[Complete vagal block in the clinical evaluation of sinus bradycardia]

The authors determined the discriminant threshold of sinus rate (SR) and the degree of its increase after complete vagal block (0.04 mg/kg of atropine sulfate IV) in 34 patients with symptomatic sinus bradycardia, the day after electrophysiological evaluation (performed before and after autonomic block with propranolol 0.2 mg/kg and atropine sulfate 0.04 mg/kg IV). Patients were divided into two groups. Group I included 19 patients (age 43.3 +/- 8) with normal intrinsic sinus automatism with normal intrinsic heart rate (IHRo) and normal intrinsic corrected sinus recovery time (intrinsic CSRT) (< 425 ms). Group II consisted of 15 patients (age 51.8 +/- 12) with abnormal intrinsic sinus automatism with abnormal IHRo and/or intrinsic CSRT (> 425 ms). Following the atropine test, SR in the individuals of Group I increased from 58.1 +/- 11.7 bpm to 103 +/- 16 bpm (delta% = 80 +/- 37), while in Group II it increased from 52.8 +/- 12 bpm to 82.15 bpm (delta% = 55.4 +/- 21). The discriminant threshold of SR and of its percentage increase (delta%) were 91 bpm and 68% respectively, with a sensitivity of 71 and 81% and a specificity of 73 and 63%. The predictive value of a positive test of SR (< 91 bpm) and of its delta% (< 68%) were 71 and 64% respectively. That of a negative test of SR (> 91 bpm) and of its delta% (< 68%) were 73 and 80% respectively. The total predictive accuracy of SR and of its percentage increase was the same: 72%.(ABSTRACT TRUNCATED AT 250 WORDS)