Learn More
BACKGROUND Cardiac memory (CM) refers to T-wave changes induced by ventricular pacing or arrhythmia that accumulate in magnitude and duration with repeated episodes of abnormal activation. We report herein the kinetics of long-term CM and its association with the ventricular action potential. METHODS AND RESULTS Dogs were paced from the ventricles at(More)
OBJECTIVE Our goal was to study rate adaptation of atrial action potentials in non-steady and steady states to further our understanding of mechanisms determining inducibility and stability of atrial fibrillation. METHODS We used standard microelectrode techniques to examine the characteristics of steady-state action potentials paced at regular cycle(More)
Gonadal steroids are thought to be important determinants of gender-related differences in electrophysiology, such as the longer rate-corrected QTc intervals in women and the incidences of some clinical arrhythmias. We studied the chronic effects of gonadal steroids on cardiac action potentials (APs) using standard electrophysiological techniques. Papillary(More)
BACKGROUND Cardiac memory refers to an altered T-wave morphology induced by ventricular pacing or arrhythmias that persist for variable intervals after resumption of sinus rhythm. METHODS AND RESULTS We induced long-term cardiac memory (LTM) in conscious dogs by pacing the ventricles at 120 bpm for 3 weeks. ECGs were recorded daily for 1 hour, during(More)
BACKGROUND Anisotropic conduction properties may provide a substrate for reentrant arrhythmias. We investigated the age-dependent changes of structural and functional anisotropy in isolated right atria from infant (1 to 2 months), young (6 to 12 months), and old (6 to 10 years) dogs. METHODS AND RESULTS The histology of the mapped atrial tissues (a small(More)
OBJECTIVE To determine whether I(Na) and I(CaL) are altered in function/density in right atrial (RA) cells from dogs with chronic atrial fibrillation (cAF dogs, episodes lasting at least 6 days) and whether the changes that occur differ from those in dogs with nonsustained or brief episodes of fibrillation (nAF dogs). METHODS Using whole cell voltage(More)
BACKGROUND The classic calciotropic hormone parathyroid hormone (PTH) and its paracrine factor parathyroid hormone-related protein (PTHrP) both increase heart rate. METHODS AND RESULTS We used standard electrophysiological techniques to study the effects of PTH and PTHrP on isolated rabbit sinus node, isolated canine Purkinje fibers, and disaggregated(More)
BACKGROUND Intravenous verapamil has been reported to prevent electrical remodeling induced by rapid atrial excitation of several minutes to several hours. However, the clinical efficacy of verapamil when taken orally and daily remains controversial. PURPOSE We attempted to demonstrate our hypothesis that if verapamil prevents calcium (Ca) overload, its(More)
Calcium overload plays a key role in the development of atrial electrical remodeling. The effect of an L-type Ca channel blocker in preventing this remodeling has been reported to be short lasting, partly due to down-regulation of this channel and persisting Ca entry through the T-type Ca channel. To prove if efonidipine, a dual L- and T-type Ca channel(More)
BACKGROUND Calcium overload plays a major role in the development of electrical and mechanical remodeling during atrial fibrillation, but the potential of verapamil, a Ca blocker, for preventing atrial electrical remodeling remains controversial. METHODS AND RESULTS Pacing and recording electrodes were sutured to the right atrium in 16 dogs. After a 5-day(More)