Recovery PVCs on exercise test are prognostic

February 01, 2008

Palo Alto, CA - A new study shows that individuals undergoing treadmill testing who had ventricular arrhythmias during the recovery phase had an almost doubling of mortality in the five-year follow-up period, compared with those who had arrhythmias only during exercise[1]. Dr Frederick E Dewey (Stanford University Medical School, Palo Alto, CA) and colleagues report their findings in the January 28, 2008 issue of the Archives of Internal Medicine.

Dewey told heart wire : "Recovery premature ventricular complexes [PVCs] seem to be more significant than PVCs that occur during exercise testing. They seem to have some prognostic significance, so that there appears to be additional risk stratification provided by arrhythmias during recovery," he noted. In contrast, PVCs occurring solely during exercise have limited prognostic significance, he said.

"Given the fact that there was a strong association with markers for ischemia with recovery PVCs, these patients might benefit from a more sensitive imaging modality for demonstrating (or not demonstrating) myocardial ischemia, such as myocardial perfusion imaging or exercise echo," he suggests.

Significance of exercise and recovery PVCs unclear

Dewey and colleagues explain that the relative prognostic significance of exercise and recovery-period ectopy has been unclear. "While some have found that recovery ectopy is more robustly associated with adverse prognosis than exercise ectopy, other results suggest otherwise." These apparent disparities may result from inconsistent methods, varied definitions of significant arrhythmia, differences in sample size and length of follow-up, or etiologic differences in PVCs in the various subject populations that have been studied, they note.

"We aimed in this study to evaluate the clinical correlates and relative prognostic significance of exercise and recovery PVCs in subjects referred for clinical exercise treadmill testing." They studied 1847 heart-failure-free patients who underwent exercise testing between March 1997 and January 2004 in the Veterans Affairs Palo Alto Healthcare System. About 55% of subjects had PVCs at some stage during exercise," Dewey noted; 46% developed exercise PVCs and 33.6% had recovery PVCs.

During 5.4 years of follow-up, 161 subjects (8.7%) died, and 53 of these deaths (32.9%) were due to cardiovascular causes. Recovery PVCs, but not exercise PVCs, were associated with 71% to 96% greater propensity-adjusted mortality rates (hazard ratio 1.96 for infrequent PVCs and HR 1.71 for frequent PVCs, compared with subjects without PVCs).

PVCs during exercise were associated with increased mortality rates only if accompanied by PVCs after exercise. But "similar to previous findings in clinical cohorts . . . recovery PVCs were robustly associated with adverse prognosis regardless of the presence of PVCs during exercise.

"Of note, the hazards for infrequent and frequent PVCs after exercise were similar, suggesting that the absolute presence of recovery PVCs has more prognostic significance than does the recovery PVC frequency," they add.

Occurrence of recovery PVCs reclassified 33.2% of subjects with intermediate-risk Duke Treadmill Scores into higher-risk subgroups.

Will statins reduce recovery PVCs?

Dewey et al go on to speculate on the possible mechanistic basis for their observations. Previous studies have suggested that age-associated fibrosis of the myocardium, ischemia, ventricular hypertrophy, and loss of vagal tone may lower the arrhythmic threshold, they note.

"A predisposition to or findings consistent with ischemia were associated only with recovery PVCs after adjustment for other variables in our population. Our findings suggest that this association was independent of other factors only in the recovery period," they note.

In contrast, both infrequent and frequent exercise PVCs were directly related to the heart-rate increase with exercise, likely resulting from increased sympathetic activity in subjects who were able to attain higher peak heart rates, they note.

Dewey told heart wire that the next step for his team is to look at interventions to see what might reduce the risk of arrhythmias during the recovery phase of exercise testing. Although many of the patients in this study were already taking statins, "a significant proportion were not," he noted, so they now plan to look at how statin use might reduce the rate of recovery PVCs.

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