Acute occlusion after a successful angioplasty is a severe complication that has been reported in 2-12% of patients. Therefore, to determine whether there was a relation between the dosage of heparin and the presence of mural thrombosis, we studied in a pig model the relation between the dosage of heparin and acute platelet-thrombus deposition on the site of arterial injury. We retrospectively analyzed the effect of three heparin regimens on platelet deposition in 32 normal pigs (mean weight, 32.7 kg) that underwent bilateral carotid angioplasty and were sacrificed 90 ± 26 minutes later. Pigs in protocol 1 (n = 7) received an intravenous bolus injection of 4,000 units heparin 10 minutes before angioplasty. Pigs in protocol 2 (n = 11) received two bolus injections of 4,000 units heparin 40 minutes apart; the angioplasty was performed immediately after the second bolus. Pigs in protocol 3 (n = 14) had an initial 4,000-unit bolus injection of heparin followed immediately by an infusion of 4,000 units/hr; angioplasty was performed 20 minutes after starting the infusion. 111In-labeled platelet deposition on deeply injured (torn into the media) arterial segments were 86.3 ± 68, 56.2 ± 56.9, and 37.7 ± 37.7 x 106/cm2 for protocols 1, 2, and 3, respectively. A regression analysis showed an inverse relation between the log of platelet deposition and heparin units per kilogram per minute in arterial segments with deep injury (r = -0.70, p = 0.0002) for the whole group as well as for each protocol (protocol 1: r = -0.80, p = 0.11; protocol 2: r = -0.80, p = 0.008; and protocol 3: r = -0.90, p = 0.008). Animals in protocol 2 had the lowest platelet deposition when heparin units per kilogram per minute was adjusted for each protocol. Platelet deposition in segments with subendothelial injury was very low (<10 x 106/cm2) and independent of the dosage of heparin. Macroscopic thrombus was present in all arterial segments (100%) with deep injury in those animals that received less than 3.1 heparin units/kg/min, whereas it was present in only 25% of arteries from pigs that had 3.1 or more heparin units/kg/min (p < 0.001). No thrombus was observed in segments with subendothelial injury. This study indicates that acute therapy with adequate dosages of heparin can significantly reduce thrombosis after arterial angioplasty in the carotid artery in pigs.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)