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Effects of Epinephrine on Right Ventricular Monophasic Action Potentials in the LQT1 Versus LQT2 Form of Long QT Syndrome: Preferential Enhancement of “Triangulation” in LQT1
Author(s) -
VIITASALO MATTI,
PAAVONEN KRISTIAN J.,
SWAN HEIKKI,
KONTULA KIMMO,
TOIVONEN LAURI
Publication year - 2005
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.2005.09404.x
Subject(s) - medicine , long qt syndrome , cardiology , qt interval , phenylephrine , repolarization , epinephrine , heart rate , restitution , anesthesia , blood pressure , electrophysiology , political science , law
Aims: To explore effects of epinephrine and phenylephrine on the behavior of right ventricular monophasic action potentials (MAPs) in symptomatic LQT1 and LQT2 patients.Methods and Results: We recorded endocardial MAPs from right interventricular septum at baseline and during epinephrine and phenylephrine infusions in six symptomatic DNA‐verified LQT1 (QTc 528 ± 83) and five LQT2 patients (QTc 527 ± 72) and in five control patients (QTc 381 ± 22). We measured MAP durations at 90% and at 50% levels of repolarization and their difference (MAP 50 to MAP 90 , a measure of MAP morphologic “triangulation”), during atrial pacing to characterize rate dependence of MAPs and repolarization phase 3 durations, respectively. Restitution kinetics were determined during atrioventricular sequential pacing, using the approach of empirical restitution rate. Epinephrine prolonged MAP 50 ‐to‐MAP 90 duration and increased the rate dependence of MAP 90 duration and increased restitution rate in type LQT1, but not in LQT2 patients nor in control subjects. Phenylephrine did not change MAP behavior. During epinephrine administration, both LQT1 and LQT2 patients had a ratio of the restitution rate of MAP to diastolic interval >1.0 at short diastolic intervals.Conclusion: Symptomatic LQT1 patients with prolonged baseline QTc intervals showed β‐adrenergic‐induced changes in MAPs (triangulation) known to be arrhythmogenic, thus giving insight to the difference in clinical triggers of life‐threatening arrhythmias between LQT1‐ and LQT2‐affected individuals.