Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (30 page)

   It is prudent to have a low threshold for the diagnosis of ACS, which is made from the clinical characteristics of the presenting symptoms, ECG findings and the presence of myonecrosis as reflected by an elevation of cardiac biomarkers. These diagnostic tools also provide risk assessment, which may dictate therapy, management strategy and placement.

   NSTEMI patients have an intermediate risk of acute complications when compared to unstable angina (lower) and STEMI patients (higher), approaching a 5% 30-day mortality rate.

   Etiology

   Cardiac sources of chest pain:

1.   
Ischemic/coronary heart disease
—acute coronary syndromes (STEMI, NSTEMI, UA), stable angina pectoris

2.   Ischemic/nonatherosclerotic—aortic stenosis, hypertrophic cardiomyopathy, severe systemic hypertension, right ventricular hypertension, aortic regurgitation, severe anemia, coronary vasospasm, anatomical abnormalities

3.   
Inflammatory
—pericarditis, infectious and autoimmune vasculitis

4.   
Hyperadrenergic states
—stress CM, severe hypertension, pheochromocytoma

5.   
Chest pain syndromes
—mitral valve prolapse, psychosomatic

   Noncardiac sources: GI (GERD, esophageal rupture, esophagitis, esophageal motility/achalasia, referred pain—biliary colic, appendicitis), pulmonary (pneumonia, pulmonary embolism, pulmonary hypertension, sarcoidosis, effusion, pneumothorax, pleuritis, serositis), aortic syndromes, musculoskeletal, psychosomatic

   Who Should Be Suspected of ACS?

   Consideration of the pretest probability of coexisting coronary artery disease should influence the diagnosis of ACS.

   ACS should be considered a working diagnosis subject to reevaluation.

   Unstable angina (UA) and NSTEMI are closely related clinical conditions with similar pathophysiology but differing severity. NSTEMI is usually characterized by ischemic chest discomfort at rest, absence of ST-segment elevation on a 12-lead ECG, and positive necrosis biomarkers.

   As an elevation of cardiac biomarkers may not be detectable for 12 hours, UA and NSTEMI may be initially indistinguishable. However, the distinction is important to make for early acute management. Increasing evidence supports early aggressive anticoagulation and mechanical revascularization as superior to conservative medical therapy for NSTEMI patients.

   Unstable angina presents as three scenarios: ischemic discomfort at rest (approximately 20 minutes’ duration), new-onset discomfort at mild exercise threshold in the last 6 weeks, or progression of previously stable angina to easily evoked with ordinary physical activity or increased in severity (Canadian Cardiovascular Society Class III).