Increasing pre-excitation ("concertina effect") during vasospastic angina

A patient with Wolff-Parkinson-White syndrome and variant angina developed progressive ST-segment elevation in the inferior leads after hyperventilation-induced right coronary artery spasm. At the same time, increasing pre-excitation ("concertina effect") developed with gradual prolongation of the AH interval on His bundle ECG. The ECG changes promptly disappeared after sublingual nitroglycerin, with termination of the chest pain. Transient ischemia induced by coronary artery spasm can be an etiology of increasing pre-excitation.