................. 1 01

Table 5.23 Shows the pre-operative risk factor of hypercholesterolemia in CPB and OPCAB CABG patients ...................................................................... 1 05

Table 5.24 Shows the pre-operative risk factor of hypertension in CPB and OPCAB CABG patients ............................................................................. 107

Table 5.25 Shows the pre-operative incidence of chronic obstructive airway disease (COAD) in CPB and OPCAB CABG patients .............................. 109

vii

VI LIST OF FIGURES

Figure 2.1

Figure 2.2

Figure 2.3

Figure 4.1

Figure 4.2

Figure 4.3

Figure 4.4

Figure 4.5

Figure 4.6

Figure 4.7

Figure 5.1

Figure 5.2

Figure 5.3

Figure 5.4

Figure 5.5

Figure 5.6

Figure 5.7

Figure 5.8

Figure 5.9

Diagram A ...................................................................................................... 8

Diagram B .................................................................................................... 10

Pathophysiology of pump syndrome ............................................................ 13

Shows the removal of the long saphenous vein from the leg ....................... 28

Shows the incision being enlarged with a pair of fine scissors ................... .32

The reversed scissors are helpful to enlarge the incision in the other direction ........................................................................................................ 33

Graduated probes can be passed into the artery to measure the internal diameter, which in this case is 2 mm. The probes are also useful in detecting narrowings in the vessel and distal artery ..................................... 34

Two further bites of this continuous suture are inserted before sliding the vein down into position .......................................................................... 35

Once the continuous suture has been inserted, the knot is tied and the suture is cut. In using Prolene , which is designed to pull through very easily, care must be taken not to tie the knot too tight and thus narrow the anastomosis by purse - stringing it. ........................................................ 36

Just before closing the chest, the grafts to the right and left anterior descending coronary arteries are checked to ensure that there is no leak from the anastomoses ................................................................................... 3 7

Shows the race distribution of patients who had undergone CPB CABG ........................................................................................................... 44

Shows the distribution of race in OPCAB CABG ....................................... 45

The pre-operative levels of serum creatinine in CPB and OPCAB CABG patients ............................................................................................. 54

The post operative levels of serum creatinine in CPB and OPCAB CABG patients ............................................................................................. 57

Shows the extubation time in OPCAB CABG and CPB CABG patients ......................................................................................................... 62

Shows the age, sex distribution and the incidence of inotropes use in CPB and OPCAB CABG patients ................................................................ 64

Shows the age distribution and the incidence of inotrope use in female CPB and OPCAB CABG patients ................................................................ 65

Shows the age distribution and the incidence of inotrope use in male CPB and OPCAB CABG patients ................................................................ 66

Shows the age and sex distribution of post-operative stroke in CPB and OPCAB CABG patients ........................................................................ 68

viii

Figure 5.10 A comparison of post operative bleeding in CPB and OPCAB CABG male patients ................................................................................................. 72

Figure 5.11 A comparison of post operative bleeding in CPB and OPCAB CABG female patients .............................................................................................. 73

Figure 5.12 Shows the types of blood products tranfused in the CPB and OPCAB CABG patients ............................................................................................. 76

Figure 5.13 Shows the incidence sternal wound infection in CPB and OPCAB CABG patients ............................................................................................. 79

Figure 5.14 Shows the incidence of post operative leg wound infection in CPB and OPCAB CABG patients .............................................................................. 81

Figure 5.15 Shows the incidence of stable angina in CPB and OPCAB CABG patients ......................................................................................................... 84

Figure 5.16 Shows the incidence of unstable angina in CPB and OPCAB CABG patients ......................................................................................................... 85

Figure 5.17 Shows the incidence of pre-operative pericardial effusion in CPB and OPCAB CABG patients ............................................................................... 87

Figure 5.18 Shows the incidence of post-operative pericardial effusion in CPB and OPCAB CABG patients ............................................................................... 89

Figure 5.19 Shows the incidence of pre-operative ejection fraction in CPB and OPCAB CABG patients ............................................................................... 93

Figure 5.20 Shows the incidence of post operative ejection fraction in CPB and OPCAB CABG patients ............................................................................... 94

Figure 5.21 A comparison of smoking in CPB and OPCAB CABG patients ................. 97

Figure 5.22 A comparison of smoking in CPB and OPCAB CABG patients ................. 98

Figure 5.23 Shows the incidence of family history of heart disease in CPB and OPCAB CABG patients ............................................................................. 100

