If I was poisoned with a drug to stop my heart beating, would my pacemaker keep me alive?
It depends on the circumstances. Drugs affecting the heart鈥檚 ability to contract act either on the specialised electrical conduction systems that trigger a heartbeat or on the ability of the heart muscle to generate contractile force. In the former case, a pacemaker will continue to stimulate cardiac contractions even when its intrinsic electrical activity has been suppressed. In the latter, the drugs will prevent the heart muscle from contracting, so the pacemaker will not keep the heart beating. Cardioplegia, the technique used to paralyse the heart during open-heart surgery, uses the latter approach. Once beating ceases, surgeons can add bypass grafts or replace valves. When the cardioplegia is reversed, the heart muscle resumes its contractions.
Rafe Chamberlain-Webber, Consultant cardiologist, Edge, Gloucestershire, UK
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