VDD stimulation is accepted as alternative mode of cardiac pacing to DDD in patients with atrio-ventricular (AV) conduction block and preserved sinus node function (SA).
Aim of the study: An attempt has been made to determine the relationship between width and amplitude of the P wave obtained during assessment the patient for the implantation procedure and the effectiveness of AV synchronization (PAS).
Material and methods: The study involved a group of 65 patients (43 male, 22 female), aged 66.6 +/- 12.7 with clinically significant disturbances of AV conduction, who did not reveal symptoms of concomitant disturbance in SA node automaticity. The width and amplitude of the P wave of the surface ECG were studied prior to the implantation procedure. Follow-up was carried out 3-4 days and 1, 3, 6 and 12 months after the procedure. The effectiveness of PAS was estimated by event counter read-out.
Results: Over the 12-month follow-up, the average value of the PAS coefficient was 95% for the entire group of patients. In 74% (subgroup A) synchronization was highly effective (PAS > or = 95%); in the remaining 26% (subgroup B) PAS occasionally fell below 95%. A statistically significant correlation between the width of the P wave of the surface ECG and the effectiveness of PAS was clearly demonstrated. In subgroup B, P wave was longer than in subgroup A (105 +/- 16 vs. 94 +/- 14 ms; p < 0.005). The width of P wave above 100 ms was the cutoff value of the ROC curve predicting PAS < 95%.
Conclusions: The width of P wave obtained from surface ECG is correlated with effective AV synchronization. The value above 100 ms was predisposed to atrial undersensing.