AHA Sessions: Arrhythmia Trials Present Substantial Findings

Two large arrhythmia trials were presented at the American Heart Association Sessions this week, which could significantly impact clinical practice.  Oklahoma Heart Institute participated in both national, multi-center randomized trials, the BLOCK HF trial and MADIT-RIT trial.  Oklahoma Heart Institute cardiac electrophysiologist, Dr. David Sandler explains the impact of these findings for patients, “whether through device choice or device programming, we are identifying opportunities to make dramatic improvements in patient outcomes."

The BLOCK HF national clinical trial studied more than 900 patients over the course of eight years with heart block and some degree of heart failure. Heart block refers to a problem some patients experience when the electrical signal that regulates rate and rhythm is slowed or disrupted as it moves throughout the heart. The trial looked at the hypothesis that outcomes would improve if both sides of the heart were resynchronized using cardiac resynchronization therapy, as opposed to pacing only one side of the heart. Looking at the composite endpoint of mortality, heart-failure related urgent care and deterioration in heart function detected by echocardiography, outcomes improved by 26 percent for patients who had biventricular pacing.
“This study would not have been possible without the dedication of our amazing research team, hard working staff and trusting patients since most of these ‘study patients’ presented after hours and in distress,” says Dr. Sandler.  “We applaud all those who participated.”
Dr. Anne Curtis, BLOCK HF lead researcher explains how biventricular pacing works in this video.


The Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy was a large national randomized trial that identified simple programming criteria for implantable cardioverter defibrillators (ICDs), which cut the risk of inappropriately delivered therapy by nearly 80 percent. For patients with non-life threatening arrhythmias, inappropriate treatment can add to the distress patients are experiencing as well as potentially worsen outcomes.
The results of this trial showed a reduction in inappropriate therapy due to antitachycardia pacing (ATP) as well as mortality by 55 percent. By allowing patients with non-life threatening arrhythmias to delay intervention by their ICD until the heart rate exceeded 200 bpm, relatively benign supraventricular arrhythmias and some nonsustained ventricular arrhythmias went untreated. Whereas conventional treatment would have initiated delivering therapy at 170 bpm, researchers observed this simple threshold change (from 170 bpm to 200 bmp) reduced unnecessary ATP, which could induce ventricular fibrillation among other side effects.
The results of this trial, researchers say supports other trials that have come before MADIT-RIT and should greatly impact potentially damaging and unnecessary therapy for benign arrhythmias that stop spontaneously without ill effects for patients.
“It cannot be overstated that having an ICD implanted requires sophistication not only in the choice of device, but also the programming,” Dr. Sandler says.  “This study shows that simple adjustments to the ICD settings can reduce the rate of unnecessary shocks and even improve survival.  If patients have an ICD, it is important that they have a rhythm specialist (electrophysiologist) review their programming to confirm that the most state-of-the art settings have been programmed.”