Figure 5.24 A comparison of the pre-operative risk factor of diabetes mellitus in CPB and OPCAB CABG patients .............................................................. 102

Figure 5.25 A comparison of diabetes mellitus in CPB and OPCAB CABG patients with respect tho the different age group ....................................... .1 03

Figure 5.26 A comparison of the pre-operative risk factor of hypercholesterolemia in CPB and OPCAB CABG patients .......................................................... 106

Figure 5.27 A comparison of pre-operative risk factor of hypertension in CPB and OPCAB CABG patients ............................................................................. 1 08

Figure 5.28 Shows the incidence of chronic obstructive airway disease (COAD) in CPB and OPCAB CABG patients .............................................................. 110

Figure 6.1 Shows the Medtronic (Inc) Tm Octopus II Tissue Stabilizer which is utilized in OPCAB CABG ......................................................................... 112

Figure 6.2 Shows an earlier model of the tissue stabilizer used in OPCAB CABG ... 113

Figure 6.3 Showing a second type of tissue stabilizer ................................................. 114

ix

ABSTRACT IN BAHASA MALAYSIA

Ini adalah suatu kajian prospektif yang telah dikendalikan di Jabatan Pembedahan

Kardiotorasik, Hospital Penang, Pulau Pinang, melibatkan sebanyak seratus orang,

sepanjang setahun daripada bulan Januari 1999 ke Januari 2000. Lima puluh pesakit telah

menjalani pembedahan secara "off-pump" (OPCAB), yang telah dibandingkan dengan

lima puluh pesakit lain yang telah menjalani pembedahan secara "on-pump" (CPB)

dengan alat "heart-lung machine". Pesakit yang sedang menghadapi penyakit seperti sakit

buah pinggang, penyakit lumpuh, penyakit lelah, dan serangan sakit jantung bam-bam ini

telah diasingkan dan di beri rawatan secara pembedahan "off-pump (OPCAB)".

Pesakit di dalarn kumpulan ini telah mengalarni masalah yang sarna; seperti sakit jantung,

kekurangan daya upaya semasa berkerja, iaitu NYHA kelas II, ill dan N. Sebelum

menjalani pembedahan, pesakit-pesakit yang didapati mengidap sakit kencing manis,

darah tinggi, darah berlemak tinggi, merokok dan yang mempunyai penyakit yang sarna di

kalangan ahli keluarga dari kedua-dua golongan telah di teliti. Pemeriksaan yang sarna,

sehelum pembedahan, telah dilakukan di kedua-dua kumpulan pesakit. X -ray dada,

pemeriksaan ECG, Echocardiography, angiogram telah dilakukan untuk seratus pesakit

1n1. Pendarahan semasa dan selepas pembedahan, keadaan huah pinggang,

Echocardiography, ECG dan X-ray dada telah dibandingkan. Perbelanjaan diantara

OPCAB dan CPB pembedahan telah dibandingkan. Kajian telah menunjukkan bahawa

x

pesakit yang telah menjalani pembedahan jantung secara "off-pump" (OPCAB) telah

menerima faedah yang lebih baik daripada pesakit yang telah menjalani pembedahan

secara CPB. Ini menunjukkan bahawa lebih banyak lagi pembedahan akan dilakukan

secara OPCAB pada masa yang akan datang.

xi

ABSTRACT IN ENGLISH

This is a prospective study conducted at the Department of Cardiothoracic Surgery,

Penang Hospital, Penang, with a total of one hundred patients were studied over a period

of one year between January 1999 to January 2000. Fifty patients who had undergone

coronary artery bypass surgery off-pump (OPCAB) were compared with fifty patients who

had undergone coronary artery bypass surgery on the heart-lung machine (CPB). Patients

who had associated problems of renal failure, stroke, bronchial asthma and recent

myocardial infarction were included in the off-pump CABG surgery. The symptoms did

not differ in both the groups. They had experienced angina, decreased effort tolerance,

palpitations, with NYHA class IT, ill and IV. The predisposing factors of diabetes

mellitus, hypertension, hyperlipidemia, smoking, previous family history of heart disease

were studied in both these groups. The same pre-operative investigations were performed

in both groups of patients. Chest x-ray, ECG, echocardiography, femoral angiogram were

done for these one hundred patients. The intra-and post operative bleeding, pre and post

operative renal status, echocardiogram, ECG and chest X-rays were compared. The cost

effectiveness of both the OPCAB and CPB procedures were reviewed. There was,

generally, a better outcome in patients who had undergone a coronary bypass by the off­

pump (OPCAB) method as when compared to those by the CPB method. This indicates

that more cases can be done by the OPCAB method in the future.

xii

Quotations:

"Its pretty easy to go upstairs and point at the patients that have been on

pump and the patients that have been off pump"

- James C. Hart, M.D.

