Bundle branch block

Ultimately, the fascicles divide into millions of Purkinje fibres, which in turn interdigitate with individual cardiac myocytes, allowing for rapid, coordinated, and synchronous physiologic depolarization of the ventricles.

[citation needed] When a bundle branch or fascicle becomes injured (by underlying heart disease, myocardial infarction, or cardiac surgery), it may cease to conduct electrical impulses appropriately.

In theory a pacemaker like this will shorten the QRS interval, thus bringing the timing of contraction of the left and right ventricles closer together and slightly increasing the ejection fraction.

[citation needed] A bundle branch block can be diagnosed when the duration of the QRS complex on the ECG exceeds 120 ms. A right bundle branch block typically causes prolongation of the last part of the QRS complex and may shift the heart's electrical axis slightly to the right.

People with bundle branch blocks may still be quite active, and may have nothing more remarkable than an abnormal appearance to their ECG.

In more severe cases, a pacemaker may be required to restore an optimal electrical supply to the heart muscle.

Image showing the ECG characteristics of a right bundle branch block and a left bundle branch block . In both cases, the late portion of the widened QRS complex arises from an anomalously conducted depolarization impulse. The direction of this delayed depolarization vector differs based on the structure that is blocked; the impulse travels anterior toward the right ventricle in RBBB and lateral toward the left ventricle in LBBB.