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Aims: This study evaluates the relative importance of two components of QRS prolongation, myocardial conduction velocity and travel distance of the electrical wave front (i.e. path length), for the prediction of acute response to cardiac resynchronization therapy (CRT) in left bundle branch block (LBBB) patients.Methods and Results: Thirty-two CRT candidates (ejection fraction <35%, LBBB) underwent cardiac magnetic resonance (CMR) imaging to provide detailed information on left ventricular (LV) dimensions. Left ventricular end-diastolic volume (LVEDV) was used as a primary measure for path length, subsequently QRSd was normalized to LV dimension (i.e. QRSd divided by LVEDV) to adjust for conduction path length. Invasive pressure-volume loop analysis at baseline and during CRT was used to assess acute pump function improvement, expressed as LV stroke work (SW) change. During CRT, SW improved by +38 ± 46% (P < 0.001). The baseline LVEDV was positively related to QRSd (R = 0.36, P = 0.044). Despite this association, a paradoxical inverse relation was found between LVEDV and SW improvement during CRT (R = -0.40; P = 0.025). Baseline unadjusted QRSd was found to be unrelated to SW changes during CRT (R = 0.16; P = 0.383), whereas normalized QRSd (QRSd/LVEDV) yielded a strong correlation with CRT response (R = 0.49; P = 0.005). Other measures of LV dimension, including LV length, LV diameter, and LV end-systolic volume, showed similar relations with normalized QRSd and SW improvement.Conclusion: Since normalized QRSd reflects myocardial conduction properties, these findings suggest that myocardial conduction velocity rather than increased path length mainly determines response to CRT. Normalizing QRSd to LV dimension might provide a relatively simple method to improve patient selection for CRT. [ABSTRACT FROM AUTHOR]

Aims: One-third of dilated cardiomyopathy patients receiving a biventricular pacing-device do not respond to this form of therapy. Therefore, the utility of mechanical dyssynchrony by real-time 3D echocardiography (RT3DE) for predicting systolic response to biventricular pacing, of which maximal rate of pressure rise (dP/dt(max)) served as the gold-standard, was evaluated. Methods and Results: Seventeen consecutive heart failure patients (aged 64 +/- 10 years, 8 male, 6 ischaemic cardiomyopathy, mean QRS duration 136 +/- 32 ms) underwent RT3DE and biventricular pacing. Post-processing software provided data of global left ventricular (LV) function and the systolic dyssynchrony index of 17 LV segments (SDI(17), %) for mechanical dyssynchrony. During biventricular pacing, percentual change in dP/dt(max) compared to the non-pacing mode, DeltadP/dt(max) was measured invasively with conductance catheters. LV ejection fraction was 31 +/- 10%, SDI(17) was 10.2 +/- 4.2% and percentual DeltadP/dt(max) during biventricular pacing was 14.5 +/- 12.4. A significant correlation (r = 0.729, P = 0.001) was found between SDI(17) and percentual DeltadP/dt(max), and between QRS duration and percentual DeltadP/dt(max) (r = 0.721, P = 0.001). Conclusion: The present study suggests that mechanical dyssynchrony measured by RT3DE shows a good correlation with invasively determined acute haemodynamic response to biventricular pacing in patients with symptomatic dilated cardiomyopathy. Future studies are needed to further define the clinical utility of RT3DE in identifying patients who are most likely to respond to cardiac resynchronization therapy. [ABSTRACT FROM AUTHOR]

The right ventricular apex has been used for cardiac stimulation because this position is easily accessible and is associated with a stable position of the electrode with a low dislodgement rate. This position, however, is associated with a dyssynchronous left ventricular contraction with subsequent deleterious haemodynamic effects. Alternative stimulation sites have been studied extensively because of a potentially better haemodynamic effect compared with right ventricular apex pacing.Using a Cochrane search strategy, nine studies were selected to analyze the haemodynamic effects of right ventricular outflow-tract pacing. The results of these studies (n=217) were pooled and indicated a significantly better haemodynamic effect (odds ratio 0.34, confidence interval 0.15–0.53) compared with right ventricular apex pacing. Therefore, these data suggest that right ventricular outflow-tract pacing may offer a modest but significant benefit over right ventricular apex pacing in patients selected for pacemaker implantation on the basis of symptomatic bradyarrhythmias. [ABSTRACT FROM PUBLISHER]

Introduction Atrioventricular sequential pacing involves stimulation from electrodes in the right atrium, generally the atrial appendage (RAA) and the right ventricular apex. The appendage, however, may be unsuitable if a stable position cannot be achieved. The aim of this study was to assess the haemodynamic consequences of different atrial stimulation sites during DDD pacing. Methods In 12 consecutive patients (mean age 67±7 years) who underwent DDD pacemaker implantation, an additional temporary bipolar pacing electrode was positioned on the right atrial free wall. Pacing was performed alternating from the two locations at 85, 100 and 120 beats per minute (bpm). Paced atrioventricular delay was set at 180 ms. Cardiac output and mitral inflow measurements were performed using Doppler echocardiography. Results Pacing at 85 and 100 bpm resulted in a significantly higher A-peak velocity from the RAA compared with the right atrial free wall. Cardiac index was consistently higher from the RAA location (2·4±1·2 vs 2·1± 0·9 l. min−1m−2 at 85 bpm, 2·71±1·4 vs 2·35±1·1 l. min−1m−2 at 100 bpm and 2·94±1·5 vs 2·61±1·4 l. min−1m−2 at 120 bpm, P<0·05). Conclusion Stimulation from the RAA was superior to stimulation from the right atrial free wall with respect to left ventricular filling and cardiac output. Compared with stimulation from the right atrial free wall, RAA pacing resulted in an increase of 10–15% in cardiac output. [ABSTRACT FROM PUBLISHER]

A 74-year-old patient was referred for a rapidly increasing pacing threshold 9 months after DDD pacemaker implantation because of symptomatic total atrioventricular (AV) block. She had a history of hypertension, diabetes with micro-angiopathy and a recent transient ischaemic attack.The paced electrocardiogram on admission had a right bundle branch block pattern and 3-dimensional transoesophageal echocardiography demonstrated passage of the lead through an atrial septal defect with a left ventricular position in addition to moderate atherosclerosis of the ascending aorta. No thrombus could be detected on the lead. Percutaneous extraction is usually not recommended because of the risk of mobilization of thrombus material. However, the risk of stroke during removal using cardiopulmonary bypass in this patient was considerably increased because of the presence of multiple independent risk factors. Therefore, percutaneous extraction using a locking device was selected and performed without complications: follow-up was uneventful. [ABSTRACT FROM PUBLISHER]

In a patient admitted with symptomatic complete heart block, a DDD pacemaker was implanted. Prior to implantation, echocardiography showed normal left ventricular function. Shortly after implantation, acute congestive heart failure developed with extensive regional hypo- and akinetic segments in the anteroseptal, anterolateral and apical region. Subsequent perfusion imaging with methoxyiso-buticeisonitrite (MIBI) at rest demonstrated hypoperfusion in the same regions while coronary angiography showed normal epicardial coronary vessels. Thus, impaired regional coronary flow can be associated with cardiac stimulation, inducing marked deterioration of left ventricular function. [ABSTRACT FROM PUBLISHER]