However, the disposition of patients with suspected acute coronary syn-
drome should be based on the clinical examination and not the cardiac
enzymes. Initial determination of these markers has a low sensitivity for
detecting ischemia and cannot be used to reliably diagnose or exclude the
presence of an ACS.
The ECG is the most important diagnostic test for assessing patients
with suspected ACS. However, the initial ECG is diagnostic in only 25% to
50% of patients presenting with an acute MI. Therefore, a normal ECG (a)
at presentation is not sufficient to rule out an acute MI. Detection of cardiac
markers requires that sufficient myocardial cell damage has occurred and
that enough time has passed for these markers to be released into the
serum and subsequently detected. One set of cardiac enzymes (b)is typi-
cally insufficient to exclude the diagnosis of acute MI. It is well known that
relief of symptoms after the administration of antacids or nitroglycerin (d)
does not rule out ACS. Epigastric discomfort, indigestion, or nausea and
vomiting(e)may be the only complaint in patients, particularly women,
elderly, and diabetics with ACS. In addition, patients with an inferior wall
MI often present this way.
31.The answer is b.(Rosen, pp 1042-1044.)Aspirinis an antiplatelet
agent that should be administered early to all patients suspected of having
an ACS, unless there is a contraindication. The ISIS-2 trial provides the
strongest evidence that aspirin independently reduces the mortalityof
patients with acute MI.
(a)Nitroglycerin provides benefit to patients with ACS by reducing
preload and dilating coronary arteries. However, there is no mortality ben-
efit with its use. (c)Unfractionated heparin acts indirectly to inhibit throm-
bin, preventing the conversion of fibrinogen to fibrin. Thus, inhibiting clot
propagation. Heparin has not shown to have a mortality benefit. (d)Routine
use of lidocaine as prophylaxis for ventricular arrhythmias in patients who
have experienced an acute MI has been shown to increase mortality rates.
(e)Use of CCBs in the acute setting has come into question, with some tri-
als showing increased adverse effects.
32.The answer is c.(Rosen, pp 1138-1139.)The patient has myocarditis.
Theenteroviruses,especially the coxsackievirus B,predominate as causative
agents in the United States. Coxsackie B virus usually causes infection during
the summer months. Some other causes of myocarditis include adenovirus,
influenza, HIV, Mycoplasma, Trypanosoma cruzi,and steroid abuse. Flu-like
40 Emergency Medicine