Right ventricular septal pacing in patients with right bundle branch block.

BACKGROUND: Cardiac resynchronization therapy (CRT) has been shown to improve left ventricular (LV) function and exercise performance in patients with left bundle branch block. Patients with right bundle branch block (RBBB) do not have a similar positive response to standard CRT. We hypothesized that single site pacing of the right ventricular septum (RVS) near the proximal right bundle could restore more normal activation of the LV in RBBB patients. METHODS: 78 consecutive patients (56 M, 22 F) with baseline RBBB underwent pacemaker or ICD implantation. Leads were placed in the right atrium and RVS. RESULTS: Baseline QRS duration was 120-220 ms (mean QRSd = 147 ms). At the optimal AV delay, the fused QRSd was 56-160 ms (mean QRSd = 112 ms). The mean decrease in QRSd was 34 ± 20.4 ms (p<0.001). CONCLUSION: RVS pacing in patients with RBBB resulted in a marked decrease in QRS duration and often normalized the ECG.

Value of right ventricular-left ventricular interlead electrical delay to predict reverse remodelling in cardiac resynchronization therapy: the INTER-V pilot study.

AIMS: Few studies have systematically evaluated the value of intra-procedural parameters in predicting response to cardiac resynchronization therapy (CRT). We investigated whether intracardiac (electrogram) measurements of electrical delays between the positioned right ventricular (RV) and left ventricular (LV) leads at implantation could predict the mid-term CRT response. METHODS AND RESULTS: Fifty-two patients underwent CRT implantation according to standard techniques and clinical indications. The RV-LV interlead electrical delay measured during spontaneous rhythm and the difference between the pacing-induced (Deltap) RV-LV interlead electrical delays measured during RV and LV pacing were defined intraoperatively using the electrical depolarizations registered at the ventricular leads on the device programmer. At 6 months, a reduction of LV end-systolic volume > or = 15% was used to define CRT responders. Responders (62%), when compared with non-responders, showed a higher proportion of ischaemic aetiology (P = 0.007) and a lower value of DeltapRV-LV interlead electrical delay (22.1 +/- 18.4 vs. 46.3 +/- 15.0 ms, P = 0.0001). At multivariate analysis, the DeltapRV-LV interlead electrical delay was the only independent predictor of response to CRT (P = 0.001). For such a parameter, the receiving operating characteristic curve analysis identified a cut-off value of 42 ms corresponding with the highest accuracy: sensitivity 90.6%; specificity 70%; positive and negative predictive value 83% and 82%, respectively. Conversely, no difference was ascertained between responders and non-responders when RV-LV interlead electrical delay was measured during spontaneous rhythm (76.1 +/- 28.5 vs. 89.6 +/- 21.2, P = 0.078). CONCLUSION: Intraprocedural measuring of paced RV-LV interlead electrical delay obtained during RV and LV pacing predicts mid-term CRT response.

Variability of left ventricular electromechanical activation during right ventricular pacing: implications for the selection of the optimal pacing site.

BACKGROUND: The right ventricular septum (RVS) and Hisian area (HA) are considered more "physiological" pacing sites than right ventricular apex (RVA). Studies comparing RVS to RVA sites have produced controversial results. There are no data about variability of electromechanical activation obtained by an approach using fluoroscopy and electrophysiological markers. This study compared the variability of left ventricular (LV) electromechanical activation in patients undergoing short-term RVA and RVS with that measured during HA pacing based on fluoroscopy and electrophysiological markers. METHODS: Tissue Doppler echocardiography was performed in 142 patients before and after RVA (54), RVS (44), and HA (44) pacing. Electromechanical activation was assessed by: (1) electromechanical latency (EML)-interval between QRS onset and mechanical activation of basal LV; (2) intra-LV dyssynchrony (intra-LV)-interval between earliest to the latest LV basal motion. The intra- and interpatients variability among pacing groups were assessed. RESULTS: Pacing from RVA showed longer EML and higher degree of intra-LV than RVS and HA pacing. RVA and RVS showed a higher variability than HA pacing with regard to intrapatient changes of EML (RVA vs RVS, P = 0.4; RVS vs HA, P = 0.01, RVA vs HA, P = 0.0002) and intra-LV (RVA vs RVS, P = 0.2; RVS vs HA, P = 0.04; RVA vs HA, P = 0.005). Similar results were found in interpatients variability from paced-values. CONCLUSIONS: RVA and RVS pacing produce a variable effect on LV electromechanical activation that is significantly more pronounced than HA pacing. A pacing site such as HA selected by fluoroscopic and electrophysiological markers maintains baseline and homogeneous LV activation pattern.

Determinants of thoracic electrical impedance in external electrical cardioversion of atrial fibrillation.

