How Should Echocardiography Be Used in CRT Optimization?

Cardiac Resynchronization Therapy Response Assessment with Electromechanical Activation Mapping within 24 Hours of Device Implantation: A Pilot Study

BACKGROUND

Cardiac resynchronization therapy (CRT) response assessment relies on the QRS complex narrowing criterion. Yet one third of patients do not improve despite narrowed QRS after implantation. Electromechanical wave imaging (EWI) is a quantitative echocardiography-based technique capable of noninvasively mapping cardiac electromechanical activation in three dimensions. The aim of this exploratory study was to investigate the EWI technique, sensitive to ventricular dyssynchrony, for informing CRT response on the day of implantation.

METHODS

Forty-four patients with heart failure with left bundle branch block or right ventricular (RV) paced rhythm and decreased left ventricular ejection fraction (LVEF; mean, 25.3 ± 9.6%) underwent EWI without and with CRT within 24 hours of device implantation. Of those, 16 were also scanned while in left ventricular (LV) pacing. Improvement in LVEF at 3-, 6-, or 9-month follow-up defined (1) super-responders (ΔLVEF ≥ 20%), (2) responders (10% ≤ ΔLVEF < 20%), and (3) nonresponders (ΔLVEF ≤ 5%). Three-dimensionally rendered electromechanical maps were obtained under RV, LV, and biventricular CRT pacing conditions. Mean RV free wall and LV lateral wall activation times were computed. The percentage of resynchronized myocardium was measured by quantifying the percentage of the left ventricle activated within 120 msec of QRS onset. Correlations between percentage of resynchronized myocardium and type of CRT response were assessed.

RESULTS

LV lateral wall activation time was significantly different (P ≤ .05) among all three pacing conditions in the 16 patients: LV lateral wall activation time with CRT in biventricular pacing (73.1 ± 17.6 msec) was lower compared with LV pacing (89.5 ± 21.5 msec) and RV pacing (120.3 ± 17.8 msec). Retrospective analysis showed that the percentage of resynchronized myocardium with CRT was a reliable response predictor within 24 hours of implantation for significantly (P ≤ .05) identifying super-responders (n = 7; 97.7 ± 1.9%) from nonresponders (n = 17; 89.9 ± 9.9%).

CONCLUSION

Electromechanical activation mapping constitutes a valuable three-dimensional visualization tool within 24 hours of implantation and could potentially aid in the timely assessment of CRT response rates, including during implantation for adjustment of lead placement and pacing outcomes.

Cardiac resynchronization therapy reprogramming to improve electrical synchrony in patients with existing devices

BACKGROUND

Optimal programming of cardiac resynchronization therapy (CRT) has not yet been fully elucidated. A novel algorithm (SyncAV) has been developed to improve electrical synchrony by fusion of the triple wavefronts: intrinsic, right ventricular (RV)-paced, and left ventricular (LV)-paced.

METHODS

Consecutive patients at a single tertiary care center with a previously implanted CRT device with SyncAV algorithm (programmable negative AV hysteresis) were evaluated. QRS duration (QRSd) was measured during 1) intrinsic conduction, 2) existing CRT pacing as chronically programmed by treating physician, 3) using the device-based QuickOpt™ algorithm for optimization of AV and VV delays, and 4) ECG-based optimized SyncAV programming. The paced QRSd was assessed and compared to intrinsic conduction and between the different modes of programming.

RESULTS

Of 64 consecutive, potentially eligible patients who underwent assessment, 34 patients who were able to undergo SyncAV programming were included. Mean intrinsic conduction QRSd was 163 ± 24 ms. In comparison, the mean QRSd was 152 ± 25 ms (-11.1 ± 19.0) during existing CRT pacing, 160 ± 25 ms (-4.1 ± 25.2) using the QuickOpt™ algorithm and 138 ± 23 (-24.9 ± 17.2) using ECG-based optimized SyncAV programming. SyncAV optimization resulted in significant reductions in QRSd compared to existing CRT pacing (P = 0.02) and QuickOpt™ (P < 0.001). Of the 32% of patients who did not have QRS narrowing with existing CRT, 72% experienced QRS narrowing with SyncAV.

CONCLUSION

ECG-based atrio-ventricular delay optimization using SyncAV significantly improved electrical synchrony in patients with a previously implanted CRT. Further studies are needed to assess the impact on long-term outcomes.

Fingertip Reactive Hyperemia Peripheral Arterial Tonometry Score Predicts Response to Biventricular Pacing

Purpose

The objectives of this study were to: (i) evaluate endothelial function via fingertip reactive hyperemia peripheral arterial tonometry (RH-PAT) among heart failure (HF) patients receiving cardiac resynchronization therapy (CRT), (ii) assess the effects of CRT on RH-PAT score, and (iii) investigate whether RH-PAT score can identify CRT response.

Methods

A total of 63 patients (61.8 ± 10.3 years; 50 males; left ventricular (LV) ejection fraction 24.3 ± 3.9%) with HF who received CRT were enrolled. Endothelial function via RH-PAT was assessed 1 day before and 6 months after CRT. Minnesota Living with Heart Failure Questionnaire (MLWHFQ) was used to assess clinical improvements. CRT response was defined as a reduction in LV end-systolic volume ≥ 15% at 6 months.

Results

A RH-PAT score of < 1.7 signified a cut-off for endothelial dysfunction (ED). Baseline ED was observed among 43 (68.3%) patients and was more prevalent in responders (76.1% vs. 47.1%, p = 0.037). RH-PAT score improved 6 months after CRT (1.58 ± 0.35 vs. 1.71 ± 0.31, p = 0.012). A RH-PAT score of < 1.7 was a significant independent predictor of CRT response in multivariate logistic regression analysis (β = 1.275, OR = 3.512, 95% CI = 1.231-11.477, p = 0.032). The severity of ED was an independent predictor of LV reverse remodeling (β = -8.873, p = 0.015). Spearman's correlation analysis revealed moderate positive correlations between an improvement in RH-PAT (ΔRH-PAT) and LV reverse remodeling (r = 0.461, p = 0.001) and MLWHFQ score (r = 0.440, p = 0.001).

Conclusions

ED detected via RH-PAT could predict the response to CRT. The RH-PAT score increased 6 months after CRT and was correlated with echocardiographic and clinical improvements.