“… heparin … quinidine , there were significant increases in the mean (+/- SD) right ventricular effective refractory period (266 +/- 24 versus 279 +/- 23; p less than 0.025), free … +/- 0.1 microgram/ml; p less than 0.001) but no changes in heart rate, corrected QT interval, or total plasma quinidine concentration.”