Alternative pacing strategies for optimal cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) via biventricular pacing (BVP) improves morbidity, mortality, and quality of life, especially in subsets of patients with impaired cardiac function and wide QRS. However, the rate of unsuccessful or complicated left ventricular (LV) lead placement through coronary sinus is 5-7%, and the rate of "CRT non-response" is approximately 30%. These reasons have pushed physicians and engineers to collaborate to overcome the challenges of LV lead implantation. Thus, various alternatives to BVP have been proposed to improve CRT effectiveness. His bundle pacing (HBP) has been increasingly used by activating the His-Purkinje system but is constrained by challenging implantation, low success rates, high and often unstable thresholds, and low perception. Therefore, the concept of pacing a specialized conduction system distal to the His bundle to bypass the block region was proposed. Multiple clinical studies have demonstrated that left bundle branch area pacing (LBBAP) has comparable electrical resynchronization with HBP but is superior in terms of simpler operation, higher success rates, lower and stable capture thresholds, and higher perception. Despite their well-demonstrated effectiveness, the transvenous lead-related complications remain major limitations. Recently, leadless LV pacing has been developed and demonstrated effective for these challenging patient cohorts. This article focuses on the current state and latest progress in HBP, LBBAP, and leadless LV pacing as alternatives for failed or non-responsive conventional CRT as well as their limits and prospects.

Comparison of left ventricular with right ventricular rapid pacing on tamponade during TAVI.

BACKGROUND: Small studies have suggested left ventricular (LV) rapid pacing has similar safety and efficacy to conventional right ventricular (RV) rapid pacing in transcatheter aortic valve implantation (TAVI). However, there are limited data on the comparative rates of tamponade. The study compared the rate of cardiac tamponade between LV and RV-pacing during TAVI. METHODS: Between 2008 and 2021, 1226 consecutive patients undergoing transfemoral or transaxillary TAVI were included. 470(38.3%) patients had TAVI deployment with RV-pacing and 756(61.7%) with LV-pacing. The primary outcome was the frequency and cause of cardiac tamponade. Secondary outcomes included efficacy, procedure duration and crossover rates. RESULTS: There was a trend to less tamponade with LV-pacing, which did not reach statistical significance [11(2.3%) vs 11(1.5%);P = 0.27]. There was no significant difference in the frequency of tamponade due to annular tear [4(0.9%) vs 9(1.2%);P = 0.59] or LV free-wall perforation [1(0.2%) vs 2(0.3%);P = 0.86]. The frequency of tamponade due to RV perforation was significantly lower in the LV-pacing group [0 vs 6(2.3%);P < 0.005)]. Two patients with tamponade due to RV perforation required emergency sternotomy of whom one died. Deployment success was similar (99% vs 99.6%;P=NS). Procedure duration was shorter with LV-pacing (70 vs 80 mins;P < 0.005). Crossover to RV-pacing was low (0.9%). There were no embolizations caused by loss-of-capture in either group. CONCLUSIONS: LV-pacing appears equally efficacious and is associated with a lower risk of tamponade due to RV perforation caused by the temporary pacing wire. LV-pacing was not associated with an increased risk of tamponade due to LV free-wall perforation.

Economic implications of adding a novel algorithm to optimize cardiac resynchronization therapy: rationale and design of economic analysis for the AdaptResponse trial.

AIMS: Although cardiac resynchronization therapy (CRT) has proven beneficial in several randomized trials, a subset of patients have limited clinical improvement. The AdaptivCRT algorithm provides automated selection between synchronized left ventricular or biventricular pacing with optimization of atrioventricular delays. The rationale and design of the economic analysis of the AdaptResponse clinical trial are described. RATIONALE: The costs associated with HF hospitalization are substantial and are compounded by a high rate of readmission. HF hospitalization payments range from $1,001 for Greece to $12,235 for US private insurance. When examining the breakdown of HF-related costs, it is clear that approximately 55% of the hospitalization costs are directly attributable to length of stay. Notably, the mean costs of a CRT patient in need of a HF-related hospitalization are currently estimated to be an average of $10,679. METHODS: The economic analysis of the AdaptResponse trial has two main objectives. The hospital provider objective seeks to test the hypothesis that AdaptivCRT reduces the incidence of all-cause re-admissions after a heart failure admission within 30 days of the index event. A negative binomial regression model will be used to estimate and compare the number of readmissions after an index HF hospitalization. The payer economic objective will assess cost-effectiveness of CRT devices with the AdaptivCRT algorithm relative to traditional CRT programming. This analysis will be conducted from a U.S. payer perspective. A decision analytic model comprised of a 6-month decision tree and a Markov model for long term extrapolation will be used to evaluate lifetime costs and benefits. CONCLUSION: AdaptivCRT may offer improvements over traditional device programming in patient outcomes. How the data from AdaptResponse will be used to demonstrate if these clinical benefits translate into substantial economic gains is herein described.

