Updates in Cardiac Resynchronization Therapy for Chronic Heart Failure: Review of Multisite Pacing.

PURPOSE OF REVIEW: Cardiac resynchronization therapy (CRT) reduces the morbidity and mortality of patients with left ventricular (LV) systolic dysfunction and intra-ventricular conduction delay. However, its clinical outcomes are heterogeneous and not all patients show a beneficial response. Multisite pacing (MSP), by stimulating the myocardium from more than one locations, is a potential therapeutic option in patients requiring CRT. This article provides a current update in the methods and outcomes of MSP, as well as in challenges in this field and opportunities for further research and development. RECENT FINDINGS: MSP can be delivered either with multiple leads or with quadripolar LV leads which can stimulate the LV from two separate sites. Initial results are promising but not always consistent across studies. Larger patient subgroups and longer follow-up duration are required for more conclusive evaluation of MSP. Routine use of MSP in clinical practice cannot be advocated at present. In selected patient subgroups, however, MSP could be considered. Newer devices and expanding knowledge are expected to facilitate the more widespread implementation of MSP and the assessment of its effects in the clinical outcomes of CRT.

Is heart failure with mid range ejection fraction (HFmrEF) a distinct clinical entity or an overlap group?

BACKGROUND: The new category of heart failure (HF), Heart Failure with mid range Ejection Fraction (HFmrEF) has recently been proposed with recent publications reporting that HFmrEF represents a transitional phase. The aim of this study was to determine the prevalence and clinical characteristics of patients with HFmrEF and to establish what proportion of patients transitioned to other types of HF, and how this affected clinical outcomes. METHODS AND RESULTS: Patients were diagnosed with HF according to the 2016 ESC guidelines. Clinical outcomes and variables were recorded for all consecutive in-patients referred to the heart failure service. In total, 677 patients with new HF were identified; 25.6% with HFpEF, 21% with HFmrEF and 53.5% with HFrEF. While clinical characteristics and prognostic factors of HFmrEF were intermediate between HFrEF and HFpEF, HFmrEF patients had the best outcome, with higher mortality in the HFrEF population (p 0.02) and higher HF rehospitalisation rates in the HFpEF population (p < 0.01).38.7% of the HFmrEF patients transitioned (56.4% to HFpEF and 43.6% to HFrEF) with fewest deaths in the patients that transitioned to HFpEF (p 0.04), and fewest HF readmissions in the patients that remained as HFmrEF (<0.01). CONCLUSION: HFmrEF patients had the best outcomes, compared to high rates of mortality seen in patients with HFrEF and high rates of HF readmissions seen in patients with HFpEF. Only 1/3 of HFmrEF patients transitioned during follow up, with the lowest mortality seen in patients transitioning to HFpEF.

A cost effectiveness study establishing the impact and accuracy of implementing the NICE guidelines lowering plasma NTproBNP threshold in patients with clinically suspected heart failure at our institution.

AIMS: The 2014 National Institute of Clinical Excellence (NICE) guidelines on the management of acute heart failure recommended using a plasma NT-proBNP threshold of 300pg/ml to assist in ruling out the diagnosis of heart failure (HF), updating previous guidelines recommending using a threshold of 400pg/ml. NICE based their recommendations on 6 studies performed in other countries. This study sought to determine the diagnostic and economic implications of using these thresholds in a large unselected UK population. METHODS: Patient and clinical demographics were recorded for all consecutive suspected HF patients over 12months, as well as clinical outcomes including time to HF hospitalisation and time to death (follow up 15.8months). RESULTS: Of 1995 unselected patients admitted with clinically suspected HF, 1683 (84%) had a NTproBNP over the current NICE recommended threshold, of which 35% received a final diagnosis of HF. Lowering the threshold from 400 to 300pg/ml would have involved screening an additional 61 patients and only would have identified one new patient with HF (sensitivity 0.985, NPV 0.976, area under the curve (AUC) at 300pg/ml 0.67; sensitivity 0.983, NPV 0.977, AUC 0.65 at 400pg/ml). The economic implications of lowering the threshold would have involved additional costs of £42,842.04 (£702.33 per patient screened, or £ 42,824.04 per new HF patient). CONCLUSION: Applying the recent updated NICE guidelines to an unselected real world population increases the AUC but would have a significant economic impact and only identified one new patient with heart failure.

A comparison of the different features of quadripolar left ventricular pacing leads to deliver cardiac resynchronization therapy.

INTRODUCTION: Cardiac Resynchronization therapy (CRT) improves the quality of life and reduces morbidity and mortality of certain patients with heart failure. However, not all patients respond positively after CRT and about one third of cases do not experience benefit. Suboptimal biventricular pacing may account for this and quadripolar left ventricular (LV) leads have emerged in the last years to address issues relating to inadequate delivery of CRT. AREAS COVERED: This review article concisely summarizes the main technical characteristics of the quadripolar LV leads either currently available in the market today or under final stages of development. Focus is given in recent advancements in the area and challenging aspects and controversies, future implications as well as opportunities for further development. EXPERT COMMENTARY: Quadripolar LV pacing leads have now become the standard of care in CRT. Currently a multitude of lead options is available to the clinician. The selection process of the most appropriate lead is far from the 'one size fits all' concept. Further development of quadripolar LV leads is currently ongoing and it is anticipated to contribute towards the release of more technologically advantageous leads which will enable the delivery of optimal CRT therapy with the lowest rate of complications.

