CARDIOVASCULAR

SYSTEM

CONTENTS

• INTRODUCTION

• LAYERS OF THE HEART WALL

• PROPERTIES OF CARDIAC MUSCLE

• CARDIAC CYCLE

• HEART SOUNDS AND MURMURS

• ECG

• APPLIED ASPECTS

• RELATED ARTICLES

• CONCLUSION

• REFERENCES

INTRODUCTION

• The heart is a chambered muscular organ that pumps blood received from the veins into the arteries, thereby maintaining the flow of blood through the entire circulatory system.

• Somewhat pyramid shaped and lies between two lungs in the mediastinum .

LAYERS OF THE HEART WALL

PERICARDIUM

MYOCARDIUM

• Formed by cardiac muscles.

• Mainly three :

• Muscles which form contractile unit of heart

• Those which form the pacemaker

• Those which form the conductive system

THE MUSCLE FIBRES FORMING

CONTRACTILE UNIT

• Striated

• Similar to skeletal muscles but involuntary

• Bound by sarcolemma

• Centrally placed nucleus

• Myofibrils embedded in sarcoplasm

• Sarcomere contains all muscle proteins

INTERCALATED DISC

SYNCYTIUM

• All muscles act like a single unit

• Gap junctions – permeable to ions

• Facilitates rapid conduction of electrical activity

THE MUSCLE FIBERS FORMING PACE

MAKER

• Muscle fibers modified

• Specialized structure with lesser striations

• Generates impulses for heart beat

• Formed by pacemaker cells

• SA node is situated in posterior wall of Right atrium near opening of Superior vena cava.

THE MUSCLE FIBRES FORMING

CONDUCTIVE SYSTEM

• Modified cardiac muscle fibres

• Specialized cells - conduct impulses from SA node to ventricles

• Junctional tissues

• Atria – directly

• Vetricles- various tissues

ELECTRICAL SYSTEM OF THE HEART

ENDOCARDIUM

• Inner most layer

• Thin,smooth, glistening membrane

• Single layer of endothelial cells

• Continues as endothelium of blood vessels

SEPTAE OF THE HEART

VALVES OF THE HEART

Pulmonarysemilunar valve

Aorticsemilunar valve

Left AV(bicuspid)valve

Right AV(tricuspid)valve

Chordaitendineae

Papillarymuscle

ARTERIAL SUPPLY

• The arterial supply of the heart is provided by the right and leftcoronary arteries, which arise from the ascending aorta immediately above the aortic valve.

PROPERTIES OF CARIAC MUSCLES

• EXCITABILITY

• RHYTHMICITY

• CONDUCTIVITY

• CONTRACTILITY

EXCITABILITY

• Ability of a tissue to give response to a stimulus .

• Muscles respond by development of an action potential.

ELECTRIC POTENTIAL IN CARDIAC

MUSCLE

• RAPID DEPOLARIZATION

• INITIAL RAPID REPOLARIZATION

• PLATEAU PHASE

• SLOW REPOLARIZATION

Ionic basis of Action potential

SPREAD OF ACTION POTENTIAL

• Spreads very rapidly

• Gap junctions- allows free movement of ions

• Cardiac muscles act like a syncytium

RHYTHMICITY

• Ability of a tissue to produce its own impulses regularly.

• Autorythmicity / Self excitation

• SA node – discharge impulses rapidly – spreads to other parts of the heart

PACEMAKER

• Part of the heart from which impulses for heart beat are produced

• SA node – modified cardiac muscle

• Superior part of lateral wall of right atrium.

• Below opening of Superior Venacava.

• Do not have contractile elements

• Continuous with fibers of atria

• Maximum number of impulses

CONDUCTIVITY

• Three groups of fibres

• Anterior internodal Bachman

• Middle internodal Wenkebach

• Posterior internodal Thorel

• All these converge towards AV node

CONTRACTILITY

• Ability of a tissue to shorten in length after receiving a stimulus.

• All or none law

• Staircase phenomenon

• Summation of subliminal stimuli

• Refractory period

• Stimulus applied- whatever may be the strength-maximum response/ no response.

• Subthreshold stimuli- no response.

• Threshold stimulus- weakest stimulus that evokes a response

All or none law

Staircase phenomenon

Summation of subliminal stimuli

• Stimulus with subliminal strength – no response

• Repeated subliminal stimuli- contraction-summation.

REFRACTORY PERIOD

• Period when muscles do not show any response to a stimulus

• Cardiac muscles have long refractory period

• Absolute – 0.27 s- throughout contraction

• Relative – 0.26 s- first half of relaxation

CARDIAC CYCLE

• Defined as the succession of coordinated activities which take place in every heart beat.

• 2 major steps – systole – 0.27 s

• diastole – 0.53 s

• Duration- 0.8 s when heart rate is 72/min

SYSTOLE

• Isometric contraction – 0.05s

• Ejection period – 0.22s

DIASTOLE

• Protodiastole – 0.04s

• Isometric relaxation – 0.08s

• Rapid filling – 0.11s

• Slow filling – 0.19s

• Atrial systole – 0.11s

ATRIAL SYSTOLE

• Also called presystole

• End of ventricular diastole

• 10% blood forced into ventricles from atria.

