Closed-Loop Stimulation in Left Bundle Branch Area Pacing

Change in heart rate (ΔHR) during the Paced Auditory Serial Addition Test (PASAT), calculated as the peak heart rate recorded during the test minus the baseline heart rate. The outcome was assessed under both closed-loop stimulation (CLS) and accelerometer-based VVIR pacing and expressed in beats per minute (bpm).

Change in heart rate (ΔHR) during the 5-minute isometric handgrip test performed at 30% of maximal voluntary contraction, calculated as the peak heart rate recorded during the test minus the baseline heart rate. The outcome was assessed under both closed-loop stimulation (CLS) and accelerometer-based VVIR pacing and expressed in beats per minute (bpm).

Change in heart rate (ΔHR) during the symptom-limited treadmill exercise test using the modified Bruce protocol, calculated as the peak heart rate achieved during exercise minus the baseline heart rate. The outcome was assessed under both closed-loop stimulation (CLS) and accelerometer-based VVIR pacing and expressed in beats per minute (bpm).

Total exercise duration during the symptom-limited treadmill exercise test performed using the modified Bruce protocol. The outcome was assessed under both closed-loop stimulation (CLS) and accelerometer-based VVIR pacing and expressed in seconds.

Exercise capacity during the symptom-limited treadmill exercise test using the modified Bruce protocol, expressed as metabolic equivalents (METs) achieved during the test. The outcome was assessed under both closed-loop stimulation (CLS) and accelerometer-based VVIR pacing.

Heart Rate Score (HRS), defined as the percentage of all sensed and paced ventricular beats occurring in the most populated 10-beats-per-minute heart rate histogram bin. HRS was assessed from pacemaker-derived heart rate histograms under both closed-loop stimulation (CLS) and accelerometer-based VVIR pacing. Higher HRS values indicate a more concentrated heart rate distribution and less heart rate variation across histogram bins. The score ranges from 0% to 100%.

Health-related quality of life was assessed using the EuroQol 5-Dimension 5-Level (EQ-5D-5L) descriptive system. Responses were converted to an EQ-5D-5L index value using the Polish value set. Index values range from -0.590 to 1.000, with higher values indicating better health-related quality of life. A value of 1 represents full health, 0 represents a health state equivalent to death, and negative values represent health states valued as worse than death. The outcome was compared between closed-loop stimulation (CLS) and accelerometer-based VVIR pacing.

Self-rated health was assessed using the EuroQol Visual Analogue Scale (EQ VAS), ranging from 0 to 100, where 0 represents the worst health the participant can imagine and 100 represents the best health the participant can imagine. The outcome was assessed under both closed-loop stimulation (CLS) and accelerometer-based VVIR pacing.

At the end of the study, participants were asked during which of the two pacing periods they experienced better overall subjective well-being, or whether they had no preference. Responses were subsequently categorized according to the pacing mode programmed during the preferred period as preference for closed-loop stimulation (CLS), preference for accelerometer-based VVIR pacing, or no preference.

Ventricular pacing percentage was obtained from pacemaker interrogation and defined as the proportion of ventricular events that were paced during each study period. The outcome was assessed under both closed-loop stimulation (CLS) and accelerometer-based VVIR pacing and expressed as a percentage from 0% to 100%.