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Dynamic Left Ventricular Outflow Obstruction in Hypertrophic Cardiomyopathy Revisited: Significance, Pathogenesis,
1St. Luke's-Roosevelt Hospital Center, New York, New York.
Insights
Systolic anterior motion of the mitral valve causes dynamic left ventricular outflow obstruction in hypertrophic cardiomyopathy. Negative inotropic drugs and surgery are effective treatments for this obstruction.
Area of Science:
- Cardiology
- Medical Imaging
- Physiology
Background:
- Dynamic left ventricular outflow obstruction is a common complication of hypertrophic cardiomyopathy.
- Systolic anterior motion (SAM) of the mitral valve and mitral-septal contact are primary mechanisms causing this obstruction.
- Established evidence from cardiac catheterization and echocardiography confirms the occurrence of true obstruction.
Purpose of the Study:
- To elucidate the mechanisms of dynamic left ventricular outflow obstruction in hypertrophic cardiomyopathy.
- To review the established evidence and recent findings regarding obstruction.
- To discuss current and emerging treatment strategies for symptomatic patients.
Main Methods:
- Review of cardiac catheterization data.
- Analysis of echocardiographic evidence, including flow dynamics and mitral valve motion.
- Evaluation of treatment outcomes for medications and surgical interventions.
Main Results:
- Systolic anterior motion of the mitral valve is initiated by flow drag, leading to mitral-septal contact.
- Obstruction intensifies after initial contact due to pressure gradients.
- A mid-systolic decline in left ventricular systolic ejection velocity is a hallmark of obstruction.
Conclusions:
- Negative inotropic drugs effectively reduce SAM and obstruction by decreasing early ejection acceleration and the associated pushing force.
- Patients unresponsive to medication often benefit from surgical intervention.
- Novel interventions like dual-chamber pacing and percutaneous transluminal septal myocardial ablation are under investigation for obstruction relief.
Abstract:
Systolic anterior motion of the mitral valve and mitral-septal contact is the usual cause of dynamic left ventricular outflow obstruction in hypertrophic cardiomyopathy. That true obstruction actually occurs is now established based on cardiac catheterization and echocardiographic evidence. A mid-systolic drop in left ventricular systolic ejection velocity because of obstruction has been demonstrated recently. Echocardiographic data indicate that systolic anterior motion of the mitral valve is initiated by flow drag; the mitral valve is swept toward the septum by the pushing force of flow. After mitral-septal contact, obstruction begets further obstruction as the pressure gradient pushes the mitral valve into the septum. Most symptomatic patients with obstruction can be treated successfully with negatively inotropic drugs. These medications reduce systolic anterior motion and obstruction by decreasing early left ventricular ejection acceleration, decreasing the early systolic pushing force on the protruding mitral leaflet. Patients who do not improve on medication generally benefit from surgery. Newer interventions to relieve obstruction, such as dual-chamber pacing and percutaneous transluminal septal myocardial ablation are under active investigation.