Investigations

• a 12-lead ECG ^{a b} - read it carefully! ^a

Why?

ECG features suggestive of a myocardial infarction make a MI or unstable angina more likely

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability
central or left-sided chest pain a (pre-test probability: 41%)	myocardial infarction (ECG, cardiac enzymes, stress tests)	probable MI	8.7 (4.8 to 16)	86%
		ischaemia or strain not known to be old	3.1 (2.1 to 4.4)	68%
		ischaemia or strain or infarction but changes known to be old	1.7 (1.1 to 2.8)	55%
		abnormal but not diagnostic of ischaemia	0.47 (0.28 to 0.78)	25%
		non-specific ST or T wave changes	0.48 (0.35 to 0.67)	25%
		normal	0.078 (0.035 to 0.18)	5%

• Emergency physicians can misread ECGs for patients with cardiac chest pain - missing 12% of ST elevation and 12% of T wave inversion. ^a