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Effect of a Class III Antiarrhythmic Drug on the Configuration of Dose Response Curve for Defibrillation
Author(s) -
MURAKAWA YUJI,
YAMASHITA TAKESHI,
KANESE YUKIHIRO,
OMATA MASAO
Publication year - 1999
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.1540-8159.1999.tb00476.x
Subject(s) - medicine , defibrillation , defibrillation threshold , ventricular fibrillation , shock (circulatory) , bolus (digestion) , cardiology , area under the curve , fibrillation , anesthesia , atrial fibrillation
Antiarrhythmic agents with a Class III action are known to increase defibrillation efficacy. We investigated whether a Class III drug simply shifts the dose‐response curve for defibrillation or more extensively alters the curve. Forty‐five dogs were divided into four groups according to the shock waveform and the presence or absence of treatment with a novel Class III drug, MS‐551 (2 mg/kg bolus + 0.02 mg/kg per min). In addition to the conventional transcardiac DFT, dose‐response curves were obtained by fitting the results of 40 fibrillation‐defibrillation sequences at five shock strengths to a logistic model. MS‐551 significantly decreased DFT regardless of the shock waveform (control vs MS‐551 = 306 ± 79 V vs 229 ± 72 V [monophasic shock, P < 0.05], or 227 ± 42 V vs 176 ± 26 V [biphasic shock, P < 0.005]). The dose‐response curves in dogs treated with MS‐551 had a gentler slope than those without treatment, and the ratio of the voltages corresponding to 50% and 90% defibrillation success (V90/V50) was significantly greater in the MS‐551 group (monophasic: 1.21 ± 0.06 vs 1.62 ± 0.42 [P < 0.005], biphasic: 1.20 ± 0.05 vs 1.37 ± 0.18 [P < 0.01]). The V90/DFT ratio was also significantly larger in the MS‐551 group (monophasic: 1.22 ± 0.12 vs 1.66 ± 0.37 (P < 0.001); biphasic: 1.19 ± 0.11 vs 1.44 ± 0.79 [P < 0.005]). Thus, this Class III drug decreased the shock strength corresponding to relatively higher success rate (˜90%) less markedly than that for moderate success rate (˜50%). These results suggest that a Class III drug does not simply shift the dose response curve in proportion to the change in DFT, but more extensively alters its configuration.