Prognostication of Poor Survival After Cardiac Resynchronization Therapy

The Role of Cardiac Resynchronization Therapy in Heart Failure: A Narrative Review

Introduction

Structural and functional cardiac defects leading to inadequate tissue oxygenation is known as Heart failure (HF) which is characterized by extensive morbidity and mortality. Pathophysiology of HF involves systolic and diastolic dysfunction, neurohormonal dysregulation, and imbalance in inflammatory mediators which complicates treatment further. Cardiac resynchronization therapy (CRT) is an approach used for restoring ventricular synchrony and enhancing mechanical efficiency. This study discusses various key points of CRT and its uses in HF and discusses challenges and future implications.

Methods

An extensive review of the literature was conducted with evidence from several databases like Medline, PubMed Central, and Embase. Preference was given to articles published after 2010, but relevant articles even pre-2010 were included. Mendeley was used as a reference manager for formatting.

Results

Functional improvements and an enhanced quality of life across a diverse range of patients have been demonstrated using CRT. This has significantly impacted the mortality rates of patients with HF. This manuscript conducted a comparative analysis various hallmark clinical trials conducted in lieu of CRT, across many years (2002, 2003, 2004, 2005, 2017, 2018, 2020). All trials have noted the supremacy of CRT compared to pharmaceutical treatment or other therapeutic methods. Majority of the trial participants had an LVEF of ≤ 35%, a QRS duration of ≤ 150 ms, and were categorized as NYHA class II-IV before initiation of CRT and, posttreatment, LVEF was improved significantly. The main advantages noted were functional improvements, such as enhanced quality of life and reduced mortality.

Conclusion

There have been multiple efforts undertaken to address the challenges in CRT, which include a reduction in the rates of nonresponding patients and using alternative adjunctive therapies like defibrillators. These have been shown to improve outcomes among HF patients. Although CRT is noted to be very efficient, some challenges like technological limitations, uncertainty regarding optimal pacing, and nonresponding patients, exist. Ongoing research aims to further develop and revolutionize HF care and improve patient outcomes across the world by refining patient selections and CRT efficacy.

A Simple Predictive Marker in Cardiac Resynchronization Therapy Recipients: Prominent S-Wave in Right Precordial Leads

Background and objectives: Current guidelines criteria do not satisfactorily discriminate responders to cardiac resynchronization therapy (CRT). QRS amplitude is an established index to recognize the severity of myocardial disturbance and might be a key to optimal patient selection for CRT. Materials and Methods: (1) Initial R-wave amplitude, (2) S-wave amplitude, and (3) a summation of maximal R- or R′-wave amplitude and S-wave amplitude were measured at baseline. These parameters were averaged according to right (V1 to V3) or left (V4 to V6) precordial leads. The impact of these parameters on response to CRT, which was defined as a decrease in left ventricular end-systolic volume ≥15% at six-month follow-up, was investigated. Results: Among 47 patients (71 years old, 28 men) who received guideline-indicated CRT implantation, 25 (53%) achieved the definition of CRT responder. Among baseline electrocardiogram parameters, only the higher S-wave amplitude in right precordial leads was an independent predictor of CRT responders (odds ratio: 2.181, 95% confidence interval: 1.078–4.414, p = 0.030) at a cutoff of 1.44 mV. The cutoff was independently associated with cumulative incidence of heart failure readmission and appropriate electrical defibrillation following CRT implantation (p < 0.05, respectively). Conclusions: Prominent S-wave in right precordial leads might be a promising index to predict left ventricular reverse remodeling and greater clinical outcomes following CRT implantation.

Ischemic Etiology and Clinical Outcomes Following Cardiac Resynchronization Therapy

Optimal patient selection for cardiac resynchronization therapy is crucial. There are several concerns that allow to better clarify the association between the ischemic etiology of heart failure and the response to cardiac resynchronization therapy. The type of ischemic coronary disease has an impact on the responses to cardiac resynchronization therapy. The prognostic impact of cardiac resynchronization therapy on cardiac death including heart transplantation and durable ventricular assist device implantation is another concern.