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Validation of a Noninvasive Measure of Local Myocardial Repolarization in a Conscious Human Model:
Author(s) -
DOUGLAS LEE S.,
DORIAN PAUL,
GEIST MICHAEL,
DAVIES EDWARD,
BARR AIALA,
DUNNE CATHERINE,
PAQUETTE MINEY,
NEWMAN DAVID
Publication year - 1999
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1111/j.1540-8167.1999.tb00292.x
Subject(s) - repolarization , cardiology , medicine , stimulus (psychology) , heart rate , stimulation , electrocardiography , endocardium , ventricular repolarization , electrophysiology , blood pressure , psychology , psychotherapist
Rate Adaptation of Myocardial Repolarization. Introduction : A commercial pacemaker sensor measure of the unipolar endocardial stimulus to T wave interval may accurately reflect changes in the monophasic action potential duration at 90% repolarization (APD 90 ). This sensor system was used to study the kinetics of adaptation of repolarization duration to changes in heart rate in humans. Methods and Results : Patients were studied using an external pacemaker capable of displaying all stimulus to T wave intervals for each paced beat. Right ventricular stimulation was delivered via the pacemaker and compared simultaneously to APD 90 . Steady‐state pacing was simulated by 60 seconds of pacing at cycle lengths (CLs) 350 to 700 msec. Adaptation to a new ventricular rate was analyzed with a sudden 200‐msec decrease in CL. The relation between repolarization measure and steady‐state CL (n = 16) was linear with a slope of 0.16 and 0.19 for APD 90 and stimulus to T wave interval, respectively (P = NS). The adaptation of both repolarization measures to a sudden change in rate were best modeled by a biexponential function. Stimulus to T wave interval exhibited a parallel course to APD 90 , and an analysis of normalized differences between APD 90 and stimulus to T wave interval followed an approximately normal distribution, with 93.5% of the paired differences within 2 SD of the mean. Conclusion : A pacemaker sensor measure of stimulus to T wave interval accurately parallels APD 90 , during both steady‐state and sudden changes in rate. Repolarization in human endocardium follows a linear relation to steady‐state CL and adapts to a new rate with a biexponential function. This model represents a novel method for studying human cardiac repolarization.