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Doppler color flow mapping studies of jet formation and spatial orientation in obstructive hypertrophic
B D Hoit1, E Penonen, N Dalton
1Division of Cardiology, Veterans Administration Medical Center, San Diego, Calif.
Insights
This study reveals that hypertrophic cardiomyopathy (HCM) causes abnormal left ventricular outflow tract (LVOT) flow angles and jet narrowing, leading to obstruction. These findings clarify the mechanism of LVOT obstruction and systolic anterior motion in HCM patients.
Area of Science:
- Cardiology
- Medical Imaging
- Fluid Dynamics
Background:
- Left ventricular outflow tract (LVOT) obstruction and systolic anterior motion (SAM) of the mitral valve are key features of hypertrophic cardiomyopathy (HCM).
- The precise mechanisms and relationship between LVOT geometry and these phenomena require further elucidation.
Purpose of the Study:
- To investigate the characteristics of LVOT flow in patients with HCM.
- To compare these flow patterns with those in patients with isolated valvular aortic stenosis (AS) and healthy volunteers.
- To clarify the relationship between LVOT obstruction, SAM, and left ventricular geometry.
Main Methods:
- Two-dimensional Doppler flow mapping was used to study LVOT flow in 20 HCM patients, 10 AS patients, and 10 healthy volunteers.
- Continuous wave Doppler measured peak jet velocity as an indicator of obstruction severity.
- Color M-mode assessed flow acceleration proximal to SAM.
Main Results:
- HCM patients exhibited significant posterolateral LVOT jets (mean angle 111.4°), with angles correlating strongly with obstruction severity (r = -0.81).
- Jet narrowing proximal to SAM was 42% in HCM, significantly greater than in AS (8%, p < 0.05).
- Evidence of flow acceleration and obstruction was observed proximal to the mitral valve SAM in HCM.
Conclusions:
- Abnormal LVOT flow dynamics, characterized by specific jet angles and significant narrowing, are central to obstruction in HCM.
- These findings provide mechanistic insights into LVOT obstruction and SAM in HCM.
- Doppler flow mapping is effective in demonstrating these hemodynamic abnormalities.
Abstract:
To help clarify the mechanism of outflow tract obstruction and systolic anterior motion of the anterior leaflet of the mitral valve and their relation to the geometry of the left ventricle, we studied left ventricular outflow tract flow in 20 patients with hypertrophic cardiomyopathy (HCM) using two-dimensional Doppler flow mapping. We compared our results with outflow tract flow in 10 patients with isolated valvular aortic stenosis, (AS) and with those in 10 healthy volunteers. In HCM, a 94- to 145-degree angle (mean 111.4 +/- 11.9 degrees) developed between the direction of left ventricular outflow tract flow acceleration and aortic valve outflow, resulting in posterolaterally directed left ventricular outflow jets. The angle of the outflow jet and the peak velocity of the jet measured with continuous wave Doppler (as an indicator of the severity of obstruction) correlated well (r = -0.81, SEE = 7.8 degrees). Jet narrowing during ejection measured just proximal to the point of systolic anterior motion was 42 +/- 11% in HCM and was weakly correlated with peak jet velocity (r = 0.61, SEE = 8.9 degrees). Aliasing of left ventricular outflow occurred proximal to systolic anterior motion of the mitral valve, and color M-mode demonstrated temporal and spatial flow acceleration proximal to systolic anterior motion, providing evidence for obstruction at that site. In AS, left ventricular outflow tract jets were more parallel to the axis of aortic outflow (129 to 153 degree, 138.4 +/- 8.1 degrees). Jet narrowing was only 8 +/- 5% compared to HCM (both p less than 0.05), and flow acceleration occurred proximal to the stenotic valve.(ABSTRACT TRUNCATED AT 250 WORDS)