Is incidental Left Bundle Branch Block Benign?

Here’s the case. You see a 24 year old male who presents with a history of 2 minutes of pinpoint left chest pain 12 hours earlier. He has not had any pain since. At that time there was no shortness of Breath or radiation of the pain. The patient has no past medical history, is on no medications and has a normal clinical examination. The nurse performs an ECG and shows it to you. It is a Left Bundle Branch Block(LBBB). You actually feel a bit nervous about it and perform a troponin, which is normal. What do you do now?

In a 2005 study (Mayo Clin Proc) Miller et al., performed a retrospective study of 723 patients. Almost half of the patients had left bundle branch block(LBBB), the other half had right bundle branch block. Those patients with any form of bundle branch block and no complicating factors such as diabetes, hypertension or hypercholesterolaemia, had increased long term mortality compared to controls. Those with LBBB showed an increased risk of cardiac related morbidity. This has been found in many other epidemiological studies.

Littman (J Electrocardiol, 2000) looked at the effects of LBBB and found that it can cause asynchronous myocardial activation which may trigger ventricular remodelling. It is also associated with impaired systolic and diastolic function.

So what to do?

In this patient, who is well, with atypical and short-lived chest pain and a normal troponin, it is important to have follow up. This should take the form of an outpatient echocardiogram looking for valvular abnormalities or cardiomyopathy. If this is normal, then there is not much else to do, except to follow up over periods of time.

If there was any issue of coronary artery disease then the patient should also have a stress/thallium study.