Interatrial Conduction Measured During Biventricular Pacemaker Implantation Accurately Predicts Optimal Paced Atrioventricular Intervals

Discordant electrical and mechanical atrial delays affect intracavitary electrogram-based cardiac resynchronization therapy optimization

AIMS

It has been shown that atrioventricular (AV) delay optimization improves cardiac resynchronization therapy (CRT) response. Recently, an automatic algorithm (QuickOpt™, St Jude Medical), able to quickly identify the individual optimal AV interval, has been developed. The algorithm suggests an AV delay based on atrial intracavitary electrogram (IEGM) duration. We hypothesized that the difference between electrical and mechanical atrial delays could affect the effectiveness of QuickOpt method. The aim of this study was to test this hypothesis in 23 CRT patients who were recipients of St. Jude Medical devices.

METHODS AND RESULTS

Using echocardiography, aortic flow velocity time integral (VTI) was evaluated at baseline, at QuickOpt suggested AV delay and after reducing it by 25 and 50%. Mechanical inter-atrial delay (MIAD) derived from echo/Doppler and electrical inter-atrial delay (EIAD) derived from IEGM were also analysed. Optimal AV delay was identified by the maximal VTI. In 11 patients (Group 1) the maximal VTI was achieved at the AV delay suggested by the algorithm, in 6 patients (Group 2) after a 25% reduction, and in 6 patients (Group 3) after a 50% reduction. While EIAD was similar among the three groups, MIAD was significantly different (P< 0.001). MIAD was longer than EIAD in Group 1 (P= 0.028) and shorter than EIAD in Groups 2 (P= 0.028) and 3. (P< 0.001). Mechanical inter-atrial delay was the only independent predictor of the AV interval associated with the best VTI (R(2) = 0.77; P< 0.001).

CONCLUSION

Our results show that MIAD plays the main role in determining the optimal AV delay, thus caution should be taken when optimizing AV by IEGM-based methods.

Effect of atrioventricular conduction prolongation on optimization of paced atrioventricular delay for biventricular pacing after cardiac surgery

OBJECTIVES

Atrioventricular conduction prolongation (AVCP) in cardiac pacing is measurable and results primarily from delayed atrial conduction. Noninvasive methods for measuring atrial conduction are lacking. Accordingly, AVCP was used to estimate atrial conduction and investigate its role on the paced atrioventricular delay (pAVD) during biventricular pacing (BiVP) optimization.

DESIGN

Retrospective analysis of data collected as part of a randomized controlled study of temporary BiVP after cardiopulmonary bypass.

SETTING

Single-center study at university-affiliated tertiary care hospital.

PARTICIPANTS

Cardiac surgical patients at risk of left ventricular failure after cardiopulmonary bypass.

INTERVENTIONS

Temporary BiVP was optimized immediately after cardiopulmonary bypass. Vasoactive medication and fluid infusion rates were held constant during optimization.

MEASUREMENTS AND MAIN RESULTS

For each patient the AVCP and the pAVD producing the optimum (highest) cardiac output (OptCO) and mean arterial pressure (OptMAP) were determined. Patients were stratified into long- and short-AVCP groups. Overall AVCP (mean ± standard deviation) was 64 ± 28 ms. For the short-AVCP group (<64 ms, n = 3), AVCP, OptCO, and OptMAP were 40 ± 11, 120 ± 0, and 150 ± 30 ms, respectively, and for the long-AVCP group (>64 ms, n = 4), these same parameters were 89 ± 10, 218 ± 44, and 218 ± 29 ms. OptCO and OptMAP were significantly less in the short-AVCP group (p = 0.015 and p = 0.029, respectively).

CONCLUSIONS

AVCP varies widely after cardiopulmonary bypass, affecting optimum pAVD. Failure to correct for this can result in the selection of inappropriately short and potentially deleterious pAVDs, especially when nominal pAVD is used, causing BiVP to appear ineffective.

Biatrial pacing improves atrial haemodynamics and atrioventricular timing compared with pacing from the right atrial appendage

AIMS

Patients with interatrial conduction delay may have suboptimal left atrioventricular (AV) timing due to delayed contraction of the left atrium with foreshortening of ventricular filling. This may be an issue in pacemaker patients, especially those requiring resychronization therapy. Pacing from the high interatrial septum (IAS) or the distal or proximal coronary sinus (CSD and CSP) may improve left AV synchrony compared with pacing from the right atrial appendage (RAA). Our aim was to compare haemodynamics of these pacing sites.

METHODS AND RESULTS

A total of 24 patients undergoing radiofrequency ablation for paroxysmal atrial fibrillation were studied. Left atrial pressures were recorded in sinus rhythm, and during pacing from the RAA, IAS, CSD, CSP, and with biatrial (BiA) pacing from the IAS + CSD. Amplitudes, +dP/dT(max), and timing of the a-wave were compared between recordings. Left atrial contractility, measured by +dP/dT(max), was greatest during BiA pacing (P ≤ 0.03 for all comparisons). There was a marked reduction in delay to peak a-wave when pacing from all sites compared with the RAA, with BiA pacing yielding the shortest delay (P ≤ 0.001). However, AV conduction was shortened by all alternative pacing sites, which mitigated the anticipation of left atrial contraction with respect to ventricular activation, except for BiA pacing (P < 0.001). Pacing of the IAS did not result in any improvement in haemodynamics or AV synchrony.

CONCLUSION

Multisite atrial pacing results in favourable acute atrial haemodynamics and left AV synchrony. This may be a solution in pacemaker patients with interatrial conduction delay.

Optimization techniques in cardiac resynchronization therapy

Cardiac resynchronization therapy improves symptoms and cardiac function, as well as reduces mortality in patients with progressive congestive heart failure, reduced left ventricular ejection fraction and a left bundle branch block on the surface electrocardiogram. As many as 30% of patients fail to have an adequate response. The interplay between the atrioventricular delay and the contribution of a properly timed atrial contraction to ventricular filling along with a properly timed sequence of activation of the right and left ventricular is crucial to maximizing the benefits of cardiac resynchronization therapy devices.