Cardiac cycle Dr. shafali singh

Learning Objectives Interpret in correct temporal relationship, the pressure, volume, heart sound, and ECG changes in the cardiac cycle. Identify the intervals of isovolumic contraction, rapid ejection, reduced ejection, isovolumic relaxation, rapid ventricle filling, reduced ventricular filling and atrial contraction. Contrast the relationship between pressure and flow into and out of the left and right ventricles during each phase of the cardiac cycle. Interpret ventricular pressure-volume loop and on it label the phases and events of the cardiac cycle (ECG, valve movement).

CARDIAC CYCLE ELECTRICAL CHANGE MECHANICAL CHANGE HEMODYNAMIC CHANGE HEART SOUNDS

Cardiac cycle Atria Ventricle The cardiac events that occur from beginning of one heart beat to the next are called the cardiac cycle Atria Atrial systole Atrial diastole Ventricle Ventricular systole Ventricular diastole

Heart beat duration (rate is 75 beat/min)

Duration of cardiac cycle HEART RATE : 75/MIN HENCE DURATION FOR ONE CYCLE IS: 60/75 = 0.8 Sec ATRIAL CYCLE ATRIAL SYSTOLE - 0.1 SEC ATRIAL DIASTOLE- 0.7 SEC VENTRICULAR CYCLE VENTRICULAR SYSTOLE – 0.3 SEC VENTRICULAR DIASTOLE – 0.5 SEC

What happens to time spent and systole and diastole with tachycardia? Under Normal condition:n1/3rd time in systole and 2/3rd in diastole Tachycardia : time spent in diastole decreases dramatically whereas time spent in systole falls to lesser extent.

CARDIAC CYCLE IF HR ↑ - 150 / MIN CARDIAC CYCLE – 0.4 Sec SYSTOLE 0.25 Sec DIASTOLE 0.15 Sec HENCE LITTLE TIME FOR VENTRICULAR FILLING

Mechanical Events of Cardiac cycle Atrial systole Isovolumic contraction phase Rapid ejection phase Reduced ejection phase Isovolumic relaxation phase Rapid filling phase Reduced filling phase (Diastasis) Last rapid filling phase

ATRIAL SYSTOLE Last phase of ventricular diastole Drives some more blood into the ventricles Increases the ventricular filling by 35% 0.1 Sec Coincides with ‘a‘ wave of JVP Contraction of atria-Fourth Heart sound

VENTRICULAR SYSTOLE

1.ISOVOLUMETRIC CONTRACTION Coincides with ‘c ‘wave in JVP Semilunar valve : remain closed AV valves close – First Heart sound Closed chamber – Contracts No change in the volume BLOOD INCOMPRESSIBLE Intraventricular pressure ↑

2.EJECTION PHASE ↑ Intraventricular pressure > 80mm Hg- Diastolic pressure of Aorta Or > 10mmHg- Diastolic pressure of Pulmonary arteries Semilunar valves forced to open Blood flows into arteries from ventricle

EJECTION PHASE MAXIMAL EJECTION – Due to High Pressure gradient - Blood is ejected into Aorta/Pul. Art. REDUCED EJECTION – Due to decreased Pressure gradient STROKE VOLUME – 70 ml END SYSTOLIC VOLUME = 40-50 ml EDV – SV = ESV [120 – 70 = 50]

Ventricular diastole 1.Protodiastolic period – 2.Isovolumetric relaxation – 3.Rapid filling phase – 4.Reduced filling phase (Diastasis) 5.Last rapid filling phase/ Atrial systole follows

1.PROTODIASTOLIC PHASE Ventricle relaxes Intraventricular pressure < pressure in the aorta/Pul.Arteries Blood flows back from aorta/pul art into ventricle SLV closes -Second heart sound

2.ISOVOLUMETRIC RELAXATION SLV and AV valves closed Ventricle relaxes as closed chamber No volume change Intraventricular pressure ↓

3.RAPID INFLOW PHASE ↓Intraventricular pressure< intra atrial pressure Hence AV valves open Blood flows from atria to ventricle Third heart sound

4.DIASTASIS ↑ in intraventricular pressure due to ↑blood flow from atria Blood flow from atria to ventricle at low rate or static Duration of diastasis variable

During diastole there is passive filling of the relaxed left ventricle During diastole there is passive filling of the relaxed left ventricle. The ventricle does not suck blood into the lumen. Filling is by the venous pressure.

