Mitral valve abnormalities in hypertrophic cardiomyopathy: echocardiographic features and surgical outcomes

The mitral valve in hypertrophic cardiomyopathy: old versus new concepts

Elongation and pathological thickening of the mitral valve (MV) is commonly seen in hypertrophic cardiomyopathy (HCM), and its pathogenic basis is poorly understood. Associated features include mal-positioning of the papillary muscles and MV, as well as systolic anterior motion (SAM) of the MV leaflets, which can worsen the turbulence and dynamic left ventricular outflow tract (LVOT) gradient. Coaptation of the MV leaflets depends on both anterior and posterior leaflet length and position, and failure of either to optimally adapt in this setting can result in mitral regurgitation or worsened LVOT obstruction. The cause of MV enlargement in HCM is not currently understood, and several different hypotheses may be relevant. The lack of correlation between MV size and the severity of left ventricular hypertrophy, as well as the early findings in genetically predisposed individuals with sarcomere mutations, suggest that it may be an intrinsic aspect of HCM in certain individuals. Other evidence points to a reactive process in the setting of excess production of paracrine growth factors in diseased myocardium that may influence valve overgrowth. Improved understanding of the responsible adaptive mechanisms will pave the way for studies targeted on the prevention and treatment of MV disease in HCM.

Interventional treatments for hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disorder. This autosomal dominant condition is defined by left ventricular hypertrophy and associated with functional limitation and premature death. In fact, many individuals are asymptomatic and the annual mortality in most modern series is 1% or less. However, severe symptoms may develop at any age, and the risk of premature death from arrhythmia, stroke, and progressive systolic impairment may complicate asymptomatic disease. The clinical management of patients with HCM therefore encompasses (1) genetic counseling including discussion of indications for genetic testing and cascade family screening, (2) assessment of prognostic risk from ventricular arrhythmia, stroke, and heart failure, and (3) symptom management. This article describes the interventional treatments in the management of severe symptoms associated with left ventricular outflow tract obstruction (LVOTO).

Alcohol Septal Ablation for the Treatment of Hypertrophic Obstructive Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an inherited myocardial disorder characterised by left ventricular hypertrophy. A subgroup of patients develops limiting symptoms in association with left ventricular outflow tract obstruction (LVOTO). Current international guidelines recommend that symptomatic patients are initially treated by alleviating exacerbating factors and negatively inotropic medication. Drug-refractory symptoms require a comprehensive evaluation of the mechanism of LVOTO and review by a multidisciplinary team to consider the relative merits of myectomy, alcohol septal ablation (ASA) and pacing. This article provides a brief overview of HCM and the pathophysiology of LVOTO, and reviews the use of ASA in patients with drug-refractory symptoms secondary to LVOTO.

In vivo measurement of mitral leaflet surface area and subvalvular geometry in patients with asymmetrical septal hypertrophy: insights into the mechanism of outflow tract obstruction

BACKGROUND

Analyzing the determinants of systolic anterior motion of the mitral valve and consequent left ventricular outflow tract (LVOT) obstruction in patients with asymmetrical septal hypertrophy requires a comprehensive 3-dimensional analysis of mitral leaflet (ML) area, papillary muscle (PM) geometry, and the distribution of left ventricular hypertrophy.

METHODS AND RESULTS

Real-time 3-dimensional echocardiography was performed in 47 patients with asymmetrical septal hypertrophy and 32 normal controls. Patients included 20 with resting LVOT obstruction (group I) and 27 without (group II). Customized software (Omni 4D) provided a validated measure of ML surface area, LVOT area, mitral annular area and nonplanarity, LVOT hypertrophy index by topography (percent area with wall thickness >16 mm), and 3-dimensional PM positions relative to annulus. ML area was more than twice as large in group I than normal and 1.4 times normal in group II (P<0.001). Group I patients were also characterized by higher LVOT hypertrophy index and medial and anterior displacements of both PMs, resulting in a shorter inter-PM distance. Independent determinants of LVOT obstruction were indexed total ML area (adjusted odds ratio, 5.651; 95% confidence interval, 1.573 to 20.304; P=0.008) and inter-PM distance (adjusted odds ratio, 0.416; 95% confidence interval, 0.203 to 0.854; P=0.0169). Minimal LVOT area during systole correlated well with peak LVOT pressure gradient (R(2)=0.83, P<0.001); its independent determinants were left ventricular end-systolic volume (P=0.0183), indexed total ML area (P=0.0108), inter-PM distance (P=0.0378), annular height (P=0.0047), and LVOT hypertrophy index (P=0.0098).

CONCLUSIONS

Myocardium is not the only tissue affected in patients with asymmetrical septal hypertrophy, and primary changes of the mitral apparatus, including ML area increase and PM displacement, are independent determinants of LVOT obstruction and provide a comprehensive mechanism that determines leaflet slack and anteriorly directed motion. Abnormal PM-mitral valve geometry assessed by real-time 3-dimensional echocardiography can provide reasonable new targets for individualized intervention.

