Transesophageal Doppler echocardiography in obstructive hypertrophic cardiomyopathy: clarification of pathophysiology and importance in intraoperative decision making
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L E Grigg1, E D Wigle, W G Williams
1Division of Cardiology, Toronto General Hospital, Ontario, Canada.
Insights
Transesophageal echocardiography aids in understanding obstructive hypertrophic cardiomyopathy by revealing abnormal mitral leaflet motion and coaptation. It is crucial for guiding surgical myectomy and assessing outcomes, leading to improved left ventricular outflow tract function.
Area of Science:
- Cardiology
- Echocardiography
- Cardiac Surgery
Background:
- Obstructive hypertrophic cardiomyopathy (HCM) involves complex left ventricular outflow tract (LVOT) dynamics.
- Understanding the pathophysiology of LVOT obstruction is key for effective treatment.
- Mitral valve abnormalities contribute significantly to HCM obstruction.
Purpose of the Study:
- To elucidate the pathophysiology of LVOT obstruction in HCM.
- To evaluate the utility of intraoperative transesophageal Doppler echocardiography (TDE) in guiding ventriculomyectomy.
- To correlate echocardiographic findings with surgical outcomes.
Main Methods:
- 32 patients undergoing ventriculomyectomy for obstructive HCM were studied.
- Preoperative and intraoperative TDE was used to assess LVOT dimensions, septal width, and mitral valve dynamics.
- Comparison with 10 healthy control subjects.
Main Results:
- Patients with obstructive HCM exhibited longer mitral leaflets and abnormal coaptation points compared to controls.
- Systolic anterior motion (SAM) of the anterior mitral leaflet was observed, leading to LVOT obstruction and mitral regurgitation.
- TDE effectively guided surgical resection, and successful myectomy resulted in reduced LVOT obstruction, resolved SAM, and decreased mitral regurgitation.
Conclusions:
- Abnormal mitral leaflet morphology and SAM are critical components of obstructive HCM pathophysiology.
- Intraoperative TDE is invaluable for surgical planning, decision-making, and outcome assessment in ventriculomyectomy for HCM.
- Routine use of TDE is recommended for patients undergoing surgical myectomy for obstructive HCM.
Abstract:
To better understand the pathophysiology of obstruction of left ventricular outflow in hypertrophic cardiomyopathy and to determine the value of intraoperative transesophageal Doppler echocardiography in decision making, 32 consecutive patients undergoing ventriculomyectomy were assessed. The mean preoperative left ventricular outflow gradient was 83 +/- 39 mm Hg and the mean basal septal width was 24 +/- 6 mm. Compared with transesophageal findings in 10 normal control subjects, the mitral leaflets were longer and the coaptation point was abnormal in the patients with obstructive hypertrophic cardiomyopathy (anterior and posterior leaflet lengths in the patients were 31 +/- 4 vs. 22 +/- 3 mm in the control group [p less than 0.00001] and 20 +/- 2 vs. 15 +/- 3 mm in the control group [p less than 0.00001]). The coaptation point in the patient group was in the body of the leaflets at a mean of 9 +/- 2 mm from the anterior leaflet tip, whereas it was at or within 3 mm of the leaflet tip in the normal group. During early systole, the distal third to half of the anterior mitral leaflet angled sharply anteriorly and superiorly (systolic anterior motion), resulting in leaflet-septal contact and incomplete mitral leaflet coaptation in mid-systole. This caused the formation of a funnel, composed of the distal parts of both leaflets, that allowed a jet of posteriorly directed mitral regurgitation to occur in mid- and late systole. The sequence of events in systole was eject/obstruct/leak. Transesophageal echocardiography was also helpful in planning the extent of the resection, assessing the immediate result and excluding important complications. In successful cases, the post-myectomy study showed 1) a dramatic thinning of the septum, with widening of the left ventricular outflow tract to a width similar to that in the normal subjects, 2) resolution of systolic anterior motion and the left ventricular outflow tract color mosaic, and marked reduction or abolition of mitral regurgitation despite persistence of abnormal mitral leaflet length and an abnormal mitral leaflet coaptation point. The routine use of transesophageal echocardiography in patients undergoing surgical myectomy for the treatment of obstructive hypertrophic cardiomyopathy is recommended.