Left ventricular pacing induced polymorphic ventricular tachycardia via the adaptive left ventricle pacing algorithm.

Providers should be aware of the possibility of cardiac resynchronization therapy-related proarrhythmia which could be life-threatening. His-bundle pacing may serve as an alternative, more physiological, option in the management as it preserves the normal sequence of depolarization from the septum to the lateral wall, and from endocardium to epicardium.

Differences in clinical characteristics and reported quality of life of men and women undergoing cardiac resynchronization therapy.

AIMS: Response to cardiac resynchronization therapy (CRT) is known to be associated with a number of clinical characteristics, including QRS duration and morphology, gender, height, and the aetiology of heart failure (HF). We assessed the relation of gender and baseline characteristics with QRS duration and Kansas City Cardiomyopathy Questionnaire. METHODS AND RESULTS: AdaptResponse is a global randomized trial. The trial enrolled CRT-indicated patients with New York Heart Association classes II-IV HF, left bundle branch block (QRS ≥ 140 ms in men, ≥130 ms in women), and baseline PR interval ≤200 ms. In total, 3620 patients were randomized, including 1569 women (43.3%) approaching the actual proportion of women in the HF population. Women were older and more often New York Heart Association class III or IV than men (55.6% vs. 48.7%), had less frequent ischaemic cardiomyopathy (21.2% vs. 39.5%), and had a 5.1 ms shorter QRS duration than men. Women were more often depressed (18.5% vs. 9.7%), had a significantly lower Kansas City Cardiomyopathy Questionnaire score, and had differences in medication prescriptions. CONCLUSIONS: AdaptResponse is the largest randomized CRT trial and enrolled more women than any other landmark CRT trial. Women differed from men with regard to baseline characteristics and quality of life. Whether these differences translate into clinical outcome differences will be examined further in the AdaptResponse trial.

Continuous optimization of cardiac resynchronization therapy reduces atrial fibrillation in heart failure patients: Results of the Adaptive Cardiac Resynchronization Therapy Trial.

BACKGROUND: Data from randomized trials have suggested a modest or no effect of conventional cardiac resynchronization therapy (convCRT) on the incidence of atrial fibrillation (AF). AdaptivCRT (aCRT, Medtronic, Mounds View, MN) is a recently described algorithm for synchronized left ventricular (LV) pacing and continuous optimization of cardiac resynchronization therapy (CRT). OBJECTIVE: We compared the long-term effects of aCRT with convCRT pacing on the incidence of AF. METHODS: The Adaptive CRT trial randomized CRT-defibrillator (CRT-D)-indicated patients (2:1) to receive either aCRT or convCRT pacing. The aCRT algorithm evaluates intrinsic conduction every minute, providing LV-only pacing during normal atrioventricular (AV) conduction and AV and ventriculoventricular timing adjustments during prolonged AV conduction. The primary outcome of this subanalysis was an episode of AF >48 consecutive hours as detected by device diagnostics. RESULTS: Over a follow-up period with a mean and standard deviation of 20.2 ± 5.9 months, 8.7% of patients with aCRT and 16.2% with convCRT experienced the primary outcome (hazard ratio [HR] = 0.54; 95% confidence interval [CI] = 0.31-0.93; P = .03). In patients with prolonged baseline AV, the incidence of the primary outcome was 12.8% in patients randomized to aCRT compared with 27.4% in convCRT patients (HR = 0.45; 95% CI = 0.24-0.85; P = .01). Also, patients with AF episodes adjudicated as clinical adverse events were less common with aCRT (4.3%) than with convCRT (12.7%) (HR = 0.39; 95% CI = 0.19-0.79; P = .01). CONCLUSION: Patients receiving aCRT had a reduced risk of AF compared with those receiving convCRT. Most of the reduction in AF occurred in subgroups with prolonged AV conduction at baseline and with significant left atrial reverse remodeling.

DDD pacemaker for severe heart failure-alternate to CRT.

Patients with severe systolic Heart Failure continue to have poor quality of life and increased mortality in spite of optimal medical management. Cardiac Resynchronization Therapy [CRT] is promising modality in patients with systolic heart failure and electrocardiographic [ECG] evidence of left bundle branch block [LBBB]. Cost issues continue to elude many deserving cases of this therapy in our society. Relatively cost effective Dual chamber pacing [DDD] with right atrial and isolated left ventricular pacing [RA-LV] can be a good alternative.

Influence of automatic frequent pace-timing adjustments on effective left ventricular pacing during cardiac resynchronization therapy.