" The patients respond to beating heart Cabg so much better and are

extubated within 2-6 hours"

- David Perkowski,M.D.

" I saw my two post - op patients today in the unit. Both were awake ,

smiling, no bleeding, no strokes, sitting up, and delined. As they sat up,

swung their legs over the side of the bed, and begged me to listen to how

good their lungs sounded, they told me how appreciative they were. I

could not think of another time EVER that an on-pump patient had EVER

looked this good this quickly"

- Michael D, Moran M.D , Cardiologist

xiii

1 INTRODUCTION

Suitable techniques for cardiopulmonary by-pass has in the last 15 years become a

realistic standard procedure. The pump oxygenator taking over the function of the lungs,

permits operation on intracardiac defects as it provides a quiet, peaceful heart and a clear

view of the heart unobscured by blood. This procedure is not without its complications

and hence has led to the alternative method of CABG operations using off-pump

technique and minimally invasive procedures. Originally, only short periods of CPB was

feasible but now up to 6 hours are possible. Nevertheless, there are several grave

complications associated with on-pump CABG. This has lead to the resurgence of the off­

pUl!lP technique in several centers. Everyday, all over the world, approximately 2000 off­

pump operations are being performed. New fields are being explored, such as prolonged

partial bypass, to assist the action of the heart in episodes of acute heart failure. Video

assisted minimally invasive coronary operations without cardiopulmonary bypass is

indeed going to be the mainstay of management in the near future. A multicenter study

from the Benetti Foundation in Argentina was carried out by Frederico et al in 1994. The

aim of this study was to avoid the risks associated with CPB. It has led to the interest in

off-pump CABG. The incision used was through a small anterior thoracotomy. The

results showed that this method is a new promising technique that can be considered an

alternative to most angioplasty and complementary to the conventional CABG operations

[Frederico et all. The main issues in "beating heart" coronary operations are the reduced

medical costs and the avoidance of the CPB associated risks. There is a dramatic decrease

in costs due to both the decrease of disposable materials and to the reduction in total

hospital stay and intensive care stay. Frederico et al proved this in their study with zero

morbidity level for non cardiac complications and to a faster recovery post-operatively. A

few of our cases needed to be on PTCA right from the pre-operative stage of

management. Studies have shown that the outcome is favourable even for these patients if

the CABG is done off-pump. This study also emphasises the advantages of a combined

right and left small thoracotomies. 'Off pump' CABG operations have led surgeons to

learn the use of tissue stabilising techniques to stabilize the target vessels on the

epicardium. A stable myocardial function is maintained, ensuring adequate total body

perfusion. The use of Medtronic Octopus Tissue Stabilising System (OTS) allows for

improved exposure, with minimal hemodynamic compromise. It enables the surgeon to do

multi-vessel 'off-pump' (OPCAB) CABG [1. Hart et aI, 1997]. The economic outcome of

'off-pump' (OPCAB) CABG has led to the revival of this technique [Asci one et aI, 1999].

2

2 LITERA TURE REVIEW

2.1 History

• Early 20th century: Lehrbuch der Chirurgie, edited by Wullstein and Wilms,

contained a short chapter describing heart wounds.

• 1910: Alexis Carrel: performed the 1 st experimental coronary artery procedure

(shunt between the descending aorta and coronary artery using a free carotid

artery graft).

• Nevertheless, full-fledged experimental studies directed to the clinical use of

coronary artery bypass grafting did not appear until the middle of that century.

• Early experiments: In 1940, Murray developed a number of direct suture

anatomosis of systemic arteries including the internal mammary artery to the

coronary artery involving a free arterial graft.

• 1956-1965: experiments aimed at solving the immediate problems, and to

protect against jeopardizing the coronary circulation were dealt with. These

studies first used blood perfusion or autoperfusion to prevent cardiac

fibrillation. Then, the study moved on to cardiopulmonary bypass and

cardioplegia method to achieve a motionless arterial target for the suturing

process.

• 1953: V.P. Demikhov in Moscow, used LIMA to LAD graft by means of a

cannula on the beating heart of a dog.

3

• 1965: Amosova Sinyakin demonstrated suturing techniques with automatic

suturing instruments (circular vessel suturing apparatus called VCA-4 or

ASC-4) in experimental dogs.

