0071643192.pdf

■ Troponin I
■ Most sensitive and specific but delayed rise
■ Rises in 3–6 hours
■ Peaks at 12–24 hours
■ Normalizes in 7–10 days
■ Unlike troponin T, is notelevated in skeletal muscle disease or renal failure

Cardiac Testing

■ Cardiac catheterizationis definitive.
■ Echocardiogram can identify regional wall motion abnormalities, but
cannot differentiate ischemia from acute or chronic infarction and cannot
reliablydetect subendocardial ischemia.
■ Perfusion imagingduring symptoms
■ IV radionuclide (eg, thallium 201, technetium 99m-sestamibi) is taken
up by myocardium.
■ Uptake is proportional to blood flow, so areas with poor perfusion are
demonstrated.
■ Stress testing is contraindicatedin the presence of MI or unstable angina.
■ Electron beam CT (EBCT)is a new technology that shows calcium
plaques in arteries and may be a good screening tool for presence of CAD.

RISKSTRATIFICATION

See Table 2.4.

CARDIOVASCULAR

EMERGENCIES

Echocardiogram cannot

reliably detect subendocardial

ischemia.

TABLE 2.4. Risk Stratification

INTERMEDIATE

HIGHLIKELIHOOD LIKELIHOOD LOWLIKELIHOOD

History Chest or left arm Chest or left arm Probable ischemic

pain or discomfort pain or discomfort symptoms without any

typical of prior angina Age > 70 high or intermediate

Known history of CAD Male likelihood features

or MI Diabetes Recent cocaine use

Examination Transient mitral Extracardiac vascular Chest discomfort

regurgitation disease reproduced by palpation

Decreased BP

Diaphoresis

Rales/pulmonary edema

ECG New ST-segment Stable chronic changes Normal or T-wave

deviation (≥0.05 mV) (Q waves, abnormal flattening or inversion in

or T-wave inversion ST segments or leads with dominant

(≥0.2 mV) while T waves) R waves

having symptoms

Cardiac Elevated Normal Normal

Markers