Hypertrophic Cardiomyopathy With Mitral Inflow Obstruction and Severe Pulmonary Hypertension
A 50-year-old man was admitted for progressive dyspnea (New York Heart Association functional class III) and episodes of paroxysmal nocturnal dyspnea. He had no significant past history of any illness or coronary artery risk factors. His blood pressure was 126/80 mm Hg; heart rate, 96 beats/min; peripheral oxygen saturation, 98%. Clinical examination found a prominent cardiac apex with grade II mid-diastolic murmur at the apex with a prominent pulmonary component of S2, jugular vein distension, and normal lung sounds. His ECG showed sinus tachycardia with left ventricular hypertrophy and left atrial enlargement (Figure 1). Chest radiography showed cardiomegaly with left atrial enlargement and grade III pulmonary venous hypertension (Figure 2). Transthoracic echocardiography showed normal left ventricular size with unusually hypertrophied papillary muscles. The thickness of interventricular septum was 14 mm, posterior wall thickness was 18 mm, and anterolateral wall was 20 mm. The hypertrophied papillary muscle extended to chordae tendineae and restricted opening of mitral valve leaflets causing mitral inflow obstruction (Figure 3A; Movie I in the online-only Data Supplement). The mean mitral inflow gradient was 7 mm Hg (Figure 3B). 3-dimensional echocardiography clearly demonstrated the direct insertion of thickened papillary muscle to the leaflets resulting in restricted mitral valve opening (Figure 3C and 3D; Movies II and III in the online-only Data Supplement). The calculated left ventricular (LV) mass was 552 g. The right ventricle was normal in size and function. There were a few muscle bundles within the right ventricle cavity. There was mild tricuspid regurgitation, and the estimated pulmonary artery systolic pressure was 106 mm\Hg. There was no evidence of rheumatic heart disease. There was no resting or inducible gradient across the LV outflow tract. Later cardiac catheterization was done to study the hemodynamic consequence of this abnormality. No abnormality was detected on the oxymetry run. The pulmonary artery systolic pressure was 102 mm Hg, and the mean pulmonary artery pressure was 65 mm Hg. The pulmonary capillary wedge pressure was 37/34/31 mm Hg. The end-diastolic mitral gradient was 14 mm Hg (Figure 4A). There was no gradient across the LV outflow tract (Figure 4B). The LV angiography showed a large convex-shaped filling defect with no obstruction in the LV outflow tract (Figure 5A; Movie IV in the online-only Data Supplement). Right ventricular angiography showed an unusual large oval-shaped filling defect within the right ventricle without causing a right ventricular outflow tract obstruction (Figure 5B; Movie V in the online-only Data Supplement). The cardiac MRI showed isolated hypertrophy of the anterolateral wall of the LV with abnormally hypertrophied papillary muscle within both right and left ventricles (Figure 6A through 6C). The thickness of the anterolateral wall was 32 mm, which was grossly underestimated on echocardiography. The hypertrophied papillary muscle measured 18 mm in thickness. There was patchy late gadolinium enhancement of the anterolateral wall of the LV (Figure 6D). Cine MRI beautifully demonstrated direct insertion of papillary muscle into mitral leaflets (Movies VI and VII in the online-only Data Supplement). There was exaggerated diastolic flow reversal into the pulmonary veins as shown in Movie VIII in the online-only Data Supplement. The patient showed significant improvement with diuretics and a β-blocker.
The involvement of myocardium in hypertrophic cardiomyopathy (HCM) is often nonuniform, and the extent of hypertrophy at any given site can vary greatly and bears importantly on the manifestations of the disease.1
Transthoracic echo/Doppler examination in HCM is undoubtedly the most important imaging modality. These combined techniques can determine the location and extent of hypertrophy, systolic and diastolic function, the presence and degree of systolic anterior motion, the severity of LV outflow tract obstruction, the degree of mitral regurgitation, the presence of additional mitral valve abnormalities, etc. However, the involvement of the anterolateral wall may be difficult to visualize on echocardiography, as seen in our patient. The involvement of the papillary muscles may occur in up to 59% of patients with nonobstructive HCM.2 Papillary muscle abnormalities may involve the direct insertion of the papillary muscle into the mitral valve resulting in mitral inflow obstruction and pulmonary venous and arterial hypertension as seen in our patient. Three-dimensional echocardiography also provides more information about the distribution of hypertrophy within the LV myocardium than 2-dimensional echocardiography.3
Cardiac magnetic resonance imaging in addition to echocardiography has lessened the need for invasive investigation in HCM. Cardiac magnetic resonance imaging is particularly useful for characterizing the presence, location, and extent of LV hypertrophy in HCM, which can be limited to 1 or 2 LV segments in ≈10% of the HCM population.4
Atypical HCM is not uncommon and poses a diagnostic challenge. The utility of multiple imaging modalities may assist in reaching the correct diagnosis, studying the hemodynamic consequence of the disease, and delivering appropriate therapy.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/lookup/suppl/doi:10.1161/CIRCULATIONAHA.112.000888/-/DC1.
- © 2013 American Heart Association, Inc.