No abstract

Continuing investigations of vascular graft materials suggest that unacceptable graft complications continue and that the ideal graft material has not yet been found. We have developed and tested a biologic vascular graft material, small intestine submucosa (SIS), in normal dogs. This material, when used as an autograft, allograft, or xenograft has demonstrated biocompatibility and high patency rates in aorta, carotid and femoral arteries, and superior vena cava locations. The grafts are completely endothelialized at 28 days post-implantation. At 90 days, the grafts are histologically similar to normal arteries and veins and contain a smooth muscle media and a dense fibrous connective tissue adventitia. Follow-up periods of up to 5 years found no evidence of infection, intimal hyperplasia, or aneurysmal dilation. One infection-challenge study suggested that SIS may be infection resistant, possibly because of early capillary penetration of the SIS (2 to 4 days after implantation) and delivery of body defenses to the local site. We conclude that SIS is a suitable blood interface material and is worthy of continued investigation. It may serve as a structural framework for the application of tissue engineering technologies in the development of the elusive ideal vascular graft material.

Background Sympathetic nerve activity is important to cardiac arrhythmogenesis. Objectives (1) To develop a method for simultaneous noninvasive recording of skin sympathetic nerve activity (SKNA) and electrocardiogram (ECG) using conventional ECG electrodes. (2) This method (neuECG) can be used to adequately estimate the sympathetic tone. Methods We recorded neuECG signals from the skin in 56 human subjects. The signals were low pass filtered to show the ECG and high pass filtered to show nerve activity. Protocol (P)-1 included 12 healthy volunteers who underwent cold water pressor test (CPT) and Valsalva maneuver. P-2 included 19 inpatients with epilepsy but without known heart diseases monitored for 24 hours. P-3 included 22 patients admitted with electrical storm and monitored for 39.0±28.2 hours. P-4 included 3 patients who underwent bilateral stellate ganglion blockade with lidocaine injection. Results In patients without heart diseases, spontaneous nerve discharges were frequently observed at baseline and were associated with heart rate acceleration. The SKNA recorded from chest leads (V1–V6) during CPT and Valsalva maneuver (P-1) was invariably higher than during baseline and recovery periods (p<0.001). In P-2, the average SKNA correlated with the heart rate acceleration (r=0.73±0.14, p<0.05) and shortening of the QT interval (p<0.001). Among 146 spontaneous ventricular tachycardia episodes recorded in 9 patients of P-3, 106 episodes (73%) were preceded by SKNA within 30 s of onset. P4 showed that bilateral stellate ganglia blockade by lidocaine inhibited SKNA. Conclusions SKNA is detectable using conventional ECG electrodes in humans and may be useful in estimating the sympathetic tone.

Autogenous saphenous vein, human umbilical vein, modified bovine collagen, Dacron, and PTFE have been used as small-diameter arterial grafts with moderate success. We tested autogenous small intestine submucosa as a small-diameter arterial graft in both a carotid and femoral artery (mean ID 4.3 mm) of 18 dogs (total of 36 grafts). All dogs received aspirin and warfarin sodium for the first 8 weeks after surgery. Graft patency was evaluated by Doppler ultrasound techniques and angiography. Two grafts ruptured and 5 grafts occluded by 21 days after surgery. One graft became occluded at 14 weeks. Fifteen dogs were sacrificed at periodic intervals until 48 weeks after surgery. Patent grafts had no evidence of infection, propagating thrombus, or intimal hyperplasia. Graft aneurysmal dilation occurred in 4 grafts (11%). The grafts were composed of a dense organized collagenous connective tissue with no evidence of endothelial cell growth on the smooth luminal surface. Three dogs are alive at 76 to 82 weeks after surgery. Overall, graft patency was 75%. Graft patency after cessation of anticoagulation therapy was 92.3% (12 of 13 grafts). We conclude that autogenous small intestinal submucosa can be used as a small-diameter arterial graft in the dog and is worthy of further investigation.