Electrical Cardioversion in Patients with Recently Implanted Cardiac Implantable Electronic Devices: Initial Safety Data from a Large Tertiary Care Center

Background: Electrical cardioversion (ECV) is often deferred in patients with recently implanted cardiac implantable electronic devices (CIEDs) due to safety concerns. However, data and official recommendations are lacking.

Objective: The aim was to assess the safety of ECV <6 weeks after CIED implantation. 

Methods: In a large tertiary care center, electronic patient records were retrospectively analyzed. Patients who underwent ECV <6 weeks after CIED-implantation were included. CIED interrogation was performed immediately after ECV, and follow-up CIED interrogation was performed ≥6 weeks post ECV. 

Results: Twenty-eight patients (50% female, mean age 72±11 years) with a total of 54 recently implanted leads underwent ECV of atrial tachyarrhythmias 20±15 days after CIED implantation (23 x dual-chamber [DC]- pacemaker [PM], 1 single-chamber [SC]-PM, 2 SC-implantable cardioverter-defibrillator [ICD], 1 DC-ICD, 1 CRT-D). Indication for CIED implantation was sick-sinus syndrome in 14 (50%), AV-block in 10 (36%), bradyarrhythmia in 1 (4%), primary prevention in 1 (4%), and secondary prevention in 2 (7%) patients, respectively. ECV was performed with a mean of 1.25±0.6 shocks (162±50 J). A statistically significant increase in RV stimulation threshold amplitude (0.50 [interquartile range (IQR) 0.50-0.75] vs. 0.75 [IQR 0.50-0.87] V; p=0.005) and a decrease in RA lead impedance were observed (437 [IQR 388-500] vs. 420 [IQR 351-468] Ω; p=0.008, Table).  There were no further significant changes in device parameters. In follow-up interrogations after 327±74 days, no significant changes were seen other than expected standard battery depletion (3.04 [IQR 2.79-3.09] to 2.90 [IQR 2.79-3.01] V; p=0.011). One case of RA lead exit block was observed post ECV (Figure). Another patient showed microdislocation after RA lead implantation close to the tricuspid valve which cannot be clearly attributed to ECV. Both cases required RA lead revision. One patient showed RV lead exit block with high a pacing threshold (4.9V/1.0ms) prior to ECV, which was considered unrelated to ECV (Figure).

Conclusion: In the majority of cases included in this initial report, ECV in patients with recently implanted CIEDs was safe, with only minimal, clinically insignificant changes in CIED parameters. However, two events possibly related to ECV in this small patient cohort show the need for more data to evaluate the risk for adverse events.

Table: 

CIED parameter	Pre ECV Median (IQR)	Post ECV Median (IQR)	P-value
Battery voltage (V)	3.05  (2.79-3.10)	3.04 (2.79-3.09)	0.830
RA lead impedance (Ω)	437  (388-500)	420 (351-468)	0.008
RA lead sensing (mV)	1.75  (0.70-3.05)	1.50 (0.90-2.80)	0.575
RA lead threshold, amplitude (V)	0.70 (0.50-1.00)	0.75 (0.58-1.00)	0.236
RA lead threshold, pulse width (ms)	0.40 (0.40-0.40)	0.40 (0.40-0.40)	0.317
RV lead impedance (Ω)	555 (435-616)	513 (409-611)	0.100
RV lead sensing (mV)	9.9 (7.6-12.0)	11.2 (6.6-12.0)	0.266
RV lead threshold, amplitude (V)	0.50 (0.50-0.75)	0.75 (0.50-0.87)	0.005
RV lead threshold, pulse width (ms)	0.40 (0.40-0.40)	0.40 (0.40-0.40)	1.000

Figure: