Carotid Sinus Massage: Racing the AV Node's Refractory Period

This simulator models the exact clinical mechanism by which carotid sinus massage terminates paroxysmal supraventricular tachycardia (AVNRT): a self-sustaining wavefront circulates around a discretized 2D reentry loop as long as the circuit's cycle length exceeds the AV node's effective refractory period. Holding the massage control drives a physiologically-timed vagal tone burst that prolongs the AV nodal refractory period in real time; once that refractory period catches up to the cycle length, the returning wavefront meets still-refractory tissue, conduction blocks, the circuit is visibly extinguished on the ring and on the live stylized ECG strip, and the sinoatrial node resumes normal pacing. Adjustable massage pressure, carotid sinus sensitivity, and reentry rate reproduce the real bedside variability in whether — and how firmly — the maneuver succeeds. Drag the ring to rotate the view and follow the wavefront around the circuit.