Reevaluating Modality of Cardiopulmonary Exercise Testing in Patients with Heart Failure and Resynchronization Therapy: Relevance of Heart Rate-Adaptive Pacing

Characterization and prognostic importance of chronotropic incompetence in heart failure with preserved ejection fraction

BACKGROUND

Exercise intolerance is the primary symptom of patients with heart failure with preserved ejection fraction (HFpEF). Chronotropic incompetence has been considered to be common and contribute to poor exercise capacity in HFpEF. However, clinical characteristics, pathophysiology, and outcomes of chronotropic incompetence in HFpEF remain poorly understood.

METHODS

Patients with HFpEF (n = 246) underwent ergometry exercise stress echocardiography with simultaneous expired gas analysis. The patients were divided into two groups based on the presence of chronotropic incompetence, which was defined by heart rate reserve <0.80.

RESULTS

Chronotropic incompetence was common in HFpEF (n = 112, 41 %). Compared to HFpEF patients with a normal chronotropic response (n = 134), those with chronotropic incompetence had higher body mass index, a higher prevalence of diabetes, more frequent β-blocker use, and worse New York Heart Association class. During peak exercise, patients with chronotropic incompetence demonstrated less increase in cardiac output and arterial oxygen delivery (cardiac output × saturation × hemoglobin × 1.34 × 10), higher metabolic work (peak oxygen consumption [VO2]/watt), an inability to increase arteriovenous oxygen difference, and poorer exercise capacity (lower peak VO2) than those without. Chronotropic incompetence was associated with higher rates of a composite of all-cause mortality or worsening HF events (hazard ratio, 2.66, 95 % confidence intervals, 1.16-6.09, p = 0.02).

CONCLUSION

Chronotropic incompetence is common in HFpEF, and is associated with unique pathophysiologic characteristics during exercise and clinical outcomes.

Aerobic exercise prescription in heart failure patients with cardiac resynchronization therapy

Exercise for heart failure patients had been shown to be beneficial in improving functional status, and was reviewed to be safe. In cases of advanced heart failure, Cardiac Resynchronization Therapy (CRT) is a promising medical option before being a heart transplant candidate. CRT itself is a biventricular pacing device, which could detect electrical aberrance in the failing heart and provide a suitable response. Studies have shown that exercise has clear benefits toward improving an overall exercise capacity of the patients. Despite its impacts, these randomized clinical trials have varying exercise regime, and until now there has not been a standardized exercise prescription for this group of patients. The nature of CRT as a pacemaker, sometimes with defibrillator, being attached to a heart failure patient, each has its own potential exercise hazards. Therefore, providing detailed exercise prescription in adjusting to the medical condition is very essential in the field of physical medicine and rehabilitation. Being classified as a high-risk patient group, exercise challenges for the complex heart failure with CRT patients will then be discussed in this literature review, with a general aim to provide a safe, effective, and targeted exercise regime.