A 25-year-old man with an insignificant medical history was playing soccer when he suddenly collapsed. Despite all attempts to save his life, he died. Autopsy is performed. Gross examination of the heart reveals a weight of 580 g (normal: <350). The cut surface of the heart is shown in the image.
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If this patient had a preparticipation sports screening, cardiac auscultation would have likely revealed a murmur that increases in intensity after which of the following?
Effect of maneuvers on hypertrophic cardiomyopathy | |||
Physiologic effect | Left ventricular | Murmur intensity | |
Valsalva | ↓ Preload | ↓ | ↑ |
Abrupt | |||
Nitroglycerin | |||
Sustained | ↑ Afterload | ↑ | ↓ |
Squatting | ↑ Afterload & preload | ||
Passive | ↑ Preload | ||
This patient's heart shows asymmetric ventricular septal hypertrophy, a finding characteristic of hypertrophic cardiomyopathy (HCM). Dynamic left ventricular outflow tract (LVOT) obstruction is common in HCM and creates a harsh crescendo-decrescendo, systolic ejection murmur that is best heard along the lower left sternal border.
Maneuvers or conditions that decrease LV preload (eg, abrupt standing, Valsalva strain phase, dehydration) or decrease LV afterload (eg, administration of an arterial vasodilator) decrease LV blood volume to worsen LVOT obstruction and increase the intensity of the HCM murmur. In contrast, maneuvers or conditions that increase LV preload (eg, passive leg raising, squatting) or increase LV afterload (eg, infusion of an arterial vasoconstrictor like the alpha-1 agonist phenylephrine, sustained handgrip) increase LV blood volume to alleviate LVOT obstruction and decrease the intensity of the HCM murmur (Choices A, B, C, and E).
The murmur of HCM is best differentiated from that of aortic stenosis by maneuvers that affect LV preload. Unlike HCM, the intensity of the aortic stenosis murmur correlates directly with LV preload. Increases in LV preload increase the pressure gradient across the aortic valve and increase the intensity of the murmur, whereas decreases in LV preload decrease the intensity of the murmur. Changes in afterload have the same effect on the murmurs of HCM and aortic stenosis, but for different reasons. In HCM, increased afterload increases LV blood volume to relieve LVOT obstruction and decrease the intensity of the murmur. In aortic stenosis, increased afterload decreases the pressure gradient across the aortic valve to decrease the intensity of the murmur.
Educational objective:
Hypertrophic cardiomyopathy (HCM) is characterized by asymmetric ventricular septal hypertrophy and dynamic left ventricular outflow tract (LVOT) obstruction. Decreases in LV blood volume, via maneuvers or conditions that decrease preload (eg, abrupt standing, Valsalva strain phase) or afterload, worsen LVOT obstruction and increase the intensity of the HCM murmur.