Experience with activity sensing rate responsive ventricular pacing. A study based upon assessment of exercise tolerance.

Fourteen patients (mean age 41 years) who received rate responsive activity sensing VVI pacemakers were studied to evaluate the relationship between the rate response and exercise tolerance by analysing the symptom limited maximum treadmill time both during fixed rate VVI oacubg abd dyrubg VVI + activity mode pacing (RRP). The proper functioning of RRP mode was confirmed by Holter monitoring in all. The indications for pacing were, sino-atrial block with high grade AV block, tachybrady syndrome, atrial fibrillation with complete heart block, congenital complete heart block and persistent slow junctional rhythm. Basic rate was programmed to 70 PPM in both pacing modes; rate response and activity threshold were programmed to 5 and medium respectively. The order in which two pacing modes were tested was chosen randomly. The maximum treadmill time (MTT) was 25.4% longer in the RRP than in VVI mode with a mean of 11.4 minutes in RRP and 8.5 mins in VVI(p less than 0.01). for the subgroup of patients who demonstrated paced only rhythm the average increase in MTT was 31.4% with a mean of 11.8 minutes in RRP and 8.1 mins in VVI (p less than 0.01). Five patients who showed intermittent spontaneous rhythm, increased their average MTT by 22.3% with a mean of 11.2 minutes in RRP and 8.7 mins in VVI mode (p less than 0.05). During RRP a significance positive correlationship was seen between MTT and the increase in heart rate (N = 14, r = 0.85, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)