Hemodynamic Consequences of Hypertrophic Cardiomyopathy with Midventricular Obstruction: Apical Aneurysm and Thrombus Formation

Abstract

Background: Hypertrophic cardiomyopathy (HCM) with midventricular hypertrophy is an uncommon phenotypic variant of the disease. Midventricular hypertrophy predisposes to intracavitary obstruction and downstream hemodynamic sequelae.

Case report: We present a case of HCM with midventricular hypertrophy and obstruction diagnosed after a CT scan of the abdomen incidentally revealed a filling defect in the left ventricular apex. Transthoracic echocardiography demonstrated mid left ventricular hypertrophy and obstruction, as well as an aneurysmal apex containing a large thrombus. Cardiovascular MRI showed a spade-shaped left ventricle with midcavitary obliteration, an infarcted apex and regions of myocardial fibrosis. Due to the risk of embolization and a relative contraindication to anticoagulation, the patient underwent surgery including thrombectomy, septal myectomy and aneurysmal ligation.

Conclusions: Hypertrophic cardiomyopathy with midventricular hypertrophy leads to cavity obstruction, increased apical wall tension, ischemia and ultimately fibrosis. Over time, patchy apical fibrosis can develop into a confluent scar resembling a transmural myocardial infarction in the left anterior descending coronary artery distribution. Aneurysmal remodeling of the left ventricular apex potentiates thrombus formation and risk of cardioembolism. For these reasons, hypertrophic cardiomyopathy with midventricular obstruction portends a particularly poor prognosis and should be recognized early in the disease process.

Keywords: Aneurysmal apical chamber; Cardiovascular magnetic resonance imaging of hypertrophic cardiomyopathy; Hypertrophic cardiomyopathy; Midcavity obstruction; Midventricular hypertrophy; Paradoxic diastolic jet flow in hypertrophic cardiomyopathy.

Figure 1

Two-dimensional transthoracic echocardiography and Doppler. A. The two-chamber view in mid diastole demonstrates a large mass at the left ventricular apex (arrow). B. Contrast-enhanced two chamber view in systole shows apposition of mid anterior and inferior segments resulting in an hourglass configuration of the left ventricle with separate apical (blue arrow) and basal chambers (red arrow). C. Color Doppler in early diastole reveals paradoxic flow (blue) from the apex toward the base due to blood previously trapped in apical chamber during systole. Red flow represents simultaneous, passive mitral inflow from the base toward the apex. D. Color M-mode confirms paradoxic flow (blue arrow) in early diastole and concurrent mitral inflow (red arrow). E. Contrast-enhanced continuous wave Doppler revealed a peak systolic velocity of 3.2 m/s (blue arrow) corresponding to a gradient of 41 mm Hg. Color Doppler (not shown) showed aliasing systolic flow with apposition of the midventricular segments, confirming the midcavitary level of obstruction. Continuous wave Doppler also demonstrated the paradoxic, early diastolic flow with a peak velocity of 2.7 m/s (red arrow) corresponding to a gradient of 29 mm Hg. F. Continuous wave Doppler performed postoperatively revealed no significant intracavitary obstruction. An insignificant jet of early diastolic flow (red arrow) persisted however. LA: Left atrium; LV: Left ventricle

Figure 2

Cardiovascular magnetic resonance imaging. A. Steady-state free precession image of the two-chamber view at end diastole demonstrating a spade-shaped left ventricular cavity with mid ventricular hypertrophy and aneurysmal apex containing a mass (arrow) measuring 24 × 20 mm. B. The corresponding view at end systole demonstrates midventricular cavity obliteration resulting in separate apical (blue arrow) and ventricular chambers (red arrow). C. Late gadolinium enhancement imaging shows transmural fibrosis (bright) of the myocardium (red arrow). The periphery of the apical mass enhances (blue arrow) while the core remains hypointense (black), consistent with thrombus. D. Late gadolinium enhancement imaging of a short-axis mid ventricular view also demonstrates inferoseptal right ventricular insertion fibrosis (blue arrow) and patchy fibrosis of the interventricular septum (red arrow), consistent with hypertrophic cardiomyopathy. IVS: Interventricular septum; LA: Left atrium; LV: Left ventricle

Figure 3

Histopathological evaluation of excised myocardium with hematoxylin and eosin staining revealed hypertrophied myocytes with hyperchromatic nuclei and fibrosis.