REPLY
Amiodarone and Ventricular Arrhythmia Suppression
Soo G. Kim;
James A. Roth; and
John D. Fisher
15 February 1993 | Volume 118 Issue 4 | Page 316
IN RESPONSE:
Dr. Cook made an assumption that we used ANOVA to compare average ventricular premature complexes per hour on each study day [1]. In the Statistical Methods section, we stated that ANOVA, the Kruskal-Wallis test, or the Fisher exact test was used to compare appropriate variables. Because ventricular premature complexes in our study patients were not normally distributed, the appropriate measure was the Kruskal-Wallis test. Dr. Cook assumed that we used ANOVA in this situation, and calls our conclusion "erroneous." It was not considered necessary to note that the Kruskal-Wallis result was compared with the chi-square distribution with 7 degrees of freedom.
The ANOVA was used to compare data shown in Table 1 of our report. The F statistic for the analysis of variance (QTc interval) was 9.05 on 7 and 371 degrees of freedom. Because the P value was reported, we did not report the F statistic. The Fisher least significant difference comparison was used to adjust for multiple comparisons.
The well-known variability [2] in frequency of ventricular premature complexes is greater in patients with less frequent ventricular premature complexes (for example < 30/h) or when measurements are made after a long period of time. The degree of variability of arrhythmia seen in our study of patients with sustained ventricular tachycardia or cardiac arrest and frequent ventricular premature complexes (
30/h), has not been well studied. The study by Pratt and coworkers [3], involving survivors of acute myocardial infarction without a history of malignant ventricular arrhythmias and 10 or more ventricular premature complexes per hour is not comparable to ours. Our study criteria are similar to those of the ESVEM study [4] and other studies [5], where they also were as useful in predicting drug effects and long-term outcomes of patients with malignant ventricular arrhythmia. In addition, the day-to-day variability in individual patients may have little significance when 50 patients are compared for each day. In sum, we stand by our conclusions.
1. Kim SG, Mannino MM, Chou R, Roth S, Roth JA, Desai B, et al. Rapid suppression of spontaneous ventricular arrhythmias during oral amiodarone loading. Ann Intern Med. 1992; 117:197-201.
2. Kim SG. The management of patients with life-threatening ventricular tachyarrhythmias: programmed stimulation or Holter monitoring (either or both)? Circulation. 1987; 76:1-5.
3. Pratt CM, Hallstrom A, Theroux P, Romhilt D, Coromilas J, Myles J. Avoiding interpretive pitfalls when assessing arrhythmia suppression after myocardial infarction: insights from the long-term observations of the placebo-treated patients in the Cardiac Arrhythmia Pilot Study (CAPS). J Am Coll Cardiol. 1992; 17:1-8.
4. Mason JW, the ESVEM Investigators. Unsustained ventricular tachycardia as a predictor of spontaneous sustained ventricular tachycardia in the ESVEM study (Abstract). Circulation. 1991; 84:II-348.
5. Kim SG. Values and limitations of programmed stimulation and ambulatory monitoring in the management of ventricular tachycardia. Am J Cardiol. 1988; 62:7I-12I.
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