ABSTRACT
Hypertrophic cardiomyopathy (HCM) is characterized by extreme clinical heterogeneity, ranging from sudden cardiac death to long-term disease progression and heart failure-related complications. Myocardial ischemia, occurring at the microvascular level, is a major determinant of clinical expression and outcome. Accordingly, the severity of this microvascular dysfunction has been shown to represent an early and powerful predictor of unfavorable outcome in HCM. The assessment of microvascular function in vivo is technically challenging, although critical to a truly comprehensive evaluation and risk stratification of HCM patients. Available technologies include positron emission tomography and cardiac magnetic resonance (CMR). Studies of regional myocardial blood flow using positron emission tomography have demonstrated that the vasodilator response to dipyridamole is impaired in most HCM patients, not only in the hypertrophied ventricular septum but also in the less hypertrophied or non-thickened left ventricular free wall. CMR also allows measurement of myocardial flow, although the technique is currently time-consuming and largely limited to research situations. CMR provides further insight into the effects of ischemia in HCM patients, by visualizing the distribution and extent of fibrosis at the intramyocardial level. Late gadolinium enhancement (LGE) is a potential predictor of risk in HCM patients, and is believed to largely reflect replacement fibrosis resulting from recurrent microvascular ischemia. LGE is associated with increased prevalence of ventricular arrhythmias, and associated with microvascular dysfunction. The present review is to provide a concise overview for the available evidence of microvascular ischemia and its consequences in HCM.
Subject(s)
Humans , Cardiomyopathy, Hypertrophic , Diagnostic Imaging , Pathology , Magnetic Resonance Imaging , Myocardium , Pathology , Positron-Emission TomographyABSTRACT
Atrial fibrillation (AF) is the most common sustained arrhythmia in patients with hypertrophic cardiomyopathy (HCM), and represents an important complication in the clinical course of the disease, with adverse consequences on functional status and outcome. Studies on community-based HCM patient populations have shown that AF is associated with long-term clinical deterioration, cardioembolic stroke and increased cardiovascular mortality due to heart failure and stroke. Moreover, acute onset of AF may cause severe hemodynamic impairment and represent a trigger of potentially lethal ventricular arrhythmias. However, the consequences of AF on the long-term prognosis of HCM patients are not uniformly unfavorable, and may be compatible with an uneventful course, when properly managed. Management of AF in HCM is challenging, particularly when onset occurs at a young age. Both paroxysmal and permanent AF represent clear indications for oral anticoagulation. In most patients, maintenance of sinus rhythm is highly desirable but made difficult by the limited long-term efficacy and potentially hazardous side effects of available pharmacological options. In selected patients with HCM and severely symptomatic AF, radiofrequency catheter ablation may represent an effective therapeutic alternative, improving functional status, and reducing or postponing the need for antiarrhythmic drugs. In patients with persistent AF, in whom maintenance of sinus rhythm is not feasible, adequate ventricular rate control should be pursued aggressively by atrio-ventricular node blocking agents.