Comparison of dyssynchrony parameters for VV-optimization in CRT patients

Efficacy on resynchronization and longitudinal contractile function comparing His-bundle pacing with conventional biventricular pacing: a substudy to the His-alternative study

AIMS

His-bundle pacing has emerged as a novel method to deliver cardiac resynchronization therapy (CRT). However, there are no data comparing conventional biventricular (BiV)-CRT with His-CRT with regard to effects on mechanical dyssynchrony and longitudinal contractile function.

METHODS AND RESULTS

Patients with symptomatic heart failure, left ventricular ejection fraction ≤ 35%, and left bundle branch block (LBBB) by strict ECG criteria were randomized 1:1 to His-CRT or BiV-CRT. Two-dimensional strain echocardiography was performed prior to CRT implantation and at 6 months after implantation. Differences in changes in mechanical dyssynchrony (standard deviation of time-to-peak in 12 midventricular and basal segments) and regional longitudinal strain in the six left ventricular walls were compared between the BiV-CRT and His-CRT groups.In the on-treatment analysis, 31 received BiV-CRT and 19 His-CRT. In both groups, mechanical dyssynchrony was significantly reduced after 6 months [BiV group from 120 ms (±45) to 63 ms (±22), P < 0.001, and His group from 116 ms (±54) to 49 ms (±11), P < 0.001] but no significant differences in changes could be demonstrated between groups [-9.0 ms (-36; 18), P = 0.50]. Global longitudinal strain (GLS) improved in both groups [BiV group from -9.1% (±2.7) to -10.7% (±2.6), P = 0.02, and His group from -8.6% (±2.1) to -11.1% (±2.0), P < 0.001], but no significant differences in changes could be demonstrated from baseline to follow-up [-0.9% (-2.4; -0.6), P = 0.25] between groups. There were no regional differences between groups.

CONCLUSION

In heart failure, patients with LBBB, BiV-CRT, and His-CRT have comparable effects with regard to improvements in mechanical dyssynchrony and longitudinal contractile function.

Myocardial strain characteristics at different interventricular pacing timings: implications for device programming and long-term clinical outcomes in patients with cardiac resynchronisation therapy

AIMS

Response to cardiac resynchronisation therapy (CRT) in patients with heart failure depends on the degree of correction of electromechanical dyssynchrony between the left and right ventricles (LV, RV). It is not known whether chronic programming of interventricular (VV) intervals based on characterisation of myocardial strain at different pacing intervals performed acutely would have better long-term clinical outcomes. We hence aimed to evaluate this relationship between speckle tracking strain patterns and rates at different VV intervals and long-term clinical outcomes of programmed VV pacing in patients with CRT in a prospective, longitudinal follow-up study.

METHODS

We assessed echocardiographic effects, myocardial strain patterns and rates in acute settings at VV intervals; 'LV Off', 'VV0', 'VV60' and 'RV Off' to provide 'RV-only', 'simultaneous BiV', 'sequential LV-RV' and 'LV-only' pacing respectively in 338 patients (age, 67.5 ± 10.3 years; male, 70%) with CRT. Thereafter, devices were programmed chronically to VV60, and long-term clinical outcomes were assessed.

RESULTS

With VV0, VV60 and LV only pacing, LVEF improved to 33.6 ± 12.3%, 40.0 ± 11.4% and 42.6 ± 11.2%, respectively, from 23.7 ± 10.2% at baseline (p < .001). Incremental improvement in strain occurred with VV0, VV60 and LV only pacing; greatest with LV only pacing. At 1 year, 23% patients had NYHA III-IV compared to 96% at baseline (p < .001).

CONCLUSIONS

In patients with CRT, different VV timings show significant differences in acute myocardial strain patterns and rates, and LVEF. These changes are markedly favourable with LV-only and sequential LV-RV pacing, the latter with chronic programming also results in long-term clinical improvement.

QRS Duration as a Predictor of Left Ventricular Outflow Tract Velocity Time Integral in Patient with Cardiac Resynchronization Therapy

Background

Cardiac resynchronization therapy (CRT) has a morbidity and mortality benefits in moderate to severe heart failure. It reduces mortality and hospitalization and improves cardiac function. It can be used according to the European guidelines in severely depressed left ventricular ejection fraction (i.e., ≤35%) and complete left bundle branch block. However, 30% of patients may show no benefit from CRT therapy. Therefore, prediction of CRT response seems to be an important subject for study in the current researches. We aimed to study the correlation between Surface ECG QRS complex duration (QRS) duration and cardiac output measured by ventricular outflow tract velocity time integral (LVOT VTI) as a predictor of response in patients with CRT implantation.

