Predicting the best way to reset the heart’s rhythm

Cardiac resynchronization by His pacing: patient selection by high-precision invasive and non-invasive phenotyping (Dr Nadine Ali)

People with abnormal heart rhythms are sometimes treated with a method called ‘pacing’ which uses small electrical pulses to reset their heartbeat. Scientists have recently discovered a new method for resetting the heartbeat called His-pacing, which works on a bundle of fibres in the heart called the ‘His-bundle’. This bundle is an important part of the overall electrical conduction system in the heart needed to maintain a normal heart rhythm. Left bundle branch block (LBBB) is an abnormal heart rhythm caused by a blockage in the heart’s electrical impulses. His-pacing seems to work better than other treatment methods in people with LBBB. However, His-pacing doesn’t work in all LBBB patients. This lack of response might be because the electrical conduction in the His-bundle is itself blocked, or because the electrical abnormality in the heart is too far away from the His-bundle. Dr Whinnett wants to develop a way of detecting if the electrical conduction block is within the His-bundle or further away. This would help doctors know whether His-pacing will work in people with LBBB or whether they would better suit the standard pacing treatment, called biventricular pacing (BVP). Moreover, if Dr Whinnett finds that His-pacing is unsuccessful in people with LBBB, even when the fault is within the His-bundle, this will show that the method needs to be improved.