Cardiac Resynchronization Therapy and AV Optimization: A Hemodynamic Evaluation with Non-Invasive Techniques

Contemporary and future trends in cardiac resynchronization therapy to enhance response

Usefulness of Atrioventricular Delay Optimization Using Doppler Assessment of Mitral Inflow in Patients Undergoing Cardiac Resynchronization Therapy

Atrioventricular optimization improves cardiac resynchronization response in patients with long interventricular electrical delays: A pooled analysis of the SMART-AV and SMART-CRT trials

Cardiac resynchronization therapy (CRT) is an exciting advance for heart failure patients. As a result of a wealth of evidence from randomized clinical trials, guidelines for selecting patients for CRT have been established, including New York Heart Association functional class III or IV on optimal medical therapy, QRS width ≥120 ms, and ejection fraction ≤35%.1,2 The landmark Multicenter InSync Randomized Clinical Evaluation (MIRACLE) trial published in 2002 reported a 67% improvement in the group randomized to CRT using a clinical composite score in which patients were judged to be improved, unchanged, or worsened.1 Interestingly, the very recent Frequent Optimization Study Using the QuickOpt Method (FREEDOM) trial, designed to assess strategies for atrioventricular (AV) and interventricular (VV) interval optimization, reported a 67.5% improvement after CRT using the same clinical composite score.3 Despite tremendous advances in knowledge and experience with CRT, the proportion of patients considered clinical nonresponders has remained at one third over the last 8 years. Puzzling questions remain: Why are there nonresponders to CRT? Can we improve on current patient selection for CRT to reduce nonresponders? The important article by Delgado et al4 in this issue finds some pieces of the puzzle of nonresponse by focusing on a large series of patients with ischemic heart failure. They reported that mortality and heart failure hospitalizations after CRT in patients with routine indications are associated with dyssynchrony, left ventricular (LV) lead position, and estimates of regional scar. It is worthwhile to consider these factors individually, in combination, and in context of other variables that may influence response to CRT (the Figure). Figure. The puzzle of nonresponse to CRT. Article see p 70 There is an abundance of data to support dyssynchrony as the major pathological derangement associated with mechanical inefficiency and deleterious biological effects that …

Cardiac resynchronization therapy (CRT) is a well-established therapy to reduce morbidity and mortality in patients with moderate and severe symptomatic congestive heart failure. Left ventricular (LV) pacing that fuses with intrinsic right ventricular (RV) conduction results in similar or even better cardiac performance compared to biventricular (Biv) pacing. Optimal programming of the atrio-ventricular (AV) and inter-ventricular (VV) delays is crucial to improve LV performance since suboptimal programming of AV and VV delays affect LV filling as well as cardiac output. CRT optimization using echocardiogram is resource-dependent and time consuming. Adaptive CRT (aCRT) algorithm provides a dynamic, automatic, ambulatory adjustment of CRT pacing configuration (Biv or LV pacing) and optimization of AV and VV delays. aCRT algorithm is safe and efficacious for CRT-indicated patients without permanent atrial fibrillation. It has been shown to improve CRT response and reduce morbidity and mortality for patients with normal AV conduction.

We hypothesized that left atrial pressure (LAP) obtained by a permanent implantable sensor is sensitive to changes in cardiac resynchronization therapy (CRT) settings and could guide CRT optimization to improve the response rate. We investigated the effect of CRT optimization on LAP and its waveform parameters in ambulant heart failure (HF) patients. CRT optimization was performed in eight ambulant HF patients, using echocardiography as reference. LAP waveform was acquired at each of eight atrioventricular (AV) intervals and five inter-ventricular (VV) intervals. Selected waveform parameters were also evaluated for their sensitivity to CRT changes and agreement with echocardiography-guided optimal settings. Optimal AV and VV intervals varied considerably between patients. All patients exhibited significant changes in waveform morphology with AV optimization. Optimal AV delay determined from echocardiography ranged between 140 ms and 225 ms. Mean LAP tended to be lower at optimal setting 14 ± 3 mmHg compared to shorter (<100 ms) or longer (>160 ms) AV settings (P = 0.16). There were clear trends to smaller peak a-wave (P = 0.11) and gentler positive a-slope (P = 0.15) and positive v-slope (P = 0.09) with longer AV delays. Mean LAP and negative v-wave slope correlated well with echo-guided optimal setting, r = 0.91 (P = 0.001) and 0.79 (P = 0.03), respectively. No significant effects on LAP or waveform were seen during VV optimization. LAP and its waveform changes considerably with AV optimization. There is good agreement between echo-guided optimal setting and LAP. LAP could provide an objective guide to CRT optimization. (Clinical Trial Registry information: URL: http://www.clinicaltrials.gov. Unique Identifier: NCT00632372).

