June 29, 2023

Heart Rhythm Society Guideline Addresses Cardiac Physiologic Pacing for Heart Failure

Indications and issues concerning cardiac resynchronization therapy, conduction system pacing

illustration of failing heart against ECG background

Conduction system pacing (CSP) is increasingly used as a permanent pacing strategy to address atrioventricular conduction dyssynchrony, thereby slowing or preventing development of heart failure. But when is it indicated over cardiac resynchronization therapy (CRT), which is backed by much stronger evidence garnered over decades of experience?

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This question and others concerning cardiac physiologic pacing (CPP) are addressed in the first practice guideline exclusively on the subject, published online in Heart Rhythm by the Heart Rhythm Society in partnership with the Asia Pacific Heart Rhythm Society and the Latin American Heart Rhythm Society.

“The uses of CSP as well as its comparisons to CRT are very active areas of investigation at the moment,” says guideline chair and first author Mina Chung, MD, a cardiologist in Cleveland Clinic’s Section of Cardiac Pacing and Electrophysiology. “We can expect much more evidence to emerge over the next decade, but this guideline — which has been preceded only by consensus statements on the topic — provides a very up-to-date profile of the state of the field.”

Essentials of CPP

The guideline defines CPP as any method of cardiac pacing intended to restore or preserve synchrony of ventricular contraction. It includes two major strategies:

  • CRT, usually achieved by biventricular pacing using leads in the coronary sinus branch or epicardial left ventricular area. Multiple randomized clinical trials have provided robust evidence of the benefits of CRT, including reducing symptoms of heart failure, reducing hospitalization, improving left ventricular function and lowering mortality.
  • CSP, which directly engages the conduction system via leads in the His bundle or left bundle branch (LBB) area. Theoretically, this method should achieve a more physiologic pacing than CRT and would be better for certain indications, but long-term experience is lacking and the evidence for its benefits is not nearly as strong as for CRT.

Key recommendations on CPP strategies

The new guideline describes situations that are likely (or not likely) to derive benefit from CPP and provides an algorithm with specific recommendations for either CRT or CSP in different scenarios. Dr. Chung highlights the following recommendations from the document:

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  • Patients undergoing pacemaker implantation who are expected to require substantial ventricular pacing (≥ 20% to 40%) should be considered for CPP to reduce the risk of pacing-induced cardiomyopathy. Those with left ventricular ejection fraction (LVEF) of 35% to 50% and advanced atrioventricular block are at particular risk of developing cardiomyopathy from substantial right ventricular pacing, according to key evidence from a Cleveland Clinic study published in Heart Rhythm (2016;13[12]:2272-2278).
  • Conversely, patients who are expected to require less ventricular pacing (< 20% to 40%) are less likely to benefit greatly from CPP. In such cases, it is reasonable to use traditional right ventricular lead placement with minimization of ventricular pacing. CSP or CRT in the setting of LBB block are also options.
  • For patients with normal LVEF who need a pacing device, the guideline provides new recommendations for LBB area pacing.

Dr. Chung notes that CRT still has class I recommendations for patients with heart failure, LVEF of 35% or less, LBB block, QRS duration of at least 150 ms, and New York Heart Association functional class II to IV symptoms on guideline-directed medical therapy. “For such patients, CRT has been well demonstrated to save lives and should be tried first,” she emphasizes. “For those who cannot benefit from CRT or have characteristics that do not meet criteria for its use, the guideline provides new recommendations for CSP strategies.”

Guideline scope, points of distinction, special issues

The 60-member international writing group developed the guideline to be relevant to medical practice worldwide. Its chief focus is to provide recommendations for the use of CPP, including for heart failure and for patients who are pacemaker candidates. Topics include patient selection, preprocedure evaluation and preparation, implant management, follow-up and response optimization, and CPP use in pediatric populations.

“This guideline represents an international multidisciplinary collaborative effort that provides not only clinical practice guidance on the latest techniques in pacing therapies, but also how patients and clinicians may consider such options together in establishing shared care goals,” says guideline co-author W.H. Wilson Tang, MD, Research Director for the Section of Heart Failure and Cardiac Transplantation Medicine at Cleveland Clinic. “Incorporating specific recommendations for optimal clinical management before, during and after placement of cardiac physiologic pacing devices emphasizes an important and holistic approach to treat and prevent heart failure beyond discussions of their clinical indications.”

“This is a very important step in helping physicians choose appropriate electrical therapies for their patients,” adds guideline co-author and Cleveland Clinic electrophysiologist John Rickard, MD, MPH. “For the first time, we have a guideline that makes recommendations for the use of conduction system pacing as well as multidisciplinary care clinics to best serve our patients. Cleveland Clinic was among the first to establish a large multidisciplinary combined electrophysiology/heart failure clinic for the care of heart failure patients with conduction disorders. The new guideline took notice of this clinic and shows strong support for the spread of such clinics globally.”

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One issue that challenged the committee when evaluating evidence, Dr. Chung notes, was that definitions of response to CRT and clinical improvement often differ among studies. Some patients ― sometimes referred to as “stabilizers” or “nonprogressors” ― appear not to achieve reverse remodeling with CRT, yet they have a slowing of the expected progression of heart failure. The committee proposed using the term “favorable responder” to include such patients (for any form of CPP) versus “unfavorable responder” for those who appear not to derive any benefit.

“With a significant proportion of patients not responding to CRT, it’s critical to distinguish real failure from apparent failure,” Dr. Chung explains. “This distinction serves to improve quality of care and supports appropriate use of therapeutics, our overarching goals for this guideline.”

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