Impact of Septal Reduction on Left Atrial Size and Diastole in Hypertrophic Cardiomyopathy.BACKGROUND AND AIMS
 Both myectomy and alcohol septal ablation (ASA) can substantially reduce left ventricular (LV) outflow obstruction, relieve symptoms, and improve outcomes in hypertrophic cardiomyopathy (HCM).  It is unclear whether septal reduction decreases left atrial (LA) size and improves diastolic function.  The aim of this study was to analyze the consequences of septal reduction on LA size and diastolic function in a cohort of patients with HCM.


 Forty patients (mean age: 50 ± 14, male sex 64%) with HCM who underwent septal reduction (myectomy or alcohol septal ablation) were studied.  Retrospective analyses of echocardiograms preprocedure, postprocedure, and at 1 year of follow-up were performed.


 Thirty-one patients had septal myectomy and 9 ASA.  The degree of reduction in rest peak LV outflow tract gradient was significant (57 ± 32 vs. 23 ± 20 mmHg at 1 year, P < 0.001).  Maximal interventricular septal thickness decreased from 22 ± 6 mm preprocedure to 19 ± 4 mm postprocedure (P < 0.001); moderate-to-severe mitral regurgitation (MR) was initially present in 34% of the sample and only 2% after the procedure.  Average LA volume index (LAVI) decreased from 63 ± 20 to 55 ± 20 mL/m(2) at the 1-year follow-up (P < 0.001).  We did not observe a significant improvement in diastolic function at Doppler (E/A 1.2 ± 0.4 vs. 1.1 ± 0.5, P = 0.07; E' 7.6 ± 3.6 vs. 6.9 ± 3.0, P = 0.4) pre- and postprocedure, respectively).  At 1 year, only 5% of the patients were severely symptomatic (NYHA III).  On multivariate analysis, a significant change in the LVOT gradient during stress (Δ gradient ≥30 mmHg) was the only variable independently associated with LAVI reverse remodeling >10 mL/m(2) [OR = 6.4 (CI 95% 1.12-36.44), P = 0.04].


 CONCLUSIONS
 Septal reduction is effective in the relief of LV obstruction and symptoms in patients with HCM.  The hemodynamic changes result in a significant LA reverse remodeling, but not in an improvement of diastolic function in these patients.
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