• During the mid 1950s, Prof. Vasili I. Kolesov started work on coronary

revascularization for the treatment of heart disease (ligation of both internal

mammary arteries, in the hope of increasing collateral flow to the mediastinal

coronary arteries). This was called the Fieschi operation. Next he used the

tunneling of bleeding internal mammary arteries to the L ventricular wall.

This was called the Vineberg procedure.

• 1950s: W.Longmire was one of the pioneers of coronary bypass surgery. He

had to perform a couple of earliest internal mammary artery to coronary

anastomosis during a thrombo-endarterectomy. It later proved to be a good

operation.

• 1961: Goetz and colleagues conducted experiments with non sutured

mammary artery anastomosis Goining of the internal mammary artery to the R

coronary artery on the beating heart by means of a tantalum ring. It took 17

minutes. Catheterization was done 2 weeks after the surgery and it confirmed

the patency of the anastomoses.

• 1964: Prof. Kolesov introduced direct suturing between the internal mammary

artery and coronary arteries (done in 1964).

• 1965: Khan and colleagues showed the use of vascular staplers for

anastomosis in calf. Further work was delayed until recent renewed efforts by

Tulleken and colleagues, Nataf and colleagues and others.

4

• 1966: Prof. Kolesov used the gastroepiploic artery for the Vineberg

procedure, retrograde (1966) and bilateral internal mammary artery

anastomosis (1969) and the use of abdominal artery grafting on experimental

basis. He pioneered the use of internal mammary artery to coronary artery

anastomosis for the treatment of acute myocardial infarction and pre­

infarction conditions. He retired in 1976, his research group carried on with

his work. He died in 1992.

• 1973: Garrett et al used the saphenous vein graft to perform CABG on a

beating heart.

• Despite the widespread use of CPB bypass, Prof. Kolesov prefered to avoid

CPB or to simplify it. He advocated that for ill patients, on-pump bypass must

be avoided as it is a heavy burden for the patients heart.

• 1975: Trapp and Bisarya and Anekey reported successful cases operated by

the off-pump method.

• 1982: Benetti et al (Argentina, South America) pioneered the off-pump

CABG Lower morbidity, mortality and reduced costs were reported. This was

particularly true of high -risk patients. Similar findings were reported by

several other centres.

• *Minimally invasive direct coronary artery grafting was demonstrated by

Subrmaniam, Robinson et aI, Califiore et aI, Janssen, Vim et al.

• Mack and Nataf introduced the video-assisted cardiac surgery. They showed

how this method greatly reduced the invasiveness of the procedure and they

developed it further. Despite the initial uncertainty, the quality of the

anastomosis and the benefits of the procedure, this off-pump direct

5

visualization has received increasing acceptance. The advent of mlnl­

thoracotomy, done off-pump, on a beating heart where LIMA is anastomosed

to the LAD as originally proposed by Benetti and popularised by Califiore et

al represented an important development in coronary surgery in recent years.

This is limited to patients with single LAD lesions.

• Recent progress: Development of myocardial tissue stabilizers, flow

occluders, etc, video-assisted dissection of LIMA have been developed.

• The use of robotics have emerged to expand these teclmiques and complete

the thoracoscopic coronary surgery. The develpoment of coronary artery

surgery spans practically throughout the entire 20th century with intervals

between the breakthroughs becoming progressively shorter. However, there

was a distressing gap between the origination and the acceptance of ideas

regarding less invasive coronary artery surgery.

• Under research now: The MIDCAB operation performing LIMA to LAD

anastomosis by percutaneous angioplasty or other methods to provide

effective myocardial revascularization via a non-invasive approach and at a

lower cost.

6

2.2 ANATOMY

The pericardium which invaginates the heart is a serous sac similar to the pleura. The

outer parietal layer is invested by a strengthening fibrous coat. The pericardium encloses

the heart and the root of the great vessels. The pericardium occupies the middle

mediastinum and is attached to the sternum by the superior and inferior sternopericardial

ligaments.The arterial supply of the heart is provided by the right and left coronary

arteries. The right coronary artery arises from the aortic sinus, passes forewards to the

coronary sulcus between the pulmonary trunk and the right auricle. It then descends in the

coronary sulcus onto the diaphragmatic surface of the heart. A marginal branch passes

towards the apex along the acute margin of the heart and ramifies over the right ventricle.

