Underrecognized entity of the transient rise in the atrial capture threshold early after dual-chamber pacemaker implantation

Rate-dependent pacing failure after pacemaker implantation: Novel insights into the mechanism of using adenosine

An 82-year-old woman received pacemaker implantation for sick sinus syndrome. Two days after the implantation, electrocardiography showed 2:1 atrial pacing failure, followed by a bradycardia-dependent increase in the atrial pacing threshold during a pacemaker examination. However, transient 1:1 atrial pacing capture recovered by adenosine triphosphate (ATP) administration, which was performed to evaluate the bradycardia-dependent pacing failure mechanism. We considered this phenomenon to be caused by Phase 4 depolarization and avoided replacing this atrial lead. Three weeks later, the atrial pacing threshold had improved. We report the potential role of Phase 4 depolarization in a bradycardia-dependent increase in pacing threshold by using ATP.

Mechanistic implication of decreased plasma atrial natriuretic peptide level for transient rise in the atrial capture threshold early after ICD or CRT-D implantation

PURPOSE

Despite the use of steroid-eluting leads, a transient but not persistent rise in the atrial/ventricular capture threshold (TRACT/TRVCT) can occur early after pacemaker implantation in patients with sick sinus syndrome. This study aimed to assess the prevalence, predictors, and mechanisms of TRACT/TRVCT in patients with heart failure undergoing implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy (CRT) implantation.

METHOD

One hundred twenty consecutive patients underwent ICD (N = 70) or CRT (N = 50) implantation. Capture threshold was measured at implantation, 7-day, 1-month, and 6-month post-implantation. TRACT/TRVCT was defined as a threshold rise at 7 days by more than twice the height of the threshold at implantation, with full recovery during follow-up. Atrial and brain natriuretic peptide (ANP and BNP) levels were measured before implantation.

RESULTS

TRACT and TRVCT were observed in 13 (11%) and 10 (8%) patients, respectively. Patients with TRACT had lower ANP level (median 72 [42-105] vs. 99 [49-198] pg/mL, P = 0.06), lower ANP/BNP ratio (0.29 [0.20-0.36] vs. 0.50 [0.33-0.70], P < 0.01), lower atrial sensing amplitude (2.0 ± 0.8 vs. 2.7 ± 1.3 mV, P = 0.02), and lower left ventricular ejection fraction (32 ± 12 vs. 40 ± 14%, P = 0.04) than those without TRACT. TRACT recovered within 1 month, whereas TRVCT recovered within 6 months. In multivariable analysis, ANP/BNP ratio was the only independent predictor of TRACT (OR, 0.018; 95% CI, 0.001-0.734; P = 0.034).

CONCLUSIONS

Atrial degenerative change characterized by lower ANP/BNP ratio was associated with the occurrence of TRACT in patients with heart failure. TRVCT could also occur, but it required a longer recovery time than TRACT.