Characteristics and Duration of Chest Pain:

• Brief episodes of pain (<5 minutes) are less likely to be cardiac in origin and could suggest conditions like costochondritis or esophageal spasm.
• Pain lasting longer than 20 minutes is more suggestive of cardiac etiology.

Differential Diagnosis and Clues:

• GERD can cause burning chest pain that can be very difficult to distinguish from cardiac chest pain. Trial of a proton pump inhibitor or response to antacids may provide clues.
• Elderly patients, women, and those with diabetes may not present with classic symptoms of cardiac chest pain and may instead have fatigue, shortness of breath, or other non-specific symptoms.

Diagnostic Tools and Interpretation:

• History alone cannot reliably rule in or rule out ACS.
• Troponin is highly sensitive but not specific for ACS and needs to be trended out as it may commonly lag the onset of chest pain symptoms.
• In ACS, creatine kinase (CK) will remain high for 3-4 days and troponin will stay high for 7-10 days; thus CK is the more reliable test for recurrent ischemia.
• The most useful scores for evaluation of chest pain in the ED are the TIMI and HEART scores.
• If you are concerned that a patient is having active ischemia, keep the EKG attached and get a new reading every 5-10 minutes - you may be able to catch dynamic changes.

Medications and Treatment:

• Ranolazine is an anti-anginal agent that doesn't affect heart rate or blood pressure and can thus be useful in patients who can't tolerate other anti-anginals; mechanism involves shifting myocardial cell metabolism from fatty acids to glucose, which requires less oxygen
• Nitroglycerin provides rapid relief for angina by causing venous and arterial dilation, reducing myocardial oxygen demand - they should be avoided in inferior MI involving RV because the RV is preload-dependent, meaning it relies on adequate venous return for optimal function and vasodilation can reduce preload and lead to a dangerous drop in BP
• Calcium channel blockers like verapamil, diltiazem, or nifedipine are first-line for coronary artery spasm (Prinzmetal Angina) - they act primary via dilation

Stress Tests:

• Exercise EKG Stress Test (Treadmill Test) - exercise on a treadmill or bicycle to increase HR and BP while monitoring EKG to look for evidence of ischemia; refer if patients can exercise and have baseline EKG
• Stress Echocardiography - echo is taken at rest and immediately after exercise; best for patients with known CAD, baseline EKG not normal
• Nuclear Stress Test (Perfusion Imaging) - radioactive dye injected and images taken before and after exercise or chemical stress (below); patients with a high risk of CAD, prior inconclusive stress tests, those who can’t exercise
• Pharmacologic Stress Test - adenosine or dobutamine (most commonly) given to simulate exercise of the heart, and then an echo or nuclear scan is performed; ideal for patients who can’t exercise or with baseline EKG abnormalities
• Contraindications to cardiac stress testing: Absolute - acute MI or UA, arrhythmia, PE, severe AS, myocarditis/pericarditis, dissection; Relative - known left main disease, SBP >200, moderate valvular stenosis, hypertrophic cardiomyopathy, 2nd (Type 2) or 3rd degree AV block
• Exercise stress testing (e.g., treadmill or bicycle) is preferred over pharmacologic stress because it provides information on exercise tolerance and can reveal exercise-induced arrhythmias.
• Achieving at least 85% of the maximum predicted heart rate (220 minus age) is generally required for an exercise stress test to be considered diagnostic
• During a stress test, symptoms like dyspnea, dizziness, or chest pain, as well as a drop in blood pressure, can be as significant as ECG changes
• Stress tests can have false positives, especially in low-risk populations or in women with a low pre-test probability of coronary artery disease.
• In general, beta-blockers, calcium channel blockers, and nitrates can affect the results of stress tests and are generally held before a test
• Caffeine should be avoided in pharmacologic stress tests using adenosine or dipyridamole, as it blocks adenosine receptors
• In general, dobutamine should be avoided in patients with severe asthma, as it can provoke bronchospasm

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