The Pathophysiology of Valvular Disease

Question 1

what are the 7 phases of the cardiac cycle?

Answer 1

(1) atrial systole (2) isovolumetric contraction (3) rapid ejection (4) reduced ejection (5), isovolumetric relaxation (6) rapid filling (7) reduced filling.

Question 2

Explain atrial systole?

Answer 2

• P wave occurs • Atrial contraction (a wave) • Pushed 10-30% more blood into ventricle

Question 3

Explain Isovolumetric contraction?

Answer 3

• QRS just occurred • Contraction of the ventricles causes ventricular pressure to rise above atrial pressure, • AV valves close (first heart sound; the first heart sound (S1, “lub”) is due to the closing AV valves and associated blood turbulence. • Ventricular pressure is still less than aortic pressure • Semilunar valves are closed • Volume of blood in the ventricle is EDV

Question 4

Explain rapid ejection?

Answer 4

• Contraction of the ventricles causes ventricular pressure to rise above aortic pressure, • Semilunar valves open • Ventricular pressure is still greater than atrial pressure • AV valves are still closed • Volume of blood ejected by the ventricles: Stroke Volume

Question 5

Explain reduced ejection?

Answer 5

• T-wave occurs • Ventricular pressure drops below aortic pressure • Back pressure causes semilunar valves to close (second heart sound; the second heart sound (S2, “dup”) occurs when the semilunar (aortic and pulmonary) valves close. S2 is normally split because the aortic valve closes slightly earlier than the pulmonary valve.

Question 6

Explain isovolumetric contraction?

Answer 6

• AV valves are still closed • Semilunar valves are still closed • Volume of blood in ventricles: ESV

Question 7

Explain rapid filling?

Answer 7

• Ventricular pressure drops below atrial pressure • AV valves are open, semilunar valves are closed • Rapid ventricular filling occurs • 70-90% of the ventricles fill with blood

Question 8

What is reduced filling?

Answer 8

• Rest of blood that has accumulated in the atria flows slowly into the ventricles.

Question 9

Explain pressure-volume loops in the ventricle.

Answer 9

• a, ventricular filling; • b, isovolumetric contraction; • c, ventricular ejection; • d, isovolumetric relaxation; • EDV and ESV, left ventricular enddiastolic and endsystolic volumes, respectively; • EDPVR, enddiastolic pressure-volume relationship; • ESPVR, end-systolic pressure-volume relationship; • SV, stroke volume (EDV – ESV).

Question 10

Explain an S2 split?

Answer 10

During inspiration, the chest wall expands and intrathoracic pressure becomes more negative. The increased negative pressure induces an increase in venous blood return to the right heart. Simultaneously, there is a reduction in blood volume returning from the lungs into the left heart. Since there is an increase in blood volume in the right ventricle during inspiration, the pulmonary valve stays open longer during ventricular systole due to an increase in ventricular emptying time. In contrast, the aortic valve closes slightly earlier due to a reduction in left ventricular volume and ventricular emptying time. During expiration, the chest wall collapses and decreases the negative intrathoracic pressure (compared to inspiration). Therefore, there is no longer an increase in blood return to the right ventricle versus the left ventricle and the right ventricle volume is no longer increased. This allows the pulmonary valve to close earlier such that it overlaps the closing of the aortic valve, and the split is no longer heard.

Question 11

how does changing afterload change stroke volume? how does changing afterload affect starling curves?

Answer 11

An increase in afterload shifts curve downward. At a given preload, an increase in afterload decreases stroke volume. A decrease in afterload would shift curve upward resulting in an increase SV at same preload