Adjusting the timing of left-ventricular pacing using electrocardiogram and device electrograms

Cardiac resynchronization therapy improves morbidity and mortality in appropriately selected patients. Whether atrioventricular (AV) and interventricular (VV) pacing interval optimization confers further clinical improvement remains unclear. A variety of techniques are used to estimate optimum AV/VV intervals; however, the precision of their estimates and the ramifications of an imprecise estimate have not been characterized previously. An objective methodology for quantifying the precision of estimated optimum AV/VV intervals was developed, allowing physiologic effects to be distinguished from measurement variability. Optimization using multiple conventional techniques was conducted in individual sessions with 20 patients. Measures of stroke volume and dyssynchrony were obtained using impedance cardiography and echocardiographic methods, specifically, aortic velocity-time integral, mitral velocity-time integral, A-wave truncation, and septal-posterior wall motion delay. Echocardiographic methods yielded statistically insignificant data in the majority of patients (62%-82%). In contrast, impedance cardiography yielded statistically significant results in 84% and 75% of patients for AV and VV interval optimization, respectively. Individual cases demonstrated that accepting a plausible but statistically insignificant estimated optimum AV or VV interval can result in worse cardiac function than default values. Consideration of statistical significance is critical for validating clinical optimization data in individual patients and for comparing competing optimization techniques. Accepting an estimated optimum without knowledge of its precision can result in worse cardiac function than default settings and a misinterpretation of observed changes over time. In this study, only impedance cardiography yielded statistically significant AV and VV interval optimization data in the majority of patients.

Objective Outcome data on exercise capacity following atrio-ventricular (AV) optimization of dual-chamber pacing are sparse. Pacemaker settings are often left at manufacturers’ nominal values upon implantation. We studied the short-term effect of AV optimization on exercise capacity in patients with a dual-chamber pacemaker.Methods and results Twenty-eight patients (mean age 73 ± 14 y) with a dual-chamber pacemaker, were randomized towards either nominal AV settings (group 1) or echo-guided AV optimization using the iterative mitral inflow VTI (velocity time integral) method (group 2) at baseline. At 4 weeks, patients were crossed-over to AV optimization in group 1 and returned to nominal AV settings in group 2 for another period of 4 weeks.Oxygen uptake efficiency slope improved significantly after AV optimization (by 126.7 mL/logL ± 190.7 mL/logL; P= 0.003).Conclusions AV optimization in dual-chamber pacing significantly improved functional capacity after 4 weeks. These data provide the background for further validation studies.

Comparison of different approaches for optimization of atrioventricular and interventricular delay in biventricular pacing

In spite of cardiac resynchronization therapy (CRT) benefits, 25-30% of patients are still non responders. One of the possible reasons could be the non optimal atrioventricular (AV) and interventricular (VV) intervals settings. Our aim was to exploit a numerical model of cardiovascular system for AV and VV intervals optimization in CRT. A numerical model of the cardiovascular system CRT-dedicated was previously developed. Echocardiographic parameters, Systemic aortic pressure and ECG were collected in 20 consecutive patients before and after CRT. Patient data were simulated by the model that was used to optimize and set into the device the intervals at the baseline and at the follow up. The optimal AV and VV intervals were chosen to optimize the simulated selected variable/s on the base of both echocardiographic and electrocardiographic parameters. Intervals were different for each patient and in most cases, they changed at follow up. The model can well reproduce clinical data as verified with Bland Altman analysis and T-test (p > 0.05). Left ventricular remodeling was 38.7% and left ventricular ejection fraction increasing was 11% against the 15% and 6% reported in literature, respectively. The developed numerical model could reproduce patients conditions at the baseline and at the follow up including the CRT effects. The model could be used to optimize AV and VV intervals at the baseline and at the follow up realizing a personalized and dynamic CRT. A patient tailored CRT could improve patients outcome in comparison to literature data.

179-02: First-degree atrioventricular Block, Atrioventricular (Dys)synchrony and Dual-chamber pacing. A long PR interval or a wide QRS? That is the dilemma

PROGNOSTIC VALUE OF ECHO-DOPPLER GUIDED AV DELAY OPTIMIZATION FOLLOWING CARDIAC RESYNCHRONIZATION THERAPY

A prospective comparison of echocardiography and device algorithms for atrioventricular and interventricular interval optimization in cardiac resynchronization therapy

The atrioventricular delay of cardiac resynchronization can be optimized hemodynamically during exercise and predicted from resting measurements