Next the coronary artery passes from the left and turns onto the back of the heart and

terminates as the posterior interventricular branch. It supplies both ventricles and

anastomoses, near the apex, with the left anterior interventricular branch of the left

coronary artery [Figure 2.1]. The left coronary artery arises from the left aortic sinus. It

passes forewards to the left and divides between the pUlmonary trunk and the left auricle

into an anterior interventricular branch (LAD) and the circumflex branch. The LAD

passes towards the apex of the heart in the anterior interventricular groove. It supplies

both ventricles and the interventricular septum and anastomoses near the apex with the

posterior interventricular branch of the right coronary artery. The circumflex artery circles

toward the back of the heart in the coronary sulcus. It has a marginal branch which

follows the left margin of the heart, supplying the left ventricle. The circumflex artery

ends on the back of the left ventricle, anastomosing with the posterior interventricular

branch of the right coronary artery.

7

Diagram A 1. Left main. 2. Left anterior descending (LAD) . 3 . Diagonal. 4. Circumflex . 5. Obtuse marginal. 6. Right. 7 . Right ventricular branch. 8 . Acute marginal branch . 9 . Posterior interventricular.

Figure 2.1 Diagram A

8

A posterior artery of the left ventricle frequently swings down the back of the left

ventricle near the tennination of the circumflex, matching the distribution of the posterior

vein of the left ventricle. The branch supplying the SA node arises from the right coronary

artery in 54% of cases, distal to its conal branch. It supplies the deep aspect of the right

atrium, circles the base of the superior vena cava and ends in the SA node at the cephalic

end of the sulcus terminalis.

An intermediate artery arises from the right coronary artery nearly opposite its right

marginal branch and ascends over the right atrial surface. An anastomotic atrial branch

arises from the circumflex artery near its origin and passes towards the right, towards the

internal surface of the left atrium. It may anastomose with the terminals of the right

sinuatrial artery and is usually involved in the variant cases in which the sinuatrial artery

is a left coronary branch. The circumflex also gives rise to an intermediate atrial branch

which distributes along the left atrium above the coronary sulcus. The A V node artery

arises from the right coronary artery opposite the origin of the posterior interventricular

artery (85%) and penetrates deeply to the AV node (LAD) and posterior interventricular

arteries. Of these, those from the LAD pass two-thirds of the way into the septum, those

from the posterior interventricular arteries pass one third of the way into the septum. The

terminal anastomoses between the arteries are usually small and require enlargement for

survival in case of occlusion of any of the larger branches of the coronary arteries.

Interference with the coronary circulation results in ischemia and pain (angina pectoris) or

a varying amount of pennanent damage to the myocardium. A small area of damage

usually allows recovery by connective tissue replacement in the infracted area, but

massive damage is likely to be fatal. The coronary artery bypass surgery in which the

venous autografts are inserted to bridge the affected areas, has saved many lives. The

three most common locations of coronary occlusion, in descending order of frequency, are

proximally in the LAD, proximally in the right coronary artery and proximally in the

circumflex artery. The veins, for most part of the heart, follow the arteries [Fig 2.2].

9

DiagramB 1. Graft to right coronary artery . 2. Graft to left anterior descending coronary artery. 3. Graft to obtuse marginal branch of circumflex coronary artery.

Figure 2.2 Diagram B.

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2.3 INCIDENCE

The incidence of coronary artery disease is more in males than in women but the odds are

equal in both sexes in the post-menopausal women and men of the same age.

2.4 INDICATIONS OF OFF·PUMP CABG

The following are the indications for performing an off-pump CABG:

• Coronary artery disease

• Severely calcified aorta, especially the ascending aorta

• Renal disease, renal insufficiency

• Pulmonary disease, emphysema

• Previous stroke, cerebrovascular accident

• Diffuse peripheral vascular disease

• elderly patients

• Poor ventricular function

• Re-operations

• Jehovah's witness religious group (refuse blood transfusion based on religious

beliefs)

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2.5 CONTRAINDICATIONS OF OFF-PUMP CABG

There are several contraindications to off-pump CABG and these are as follows:

• Deep intramyocardial vessels

• Small distal targets

• Hemodynamic instability due to cardiac manipulation or ischaemic precondition

• Acute myocardial infarction with cardiogenic shock

2.6 ADVERSE EFFECTS OF CPB CABG

On-pump CABG (CPB), has several adverse effects affecting mUltiple organs. The

pathophysiology of this "pump syndrome" is illustrated in Fig. 2.3 below.

