This study aims to evaluate the clinical impact of an optimized pacing strategy in patients with heart failure.

• Intervention: Adjustment of the pacemaker lower rate limit to an individualized, hemodynamically optimized heart rate.
• Primary Endpoint: Heart failure symptoms, assessed by the Kansas City Cardiomyopathy Questionnaire score.
• Hypothesis: In patients with heart failure requiring permanent pacing, an optimized pacing strategy will lead to a significant improvement in heart failure symptoms (Kansas City Cardiomyopathy Questionnaire score) at 12 months compared with the conventional pacing strategy.

Heart failure is a growing health concern with increasing prevalence in the aging population, and permanent pacemaker implantation is frequently required due to concomitant bradyarrhythmias. Heart rate is closely associated with hemodynamic status in patients with heart failure; however, evidence guiding the optimal pacemaker lower rate setting remains limited. Although the conventional lower rate is typically set at 50-60 bpm, recent studies suggest that a moderately increased pacing rate may improve hemodynamics and clinical outcomes. Furthermore, advances in physiological pacing techniques, such as conduction system pacing, provide the potential for greater clinical benefits through optimized heart rate settings in this patient population.

Enrolled subjects are randomized in a 1:1 ratio into either the optimized pacing group or the conventional pacing strategy group based on stratification factors.

The optimized pacing group undergoes post-procedural right heart catheterization with adjustments to the lower rate limit, where the heart rate (HR) that yields the lowest mean pulmonary capillary wedge pressure (mPCWP) or the highest cardiac output is determined as the optimal HR. In the conventional pacing strategy group, the lower rate limit is set at 60 bpm. Clinical symptoms and parameters of both groups are subsequently compared over a one-year follow-up period.

Inclusion Criteria:

• Patients with symptomatic bradycardia who meet the indication for permanent pacemaker implantation and fulfill one of the following conditions:

  1. Sick sinus syndrome with or without impaired atrioventricular conduction
  2. Persistent or permanent atrial fibrillation with slow ventricular response
  3. Chronotropic incompetence

• Patients diagnosed with heart failure with left ventricular ejection fraction ≥ 50% on transthoracic echocardiography with at least one of the following:

• H2FPEF score ≥ 6 or HFA-PEFF score ≥ 5

• N-terminal pro-B-type natriuretic peptide ≥ 300 pg/mL (sinus rhythm) or ≥ 600 pg/mL (atrial fibrillation)

• Prior hospitalization for heart failure or documented use of loop diuretics for heart failure symptoms

Exclusion Criteria:

• Patients expected to have a ventricular pacing burden ≥ 20% without sufficient capture of cardiac physiologic pacing, which includes biventricular pacing, His bundle pacing, and left bundle branch area pacing.

(Sufficient cardiac physiologic pacing is defined as a paced QRS duration ≤ 140 ms.)

• Patients not expected to achieve sufficient pacing dependency, defined as:

  1. In sinus rhythm: baseline atrial rate > 60 bpm on Holter monitoring or inpatient ECG monitoring
  2. In atrial fibrillation/flutter: baseline ventricular rate > 60 bpm on Holter monitoring or inpatient ECG monitoring

• Patients with contraindications to permanent pacemaker implantation

• Patients with moderate or greater valvular stenosis or regurgitation.

• Patients with dyspnea not attributable to heart failure, due to uncontrolled comorbid conditions

• Pregnant or breastfeeding women.

• Patients who have refused active treatment.