• 0.11 sec

ISOMETRIC CONTRACTION

• Lasts for 0.05s

• Starts immediately after atrial systole

• AV valves close – increased pressure in ventricles

• No change in volume or length of muscle fibres-only tension

EJECTION PERIOD

• Due to opening of semilunar valves

• 2 stages

• Rapid ejection

• Slow ejection

• 0.22 sec

PROTODIASTOLE

• Pressure in ventricles drop

• Pressure in aorta and pulmonary artery increase

• Semilunar valves close again

• Indicates end of systole

• 0.04 sec

ISOMETRIC RELAXATION

• Once again all valves are closed

• Both ventricles relax – with no change in volume or length of muscle

• Fall in intraventricular pressure

• When pressure goes less than atria – AV valves open

• Leading to filling of ventricles

• 0.08 sec

RAPID FILLING

• Av valves open

• Blood accumulates in atria – atrial diastole

• Sudden rush into ventricles – 70% of filling

• 0.11 sec

SLOW FILLING/DIASTASIS

• Ventricular filling slows down

• 20 % filling takes place

• 0.19 sec

atrial systole/last rapid filling phase and the cycle repeats, 10% filling.

HEART SOUNDS

• Four sounds

• Fisrt and second – more prominent – resemble ‘LUBB DUBB’ respectively

• Heard – stethoscope

• 3rd- mild – microphone – children and athelets

• 4th – inaudible – graphic registration-phonocardiogram

• First sound – simultaneous closure of both AV valves

• Second – closure of semilunar valves

• Third – rapid filling

• Fourth – atrial systole

CARDIAC MURMURS

• Abnormal heart sounds or bruits

• Turbulence in blood flow

• Ventricular diseases / abnormal conditions

CLASSIFICATION

CARDIAC MURMURS

SYSTOLIC MURMURS DIASTOLIC MURMURS CONTINUOUS MURMURS

INCOMPETENT AV STENOSIS OF AV VALVES PDAVALVES

INCOMPETENCE OF S VSTENOSIS OF S V

ELECTROCARDIOGRAM

• Electrocardiography – technique

• Electrocardiograph – instrument

• Electrocardiogram – graphical registration

• Introduced in 1901 – Dutch physiologist –Willem Einthoven

APPLIED ASPECTS

• CONGENITAL HEART DISEASES

• Acyanotic

• Cyanotic

• ACQUIRED HEART DISEASES

• Rheumatic fever

• Infective endocarditis

CONGENITAL HEART DISEASE

• Incidence – 9 in 1000 births

• Maybe abberant embryonic development

• Maternal rubella / chronic maternal alcohol abuse

ACYANOTIC CONGENITAL HEART

DISEASES• Minimal or no cyanosis

• Left to right shunting of blood

• Ventricular septal defect

• Atrial septal defect

CYANOTIC

• Right to left shunting

• Cyanosis even during minor exertion

• Tetralogy of Fallot

• Pulmonary stenosis

• Tricuspid atresia

• Transposition of great vessels

ATRIAL SEPTAL DEFECT

• Most common

• More frequent in females

• Dyspnea ,chest infections

• Fixed splitting of second heart sound

• Chest radiograph – enlarged heart

• Echo shows clear defect with ventricular dilatation and hypertrophy and PA dilatation

MANAGEMENT

• Closure – cardiac catheterization

• Implantable closure devices

VENTRICULAR SEPTAL DEFECT

• Congenital VSD – incomplete separation of ventricles

• Left to right shunting

• 1 in 500 live births

• Murmur heard at the left sternal edge.

• Occurs as acute failure in infants

• Chest x ray and ECG – ventricular hypertrophy

Mary S. Minette, MD; David J. Sahn, MD, Ventricular Septal Defects

Circulation. 2006;114:2190-2197.)

MANAGEMENT

• Small VSD – no treatment – prophylaxis is must

• Large defects – initially treated with medications – digoxin ,diuretics

• Persistent failure – surgical repair

PATENT DUCTUS ARTERIOSUS

• Ductus arteriosus – present in fetal life

• Normally closes after birth

• Sometimes may persist – defect

• Since pressure in aorta greater than PA –continuous AV shunt.