The first sign of activity in the heart is the atrial contraction The first sign of activity in the heart is the atrial contraction. This weak structure pushes a small amount of blood into the ventricle (atrial kick) Blood is also propelled back into the veins giving rise to the A-wave. Not vital.

Isovolumetric contraction occurs as the ventricle starts to contract Isovolumetric contraction occurs as the ventricle starts to contract. The mitral valve closes The ventricular pressure rises toward aortic pressure . The mitral valve bulges into the atrium causing the C wave in venous pressure

Ejection phase starts as the aortic valve opens Ejection phase starts as the aortic valve opens. The ventricular contents are ejected during this time.

Isovolumetric relaxation begins as the aortic valve closes Isovolumetric relaxation begins as the aortic valve closes. Ventricular pressure falls from aortic to left atrial during this period.

Diastolic filling begins again as the mitral valve opens Accumulated blood in the atrium rushes into the ventricle Movement of blood into the ventricle causes venous pressure to drop suddenly causing the V wave

EKG EVENT VALVULAR EVENT SOUND P wave Atrial depolarisation Mitral valve open (ventricle is filling) S4 (S3 prior to P wave) PR interval AV Node conduction - QRS Ventricular depolarization Mitral valve close S1 QT interval Ejection phase Aortic valve is open No sound T wave Ventricular repolarization Aortic valve closure S2

HEMODYNAMIC CHANGES Pressure and volume changes in the atria & ventricle during cardiac cycle Intra atrial pressure curve Intraventricular pressure curve Aortic pressure curve Ventricular volume curve

INTRA-ATRIAL PRESSURE CURVE Pressure changes in the atria is reflected in the veins near the heart, eg.jugular vein acv curve – Jugular Phlebogram - JVP

PHLEBOGRAM 3 Positive waves – a,c &v 2 Negative waves x &y 3 4 2 a 1 v AS VS VD

The jugular pulse waves are superimposed on the respiratory fluctuations in venous pressure. Venous pressure falls during inspiration as a result of the increased negative intrathoracic pressure and rises again during expiration

Venous Pulse a wave Highest deflection of the venous pulse and produced by the contraction of the right atrium Correlates with the PR interval Is prominent in a stiff ventricle, pulmonic stenosis and insufficiency Is absent in atrial fibrillation and other atrial arrhythmias The jugular pulse waves are superimposed on the respiratory fluctuations in venous pressure. Venous pressure falls during inspiration as a result of the increased negative intrathoracic pressure and rises again during expiration

Venous Pulse c wave Mainly due to the bulging of the tricuspid valve into the atrium (rise in right atrial pressure) Occurs near the beginning of ventricular contraction (is coincident with right ventricular isovolumic contraction) The jugular pulse waves are superimposed on the respiratory fluctuations in venous pressure. Venous pressure falls during inspiration as a result of the increased negative intrathoracic pressure and rises again during expiration

Venous Pulse x descent Produced by a decreasing atrial pressure during atrial relaxation Separated into two segments when the c wave is recorded v wave Produced by the filling of the atrium during ventricular systole when the tricuspid valve is closed Corresponds to T wave of the EKG A prominent v wave would occur in tricuspid insufficiency and right heart failure

Venous Pulse y descent Produced by the rapid emptying of the right atrium immediately after the opening of the tricuspid valve A more prominent wave in tricuspid insufficiency and a blunted wave in tricuspid stenosis

A more prominent v wave in tricuspid insufficiency and a blunted wave in tricuspid stenosis

A common diagnostic technique is to place catheters at various points in the cardiovascular system and record their pressures.

Similar recordings to the systemic venous pulse are obtained when recording pulmonary capillary wedge pressure. Left atrium mechanical events are transmitted in a retrograde manner, although they are somewhat damped and delayed. The figure below shows the pressure recording from the tip of a Swan-Ganz catheter inserted through a systemic vein through the right side of the heart into the pulmonary circulation and finally with the tip wedged in a small pulmonary artery. The pressure recorded at the tip of the catheter is referred to as pulmonary capillary wedge pressure and is close to left atrial pressure and is an index of preload on the left ventricle

INTRAVENTRICULAR PRESSURE CURVE Ejection phase Closure of SLV 4 SLV opens Protodiastole 3 5 Isovolumetric Relax Isovolumetric contr Right Ventricular pressure changes Similar to LV pressure changes Peak pressure during systole is 25 mm Hg Diastole pressure 2 mm Hg 6 AV valves open Atrial systole VD 2 7 1 Closure of AV Valve AS VS VD

