Parks, Jordan

Background: Right ventricular pacing (RVP) can have adverse cardiac effects and cause pacing induced cardiomyopathy (PiCM). His bundle pacing (HBP)&Left Bundle Branch area pacing (LBBAP) mimic physiologic conduction (PhysioP) and maintain biventricular synchrony. Hypothesis and Aims: Reduced left ventricular (LV) systolic function reserve in the presence of normal baseline LV ejection fraction (EF) could precede development of RV PiCM. Our aim was to compare the effects of RVP vs. PhysioP on bicycle exercise cardiopulmonary performance in patients with normal LVEF who required pacing for bradyarrhythmias. Methods: Patients with sinus rhythm and RVP or PhysioP&ventricular pacing burden of >70% who completed cardiopulmonary exercise test and simultaneous stress echocardiography (SE) were included. Pulmonary gas exchange was calculated using Ventilation/CO2 production at rest and during exercise. Changes in LV size, EF, longitudinal strain and diastolic function and gas exchange parameters were compared post and pre exercise in the 2 groups. Results: 25 of 29 patients completed the study [68 ± 23 yrs, 48% M; LVEF 56±5%, 11 RVP, 14 PhysioP]. There was no difference in baseline demographic&clinical variables, exercise duration, rest and peak heart rate and blood pressure between 2 groups. Pacing duration was 2.61±1.48 yrs in RVP vs. 0.84±0.67 yrs (p=0.003) in the Physio group. Resting echocardiographic parameters ( Table 1A) were comparable. Compared to RVP, reduction in LV end-diastolic volume (EDV) 3.4±14.1 ml vs. -23.1±18.1ml, p=0.006)&LV end-systolic volume (ESV -5.7±11.6 ml vs. -18.0±9.5ml, p=0.01) was more pronounced in the PhysioP group. Changes in LVEF, LV strain&diastolic function were not different between the 2 groups ( Table 1B ). There were no significant differences in changes in pulmonary gas exchange parameters in the 2 groups. Conclusions: In patients with normal LVEF and pacemaker dependent, RVP is associated with impaired but PhysioP with preserved LV systolic function reserve, which can be detected by exercise SE. SE may help identify patients at risk for RV PiCM. Benefit of PhysioP needs to be determined by larger studies with longer follow-up.

Introduction: Heart failure (HF) is associated with limited blood flow reserve due to reduced cardiac output (Q). HF is also associated with generalized respiratory muscle weakness, despite patients being exposed to an increased work and cost of breathing due primarily to increased flow resistive work from an altered breathing pattern. We hypothesized that the use of a respiratory training device during aerobic exercise training would positively impact patients with HF by training the inspiratory muscles and modifying their respiratory response to exercise. Methods: 15 subjects completed all study visits (age 67.5±10.0 yr, Ht 179.3±6.1cm, BMI 28.8±5.7 m/cm 2 ). Patients diagnosed with HF and currently enrolled in cardiac rehabilitation (CR) completed the Minnesota living with heart failure questionnaire (MLHFQ), pulmonary function testing, and measures during exercise that included Q (soluble gas method), ventilation (V E ) and respiratory gas exchange. Measures were made at baseline and after completion of CR. Participants were randomized to no respiratory resistance (NR) or mild-moderate inspiratory resistance (MR, 15 to 20 cmH 2 O) provided by a respiratory resistance mask (Training Mask Co., Cadillac, MI) worn during aerobic portions of CR. Results: Participants completed on average 23.9 ± 2.5 CR sessions with 10 subjects in the MR group and 5 in the NR group. The MR group had a decrease on the MLHFQ score of 19.9±26.9 and the NR group had a decrease of 6.0±23.4 (p=0.330). At a matched workload of 30 Watts (W), V E declined by 4.0±7.0 L/min and increased by 2.2±13.1 L/min for subjects in the MR and NR groups, respectively (p=0.06). Respiratory rate (RR) decreased in MR by 1.2± 4.9 and decreased in NR by 0.67± 5.9 (p>0.05). Heart rate at 30W decreased with time in both the MR and NR groups 10.4±12.4 and 3.9±8.9 respectively (p=0.036, no difference between groups). Stroke volume at 30W tended to increase for both MR and NR (p>0.05, no difference between groups). Conclusion: The addition of moderate inspiratory resistance to the aerobic training during CR was well tolerated by HF patients and preliminarily suggests trends toward improved ventilatory responses when assessed during submaximal exercise.