Accumulation of risk factors for pacing-induced cardiomyopathy has a detrimental effect on thoracic impedance and left ventricular ejection fraction

Thoracic impedance (TI) correlates with pulmonary capillary wedge pressure, brain natriuretic peptide and breathlessness. TI rises after implant as pocket inflammatory fluid is reabsorbed. Lower TI levels are seen in patients with heart failure. TI may be able to demonstrate the adverse effect of right ventricular pacing (RVP) in susceptible patients.

To determine whether accumulation of risk factors for pacing-induced cardiomyopathy (PICM) has a detrimental impact on TI and left ventricular ejection fraction (LVEF).

One year of remote monitoring (RM) data was retrieved for all bradycardia pacemaker patients at our centre. Data were collected in November 2023 and the first year of RM data after implant was analysed. Patients were included if RM data commenced within 7 days of implant. Each risk factor for PICM was allocated 1 point. Patients were assigned a score based on the number of risk factors accumulated up to a maximum of 7; age >70 at implant, male, type 2 diabetes (T2DM), chronic kidney disease (CKD), ischaemic heart disease (IHD), history of atrial fibrillation (AF), left ventricular ejection fraction (LVEF) at implant <50%. Patients were divided into two groups based on RVP percentage; ‘paced’ RVP 20-100% and ‘non-paced’ RVP <20%. Linear mixed-effects models were calculated to analyse the impact of the accumulation of PICM risk factors on mean daily TI. A LOESS plot was generated to show TI over time. T-tests were used to compare change in LVEF in paced and non-paced groups.

RM data was retrieved for 1159 patients, of which 965 (83.2%) patients had complete RM data. For each PICM risk factor, mean daily TI decreased by -1.31 ohms (p=0.003) in paced patients. There was no significant change in mean daily TI in non-paced patients (-0.70 ohms p=0.15)(Figure 1). Baseline LVEF was 53.8±3.2 vs 53.0±3.2% p=0.001. In the paced group, RVP was higher (73.5±34 vs 3.4± 9.9%). More paced patients had a follow-up echo (42.1 Vs 29.9% p=0.001). This was at a similar time from implant in both groups (797 (438-1414) Vs 823 (396-1304) days p=0.54). In paced patients, accumulation of three or more PICM risk factors is associated with a reduction in LVEF at follow-up compared with non-paced patients; 3)-1.93% vs -6.89% p=0.008, 4)1.29% vs -4.78% <0.001, 5)-6.2% vs -4.78% p=0.763 6)0.49% vs -6.89% p=0.002 (Figure 2). Paced patients were older(78.0±8.7 vs 75.7±11.2 years p=0.001), more often male(68.0 vs 54.2% p=<0.001) and were more comorbid (CKD 34.3 vs 22.3% p=<0.001, IHD 47.2 Vs 43.5% vs p=0.054, T2DM 30.0 vs 21.7 p=0.004)than non-paced patients. AF was similar in both groups (47.0 vs 46.7 p=0.978).

Each accumulated PICM risk factor reduces TI by -1.31 ohms in paced but not non-paced patients. Similarly, when RVP >20% there is a greater reduction in LVEF at follow up for each accumulated PICM risk factor compared with RVP <20%. A risk factor score may support prediction of pacing induced cardiomyopathy.Figure 1  Figure 2