AORTIC PRESSURE CURVE 1 – SLV open 2 – Max. Ej. Phase 2-3 – Reduced Ej. Phase 3 – End of Vent. Diastole 4 - SLV closes 5 – Small positive wave 2 120 5 3 100 4 Incisura 1 80 VS VD

VENTRICULAR VOLUME CHANGES 120 I V R I V C A S 60ml VS VD

Blood pressure rises during systole and falls during diastole. The difference between the peak and the trough is called the pulse pressure

A is atrial systole. Causes the A wave in atrial pressure. Helps fill the ventricle.

B is Isovolumic contraction. It starts with mitral valve closure Both the aortic and mitral valves are closed so the ventricle’s volume is constant.

C is rapid ejection period. It starts with aortic valve opening. Ventricular pressure leads aortic. Flow out of the ventricle is accelerating.

D is the reduced ejection period. Aortic pressure leads ventricular. Flow out of the ventricle is decelerating.

E is the isovolumetric relaxation period. Begins with aortic valve closure. Ventricular volume is constant Gives rise to the V wave as blood accumulate in the atrium

F is the rapid filling period. Begins with opening of the mitral valve. Gives rise to the y wave as blood accumulated in the atrium rushes into the ventricle. y

G is the reduced filling period(diastasis). Ventricular filling is now in equilibrium with venous return.

Events on the right side are the same except the pressure is lower.

Left ventricular end-diastolic volume (LVEDV) Left ventricular end-systolic volume (LVESV) stroke volume= LVEDV-LVESV  cardiac output = stroke volume x heart rate

Since there are no valves between the atrium and veins atrial pressure is essentially equal to venous pressure. Notice the venous pressure trace with A, C and V waves

Ventri Q1. Ventricular filling begins at point? D and B Q1. Ventricular filling begins at point? Q2. Closure of mitral valve begins at point?

The volume and pressure tracings for the left ventricle of a 34 year old male are shown below. Which of the following points correspond to aortic valve opening? A B C D E

PRESSURE-VOLUME LOOPS

1 → 2 (isovolumetric contraction) 1 → 2 (isovolumetric contraction). The cycle begins during diastole at point 1. The left ventricle is filled with blood from the left atrium and its volume is about 140 mL (end-diastolic volume). Ventricular pressure is low because the ventricular muscle is relaxed. On excitation, the ventricle contracts and ventricular pressure increases. The mitral valve closes when left ventricular pressure is greater than left atrial pressure. Because all valves are closed, no blood can be ejected from the ventricle (isovolumetric). b. 2 → 3 (ventricular ejection). The aortic valve opens at point 2 when pressure in the left ventricle exceeds pressure in the aorta. Blood is ejected into the aorta, and ventricular volume decreases. The volume that is ejected in this phase is the stroke volume. Thus, stroke volume can be measured graphically by the width of the pressure-volume loop. The volume remaining in the left ventricle at point 3 is end-systolic volume c. 3 → 4 (isovolumetric relaxation). At point 3, the ventricle relaxes. When ventricular pressure decreases to less than aortic pressure, the aortic valve closes. Because all of the valves are closed again, ventricular volume is constant (isovolumetric) during this phase. d. 4 → 1 (ventricular filling). Once left ventricular pressure decreases to less than left atrial pressure, the mitral (AV) valve opens and filling of the ventricle begins. During this phase, ventricular volume increases to about 140 mL (the end-diastolic volume

Q.On the graph showing left ventricular volume and pressure, isovolumetric contraction occurs from point (A) 4 → 1 (B) 1 → 2 (C) 2 → 3 (D) 3 → 4 Q The aortic valve closes at point (A) 1 (B) 2 (C) 3 (D) 4

Q The first heart sound corresponds to point (B) 2 (C) 3 (D) 4

If the heart rate is 70 beats/min, then the cardiac output of this ventricle is closest to (A) 3.45 L/min (B) 4.55 L/min (C) 5.25 L/min (D) 8.00 L/min (E) 9.85 L/min 140 70

The ejection fraction equals b. 0.55 c. 0.60 d. 0.65 e. 0.70

Mechanically Altered States Preload Afterload Increased contractility Exercise Heart failure Aortic stenosis Aortic insufficiency Mitral stenosis Mitral insufficiency