The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Takeshi Suzuki - One of the best experts on this subject based on the ideXlab platform.
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atria selective prolongation by nip 142 an antiarrhythmic agent of refractory period and Action Potential Duration in guinea pig myocardium
Journal of Pharmacological Sciences, 2005Co-Authors: Tomoyuki Matsuda, Kentaro Takeda, Reiko Yamagishi, Miku Tamura, Hideki Nakamura, Noriko Tsuruoka, Tomoaki Saito, Haruko Masumiya, Takeshi SuzukiAbstract:Abstract NIP-142 is a novel benzopyran compound that was shown to prolong the atrial effective refractory period and terminate experimental atrial fibrillation in the dog. In the present study, we examined the effects of NIP-142 on isolated guinea pig myocardium and on the G-protein-coupled inwardly rectifying potassium channel current (acetylcholine-activated potassium current; IKACh) expressed in Xenopus oocytes. NIP-142 (10 and 100 µM) concentration-dependently prolonged the refractory period and Action Potential Duration in the atrium but not in the ventricle. E-4031 and 4-aminopyridine prolonged Action Potential Duration in both left atrium and right ventricle. Prolongation by NIP-142 of the atrial Action Potential Duration was observed at stimulation frequencies between 0.5 and 5 Hz. In contrast, the prolongation by E-4031 was not observed at higher frequencies. Tertiapin, a blocker of IKACh, prolonged Action Potential Duration in the atrium but not in the ventricle. NIP-142 completely reversed the carbachol-induced shortening of atrial Action Potential Duration. NIP-142 (1 to 100 µM), as well as tertiapin (0.1 to 100 nM), concentration-dependently blocked IKACh expressed in Xenopus oocytes; the blockade by NIP-142 was not affected by membrane voltage. In conclusion, NIP-142 was shown to prolong atrial refractory period and Action Potential Duration through blockade of IKACh which may possiblly explain its previously described antiarrhythic activity. NIP-142 has pharmacological properties that are different from classical class III antiarrhythmic agents such as atria specificity and lack of reverse frequency dependence, and thus appears promising for the treatment of supraventricular arrhythmia.
Robert F Gilmour - One of the best experts on this subject based on the ideXlab platform.
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Control of Action Potential Duration alternans in canine ventricular tissue
2010 Annual International Conference of the IEEE Engineering in Medicine and Biology, 2010Co-Authors: Uche Kanu, Robert F Gilmour, Shahriar Iravanian, David J. ChristiniAbstract:Cardiac Action Potential Duration alternans is characterized by a beat-to-beat alternation in Action Potential waveform. Its presence has been putatively linked to the onset of lethal cardiac arrhythmias. Previous studies, which have been limited to cardiac Purkinje fibers, have shown that closed-loop alternans control techniques, which apply a succession of externally administered cycle perturbations, provide ineffectual spatial alternans elimination. A more complete understanding of alternans control in the more clinically relevant ventricular tissue is needed. Here, we study the spatial dynamics of alternans and alternans control in arterially perfused canine right ventricular preparations using optical mapping. We quantified the spatial efficacy of alternans control across 2.5 cm of tissue, focusing primarily on differences in spatial control within several sub-regions of tissue. Our results provide a basis for future investigations into multi-electrode-based control interventions of alternans in cardiac tissue.
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dynamic restitution of Action Potential Duration during electrical alternans and ventricular fibrillation
American Journal of Physiology-heart and Circulatory Physiology, 1998Co-Authors: Marcus L Koller, Mark L Riccio, Robert F GilmourAbstract:The restitution kinetics of Action Potential Duration (APD) were investigated in paced canine Purkinje fibers (P;n = 9) and endocardial muscle (M; n = 9), in isolated, perfused canine left ventricl...
Stuart M Cobbe - One of the best experts on this subject based on the ideXlab platform.
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effects of the class iii antiarrhythmic drug dofetilide on ventricular monophasic Action Potential Duration and qt interval dispersion in stable angina pectoris
American Journal of Cardiology, 1992Co-Authors: Martin L Sedgwick, Henrik S Rasmussen, Stuart M CobbeAbstract:Abstract The effects of intravenous dofetilide on ventricular monophasic Action Potential Duration and effective refractory period at the right ventricular apex and outflow tract were studied in 18 patients (aged 37 to 70 years) with ischemic heart disease. Six patients received low-dose dofetilide as a 3 μg/kg loading dose over 15 minutes and a 1.5 μg/kg maintenance dose over 45 minutes; 6 received high-dose dofetilide 6 + 3 μg/kg and 6 placebo. During atrial pacing at a cycle length of 800 ms high-dose dofetilide prolonged right ventricular apex monophasic Action Potential Duration by 45 ms (16%) and the effective refractory period by 40 ms (16%). At the right ventricular outflow tract, monophasic Action Potential Duration was prolonged by 45 ms (15%) and effective refractory period by 55 ms (21%). During atrial pacing at a cycle length of 500 ms high-dose dofetilide prolonged the right ventricular apex monophasic Action Potential Duration by 40 ms (18%) and the effective refractory period by 43 ms (21%). The right ventricular outflow tract monophasic Action Potential Duration was prolonged by 33 ms (14%) and effective refractory period by 45 ms (21%). Dofetilide produced no increase in the dispersion of repolarization between the 2 sites. During the maintenance infusion QTc prolongation by highdose dofetilide averaged 43 ms (10%) with no increase of interlead QT dispersion. The effects of dofetilide on QT interval and effective refractory period are shown to be due to a direct effect on Action Potential Duration with no effect on dispersion. No rate dependence of monophasic Action Potential prolongation was detected at these cycle lengths.
Peng Sheng Chen - One of the best experts on this subject based on the ideXlab platform.
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Action Potential Duration restitution and ventricular fibrillation due to rapid focal excitation
American Journal of Physiology-heart and Circulatory Physiology, 2002Co-Authors: Moshe Swissa, Zhilin Qu, Toshihiko Ohara, Alan Garfinkel, Hrayr S Karagueuzian, James N Weiss, Peng Sheng ChenAbstract:The focal source hypothesis of ventricular fibrillation (VF) posits that rapid activation from a focal source, rather than Action Potential Duration (APD) restitution properties, is responsible for...
Olivier Bernus - One of the best experts on this subject based on the ideXlab platform.
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Electrotonic effects on Action Potential Duration in perfused rat hearts
2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009Co-Authors: Richard D. Walton, Olivier BernusAbstract:Electrotonic interActions in cardiac tissue have been shown previously to modulate dynamical properties of the myocardium such as Action Potential Duration (APD) and Action Potential Duration restitution. A recent computational study indicated that these electrotonic effects may be strongest in small murine hearts. In the present study, we investigate experimentally how APD is modulated by activation sequence and pacing rate using optical mapping in Langendorff perfused rat hearts. Our results show that following an epicardial point stimulus, a strong correlation exists between epicardial APD and activation time, with decreasing APD for increasing activation time. This effect is preserved for all pacing frequencies (6-14 Hz) investigated in this study. Our experimental results are validated by detailed three-dimensional computer simulations. These simulations also demonstrate a strong transmural APD dependence on activation sequence, which, near the pacing site, is sufficient to mask the intrinsic transmural gradient.
