Competitive Blood Flow in the- Coronary Circulation Simulating Progression of Proximal Coronary Artery Disease After Saphenous Vein Bypass Surgery*

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1 Clin. Cardiol. 7, Clinical Cardiology Publishing Co., Inc. Competitive Blood Flow in the- Coronary Circulation Simulating Progression of Proximal Coronary Artery Disease After Saphenous Vein Bypass Surgery* w. P. MILLER, M.D.,? H. DASH, M.D. Division of Cardiology, Department of Medicine, The Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA Summary: We report a case of competitive blood flow in the left coronary circulation after saphenous vein bypass grafting that resulted in the apparent progression of a proximal stenosis to total occlusion at coronary angiography. Repeat angiography with careful attention to catheter position and adequate injection of contrast agent demonstrated the actual anatomy and showed that there was no postoperative change in the native coronary circulation. The true incidence of progression of proximal coronary disease after saphenous vein bypass surgery is unknown, and reported figures may be falsely elevated because of unrecognized competitive flow patterns simulating obstruction. Key words: aortocoronary bypass, coronary disease, angiography *Supported in part by The Caplan Fund.?Present affiliation: Cardiology Section, Department of Medicine, University of Wisconsin School of Medicine, Madison, Wisconsin, USA Address for reprints: Harold Dash, M.D. Division of Cardiology Milton S. Hershey Medical Center P.O. Box 850 Hershey, Pennsylvania 17033, USA Received: October 4, 1983 Accepted: November 22, 1983 Introduction In the past 10 years, numerous investigators have reported an accelerated progression of coronary artery disease in patients having saphenous vein bypass surgery. Such progression has occurred primarily in those arteries grafted, particularly in sites proximal to patent saphenous vein bypass grafts (Aldridge and Trimble, 1971; Bourassa et al., 1973; Bousvaros et al., 1972; Glassman et al., 1973; Guthaner et al., 1979; Itscoitz et al., 1975; Malinow et al., 1973; Seides et al., 1978). The reported incidence of progression of disease in grafted arteries has varied widely, however. Although the timing of postoperative evaluation and the selection of patients studied account in part for such wide variation, the presence of competitive flow mimicking progression of proximal disease in grafted vessels with two sources of blood supply may also be an important factor. In this report, we emphasize the importance of identifying competitive flow relationships in patients undergoing angiographic evaluation after saphenous vein bypass surgery. Case Report A 54-year-old male with severe mitral regurgitation and a 50% diameter stenosis of the left anterior descending artery (Fig. 1) underwent mitral valve replacement and a single saphenous vein bypass graft. His perioperative course was complicated by an acute anteroseptal myocardial infarction. Seven months later he had repeat cardiac catheterization as part of an evaluation for a history of syncope with exertion and atypical chest pain.

2 180 Clin. Cardiol. Vol. 7, March 1984 FIG. 1 Preoperative left coronary angiogram in a left anterior oblique projection. A 50% diameter stenosis is present in the midlelt anterior descending artery (large arrow). Right and left heart pressures and the hemodynamic response to exercise were normal. There was no significant pressure gradient across the prosthetic mitral valve. Left ventricular cineangiography showed anterior and apical hypokinesis which was new compared to the preoperative study. Angiography of the native left coronary artery demonstrated a normal left main and circumflex system and apparent occlusion of the left anterior descending artery at the site of previous stenosis with faint visualization of a first diagonal branch (Fig. 2). The initial graft injection showed a patent saphenous vein with normal antegrade filling of the distal left anterior descending artery. However, retrograde flow in the left anterior descending did not pass the site of known stenosis. Moreover, there appeared to be segmental loss of the left anterior descending artery just distal to the site of the previous stenosis, which suggested progression to total occlusion at that site (Fig. 3). Repeat graft angiography with better ostial intubation and a somewhat more vigorous hand injection resulted in visualization of the entire left coronary circulation (Fig. 4). The lesion in the left anterior descending was unchanged from the preoperative study. Discussion Aldridge and Trimble (197 1) published the first report of progression of proximal coronary artery disease in vessels undergoing saphenous vein bypass gmfting. Four of 8 stenotic arteries supplied by patent grafts had progression to total occlusion at restudy 6 months postoperatively. One year later Bousvaros et al. (1972) described the development of total occlusions in 6 of 9 vessels with patent grafts. They recognized, however. that 2 of the occlusions were apparent rather than real. With injection of radiographic contrast into the native vessel, the contrast moved in a to-and-fro pattern at the site of apparent obstruction. Moreover, injection of the graft resulted in retrograde filling of the native coronary artery proximal to the point of apparent occlusion. When present, the to-and-fro motion of contrast is presumptive evidence for competitive flow and simulated rather than real occlusion (Bousvaros et al., 1972; Winer et al., 1979). However, such a pattern of' motion may not be present (Ross et al., 1977). Othen (Griffith et al., 1973; Pasternak et al., 1973; Winer er al., 1979) have suggested that a diagnosis of progression of proximal disease to complete occlusion in a native vessel rests on the demonstration of loss of perfusion of' a segment of the coronary artery in question. When native coronary and graft angiograms show no segmental loss of the coronary artery, then one must assume the occlusion is simulated rather than real despite the absence of antegrade flow beyond the site of stenosis in the nativc coronary vessel. Of interest is that the 3 examples of postoperative progression of coronary disease presented by Aldridge and Trimble (1971) may all represent simulated occlusions, as no substantial segmental loss can be identified in their figures. On the other hand, our case demonstrates that segmental loss of a coronary

3 W. P. Miller and H. Dash: Competitive coronary flow after bypass surgery 181 FIG. 2 Postoperative native left coronary angiogram in a left anterior oblique projection. Apparent total occlusion of the left anterior descending artery is present (large arrow). FIG. 3 Postoperative saphenous vein graft (small arrow) angiogram in a left anterior oblique projection. Apparent total occlusion of the left anterior descending artery is again present (large arrow). Comparison with Fig. 2 demonstrates a segmental loss of filling in the artery suggesting progression of the coronary artery disease to total occlusion.

