Fig. 1. Rate-dependent right ventricular electrophysiologic effects of thoracic epidural anesthesia (TEA; diamonds) and autonomic nervous system blockade (ANS) in the presence of continued TEA (triangles) in awake dogs (n = 7) in comparison to control (upside down triangles); mean ± SD. Right ventricular endocardial effective refractory period (ERP;A ) and monophasic action potential duration at 90% repolarization (MAP90 RV;B ) are plotted against cycle length (I–III). Example of monophasic action potential shortening with decreasing cycle length during control conditions (I), with TEA (II), and with ANS in the presence of continued TEA (III).