Relationship between the U wave on electrocardiogram and the midmyocardium of the left ventricular wall.
OBJECTIVE
To investigate the relationship between the U wave on electrocardiogram and the midmyocardium in rabbit left ventricle free wall in vivo.


METHODS
The monophasic action potentials in the epicardium, midmyocardium, and endocardium of the left ventricle free wall were recorded simultaneously in 16 rabbits. The rabbits were then given an intravenous injection of Sotalol (1, 1.5 and 2.0 mg/kg) in 30 minutes intervals, and measurements were taken.


RESULTS
In the basic condition, there were no U wave on electrocardiogram. The U wave appeared after the intravenous Sotalol at 1.5 mg/kg, and the U wave became greater with increased dosage of intravenous Sotalol (2 mg/kg). The repolarization duration of the midmyocardium was prolonged longer than that of the epicardium and endocardium by Sotalol, and the repolarization duration of the epicardium coincided with the apex of the T wave, The repolarization duration of the midmyocardium coincided with the end point of the U wave.


CONCLUSIONS
The U wave may originate from the delayed repolarization of the midmyocardium.
Department of Cardiology, Tongji Hospital Tongji Medical University, Wuhan 430030, China.
Cuntai
C
Zhang
Yuntian
Y
Li
Zaiying
Z
Lu
Jie
J
Wu
Chen
C
Wang
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D004699:Endocardium / Q000187:drug effects / Q000502:physiology; D006352:Heart Ventricles / Q000187:drug effects; D010496:Pericardium / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D013015:Sotalol / Q000494:pharmacology; D016276:Ventricular Function
D000889:Anti-Arrhythmia Agents; D013015:Sotalol