4 182 Clin. Cardiol. Vol. 7, March 1984 FIG. 4 Repeat saphenous vein graft (small arrow) angiogram in a projection similar to Fig. 3. Large arrows bracket the area of segmental filling loss demonstrated by comparing Figs. 2 and 3, which was apparent rather than real. The lesion in the left anterior descending artery is not well seen in this view but was unchanged from the preoperative study. artery does not by itself guarantee that the vessel is in fact totally occluded. Ross et al. (1977) reported that competitive flow and simulated occlusion of a proximal coronary artery after bypass surgery was demonstrated in 3 cases only after the injection catheter became wedged within the ostium of the native coronary or the bypass graft. They postulated that the wedged position of the catheter resulted in a high pressure contrast injection which overcame the competitive flow. Their cases and the one presented in this report document the difficulty of differentiating true progression of coronary disease from apparent progression with competitive flow. In the case reported here, the left anterior descending artery appeared occluded on the initial angiograms of the native left coronary and bypass graft. To-and-fro motion of contrast was not visible on the video tape images although such motion was subsequently identified on the cineangiograms. Better positioning of the catheter in the ostium of the bypass graft and a somewhat more forceful injection of contrast agent overcame the competitive flow in the native coronary and demonstrated the actual anatomy. Had the competitive flow not been overcome, we would have assumed that the left anterior descending artery was totally occluded, a finding consistent with the perioperative myocardial infarction. Because the presence of competitive flow makes the interpretation of postoperative coronary angiography so difficult, the true incidence of postoperative progression of proximal CO~OM~~ disease after saphenous vein bypass grafting is unknown. It is not surprising that in the articles referenced here the reported incidence of progression of disease in vessels supplied by patent grafts has vaned from 19% to 96%. Even among those studies that tried to account for competitive flow, the reported incidence of progression of native disease has varied considerably (Bousvaros et al., 1972; Griffith et al., 1973; Pasternak et al., 1973; Winer et al., 1979). Nevertheless, in clinical practice it is useful to try to avoid mistaking apparent for true occlusions by utilizing the techniques reviewed in this report: (1) Selective angiograms of the native coronary and saphenous vein bypass graft must be compared to determine whether segmental loss of the native coronary artery can be demonstrated. Such segmental loss is suggestive but not diagnostic of progression of native disease. (2) The presence of to-and-fro motion of radiographic contrast at the site of apparent obstruction, either with the native coronary or the graft injection, indicates competitive flow rather than true occlusion. (3) Careful positioning of the catheter tip in the ostia of the graft and native coronary is important, but a wedged catheter position with high pressu~ hand contrast injection should be avoided. In the latter situation, the benefits of identifying competitive flow probably do not outweigh the risks of such an injection.

5 W. P. Miller and H. Dash: Competitive coronary flow after bypass surgery 183 Acknowledgments We thank Dr. Lawrence K. Harris for referring the patient to us. Nina Kaye Gingerich typed the manuscript. References Aldridge HE, Trimble AS: Progression of proximal coronary artery lesions to total occlusion after aortacoronary saphenous vein bypass grafting. J Thorac Cardiovasc Surg 62, 7 (1971) Bourassa MG, Goulet C, Lesperance J: Progression of coronary arterial disease after aortocoronary bypass grafts. Circulation 47, 48 (Suppl 111), 127 (1973) Bousvaros G, Peracha AR, Chaudhry MA, Grant C, Older TM, Pifarre R: Increase in severity of proximal coronary disease after successful distal aortocoronary grafts. Circulation 46, 870 (1972) Glassman E, Spencer FC, b uss KR, Weisinger B, Isom OW: Changes in the underlying coronary circulation secondary to bypass grafting. Circulation 50 (Suppl 11), 80 (1973) Gnffith LSC, Achuff SC, Conti CR, Humphries JO, Brawley RK, Gott VL, Ross RS: Changes in intrinsic coronary circulation and segmental ventricular motion after saphenousvein coronary bypass graft surgery. N Engl J Med 288,589 ( 1973) Guthaner DF, Robert EW, Alderman EL, Wexler L: Longterm serial angiographic studies after coronary artery bypass surgery. Circulation 60, 250 (1979) Itscoitz SB, Redwood DR, Stinson EB, Reis RL, Epstein SE: Saphenous vein bypass grafts: Long-term patency and effect on the native coronary circulation. Am J Cardiol 36, 739 (1975) Malinow MR, Kremkau EL, Kloster FE, Bonchek LI, Rosch J: Occlusion of coronary arteries after vein bypass. Circulation 47, 1211 (1973) Pasternak R, Cohn K, Selzer A, Langston MF Jr.: Enhanced rate of progression of coronary artery disease following aortocoronary saphenous vein bypass surgely. Am J Med 58, 166 (1973) Ross AM, Hammond GL, Cohen LS, Wolfson S: Angiographic evaluation of saphenous vein bypass grafts: Artifactual occlusion caused by dual sources of flow. Am J Cardiol 39, 384 (1977) Seides SF, Borer JS, Kent KM, Rosing DR, McIntoch CL, Epstein SE: Long-term anatomic fate of coronary-artery bypass grafts and functional status of patients five years after operation. N Engl J Med 298, 1213 (1978) Winer HE, Glassman E, Spencer FC: Mechanism of relief of angina after coronary bypass surgery. Am J Cardiol 44, 202 (1979)