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CPB

~ (controlled shock)

~ Inflammatory reaction

~ Activation ofC', Kallikrein, kinnins, Tumor necrosis

~ factor, alpha systems

~ Alters coagulation functions

~ vasoplegic syndrome

~ Increased capill~ permeability

~ Sequestration of neutrophils

~ MICROEMBOLI

~ (to brain, kidneys, lungs, liver etc)

Figure 2.3 Pathophysiology of pump syndrome.

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2.6.1 Renal Failure

After CPB CABG, renal failure is usually due to acute tubular necrosis. This is due to

renal vasoconstriction. The exact local mechanism is not understood as yet. It is believed

to be due to a physiological shunt which diverts blood from the artery to the vein, thereby

depriving the renal tissue of its blood supply. Acute tubular necrosis can occur in the

event of a brief hypotensive episode intraoperatively. Other mechanisms may be involved

including the intravascular (glomerular) thrombosis, tubular obstruction and the renin­

angiotensin system. Incompatible blood transfusion damage in the extracorporeal

apparatus, long perfusions, septicaemia, hypoxia and acidosis have also been implicated

in the etiology of renal failure in CPB CABG. The plasma haemoglobin released by red

cell trauma after CPB operations can pass through the kidney and appear in the urine

without any sign of renal disturbance. Renal embolism with clot, air or airfoam is a rare

cause of renal failure. The acute tubular necrosis usually causes oliguria (less than 400

ml/day). Anuria is rare in acute tubular necrosis and if present, it suggests the presence of

bilateral renal embolism or bladder neck obstruction due to an associated prostatic

hyperplasia. Renal failure can occur without oliguria, as seen in non-oliguric renal failure

in valve replacement done on CPB.

2.6.2 Cerebral Damage

Cerebral damage after CPB CABG is due to embolism and cerebral ischemia. eNS

complications due to cerebral embolisation occurs at the time of decannulation, aortic

clamping and declamping. A common complication is the development of a stroke.

14

Intracranial hemorrhage, hypothermia, metabolic derrangements can also contribute to

cerebral disturbances after CPB CABG. It is manifested as psychiatric disorder or present

with post-operative neurological signs which may be so severe as to result in coma and

death. Embolism may be due to air trapped within the left side of the heart after open

heart surgery. The nitrogen content of air is absorbed slowly. Thus air embolism is more

dangerous than oxygen or carbon dioxide embolism. This can occur if frothing occurs in

the oxygenator or if cold blood comes into contact with warm tissues. De-airing of the

grafts and the chambers of the heart is very important at the end of the anastomosis of the

grafts.

The presence of a preoperative mitral valve lesion will predispose the patient to the risk of

developing a cerebral thrombo-embolism from the left atrium and appendage. Left

ventricular aneurysms often contain clots which can embolise. Thrombosis along the left

atrial suture lines and prosthetic valves is another cause of post-operative thrombo­

embolism. Fat embolism can occur due to the release of fat globules from the pericardium

after median sternotomy incisions or due to trauma to mediastinal fat by suction injury of

the coronary aspirators into the extracorporeal equipment. Fibrin embolism has been

shown to be common with certain oxygenators resulting in diffuse brain damage.

Occasionally, foreign materials such as sutures, patches can reach the brain as emboli.

Cerebral ischemia can cause severe cerebral damage. The ischemic event could manifest

are noted in hypoglycemia, diabetic coma, gross electrolyte imbalance or a very low pH.

Drugs added due to a very low intraoperative cardiac output, a low flow from the pump

oxygenator. This can also result from using pure oxygen in the pump oxygenator leading

to a low arterial carbon dioxide tension. It is also seen if the patient is hyperventilated

intraopeartively. Cerebral anoxia develops faulty oxygenation techniques by the

15

anaesthetist, with large left to right shunts, pulmonary complications and ventilatory

inadequacies result in cerebral damage. Other causes of cerebral damage in CPB CABG is

due to raised intracranial pressures from subdural hemorrhage, hypertensive crisis,

cerebral dehydration with hypertonic solutions and with obstruction to one jugular vein. In

this instance, the venous cross communications cannot be relied upon to overcome the

resultant raised intracranial pressure. Profound hypothermia can cause cerebral damage

due to ischemia rather than from direct damage from hypothermia. Cerebral symptoms

may be seen due to metabolic disturbances but it is rare. Mental and neurological changes

can occur due to the pump oxygenator. The psychological disturbances are of various

degrees ranging from slight disorientation to frank psychoses. Treatment postoperatively

