Abstract 2457: Ventricular Function After Long-Term Single-Site Pacing for Complete Heart Block
Background: Pts with complete heart block (CHB) often undergo long-term single-site right ventricular (RV) pacing. Left ventricular (LV) function over time in these pts has not been well studied.
Objectives: To evaluate LV function in pts with normal baseline function and long-term RV pacing due to CHB.
Methods: Retrospective review of pacemaker pts followed at one institution 1980 –2005. Inclusion criteria: isolated CHB or CHB with minor structural heart disease (SHD), follow-up >1 year, normal LV function prior to implant, no significant valvar dysfunction, and adequate echo imaging.
Results: Of 57 eligible pts, median follow-up time was 6.9 yrs (range 1.7–19.9). Diagnoses were isolated CHB in 40 (70%) and CHB with SHD in 17 (30%). Median age at pacemaker implant was 1.4 yrs (0 –36.2), and median paced QRS duration was 152 msec (114 –202). Pacing mode was DDD in 34 (59%). Most common lead locations were apical in 41 (72%) and RV outflow tract in 8 (14%). On most recent echo, mean ejection fraction (EF) was 58% (±8). Pts with SHD had lower mean EFs on recent echo (53% (±7) vs 61% (±8), p=0.002). Other variables, including lead location, pacing mode, duration of pacing, and age at first implant were not correlated with lower EF. A total of 40 pts had more than one echo available for comparison of function over time. Median time span between echos was 5.8 yrs (range 0.5–20.1 yrs). EF decreased a by a mean of 3% on follow-up (±12, p=0.11). End-diastolic volume Z scores decreased slightly over the study period (mean −0.7, ±2.8, p=0.11). Of the 31 pts paced >3 years between echos, mean decrease in EF was 5% (±10, p=0.01). Of the 9 SHD pts with >1 echo, EF decreased by a mean of 7% (±23, p=0.10). In all, 19 pts had EFs < 55% on follow-up echo (range 42–54%). Of these, 10 (52%) had SHD. No pts in the cohort developed clinical heart failure.
Conclusions: Single-site RV pacing in pts without pre-existing ventricular dysfunction is not associated with marked progressive ventricular dysfunction or enlargement on intermediate follow-up. This suggests that routine multi-site ventricular pacing in these pts is not likely to be warranted. Additional studies to help identify candidates for traditional single-site pacing or for multi-site ventricular pacing are needed.