Apical Ischemia Is a Universal Feature of Apical Hypertrophic Cardiomyopathy

Abstract

Background: Apical hypertrophic cardiomyopathy (ApHCM) accounts for ≈10% of hypertrophic cardiomyopathy cases and is characterized by apical hypertrophy, apical cavity obliteration, and tall ECG R waves with ischemic-looking deep T-wave inversion. These may be present even with <15 mm apical hypertrophy (relative ApHCM). Microvascular dysfunction is well described in hypertrophic cardiomyopathy. We hypothesized that apical perfusion defects would be common in ApHCM.

Methods: A 2-center study using cardiovascular magnetic resonance short- and long-axis quantitative adenosine vasodilator stress perfusion mapping. One hundred patients with ApHCM (68 overt hypertrophy [≥15 mm] and 32 relative ApHCM) were compared with 50 patients with asymmetrical septal hypertrophy hypertrophic cardiomyopathy and 40 healthy volunteer controls. Perfusion was assessed visually and quantitatively as myocardial blood flow and myocardial perfusion reserve.

Results: Apical perfusion defects were present in all overt ApHCM patients (100%), all relative ApHCM patients (100%), 36% of asymmetrical septal hypertrophy hypertrophic cardiomyopathy, and 0% of healthy volunteers (P<0.001). In 10% of patients with ApHCM, perfusion defects were sufficiently apical that conventional short-axis views missed them. In 29%, stress myocardial blood flow fell below rest values. Stress myocardial blood flow was most impaired subendocardially, with greater hypertrophy or scar, and with apical aneurysms. Impaired apical myocardial blood flow was most strongly predicted by thicker apical segments (β-coefficient, -0.031 mL/g per min [CI, -0.06 to -0.01]; P=0.013), higher ejection fraction (-0.025 mL/g per min [CI, -0.04 to -0.01]; P<0.005), and ECG maximum R-wave height (-0.023 mL/g per min [CI, -0.04 to -0.01]; P<0.005).

Conclusions: Apical perfusion defects are universally present in ApHCM at all stages. Its ubiquitous presence along with characteristic ECG suggests ischemia may play a disease-defining role in ApHCM.

Keywords: apical hypertrophic cardiomyopathy; cardiomyopathy; humans; hypertrophic; hypertrophy; stroke volume.

Figure 1.

Long-axis cardiac magnetic resonance and ECG appearances of overt versus relative apical hypertrophic cardiomyopathy (ApHCM). Images depict overt ApHCM on the left (Ai-Di) and relative ApHCM on the right (Aii-Dii). End-diastolic frames of 4-chamber (Ai, Aii) and 2-chamber (Ci, Cii) show apical hypertrophy and "ace of spades" appearance of left ventricular cavity (more marked in overt disease). End-systole (Bi, Bii, Di, Dii) demonstrate apical cavity systolic obliteration, extending more basally in overt disease. ECGs show similar appearances with deep T-wave inversion in the precordial leads.

Figure 2.

Stress and rest quantitative perfusion maps in health and disease. Rest and stress perfusion maps in 3 short-axis and 1 long-axis view. The color scale (right) denotes myocardial blood flow in mL/g per min. Rest flow is normal in all groups. During stress, healthy volunteers achieve global hyperemia with no perfusion defects. In asymmetrical septal hypertrophy hypertrophic cardiomyopathy (ASH HCM), while there is hyperemia, there are often dense perfusion defects, mainly in the hypertrophied areas. In apical hypertrophic cardiomyopathy (ApHCM), perfusion defects are seen circumferentially in the apical subendocardium, here with stress flow below rest flow.

Figure 3.

Two-chamber long-axis stress perfusion maps in all cases of overt and relative apical hypertrophic cardiomyopathy (ApHCM). The extent of perfusion defects varies, as does the presence of below rest adenosine flow. There were no perfusion defects in healthy volunteer controls.

Figure 4.

The importance of apical coverage. The conventional 3 short-axis approaches here would have missed the apical perfusion seen on the long-axis view, as found in 10% of our cohort.