Percutaneous Revascularization of Chronic Total Occlusion of Left Anterior Descending Artery (full title below)

Percutaneous Revascularization of Chronic Total Occlusion of Left Anterior Descending Artery Using Contralateral Injection via Isolated Conus Artery

From the *Division of Cardiology, Department of Medicine, Keio University School of Medicine, Tokyo, and the §Division of Radiology, Department of Medicine, Keio University School of Medicine, Tokyo, Japan. The authors report no conflicts of interest regarding the content herein. Manuscript submitted December 15, 2008, and accepted January 5, 2009. Address for correspondence: Akio Kawamura, MD, Division of Cardiology, Department of Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. E-mail: kawamura@cpnet.med.keio.ac.jp

_______________________________________________ ABSTRACT: A 74-year-old male underwent cardiac catheterization that revealed a chronic total occlusion of the proximal left anterior descending coronary artery (LAD). The right coronary artery provided only faint collateral circulation to the LAD. Multislice computed tomography (MDCT) disclosed that a conus artery took off directly from the aorta and provided good collateral circulation to the LAD. Percutaneous coronary intervention of the LAD was successfully performed using contralateral injection via the isolated conus artery. Whenever sufficient collateral filling is not visualized in a chronically occluded LAD, an isolated conus artery should be considered. MDCT is a helpful tool in this setting.

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J INVASIVE CARDIOL 2009;21:E84–E86 The conus artery is one of the important collateral pathways to the chronically occluded left anterior descending coronary artery (LAD).1,2 Failure to visualize the artery by coronary angiography can result in underestimation of the collateral circulation, as well as overestimation of the length of the chronic total occlusion (CTO). While the conus artery is usually a branch of the right coronary artery (RCA), it arises directly from the aorta in approximately 50% of human hearts at autopsy.3,4 In these cases, it is called the isolated conus artery. Here we report a case of successful percutaneous revascularization of a chronic total occlusion (CTO) of the LAD using super-selective contralateral injection via an isolated conus artery. Case Report. A 74-year-old male with exertional angina and a positive stress test was referred for cardiac catheterization, which revealed a CTO of the proximal LAD (Figure 1). The RCA provided only faint collateral circulation to the LAD, and left ventriculography showed normal wall motion with an ejection fraction of 60%. The length of the occlusion was estimated to be > 30 mm. Because of the mismatch between good left ventricular wall motion and poor perfusion of the LAD area, other potential collateral sources were considered. With a 6 Fr internal mammary artery catheter withdrawn from the ostium of the RCA and rotated anteriorly, a conus artery was visualized and found to take off directly from the aorta a few centimeters above the origin of the RCA. The isolated conus artery was providing better collateral filling to the distal part of the chronically occluded LAD. Multislice computed tomography (MDCT) also revealed the collateral network and clearly visualized the anatomical location of the isolated conus artery (Figure 2). Percutaneous coronary intervention (PCI) of the LAD was attempted with superselective contralateral injection from the isolated conus artery because nonselective angiograms did not opacify the distal lumen adequately. For cannulation of the conus artery, several guide catheters including a right Judkins, internal mammary, hockey stick, right and left Amplatz were used, but it was challenging to engage those guide catheters selectively. With a 6 Fr left Amplatz 1 guide catheter placed at the bottom of the ascending aorta, but not engaged, a 0.014 inch Fielder FC guidewire (Asahi Intec, Nagoya, Japan) was successfully advanced distally into the isolated conus artery (Figure 3). Next, a 1.8 Fr Finecross microcatheter (Terumo Medical, Tokyo, Japan) was advanced over the guidewire. After the guidewire was withdrawn, blood was allowed to exit back from the microcatheter. Contralateral injection was done gently through the microcatheter with 1 mL of contrast each time, which clearly visualized the distal lumen. At this point, it was evident that the occluded segment was at most 10 mm in length (Figure 4). No major arrhythmia was induced by the injection. Finally, the occluded segment was successfully crossed with a 0.014 inch Conquest Pro 12 g guidewire (Asahi Intec, Nagoya, Japan), and a 3 × 13 mm sirolimus-eluting Cypher™ stent (Cordis Corp., Miami Lakes, Florida) was deployed (Figure 5). Discussion. In PCI of a CTO, clear understanding of the length and course of a totally occluded segment are key to success. The conus artery is one of the important collateral pathways to a chronically occluded left anterior descending coronary artery.1,2 While the artery is usually a branch of the RCA, it arises directly from the aorta in approximately 50% of human hearts at autopsy.3,4 This is called the isolated conus artery, which can be missed at the time of coronary angiography in 20% of cases.5 Failure to visualize the artery by angiography can result in critical underestimation of collateral circulation as well as overestimation of the length of the occluded segment. Although nonselective angiography has been helpful, it can be challenging to find a relatively small conus artery if the origin is distant from the RCA. Even in this setting, MDCT can be a helpful tool to visualize these small arteries.6 Difficulties with PCI of CTOs are largely influenced by the degree to which collateral circulation is opacified. It is important to evaluate the total length of the occluded segment and to clarify the location of the distal lumen, which is the goal for the guidewire to reach. In our case, the guidewire passage would have been more challenging without superselective contralateral injection via the isolated conus artery. Selective conus artery catheterization may be dangerous if it causes sustained myocardial ischemia. Levin et al suggested that careless injection of contrast medium by a catheter wedged into a small vessel could result in ventricular fibrillation.5 In the study by Yamagishi et al, however, the isolated conus artery was selectively engaged and visualized in 45 patients without causing ventricular arrhythmias.7 In our case, we attempted super selective injection from a microcatheter to obtain adequate opacification of the distal segment with as little amount of contrast as possible. Although no major arrhythmia was induced during the injection, it should be done gently with minimal contrast in short duration. Whenever sufficient collateral filling is not visualized in the chronically occluded LAD, the presence of an isolated conus artery should be suspected. In this setting, MDCT is helpful in visualizing the isolated conus artery, which can elude visualization in conventional coronary angiography. Contralateral injection form the isolated conus artery can play a crucial role in successful PCI of CTO of the LAD.

2. Tanigawa J, Petrou M, Di Mario C. Selective injection of the conus branch should always be attempted if no collateral filling visualises a chronically occluded left anterior descending coronary artery. Int J Cardiol 2007;115:126–127.

3. Schlesinger MJ, Zoll PM, Wessler S. The conus artery: A third coronary artery. Am Heart J 1949;38:823–836.

4. Edwards BS, Edwards WD, Edwards JE. Aortic origin of conus coronary artery. Evidence of postnatal coronary development. Br Heart J 1981;45:555–558.

5. Levin DC, Beckmann CF, Garnic JD, et al. Frequency and clinical significance of failure to visualize the conus artery during coronary arteriography. Circulation 1981;63:833–837.

6. Funabashi N, Asano M, Komuro I. Large collateral conus branch to the left anterior descending branch of the coronary artery in a subject with angina pectoris demonstrated by multislice computed tomography. Int J Cardiol 2005;103:105–106.

7. Yamagishi M, Haze K, Tamai J, et al. Visualization of isolated conus artery as a major collateral pathway in patients with total left anterior descending artery occlusion. Cathet Cardiovasc Diagn 1988;15:95–98.