SUMMARY The effect of sublingual or intracoronary nitroglycerin (NTG) on luminal caliber in normal and diseased portions of epicardial coronary arteries was determined in 85 lesions from 57 typical patients with ischemic heart disease. Measurements were made from coronary angiograms, using a computer-assisted method and a carefully blinded protocol for analysis of the pre-and post-NTG angiograms. Luminal area in the "normal" portion of the diseased segment and at its maximum constriction and an estimate of flow resistance in the stenosis were computed. Luminal area increased 1.27 mm2 (p < 0.001) in the "normal" regions, an average increase of 18% over the control area. Dilation with NTG depended strongly on vessel size; area increased 35% in normal vessels of 1.6-2.3 mm luminal diameter and only 9% in vessels 4.0-5.0 mm in diameter. Lesions were grouped into four levels of severity by percent stenosis. Minimum luminal area increased 0.35 mm2 (p < 0.01) at the narrowest point in moderate lesions, a 22% area increase, and 0.14 mm2 (p < 0.001) in severe lesions, a 36% area increase. Stenosis dilation resulted in an average 25% reduction (p < 0.01) in estimated stenosis flow resistance in moderate lesions and a 38% reduction (p < 0.001) in severe lesions. A statistically significant resistance reduction of greater than 20% occurred in 15 of 20 severe stenoses; only two of 20 showed no measurable dilation. We reviewed recent literature on hemodynamic responses to NTG and determined that changes of this magnitude are among the largest reported. We conclude that vasodilation of epicardial coronary stenoses is usually a major component of the beneficial response to NTG.We support that conclusion by demonstrating a striking improvement in ischemic left ventricular compliance abnormalities after low-dose intracoronary NTG. NITROGLYCERIN (NTG) affords dramatic relief of angina pectoris in patients with coronary artery disease; yet its mechanisms of action are complex and, in certain respects, controversial. NTG is said to reduce the myocardial oxygen requirement by diminishing systolic wall tension through reduced systemic pressure (afterload) and reduced left ventricular (LV) diastolic pressure and cavity size (preload

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Background/Objectives: Slow-flow vascular malformations are abnormal vessels that can lead to activation and consumption of coagulation factors and thrombosis, known as localized intravascular coagulopathy (LIC). Most clinical and research evidence of vascular malformation hemostasis relies on conventional coagulation studies, which may not provide a complete picture. Thromboelastograpy (TEG) is a tool that can provide real-time assessment of a patient's coagulation dynamics, and may allow for a more individualized treatment approach. We hypothesized that patients with slowflow vascular malformations will have changes in TEG parameters peri-procedure that will help predict blood product or medication administration. Design/Methods: Institutional Review Board approved prospective study of patients with slow-flow vascular malformations undergoing a sedated, minor procedure. TEG and conventional coagulation studies were obtained preprocedure, 15 min, and when possible, at 30 min after the start of the procedure. Results: Twenty-five patients were enrolled. Median age was 15 years (range 3-47 years). Procedures included laser and/or sclerotherapy. There were no changes in TEG parameters from baseline to 15 min or 30 min. The following decreased from baseline to 15 min: fibrinogen 313 to 287 mg/dL (P = .001), D-dimer 1.3 to 1.1 mg/L (P = .02), hemoglobin 12.8 to 11.8 g/dL (P = .001), and platelet count 272 000 to 256 000 (P = .006). No patient had a bleeding/thrombotic complication during or within 1 week postprocedure. Conclusion: We saw no change in TEG parameters or bleeding or clotting complications despite significant numerical changes in conventional coagulation profiles, suggesting that conventional studies may not be as useful in determining risks of bleeding or thrombotic complications peri-procedure for minor procedures.

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