Study On The Electrophysiologic Mechanism Of The Short P-R Interval By TEAP Together With Medicine Experiment

Objective:To explore the electrophysiologic mechanism of the short P-R intervalMethods:An electrophysiological exploration was carried out in 30 patients presenting a syndrome of a short P-R interval(<0.12s) and a normal QRS wave (group 1). compared to a reference group of 30 patients who did not present this abnormality (group 2).There were 3 steps according to the possible mechanism:1. The group 1 were injected with propranolol and atropine, completely blocking the domination of the heart autonomic nervous system, then compared the P-R interval before and after the injection of the drugs.2. to compare the electrophysiologic parameters between the two groups after non-programmed stimulation(S1S1) and programmed ectopic stimulation(S1S2) by transesophageal atrial pacing(TEAP).3. the group 1 were injected with verapamil 5mg, received the same examination as the step two. then compared the electrophysiologic parameters before and after the injection of the verapamil.Results: 1. after the injection of propranolol and atropine,the P-R interval of the group 1 changes from 0.100±0.009s to 0.102±0.008s(p>0.05).2. the S1R interval, the wenckbach point of atrioventricular conduction, the AVERP of the two groups are 153.3±16.0ms,184.3±21.9ms; 213.7±12.5 ppm,167.3±20.5ppm; 228.7±22.lms,332.0±43.8ms; respectively.The differences are all significant(p<0.01)3. after the injection of the verapamil, the S1R interval of the group 1 extends from 153.±16.0ms to 184.0±23.7ms(p<0.01); the wenckbach point shortens from 213.7±12.5 ppm to 183.7±15.4ppm(p<0.01); the AVERP extends from 228.7±22.1ms to 305.3±±27.0ms(p<0.01).Conclusions:1. Neural factor is not the main mechanism of short P-R intervals.2. short P-R intervals are characterized by enhanced atrioventricular nodal conducton(EVANC).3. We do not find James or Brechenmacher fibers in group 1, therefore they are not the main mechanism of short P-R intervals.