Diagnosis	History	Physical examination	Chest radiography	Electrocardiography
Myocardial infarction	Substernal pain that radiates, dyspnea, shortness of breath	Diaphoresis, hypotension, third heart sound (S3)	Usually normal	ST-T elevations (especially if new), new Q wave, new conduction defect
	Pleuritic pain decreases likelihood ratio
Pericarditis	Positional pain: increases while supine and decreases when upright	Pericardial friction rub	Increased heart size with pericardial effusion greater than 250 mL	Diffuse concave upward ST-segments, PR- segment depression
				Abnormality noted in more than 90 percent of cases
Pneumonia	Anorexia, cough, dyspnea, fatigue, myalgia	Crackles, egophony, fremitus	Infiltrate	Typically not indicated
Pneumothorax	Sudden pain and dyspnea	Tachycardia, hyperresonance, decreased breath sounds, decreased wall movement	Thin pleural line	Typically not indicated
			May be normal in small pneumothorax	Sinus tachycardia
Pulmonary embolism	Prior embolism or clot	Tachycardia, tachypnea	Abrupt hilar cutoff, oligemia, or pulmonary consolidations compatible with infarction	Sinus tachycardia, right ventricular overload (T-wave inversion in right precordial leads, S1Q3/S1Q3T3, transient right bundle branch block, pseudoinfarction, S1S2S3)
	Cancer, immobilization, estrogen use, or recent surgery
	Dyspnea, syncope