Pace yourself � you'll live longer

Biventricular pacemakers can improve survival in patients
with advanced heart failure

By Chris Williams

Ben Muldoon used to list gardening as one of his favourite activities, but this 72-year-old cut back on vigorous pruning and weeding when he experienced some heart trouble a couple of years ago. He was fitted with a pacemaker, but, like most existing devices, it paces only the right ventricle. This may not be enough for Ben. His damaged heart tissue sometimes interrupts signalling between the ventricles, which can induce weak pumping action by the heart and may bring on symptoms of chronic heart failure. A new kind of pacemaker that sends each chamber an independent signal and handles the timing itself might be the answer. According to a study in the May 20 New England Journal of Medicine (NEJM), the biventricular pacemaker increases survival by about a one-third among patients with advanced heart failure. This promising technique is known as cardiac-resynchronization therapy (CRT).

Researchers from the University of Colorado followed a whopping 1,520 patients from 128 different hospitals. All the patients suffered from advanced heart failure and electrocardiograms showed that they had a QRS interval of at least 120 milliseconds � a condition that's associated with abnormal ventricular impulse conduction. The subjects were randomized to one of three treatment arms. All three groups received the best standard pharmacologic therapy in the form of diuretics, angiotensin-converting enzyme inhibitors, beta-blockers, and spironolactone. Aside from this, the control group didn't receive any extra intervention, while one arm was fitted with biventricular pacemakers, and the other with biventricular pacemaker-defibrillators.

After one year, 19% fewer people in the pacemaker group died or wound up in hospital compared to the control population. Similarly, the pacemaker-defibrillator group showed a 20% reduction in mortality and hospitalization from all causes. When death or hospitalization for heart failure alone was looked at, pacemakers and pacemaker-defibrillators reduced the risk by 34% and 40% respectively as compared to their control-group compadres. Finally, when only survival was considered, 24% more of those with pacemakers and 36% more of patients with pacemaker-defibrillators were alive to tell the tale.

The results come on the heels of a previous study in the Canadian Journal of Cardiology that found that biventricular pacemakers improve quality of life and exercise tolerance in heart failure patients. That study, in April 2003, also included patients with milder versions of the disease, who appeared to derive similar benefits from the treatment. In addition, another, very small Canadian study found that the devices improve sleep quality.

Dr Michael Bristow, lead investigator in the NEJM trial, said: "Heart failure is a major public health problem in all industrialized countries. Despite improvements in drug therapy, heart failure continues to be a disease with high rates of hospitalization and mortality, and poor patient quality of life."

"The results indicate that a substantial group of patients with advanced heart failure receive major benefit from cardiac-resynchronization therapy. These devices allow very ill, compromised patients not only to feel better and be more active, which was known previously, but also to avoid hospital and live longer. COMPANION trial results are fundamental because they demonstrate for the first time the significant improvement in patient outcomes achieved with CRT, which is over and above and incremental to optimal drug therapy."

Biventricular pacemakers have been shown to improve both quality and length of life. Unfortunately, these nifty devices cost about $50,000Cdn each, and are currently being studied by Canada's Therapeutic Products Directorate, the government body that regulates pharmaceutical drugs and medical devices. Their decision on this important issue will be of significant interest to doctors and patients.