of the study:
study concerned cardiac patients undergoing outpatient cardiac catheterization1.
In this study there were 192 outpatients, and 189 inpatients.
There were three heart attacks in the outpatient group, and one heart attack in
the inpatient group. The authors
conclude that heart catheterization is safe to perform as an outpatient.
Elective heart catheterization in stable patients is usually associated with a major complication (stroke, MI. or death) in only 1 out of 1000 patients2. This study reported that 3 patients out of 192 patients (approximately 1 out of 64) of outpatients experienced an MI with elective outpatient cardiac catheterization and that 1 patient out of 189 patients with inpatient cardiac catheterization had an MI.
Implausibly, the authors concluded that these patient results demonstrated that outpatient heart catheterization is safe. Outpatient catheterization actually is safe, but the data in this study suggests the opposite. (The authors did note that because of the small sample size they could not exclude a small increase in complication rates. Nevertheless, their data did not suggest outpatient catheterization was safe. As it turned out, the seemingly high complication rate with outpatient catheterization in this study was a result of the authors miscounting data points as well as not following their own trial protocol.)
In contrast, if
a heart catheterization laboratory was actually found to have 1
out of 65 patients of the last 190 stable patients undergoing low risk
catheterization develop a heart attack, that program would need to intensely
investigate if a significant procedural problem exists.
The authors subsequently reveal in a follow-up letter3 they had mistakenly counted patients having a heart attack twice rather than once. This occurred even though having a heart attack as a complication of the procedure was the most important primary trial data endpoint and they only counted a total of 4 heart attacks. Furthermore, contrary to their descriptions of the patients as being low risk outpatient cardiac catheterization, they accidentally included at least one patient in the outpatient group that had a much higher risk procedure, elective balloon angioplasty who went on to have a heart attack. This was a clear and unacceptable violation of their description of the patients being studied in their trial.
Hence, in this one study the authors not only misinterpreted their data and ignored adverse trends, they miscounted their data endpoints and unintentionally broke trial protocol as well.
Block P, Ockene I, Goldberg R, et al. A Prospective Randomized Trial of
Outpatient versus Inpatient Cardiac Catheterization; N Engl J Med 1988: 219: