Myocardial scar detection by CMR in hypertrophic cardiomyopathy

Myocardial scar detection by CMR in hypertrophic cardiomyopathy

Myocardial scar detection by CMR in hypertrophic cardiomyopathy: Hypertrophic cardiomyopathy is one of the important genetically mediated cardiovascular disorders and the commonest among them. It is transmitted in an an autosomal dominant pattern and has a propensity for sudden cardiac death and an annual mortality ranging from one to five percent. Implantation of an implantable cardioverter defibrillator (ICD) is a life saving option in patients with hypertrophic cardiomyopathy. Since ICD is a costly option and not without associated problems, case selection is an important consideration. Accepted high risk markers include a family history of sudden cardiac death (>/= 1 first degree relative, <50 years of age), previous resuscitated cardiac arrest, ventricular tachycardia, syncope, left ventricular outflow obstruction (gradient >30 mm Hg) and gross ventricular hypertrophy (maximum wall thickness >/= 30 mm Hg). Still risk prediction has its own limitations due to the low positive predictive value.

It is in this context that detection of myocardial scar by late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) has been evaluated by Bruder O and associates (J Am Coll Cardiol, 2010; 56:875-887). They could have a mean follow up period of 1090 days in two hundred and twenty patients, all of whom underwent an initial CMR evaluation in a prospective study. There were twenty deaths and two patients had an ICD rescue from sudden cardiac death. Of these 22 events, sixteen was due to cardiac reasons and the rest due to accidents and cancer.
In this study, the extend of scar was determined automatically by the computer algorithm by counting the hyperenhanced pixels. The scar volume was assessed as a percentage of the total left ventricular myocardium. LGE was noted in 67.2% of the patients in this cohort, with scar percentages ranging from 0.9 to 39.9. Scars were mostly in the mid myocardium unlike the subendocardial scarring in ischemic heart disease and subepicardial scarring in inflammatory heart disease. LGE was found to be an independent predictor of cardiac death in hypertrophic cardiomyopathy, with a hazard ratio of 4.81 in this report, on multivariate analysis. The results are more significant as the cohort involved 81% patients who were only mildly symptomatic or asymptomatic. Another interesting aspect was that 8 of the 11 patients who had sudden cardiac death had no recognized clinical risk factors. All but one of them had scars detected on CMR. Still there was one patient without LGE or clinical risk factors, calling for more studies for additional factors like genotype and undetected coronary artery disease.