• Small shunts – no symptoms

• Large shunts- growth retardation

• Dyspnea eventually cardiac failure

• Machinery murmur- second left intercostalspace below clavicle

• Accompanied by thrill

• ECG usually normal

MANAGEMENT

• Cardiac catheterization

• May be done in infancy

• Smaller shunts – delayed to childhood

• Prostaglandin synthetase inhibitors –Indomethacin ,Ibuprofen – 1st week – induce closure

PERSISTENT DUCTUS WITH REVERSE

SHUNTING• Pulmonary Artery pressure rises to exceed aortic

pressure

• Shunt may reverse

• Central cyanosis – Eisenmenger’s Syndrome

• ECG – ventricular hypertrophy

TETRALOGY OF FALLOT

• Pulmonary stenosis

• Overiding aorta

• VSD

• Right ventricular hypertrophy

• Elevated right ventricular pressure

• Right to left shunting

“ FALLOT SPELLS ”

• Cyanosis

• Syncope

• Brain injury

• Death

MANAGEMENT

• Definitive management – total correction of defect

• Surgical relief of pulmonary stenosis

• Closure of VSD

AQUIRED HEART DISEASES

• INFECTIVE ENDOCARDITIS

• RHEUMATIC FEVER

INFECTIVE ENDOCARDITIS

CAUSATIVE ORGANISMS

• Staphylococcus

• Group A streptococcus

• pnemonococcus

• 2 forms – acute , subacute

• Subacute – viridans stretococci

• Vegetations – fibrous exudate and microorganisms

CLINICAL FEATURES

• Low irregular fever

• Sweating

• Malaise

• Arthralgia

• Weight loss

• Anorexia

• Murmurs

• Painful fingers and toes ,skin lesions

LABORATORY FINDINGS

• Leukocytosis

• Neutrophilia

• Normocytic normochromic anemia

• ESR is rapid

PROPHYLAXIS

SINGLE DOSE 30-60mins BEFORE PROCEDURE

ORAL AMOXICILLIN

ADULTS

2g

CHILDREN

50mg/kg

UNABLE TO TAKE ORALLY

AMPICILLIN ORCEFAZOLIN ORCEFTRIAXONE

2g IM/IV

1g IM/IV

50mg/kg

50mg/kg

ALLERGIC TO PENICILLIN ORAL

CEPHALEXIN ORCLINDAMYCIN ORAZITHROMYCIN/CLARITHROMYCIN

2g600mg500mg

50mg/kg20mg/kg15mg/kg

UNABLE TO TAKE ORALLY –ALLERGIC TO PENICILLIN

CEFAZOLIN ORCEFTRIAXONE OR CLINDAMYCIN

1g IM/IV

600mg IM/IV

50mg/kg

20mg/kg

•Cardiac conditions associated with highest risk of adverse outcome from endocarditis for which prophylaxis with dental procedure is reasonable

• Prosthetic cardiac valve or prosthetic material used for cardiac valve repair

• Previous infective endocarditis

• Congenital heart disease

• Unrepaired cyanotic CHD

Crieghton M, Dental care for the pediatric cardiac patient .Journal of Canadian Dental Association 1992 March;58(3):201-2

Prophylaxis recommended:

• Management of gingival tissues or periapicalregions of teeth

• Perforations of oral mucosa(extractions)

Not recommended

• Anesthetic injections through noninfectedtissues

• Taking dental radiographs• Placement of orthodontic or prosthodontic

appliances• Shedding of decidious teeth• Bleeding following trauma to the lips and oral

mucosa• Arnold S. Bayer et al . Diagnosis and Management of Infective

Endocarditis and Its Complications;Circulation. 1998;98:2936-2948

RHEUMATIC HEART DISEASES

• children of age group 5-15 years,

• inflammation of heart

• Streptococcus bacteria- sore throat (strep throat) and fever called rheumatic fever

• shortness of breath and chest pain with high fever.

Management

• valvuloplasty or have a valve replacement

• long term penicillin prophylaxis

Dental care:

• Special attention to oral health may be recommended for people with heart disease and heart conditions.

• Wait a minimum of six months after cardiac surgery or heart attack before undergoing any dental treatments.

CARDIAC SURGERY PATIENTS

• Complete dental evaluation prior

• Preventive dental programme – prevent IE

• Dental radiographs

• Consultation with cardiologist – to plan the treatment

• Treatment – within 3-4weeks of surgery

CONCLUSION

• The heart is the life-giving, ever-beating muscle

• The primary function of the heart is to pump blood through the arteries, capillaries, and veins.

• Heart defects present at birth are called congenital heart defects. Slightly less than 1% of all newborn infants have congenital heart disease.

REFERENCES

• N.A Boon , Cardiovascular System , Davidson’s Principles and Practise of Medicine.19th

edition.Elsevier 2002;357-483

• Ralph E.McDonald. Dental problems in children with disabilities.Dentistry for children and adolescents.9th edition.Elsevier 2010

• K.Sembulingam .Cardiovascular System.Essentialsof Medical Physiology.2nd edition.Jaypee 2002

• Mary S. Minette, MD; David J. Sahn, MD, Ventricular Septal Defects; Circulation. 2006;114:2190-2197

• Crieghton M, Dental care for the pediatric cardiac patient .Journal of Canadian Dental Association 1992 March;58(3):201-2

• Arnold S. Bayer et al . Diagnosis and Management of Infective Endocarditis and Its Complications;Circulation. 1998;98:2936-2948