Developments in Cardiac Resynchronisation Therapy

Abstract

Since the introduction of CRT more than 20 years ago, its role in mild to severe systolic heart failure has become well established.CRT has been shown to decrease mortality, reduce heart failure hospitalisations and improve functional status in patients with NYHA class II-IV heart failure and QRS prolongation, most commonly with LBBB pattern.1 One of the major limitations of CRT implementation is the significant number of 'appropriate' candidates, as determined by guidelines, who fail to respond with clinical, functional or structural endpoints. The rate of non-responders has been estimated between 20 % and 40 %.2 Efforts to predict those patients who will respond to CRT and to optimise the magnitude of response have been important areas of focus with regard to the future of CRT. This article will present recent considerations and advances, both technical and theoretical, in CRT. 3 This trial examined 67 patients with LV ejection fraction (LVEF) ≤35 %, NYHA class III heart failure symptoms, sinus rhythm and QRS duration >150 ms who had biventricular pacemakers placed. The devices were initially programmed to ventricular back-up pacing for rates <40 beats per minute for a period of 3 months followed by reprogramming to encourage biventricular pacing. CRT resulted in significant improvement in 6-minute walk distance, quality of life and peak oxygen uptake as well as decreased hospitalisations. Eighty-five per cent of the study patients reported that they felt better during the period with biventricular pacing programmed on. BackgroundThe Multicentre InSync Randomised Clinical Evaluation (MIRACLE) trial evaluated a similar but much larger patient population. 4 There were 453 patients with NYHA class III-IV heart failure, LVEF ≤35 % and QRS duration ≥130 ms randomised to biventricular or no pacing. Over 6 months of follow-up, significant improvements were noted in 6-minute walk distance, NYHA class and quality of life. Additionally, CRT was an effective adjunct to optimal medical therapy in reducing the secondary combined endpoint of heart failure hospitalisation or death. Although the results of MUSTIC and MIRACLE were encouraging in terms of the clinical benefits of CRT, reduced mortality had not yet been proved. The Comparison of Medical Therapy, Pacing and Defibrillation(COMPANION) trial used a combined primary endpoint of hospitalisation or death from any cause.5 Enrolling 1,520 patients with LVEF ≤35 %, NYHA class III-IV heart failure and QRS duration >120 ms, this trial randomised subjects to optimal medical therapy, medical therapy with a CRT pacemaker (CRT-P) or medical therapy with a CRT defibrillator (CRT-D). At 1 year of follow-up, the CRT-D group showed significant reduction in overall mortality versus medical therapy alone, and the CRT-P group had showed a strong trend for reduced mortality (p=0.059).These results suggested a mortality benefit from CRT even in the absence of defibrillator capabilities.Several studies have since examined the effects of biventricular pacing alone (i.e. CRT-P) on heart fa...

His-bundle Pacing as a Bailout Therapy for a Patient with Subclavian Stenosis and No Suitable Coronary Sinus Branch: A Double Whammy

“… 9 Overall, an unfavorable CS anatomy precludes the delivery of an LV lead placement in 5%–8% of patients, and the lead position is suboptimal in another 15%–20% of patients. 10 In a contemporary meta-analysis of 29,503 patients, the overall rate of failure of implantation of an LV lead was 3.6% (95% confidence interval [CI], 3.1%–4.3%). The rate of failure in studies that commenced before 2005 was 5.4% (95% CI, 4.4%–6.5%), and that in studies performed from 2005 onward was 2.4% (95% CI, 1.9%–3.1%; P < .001).…”

How to deliver optimal cardiac resynchronisation therapy

“…Small trials have suggested that CRT non-responders might benefit from placement of an additional LV lead to achieve multisite LV pacing 28. Lenarczyk et al showed that triple-site CRT is more beneficial than conventional CRT and upgrade to triple-site CRT should be considered in non-responders to standard resynchronisation 29.…”

“…The only alternative to transvenous CS cannulation has been surgical placement of epicardial LV leads, an approach with significantly increased risk due to the invasive nature of the procedure 28. The data regarding epicardial/surgical LV lead placement are very limited.…”

Automated Classification of Severity in Cardiac Dyssynchrony Merging Clinical Data and Mechanical Descriptors

“…Guidelines from the American College of Cardiology/American Heart Association/Heart Rhythm Society recommend CRT for HF patients with a functional class III or IV, left ventricle ejection fraction (LVEF) < 35%, and an electrocardiogram trace with a QRS complex greater than 120 milliseconds [ 14 , 15 ]. Efficacy of CRT has been demonstrated in multiple trials, showing a significant improvement in 6-minute walk distance, quality of life, peak oxygen uptake, functional classification, hospital admissions, and mortality among patients with left ventricle (LV) malfunction, and ventricular electric conduction disorders [ 16 , 17 ]. The improvement in LVEF seems to correlate with a better long-term survival [ 18 ].…”

“…Some of them use cine myocardial tagging and strain imaging, a technique that presents a tridimensional map that changes in color reflecting the timing and distribution of circumferential strains during mechanical contraction and relaxation. In a patient with ventricular contraction abnormality, the map will show heterogeneity in color coding mainly related to the septum and the lateral wall [ 16 ]. Nevertheless, the time processing to achieve this map is too high and it might suffer from meaningful degradation.…”