Niraj Varma, MD, PhD
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Despite common guidelines for cardiac resynchronization therapy (CRT) practice, the application of CRT differs substantially between U.S. and non-U.S. participants in the international Advance CRT Registry. And the differences suggest that patients receiving CRT in the U.S. are considerably more difficult to treat than their counterparts in other parts of the world.
Those are key conclusions of an analysis of enrollment data for more than 1,500 patients in the Advance CRT Registry being presented May 6 by Cleveland Clinic electrophysiologist Niraj Varma, MD, PhD, at Heart Rhythm 2016, the Heart Rhythm Society’s 37th annual scientific session.
“Compared with CRT patients in other nations, the population of patients receiving CRT in the United States has less-typical characteristics — such as lower rates of left bundle branch block, lower rates of QRS > 150 ms, more ventricular scarring and a greater comorbidity burden,” says Dr. Varma, who serves as chairman of the Advance CRT Registry. “This makes U.S. patients more challenging to treat effectively.”
Advance CRT Registry at a glance
The international registry was designed to improve understanding of CRT care strategies, especially for nonresponders to CRT, in real-world practice settings around the globe. The current analysis of enrollees’ baseline characteristics is among the first data reported from the registry, whereas data collection for several other outcome measures continues through the end of 2016.
The current analysis compared demographic and baseline clinical characteristics between 1,147 CRT patients from 42 U.S. centers and 382 CRT patients from 27 centers outside the U.S. (largely from Asia, with none from Europe). The non-U.S. patients represented 25 percent of the registry’s overall sample and were enrolled in India (n = 205), China (n = 44), South Korea (n = 35), Japan (n = 33), Colombia (n = 27), Brazil (n = 29) and Argentina (n = 9).
Where the groups did not differ
Results revealed no significant differences between the U.S. and non-U.S. groups in the following variables:
- Gender (68 percent male across both groups)
- Percentage of patients with NYHA Class III heart failure
- Diabetes prevalence
- Use of antiarrhythmic medications
Where and how the groups differed
Patients outside the U.S. were younger (62.9 ± 11.1 years vs. 69.5 ± 11.2 years; P 150 ms
- Nonischemic cardiomyopathy
- Poorer left ventricular (LV) function
In contrast, registry patients in the U.S were more likely to be obese, to have atrial fibrillation, to have a smoking history and to have milder heart failure (NYHA Class I or II).
Differences in CRT practices
The analysis also showed that U.S. patients were more likely to have a quadripolar LV lead implanted in the lateral location (P < .0001), whereas LV leads in non-U.S. patients were more likely to be bipolar and placed posterolaterally (P < .0001).
Although CRT defibrillators were used more widely than CRT pacemakers in both groups, the proportion of defibrillator use was greater among U.S. patients (P < .001).
The finding that Dr. Varma finds most striking what was the low proportion of U.S. patients who received CRT for a class 1 indication — approximately 20 percent, compared with nearly two-thirds for patients outside the U.S. “This means we are taking on more difficult patients in this country,” he says.
“In view of these more challenging patients,” he adds, “we may need enhanced methods to achieve the best performance from implanted devices.” He cites the focus of another key presentation at Heart Rhythm 2016 — multipolar pacing, as assessed in the late-breaking MultiPoint Pacing IDE Study, for which he was a co-investigator — as one example of these enhanced approaches.