Hypertrophic cardiomyopathy (HCM) is characterised by a heterogeneous clinical expression, unique pathophysiology and diverse natural history. Longstanding left ventricular (LV) outflow tract obstruction is a strong determinant of HCM-related progressive heart failure and cardiovascular death. Here we report the clinical features and natural history of a young female with HCM and mid-cavity obstruction who became symptomatically better after apical myocardial infarction which resulted in the loss of mid-cavity obstruction.

A 40-year-old woman presented with a history of progressive worsening of dyspnoea on exertion over the previous 6 months. She had been diagnosed with hypertrophic obstructive cardiomyopathy at the age of 28 years when she had recurrent episodes of syncope. Most of the syncopal episodes were exertional and started 3 years prior to the diagnosis. Her ECG at that time showed LV hypertrophy with T inversion in lateral chest leads (figure 1A) and echocardiographic examination showed severe LV hypertrophy with mid-cavity obstruction and near total obliteration of the LV apex in systole. The mid-cavity obstruction was dynamic with a peak gradient of 75 mm Hg (figure 1B–E). The patient was on oral propanolol 40 mg thrice daily. She had been lost to follow-up for the previous 10 years mainly because she felt better with no further syncope and discontinued all medications. Currently, she has NYHA class II heart failure.

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Figure 1

(A) 12-Lead electrocardiogram showing T wave inversion in lateral chest leads. (B–E) Transthoracic echocardiogram views showing severe concentric left ventricular hypertrophy and a mid-cavity gradient.

On examination her heart rate was 90/min with blood pressure of 120/80 mm Hg. She was not in heart failure and had a short mid-systolic murmur over the left sternal border. Her chest skiagram showed cardiomegaly (figure 2A). Electrocardiogram showed deep Q waves in leads V4, V5, V6 and an R/S ratio >1 in V1 and V2 suggesting an apical and postero-lateral myocardial infarction (figure 2B). Echocardiographic examination showed an akinetic apex, apical lateral wall and apical septum with moderate LV systolic dysfunction. There was a marked reduction in LV hypertrophy with no mid-cavity gradient (figure 2C,D, see online supplementary video 1). Mild pericardial effusion was present. Coronary angiogram showed normal epicardial coronary arteries. Gadolinium-enhanced cardiac MRI showed delayed subendocardial enhancement in the infero-lateral myocardium at the mid-cavity level and at the apex, suggestive of a myocardial scar (figure 2E–G). Currently, the patient is on β blockers, a statin, diuretics and antiplatelets with symptomatic improvement.

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Figure 2

(A) Chest X-ray showing cardiomegaly. (B) 12-Lead ECG showing Q waves in infero-lateral leads. (C) Transthoracic echocardiogram image showing left ventricular basal hypertrophy and moderate pericardial effusion. (D) Colour Doppler echocardiogram image showing no significant intra-cavity flow turbulence. (E–G) Gadolinium-enhanced MRI showing delayed enhancement in the lateral wall (arrow).

This case highlights the natural history of HCM with mid-cavity obstruction. Mid-cavity obstruction is seen in up to 25% of HCM cases and is due to hypertrophied papillary muscle abutting on the LV free wall during systole. Outflow obstruction may be associated with mid-cavity obstruction. Apical aneurysm formation is seen in up to 35% of patients with mid-cavity obstruction, most of whom will have normal epicardial coronary arteries. Aneurysm formation is associated with focal myocardial scarring as demonstrated by delayed enhancement in contrast-enhanced cardiac MRI. Formation of these scars is attributed to increased apical wall tension due to mid-cavity obstruction. The presence of mid-cavity obstruction is an independent determinant of unfavourable outcome. In addition, apical aneurysm formation more strongly predicted HCM-related sudden death. Apical systolic dysfunction due to apical aneurysm formation may reduce the mid-cavity gradient. Our patient developed apical myocardial infarction and there was regression of hypertrophy and loss of the previous mid-cavity gradient. Moreover, the disappearance of syncopal episodes in spite of apical myocardial infarction and LV dysfunction suggests that syncope in this patient is likely due to mid-cavity obstruction.1–3