SNOWMASS, COLO. — American physicians are probably overtreating many patients with advanced heart failure and conduction delay by implanting combined biventricular pacemaker/cardioverter defibrillators, Dr. Michael R. Gold said at a conference sponsored by the Society for Cardiovascular Angiography and Interventions.
It's likely that in many such patients, a simpler biventricular pacemaker for cardiac resynchronization therapy (CRT) alone would achieve the same goals of reduced mortality, fewer hospitalizations, and improved quality of life, compared with medical management, according to Dr. Gold, professor of medicine and director of adult cardiology at the Medical University of South Carolina in Charleston.
“We do not have definitive data that biventricular pacemaker/defibrillators are better than biventricular pacing alone, despite being about four times the cost,” he said.
Yet 9 out of 10 devices implanted for treatment of advanced heart failure in the United States are combination CRT/implantable cardioverter defibrillators (ICDs), whereas European physicians tend to favor CRT alone, he said.
And a landmark European trial, the Cardiac Resynchronization-Heart Failure (CARE-HF) study—“one of the most important studies ever done in this field,” in Dr. Gold's view—showed that CRT without an ICD resulted in a 45% reduction in death from worsening heart failure and a 46% drop in sudden death over 3 years, compared with medical management, said Dr. Gold.
For now, however, it is not clear which specific patients ought to get a simple biventricular pacemaker rather than a combined CRT/ICD device; that issue is being investigated in the second Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT-2).
In addition to the mortality benefit, cardiac resynchronization therapy brings impressive quality-of-life and economic gains. In the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) trial, reported in 2002, CRT resulted in a 50-m improvement in 6-minute walk distance after 6 months. No heart failure drug provides an improvement of comparable magnitude.
CRT has been shown in multiple studies to cut hospitalizations by up to 50%, compared with medical management alone. “If you start to play that out, we're not talking about the expense of resynchronization, we're talking about the cost savings,” Dr. Gold said.
“It actually saves money to put in a biventricular pacemaker in the right group of patients because the amount saved in hospitalizations more than offsets the cost of this therapy,” he added.
Cardiac resynchronization therapy is so effective because it has been shown to increase myocardial contractility while reducing myocardial oxygen consumption. The only other treatment that can do that is a β-blocker.
“Biventricular pacing is essentially an electronic β-blocker for our patients. We see virtually the same response long term with β-blockers that we see with CRT,” he explained.
He stressed that cardiac resynchronization therapy needs to be used in conjunction with optimal medical therapy. Indeed, CRT actually facilitates drug therapy. For example, by regulating blood pressure and minimizing hypotension, CRT permits uptitration of ACE inhibitors. And because CRT prevents bradycardia—a common limiting factor in β-blocker therapy—that drug can also be uptitrated.
The CRT nonresponder rate is high—30% in most studies.
It's not widely appreciated that this nonresponder group includes a substantial number of patients who are made hemodynamically worse by biventricular pacing.
“These tend to be patients with a narrower QRS interval. I am often referred patients with a QRS interval of 120, 115, or even 110 milliseconds, with the comment that 'Their heart failure is bad—why don't you put in a biventricular pacemaker?' Well, one of the reasons not to is that you can make these patients worse. They're better off conducting through their native conduction system than to artificially be stimulated from the right ventricular apex or left ventricular free wall,” Dr. Gold said.
“If you look at large patient series using QRS duration as a crude way to try to identify these groups of patients, you'll find that when you get out to 160–170 milliseconds, 80%–90% of patients are going to respond,” he said. But down at 125 milliseconds only about 20% are going to be responders, and a very significant percentage of the others not only will not be responders but will have an adverse hemodynamic response to this therapy,” he added.
Dr. Gold serves as a consultant to the device makers Guidant Corp. and Medtronic Inc.