With the aim to detect dysfunction of pacing leads, most present-day p
acemakers measure pacing impedance by means of real-time telemetry. Th
e recommended setting for impedance measurement is 5.0 V for pulse amp
litude and 0.5 ms for pulse duration. Availability of reliable setting
s would facilitate impedance measurements during follow-up. The purpos
e of the present study wets twofold: (1) to assess whether telemetrica
lly measured impedance of the studied pacemaker is similar to impedanc
e measured at implantation; and (2) to evaluate whether the pacemaker
setting influences telemetrically measured impedance. Sixty-five conse
cutive patients receiving VVI(R) pacemakers were studied; in all patie
nts, impedance measured at implantation by a pacing system analyzer wa
s compared to measurements obtained telemetrically within 1 day after
implantation. In 44 other patients, impedance was determined 3 months
after implantation at 60 and 120 ppm (n = 44), twice at 60 ppm (n = 42
), and 12 months after implantation at 60 ppm (n = 34). For each measu
rement, pulse amplitude was programmed to 0.8, 2.6, 2.5, 5.0, and 8.0
V, and pulse duration to 0.05, 0.25, 0.50, and 1.00 ms. Impedance at i
mplantation (606 +/- 113 ohms) did not differ from the data obtained w
ith telemetry (629 +/- 113 ohms; P = NS). Different pacing rates, repe
at measurements, and follow-up time failed to show any influence on im
pedance. Measurement tolerance was < 10% for 15 of 19 studied settings
other than 5.0 V and 0.5 ms. Conclusion: The studied pacemakers provi
de reliable data for telemetrically measured impedance. Telemetrical i
mpedance does not necessarily have to be measured at 5.0 V and 0.5 ms.
These findings should be considered for measurement and interpretatio
n of real-time telemetry impedance during follow-up.