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Electrophysiologic properties of nitroglycerin in man

1977; Elsevier BV; Volume: 94; Issue: 3 Linguagem: Inglês

10.1016/s0002-8703(77)80478-x

1097-6744

Lawrence Gould, C.V. Ramana Reddy, Windell Chua, C.R. Narayana Swamy, Jean-Claude Dorismond,

Blood Pressure and Hypertension Studies

His bundle electrograms were obtained in 13 patients before and after the sublingual administration of nitroglycerin. The P-A interval, measured in all patients, was 32 ± 3 msec. (mean ± standard error of the mean) before and after nitroglycerin (N.S.). The mean A-H interval during sinus rhythm in all patients was, respectively 112 ± 15 msec. before, and 103 ± 14 after nitroglycerin (p < 0.001). The mean A-H interval at a paced rate of 140/min. in 11 patients was 150 ± 14 msec. before and 130 ± 10 msec. after nitroglycerin (p < 0.02). The mean H-V interval was 44 ± 3 before and after nitroglycerin (N.S.). The mean sinus rate and sinus recovery times were, respectively, 70 ± 6 beats/min. and 1097 ± 184 msec. before and 83 ± 7 beats/min. and 847 ± 80 msec. after nitroglycerin (p < 0.001 and N.S.). The blood pressure fell in every patient after nitroglycerin. The mean values were, respectively 133/78 ± 3/3 mm. Hg before and 119/70 ± 4/2 mm. Hg after nitroglycerin (p < 0.001). Functional and effective refractory periods were measured (in milliseconds) with the use of the atrial extrastimulus technique. The mean atrial effective refractory period (12 patients) were 280 ± 12 msec. before and 259 ± 9 msec. after nitroglycerin (p < 0.01). The mean atrioventricular (A-V) nodal functional refractory period (13 patients) and effective refractory period (6 patients) were 460 ± 36 and 442 ± 70 msec. before and 429 ± 35 and 401 ± 63 msec. after nitroglycerin (p < 0.001 and p < 0.05). The mean relative refractory period of the His Purkinje system (5 patients) was 428 ± 15 before and 392 ± 16 msec. after nitroglycerin (p < 0.01). In summary, nitroglycerin increased sinus nodal automaticity as manifested by an increase in sinus rate and improved A-V nodal conduction as manifested by a reduction in the A-H interval and the A-V nodal functional and effective refractory periods. This is probably explained by the systemic hypotension produced by nitroglycerin which reflexly will increase sympathetic drive to the heart and decrease vagal tone.