CARDIAC PHYSIOLOGY& ANAESTHETIC CONSIDERATIONS

By- Dr. Armaan Singh

Heart

Hollow Located within the mediastinum of the thoraxDistal end extends downward to the left forming apex at the

fifth intercostal space.

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HEART STRUCTURE ANATOMICALLY ONE ORGAN FUNCTIONALLY DIVIDE INTO RT. & LT PUMPSFOUR VALVES WITH UNIDIRECTIONAL FLOW

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Pulmonaryand SystemicBloodflow

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The heart consists of three different layers

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Coronary supplyInferior Rt coronary

Anteroseptal Lt ant descening

Anteroapical Lt ant desceding( distal)

Anterolateral Circumflex

Posterior Rt coronary artery

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CARDIAC ACTION POTENTIALl

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ME

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TIME

PHASE0 = Rapid Depolarization (inward Na+ current) 1 = Overshoot2 = Plateau (inward Ca++ current)

3 = Repolarization (outward K+ current)4 = Resting Potential

Mechanical Response

PACEMAKERS (in order of their inherent rhythm)

• Sino-atrial (SA) node• Atrio-ventricular (AV) node• Bundle of His• Bundle branches• Purkinje fibers

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AtrioVentricular Node

Sinoatrial Node

Atrioventricular Bundle

Purkinje Fibers

Heart Conduction System

INITIATION & CONDUCTION OF THE CARDIAC IMPULSE

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Heart Actions• Atrial systole is when the atria contract while the ventricles

relax which is called ventricular diastole.• Thus systolic and diastolic blood pressure.• This series of contraction and relaxation is called a cardiac

cycle.

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LATE DIASTOLE

ATRIALSYSTOLE

ISOMETRIC VENTRICULARCONTRACTION

VENTRICULAR EJECTION

ISOMETRICVENTRICULARRELAXATION

EVENTS IN CARDIAC CYCLE

DIASTOLE

CARDIAC CYCLE

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Atr

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Syst

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Mitral Closes

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Aortic opens

S1

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Red

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Aorticcloses

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Mitralopens

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CARDIAC OUTPUT• DEFIND AS VOLUME OF BLOOD PUMPED BY HEART/MIN• CO = SV X HR • SV IS VOLUME PUMPED PER CONTRACTION• average cardiac output would be 5L.min-1 for a human male

and 4.5L.min-1 for a female.

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CARDIAC OUTPUT AND THE FICK PRINCIPLE

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BODY O2 CONSUMPTION

250mlO2/min

PaO2

190mlO2/l blood

PvO2

140mlO2/l blood

PULMONARYARTERY

PULMONARYVEIN

CARDIAC OUTPUT=O2 CONSUMPTION (ml/min)

PaO2- PvO2

Pulmonary capillaries

Lungs

Pulse

• Pressure wave move along the artery wall which are pliable

• usually measured in beats per minute • normal range from 60 to 100 beats per minute

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Factors Influencing the Pulse• Stroke volume

• Rate of ejection

• Distensibility of peripheral arteries

• Peripheral resistance

• Pulse rate

• Pulse pressure

• Size of the vessel

• Distance from the heart

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Pulsus Parvus

• The pressure is diminished, and the pulse feels weak and small, seen in - restrictive pericardial disease, hypovolemia, mitral stenosis

• Pulsus Parvus et Tardus (weak and delayed): →Aortic Stenosis

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Bisferiens Pulse

• Increased arterial pulse with a double systolic peak. • Causes : AR

• HCM

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Bigeminal Pulse

• characterized by groups of two heartbeats close together followed by a longer pause. The second pulse is weaker than the first

• Causes: severe HF, hypovolemic shock, cardiac tamponade)

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Pulsus Alternans

arterial pulse waveform showing alternating strong and weak beats

• Causes:• Left ventricular failure • severe AR

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Pulsus Paradoxus

• Pressure drop > 20 mmHg during inspiration.• Normally, systolic arterial pressure falls 8-12 mmHg during

inspiration.• Causes:• Cardiac Tamponade• COPD, hypovolemic shock

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BLOOD PRESSURE• DEFINE AS PRESSURE OF BLOOD AGAINST THE WALL OF MAIN

ARTRIES• HIGHEST DURING SYSTOLE N LOWEST DURING DIASTOLE• MEASURED BY SPHYGMOMANOMETER @ BRACHIAL ARTERY

OF ARM

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Blood Pressure (BP): Measurements

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Figure 15-7: Measurement of arterial blood pressure

CLASSIFICATION

Category Systolic Diastolic

hypotension <90 <60

normal 90 – 119 60 - 79

prehypertesion

120 - 139 80 - 89

stage1ht 140 - 159 90 - 99

stage2ht >160 >100By- Dr. Armaan Singh

Pulse and Mean Arterial Pressures

• Pulse pressure = Systolic –Diastolic• Mean arterial pressure (MAP) = Diastolic +

1/3 pulse pressure

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EJECTION FRACTION• Ejection fraction (Ef) is the fraction of the end-diastolic

volume that is ejected with each beat• it is stroke volume (SV) divided by end-diastolic volume (EDV):

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EJECTION FRACTION• In a healthy man, the SV is approximately 70 ml and the left

ventricular EDV is 120 ml, giving an ejection fraction of 70/120, or 0.58 (58%).

• Healthy individuals typically have ejection fractions between 50% and 65%

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METHODS OF EF MEASUREMENT • CARDIAC CATHETRISATION

• RADIONUCLEOTIDE STUDIES

• ANGIOCARDIOGRAPHY

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CARDIAC INDEX

• Cardiac index (CI) is a vasodynamic parameter that relates the cardiac output to body surface area

• unit of measurement is (l/min/m2) • normal range of cardiac index is 2.6 - 4.2 L/min per square meter.

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ANAESTHETIC CONSIDERATION• Halothaane isoflurane and enflurane depress SA node automaticity.

• IV induction agent have limited effect on usual clinical doses.• Opioids can depress cardiac conduction.• LA associated with systemic toxicity.

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GOALS OF ANAESTHESIA IN CVS DISEASES• PREMEDICATE BY BZP’S• BLUNT RESPONSE BY LARYGOSCOPY N INTUBATION• AVOID TACHYCARDIA• AVOID HYPOCAPNIA

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THANK YOU

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FOR MORE MEDICAL PRESENTATIONS VISITSlideshare/Dr. Armaan Singh