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Ann Thorac Surg 1997;64:1876-1877
© 1997 The Society of Thoracic Surgeons

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Correspondence

Reverse Redistribution Phenomenon After CABG: Differences Between ITA and SV Grafts

Second Department of Surgery, Shiga University of Medical Science, Tsukinowa Seta Otsu, Shiga, 520-21 Japan

To the Editor:

We reported the clinical significance of reverse redistribution phenomenon (RR) using thallium 201 exercise myocardial single-photon emission computed tomography (SPECT) before and after coronary artery bypass grafting (CABG) [1]. The patients exhibiting postoperative RR showed significant postoperative improvement in left ventricular wall motion, compared with preoperative motion. The determination of quantitative myocardial viability before and after the operation revealed that patients exhibiting postoperative RR showed significant postoperative improvement in myocardial viability. The onset of RR after CABG suggests that the operation results in a sufficient supply of blood flow to the residual myocardium. The reviewer of our article [1] recommended that clinical differences between the left internal thoracic artery graft (ITAG) and greater saphenous vein graft (SVG) should be evaluated.

In this study, clinical differences between cases using ITAG and SVG were evaluated. Between March 1, 1989, and December 31, 1991, we studied 23 consecutive patients (21 men and 1 woman) who underwent ²⁰¹Tl myocardial exercise SPECT before and after CABG that included the left anterior descending artery (LAD). The mean age at operation was 55.4 ± 10.2 years. Autografts for LAD were obtained from SVG in 17 patients, and from ITAG in 6. Thirteen patients had a history of preoperative anteroseptal myocardial infarction in the area perfused by the LAD. There were no patients with evidence of perioperative myocardial infarction. Thallium 201 exercise myocardial SPECT was performed (mean, postoperative day 55). The mean intervals between myocardial infarction and operation were 3.8 ± 2.3 months. The study was approved by the institutional review board, and informed consent was obtained from each patient.

After CABG, coronary angiography was performed (mean, postoperative day 63) and again about 1 year later. All grafts involving the LAD were patent on postoperative coronary angiography. Myocardial viability was evaluated by quantitative analysis. A quantitative analysis of ²⁰¹Tl exercise myocardial SPECT images was performed using the method described in our report [1].

Preoperatively, all patients exhibited redistribution in the area perfused by the LAD. Early postoperative ²⁰¹Tl SPECT showed RR in 33% of the ITAG group and 59% of the SVG group. The SVG group exhibited significant postoperative decreases in these parameters: defect volume ratio (DVR) (from 52.4 ± 16.7 to 30.1 ± 15.4; p < 0.05), mean defect severity (MDS) (from 13.1 ± 3.4 to 8.5 ± 3.8; p < 0.05), and defect severity index (DSI) (from 6.8 ± 0.56 to 2.6 ± 0.53; p < 0.05). The ITAG group exhibited significant postoperative decreases in these parameters: DVR (from 53.5 ± 15.4 to 34.7 ± 12.5; p < 0.05), MDS (from 12.6 ± 4.8 to 9.2 ± 4.5; p < 0.05), and DSI (from 6.7 ± 0.52 to 3.2 ± 0.42; p < 0.05). One year after CABG, none of the patients in the SVG group showed RR, whereas 67% in the ITAG group showed RR. The ITAG group exhibited significant postoperative decreases in these parameters: DVR (from 34.7 ± 12.5 to 20.5 ± 8.6; p < 0.05), MDS (from 9.2 ± 4.5 to 7.2 ± 3.1; p < 0.05), and DSI (from 3.2 ± 0.42 to 1.5 ± 0.40; p < 0.05). In the ITAG group, DVR, MDS, and DSI improved significantly 1 year after CABG compared with early results after CABG. In contrast, the SVG group showed no significant differences between findings in the early period and those 1 year later: DVR (from 30.1 ± 15.4 to 29.9 ± 7.2), MDS (from 8.5 ± 3.8 to 8.8 ± 2.8), and DSI (from 2.6 ± 0.53 to 2.6 ± 0.49). Preoperatively, the ITAG group had a higher DVR, MDS, and DSI than the SVG group (p < 0.05).

The present study suggests that blood supply soon after CABG was lower but 1 year after operation was higher in ITAG than SVG. Several perioperative studies have shown that blood flow in the anastomosed ITAG was lower than that in the SVG at rest or after ischemic reactive or pharmacologically induced coronary hyperemia [2]. In contrast, other studies performed later after bypass grafting have suggested that these alterations in blood flow are transient [3]. In previous studies, ITAGs and vein grafts with the same characteristics showed no differences in 1-year patency rates [4]. It is still controversial whether ITAGs can provide adequate flow at periods of peak myocardial demand [5].

References

1. Watarida S, Onoe M, Sugita T, et al. The clinical significance of reverse redistribution phenomenon after coronary bypass grafting. Ann Thorac Surg 1995;59:1528–33.[Abstract/Free Full Text]
2. McCormic JR, Kanedko M, Baue AE, et al. Blood flow and vasoactive drug effects in internal mammary and venous bypass grafts. Circulation 1975;51(Suppl 1):172–80.
3. Schmidt DH, Blau F, Hellman C, et al. Isoproterenol-induced flow responses in mammary and vein grafts. J Thorac Cardiovasc Surg 1980;80:319–26.[Medline]
4. Meer J, Hillege HL, Gilst WH, et al. A comparison of internal mammary artery and saphenous vein grafts after coronary artery bypass surgery. No difference in 1-year occlusion rates and clinical outcome. Circulation 1994;90:2367–74.[Abstract/Free Full Text]
5. Loop FD, Thomas JD. Hypoperfusion after arterial bypass grafting. Ann Thorac Surg 1993;56:812–3.[Medline]

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