Conduction system in a patient with Prinzmetal's angina and transient atrioventricular block

His bundle recordings obtained during and between attacks of Prinzmetal's variant angina and transient atrioventricular (A-V) block were followed by a comprehensive serial section study of the conduction system in a 33 year old woman. Recordings between attacks showed normal A-H and H-V intervals. During an attack there was block proximal to the His bundle recording site. Pathologic studies revealed severe narrowing of the right coronary artery. Arteriolosclerosis of the heart was diffuse. Insignificant changes were found in the approaches to the A-V node and the A-V node itself. Major changes found in the left bundle branch had no counterpart in the electrocardiogram; the discordance in these findings is discussed.