Hypertrophic obstructive cardiomyopathy caused by Fabry disease: implications for surgical myectomy

Hypertrophic obstructive cardiomyopathy can be the phenotype of storage disorders as Fabry disease cardiomyopathy. In this instance, its recognition through GLA gene analysis and preventive administration of enzyme replacement therapy may reduce heart failure risk of surgical septal myectomy (SSM). A 59-year-old man was referred for SSM as dyspnoea and low threshold muscle fatigue associated to severe left ventricular outflow obstruction (gradient of 100 mmHg) due to both interventricular septal hypertrophy and mitral leaflet systolic anterior motion were not controlled by metoprolol 100 mg bid. Electrocardiogram showed sinus rhythm and a complete left bundle branch block. Cardiac magnetic resonance imaging showed a preserved left ventricular (LV) contractility (ejection fraction 70%) but failed to reveal reduced T1 mapping and fibrosis of postero-lateral LV wall suggesting Fabry disease cardiomyopathy. Cardiac catheterization and coronary angiography documented increased LV end-diastolic pressure but normal coronary arteries. SSM was followed by acute renal and heart failure with left ventricular ejection fraction declining to 35%. Histology of SSM showed regularly arranged severely enlarged cardiomyocytes containing extensive vacuoles that were intensely positive to immunofluorescence with anti-Gb3 antibodies and appeared at electron microscopy to consist of myelin bodies suggesting the diagnosis of FD. This entity was confirmed by low blood levels of alpha-galactosidase A (0.8 nmol/mL/h; NV > 1), high values of Lyso-Gb3 (5.85 nmol/L; NV < 2.3), and the presence of the pathogenic mutation c.644A>G in the exon 5 of GLA gene. This study emphasizes the importance of a genetic screening for FD before SSM be considered for hypertrophic obstructive cardiomyopathy.

[The role of Cardiovascular Magnetic Resonance in Interventional Cardiology]

Cardiovascular magnetic resonance has emerged as a very helpful tool for the interventional cardiologists not only in the assessment and treatment of coronary artery disease, but also in the evaluation of various structural cardiac diseases. The main pulse sequences are standardised, acquired during short breath-holds, and include steady-state free precession cines, dynamic myocardial first-pass perfusion imaging during contrast injection, and late enhancement imaging for the identification of myocardial substrates. Less than 30-minute CMR studies are now available for the most common clinical indications. More recently, T1 and T2 parametric myocardial maps are promising for detailed myocardial tissue characterisation (edema, replacement fibrosis, diffuse interstitial fibrosis). Technical aspects will not be addressed with particular emphasis on clinical applications.

Anterior mitral valve leaflet length in cats with hypertrophic cardiomyopathy

INTRODUCTION

Anterior mitral valve leaflet (AMVL) elongation is a recognised feature of hypertrophic cardiomyopathy (HCM). However, whether AMVL elongation precedes left ventricular hypertrophy in cats is currently unknown. The aim of this study was to explore the risk of developing an HCM phenotype in cats with an elongated AMVL.

ANIMALS

FIFTY-FIVE APPARENTLY HEALTHY CATS WITH A NORMAL BASELINE ECHOCARDIOGRAM AND A FOLLOW-UP ECHOCARDIOGRAM AT >ONE YEAR.

MATERIALS AND METHODS

This was a retrospective longitudinal study. Cats at the baseline were grouped based on whether or not they developed an HCM phenotype at follow-up. AMVL length and left atrial and left ventricular dimensions were measured from two-dimensional images.

RESULTS

The median follow-up period of the study population was 5.4 years (25th and 75th quartile, 2.7-6.7 years). During this time, 17 cats (30.9%) developed an HCM phenotype. At the baseline, cats that subsequently developed an HCM phenotype had greater AMVL length (9.4 mm [25th and 75th quartile, 9.0-10.6 mm] vs. 8.5 mm [25th and 75th quartile, 7.6-9.1 mm], P < 0.0001) and maximal left ventricular wall thickness (4.5 mm [25th and 75th quartile, 4.1-4.7 mm] vs. 4.0 mm [25th and 75th quartile, 3.7-4.6 mm], P = 0.007) than those that did not. Multiple logistic regression analysis confirmed that both baseline variables were independent predictors for development of an HCM phenotype.

CONCLUSIONS

The AMVL length was greater in cats that subsequently developed left ventricular hypertrophy. Further studies investigating the clinical application of AMVL in the natural history of feline HCM are warranted.