Cardiac cycle — MCQs

A 72-year-old man with severe aortic regurgitation and compensated heart failure is being evaluated for surgical intervention. His echocardiogram shows LV end-diastolic dimension of 7.5 cm, ejection fraction of 45%, and severe aortic regurgitation with a regurgitant fraction of 60%. Pressure-volume loop analysis shows a markedly widened loop with increased stroke work. Evaluate the compensatory mechanisms maintaining his cardiac output and predict the timing for surgical intervention based on cardiac cycle mechanics.

A 35-year-old woman with constrictive pericarditis undergoes right heart catheterization showing equalization of diastolic pressures across all cardiac chambers (RA, RV, PA, PCWP all approximately 20 mmHg). Ventricular pressure tracings show a distinctive 'square root sign' during diastole. Evaluate the mechanism by which pericardial constriction alters the normal pressure dynamics during the cardiac cycle and predict the effect on cardiac output during exercise.

A 58-year-old man with severe coronary artery disease develops a ventricular aneurysm following an anterior myocardial infarction. Pressure-volume loop analysis shows a distinctive notch during the ejection phase. He has reduced ejection fraction of 30% but normal filling pressures. Evaluate the pathophysiologic mechanism explaining the notch in the pressure-volume loop and its clinical significance.

A 62-year-old man with hypertrophic cardiomyopathy undergoes hemodynamic monitoring showing a left ventricular pressure of 180 mmHg during systole, while simultaneous aortic pressure is 110 mmHg. After the aortic valve closes, left ventricular pressure drops rapidly but remains elevated at 25 mmHg when the mitral valve should open. Analyze the mechanism for delayed mitral valve opening.

A 45-year-old woman with rheumatic heart disease develops atrial fibrillation. Her cardiologist notes that her cardiac output has decreased by approximately 20% despite unchanged heart rate and contractility. Analyze the mechanism by which loss of atrial contraction affects ventricular performance during the cardiac cycle.