Cardiovascular 2:CARDIAC CYCLE

Prof.dr.Hardi Darmawan, MPH&TM, FRSTM 1

The Cardiac Cycle Electrical events of the heart (measured by ECG) Mechanical Events (contraction & relaxation of the heart) Refers to period from the start of one heart beat next heart beat. 2

Myocardial Action Potential

Atrial Systole Isovolumetric ventricular contraction Rapid ventricular ejection Reduced ventricular ejection Isovolumetric ventricular relaxation Rapid ventricular filling 5 The Steps of the cardiac cycle

1. Ventricular filling 2. Isovolumetric contraction 3. Ventricular ejection 4. Isovolumetric relaxation 5. Mitral valve opens 6. Mitral valve closes 7. Aortic valve opens 8. Aortic valve closes 6

Cardiac Cycle Phases: 1.Isovolumetric contraction- period between mitral valve closure and aortic valve opening; period of highest oxygen consumption 2.Systolic ejection-period between aortic valve opening and closing 3.Isovolumetric relaxation-period between aortic valve closing and mitral valve opening 4.Rapid filling-period just after mitral valve opening 5.Slow filling-period just before mitral valve closure. 7

Cardiac Cycle Sounds: S1 - mitral and tricuspid valve closure. S2 - aortic and pulmonary valve closure. S3 - at end of rapid ventricular filling. S4 - high atrial pressure/ stiff ventricle. S3 is associated with dilated CHF. S4 (atrial kick) is associated with a hypertrophic ventricle. 8

Cardiac Cycle a wave - atrial contraction c wave - RV contraction (tricuspid valve bulging into atrium) v wave - increased atrial pressure due to filling against closed tricuspid valve. Jugular venous distention is seen in right heart failure. 9

CARDIAC CYCLE 10

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An example of a normal jugular venous pulse tracing 1

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The major features of a left ventricular pressure- volume loop 14

SUMMARY OF THE CARDIAC CYCLE Step Step Mechanism Important Points No. Ventricular Contraction (Systole) AV Valve 1 Ventricular contraction causes Normal aortic systolic Closure increased ventricular pressure: 120 mm Hg. pressure. Normal pulmonary artery systolic pressure: 15-18 mm 2 When ventricular pressure Hg. exceeds atrial pressure, AV valves close. Iso- 3 Closed AV valves isolate Arterial diastolic pressure is volumetric ventricles from atria the lowest arterial pressure. Contraction It occurs just before onset of 4 Ventricular volume stays ventricular ejection. constant while ventricular pressure rises. 15

SUMMARY OF THE CARDIAC CYCLE Step Step No. Mechanism Important Points Ventricular Contraction (Systole) Ventricular 5 When ventricular pressure Arterial systolic pressure is Ejection exceeds arterial pressure the peak arterial pressure. semilunar valves open. It occurs at the end of rapid ejection. 6 Ejection starts, and arterial volume and pressure begin to Right ventricular ejection increase. occurs before left because pressure in pulmonary artery 7 Rapid ejection: two thirds of is low compared to that in stroke volume ejected during aorta. first third of systole (ventricular pressure > aortic pressure). 8 Reduced ejection: one third of stroke volume ejected during last two thirds of systole (ventricular pressure < aortic pressure). 9 Ventricles relax. 16

SUMMARY OF THE CARDIAC CYCLE Step Step Mechanism Important Points No. Ventricular Contraction (Systole) Semilunar 10 Closure of aortic and Incisura: notch on descending Valve pulmonic valves prevents flow limb of aortic pressure curve Closure of blood back into ventricles. produced by closure of aortic valve, indicates end of ventricular systole. Ventricular Relaxation (Diastole) Iso- 11 Ventricles relax and Systemic arterial pressure volumetric ventricular pressure rapidly declines as blood continues to Relaxation falls without change in flow. ventricular volume. 17

