Collateral Myocardial Blush in Inferior Wall Myocardial Infarction: A New Diagnostic Tool to Differentiate Between Occluded Right Coronary and Circumflex Arteries

Abstract: Objectives. The infarct-related artery (IRA) in inferior wall myocardial infarction (IMI) may be problematic to identify due to occasional instances in which the right coronary (RCA) and left circumflex (CX) arteries are both occluded. We sought to investigate if impaired collateral myocardial blush (CMBG) identifies the correct IRA. Methods. Between 2002 and 2010, we retrospectively analyzed 1907 patients who underwent primary angioplasty at our institution. Of these, 44 had an IMI together with total occlusion of both the RCA and CX. Results. Thirty of these had good collaterals to both distal vessels. Ten of this group had impaired CMBG, indicating the IRA. In 2 patients, angioplasty was attempted in the wrong artery in retrospect. Conclusions. The correct IRA may be difficult to identify in patients with IMI and occlusion of both RCA and CX arteries. Impaired CMBG is a new tool to aid in this challenge.

J INVASIVE CARDIOL 2012;24:130–131

Key words: myocardial blush, collaterals, inferior wall myocardial infarction

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Inferior wall myocardial infarction (IMI) is a result of acute occlusion of the right coronary artery (RCA) or the left circumflex artery (CX). In most circumstances, only one of these arteries is occluded — the infarct-related artery (IRA).

In rare situations, both the RCA and CX are found to be totally occluded. In these cases, clinical examination, electrocardiogram, echocardiography, and angiographic appearance of the total occlusion can help to define which is the IRA, but there are occasions in which even these tools fail to clarify which is the culprit artery, leading to intervention in the wrong artery, thus prolonging the time for revascularization.

We recently described a novel method using collateral myocardial blush (CMBG) related to the IRA region, to predict myocardial blush grade (MBG) after revascularization.¹ 

We feel that this method may help in defining the IRA in patients who present with IMI and totally occluded RCA and CX.

Methods

This was a retrospective observational trial. Between 2002 and 2010, a total of 1907 patients underwent primary percutaneous coronary intervention (PPCI) at our institution. Of these, 44 had IMI with both the RCA and CX totally occluded.

Fourteen of this group were excluded either because they had previous coronary bypass surgery, or no collaterals were demonstrated. The remaining 30 patients had well-developed collaterals (Rentrop grade 2 and 3)² to both totally occluded arteries, and these made up the study group. CMBG was assessed in all these patients, as described by us previously.¹

Results

Twenty of these 30 patients demonstrated  CMBG grade 2 and 3, reflecting good tissue perfusion. The remaining 10 patients had abnormal collateral myocardial blush (grade 0 or 1) indicating the IRA. They also demonstrated persistent contrast medium staining in the IRA distal to the occlusion — “collateral no-flow” (Figure 1). This phenomenon is observed faintly after the first injection. However, it is most pronounced after the second and subsequent  injections of dye. At the time, we were not familiar with the significance of this observation and failed to correctly identify the IRA, leading to an unnecessary attempt in 2 patients to open what was in retrospect a chronic total occlusion (CTO).

Discussion

IMI, which accounts for 40%-50% of all acute myocardial infarctions, can be caused by the occlusion of the RCA or the CX. Physical findings, electrocardiography, and echocardiography, especially looking for signs of right ventricular infarction, will point toward the RCA as the IRA. In addition, various electrocardiographic algorithms have been suggested to predict the culprit artery based on analysis of ST-segment elevation and ST-segment depression in different leads.^3-15 These algorithms are based on the concept that in RCA occlusions, the vector of injury is directed inferior and to the right, whereas it is downward, posterior, and to the left in CX occlusions. At angiography, the characteristics of the occlusion (existence of thrombus, ulceration, or ruptured plaque) may point toward the IRA. Nevertheless, in some patients referred for primary percutaneous coronary intervention in ST-elevation IMI, these clues may be of no help, and although the constellation of IMI with totally occluded RCA and CX arteries with good collaterals to both distal vessels is rare, we propose that our observation could be put to valuable use in these patients, in order to correctly identify and minimize the time to open the IRA.

References

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From the Cardiology Department, Soroka Medical Center and Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.
Manuscript submitted October 19, 2011, provisional acceptance given December 20, 2011, final version accepted December 22, 2011.
Address for correspondence: Prof. Reuben Ilia, MD, Director, Cardiology Department, Soroka University Medical Center, POB 151, Beer-Sheva, Israel. Email: iliar@bgu.ac.il