Investigations

• pain worse than prior angina or the same as the pain associated with a prior MI
• systolic blood pressure <110 mmHg
• crackles above the bases bilaterally
• ST elevation or Q waves, not known to be old, in two or more leads
• ST segment or T wave changes, not known to be old, indicative of myocardial ischaemia

Why?

A clinical prediction rule can help identify patients at risk of having major complications

Group a	risk of major complication at 4 days	%  (95% CI)	NNF  (95% CI)
suspected MI on ECG or suspected ischaemia on ECG and 2 or more risk factors	high	16%  (12% to 20%)	6  (5 to 8)
suspected ischaemia on ECG and 1 or less risk factor	moderate	7.8% (6.0% to 9.6%)	13  (11 to 17)
one risk factor with no MI or ischaemia	low	3.9%  (2.7% to 5.2%)	26  (19 to 37)
no risk factors	very low	0.58%  (0.29% to 0.87%)	170  (110 to 340)