381
Modelling of IMA flow to incorporate these features produces predicted velocity profiles that match those recorded clinically. Acute distal obstruction should not affect systolic flow but diastolic flow would be reversed; we have not yet seen this pattern clinically. Low resting graft flows have not yet been observed in association with a major change in the systolic to diastolic time-averaged velocity ratio, which may indicate that graft compliance and conductance tend to change in the same direction. To our surprise, resting graft flow was not consistently greater than flow in the ungrafted IMA, and we found little difference in diameter between the grafted and ungrafted vessels. IMA grafts are known to dilate in response to increased bloodflow, but our measurements were made during the early postoperative period and there may yet be further arterial remodelling. Nevertheless, we did find flow to be related to the quality of the coronary arterial bed into which the IMA graft is implanted (?-=0-75, p=0’04). The flows we have measured
much lower than those recorded with electromagnetic flow-meters immediately after completion of the anastomosis,s but such measurements are made in anaesthetised patients, often after direct application of vasodilators to the grafts. Clinical application of the technique must take account of its limitations: although the ungrafted IMA was found in all patients, 14 grafts (10 left IMA, 4 right IMA) could not be detected. In 1 patient with bilateral grafts but in whom neither IMA could be imaged, subsequent angiography showed very poor flow in the left graft but the right was widely patent. Thus failure to image a graft does not indicate graft failure, unless an earlier study showed a patent graft. The limited accuracy with which small-vessel diameter can be measured by ultrasound will be reflected in any flow calculations: clinical use of duplex ultrasound to follow up are
patients after IMA grafts should therefore take note of qualitative and quantitative changes in velocity profiles as well as total graft blood-flow. Flow measurements during angiography also show that competing residual blood-flow from the proximal coronary artery reduces resting IMA graft blood-flow,6 and patients with a proximally occluded native vessel may need to be studied for physiological or pharmacological investigations in which IMA graft bloodflow is taken
to
reflect total blood-flow
to an area
of
myocardium. Despite these limitations, transcutaneous assessment of IMA graft blood-flow may represent a valuable technique both for clinical follow-up and for studies in cardiac physiology and pharmacology. Canver and colleagues7 have reported use of a similar technique for preoperative IMA assessment.
REFERENCES 1.
Loop FD, Lytle BW, Cosgrove DM, et al. Influence of the internalmammary-artery graft on 10 year survival and other cardiac events. N Engl J Med 1986; 314: 1-6. 2. Barner HB, Swartz MT, Mudd JG, Tyras DH. Late patency of the internal mammary artery as a coronary bypass conduit. Ann Thorac Surg 1982; 34: 408-12. 3. Evans DH, McDicken WN, Skidmore R, Woodcock JP. Doppler ultrasound: physics, instrumentation and clinical applications. Chichester: Wiley, 1989: 233-59. 4. Brandt PWT, Partridge JB, Wattie WJ. Coronary arteriography: method of presentation of the arteriogram report and a scoring system. Clin Radiol 1977; 28: 261-65. 5. Mills NL, Bringaze WL. Preparation of the internal mammary graft. J Thorac Cardiovasc Surg 1989; 98: 73-79. 6. Sons H, Becker T, Marx B, Loose B, Schulte HD, Bircks W.
Postoperative ultrasonic duplex scanning of the internal mammary artery. Eur Heart J 1989; 10 (suppl): 304 (abstr). 7. Canver CC, Ricotta JJ, Bhayana JN, Fielder RC, Mentzer RM. Use of duplex imaging to assess suitability of the internal mammary artery for coronary artery surgery. J Vasc Surg 1991; 13: 294-301.
