Over the past several years, cardiac resynchronization therapy (CRT), which involves the implantation of a biventricular pacemaker, has become an increasingly common treatment for certain heart failure patients who do not respond adequately to medication. However, according to new research, about 40 percent of the 50,000 people who receive biventricular pacemakers each year may not benefit from the devices, which cost about $70,000 each.
Placement of a biventricular pacemaker was originally recommended for patients with systolic heart failure, severe limitations on physical activity and an interval of 120 milliseconds or more for activation of the right and left ventricles. The interval for activation of the two ventricles is known as QRS duration. QRS duration ranges from 60 to 110 milliseconds in healthy people.
About a third of the people who experience systolic heart failure have a QRS duration greater than 120 milliseconds. Criteria for receiving a biventricular pacemaker were ultimately extended to people with relatively mild symptoms but a QRS duration of at least 150 milliseconds.
As the popularity of biventricular pacemakers grew, it became apparent that a substantial number of people30 to 50 percentdid not benefit from the treatment. Research suggested that patients with QRS durations between 120 and 150 milliseconds were less likely to experience fewer heart failure-related clinical events, such as hospitalization and death, with the pacemaker.
Because the role of QRS duration on the effectiveness of biventricular pacemakers had not been rigorously explored, researchers at Case Western Reserve University examined data from five randomized trials, involving nearly 6,000 subjects, that reported the types of clinical events that happened within different QRS ranges.
Researchers found that biventricular pacemakers were helpful in reducing clinical events in patients who had systolic heart failure and a prolonged QRS duration of 150 milliseconds or longer prior to treatment. The biventricular pacemakers were less likely to provide benefit, however, for individuals with moderately prolonged QRS, 120 to 150 milliseconds, regardless of the severity of symptoms.
The researchers’ conclusion suggested that too many patients are receiving biventricular pacemakers, and that doctors should more carefully consider whom they recommend for the devices.
Source: Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50