Echocardiographic assessment of left ventricular geometry and the mitral valve apparatus in cats with hypertrophic cardiomyopathy

OBJECTIVES

This retrospective study addressed the general hypothesis that abnormalities of the mitral valve apparatus are common in cats with idiopathic hypertrophic cardiomyopathy (HCM) and contribute to dynamic obstruction of the left ventricular outflow tract (LVOT).

ANIMALS, MATERIALS AND METHODS

106 cats (28 controls and 78 with HCM) had transthoracic two-dimensional and Doppler echocardiography performed with quantification of 33 variables. Three groups of cats (control [Group-1], HCM without obstruction [Group-2], and HCM with obstruction [Group-3]) were identified and compared by analysis of variance, chi(2) analysis, and correlation analysis.

RESULTS

Cats in Group-3 had more LV and papillary muscle hypertrophy, increased length of the anterior mitral valve leaflet, and a higher prevalence of false tendons in the LVOT compared to cats in Group-2 (P < or = 0.05). The length of the anterior mitral valve leaflet was correlated to the severity of dynamic obstruction (P < or = 0.05) and the magnitude of LV hypertrophy (P < or = 0.001). Systolic anterior motion of chordae tendineae (CAM) was observed in 16% of control cats and >50% of cats with HCM (P < or = 0.05).

CONCLUSIONS

Abnormalities of the mitral valve are common in cats with HCM suggesting a possible role in the pathogenesis of dynamic outflow tract obstruction.

Echocardiography in hypertrophic cardiomyopathy diagnosis, prognosis, and role in management

Hypertrophic cardiomyopathy (HCM) is diagnosed on the basis of left ventricular (LV) hypertrophy for which there is insufficient explanation (e.g. mild hypertension or mild aortic stenosis with marked hypertrophy). Echocardiography is an invaluable tool in the diagnosis and follow-up of patients with HCM. Echocardiographic assessment requires a comprehensive assessment in several imaging planes with careful attention to correct beam alignment in order to minimize errors in the measurement of LV wall thickness and appropriate identification of hypertrophy with an unusual distribution.

Extended septal myectomy for hypertrophic obstructive cardiomyopathy with anomalous insertion of chordae tendineae

We present a case of hypertrophic cardiomyopathy with anomalous insertion of mitral valve chordae tendineae diagnosed with two-dimensional echocardiogram. A high gradient was found in left ventricular outflow tract (LVOT) obstruction, which was attributed to the fixed gradient caused by anomalous insertion of chordae tendineae in addition to the gradient of dynamic LVOT obstruction. The misinserted chordae tendineae were resected, and an extended septal myectomy was performed. Follow-up echocardiography showed reduction of the pressure gradient to less than 40 mm Hg in the LVOT, and the patient had no symptoms during the 1-year follow-up period.

What is the best surgical treatment for obstructive hypertrophic cardiomyopathy and degenerative mitral regurgitation?

BACKGROUND

Many prefer mitral valve replacement (MVR) for patients with obstructive hypertrophic cardiomyopathy (HCM) and concomitant degenerative mitral regurgitation (MR). We reviewed our results of septal myectomy combined with mitral valve repair (MVrep) and MVR when these problems coexist.

METHODS

Between 1990 and 2006, 32 patients (56% men; mean age, 60.7 +/- 16.7 years) underwent extended septal myectomy for HCM with concomitant MVrep or MVR for degenerative MR (4% of myectomies and 3% of isolated MVrep during the same period). Preoperatively, 63% were in New York Heart Association (NHYA) functional class III/IV. Preoperative peak left ventricular outflow tract (LVOT) gradient was 63.7 +/- 37.6 mm Hg. Systolic anterior motion (SAM) was present in 94%, with severe MR in 88%.

RESULTS

Extended septal myectomy included concomitant MVrep in 28 (88%) or mechanical MVR in 4 (12%). MVrep included leaflet resection in 10 (36%), edge-to-edge stitch in 6 (21%), and leaflet plication in 8 (29%). An annuloplasty ring/band was used in 19 (68%) and commissural annuloplasty in 2 (7%). There was one early death (3%). At discharge, resting LVOT gradient was reduced to 10.2 +/- 19.0 mm Hg (p < 0.005). Dismissal echocardiography in MVrep patients demonstrated chordal SAM in 6 (21%, p < 0.005). MR was absent or mild in 21 (75%) and moderate in 6 (21%; p < 0.005 vs preoperatively). At late follow-up, LVOT gradient was 2.5 +/- 5.8 mm Hg, SAM resolved in all patients, and 2 had moderate MR; 24 (83%) were in NYHA class I/II (p < 0.005).

CONCLUSIONS

Concomitant MVrep with myectomy for HCM and degenerative MR can be performed with low early mortality with satisfactory relief of LVOT obstruction and MR. Most patients have significant relief of symptoms. MVR can be avoided in most patients with degenerative MR and HCM.