Paradoxic heart rate deceleration during exercise. Relationship to a mid-right coronary artery stenosis

A patient developed paradoxic deceleration of his heart rate at a high exercise level. Angioplasty of a right coronary artery stenosis distal to the sinoatrial branch and institution of diltiazem therapy resulted in normal cardioacceleration during repeated exercise testing. This unique pathophysiologic response appears to be due to direct or indirect effects of ischemia.