at the CICU can bring about a fear of impending death with its unsureal atmosphere. They

can have a lack of sleep, anxiety fragmented speech and use the wrong words while

attempting to talk. Hallucinations occur when the cardiac output improves. Patients can

also experience disorders of conciousness, unequal pupils, hemiparesis, convulsions,

hyperpyrexia, hyperreflexia and extensor responses. Slowing pulse, spreading hemi­

paresis or hemi-sensory loss could point to the evolvement of cerebral oedema. An

associated papilloedema will definitely indicate a CT scan of the brain with further

neurological assessment. The pathology of cerebral damage is due to changes brought

about by ischemia and anoxia. It consists of diffuse neuronal loss in the cerebral cortex

with less changes in the medulla. Cerebral odema mayor may not be present. Clot and

calcium embolism may cause cerebral infarcts. Diffuse local areas of cerebral damage

may be seen due to air or fibrin embolism.

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2.6.3 Hepatic Failure

Jaundice may occur after cardiac surgery for vanous reasons. Older patients with

pulmonary hypertension and myocardial insufficiency are likely to develop hepatic

failure. Hepatic function could be depressed during and after the surgery. Anaesthesia,

especially halothane, hypothermia, a low flow with poor tissue perfusion from the pump

oxygenator and raised plasma hemoglobin aggravate these effects. The kidneys will also

suffer from a reduced renal blood flow. Thus renal and hepatic failure can occur

simultaneously.

Post-operatively a low cardiac output with a high venous pressure may worsen hepatic

damage. Drugs and sepsis also playa role. Transfusion viral hepatitis may occur after

cardiac surgery with an incubation period of 14-100 days. Cytomegalovirus hepatitis may

also occur.

2.6.4 Hematological Disorders

Blood damage in extracorporeal circulation is of a complex nature and causes accelerated

destruction of red blood cells in the post-perfusion period. Hemoglobin levels can fall to

as low as 3-5 gmJdL.Subacute bacterial endocarditis or protracted low grade infection

may cause anemia. Gastrointestinal bleeding may occur from anticoagulant therapy and

result in anemia. Post operatively, despite good drainage variable amount of blood lies in

the chest cavity. Post operative chest X-ray will show a widening of the mediastinum.

Intravascular hemolysis will occur due to artificial materials used in CPB. A patient with

17

sickle cell disorder will do well with off-pump CABG with a preoperative spleenectomy

before the CABG. The amount of blood to be transfused (packed cells) is calculated with

the following formula:

Vol. of blood = 3.5 X (Desired level of Hb - Actual Hb level) X body weight

Failure of the hemostatic mechanism after CPB is a major problem requiring chest

reopening. The circulating heparin may not have been neutralised well with protamine.

Recrudescence of heparin activity after effective neutralization can occur. It is called

heparin rebound phenomenon. The cause is unknown. Heparinised blood returns into

circulation from stagnant peripheral vessels or to fibrinolytic degradation of the heparin

protamine complex. An increase thrombin time due to a decrease in levels, allows heparin

to reappear. Excessive dose of protamine prolongs coagulation, but fortunately this rare.

Qualitative platelet defects are seen when platelets are exposed to the CPB circuit with

alpha- granule release. Alteration of platelet membrane receptors occurs. The degree of

platelet dysfunction co-relates with the duration of CPB and the degree of hypothermia

after bypass. Hemodilution on CPB and consumption in extracorporeal circuit will

decrease platelet count by 30%-50%. The thrombocytopenia worsens as the CPB time

increases. These are the quantitative platelet defects. A transient fall in the platelet count

to 30% is noted on giving protamine. CPB lowers most of the coagulation factors by 50%,

especially factor V by 80%. Hemodilution is more pronounced if patients have a small

blood volume. The use of intra-operative cell-savers will eliminate clotting factors.

Fibrinolysis occurs due to activation of the plasminogen during CPB.

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2.6.5 Other Factors

CPB predisposes to the development of paradoxical septal wall motions of the cardiac

musculature. There is an increased rate of morbidity and mortality .It involves increased

utilization of resources. There is an increased incidence of reopening of the chest for

blood loss and bleeding. The post-operative stay is prolonged as when compared to the

off-pump CABG. Peri-operative incidence of myocardial infarct is more with CPB.

