Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

1. Impaired left anterior descending (LAD) artery coronary flow velocity reserve (CFVR) acquired by transthoracic Doppler echocardiography (TDE) (≤2) was a strong, independent predictor of adverse cardiac outcome in patients with HCM.

Evidence Rating Level: 2 (Good)

Hypertrophic cardiomyopathy (HCM), a disease that causes thickening of heart muscle, is the most common inherited cardiac disease. To date, there are few clinical and echocardiographic parameters for predicting certain HCM-related cardiovascular events, such as progressive deterioration of left ventricular (LV) systolic function with heart failure development or an ischemic stroke. Previous studies have found that microvascular ischemia may be one such parameter. However, assessment of microvascular ischemia in HCM patients remains challenging. Coronary flow velocity reserve (CFVR) acquired by transthoracic Doppler echocardiography (TDE) has proved to be a non-invasive and inexpensive tool for functional evaluation of microcirculation in the absence of epicardial stenosis. The long-term predictive value of TDE CFVR on clinical outcome has not been investigated in HCM patients. Consequently, this prospective study assessed long-term prognostic value of CFVR on clinical outcome in patients with HCM. A total of 150 patients with HCM (68 men, 82 women; mean age 48±15 years) were recruited between January 2008 and July 2017. Of these, 41 patients had significant left ventricular outflow tract gradient (LVOTG) and 109 patients had no obstruction. Clinical characteristics and echocardiographic and CFVR findings for both left anterior descending (LAD) and posterior descending (PD) arteries were assessed in all participants. Patients were stratified into 2 subgroups depending on CFVR LAD value: Group 1 (CFVR LAD>2, [N=87]) and Group 2 (CFVR LAD≤2, [N=63]). The primary outcome was a composite of HCM-related death, heart failure requiring hospitalization, sustained ventricular tachycardia, and ischemic stroke. During a median follow-up of 88 months, 8/87 (9.2%) patients in Group 1 and 33/63 (52.4%) patients in Group 2 (P<0.001 vs. Group 1) had adverse cardiac events. Patients with preserved CFVR LAD had significantly higher cumulative event‐free survival rate compared to patients with impaired CFVR LAD (96.4% and 90.9% versus 66.9% and 40.0%, at 5 and 8 years, respectively: log‐rank 37.2, P<0.001). CFVR PD was not significantly associated with outcome. The authors concluded that impaired CFVR LAD (≤2) is a strong, independent predictor of adverse cardiac outcome in patients with HCM. Identifying patients with impaired CFVR LAD may help improve risk stratification of HCM patients.

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