Microvascular Dysfunction, Myocardial Ischemia, and Progression to Heart Failure in Patients with Hypertrophic Cardiomyopathy

Abstract

Microvascular dysfunction can be demonstrated in most patients with hypertrophic cardiomyopathy (HCM), both in the hypertrophied and nonhypertrophied myocardial walls, mostly due to intimal and medial hyperplasia of the intramural coronary arteries and subsequent lumen reduction. As a consequence, regional myocardial ischemia may be triggered by exercise, increased heart rate, or arrhythmias, in areas which are unable to increase myocardial blood flow. In patients with HCM, microvascular dysfunction leading to severe myocardial hypoperfusion during maximal hyperemia represents a strong predictor of unfavorable outcome, left ventricular remodeling with progressive wall thinning, left ventricular dysfunction, and heart failure. Accurate quantitative assessment of microvascular dysfunction and myocardial ischemia is not easily feasible in clinical practice. Although signs of inducible myocardial ischemia may be detected by electrocardiogram, echocardiography, or myocardial scintigraphy, the vasodilator response to dipyridamole by positron emission tomography is considered the method of choice for the assessment of maximal regional and global flow. Cardiac magnetic resonance provides further information, by late gadolinium enhancement (LGE), which may show areas where replacement fibrosis has occurred following microvascular ischemia and focal necrosis. LGE areas colocalize with severe regional microvascular dysfunction, are associated with increased prevalence of ventricular arrhythmias, and show more extensive distribution in the late stages of the disease, when heart failure is the dominant feature. The present review aims to provide a concise overview of the available evidence of microvascular dysfunction and ischemia eventually leading to disease progression and heart failure in HCM patients.

Differentiating physiology from pathology in elite athletes. Left ventricular hypertrophy versus hypertrophic cardiomyopathy

“…Diffuse microvascular dysfunction in the heart, in the absence of changes in epicardial coronary arteries, is an effect of pathological remodelling in small intramural vessels, with thickening of the arteriole wall, hyperplasia of smooth muscles, and disorganisation of elastic fibres [32]. A result of the remodelling process is a narrowing of the luminal diameter, most often irregular and impaired vasodilator reserve [33].…”

“…A result of the remodelling process is a narrowing of the luminal diameter, most often irregular and impaired vasodilator reserve [33]. Therefore, microvascular dysfunction, along with compression forces, resulting from the hypertrophy may be a cause of ischaemia in HCM [32].…”

Apical hypertrophic cardiomyopathy, a review of presentation, pathophysiology, diagnosis and natural course of the disease

“…(Bangladesh Heart Journal 2016; 31 (1) : [29][30][31][32][33][34][35][36] Apical hypertrophic cardiomyopathy mimics and the role of other imaging modalities As mentioned a TTE although often the first line imaging modality can be non-diagnostic for AHCM especially if the apex is not fully visualized. Furthermore apical thrombus, Loefflers endocarditis, LV aneurysm, LV non compaction, and endomyocardial fibrosis may give a similar echocardiographic appearance on TTE to AHCM.…”

“…Mortality and morbidity outcomes from these studies are summarized in Table 2 and Table 3. 3,4,5,16,36,37,[40][41][42][43] Most studies did not report MI unrelated to pre-existing coronary artery disease.…”

Does relief of outflow tract obstruction in patients with hypertrophic cardiomyopathy improve long-term survival? Implications for lowering the threshold for surgical myectomy and alcohol septal ablation

“…Could it be that obstruction exacerbates microvascular ischemia that is a necessary trigger of the underlying arrhythmic substrate, and thus a more quiescent state ensues after relief of obstruction? Certainly, data does support that ischemia is present in patients with HCM, even without epicardial coronary disease, and that such ischemia is a potent predictor of both progression and death (15). Alternatively, it could be that the overall propensity for arrhythmia is reduced with regression of cellular hypertrophy, or that a more normally-functioning heart can simply tolerate ventricular arrhythmias better.…”