Catheter Ablation of Right Ventricular Outflow Tract PVCs
Abstract & Commentary
With Comments by John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville. Dr. DiMarco is on the Editorial Board of Clinical Cardiology Alert.
Synopsis: Eliminating frequent right ventricular outflow tract PVCs improves left ventricular function, particularly in patients with extremely high density arrhythmias.
Source: Takemoto M, et.al. J Am Coll Cardiol. 2005;45: 1259-1265.
Takemoto and colleagues from Kitakyushu, Japan, report that there is symptomatic and functional improvement after radiofrequency ablation of monomorphic right ventricular outflow tract premature ventricular contractions (PVCs) in patients with frequent PVCs, but no apparent underlying structural heart disease. Between the years 1994 and 2004, 10 men and 45 women with a mean age of 50 ± 2 years underwent attempted radiofrequency catheter ablation for right ventricular outflow tract PVCs in the Takemoto et al’s laboratory. Structural heart disease was excluded by appropriate invasive and/or noninvasive testing. Echocardiograms were obtained prior to the procedure, with all values calculated for measurements made during only sinus rhythm. Echographic exams were repeated immediately after, and 6 to 12 months after the radiofrequency ablation.
Of the 45 patients initially identified, 5 patients were lost to follow-up and were excluded from further analysis. Procedural success was achieved in 37 (93%) of the remaining 40 patients. Prior to radiofrequency ablation, there was a relationship between the left ventricular (LV) end diastolic interval dimension and PVC frequency, suggesting an association between frequent PVCs and LV dilation. On the basis of their PVC frequency, patients were divided into 3 groups. The lower frequency group had less than 10% of their total cardiac beats on a 24-hour Holter monitoring, the middle frequency group had 10% to 20% PVCs, and the high frequency group had greater than 20% PVCs. After radiofrequency ablation, the total PVC frequency decreased in all 3 groups. In the middle group, the total PVC frequency decreased from 133 ± 11 (× 100) to 11 ± 8 (× 100) beats per day. In the upper group, the total PVC frequency decreased from 381 ± 34 (× 100) to 13 ± 9 (× 100) beats per day. In the patients with the most frequent PVCs, there were significant improvements in ejection fraction, left ventricular dimension, and degree of mitral regurgitation in the frequent PVC group. These changes were not observed on the echocardiogram the day after ablation, when sinus rhythm was already present, but were noted on the follow-up studies between 6 and 12 months later. Radiofrequency ablation significantly improved New York Heart Association functional class in each group. In the high frequency group, this was confirmed by a normalization of previously elevated brain natruretic peptide levels.
Takemoto et al conclude that eliminating frequent right ventricular outflow tract PVCs improves left ventricular function, particularly in patients with extremely high density arrhythmias.
Comments
We usually think of right ventricular outflow PVCs as having only a benign significance. As a result, radiofrequency ablation is recommended only in patients with symptoms. All of the patients in this series had some symptoms, so we should be careful extending observations to truly asymptomatic patients. However, it has been my experience that even patients who deny symptoms but have over 10,000 or 20,000 PVCs during a 24-hour period usually will feel better if their arrhythmias are eliminated either with drug therapy or catheter ablation. The study here confirms that PVCs at this frequency may have subtle deleterious effects. Although this study seems to have been carefully done, its implications should be interpreted cautiously. It is frequently difficult to estimate ventricular function in patients with this high a frequency of PVCs. In the study, Takemoto et al make careful attempts to analyze echocardiograms obtained only during sinus rhythm. Since many patients with outflow tract PVCs will suppress their ectopy during exercise, this sometimes has to be done during echocardiography. The fact that they noted that there was no change in the ventricular dimensions the day after radiofrequency ablation, even though the ectopy had disappeared, is the strongest evidence that there is a chronic remodeling process in patients with this very high frequency ventricular ectopy. Whether this is important for long-term clinical end points remains to be determined.
Eliminating frequent right ventricular outflow tract PVCs improves left ventricular function, particularly in patients with extremely high density arrhythmias.
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