AIMS: Cardiac resynchronization therapy (CRT) requires effective left ventricular (LV) pacing (i.e. sufficient energy and appropriate timing to capture). The AdaptivCRT™ (aCRT) algorithm serves to maintain ventricular fusion during LV or biventricular pacing. This function was tested by comparing the morphological consistency of ventricular depolarizations and percentage effective LV pacing in CRT patients randomized to aCRT vs. echo-optimization. METHODS AND RESULTS: Continuous recordings (≥20 h) of unipolar LV electrograms from aCRT (n = 38) and echo-optimized patients (n = 22) were analysed. Morphological consistency was determined by the correlation coefficient between each beat and a template beat. Effective LV pacing of paced beats was assessed by algorithmic analysis of negative initial EGM deflection in each evoked response. The %CRT pacing delivered, %effective LV pacing (i.e. % of paced beats with effective LV pacing), and overall %effective CRT (i.e. product of %CRT pacing and %effective LV pacing) were compared between aCRT and echo-optimized patients. Demographics were similar between groups. The mean correlation coefficient between individual beats and template was greater for aCRT (0.96 ± 0.03 vs. 0.91 ± 0.13, P = 0.07). Although %CRT pacing was similar for aCRT and echo-optimized (median 97.4 vs. 98.6%, P = 0.14), %effective LV pacing was larger for aCRT [99.6%, (99.1%, 99.9%) vs. 94.3%, (24.3%, 99.8%), P=0.03]. For aCRT vs. echo-optimized groups, the proportions of patients with ≥90% effective LV pacing was 92 vs. 55% (P = 0.002), and with ≥90% effective CRT was 79 vs. 45%, respectively (P = 0.018). CONCLUSION: AdaptivCRT™ significantly increased effective LV pacing over echo-optimized CRT.

Automated detection of effective left-ventricular pacing: going beyond percentage pacing counters.

AIMS: Cardiac resynchronization therapy (CRT) devices report percentage pacing as a diagnostic but cannot determine the effectiveness of each paced beat in capturing left-ventricular (LV) myocardium. Reasons for ineffective LV pacing include improper timing (i.e. pseudofusion) or inadequate pacing output. Device-based determination of effective LV pacing may facilitate optimization of CRT response. METHODS AND RESULTS: Effective capture at the LV cathode results in a negative deflection (QS or QS-r morphology) on a unipolar electrogram (EGM). Morphological features of LV cathode-RV coil EGMs were analysed to develop a device-based automatic algorithm, which classified each paced beat as effective or ineffective LV pacing. The algorithm was validated using acute data from 28 CRT-defibrillator patients. Effective LV pacing and pseudofusion was simulated by pacing at various AV delays. Loss of LV capture was simulated by RV-only pacing. The algorithm always classified LV or biventricular (BV) pacing with AV delays ≤60% of patient's intrinsic AV delay as effective pacing. As AV delays increased, the percentage of beats classified as effective LV pacing decreased. Algorithm results were compared against a classification truth based on correlation coefficients between paced QRS complexes and intrinsic rhythm QRS templates from three surface ECG leads. An average correlation >0.9 defined a classification truth of ineffective pacing. Compared against the classification truth, the algorithm correctly classified 98.2% (3240/3300) effective LV pacing beats, 75.8% (561/740) of pseudofusion beats, and 100% (540/540) of beats with loss of LV capture. CONCLUSION: A device-based algorithm for beat-by-beat monitoring of effective LV pacing is feasible.

The roles of the Q (q) wave in lead I and QRS frontal axis for diagnosing loss of left ventricular capture during cardiac resynchronization therapy.

INTRODUCTION: Loss of left ventricular (LV) capture may lead to deterioration of heart failure in patients with cardiac resynchronization therapy (CRT). Recognition of loss of LV capture in time is important in clinical practice. METHODS AND RESULTS: A total of 422 electrocardiograms were acquired and analyzed from 53 CRT patients at 8 different pacing settings (LV only, right ventricle [RV] only, biventricular [BV] pacing with LV preactivation of 60, 40, 20, and 0 milliseconds and RV preactivation of 20 and 40 milliseconds). A modified Ammann algorithm by adding a third step-presence of Q (q, or QS) wave-to the original 2-step Ammann algorithm and a QRS axis shift method were devised to identify the loss of LV capture. The accuracy of modified Ammann algorithm was significantly higher than that of Ammann algorithm (78.9% vs. 69.1%, P < 0.001). The accuracy of the axis shift method was 66.4%, which was significantly lower than the modified Ammann algorithm (P < 0.001) and similar to the original one (P = 0.412). However, in the ECGs with QRS axis shift, 96.8% were correctly classified. LV preactivation or simultaneous BV activation and LV lead positioned in nonposterior or noninferior wall could elevate the accuracies of the modified Ammann algorithm and the QRS axis shift method. CONCLUSIONS: The accuracy of the modified Ammann algorithm is greatly improved. The QRS axis shift method can help diagnose LV capture. The LV preactivation, or simultaneous BV activation and LV lead positioned in nonposterior or noninferior wall can increase the diagnostic power of the modified Ammann algorithm and QRS axis shift method.