The role of multi modality imaging in selecting patients and guiding lead placement for the delivery of cardiac resynchronization therapy.

INTRODUCTION: Cardiac resynchronization therapy (CRT) is an effective pacemaker delivered treatment for selected patients with heart failure with the target of restoring electro-mechanical synchrony. Imaging techniques using echocardiography have as yet failed to find a metric of dyssynchrony to predict CRT response. Current guidelines are thus unchanged in recommending prolonged QRS duration, severe systolic function and refractory heart failure symptoms as criteria for CRT implantation. Evolving strain imaging techniques in 3D echocardiography, cardiac MRI and CT may however, overcome limitations of older methods and yield more powerful CRT response predictors. Areas covered: In this review, we firstly discuss the use of multi modality cardiac imaging in the selection of patients for CRT implantation and predicting the response to CRT. Secondly we examine the clinical evidence on avoiding areas of myocardial scar, targeting areas of dyssynchrony and in doing so, achieving the optimal positioning of the left ventricular lead to deliver CRT. Finally, we present the latest clinical studies which are integrating both clinical and imaging data with X-rays during the implantation in order to improve the accuracy of LV lead placement. Expert commentary: Image integration and fusion of datasets with live X-Ray angiography to guide procedures in real time is now a reality for some implanting centers. Such hybrid facilities will enable users to interact with images, allowing measurement, annotation and manipulation with instantaneous visualization on the catheter laboratory monitor. Such advances will serve as an invaluable adjunct for implanting physicians to accurately deliver pacemaker leads into the optimal position to deliver CRT.

Comprehensive use of cardiac computed tomography to guide left ventricular lead placement in cardiac resynchronization therapy.

BACKGROUND: Optimal lead positioning is an important determinant of cardiac resynchronization therapy (CRT) response. OBJECTIVE: The purpose of this study was to evaluate cardiac computed tomography (CT) selection of the optimal epicardial vein for left ventricular (LV) lead placement by targeting regions of late mechanical activation and avoiding myocardial scar. METHODS: Eighteen patients undergoing CRT upgrade with existing pacing systems underwent preimplant electrocardiogram-gated cardiac CT to assess wall thickness, hypoperfusion, late mechanical activation, and regions of myocardial scar by the derivation of the stretch quantifier for endocardial engraved zones (SQUEEZ) algorithm. Cardiac venous anatomy was mapped to individualized American Heart Association (AHA) bull's-eye plots to identify the optimal venous target and compared with acute hemodynamic response (AHR) in each coronary venous target using an LV pressure wire. RESULTS: Fifteen data sets were evaluable. CT-SQUEEZ-derived targets produced a similar mean AHR compared with the best achievable AHR (20.4% ± 13.7% vs 24.9% ± 11.1%; P = .36). SQUEEZ-derived guidance produced a positive AHR in 92% of target segments, and pacing in a CT-SQUEEZ target vein produced a greater clinical response rate vs nontarget segments (90% vs 60%). CONCLUSION: Preprocedural CT-SQUEEZ-derived target selection may be a valuable tool to predict the optimal venous site for LV lead placement in patients undergoing CRT upgrade.

Real-Time X-MRI-Guided Left Ventricular Lead Implantation for Targeted Delivery of Cardiac Resynchronization Therapy.

OBJECTIVES: This study sought to test the feasibility of a purpose-built, integrated software platform to process, analyze, and overlay cardiac magnetic resonance (CMR) data in real time within a combined cardiac catheter laboratory and magnetic resonance imaging scanner suite (X-MRI) to guide left ventricular (LV) lead implantation. BACKGROUND: Suboptimal LV lead position is a major determinant of poor cardiac resynchronization therapy (CRT) response, and the optimal site is highly patient specific. Pacing myocardial scar is associated with poorer outcomes; conversely, targeting latest mechanical activation (LMA) may improve them. METHODS: Fourteen patients (age 74 ± 5.1 years; New York Heart Association functional class: 2.7 ± 0.4; 86% ischemic with ejection fraction 27 ± 7.6%; QRSd: 157 ± 19 ms) underwent CMR followed by immediate CRT implantation using derived scar and dyssynchrony data, overlaid onto fluoroscopy in an X-MRI suite. Rapid LV segmentation enabled detailed scar quantification, identification of LMA segments, and selection of myocardial targets. At coronary venography, the CMR-derived 3-dimensional shell was fused, enabling identification of viable venous targets subtended by target segments for LV lead placement. RESULTS: The platform was successful in all 14 patients, of whom 10 (71%) were paced in pre-procedurally defined target segments. Pacing in CMR-defined target segments (out of scar) showed a significant decrease in the LV capture threshold (mean difference: 2.4 [1.5 to 3.2]; p < 0.001) and shorter paced QRS duration (mean difference: 25 [15 to 34]; p < 0.001) compared with pacing in areas of CMR determined scar. In 5 (36%) patients with extensive scar in the posterolateral wall, CMR guidance enabled successful lead delivery in an alternative anatomically favorable site. Radiation dose and implant times were similar to historical controls (p = NS). CONCLUSIONS: Real-time CMR-guided LV lead placement is feasible and achievable in a single clinical setting and may prove helpful to preferentially select sites for LV lead placement.