Assessment of left ventricular outflow tract dynamics during the cardiac cycle by three- dimensional echocardiography

Abstract

Background
Anatomical and anatomo-functional disorders of the left ventricular outflow tract (LVOT) are subject of numerous studies. However, LVOT normal dynamic behavior, especially in procedures involving this area is also relevant, and may be evaluated with new three-dimensional imaging methods.

Objective
The aim of this study was to assess LVOT dynamics during the cardiac cycle with three-dimensional transesophageal echocardiography (TEE).

Methods

Forty two patients referred for transesophageal echocardiography (TEE) were prospectively included. All TEE studies were performed with a three-dimensional transesophageal probe. For complete volume images, 4 gated beats were acquired for off-line analysis. The cardiac cycle was divided in proto-systole (S1), mid-systole (S2) and tele-systole (S3) and proto-diastole (D1), mid-diastole (D2) and tele-diastole (D3). The LVOT area was measured by planimetry of the short axis, through orthogonal sections to the long axis of the LVOT in each phase.
Results

Mean age was 67±10 years, and 63% of the patients were male. The LVOT area (cm2) in the different phases of the cardiac cycle was: S1: 4.44±1.02; S2: 4.15±0.91; S3: 3.9±0.89;D1: 3.76±0.98; D2: 3.89±1.04; D3: 4.34±1.11. Maximum area was observed in S1, corresponding to the closed position of the anterior leaflet of the mitral valve (AL) and reduced motion of the interventricular septum (IVS) towards LVOT; minimum area was obtained in D1 consistent with a certain persistence of IVS in the LVOT and maximal AL opening occupying part of the LVOT. Total area reduction was 15±11% (p<0.0001), changing the LVOT from a partially elliptical or circular shape (systole) to a markedly elliptical or semilunar one (diastole).

Conclusion

The LVOT changes its area and shape during the cardiac cycle, depending basically on the movement of the IVS (during systole) and mitral valve opening (during diastole).