Abstract 14335: Abnormal Left Atrial Conduit Function in Obstructive Hypertrophic Cardiomyopathy is Mediated Through Elevated Left Ventricular Filling Pressure

Abstract

Introduction: Elevated left ventricular outflow tract (LVOT) gradient occurs in a majority of HCM patients and is associated with diastolic dysfunction, heart failure, atrial fibrillation and death. These adverse outcomes are also commonly associated with Left atrial (LA) dysfunction. Yet, the nature and extent of the relationship between LVOT gradient and LA function remains ill-understood. Methods: HCM patients were classified as obstructive (rest gradient ≥ 30 mmHg), labile (rest gradient < 30 mmHg, provoked gradient ≥ 30 mmHg) and non-obstructive (rest and provoked gradient < 30 mmHg). In addition to conventional analysis, LA reservoir, conduit and contractile strain were measured (TomTec Imaging Systems). Results: Of 135 patients, 34 (44% male) were obstructive, 36 (75% male) labile and 65 (63% male) non-obstructive HCM. Large LA volume index and elevated E/e’ was associated with elevated LVOT gradient at rest (r 0.17; p 0.04 and r 0.40; p<0.001, respectively) and with Valsalva (r 0.19; p 0.03 and r 0.33; p<0.001, respectively). Low LV strain was associated with elevated LVOT gradient with exercise (r -0.22, p 0.04). LA conduit strain (but not reservoir or contractile strain) was lower in patients with obstructive HCM compared to patients with non-obstructive HCM (13.1 ± 5.4 vs 11.0 ± 3.9%, p = 0.03, Figure 1). There was no significant difference in all LA strain parameters across all the other HCM types. Conclusions: Measures of elevated LV filling pressure (large LA volume index, elevated E/e’ and low LV strain) were associated with elevated LVOT gradient. LA conduit strain was lower in obstructive compared to non-obstructive HCM. Our data suggest that elevated LVOT gradient is associated with abnormal LA conduit function most likely mediated via elevated LV filling pressure.