Professor John Hampton, emeritus professor of cardiology, University of Nottingham
The ECG at our surgery provides an interpretation of any ECG undertaken. A quite common finding is ‘left anterior fascicular hemiblock'. If there are no cardiac symptoms and the ECG has been taken for another reason, such as assessment of end-organ damage in hypertension, how should the ECG be managed?
A word of warning about automatic ECG interpretation. Automatic reports are design-ed as much to protect the manufacturers as to help the patient – they tend to over-report to ensure that nothing is missed. As a result a lot of ECG changes that are actually normal variants get interpreted as abnormal. It is unwise to depend totally on an automatic report, and I hope you know enough about ECGs to interpret the reports with caution.
Left anterior hemiblock means left axis deviation (ie, a dominant S wave in both leads two and three – and I have come across automatic reports that describe left axis when there is a dominant S in lead three
only) often with a slightly widened QRS complex, although the QRS is still less than 120msec.
Left anterior hemiblock is caused by failure of conduction in the anterior fascicle of the left bundle branch. The left bundle branch has two divisions, the anterior and posterior fascicles, and conduction failure in one of these can be thought of as ‘half' of left bundle branch block. In other words, it is a manifestation of fibrosis in the conduction system and so of some sort of cardiac disease.
Of itself, left anterior hemiblock causes no problems, and seldom progresses to higher (and therefore clinically important) degrees of block.But here I must be pedantic and say you should never treat an ECG – you treat the patient, and the ECG is just a tool in diagnosis. If your patient with hypertension has an ECG showing left anterior hemiblock then there is target organ damage, even though it may not be very important.