title: Strength-interval relation in the human ventricle: effect of procainamide.
abstract: The effects of procainamide on strength-interval relations were evaluated in 18 patients. At plasma concentrations of 4.3 to 13.6 micrograms/ml procainamide had minimal effects on threshold current in late diastole, but in early diastole it shifted the strength-interval curve to the right. The basic strength-interval relation (that is, decreasing refractory period as current is increased) was not altered. The control refractory period decreased by a mean of 44 ms as the current was increased from threshold to 10 mA, whereas a mean decrease of 42 ms was observed after procainamide. However, the steep portion of the strength-interval curve(absolute refractory period) was shifted to longer coupling intervals by a mean value of 24 ms. These findings suggest that procainamide may primarily affect active membrane properties, but exert little net effect on passive membrane properties late in diastole.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000328:Adult; D000368:Aged; D004562:Electrocardiography; D004594:Electrophysiology; D006321:Heart / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects; D006801:Humans; D007263:Infusions, Parenteral; D008566:Membranes / Q000187:drug effects; D008875:Middle Aged; D011342:Procainamide / Q000008:administration & dosage* / Q000097:blood; D016276:Ventricular Function
chemical_list: D011342:Procainamide