In patients with hypertrophic obstructive cardiomyopathy and dynamic left ventricular outflow tract obstructions, an additional fixed obstruction may uncommonly coexist. In these situations, flow through the aortic valve is usually delayed but typically still throughout the entire ejection period. We describe a case of marked reduction in aortic flow during mid and late systole, diagnosed by Doppler echocardiography, caused by combined hypertrophic obstructive cardiomyopathy and severe calcific bicuspid aortic stenosis.
A 59-year-old woman was referred for evaluation dyspnea and exertional near-syncope, thought to be due to dynamic left ventricular outflow tract (LVOT) obstruction. At the age of 21 years, an incidental systolic murmur was confirmed to be the result of a bicuspid aortic valve. At the present evaluation, physical examination noted a harsh late peaking systolic ejection murmur and thrill (grade 5/6) at the right second intercostal space with radiation to the neck. A second blowing diastolic murmur (grade 2/6) was heard at the left sternal border fourth intercostal space.
Two- and three-dimensional transthoracic echocardiography revealed LVOT obstruction caused by septal wall hypertrophy, systolic anterior motion of the mitral valve associated with moderate mitral insufficiency, a heavily calcified aortic valve with mild to moderate aortic regurgitation, and a dilated proximal aortic root (4.5 cm) ( Figure 1 A-D, Video 1 A-C). Two distinct systolic LVOT gradients were demonstrated: a mid peaking high-velocity symmetric Doppler contour typical of aortic stenosis (calculated mean gradient 40 mm Hg) ( Figure 2 A), due to a bicuspid aortic valve, and a second asymmetric late-peaking “dagger-shaped” velocity (peak gradient 108 mm Hg) ( Figure 2 B) typical of dynamic outflow obstruction. The aortic stenosis velocity profile abruptly decreased at 230 ms after onset of the systolic period, measured from the opening click visualized on continuous-wave Doppler interrogation, with low-velocity flow recorded during the remainder of systole to aortic valve closure ( Figure 2 A). The dynamic outflow velocity contour begins a marked acceleration at 230 ms of the systolic flow period, coincident with the sudden decline in aortic velocity, peaks at 260 ms, and continues to aortic valve closure ( Figure 2 B). These Doppler profiles illustrate the marked reduction of aortic flow immediately after peak flow caused by a coexistent, severe LVOT dynamic obstruction with resultant diminution in flow across the aortic valve to approximately 1.2 m/sec at 230 ms post-opening of the aortic valve. This relationship is further illustrated in simultaneous velocity-time and pressure-time diagrams ( Figure 3 ). This reduction of flow into the aorta is likely responsible for the patient’s symptoms. The velocity profile for aortic stenosis typically demonstrates a gradual decay from its peak velocity during late systole that extends to aortic valve closure ( Figure 4 ), consistent with the reduced but continuous forward flow during the latter half of systole. In our patient, however, the dynamic outflow obstruction induced by septal hypertrophy and systolic anterior motion of the mitral valve markedly reduces systolic flow through the aortic valve. The reduced subvalvular flow at the time the dynamic obstruction worsens, combined with severe aortic stenosis, culminates in a sudden and significant diminution of flow into the proximal aorta during mid to late systole. Associated aortopathy was also noted with an ascending aortic aneurysm. Because of this constellation of findings and worsening symptoms of dyspnea and exertional near-syncope, surgery was recommended.