CARISMA: Loop Recorders Might Help Stratify Risk in Post-MI Patients

April 07, 2008

April 7, 2008 (Chicago, IL) – For patients with diminished left ventricular ejection fractions following MI, implanting an ECG loop recorder may help to stratify risk by identifying life-threatening cardiac arrhythmias. A recent study showed that implantable loop recorders detected a number of arrhythmias in these patients, as well as atrioventricular (AV) block, which is not treated with an ICD but was a strong predictor of cardiac death in this study.

The study, known as Cardiac Arrhythmias and Risk Stratification after Myocardial Infarction (CARISMA), was presented here earlier this week at the American College of Cardiology 57th Annual Scientific Session. "The study was not designed to answer the question about whether or not this was a clinically useful tool," lead investigator Dr Paul Erik Bloch Thomsen (University of Copenhagen, Denmark) told heartwire , "but I can tell you that a lot of the patients with AV block did receive pacemakers, and patients with nonsustained ventricular tachycardia and sustained ventricular tachycardia did receive ICDs."

Previous CARISMA data was first presented at the Heart Rhythm Society (HRS) annual meeting last year and reported by heartwire at that time. With that study, investigators assessed the predictive value of electrophysiologic testing and noninvasive screening tests for tachyarrhythmia performed at six weeks after MI. In this analysis, investigators wanted to document the incidence and prognostic significance of the cardiac arrhythmias obtained from the ECG loop recorder.

Investigators identified 1393 patients with ejection fractions <40% at three to 21 days post-MI, but only 297 patients agreed to have loop recorders implanted. The devices were implanted at five to 21 days post-MI, and patients were followed quarterly for two years.

Rhythm disturbances were common, reported Bloch Thomsen. Overall, 137 patients had documented ventricular fibrillation or at least one prespecified arrhythmia. Of these, 86% were asymptomatic. They also observed an increased incidence of new-onset atrial fibrillation, with 32% of patients developing the rhythm disorder. About 17% of patients had ventricular tachycardia or supraventricular tachycardia. In univariate analysis, AV block, sinus bradycardia, and nonsustained ventricular tachycardia were predictors of cardiac death, but only AV block remained significant in multivariate analysis.

"It will be useful in the future," said Bloch Thomsen, referring to the loop recorder. "I think this is a useful device to guide management." He noted that post-MI patients with ejection fractions >35% are not usual candidates for ICDs, but the loop recorder could provide warning signs of sudden cardiac death, especially if arrhythmias were detected.

Cost, at $2000 per unit, and the reluctance of patients to have a diagnostic device implanted are impediments to using the loop recorder regularly in clinical practice, said Bloch Thomsen.

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