High endothelin-1 immunoreactivity in Crohn’s disease and ulcerative colitis
Both immunological hypersensitivity and vascular abnormalities have been implicated in the pathogenesis of inflammatory bowel disease. In an attempt to link the two hypotheses, we sought evidence of local production of endothelin-1, a potent vasoconstrictor, in patients with Crohn’s disease and ulcerative colitis. An immunohistochemical method was used to detect endothelin-1 in tissue samples from sixteen Crohn’s disease patients, nine ulcerative colitis patients, and thirteen controls. In the controls, positively staining cells were infrequent in both lamina propria (mean 0·9% of total cells, 95% confidence interval 0·1-1·7%) and submucosa (2·3%, 0·4-4·1%). The percentage of endothelinimmunoreactive cells was significantly higher in the two disease groups than in the controls. Among the Crohn’s disease patients, there were more immunoreactive cells in the submucosa than in the lamina propria (19·1%, 15·2-22·1% vs 12·3%, whereas the converse was 8·1-16·5%; p
Modelling of IMA flow to incorporate these features produces predicted velocity profiles that match those recorded clinically. Acute distal obstruction should not affect systolic flow but diastolic flow would be reversed; we have not yet seen this pattern clinically. Low resting graft flows have not yet been observed in association with a major change in the systolic to diastolic time-averaged velocity ratio, which may indicate that graft compliance and conductance tend to change in the same direction. To our surprise, resting graft flow was not consistently greater than flow in the ungrafted IMA, and we found little difference in diameter between the grafted and ungrafted vessels. IMA grafts are known to dilate in response to increased bloodflow, but our measurements were made during the early postoperative period and there may yet be further arterial remodelling. Nevertheless, we did find flow to be related to the quality of the coronary arterial bed into which the IMA graft is implanted (?-=0-75, p=0’04). The flows we have measured
much lower than those recorded with electromagnetic flow-meters immediately after completion of the anastomosis,s but such measurements are made in anaesthetised patients, often after direct application of vasodilators to the grafts. Clinical application of the technique must take account of its limitations: although the ungrafted IMA was found in all patients, 14 grafts (10 left IMA, 4 right IMA) could not be detected. In 1 patient with bilateral grafts but in whom neither IMA could be imaged, subsequent angiography showed very poor flow in the left graft but the right was widely patent. Thus failure to image a graft does not indicate graft failure, unless an earlier study showed a patent graft. The limited accuracy with which small-vessel diameter can be measured by ultrasound will be reflected in any flow calculations: clinical use of duplex ultrasound to follow up are
patients after IMA grafts should therefore take note of qualitative and quantitative changes in velocity profiles as well as total graft blood-flow. Flow measurements during angiography also show that competing residual blood-flow from the proximal coronary artery reduces resting IMA graft blood-flow,6 and patients with a proximally occluded native vessel may need to be studied for physiological or pharmacological investigations in which IMA graft bloodflow is taken
to
reflect total blood-flow
to an area
of
myocardium. Despite these limitations, transcutaneous assessment of IMA graft blood-flow may represent a valuable technique both for clinical follow-up and for studies in cardiac physiology and pharmacology. Canver and colleagues7 have reported use of a similar technique for preoperative IMA assessment.
REFERENCES 1.
Loop FD, Lytle BW, Cosgrove DM, et al. Influence of the internalmammary-artery graft on 10 year survival and other cardiac events. N Engl J Med 1986; 314: 1-6. 2. Barner HB, Swartz MT, Mudd JG, Tyras DH. Late patency of the internal mammary artery as a coronary bypass conduit. Ann Thorac Surg 1982; 34: 408-12. 3. Evans DH, McDicken WN, Skidmore R, Woodcock JP. Doppler ultrasound: physics, instrumentation and clinical applications. Chichester: Wiley, 1989: 233-59. 4. Brandt PWT, Partridge JB, Wattie WJ. Coronary arteriography: method of presentation of the arteriogram report and a scoring system. Clin Radiol 1977; 28: 261-65. 5. Mills NL, Bringaze WL. Preparation of the internal mammary graft. J Thorac Cardiovasc Surg 1989; 98: 73-79. 6. Sons H, Becker T, Marx B, Loose B, Schulte HD, Bircks W.
Postoperative ultrasonic duplex scanning of the internal mammary artery. Eur Heart J 1989; 10 (suppl): 304 (abstr). 7. Canver CC, Ricotta JJ, Bhayana JN, Fielder RC, Mentzer RM. Use of duplex imaging to assess suitability of the internal mammary artery for coronary artery surgery. J Vasc Surg 1991; 13: 294-301.
High endothelin-1 immunoreactivity in Crohn’s disease and ulcerative colitis
Both immunological hypersensitivity and vascular abnormalities have been implicated in the pathogenesis of inflammatory bowel disease. In an attempt to link the two hypotheses, we sought evidence of local production of endothelin-1, a potent vasoconstrictor, in patients with Crohn’s disease and ulcerative colitis. An immunohistochemical method was used to detect endothelin-1 in tissue samples from sixteen Crohn’s disease patients, nine ulcerative colitis patients, and thirteen controls. In the controls, positively staining cells were infrequent in both lamina propria (mean 0·9% of total cells, 95% confidence interval 0·1-1·7%) and submucosa (2·3%, 0·4-4·1%). The percentage of endothelinimmunoreactive cells was significantly higher in the two disease groups than in the controls. Among the Crohn’s disease patients, there were more immunoreactive cells in the submucosa than in the lamina propria (19·1%, 15·2-22·1% vs 12·3%, whereas the converse was 8·1-16·5%; p
