A 34-year-old man comes to the clinic for evaluation of a heart murmur. The patient has no chest pain, palpitations, dizziness, or shortness of breath at rest. He also exercises regularly without any abnormal symptoms. Cardiac auscultation in the second right intercostal space reveals an ejection click along with a soft systolic murmur radiating to the neck. A normal volume and pressure tracing of the left ventricle is shown in the image below. Which of the following letters corresponds to the opening of the valve most likely affected in this patient?
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This young, asymptomatic patient with a soft systolic ejection murmur at the right second intercostal space most likely has a bicuspid aortic valve.
The graph above depicts the normal left ventricular (LV) pressure and volume curves during the cardiac cycle. Ventricular pressure and volume curves allow one to identify the phases of the cardiac cycle and to determine the exact time of opening and closure of the cardiac valves. Aortic valve opening occurs when the LV pressure exceeds the central aortic pressure at the end of isovolumetric contraction. Subsequently, LV pressure continues to rise with forward blood flow into the aorta, until the pressure in the left ventricle falls below the aortic pressure leading to aortic valve closure.
(Choice A) The initial part of the LV pressure and volume curves corresponds to atrial systole, which results in a slight increase in LV volume and pressure. This is immediately followed by mitral valve closure and the beginning of isovolumetric contraction, where the LV pressure rises rapidly while LV volume remains constant.
(Choice C) This point corresponds to aortic valve closure, where LV pressure falls below the central aortic pressure. This also marks the beginning of isovolumetric relaxation, where the LV pressure rapidly falls while LV volume remains relatively constant.
(Choice D) Left atrial pressure gradually increases from passive filling from the pulmonary veins and exceeds LV pressure at the end of isovolumetric relaxation, leading to the opening of the mitral valves.
(Choice E) This point corresponds to passive LV filling with blood flow from the left atrium, which results in a gradual rise in LV volume and pressure.
Educational objective:
Ventricular pressure and volume curves allow one to identify the phases of the cardiac cycle and to determine the exact time of opening and closure of the cardiac valves. The aortic valve opens when left ventricular pressure exceeds the central aortic pressure at the end of isovolumetric contraction.