Isolated Right Ventricular Myocardial Infarction in Patients with Coronary Artery Bypass Grafts

To the Editor:

I read with interest the article in the Texas Heart Institute Journal by Franco and colleagues¹ about isolated right ventricular myocardial infarction (RVMI). First, I want to thank the authors for reminding us that isolated RVMI can easily be misdiagnosed as acute anterior myocardial infarction (MI) and should be considered in the differential diagnosis.

In clinical practice, isolated RVMI is rare in comparison with anterior MI.² There are important differences in the approach to treating these types of MI, particularly in regard to vasodilator medication. Therefore, the differential diagnosis is important, especially in centers without the capability of performing primary percutaneous coronary intervention. ST-segment elevation in the precordial leads is characteristic of anterior MI caused by left anterior descending coronary artery occlusion. However, ST-segment elevation in leads V₁ through V₃ or V₄ has also been reported during isolated RVMI. The decrease in magnitude of the ST-segment elevation in the precordial leads V₁ through V₃ or V₄ and progressive regression of ST segments without Q-wave formation on electrocardiography suggests isolated RVMI rather than anterior MI.³

Franco and colleagues mentioned some causes of isolated RVMI. Another cause is proximal acute occlusion of a dominant right coronary artery (RCA) in a saphenous vein graft to the RCA.⁴ In this circumstance, the inferior part of the left ventricle is preserved by the saphenous vein graft and does not become ischemic. If the right ventricular branch of the RCA does not receive enough retrograde blood supply from the graft, occlusion of the proximal dominant RCA can induce isolated RVMI. Therefore, isolated RVMI should be considered in patients who have histories of coronary artery bypass grafting and ST-segment elevation in leads V₁ through V₃ or V₄ on electrocardiography.