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Ischemic Heart Disease 159

extension, or tachyarrhythmias early after the onset of
infarction. If adverse effects of beta-blockers develop
or if patients present with complications of infarction
that are contraindications to beta-blockade, such as
heart failure or heart block, the beta-blocker should
be withheld. Unless there are contraindications, beta-
blockade probably should be continued in patients who
develop STEMI. Moreover, patients who initially have
contraindications to a beta-blocker, such as heart failure,
should be reevaluated with respect to their candidacy for
such therapy after 24 hours (Reference: Braunwald’s Heart
Disease, 9th edn. Elsevier chapter 55). In those with mild
to-moderate heart failure, beta-blockers may be initiated
at a lower dose (i.e. Carvedilol 3.125 mg twice daily or
metoprolol 12.5 mg twice daily) along with a diuretic and
ACE inhibitor. Gradually the dose of the beta-blocker
may be increased to attain the target dose (i.e. Carvedilol
25 mg twice daily or metoprolol 100 mg twice daily).
11. What do you know about the cardiac biomarkers?
Myocardial infarction is defined as detection of a rise
and/or fall of cardiac biomarker values with at least one
of the following:
• Symptoms of ischemia.
• New or presumed new significant ST segment–T wave
(ST–T) changes or new left bundle branch block (LBBB).
• Development of pathological Q waves in the ECG.
• Imaging evidence of new loss of viable myocardium
or new regional wall motion abnormality.
• Identification of an intracoronary thrombus by
angiography or autopsy.
Cardiac biomarkers thus play an important role in the
diagnosis of acute myocardial infarction. The important
cardiac biomarkers are the following (Table 4):