The Rational Clinical Examination
David L. Simel, Drummond Rennie
Cardiac Tamponade
David L. Simel
Make the Diagnosis: Cardiac Tamponade
Topics Discussed:
beck triad, cardiac tamponade, criterion standard comparisons (diagnostic tests), diagnosis, differential, diagnostic process, likelihood ratio, make the diagnosis, pericardial effusion, prior probability, pulsus paradoxus, reference standards
Excerpt:
"Cardiac tamponade occurs when fluid trapped in the pericardial
space (ie, effusion) compresses the heart and compromises cardiac
output. Thus, an assessment of tamponade in the nonurgent setting
requires (1) knowing the pretest probability of an effusion and (2)
knowing the prior probability of tamponade among patients with effusion.
Most studies report only retrospective case series of patients with
effusion, so the prior probability of cardiac tamponade is not known.
However, because tamponade is so infrequent, among all patients
the probability is most likely less than 1%. Among case
series of patients with effusion, the prior probability cannot be
determined with certainty because of patient selection bias. In
a study of patients with effusion who were clinically suspected
of having hemodynamic compromise, 64% had tamponade.1 Since
many patients with pericardial effusions have small inconsequential
amounts of fluid, the likelihood of tamponade in all patients with
effusion should be much lower than 64%...."
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