Fig. 1.

Human saphenous vein grafts with blue markings displayed impaired contractile responses. Remnant saphenous vein from patients undergoing coronary artery bypass or peripheral vascular revascularization surgery were collected (n = 38). Rings from each vein were suspended in a muscle bath, contracted with 110 mM KCl (A), 10⁻⁶ M norepinephrine (B), force was measured, and converted to stress (10⁵ N/m²). Unmarked (n = 16) had no visible sign of markers when collected; marked (n =22) had visible sign of marking. The error bars show the standard error of the mean. * P < 0.0001.