Potential pro-arrhythmic effect of cardiac resynchronization therapy

A decline in mortality due to pump failure has been clearly documented after cardiac resynchronization therapy [CRT], however the impact on sudden cardiac death and the development of malignant ventricular arrhythmias remains questionable. Our study aims to investigate this alleged pro-arrhythmic effect of CRT using surface electrocardiogram [ECG] markers of pro-arrhythmia. Seventy five patients, who received CRT were included in this study. Manual measurement of corrected QT interval [QTc], T[peak-end] T[p-e] interval, QT dispersion [QTd] and T[peak-end] dispersion during baseline 12 lead surface ECG and after applying atrial-biventricular pacing were done. Arrhythmias post CRT was recorded from ECG, 24 h holter monitoring or pacemaker programmer event recorder. QTc interval showed significant prolongation after CRT [498.9 +/- 50.8 vs. 476.2 +/- 41.6 msec, P = 0.0001]. Comparing patients with major arrhythmogenic events [MAE] and increased frequency of premature ventricular contractions [PVCs] post CRT pacing to those patients without arrhythmias, there was a significant prolongation of the QTc interval [527 +/- 63.29 vs. 496.95 +/- 45.2 msec, P = 0.043] and T p-e interval [94.16 +/- 9 vs. 87.41 +/- 16.37 msec, P = 0.049]. While in the arrhythmogenic group, there was an insignificant decrease in QTd and T[peak-end] dispersion. QTc and T[p-e] intervals are a potential predictor of occurrence of MAE and PVCs. On the other hand, T[p-e] dispersion and QTd did not show a predictive potential for arrhythmia

Are arrhythmias in rheumatic mitral regurgitation common as in mitral valve prolapse in children ?

Rheumatic fever is a common cause of acquired heart disease in children and young adult throughout the developing world and the pancarditis caused by rheumatic fever may manifest by palpitations. Ventricular arrhythmias are a common feature in patients with mitral valve prolapse [MVP] and several factors have been identified in those patients who progress to sudden death, including severe mitral regurgitation. So could arrhythmias in children with rheumatic mitral regurgitation [MR] be as common as in patients with mitral valve prolapse? This study included 30 patients [pts] with isolated rheumatic mitral regurgitation with different grades [mild, moderate and severe mitral regurgitation] diagnosed by echocardiography [group I] compared to group II [control group], which included 30 healthy children with a normal heart confirmed by echocardiography. All the study population was subjected to the following: Full medical history and physical examination, laboratory investigations, twelve leads ECG, chest X-ray, echocardiography and Ambulatory twenty four hours ECG monitoring [Holter]. The total prevalence of arrhythmias detected by Holter monitoring in the studied patients and control group were 40% [12 pts] and 16.6% [5 pts] respectively, p value = 0.04. As regard the type of arrhythmias; sinus tachycardia occurred in 10 pts [33.3%] and 4 pts [13.3%] in group I and II respectively [p value > 0.05]. Infrequent premature atrial contractions [PACs] occurred in 2 pts [6.7%] in group I and one patient [3.3%] in group II [p value > 0.05]. The incidence of arrhythmias detected by Holter recording was insignificant with mild MR compared to the control group [p value = 0.4]. Thereafter, the prevalence of arrhythmias increased proportionally to the degree of MR. The occurrence of arrhythmias in pts with moderate and severe rheumatic MR was significantly higher as compared to the control group [p value = 0.02 and 0.009 -respectively]. The incidence of arrhythmias was not significantly higher in cases of rheumatic MR with active rheumatic fever [4 pts had arrhythmias out of 5 pts with rheumatic activity] than those with rheumatic MR without rheumatic activity [p value = 0.07]. The prevalence of arrhythmias in the patients studied in relation to the echocardiographic findings revealed a significantly higher incidence of arrhythmias in rheumatic MR with left atrial enlargement; eleven out of thirteen pts had sinus tachycardia and PACs [p value = 0.0001]. We conclude from this study that rheumatic mitral regurgitation in the pediatric age group is associated with sinus tachycardia and uncommonly with premature atrial contractions; no other arrhythmias were detected even in association with cardiac enlargement or active carditis. The incidence of arrhythmias in MVP is much more common than in rheumatic MR. Ventricular arrhythmias occurs in MVP, while it did not occur with rheumatic MR in our study. The incidence of arrhythmias in rheumatic MR is significantly related to the severity of mitral regurgitation