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Strength-interval relation in the human ventricle: effect of procainamide
The American Journal of Cardiology
|April 1, 1980
Summary
Procainamide minimally impacts cardiac electrical properties late in diastole but affects the strength-interval relationship in early diastole. This antiarrhythmic drug may influence active membrane function more than passive properties.
Area of Science:
- Cardiac Electrophysiology
- Pharmacology
Background:
- Understanding the effects of antiarrhythmic drugs on cardiac electrophysiology is crucial for managing arrhythmias.
- Procainamide is a Class IA antiarrhythmic agent used to treat various cardiac rhythm disorders.
Purpose of the Study:
- To investigate the impact of procainamide on cardiac strength-interval relationships.
- To determine how procainamide affects the refractory period and membrane properties during different phases of diastole.
Main Methods:
- Evaluated strength-interval relations in 18 patients receiving procainamide.
- Measured threshold current and refractory periods at varying plasma concentrations (4.3–13.6 µg/mL).
- Assessed changes in the steep portion of the strength-interval curve, representing the absolute refractory period.
Main Results:
- Procainamide showed minimal effect on threshold current in late diastole.
- In early diastole, procainamide shifted the strength-interval curve to the right.
- The basic strength-interval relation remained unaltered, but the absolute refractory period shifted to longer coupling intervals by a mean of 24 ms.
Conclusions:
- Procainamide appears to primarily affect active membrane properties of cardiac cells.
- The drug exerts little net effect on passive membrane properties in the late diastolic phase.
- Findings suggest a nuanced impact of procainamide on cardiac electrophysiological parameters.