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 a	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability
central or left-sided chest pain (pre-test probability: 41%)	MI or unstable angina (ECG, cardiac enzymes, stress tests)	probable MI	13 (8.5 to 20)	73%
		ischaemia or strain not known to be old	1.6 (1.1 to 2.3)	25%
		ischaemia or strain or infarction but changes known to be old	0.34 (0.13 to 0.91)	7%
		abnormal but not diagnostic of ischaemia	0.21 (0.066 to 0.64)	4%
		non-specific ST or T wave changes	0.13 (0.049 to 0.34)	3%
		normal	0.042 (0.0059 to 0.30)	1%

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