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Strength-interval relation in the human ventricle: Effect of procainamide

1980; Elsevier BV; Volume: 45; Issue: 4 Linguagem: Inglês

10.1016/0002-9149(80)90132-0

1879-1913

Joseph S. Camardo, Allan M. Greenspan, Leonard N. Horowitz, Scott R. Spielman, Mark E. Josephson,

Ion channel regulation and function

The effects of procainamide on strength-interval relations were evaluated in 18 patients. At plasma concentrations of 4.3 to 13.6 μg/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.