Post-myocardial infarction (MI) patients who have left ventricular (LV) dysfunction and left branch bundle block (LBBB), risk of ventricular tachyarrhythmic events was directly related to time elapsed from MI, according to results from the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy) substudy.
The substudy conducted by Mehmet F. Ozlu, MD, of Abant Izzet Baysal University in Bolu, Turkey, and colleagues was published in JACC: Clinical Electrophysiology. They sought to explore the relationship between the time elapsed from MI and risk of ventricular tachyarrhythmic events in 693 patients with ischemic cardiomyopathy and known date of MI.
As researchers pointed out, “Implantable cardioverter defibrillators (ICDs) implanted 40 days after MI and 90 days after revascularization reduces the risk of sudden death in post-MI patients with LV dysfunction.” However, there has been some debate as to when the greatest benefit is derived, prompting MADIT-CRT investigators to conduct this substudy.
The time elapsed from MI was defined as the time from the date of most recent MI to device implantation. Researchers grouped patients into quartiles according to elapsed time from MI, and then compared quartile 1 patients to patients in quartiles 2 through 4. Patients with an elapsed time from MI <3 years (n=172) were included in quartile 1 and quartiles 2 through 4 included patients with an elapsed time from MI ≥3 years (n=521).
First occurrence of appropriate ICD therapy for ventricular tachycardia/ventricular fibrillation or death was the primary end point, with secondary end points including appropriate device therapy for the combined end point of ventricular tachycardia/ventricular fibrillation, appropriate anti-tachycardia pacing therapy alone, and appropriate device shock therapy.
The primary end point occurred in 256 patients during a median follow-up of 3.3 years (interquartile range: 1.5 years), and the median elapsed time from MI to enrollment in the trial was 8.6 years (interquartile range: 12.1 years).
About 75% of patients had their MI 3 or more years before enrollment. Those patients were older and less likely to have diabetes and hypertension compared to patients with shorter elapses from MI (<3 years). Patients with an elapsed time from MI ≥3 years were more likely to have undergone coronary artery bypass grafting compared to patients with <3 years elapsed from MI.
In addition, patients with an elapsed time from MI ≥3 years had lower rates of CRT-D treatment compared to patients with shorter time lapses from MI. Between the 2 groups, the mean LVEF, QRS duration, BMI, and glomerular filtration rate were similar. A large majority of patients were on beta-blockers, angiotensin-converting enzyme inhibitors, or aldosterone receptor blockers and statins. Patients with LBBB had a median LVEF of 28.7% vs 29.5% in patients with non-LBBB (P<.001).
In the highest quartile, the cumulative probability of ventricular tachycardia/ventricular fibrillation or death at 3 years was 41% and 22% in the lowest quartile (P=.015 for the overall difference). “Similarly, a significantly higher cumulative probability of VT/VF [ventricular tachycardia/ventricular fibrillation] was seem in patients in the highest quartile of elapsed time from MI when compared to patients in the lowest quartile of elapsed time of MI (P<.001),” researchers wrote.
Multivariate analysis demonstrated that among patients with LBBB, an elapsed time from MI ≥3 years had a significant 2.3-fold (95% confidence interval: 1.43-3.80; P=.001) higher risk of ventricular tachycardia/ventricular fibrillation or death compared to those with shorter elapsed times and a similarly higher risk for the secondary end points.
“These findings suggest that patient with remote MIs should be closely monitored and considered for implantation of an ICD or CRT-D when indicated, to reduce the risk of sudden cardiac death and improve outcomes,” researchers concluded.
They urged future studies to examine the use of time elapsed from MI as an additional risk marker for sudden cardiac death in patients with ischemic cardiomyopathy.
Disclosures: MADIT-CRT was supported by an unrestricted research grant from Boston Scientific to the University of Rochester Medical Center.
Ozlu MF, Barsheshet A, Moss AJ, et al. Time dependence of ventricular tachyarrhythmias after myocardial infarction: a MADIT-CRT sub-study. JACC Clin Electrophysiol. 2016. doi:10.1016/j.jacep.2016.04.010.