Investigations

• ECG  ^b looking for:
  • anterior Q waves ^b
  • left-bundle branch block ^b

• Anterior q waves and left bundle-branch block are very helpful at diagnosing an ejection fraction < 40% ^b

A normal ECG makes left ventricular systolic dysfunction less likely

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected heart failure b (pre-test probability: 18%)	impaired left ventricular systolic dysfunction (echocardiography)	abnormal ECG	2.4 (2.1 to 2.8)	35%	0.10 (0.047 to 0.22)	2%