Cardiac Causes

The various types of cardiac causes are listed below.

Normal variant/benign early repolarisation

In 1960, Hiss [8] studied the ECGs of 6014 healthy men in the US Air force. They found that 91% had ST segment elevation of 1mm to 3mm in one or more precordial leads. This demonstrates the common nature of BER, the incidence of this finding decreases with age.

Women demonstrate ST elevation of >1mm in only 20% of cases and this does not appear to change with increasing age [3].

It is equally common in all races [11]. ST segment elevation due to BER reduces in amplitude during exercise – however, exercising people with ST elevation in order to confirm BER may be hazardous.

Learning bite

BER is common especially at younger ages.

Left bundle branch block

The appearance of LBBB on an ECG makes any further interpretation of the ECG difficult. There are various features that allow you to ‘read through’ LBBB to identify an acute STEMI: Sgarbossa [15] described three independent ECG signs suggestive of AMI in a patient with LBBB on their ECG, as shown in Table 1 below.

Table 1: Modified Sgarbossa Criteria

These are highly specific but not sensitive for AMI and so have limited use in everyday clinical practice.

Much more importance is attached to a good history for AMI.

Learning bite

A patient presenting with a good history of AMI and with LBBB on their ECG should be treated as an AMI even in the absence of the Sgarbossa criteria.