Step Step Mechanism Important Points No. Ventricular Relaxation (Diastole) AV Valve 12 Rapid filling: high atrial pressure Normal diastolic pressure in Opening aorta: 80 mm Hg. (due to continued venous return Normal diastolic pressure during ventricular systole) causes pulmonary artery: 8-10 mmHg. initial rapid passive ventricular Tachycardia (>180 bpm) results filling (80% of blood volume). in decreased CO; ventricular 13 Pressure in atria and ventricles filling time is markedly reduced, decreases and ventricular which lowers VEDV and SV. relaxation continues during rapid Atrial contraction is not filling. essential for ventricular filling, as evidenced by adequate 14 Slow filling or diastasis: as blood ventricular filling in patients continues to return to heart,atrial without atrial contraction (eg, and ventricular pressures slowly atrial fibrillation or heart block). rise. Contribution of atrial contraction to ventricular 15 Ventricular filling of blood stops volume is more important when shen ventricles reach their volume HR is rapid and duration of limit. diastasis is short (eg, mitral stenosis). 16 Atrial contraction forces blood into ventricles to complete ventricular filling. 18

20 PHASE OF THE CARDIAC CYCLE

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II. The Heart As A Pump A. The Cardiac Cycle 1. Diastole constitudes 2/3 of the cycle (filling and isovolumetric contraction). Aortic pressure is higher than ventricular (aortic valve closed). 2. Systole accounts for 1/3 of the cardiac cycle(ejection and isovolumetric relaxation) 27

Cardiac Output (CO) Cardiac output = (stroke volume) x (heart rate) Fick Principle During exercise, CO initially Rate of O2 consumption CO = as a result of an in SV. Arterial O2 content - venous O2 content After prolonged exercise, CO as a result of an in HR. Mean arterial = cardiac x total peripheral If HR is too high, diastolic filling Similar to Ohms law: is incomplete and CO Voltage = (current) x (resistance) (e.g., ventricular MAP = systolic + 2/3 diastolic tachycardia) Pulse pressure = systolic - diastolic Pulse pressure = stroke volume 28

CO SV = = EDV - ESV HR SV EF = X 100% (normal 55-80%) EDV 29

Calculations of Stroke Volume, Cardiac Output & Ejection Fraction 30

Cardiac Output Variables Stroke volume affected by SV CAP. Contractility, Afterload, and Preload. Increased SV when Stroke volume in anxiety, preload, afterload, or exercise, and contractility. pregnancy. Contractility (and SV) with : A failing heart has stroke 1. Catecholamines ( activity of volume. Ca2+ pump in sarcoplasmic reticulum) 2. intracellular calcium 3. extracellular sodium 4. Digitalis ( intracellular Na+, resulting in Ca2+) 31

Cardiac Output Variables Contractility (and SV) Myocardial O2 demand is with: by: 1. 1 blockade 1. afterload ( diastolic 2. Heart failure BP) 3. Acidosis 2. contractility 4. Hypoxia/ hypercapnea 3. heart rate 4. heart size ( wall tension) 32

Cardiac Function Curve (Frank Starling Curve) 33

Diagram of normal blood pressures within heart chambers and great vessels 34

HEART SOUNDS Sound Cause of Events Sound S1 Closure of AV Just after onset of ventricular contraction. valves. Signals onset of ventricular systole. S2 Closure of Signals end of systole and onset of ventricular diastole. semilunar valves. Normal splitting: during inspiration, increased venous return causes prolongation of right ventricular EF and an increased separation between aortic valve closure (A2) and pulmonic valve closure (P2). Aortic valve closes first because ejection rate from left ventricle is higher than that from right ventricle. Paradoxical splitting occurs if splitting of S2 decreases during inspiration, indicating P2 precedes A2. Delayed aortic valve closure indicates a disease process affecting left ventricle(LBBB, aortic stenosis). 36

HEART SOUNDS Sound Cause of Events Sound S3 Rapid, passive At start of ventricular diastole. ventricular filling. Heard best at apex. Usually not heard in adults but may be heard in children or patients with LVE S4 Forcing of Atrial contraction. additional blood Occasionally heard in healthy individuals. into distended Individuals with CHF have triple sound called gallop ventricle. rhythm. 37

ATRIAL PRESSURE CHANGES VIA JUGULAR VENOUS TRACING Wave Timing of Wave Cause of Wave a Atrial contraction at end of Small amount of blood regurgitates into great ventricular diastole. veins. Venous inflow stops, causing rise in venous pressure c Isovolumetric contraction Rise in atrial pressure produced by bulging of AV valves into atria. v Ventricular diastole Rise in atrial pressure before AV valves open during diastole 38

40 Effect of Systolic and Diastolic Dysfunction on Pressure-Volume Relationship in the Left Ventricle