Left Atrial Strain is an Independent Determinant of Exercise Capacity in Hypertrophic Cardiomyopathy

Aims: The objective was to evaluate the potential contribution of left atrial (LA) function to reduced exercise capacity in patients with hypertrophic cardiomyopathy (HCM).Methods and results: Using a case-control design we randomly selected 95 patients with confirmed HCM based on guidelines criteria and without permanent atrial arrhythmia who underwent a treadmill exercise test. We measured echo-based left ventricular (LV) and LA morphology and function including mechanics using 2D speckle tracking. Preserved exercise capacity was defined as the 25 th percentile of metabolic equivalents (METs) or > 7 METs. Of 95 HCM patients, 36 had reduced exercise capacity (£7 METs) and 59 had preserved exercise capacity (>7 METs). Reduced exercise capacity patients were more likely to be older, female, had higher BMI, and more advanced heart failure symptoms. They also had a higher E/e’ ratio and lower LA reservoir and conduit strain but similar left ventricular outflow tract (LVOT) pressure gradients. By univariate analysis, LA reservoir and conduit strain, age, gender, BMI, NYHA class, and E/e’ correlated with METs. In multivariate analysis, LA conduit strain independently determined METs after adjusting for age, gender, BMI, NYHA and E/e’ (standardized coefficients 0.17, P=0.04). This relationship was primarily noted in non- and labile-obstructive but not in obstructive HCM. History of atrial fibrillation did not impact the association of LA strain with exercise capacity.Conclusion : Even after adjusting for LVOT gradients and diastolic function, reduced LA conduit strain is an independent determinant of exercise tolerance in HCM.