Demonstration of left ventricular outflow tract eccentricity by 64-slice multi-detector CT

Area of Science:

• Cardiovascular imaging
• Cardiac geometry and hemodynamics

Background:

• Advanced 3D imaging offers novel insights into cardiac shape and geometry.
• Traditional formulas like the continuity equation (CE) assume a round left ventricular outflow tract (LVOT), potentially impacting accuracy.
• Small variations in LVOT diameter significantly influence calculated aortic valve area (AVA).

Purpose of the Study:

• To assess the shape of the LVOT using 64-slice Multi-detector CT (MDCT) planimetry.
• To compare diameter-derived LVOT area (ALVOTdiam) with direct planimetry (ALVOTplan) and an ellipsoid model (ALVOTellip).
• To evaluate the impact of LVOT shape assumptions on AVA calculations.

Main Methods:

• 30 patients underwent 64-slice MDCT.
• LVOT area was calculated using diameter (ALVOTdiam) and direct planimetry (ALVOTplan).
• An ellipsoid LVOT area (ALVOTellip) was derived, and eccentricity index (EI) was computed.

Main Results:

• ALVOTdiam consistently underestimated LVOT area compared to ALVOTplan (3.7 cm² vs. 4.1 cm²).
• The LVOT demonstrated a median eccentricity index of 0.18, indicating an elliptical shape.
• ALVOTellip showed high correlation with ALVOTplan (r=0.96), superior to ALVOTdiam (r=0.87).

Conclusions:

• MDCT confirms the LVOT is predominantly elliptical.
• The CE's assumption of a round LVOT leads to underestimation of LVOT area and potentially AVA.
• LVOT planimetry with 3D imaging (echocardiography, MRI, MDCT) offers more precise AVA determination.