SAN FRANCISCO—Two substudies of the MADIT-CRT trial presented May 4 at this year’s Heart Rhythm Society scientific sessions showed that various factors including a younger age, being male, having a history of ventricular arrhythmia and left bundle branch block (LBBB) can be risk factors for recurrent ventricular tachyarrhytmia (VT) post-cardiac synchronization defibrillator therapy (CRT-D).
The MADIT-CRT trial evaluated 1,820 patients who were randomized to receive either CRT-D or implantable cardioverter defibrillator (ICD) therapy. The current substudies sought to evaluate which factors were associated with recurrent VT post-CRT-D.
In the first study, Gregory Ouellet, BS, a medical student of the University of Rochester School of Medicine in Rochester, N.Y., evaluated the effect of CRT-D therapy on the risk of recurrent tachyarrthymias in mild heart failure (HF) patients with a prolonged QRS duration. Ouellet and colleagues used an Anderson Gill modeling strategy to assess the risk factors for recurrent fast VT events and the effect of CRT-D vs. ICD therapy in patients with and without LBBB.
The events in both trials were defined as sustained VTs more than 180 beats/min.
The reason 180 beats/min. was chosen is because VTs “are potentially life-threatening events and since device programming was up to each individual center it was decided that most centers were programmed to detect rates of 180 or greater,” Ouellet told Cardiovascular Business.
Like previous trials, Ouellet and colleagues found that LBBB patients benefit from CRT. However, while this patient population receives benefit after a first event, researchers did not detect a benefit for reducing the risk of other recurrences after a first event.
In LBBB patients, CRT-D therapy was linked to a 28 percent reduction in the risk of recurrent VT events. In patients with non-LBBB, CRT-D was associated with an increased risk of recurrent VT.
“What we are thinking is that this could mean that patients who already experienced an event could be classified as non responders,” Ouellet said. “These patients may not be gaining benefit from reverse remodeling and as a result undergoing many arrhythmias afterwards.”
While Ouellet said that currently these results are “simply a correlation,” he said that future research will center on studying reverse modeling to understand the consequences in terms of recurrent arrhythmias.
“We want to show that these recurrent arrhythmias actually do have clinical consequences,” said Ouellet. He said that a Cox model with time-dependent variables for a first, second or third event showed that “there was a step up in the hazard ratio with each sequential event.
“The current study confirms previous studies that have shown that CRT is focused on patients with LBBB,” concluded Ouellet. “It furthers the evidence that this is a patient population that should be treated with CRT-D as opposed to all patients with wide QRS.”
Within the second study, researchers used the same trial design to better understand risk factors for the development of VTE after device implantation. David T. Huang, MD, also of the University of Rochester Medical Center, and colleagues used a Cox regression analysis to assess the risk of heart failure or death in ICD and CRT-D recipients.
After a three-year follow-up, Huang et al reported that 179 patients (8.9 percent) experienced a single VTE and 148 patients (8.2 percent) experienced two or more VT events. The results showed that patients with a history of ventricular arrhythmia prior to enrollment, a younger age (under 65) and being male were factors independently associated with the increased risk of recurrent VT events.
Huang et al reported that a single VT event and more than two VT events were associated with a 2.04 and 2.56-fold increase in the risk of HF or death, respectively.
“The occurrence of VTE was a robust predictor of subsequent mortality and HR events during the trial,” Huang concluded.
Future research should be conducted to further understand the predictors of these life-threatening arrhythmias in certain populations after device implant, as well as their consequences for patients, the researchers concluded.