Insertable Loop Recorder Tracks Cardiac Arrhythmias Following Acute Myocardial Infarction

April 1, 2008 By Alexandra M. Palmer [mailto:apalmer@perfuse.org]

ACC 08-Chicago, IL: Results of the CARISMA trial demonstrate that the insertable loop recorders (ILR) can document cardiac arrhythmias following myocardial infarction. The findings were presented by Dr. Poul Erik Bloch Thomsen today at the American College of Cardiology 2008 Scientific Sessions.

The goal of the CARISMA study (Cardiac Arrhythmias and Risk Stratification after Myocardial Infarction) was to measure the efficacy of an insertable loop recorder (ILR) in recording cardiac arrhythmias post myocardial infarction. The CARISMA study was a prospective, observational, multicenter study in which 297 patients (after screening 5869 patients with an acute myocardial infarction) with an ejection fraction (EF) ≤ 40% who had suffered an acute myocardial infarction (AMI) between 3 and 21 days prior to screening were implanted with an ILR. Patients with planned bypass surgery/ implantable cardioverter defibrillator, NYHA class IV and who were unable to provide informed consent were excluded from the study.

Pre-specified arrhythmias included sinus bradycardia (≤ 30 bpm, ≥ 8 seconds), sinus arrest (≥ 5 seconds), second or third degree AV block (≤ 30 bpm, ≥ 8 seconds), non-sustained VT (≥ 125 bpm, ≥ 16 beats), sustained VT (≥ 125 bpm, ≥ 30 seconds) and new onset atrial fibrillation (≥ 125 bpm).

At the mean follow-up time of 1.8 ± 0.3 years, 137 patients (46%) with an ILR demonstrated ventricular fibrillation (VF) or at least one pre-specified arrhythmia. 86% were asymptomatic.

Among the patients who had documented arrhythmia, 7% had sinus bradycardia, 5% presented with sinus arrest, 10% with 2º or 3º AV block, 13% of patients demonstrated non-sustained VT, 3% had sustained VT, 3% had VF and 32% had new onset atrial fibrillation. In addition, documented 2º or 3º AV block <30 bpm was an independent predictor of cardiac death (HR 7, p = 0.0004).

This is the first study to document long-term cardiac arrhythmias recorded by an ILR. The investigators concluded that ILRs are good diagnostic tools and should be implemented for tracking cardiac arrhythmias in patients following an acute myocardial infarction. The occurrence of second or third degree heart block was associated with cardiac death.