2.7 INCIDENCE OF MAJOR POST-OPERATIVE COMPLICATIONS WITH AND WITHOUT CPB IN A STUDY DONE BY ENIO BUFFALO IN 1995.

The above study conducted by Enio Buffalo et al has established that complications of

CABG with CPB is more than with off-pump CABG (Table 2.1). Patients benefit from an

off-pump CABG. A similar study was done by the cardiothoracic teams of three hospitals

in the USA i.e. Allegheny University HospitaV Medical College of Pennsylvania,

Harrisburg Hospital and Park Nicolet CliniclHealth System Minnesota. They had similar

results showing that off-pump CABG had many advantages over the CPB CABG.

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Table 2.1 Incidence of major post-operative complications with and without CPB in a study done by Enio Buffalo in 1995.

Complication With CPB WithoutCPB (509 cases) (200 cases)

Perioperative MI 18 (3.5%) 2 (1%)

Arrythmias 25 (5.6%) 5 (2.5%)

eVA 3 (0.6%) 0(0%)

Acute renal failure 8 (5.1%) 0(0%)

GIT bleed 7 (1.4%) 2 (1%)

Excessive bleeding 16 (3.0%) 3 (1.5%)

Prolonged intubation 40 (7.8%) 9 (4.5%)

Vasoplegic syndrome 10 (2.1 %) 2 (1%)

Total 127 (24.90/0) 23 (11.50/0)

2.8 COST - EFFECTIVENESS

Costs are reduced when CABG is performed by the off-pump method. CPB patients

require a prolonged CleU stay, and general ward stay post operatively due to all the

above mentioned complications. With CPB, time spent in the hospital is reduced, with

fewer post operative complications. Thus more number of patients can be treated by the

off-pump technique using the available resources. It also decreases the waiting list for

coronary surgery. The estimated cost of coronary artery bypass operation at the

Cardiothoracic Surgery Unit at Penang Hospital is as follows (Table 2.2):

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Table 2.2 Showing the cost of OPCAB and CPB CABG at Penang Hospital, Penang.

Type of operation Off-pump (OPCAB) CPB

Cost (in ringgit Malaysian) RM3,200.00 RM 4,864.00

The cost of utilizing the extracorporeal equipment alone being RM2064.00.

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3 OBJECTIVE OF STUDY

1. The primary aim of this study is to assess the usefulness of the off-pump coronary

artery bypass surgery for elective patients with coronary artery disease.

2. The secondary aim is to assess the following parameters in these patients:

a) Morbidity

1. Infection

11. Ventilation time

iii. Cost effectiveness

b) Mortality

c) Peri-operative infarcts based on ECG findings

d) Clinical outcome

1. Renal status pre and post operatively (assessed with serum creatinine)

11. Duration of CICU stay ( assessed with time of extubation)

iii. Treatment with inotroph

IV. Gross neurological status

v. Post operative bleeding

VI. Post operative blood transfusion

V11. Post operative wound infection of the chest and the leg.

VIlt. Post operative lung complications

IX. Angina

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x. Pericardia! effusion

Xl. Ejection fraction

xu. Pre-operative risk factors

xiii. Incidence of wound infection

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4 MATERIALS AND METHOD

4.1 GENERAL DESCRIPTIONS

Suitable techniques for cardiopulmonary bypass has in the last fifteen years become a

realistic standard procedure. The pump oxygenator takes over the functions of the heart

and the lungs, thus pennitting a quiet, non-beating heart with a clear view unobscured by

blood. Originally only short periods of bypass were feasible. Now periods of up to 6 hours

are possible. Nevertheless, there are several grave complications associated with the use

of the CPB machine. This has led to the use of the off-pump method of CBG using the

Octopus IT tissue stabilizer (by Medtronics Inc.) in several centres around the world.

A total of 100 patients were involved in this prospective study. Fifty of them were

operated using the CPB method and another fifty patients were operated by the off-pump

method. Patients were selected randomly into the two groups of study. Those with pre­

operative risk factors of arrythmias were excluded from this study. Both groups had

patients with various other medical problems such as diabetes mellitus, hypertension,

gastrointestinal bleeding, gastritis, ischaemic heart disease, chronic obstructive airway

disease, renal disease, and others. They were all assessed pre operatively by the same

parameters. Baseline blood investigation of full blood count, blood urea and electrolytes,

serum creatinine, coagulation profile were done. Routinely, blood was grouped and cross

matched prior to surgery. A pre-operative angiogram was perfonned. All the 100 patients

had under gone investigations such as ECG, echocardiography, chest x-ray preoperatively.

They were all grouped together and given a "pump talk" i.e. a briefing about the

24