Expanding benefits from cardiac resynchronization therapy to exercise-induced left bundle branch block in advanced...

Area of Science:

• Cardiology
• Electrophysiology
• Heart Failure Management

Background:

• Cardiac resynchronization therapy (CRT) is indicated for heart failure with reduced ejection fraction (HFrEF) and left bundle branch block (LBBB).
• Exercise-induced LBBB is not a current standard indication for CRT.
• Patients with HFrEF often present with significant functional impairment.

Observation:

• A 57-year-old woman with idiopathic dilated cardiomyopathy (ejection fraction 23%) and NYHA Class IV symptoms experienced recurrent hospitalizations.
• During a cardiopulmonary exercise test for heart transplant evaluation, a new onset of intermittent left bundle branch block was detected.
• This patient had no LBBB at rest but demonstrated electromechanical dyssynchrony during exertion.

Findings:

• CRT was implanted, achieving a 97% resynchronization rate.
• Following CRT implantation, the patient showed significant improvements in both clinical and prognostic exercise parameters at 12-month follow-up.
• The case demonstrates that CRT can be effective in improving functional capacity in selected HFrEF patients with exercise-induced LBBB.

Implications:

• Cardiopulmonary exercise testing may reveal subclinical electromechanical dyssynchrony in HFrEF patients without resting LBBB.
• Identifying exercise-induced LBBB could expand the criteria for CRT candidacy.
• CRT may offer a viable therapeutic option for improving exercise tolerance and quality of life in this patient population.