Coronary microvascular dysfunction and prognosis in hypertrophic cardiomyopathy

Area of Science:

• Cardiology
• Cardiovascular Imaging
• Physiology

Background:

• Microvascular dysfunction is a known feature of hypertrophic cardiomyopathy (HCM), characterized by inadequate myocardial blood flow response to vasodilators.
• The long-term prognostic implications of this dysfunction in HCM patients remain largely unknown.

Purpose of the Study:

• To prospectively evaluate the long-term effect of microvascular dysfunction on prognosis in patients with hypertrophic cardiomyopathy.
• To assess the relationship between quantitative myocardial blood flow and clinical outcomes.

Main Methods:

• Fifty-one HCM patients (NYHA class I-II) underwent quantitative myocardial blood flow assessment using PET and N-13 ammonia at baseline and after dipyridamole infusion.
• Patients were followed for a mean of 8.1 years, and divided into three groups based on myocardial blood flow values.
• Twelve subjects with atypical chest pain served as controls.

Main Results:

• HCM patients exhibited severely blunted myocardial blood flow response to dipyridamole compared to controls (1.50 vs. 2.71 ml/min/g, P<0.001).
• Thirty-one percent of patients experienced an unfavorable outcome (cardiovascular death, NYHA class III-IV progression, or ICD implantation).
• Reduced blood flow was strongly associated with unfavorable outcomes; patients in the lowest flow group had a 9.6-fold increased hazard for cardiovascular death and 20.1-fold for unfavorable outcomes.

Conclusions:

• The degree of microvascular dysfunction is a potent, independent predictor of clinical deterioration and mortality in hypertrophic cardiomyopathy.
• Severe microvascular dysfunction can be present even in initially asymptomatic or mildly symptomatic HCM patients and may precede clinical decline by years.