LETTERS TO T H E E D I T O R S The Editors invite readers to submit letters commenting on the contents of articles that appear in the Journal. Also welcome are brief communications in letter form reporting investigative or clinical observations without extensive documentation and with brief bibliography (five titles or less), not requiring peer review but open to critique by readers. Letters to the Editors should be no more than 500 words in length and they may have to be edited for publication.

Immunologic r e s p o n s e t o c o l l a g e n - i m p r e g n a t e d vascular grafts To the Editors:

In a recent article in the JOURNAL, the immunologic response to collagen-impregnated vascular grafts was reported.1 We have published an article on the same subject and would like to give some comments and a follow-up of our report. 2 In our study, 4 of 11 patients who received a collagen-impregnated graft had circulating antibodies against the graft collagen, as well as against purified bovine type I collagen. These patients have now been reexamined 1 year after surgery. In two of the patients increased antibody titers persisted, but in two patients the antibody titers had returned to baseline. We also tested the sera from these four patients for presence of circulating antibodies to human skin type I collagen (Calbiochem-Behring Corp., San Diego, Calif.). Sera from all four patients cross-reacted with this collagen preparation. Interestingly, one of the patients, whose antibody titer against the bovine collagen had normalized 1 year after surgery, showed persisting reactivity with the human type I collagen. The findings of cross-reactivity are in contrast to the findings in the Canadian study) in which no such reaction was found. The four patients did not have any surgical or other complication during the follow-up period. In conclusion, both studies showed that some patients receiving collagen-impregnated grafts have circulating antibodies against bovine type I collagen. Furthermore, in our study cross-reactivity with human type I collagen occurred and in some patients the antibody response persisted for at least 1 year after surgery. No clinical short-term consequences seem to be related to development of these antibodies. The long-term consequences are presently unknown. Tore Saxne, A4D, PhD

Department of Rheumatology Lars Norgren, A4d), PhD

Department of Surgery Lund University Hospital S-221 85 Lurid, Sweden

REFERENCES 1. The Canadian Multicenter Hemashield Study Group. Immunologic response to collagen-impregnated vascular grafts: a randomized prospective study, l VASe SURG 1990;12:741-6. 2. Norgren L, Holt~is S, Persson G, Ribbe E, Saxne T, Th6rne J. 730

Immune response to collagen-impregnated Dacron doublevelour grafts for aortic and aorto-femoral reconstructions. Eur J Vasc Surg 1990;4:379-84. 24/41/32582 Intermittent claudication as a manifestation of silent myocardial ischemia: A pilot study To the Editors:

I read with great interest the paper entitled "Interm~ttent claudication as a manifestation of silent myocardial ischemia: A pilot study" in the JOURNAL OF VASCULAR SURGERY (1991;14: 76-86). My question is the following: Is myocardial ischemia really 'silent' in these parents if they manifest angina in their legs, which is intermittent dandication, rather than in their chest? I generally teach my housestaff on ward rounds that patients with coronary artery disease and intermittent claudication generally do not complain of angina, because the leg pain usually stops the patient from walking too far before they develop angina. Now we have a second explanation for the association of 'silent' myocardial ischemia and intermittent clandication, that is, myocardial ischemia produces left ventricular dysfunction and a decrease in stroke volume leading to a large fall in ankle pressure and early onset of intermittent daudication as the authors of the pilot study postulated. Tsung O. Cheng, MD

Professor of Medicine The George Washington University Medical Center 2150 Pennsylvania Ave., N.W. Washington, D.C, 20037 24/41/32669 Epidural spinal cord electrical stimulation: An

unproven methodology for management of lower extremity ischemia To the Editors:

We read with interest the recent editorial of LoGerfo concerning epidural spinal cord electrical stimulation (ESES), 1 which in fact reviewed our recent article in the JOURNAL OF VASCULAR SURGERY.2 The main criticism referred to the absence of a control group, which should receive the same ancillary treatment as provided in the ESES group. We fully agree with this statement, and we always advocate the design and accomplishment of prospective randomized trials. 3 These controlled studies,

Immunologic response to collagen-impregnated vascular grafts.

LETTERS TO T H E E D I T O R S The Editors invite readers to submit letters commenting on the contents of articles that appear in the Journal. Also we...
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