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Separated right and left ventricular excitation during right ventricular septal pacing in a patient with narrow QRS wave: a case report
© Yaegashi et al.; licensee BioMed Central Ltd. 2014
Received: 26 December 2013
Accepted: 17 March 2014
Published: 21 May 2014
Right ventricular septal pacing is thought to be better than right ventricular apical pacing for shortening the QRS duration and for preserving left ventricular function. However, right ventricular septal pacing may not be effective in all cases. In this case report, we present a rare case in which right ventricular septal pacing induced thoroughly separated right and left ventricular excitation despite the presence of a relatively narrow QRS wave during atrium-only pacing.
We report a case of 63-year-old Japanese man with cardiomyopathy with an implantable cardioverter defibrillator placement for ventricular tachycardia. Three years after implantation, he developed second-degree atrio-ventricular block. Therefore, atrio-ventricular sequential pacing was started; then his heart failure was much worsened. His electrocardiogram showed a dissociated biphasic QRS wave during right ventricular high-septal pacing, despite the presence of a non-fragmented QRS morphology during atrium-only pacing. An activation map during right ventricular high-septal pacing showed that right ventricular conduction started at the pacing site and ended at the right ventricular basal inferior site. Subsequently after a 10ms interval, left ventricular conduction started at the left ventricular posteroseptum and ended at the left ventricular lateral wall. These data indicate that during right ventricular high-septal pacing, the first component of the QRS wave supposedly reflects only right ventricular excitation and the second component only left ventricular excitation. Also due to the intracardiac electrograms, it was assumed that this phenomenon was caused by transversely limited severe transseptal conduction disturbance.
It should be noted that even ventricular septal pacing could evoke harmful interventricular dyssynchrony due to transversely limited severe septal conduction disturbance, despite the presence of a relatively narrow QRS wave.
A prolonged duration of the QRS complex on electrocardiogram is associated with adverse prognosis not only in patients with cardiac diseases[1, 2] but also in the general population. Right ventricular (RV) septal pacing is thought to be better than RV apical pacing for shortening the QRS duration and for preserving left ventricular (LV) function[4, 5]. However, there are no apparent data suggesting that RV septal pacing is better than RV apical pacing for patients’ prognosis.
In this report, we present a case in which RV septal pacing induced thoroughly separated RV and LV excitation and contraction.
It was reported that RV septal pacing might induce intraventricular LV dyssynchrony causing severe LV ejection fraction deterioration and symptoms of congestive heart failure. However, septal pacing-induced interventricular dyssynchrony has not been reported. In this case, an ECG of the patient during RV high-septal pacing as well as during LV lateral or RV apical pacing showed a biphasic QRS complex, and this QRS morphology supposedly reflects completely separated RV and LV excitations, although the intrinsic QRS morphology in this case showed only a mild intraventricular conduction disturbance pattern.
In a previous study on patients with left bundle-branch block, two patterns of initiation of LV septal activation were observed: (1) via slow conduction through the left bundle branch and (2) via right-to-left transseptal activation. In the former pattern, the earliest LV activation occurred in the mid-septum by slow conduction through the left posterior fascicle, whereas in the latter pattern, the earliest LV activation occurred in the high septum. In the present case, the earliest LV activation started at the mid-septum during atrium-only pacing and at the basal posterior septum during the RV high-septal pacing. In addition, while intracardiac mapping was performed, fragmented potentials were recorded in the posteroseptal area during atrium-only pacing (Figure 3B), and double potentials were recorded in the same area during RV septal pacing (Figure 3D); this shows that severe conduction disturbance may have been present around this region on the working myocardium, and that myocardial excitation rose from the RV septal pacing site conducted very slowly through this damaged area transversely.
During atrium-only pacing, RV and LV excitation started and ended almost simultaneously within 166ms. During RV septal pacing, RV and LV excitation occurred sequentially; however, intraventricular conduction durations of the right and left ventricles measured by activation mapping were comparatively shorter than those during atrium-only pacing (83ms and 133ms in the right and left ventricles, respectively); therefore, it seems that each intraventricular conduction uses some intact cardiac conduction system.
We experienced a rare case of idiopathic cardiomyopathy that showed a dissociated biphasic wide QRS complex and completely separated RV and LV contractions during RV high-septal pacing due to transversely limited severe transseptal conduction disturbance, despite the presence of a relatively narrow QRS wave during atrium-only pacing. Although RV septal pacing can usually achieve more physiological ventricular contraction than RV apical pacing, it should be noted that even septal pacing could evoke harmful interventricular dyssynchrony.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by Editor-in-Chief of this journal.
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