Elsevier

American Heart Journal

Volume 135, Issue 2, February 1998, Pages 323-328
American Heart Journal

Thrombolysis in Myocardial Infarction frame count in saphenous vein grafts,☆☆,

https://doi.org/10.1016/S0002-8703(98)70100-0Get rights and content

Abstract

Background Although the Thrombolysis in Myocardial Infarction flow grade system is a widely used index of coronary blood flow, it has important limitations. We recently described a new continuous measure of blood flow in native coronary arteries, the Thrombolysis in Myocardial Infarction frame count (TFC), and sought to extend this method to coronary artery bypass grafts. Methods We retrospectively analyzed cinefilms of patients' status after coronary artery bypass grafting, excluding patients with recent myocardial infarction and grafts with stenoses in the graft or native vessel. We counted the cineframes required for dye to travel from the ostium of the graft to the graft anastomotic site (TFCg) and to a standardized distal coronary landmark (TFC). Results For all vein grafts combined, TFCg was 19.2 ± 5.7 frames (mean ± SD, n = 93) and the TFC was 33.9 ± 8.0 frames (n = 67). The upper limits for “normal” flow, calculated from the 95% confidence intervals, were 31 frames for TFCg and 50 frames for TFC. Conclusions The Thrombolysis in Myocardial Infarction frame counting method has now been extended to normal saphenous vein grafts, and normal reference values are provided. (Am Heart J 1998;135:323-8.)

Section snippets

Methods

All analyzable cinefilms of patients who underwent cardiac catheterization at the West Roxbury Veterans Affairs Medical Center between January 1990 and September 1996 were examined to determine the range of values for the TFC in saphenous vein bypass grafts that were normal on angiography. Patients were excluded if they had sustained an acute myocardial infarction within 1 week of their catheterization or if any stenosis was present in either the saphenous vein graft or the native vessel. No

Results

A total of 97 injections of grafts in 83 patients met the inclusion criteria for analysis. For all SVGs (Table I) the mean TFCg was 19.2 ± 5.7 frames (n = 93), the mean TFCn was 14.0 ± 6.1 frames (n = 63), and the mean TFC was 33.8 ± 7.9 frames (n = 67). The 95% confidence interval (±1.96 × SD) for all vein grafts yielded an upper limit of “normal flow” of 31 frames for TFCg, 26 frames for TFCn, and 50 frames for TFC. In vein grafts to the LAD, TFCg was 18.4 ± 5.6 (n = 17), TFCn was 13.1 ± 4.8 (

Potential pitfalls in the conventional TIMI flow grade system

Although the conventional TIMI flow grading system1 has been widely used to compare the efficacy of thrombolytic agents and to risk stratify patients, it has several important limitations. This classification scheme was originally designed to categorize flow in native coronary arteries. Little data exist describing the visual assessment of normal flow in saphenous vein bypass grafts, which often have a larger diameter than native vessels, which may alter the normal velocity of dye. Another

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From the Cardiovascular Division of the Department of Medicine, the Brigham and Women's Hospital and West Roxbury Veterans Affairs Medical Center, Harvard Medical School.

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Reprint requests: C. Michael Gibson, MS, MD, Chief Of Cardiology, West Roxbury Veteran's Affairs Medical Center, 1400 VFW Pkwy., West Roxbury, MA 02132.

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