Changes in myocardial repolarization in patients undergoing balloon valvuloplasty for congenital pulmonary stenosis: evidence for contraction-excitation feedback in humans.
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 alter 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 less than .001) and the QTc increased concurrently (409.1 +/- 24.3 to 440.7 +/- 28.0 msec, p less than .001) after successful valvuloplasty. The increase in QTc was most marked for those patients with a greater than 30 mm Hg decrease in right ventricular pressure (40.0 +/- 23.3 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 +/- 21.9, p less than .001) after successful valvuloplasty, confirming that the QTc 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 less than .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.
Levine
J H
JH
Divisions of Cardiology, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD 21205.
Guarnieri
T
T
Kadish
A H
AH
White
R I
RI
Calkins
H
H
Kan
J S
JS
D000200:Action Potentials; D002404:Catheterization; D004562:Electrocardiography; D004594:Electrophysiology; D005246:Feedback; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D009200:Myocardial Contraction; D011666:Pulmonary Valve Stenosis / Q000151:congenital* / Q000628:therapy