Methods

We studied 100 consecutive patients prospectively with biventricular pacing system. The patients were studied at the pacemaker follow-up clinic. Each patient was subjected to: Full medical history, general and local examination, a 12 lead electrocardiogram and QRS duration in ms was measured. All patients were subjected to a focused transthoracic echocardiographic examination in which a parasternal long axis view was obtained to measure the diameter of the LVOT diameter in mid-systole. The LVOT VTI was measured by pulsed-wave Doppler in the LVOT using a 2-mm sample volume positioned just proximal to the aortic valve in the apical five chamber view.

Results

We found a statistically significant difference between CRT responders and nonresponders as regards age, body surface area (BSA), time since CRT implantation and smoking status (P = 0.018, 0.039, 0.002, <0.001). There was negative significant correlation between QRS duration and LVOT VTI and stroke volume index. The optimal cut off values for optimal response to CRT using receiver operating characteristics curves were 130 ms for postimplant QRS duration and 17.1 cm for LVOT VTI. We also found a significant difference between responders and nonresponders as regard CO. It was higher in responders (5.97 vs. 3.34, P < 0.001).

Conclusion

CRT response is more in patients with lower BSA, and without previous history of ischemic heart disease or smoking. There is a significant negative correlation between QRS duration and LVOT VTI.

Noninvasive cardiac output measurement based optimization in nonresponders of cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) is an important and effective therapy for end-stage heart failure (HF). Nonresponse to CRT is one of the main obstacles to its application in clinical practice. Herein, we investigated the utilization of the optimization technique using noninvasive cardiac output measurement (NICOM) based Mobil-O-Graph device that measures several circulation parameters noninvasively.

METHODS

Seventy-five CRT nonresponder HF patients with an implanted CRT device were included. Patients were randomized equally to 3 groups: NICOM, echocardiographic, and empirical optimization groups. After 3 months of optimization, changes in six minutes walk test (6-MWT), cardiac output (CO), left ventricular ejection fraction (LVEF), and end-systolic volume (LVESV) were measured. New York Heart Association (NYHA) class and hospitalization for HF were also determined.

RESULTS

There were no statistically significant differences among the three groups in terms of demographics, baseline characteristics. In the NICOM group, the 6-MWT, LVEF, CO, and LVESV measurements showed significant improvements compared to baseline values (P < .05). There was no significant improvement in 6-MWT, LVEF, CO, NYHA class, and LVESV in Echo and Empirical groups after 3 months (P > .05). 6-MWT, CO, LVESV percentages, and hospitalization for HF were significantly different between the groups (P < .05). In post hoc analyzes, the percentages of the change in 6-MWT, CO, LVESV, and hospitalization for HF were significantly higher in the NICOM group (P < .017).

CONCLUSIONS

This study suggests that Mobil-O-Graph device optimization according to CO measures does appear to have potential hemodynamic and clinical benefits in nonresponder CRT patients. Use of Mobil-O-Graph device as an option for optimization of CRT devices can be an attractive method of improving CRT outcomes.

Improvement of abnormal systolic motion of the interventricular septum with cardiac resynchronization therapy

BACKGROUND

There is no consensus in the literature regarding what is the responsible mechanism of left ventricular dyssynchrony; septal dyskinesia or late movement of left ventricle (LV) lateral wall. We aim to evaluate the abnormal systolic motion in each myocardial segment and the improvement of LV systolic function with pulsed tissue Doppler imaging (TDI) in patients undergoing cardiac resynchronization therapy (CRT) with left bundle branch block (LBBB).

METHODS

A total of 26 patients undergoing CRT implantation with LBBB, wide QRS duration (≥120 ms), and low ejection fraction (EF) (<35%) were included. Pulsed TDI was taken from apical 4-chamber view and parasternal short axis view (PSAX). All echocardiographic parameters were measured when CRT is on and off.

RESULTS

Systolic ejection time (ET) of anteroseptal and posterolateral wall of LV in PSAX was statistically significantly longer in CRT on group (321.6 ± 62.7 vs 237.5 ± 59.3 ms, P < .001; 323.9 ± 58.0 vs 289.4 ± 43.7 ms, P = .015, respectively). In apical 4-chamber view, septal annulus systolic ET is significantly longer in CRT on group than CRT off group (315.8 ± 57.2 vs 287.3 ± 42.2, P = .014). Also, there was a strong correlation between systolic ET of the septum in PSAX with aortic velocity time integral (VTI), QRS duration and EF (r = .587, P = .002; r = .479, P = .013; r = .440, P = .025; respectively).

CONCLUSION

Circumferential contraction of septal myocardial fibers is improved with CRT and it is strongly correlated with increase of aortic VTI and shortening of QRS duration. These findings predict the deterioration of septal contraction as the main mechanism in patients with LBBB pattern and, CRT may improves myocardial contraction by correcting septal systolic motion.

Advances in atrioventricular and interventricular optimization of cardiac resynchronization therapy - what's the gold standard?

