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THIS WEEK'S TEACHING TOPICS
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prevalence of obstructive coronary disease among Quote of the Week
“Regardless of which topical insecticide is used, management of head lice should include the use of a lotion that delivers a high insecticide concentration in one application, with a sufficient quantity of the lotion applied to ensure thorough coverage, a second application no fewer than 7 and no more than 11 days after the first in order to kill lice that may have hatched from eggs surviving the first treatment, and concomitant treatment of all infested family members.” EDITOR'S NOTE: Should This Internist Recertify? This week we
publish a nat presents a fictitious vignette involving
a 55-year-old physician who has never considered enrolling in the maintenance of certification (MOC) program and has received a communication from the ABIM urging him to undergo the MOC process. n whether the internist should enroll in the MOC program as currently configured andupport your recommendation by March 24.
TEACHING TOPIC
1. Commotio Cordis
REVIEW ARTICLEB.J. Maron and N.A.M. Estes
Ventricular fibrillation and sudden death triggered by a blunt, nonpenetrating, and often innocent-appearing unintentional blow to the chest without damage to the ribs, sternum, or heart (and in the absence of underlying cardiovascular disease) constitute an event known as commotio cordis.
Clinical Pearls
When does commotio cordis occur?
About 55% of occurrences of commotio cordis have been reported in young competitive athletes (mostly those between 11 and 20 years of age) participating in a variety of organized amateur sports — typically baseball, softball, ice hockey, football, or lacrosse — who receive a blow to the chest that is usually (but not always) delivered by a projectile that is used to play the game.
How should suspected commotio cordis be treated?
A public health strategy that incorporates a plan for making automated external defibrillators (AEDs) widely available is likely to result in the survival of more young people in the event of commotio cordis. Indeed, AEDs have also effectively terminated ventricular fibrillation in animal models of commotio cordis. However, even under optimal conditions, an AED can fail to restore the heart to normal rhythm after commotio cordis. Both clinical studies and experimental studies suggest that precordial thumps are unreliable in terminating ventricular fibrillation caused by chest blows.
Morning Report Questions
Q What location of a blow can precipitate commotio cordis?
:
A To precipitate commotio cordis, the blow must be directly over the heart,
particularly at or near the center of the cardiac silhouette. Precordial bruises : representing the imprint of a blow are frequently evident in victims. There is no evidence in humans or in experimental models that blows sustained outside the precordium (e.g., the back, the flank, or the right side of the chest) cause sudden death.
Q At what part of the cardiac electrophysiological cycle must the blow
occur?
:
A The blow must occur within a narrow window of 10 to 20 msec on the upstroke
of the T wave, just before its peak (accounting for only 1% of the cardiac cycle) : — that is, the blow must occur during an electrically vulnerable period, when inhomogeneous dispersion of repolarization is greatest, creating a susceptible myocardial substrate for provoked ventricular fibrillation.
f Circumstances in Which Chest Blows Have Triggered TEACHING TOPIC
2. Elective Cardiac Catheterization
ORIGINAL ARTICLE.R. Patel
In this national registry of data on cardiac catheterization, only 38% of elective, diagnostic coronary angiograms showed obstructive lesions, and 39% of angiograms were interpreted as showing no disease. The findings indicate a relatively low diagnostic yield of elective coronary angiography, a procedure that exposes patients to Clinical Pearls
What is the prevalence of obstructive coronary disease among patients with
typical angina?
Of the 397,954 patients without known coronary artery disease who had elective cardiac catheterization, obstructive coronary artery disease was identified in 38%, of whom 53.3% had evidence of multivessel disease. Patients with symptoms of stable angina were more likely to have obstructive coronary artery disease than were patients without symptoms (43.9% vs. 31.5%, P<0.001).
What were the independent risk factors that predicted the presence of
obstructive coronary disease?
According to the results of this study, male sex, white race, older age, lower body-mass index, use of tobacco, and presence of diabetes, dyslipidemia, peripheral vascular disease, cerebrovascular disease, dialysis-dependent renal failure, or hypertension were each independent predictors of obstructive coronary artery disease.
Morning Report Questions
Q Did positive results on noninvasive testing substantially improve the
prediction of obstructive coronary disease beyond traditional risk
: factors?
A Although the association was significant, the effect of a positive noninvasive
test on the ability of the model to predict the presence of obstructive coronary : artery disease was limited, increasing the C-index from 0.7609 to 0.7639.
Q Did the presence of symptoms substantially improve the prediction of
obstructive coronary disease beyond traditional risk factors?
:
A When symptoms were added to the predictive model, they were independently
related to the presence of obstructive coronary artery disease and also slightly : improved the predictive ability of the model for obstructive coronary artery disease (from a C-index of 0.7417 to a C-index of 0.7609).

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