[Echocardiographic assessment of left atrial volume and emptying in hypertrophic cardiomyopathy]

Left ventricular diastolic dysfunction plays an important role in the pathogenesis of symptoms in patients with hypertrophic cardiomyopathy (HCM). Theoretically abnormal LV filling should lead to left atrium (LA) enlargement and abnormal emptying. Our study was performed in 27 pts with hypertrophic cardiomyopathy (mean ventricular septum thickness 2.4 +/- 0.73 cm, mean posterior wall thickness 1.23 +/- 0.42 cm and mean LV wall thickness measured at 10 segments 1.93 +/- 0.37 cm) and 38 healthy volunteers. Transmitral Doppler flow parameters (Emax, Amax, t decE, Emax/Amax) did not differ in both groups. We used 2D echocardiographic automatic borderline detection method to assess the following LA volumes during its emptying: maximal volume (LAVmax), volumes at the end of rapid emptying (LAV-RE), before atrial contraction--P wave on ECG (LAV-P) and minimal LA volume after atrial contraction (LAVmin). We also calculated total LA emptying fraction (%LAEF), absolute volume changes during LA early emptying (delta LAV-RE) and atrial contraction (delta LAV-AC) and their ratio (delta LAV-RE/delta LAV-AC). 11 pts had mitral regurgitation. The mitral regurgitation fraction was calculated as the ratio of the area of mitral regurgitation to LA area.

Significantly larger LAVmax (75.8 +/- 28.0 vs 60.7 +/- 18.1 ml, p<0.01), LAV-RE (50.4 +/- 21.4 vs 35.3 +/- 13.8 ml, p<0.005), LAV-P (50.7 +/- 20.5 vs 38.4 +/- 13.8 ml, p<0.01) and LAVmin (33.0 +/- 15.1 vs 26.3 +/- 11.7 ml, p<0.05) were found in HCM compared to C. The total LA emptying fraction %LAEF (58.0 +/- 11.4 vs 57.4 +/- 12.1%, NS), DLAV-RE (27.3 +/- 12.6 vs 25.3 +/- 11.0 ml, NS), and ratio delta LAV-RE/DLAV-AC (1.94 +/- 1.22 vs 2.38 +/- 1.10, NS) were similar both groups and active emptying delta LAV-AC (17.6 +/- 9.7 vs 12.1 +/- 5.3 ml, p<0.005) was significantly larger in HCM. The regurgitation fraction observed in HCM was 2.7-31.1%. Statistically significant correlation between LA total emptying fraction (%LAEF) and mitral regurgitation fraction (r=-0.47, p<0.05) and no relations between LA size and function parameters and LV hypertrophy parameters were found in HCM.

LV hypertrophy in hypertrophic cardiomyopathy leads to LA enlargement and changes in its emptying. We found larger the following LA volumes: maximal volume, volume after early emptying, before atrial contraction and minimal volume and greater LA volume change during active emptying. Total LA emptying fraction, volume change during early/passive emptying and passive/active emptying volumes ratio were similar in both groups. No correlation existed between the degree of LV hypertrophy and LA volume and emptying parameters. We observed negative relation between mitral regurgitation fraction and LA total emptying fraction, but because of small group of pts with mitral regurgitation, further studies are needed.