The success of external cardioversion (ECV) of atrial fibrillation depends on generating sufficient transmyocardial current for defibrillation with minimal myocardial injury. Thoracic electrical impedance plays an important role in the relation between the delivered energy and transmyocardial current. This study assessed the determinants of thoracic electrical impedance in ECV of atrial fibrillation. ECV of atrial fibrillation was performed in 80 consecutive patients (mean age 73 +/- 9 years; men 69%; body mass index 26.0 +/- 3.6 kg/m(2)) within 12 months, using biphasic shocks (Multipulse Biowave) delivered through adhesive pads in an anteroposterior position. Thoracic electrical impedance was measured using the first shock. The mean thoracic electrical impedance was 57.7 +/- 12.3 Omega (energy 71 +/- 43 J, current intensity 33 +/- 12 A). Sinus rhythm was immediately restored in 75 patients (94%). Thoracic electrical impedance was greater (60.9 +/- 11.8 vs 51.7 +/- 11.0 Omega, p = 0.001) in patients requiring >1 shock (65%). At multivariate linear regression analysis (R = 0.761, p <0.001), female gender (+9.7 +/- 2.0 Omega, p <0.001), body mass index (+1.5 +/- 0.3 for a 1 kg/m(2) increase, p <0.001), hemoglobin concentration (+1.9 +/- 0.6 for a 1 g/dl increase, p = 0.004), and the presence of chronic heart failure (-5.3 +/- 2.0 Omega, p = 0.009) were independent predictors of thoracic electrical impedance. In conclusion, to increase ECV efficacy and minimize complications, the delivered energy should be adjusted in accordance with the clinical variables that independently affect thoracic electrical impedance and, hence, transmyocardial current.

Digital technology in cardiac pacing: methods for morphology analysis of sensed endocavitary signals.

UNLABELLED: Proper functioning of a pacemaker depends exclusively on the detection of intrinsic cardiac signals. Conventional devices merely establish the presence of an endocavitary potential, but do not evaluate it qualitatively. The recent incorporation of digital signal processing of sensed events in pacemaker permits diagnostic characterization heretofore impossible. METHODS: Digital processing was used in 268 cardiac cycles recorded from 5 patients during elective dual chamber pacemaker replacement, The signals were classified in real time by an external pacemaker equipped with hardware and software capabilities for this purpose. RESULTS: The parameters used for morphological analysis were the minimum value of the slope signal and the minimum value of the filtered signal. The discrimination of a true atrial signal from a far-field R wave was correct in every patient (p < 0.0001). CONCLUSION: Digital devices may monitor and classify every event continually, and dramatically increase device reliability and the amount of information that can be processed and stored.

Advances in devices for cardiac resynchronization in heart failure.

Patients with advanced heart failure have a high mortality and morbidity despite medical therapy. Depending on the underlying heart disease and severity of heart failure, 3.7 to 52.8% of patients have a QRS complex > or =120 ms who may have interventricular and intraventricular dyssynchrony correctible by cardiac resynchronization therapy (CRT). The latter is usually achieved with biventricular pacing, with the left ventricular lead placed in a tributary of the coronary sinus (CS), with a reported success rate between 88-92%. The technical advances for implantation include preformed guide sheaths to cannulate the CS, over the wire leads with passive fixation mechanism, and surgical placement methods. Device-specific CRT features include optimizing heart failure through insurance of a high percentage of pacing, heart failure monitoring, atrioventricular and interventricular timing, and avoiding double ventricular sensing. Furthermore, arrhythmic co-morbidities of heart failure such as atrial fibrillation and ventricular tachyarrhythmias can also be managed. Recent prospective trials suggest that there is a 30% reduction in heart failure hospitalization with CRT, and preliminary results suggest a survival benefit with CRT and implantable cardioverter defibrillator over optimal medical therapy.

Clinical and angiographic findings of complete atrioventricular block in acute inferior myocardial infarction.

INTRODUCTION: The angiographic findings and prognosis of patients with complete atrioventricular block (AVB) complicating acute inferior myocardial infarction (MI) remain unclear. MATERIALS AND METHODS: The clinical and angiographic findings of 70 consecutive patients with complete AVB were compared with those of 319 patients with inferior MI without AVB (control group) admitted within the same study period. RESULTS: Patients with complete AVB were older (68 +/- 12 vs 63 +/- 13 years; P = 0.004) and clustered with clinical features indicative of larger infarct size, such as right ventricular infarction, cardiogenic shock, or low left ventricular ejection fraction (LVEF). The onset of the complete AVB was observed within 24 hours in 62 (88.6%), preceded by second-degree AVB in 26 (37.1%) and the escape QRS complex was wide in 8 (11.4%) patients. In patients with complete AVB, a dominant right coronary artery occlusion was found in >95% of cases and in-hospital mortality was increased (27.1% vs 10.7%; P = 0.000), especially in those with widen QRS escape rhythm (75.0%). Reperfusion therapy had a positive impact on the natural course of complete AVB. CONCLUSIONS: Complete AVB in acute inferior MI was associated with advanced age and larger infarct size. Complete AVB was virtually always caused by dominant right coronary artery occlusion. The in-hospital mortality was significantly higher, but improved by reperfusion therapy. No permanent pacemaker is performed at a mean follow-up of 47 months.

Sport and arrhythmias: summary of an international symposium.

This article is the report of an International Symposium endorsed by the European Society of Cardiology, held within the Venice Arrhythmias 2007: 10 International Workshop on Cardiac Arrhythmias (Venice, October 2007). The topics of the Symposium are the following: how to stratify the risk of sudden death in athletes; the role of different diagnostic examinations in the risk stratification of sudden death in athletes; controversies on arrhythmias and sport; and exercise prescription in patients with arrhythmias.