Comparative Functional Effects of Chronic Ventricular Demand and Atrial Synchronous Ventricular Inhibited Pacing

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Abstract
We compared the effects of chronic ventricular inhibited (VVI) and atrial synchronous ventricular inhibited (VDD) pacing on functional capacity in 8 patients with complete atrioventricular heart block. Permanent VDD (Medtronic #2409, ASVIP) pacemakers were implanted in four men and four women (age range 27-76 years, mean 58.9 +/- 18.4 years), and randomly assigned to a three-month period of VDD or VVI pacing in this single blinded, crossover study. Functional capacity was assessed by questionnaire, graded treadmill exercise testing and radionuclide angiocardiography prior to pacemaker implant and following each pacing period. Following 3 months of pacing in each of VVI and VDD pacing modes, maximum heart rate (83.4 +/- 14 vs 134.9 +/- 16.4 beats/min, p less than 0.001) and double product (147.5 +/- 58.3 vs 218.9 +/- 52.7, p less than .001) were greater with VDD pacing. Although exercise duration on treadmill exercise testing (5.3 +/- 2.9 vs 6.9 +/- 3.1 minutes, p less than 0.1) was greater in the VDD mode, the difference was not significant. Similarly, there was no significant difference in functional capacity as measured by questionnaire scores (50.1 +/- 8.4 vs 46.9 +/- 8.9, p less than 0.1) or in left ventricular ejection fraction for the two pacing modes (.54 vs .55, p less than .5). Only one patient reported a subjective improvement with physiologic (VDD) pacing, whereas the remaining patients stated no preference. We conclude that VDD pacing offers improved maximal cardiac work during exercise compared to VVI pacing.(ABSTRACT TRUNCATED AT 250 WORDS)