INTRODUCTION

Cardiac resynchronization therapy (CRT) is one of the most important advances in heart failure management in the last twenty years. Approximately one-third of patients appear not to respond to therapy. Although there are a number of possible mechanisms for non-response, an important factor is suboptimal atrioventricular (AV) and interventricular (VV) timing intervals. There remains controversy over whether routinely optimizing intervals is necessary and there is no agreed gold standard methodology. Optimization has classically been performed using echocardiography which has limits related to resource use, time-cost and variable reproducibility. Newer optimization methods using device-based sensors and algorithms show promise in reducing heart-failure hospitalization compared with echocardiography. Areas covered: This review outlines the rationale for optimization, the principles of AV and VV optimization, the standard echocardiographic approach and newer device-based algorithms and the evidence base for their use. Expert commentary: The incremental gains of optimization are likely to be real, but small, compared to the overall improvement gained from cardiac resynchronization itself. At this time routine optimization may not be mandatory but should be performed where there is no response to CRT. Device-based optimization algorithms appear to be practical and in some cases, deliver superior clinical outcomes compared to echocardiography.

Identification of Typical Left Bundle Branch Block Contraction by Strain Echocardiography Is Additive to Electrocardiography in Prediction of Long-Term Outcome After Cardiac Resynchronization Therapy

BACKGROUND

Current guidelines suggest that patients with left bundle branch block (LBBB) be treated with cardiac resynchronization therapy (CRT); however, one-third do not have a significant activation delay, which can result in nonresponse. By identifying characteristic opposing wall contraction, 2-dimensional strain echocardiography (2DSE) may detect true LBBB activation.

OBJECTIVES

This study sought to investigate whether the absence of a typical LBBB mechanical activation pattern by 2DSE was associated with unfavorable long-term outcome and if this is additive to electrocardiographic (ECG) morphology and duration.

METHODS

From 2 centers, 208 CRT candidates (New York Heart Association classes II to IV, ejection fraction ≤35%, QRS duration ≥120 ms) with LBBB by ECG were prospectively included. Before CRT implantation, longitudinal strain in the apical 4-chamber view determined whether typical LBBB contraction was present. The pre-defined outcome was freedom from death, left ventricular assist device, or heart transplantation over 4 years.

RESULTS

Two-thirds of patients (63%) had a typical LBBB contraction pattern. During 4 years, 48 patients (23%) reached the primary endpoint. Absence of a typical LBBB contraction was independently associated with increased risk of adverse outcome after adjustment for ischemic heart disease and QRS width (hazard ratio [HR]: 3.1; 95% CI: 1.64 to 5.88; p < 0.005). Adding pattern assessment to a risk prediction model including QRS duration and ischemic heart disease significantly improved the net reclassification index to 0.14 (p = 0.04) and improved the C-statistics (0.63 [95% CI: 0.54 to 0.72] vs. 0.71 [95% CI: 0.63 to 0.80]; p = 0.02). Use of strict LBBB ECG criteria was not independently associated with outcome in the multivariate model (HR: 1.72; 95% CI: 0.89 to 3.33; p = 0.11. Assessment of LBBB contraction pattern was superior to time-to-peak indexes of dyssynchrony (p < 0.01 for all).

CONCLUSIONS

Contraction pattern assessment to identify true LBBB activation provided important prognostic information in CRT candidates.

Echocardiographic assessment of myocardial ischemia

Over the last 60 years, echocardiography has emerged as a dominant and indispensable technique for the detection and assessment of coronary heart disease (CHD). In this review, we will describe and discuss this powerful tool of cardiology, especially in the hands of an experienced user, with a focus on myocardial ischemia. Technical development is still on-going, and various new ultrasound techniques have been established in the field of echocardiography in the last several years, including tissue Doppler imaging (TDI), contrast echocardiography, three-dimensional echocardiography (3DE), and speckle tracking echocardiography (i.e., strain/strain rate-echocardiography). High-end equipment with harmonic imaging, high frame rates and the opportunity to adjust mechanical indices has improved imaging quality. Like all new techniques, these techniques must first be subjected to comprehensive scientific assessment, and appropriate training that accounts for physical and physiological limits should be provided. These limits will constantly be redefined as echocardiographic techniques continue to change, which will present new challenges for the further development of ultrasound technology.

Echocardiographic Evaluation of Left Atrial Mechanics: Function, History, Novel Techniques, Advantages, and Pitfalls

Left atrial (LA) functional analysis has an established role in assessing left ventricular diastolic function. The current standard echocardiographic parameters used to study left ventricular diastolic function include pulsed-wave Doppler mitral inflow analysis, tissue Doppler imaging measurements, and LA dimension estimation. However, the above-mentioned parameters do not directly quantify LA performance. Deformation studies using strain and strain-rate imaging to assess LA function were validated in previous research, but this technique is not currently used in routine clinical practice. This review discusses the history, importance, and pitfalls of strain technology for the analysis of LA mechanics.