R-wave synchronised atrial pacing in pediatric patients with postoperative junctional ectopic tachycardia: the atrioventricular interval investigated by computational analysis and clinical evaluation.

BACKGROUND: R-wave synchronised atrial pacing is an effective temporary pacing therapy in infants with postoperative junctional ectopic tachycardia. In the technique currently used, adverse short or long intervals between atrial pacing and ventricular sensing (AP-VS) may be observed during routine clinical practice. OBJECTIVES: The aim of the study was to analyse outcomes of R-wave synchronised atrial pacing and the relationship between maximum tracking rates and AP-VS intervals. METHODS: Calculated AP-VS intervals were compared with those predicted by experienced pediatric cardiologist. RESULTS: A maximum tracking rate (MTR) set 10 bpm higher than the heart rate (HR) may result in undesirable short AP-VS intervals (minimum 83 ms). A MTR set 20 bpm above the HR is the hemodynamically better choice (minimum 96 ms). Effects of either setting on the AP-VS interval could not be predicted by experienced observers. In our newly proposed technique the AP-VS interval approaches 95 ms for HR > 210 bpm and 130 ms for HR < 130 bpm. The progression is linear and decreases strictly (- 0.4 ms/bpm) between the two extreme levels. CONCLUSIONS: Adjusting the AP-VS interval in the currently used technique is complex and may imply unfavorable pacemaker settings. A new pacemaker design is advisable to allow direct control of the AP-VS interval.

Left ventricular asynchrony in patients with right bundle branch block and normal ejection fraction.

AIMS: The role of right bundle branch block (RBBB) for the induction of left ventricular (LV) asynchrony is discussed controversially. The objective of this study was to assess presence and degree of LV asynchrony in patients with RBBB, left bundle branch block (LBBB), or left anterior hemiblock (LAH) and normal LV function. METHODS: We included 15 patients with RBBB, 13 patients with RBBB and concomitant LAH, 10 patients with pure LBBB, and 100 healthy controls into this study. All patients had normal LV function. Interventricular asynchrony was assessed as the difference of the right and LV ejection delay. Intraventricular delay was obtained by tissue synchronicity imaging-guided tissue Doppler imaging measurement. RESULTS: Interventricular and left intraventricular asynchrony were linked to the presence of an LBBB. No left intraventricular asynchrony was noted during pure RBBB; interventricular delays were negative (aortic flow preceding pulmonary flow) in the presence of RBBB. CONCLUSION: In patients with normal LV function, intraventricular asynchrony depends on the presence of an LBBB and interventricular asynchrony is inversed in the presence of RBBB.

Transesophageal left ventricular electrogram-recording and temporary pacing to improve patient selection for cardiac resynchronization.

Cardiac resynchronization therapy (CRT) with biventricular pacing (BV) is an established therapy for heart failure (HF) patients with inter- and intraventricular conduction delay. The aim of this pilot study was to test the feasibility of both transesophageal measurement of left ventricular (LV) electrical delay and transesophageal LV pacing prior to implantation, to better select patients for CRT. Esophageal TO8 Osypka catheter was perorally applied in 30 HF patients in position of maximum LV deflection to measure LV electrical delay and to study arterial pulse pressure (PP) during transesophageal bipolar LV pacing. There were 15 responders with a PP increase of a mean 65 ± 24 mmHg to 79 ± 27 mmHg (P < 0.001) and a mean LV electrical delay of 86.8 ± 33 ms. The 15 non-responders with poor PP increase of a mean 63.5 ± 23.5 mmHg to 64.1 ± 23.9 mmHg (P = 0.065) had a significantly smaller LV electrical delay of 36 ± 21 ms (P < 0.001). During a 34 ± 26 month CRT follow-up, the responders New York Heart Association (NYHA) class improved from 3.1 ± 0.35 to 2.1 ± 0.35 (P < 0.001). Determination of left ventricular electrical delay by transesophageal electrogram recording and transesophageal left ventricular pacing may be additional useful techniques to improve patient selection for CRT.

A modified echocardiographic protocol with intrinsic plausibility control to determine intraventricular asynchrony based on TDI and TSI.

BACKGROUND: Established methods to determine asynchrony suffer from high intra- and interobserver variability and failed to improve patient selection for cardiac resynchronization therapy (CRT). Thus, there is a need for easy and robust approaches to reliably assess cardiac asynchrony. METHODS AND RESULTS: We performed echocardiography in 100 healthy subjects and 33 patients with left bundle branch block (LBBB). To detect intraventricular asynchrony, we combined two established methods, i.e., tissue synchronization imaging (TSI) and tissue Doppler imaging (TDI). The time intervals from the onset of aortic valve opening (AVO) to the peak systolic velocity (S') were measured separately in six basal segments in the apical four-, two-, and three-chamber view. Color-coded TSI served as an intrinsic plausibility control and helped to identify the correct S' measuring point in the TDI curves. Next, we identified the segment with the shortest AVO-S' interval. Since this segment most likely represents vital and intact myocardium it served as a reference for other segments. Segments were considered asynchronous when the delay between the segment in question and the reference segment was above the upper limit of normal delays derived from the control population. Intra- and interobserver variability were 7.0% and 7.7%, respectively. CONCLUSION: Our results suggest that combination of TDI and TSI with intrinsic plausibility control improves intra- and interobserver variability and allows easy and reliable assessment of cardiac asynchrony.

