Utility of the surface ECG before VDD pacemaker implantation

VDD pacemakers may be implanted in the setting of atrioventricular block with preserved sinus function. Their main advantage over DDD pacemakers is use of a single lead. However, low-amplitude atrial electrograms (EGMs) recorded from the free-floating atrial electrode may lead to undersensing. There is currently no way of predicting EGM amplitude prior to implantation and to thus identify candidates who may be safely implanted with a VDD pacemaker.

We sought to investigate whether the P-wave amplitude measured on the standard surface ECG correlates with the atrial EGM amplitude measured by the single-pass lead at implantation.

Data on 122 patients implanted with a VDD pacemaker at our institution were reviewed. Atrial EGM amplitudes measured at implantation by the single-pass lead were correlated with the maximal P-wave amplitude on the surface ECG recorded just prior to implantation.

There was a highly significant correlation between the maximal P-wave amplitude on the surface ECG and the atrial EGM (Pearson's correlation 0.313, P<0.001). Multivariate analysis showed that maximal P-wave amplitude was independently associated with atrial EGM amplitude (p=0.003). For the overall population, an EGM amplitude of <0.9 mV was present in only 11/122 (9%) cases. An atrial EGM amplitude of <0.9 mV was found in 10/69 (14%) of patients with a maximal surface P-wave < or =0.1 mV but only in 1/53 (2%) of those with >0.1 mV (p=0.023).

Low-amplitude atrial EGMs at implantation are found in a minority of patients with single-pass leads. However, patients with a maximal surface P-wave amplitude of >0.1 mV are especially unlikely to have a low atrial EGM amplitude and may be good candidates for a VDD pacemaker.