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Specific guide to this web site for:

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      in Statistics

 2.  Medical Students

 3.  Science media writers

 4.  High School & College
     Statistic Teachers


1. Harvard led MI study

2. JACC study 

   (J. of Amer. Coll.

3. NEJM cath study

4. Amer. J. of Cardio.
    review of literature


Oat bran study

Pregnancy & Alcohol

Are Geminis really
9. Columbia 'Miracle' Study  

Additional Topics:


Limitations of Meta-Analyses

Large Randomized Clinical Trials

Tale of Two Large

Advocate meta-analyses

Network meta-analyses




Letter. Outpatient versus inpatient catheterization. Roehm E. NEJM 1989; 320:938

  To the Editor:  The article by Dr. Block et al1 regarding outpatient versus inpatient cardiac catheterization showed a high frequency of myocardial infarctions developing in the outpatient group. The outpatient group developed a myocardial infarction in 1.6% of the patients (3/192) versus 0.5% (1/189) in the inpatient group. There was no statistical significance in this threefold difference in myocardial infarction rate, though as the authors have suggested, this may be the result of a type II statistical error.

The frequency of myocardial infarction occurring as a possible complication of cardiac catheterization is quite low in modern day studies. The CASS study which included patients with unstable angina in contrast to Dr. Block's study, had a 0.45% combined incidence of myocardial infarction and fatal events within 48 hours of the procedure.2 Unstable angina in the CASS study was the only variable statis­tically associated with the occurrence of nonfatal infarction, and was present in the majority of the fatalities as well. Other large modern day studies have reported myocardial infarction as a complication in 0.09%3 and 0.07%4 of patient's undergoing cardiac catheterization. The incidence of myocardial infarction is considerably higher in the outpatient group in Dr. Block's study.

Detailed, additional information on the 4 patients in Dr. Block's study who developed a myocardial infarction would be useful. How many hours after the cardiac catheterization did the onset of each myocardial infarction occur?  Were there factors in the individual cases that suggested the development of the myocardial infarction was related to the outpatient protocol? What type of coronary disease and functional class existed in each of the patients who experienced a myocardial infarction?

Analysis of this type may help indicate whether this particular outpatient protocol played a role in the development of the myocardial infarctions which occurred. For example, if early mobilization led to a large hematoma associated with hypotension followed by a myocardial infarction, this would be suggestive evidence that the infarction was related to the outpatient catheterization procedure. Alternatively, if the myocardial infarction occurred prior to mobilization, it would indicate the patient's outpatient status was unrelated to the outcome.

A modern day study of a cardiac catheterization protocol, particularly in clinically stable patients, in which one arm of the protocol experiences one myocardial infarction every 64 patients warrants a close examination before that approach can reasonably be considered both "feasible and safe". Would the authors examine their patient data and furnish additional information to allow for further evaluation of this aspect of their study?     (The New England Journal of Medicine Editors deleted this last paragraph of the letter after accepting it for publication.) 

1. Block P, Ockene I, Goldberg R, et al. A Prospective Randomized Trial of Outpatient versus Inpatient Cardiac Catheterization. N Engl J Med 1988: 219: 1251-55.

2. Davis K, Kennedy J, Kemp J, et al. Complications of Coronary Arteriography from the Collaborative Study of Coronary Artery Surgery (CASS). Circulation 1979: 59: 1105-12.    

Eric Roehm, M.D.