Does a posterior aneurysm increase the risk of endocardial resection?

Claims of equivalence in medical research: are they supported by the evidence?

BACKGROUND

Most clinical studies are done to show comparative superiority, but many reports now claim equivalence between the investigated entities. These assertions may not always be supported by the methods used and the results obtained.

PURPOSE

To assess the justification and support for claims of clinical or therapeutic equivalence in medical journals.

DATA SOURCES

A search of MEDLINE for articles published from 1992 through 1996.

STUDY SELECTION

From 1209 citations that contained the word equivalence in the title or abstract or contained the Medical Subject Heading therapeutic equivalency, we excluded 1121 studies reporting nonoriginal research, purely laboratory or other nonhuman research, and studies in which equivalence was not the main claim. The remaining 88 eligible papers were evaluated for five methodologic attributes.

DATA SYNTHESIS

Only 45 (51%) of the 88 reports were specifically aimed at studying equivalence; the others either tried to show superiority or did not state a research aim. The quantitative distinctions regarded as "equivalent" ranged from 0% to 21% for direct increments and from 0% to 76% for proportionate differences. An equivalence boundary was set and confirmed with an appropriate statistical test in only 23% of reports. In 67% of reports, equivalence was declared after a failed test for comparative superiority, and in 10%, the claim of equivalence was not statistically evaluated. The sample size needed to confirm results had been calculated in advance for only 33% of reports. Sample size was 20 patients per group or fewer in 25% of reports.

CONCLUSIONS

Many studies of clinical equivalence do not set boundaries for equivalence. Claims of "difference" or "similarity" are often made not by thoughtful examination of the data but by tests of statistical significance that are often misapplied or accompanied by inadequate sample sizes. These methodologic flaws can lead to false claims, inconsistencies, and harm to patients.

Direct operation versus ICD therapy for ischemic ventricular tachycardia

Now that the implantable cardioverter defibrillator is available as a therapeutic option for the management of ventricular tachycardia (VT), some argue that there no longer should be a role for direct surgical intervention for this malignant arrhythmia. Rebuttal of this argument is difficult for the following reasons: (1) there are many patients who are candidates for implantable cardioverter defibrillator therapy but not for direct VT operation, and thus direct comparisons of the two therapies is difficult; (2) implantable cardioverter defibrillator therapy by definition is palliative, but a VT operation is curative in most instances; (3) in many electrophysiologic triage algorithms, implantation of a cardioverter defibrillator and VT operation are employed as alternative, not competitive, therapies, again making direct comparisons difficult; and (4) probably most importantly, there are misconceptions in the literature regarding the risks and benefits of direct VT surgical procedures as they are currently performed. In this brief review, we examine the currently available data on both sides of this argument.

The future of arrhythmia surgery

The future of arrhythmia surgery is discussed in light of the 25 years of historical developments that have led to the present explosion in antiarrhythmic therapies and technologies. The role of the arrhythmia surgeon in these developments is outlined, along with a number of exciting near-term and far-term developments that will continue to revolutionize therapeutic interventions for arrhythmia problems.