How do physicians determine when to perform an "on-drug" electrophysiology study for efficacy determination in patients with sustained ventricular tachyarrhythmias: a previously unaddressed variable that may affect efficacy rates.
In patients with ventricular tachyarrhythmias, efficacy rates of antiarrhythmic agents, as judged by serial electrophysiological (EP) tests, have been variable. Factors underlying this variability have been reported to include: specific drug, type of arrhythmia, type of heart disease, left ventricular function, and number of prior drug failures. We hypothesized that variability in physician practice behavior as to when a drug assessment is performed might be another important factor affecting drug efficacy. Using a survey sent to 103 electrophysiology centers we determined from the 46 respondents that this is indeed the case. Twenty-six of the 46 respondents always, 9 of 46 sometimes, and 11 of 46 did not require ectopy reduction on continuous electrocardiographic monitoring before proceeding to an EP study. The ectopy reduction required, however, varies among physicians in percentage and type. Twenty-seven of the 35 respondents who utilize rhythm monitoring also require attainment of an acceptable blood level, a prespecified minimal target dose, and/or one or more ECG interval changes prior to proceeding to EP testing. Fifteen out of 46 do not require "therapeutic" drug levels. Of 11 who don't use rhythm monitoring, 5 also don't use blood levels. The lower value for "therapeutic ranges" varied by up to 3-fold and the upper value by up to 2 1/2-fold for individual drugs. The minimum time for testing varied from 1 half-life to over 10 half-lives. Similarly, the response to failure of a submaximal dose also varied: 9% always retested at a high dose, 2% never tested at a higher dose, and 91% were inconsistent. Moreover, what was considered the maximal dose for an individual drug varied by 3- to 6-fold for most agents queried. We believe these variations in dose, time, and coassessment factors must have an influence on efficacy rates of antiarrhythmic agents.
Reiffel
J A
JA
Department of Medicine, Columbia University, College of Physicians and Surgeons, New York, New York, USA.
Banker
J
J
D000889:Anti-Arrhythmia Agents / Q000097:blood / Q000627:therapeutic use*; D002304:Cardiac Pacing, Artificial; D015716:Electrocardiography, Ambulatory; D006801:Humans; D010818:Practice Patterns, Physicians'; D011795:Surveys and Questionnaires; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000188:drug therapy*
D000889:Anti-Arrhythmia Agents