Alterations in ventricular loading conditions lead to changes in action potential duration and arrhythmias via contraction-excitation feedback; a decrease in load leads to prolongation of repolarization. To determine whether changes in right ventricular load after ventricular repolarization in man, the corrected QT interval, a measure of overall ventricular repolarization, was measured in 32 patients before and after valvuloplasty for pulmonary stenosis. Right ventricular systolic pressure decreased (82.5 ± 30.7 to 40.5 ± 9.5 mm Hg, p<.001) and the QT(c) increased concurrently (409.1 ± 24.3 to 440.7 ± 28.0 msec, p<.001) after successful valvuloplasty. The increase in QT(c) was most marked for those patients with a greater than 30 mm Hg decrease in right ventricular pressure (40.0 ± 22.3 vs 16.3 ± 21.3 msec, p=.006). In a subset of seven patients in whom monophasic action potentials were recorded, monophasic action potential duration, a measure of local repolarization, was prolonged (230.0 ± 24.3 vs 216.9 ± 21.0, p<.001) after successful valvuloplasty, confirming that the QT(c) prolongation reflected changes in local ventricular repolarization. In addition, during nine acute right ventricular outflow tract occlusions in a subset of six patients, monophasic action potential duration shortened (206.6 ± 17.6 vs 221.7 ± 20.9 msec, p<.01) and early afterdepolarizations developed consistent with contraction-excitation feedback. These data suggest that, in humans, changes in mechanical load are associated with changes in ventricular repolarization consistent with contraction-excitation feedback.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)