Should we use the rate-adaptive AV delay in cardiac resynchronization therapy-pacing?

AIMS: Recommendations for programming the rate-adaptive AV delay in CRT. METHODS AND RESULTS: In cases of continual biventricular pacing, the optimal AV delay in CRT (AVD(opt)) is the net effect of the pacemaker-related interatrial conduction time (IACT), duration of the left-atrial electromechanical action (LA-EAC(long)), and the duration of the left-ventricular latency period (S(V)-EAC(short)). It can be calculated by AVD(opt) = IACT+LA-EAC(long)-S(V)-EAC(short). We measured these three components in 20 CRT-ICD patients during rest and submaximal ergo metric exercise (71 +/- 9 W) resulting in a 22.5 +/- 9.6 bpm rate increase. IACT and S(V)-EAC(short) did not reveal significant differences. LA-EAC(long), however, varied significantly by -10.7 +/- 16.1 ms (P = 0.008) during exercise. In contrast to AVD(optVDD), there was a significant difference in AVD(optDDD) of -8.8 +/- 14.5 ms (P = 0.014) between the resting and submaximal exercise conditions. In DDD pacing, AVD(opt) was shortened by 2.6 ms/10 bpm. CONCLUSION: In consideration of the findings of the studies performed to date, the rate-adaptive AV delay should be deactivated.

How can the rate-adaptive atrioventricular delay be programmed in atrioventricular block pacing?

AIM: To optimize recommendations for programming of the rate-adaptive atrioventricular (AV) delay. METHODS AND RESULTS: Optimal AV delay (AVD(opt)) is the net effect of the pacemaker-related interatrial conduction time (IACT), duration of the left-atrial electromechanical action (LA-EAC(long)) and duration of left-ventricular latency (S(V)-EAC(short)). It can be calculated by AVD(opt) = IACT + LA-EAC(long)-S(V)-EAC(short). We measured these three components in 20 DDD pacemaker patients (EF >45%) with the third degree AV block (AVB) at rest and submaximal ergometric exercise load of 71 +/- 9 W which resulted in a 31.5 +/- 9.9 bpm rate increase. Between exercise and rest, the components of and the final AVD(opt) showed no significant differences. Interatrial conduction time in VDD and DDD pacing varied by 2.3 +/- 8.4 ms and 1.4 +/- 8.8 ms, respectively, S(V)-EAC(short) changed by -2.6 +/- 21.8 ms and AVD(opt) by -3.5 +/- 33.3 ms and -4.3 +/- 37.8 ms in VDD and DDD operation, respectively. The greatest variation was of LA-EAC(long) by -8.4 +/- 32.7 ms. Linear regressions of the rate-dependent variations (Deltaf) in VDD operation yielded DeltaIACT(f) = 0.04Deltaf + 0.95 ms, DeltaLA-EAC(long) = -0.59Deltaf + 10.1 ms, and DeltaS(V) - EAC(short) = 0.14Deltaf -7.2 ms which resulted in DeltaAVD(opt) = -0.69Deltaf + 18.2 ms. CONCLUSION: A recommendation for programming of rate-adaptive AV delay in AV block patients cannot be given.

Influence of the atrio-ventricular delay optimization on the intra left ventricular delay in Cardiac Resynchronization Therapy.

BACKGROUND: Cardiac Resynchronization Therapy (CRT) leads to a reduction of left-ventricular dyssynchrony and an acute and sustained hemodynamic improvement in patients with chronic heart failure. Furthermore, an optimized AV-delay leads to an improved myocardial performance in pacemaker patients. The focus of this study is to investigate the acute effect of an optimized AV-delay on parameters of dyssynchrony in CRT patients. METHOD: 11 chronic heart failure patients with CRT who were on stable medication were included in this study. The optimal AV-delay was defined according to the method of Ismer (mitral inflow and trans-oesophageal lead). Dyssynchrony was assessed echocardiographically at three different settings: AVDOPT; AVDOPT-50 ms and AVDOPT+50 ms. Echocardiographic assessment included 2D- and M-mode echo for the assessment of volumes and hemodynamic parameters (CI, SV) and LVEF and tissue Doppler echo (strain, strain rate, Tissue Synchronisation Imaging (TSI) and myocardial velocities in the basal segments) RESULTS: The AVDOPT in the VDD mode (atrially triggered) was 105.5 +/- 38.1 ms and the AVDOPT in the DDD mode (atrially paced) was 186.9 +/- 52.9 ms. Intra-individually, the highest LVEF was measured at AVDOPT. The LVEF at AVDOPT was significantly higher than in the AVDOPT-50 setting (p = 0.03). However, none of the parameters of dyssynchrony changed significantly in the three settings. CONCLUSION: An optimized AV delay in CRT patients acutely leads to an improved systolic left ventricular ejection fraction without improving dyssynchrony.