Sophisticated pacemakers benefit heart-block patients
People with an electrical malfunction that blocks signals from the top of the heart to its lower chambers fare better with an advanced pacemaker that synchronizes cardiac rhythm, researchers said.
The findings should help persuade doctors to use pacemakers that provide pacing for the left as well as right side of the heart, said lead researcher Anne Curtis, chairwoman of the Department of Medicine at the State University of New York at Buffalo's School of Medicine and Biomedical Sciences.
The newer and more expensive pacemakers more closely replicate the way a healthy heart would beat, said David Steinhaus, medical director for cardiac rhythm disease management at Medtronic. The results show patients who got bi-ventricular pacing were 26 percent less likely to die, be hospitalized for heart failure therapy or have their heart further enlarge than those with traditional devices.
"We have had reason to suspect this for years, but we never have a large-scale study to show there is a benefit" from using the devices known as cardiac resynchronization therapy, Curtis said in a telephone interview. "This kind of information should lead to a change in the guidelines" and make the CRT devices, which have been on the market since 2001, the standard of care, she said.
The results apply to the 800,000 patients in the United States with heart block, when the heart beats too slowly and the signals that tell it to contract fail to run smoothly from the atria to the ventricles.
The findings may boost use of the more sophisticated pacemakers, which cost about $8,000, almost twice the price of the older models. They may also help bolster the pacemaker market, which has slumped to less than $4 billion in recent years amid falling prices and fewer implants.
The study used devices from Minneapolis-based Medtronic, which funded the trial. Boston Scientific, based in Natick, Mass., and St. Jude Medical, based in St. Paul, Minn., also market the CRT pacemakers.
The procedure requires doctors to insert an additional lead into the heart, which can be more complicated, Curtis said. During the study of 691 patients followed for an average of three years, about 1 in 4 switched from standard right heart pacing to the biventricular model, which could have skewed some of the results.
Patients with the weakest hearts already are receiving the coordinated pacing from the newer devices, said Paul Friedman, an electrophysiologist at Mayo Clinic in Rochester, Minn. The results may change care for those with stronger hearts, he said in a telephone interview.
"Essentially it's like the timing is off on a car, the pistons aren't firing properly, because the electrical signals aren't reaching all parts of the heart at the correct time," he said. "This study is a missing piece of evidence. It extends this potentially to people who don't have a weak heart pump."
A second study found reprogramming cardiac defibrillators slashes the number of unnecessary and painful shocks. Delaying the speed with which the devices fire and allowing the heart to race faster before the defibrillator is triggered cut the shocks and unexpectedly boosted survival by 55 percent.
About 1 in 5 of the shocks given now are in response to erratic heart rates that aren't life threatening, a 2008 study found. Programming the defibrillators to go off once the heart hits 200 beats a minute, rather than the current standard of 170 beats a minute, cut the risk of a first inappropriate shock by 79 percent, the study found.
The results were "striking" and could benefit a broad range of people at risk for sudden death, said Arthur Moss, the lead researcher and a professor of cardiology at the University of Rochester Medical Center in New York. The study involving 1,500 patients was funded by Boston Scientific.
"There is considerable research to suggest that there is a small amount of damage to the heart muscle with each delivered shock," Moss said in a statement. "If we can eliminate the unnecessary shocks, this is going to be associated with less heart damage."