Effect of Left Ventricular Outflow Tract Obstruction on Left Atrial Mechanics in Hypertrophic Cardiomyopathy

Abstract

Left atrial (LA) volumes are known to be increased in hypertrophic cardiomyopathy (HCM) and are a predictor of adverse outcome. In addition, LA function is impaired and is presumed to be due to left ventricular (LV) diastolic dysfunction as a result of hypertrophy and myocardial fibrosis. In the current study, we assess the incremental effect of outflow tract obstruction (and concomitant mitral regurgitation) on LA function as assessed by LA strain. Patients with HCM (50 obstructive, 50 nonobstructive) were compared to 50 normal controls. A subset of obstructive patients who had undergone septal myectomy was also studied. Utilising feature-tracking software applied to cardiovascular magnetic resonance images, LA volumes and functional parameters were calculated. LA volumes were significantly elevated and LA ejection fraction and strain were significantly reduced in patients with HCM compared with controls and were significantly more affected in patients with obstruction. LA volumes and function were significantly improved after septal myectomy. LVOT obstruction and mitral regurgitation appear to further impair LA mechanics. Septal myectomy results in a significant reduction in LA volumes, paralleled by an improvement in function.

Left atrial remodeling postseptal myectomy for severe obstructive hypertrophic cardiomyopathy: Analysis by two‐dimensional speckle‐tracking echocardiography

“…Our findings, consistent with those of previous studies, have shown that septal myectomy in patients with HCM results in a decrease in all LA volumes. 7,8,11,12 We have shown that following surgical myectomy LA active myectomy was similar to patients with no intra-ventricular conduction abnormalities 38 . Indeed, LVOT gradient has been shown to be associated with E/e′ lateral ratio and tissue Doppler of the mitral annulus early diastolic velocity.…”

“…Several studies have documented increased LA volumes in HCM patients. 7,8,12 The LA appears to initially increase its volume by stretching to compensate for the increased loading conditions resulting from significant LVOTO, mitral regurgitation and diastolic dysfunction while maintaining normal compliance. It is plausible that as LA enlargement increases beyond the Frank-Starling relationship, it results in a significant reduction in the atrial booster pump function, which again results in reduced LA emptying fraction.…”

“…1 Septal myectomy relieves the left ventricular (LV) outflow tract obstruction (LVOTO) and is associated with excellent long-term outcomes. [7][8][9][10][11][12] Two-dimensional (2D) speckle-tracking echocardiography (2DSTE) allows measurement of phasic changes in LA volumes and strain. One would expect improvement of these parameters following elimination of the LVOTO by surgical myectomy.…”

“…However, data regarding diastolic and LA function post myectomy are scarce and inconsistent. [7][8][9][10][11][12] Two-dimensional (2D) speckle-tracking echocardiography (2DSTE) allows measurement of phasic changes in LA volumes and strain. 13,14 Furthermore, 2DSTE-derived LA functional parameters have been strongly associated with the degree of diastolic dysfunction.…”

Left ventricular outflow tract obstruction in ICU patients

“…LVOTO and mitral regurgitation further impair left atrium mechanics [11]. In HCM, the left atrium is often enlarged and its size provides important prognostic information [12].…”