A 72-year-old woman with a past history of myocardial infarction and bypass surgery is admitted for investigation of frequent angina on exertion:

• Sinus rhythm, 62/min
• 1st degree AV block (PR = 480 msec.)
• Incomplete right bundle branch block (iRBBB)
• ST and T abnormality, consider inferior-lateral ischemia

Coronary angiography demonstrated that the left internal mammary artery graft to the left anterior descending artery was patent and free of lesions. The circumflex artery was normal and supplied collaterals to the right coronary that was occluded in its proximal segment.