Abstract
Introduction: QT dispersion (QTd) and Tp-e interval show controversial results in incidence of sustained ventricular arrhythmias (SVA) in patients with heart failure (HF). In patients with implanted cardiac resynchronization therapy (CRT) device, there is a unique opportunity to record SVAs. The aim of this study was to evaluate the effects of QTd and Tp-e interval on the incidence of SVAs after simultaneous biventricular (Biv) pacing. Methods: In the present study, 31 consecutive patients with advanced HF and implanted CRT device were evaluated one year for possible SVAs, corrected QT (QTc), QTd, and Tp-e interval. Patients were divided into two groups; with (group 1) and without (group 2) SVAs. Results: Among the studied patients, 5 (16%) experienced SVAs. The intrinsic and Biv pacing QTd were 70.74 ± 18.00 and 89.26 ± 28.00 msec, and 95.09 ± 44 and 88.09 ± 33 msec in group 1 and group 2, respectively (P = 0.18 and P = 0.16, respectively). Tp-e was not different between the two groups. In group 1, QTc increased from 438.83 ± 64 msec to 488.24 ± 48 msec (P = 0.13), and in group 2, it decreased from 499.70 ± 65.00 msec to 480.00 ± 31.00 msec after simultaneous Biv pacing (P = 0.13). Conclusion: QTd, Tp-e, and QTc did not differ significantly after Biv pacing to show any positive effect on the incidence of SVAs in part due to the severity of changes which already occur in patients with advanced HF. QTc, QTd, and Tp-e showed little changes after Biv pacing and probably do not have a significant role in the incidence of SVAs.
Highlights
QT dispersion (QTd), Tp-e, and QTc did not differ significantly after Biv pacing to show any positive effect on the incidence of sustained ventricular arrhythmias (SVA) in part due to the severity of changes which already occur in patients with advanced heart failure (HF)
QTd, Tp-e, and QTc did not differ significantly after Biv pacing to show any positive effect on the incidence of SVAs in part due to the severity of changes which already occur in patients with advanced HF
It has been shown that Cardiac resynchronization therapy (CRT) can reduce the possibility of sudden cardiac death probably due to its induction of left ventricular remodeling; some proarrhythmic effects have been attributed to CRT in the literature.[2]
Summary
This study was designed to evaluate the effects of QTd and Tp-e duration on incidence of SVAs in patients who have undergone CRT-D device implantation. The frequency of NSVAs in the present study was about 54.8% which may to some degree justify the relatively high incidence of SVAs. The changes in QTd after simultaneous Biv pacing were not significant in all patients. CRT-D was more effective in decreasing QRS duration in patients with wider intrinsic QRSs. The protective effects of shortening of QRS duration after Biv pacing may overcome other electrophysiological changes occurring after CRT-D device implantation. After simultaneous Biv pacing, the numbers tend to be equal in groups with and without SVAs. the important predictors for major arrhythmias after CRT implantation may be the degree and direction of changes from baseline values not the numbers after Biv pacing itself. It seems that factors like the degree and direction of changes from baseline values and degree of narrowing of QRSs are better predictors
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