The role of the 12-lead ECG as a screening test for cardiac source of embolus.

BACKGROUND

Investigation for cardiac source of embolus (CSE) is one of the commonest referrals for transthoracic echocardiography (TTE) of hospital inpatients, but has a relatively low-diagnostic yield. We sort to investigate whether 12-lead ECG might be useful in screening patients to obviate the need for TTE, in a subset of patients referred for echocardiographic investigation of cardiac source of embolus.

METHODS

We collected ECG and echo data for 400 consecutively referred inpatients for TTE investigation of possible cardiac source of embolus. We analysed this data for evidence of cardiac source of embolism on TTE in patients with a normal or abnormal ECG.

RESULTS

41/400 (10%) subjects had possible CSE identified on TTE. Diagnostic yield for CSE was higher for those with abnormal compared with normal ECG (17% versus 6%, p<0.001). Of 232/400 (58%) patients with a normal ECG, 200 had a normal TTE (86%). Of the 32 with normal ECG and abnormal TTE, echo found a possible embolic source in 13. Of those 168 (42%) with an abnormal ECG, TTE was normal in 73 and abnormal in 95, of whom 28 patients had an echo that identified a possible cardio-embolic source. ECG, therefore, had a sensitivity of 68%, specificity of 61%, positive predictive value of 0.17 and negative predictive value of 0.94 for detecting possible cardiac sources of embolus.

CONCLUSIONS

Although TTE is a relatively low-yield investigation for the detection of cardiac source of embolus, 12-lead ECG is not sufficiently sensitive to identify the approximately 10% of patients in whom echo will demonstrate a diagnostic abnormality.