Reliability of single-lead VDD atrial sensing and pacing during exercise

If atrial sensing ability of a single-lead VDD pacemaker is well accepted a t rest, the detection quality by atrial floating electrodes remains less re cognized during exercise. The aim of this study was to verify, during tread mill test and a continous telemetry, the atrial tracking performance using four different leads technologies. From November 1994 to July 1997 21 patie nts (71.3 +/- 6.3 years old, 7 female, cardiopathy: 57%) were paced for iso lated high degree (permanent: 13, paroxystic: 8) AV block. The implanted de vices were the Vitatron Saphir/Brillant lead (13 patients), Intermedics Uni ty/425/04-13 lead (5 patients), Pacesetter Addvent (2 patients), and Biotro nik Eikos (1 patient). The acute atrial signal amplitude was 1.66 +/- 0.75 mV. The treadmill test used the chronotropic assessment exercise protocol a fter pacemaker reprogramming to detect atrial undersensing (A V delay less than or equal to 120 ms, no hysteresis, no flywheel, upper rate increase). The mean delay was 31.1 weeks (range 1-100). The testing duration was 6.1 /- 2.3 minutes, the number of steps was 3.3 +/- 1.3 per patient, and the pe ak exercise rate was 135 +/- 19 beats/min. At rest, complete atrial trackin g was complete in 90% of the patients, and during testing in only 23.8% of the patients, while AV synchronization > 95% was present in 57.1%, > 90% in 71.4%, and > 85% in 90.4% of patients (Vitatron 13/13, Intermedics 3/5, Bi otronik 1/1, and Pacesetter 1/2). During the recovery period synchronizatio n was always > 95%. The mean P wave amplitude at rest was 1.1 +/- 0.5 mV; d uring the first step, 1.04 +/- 0.61 mV; second step, 0.94 +/- 0.53 mV; thir d step, 0.82 +/- 0.58 mV; fourth step, 0.67 +/- 0.39 mV; and during recover y, 1.13 +/- 0.67 mV. The mean P wove decrease signal at peak of exercise is 0.21 mV(from -1.31 to +0.5). In fact, P wave variations have several patte rns: a decrease was measured in 7 patients, an increase in 2 patients, and no significant change in 7 patients. Single-lead VDD P wave identification during exercise wets almost accurate. However, often there was progressive lowering of atrial sensing with transient loss of AV synchrony.