Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0151744 (myocardial ischemia)
 31,282 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To study the mechanisms of myocardial ischemia during isometric exercise, handgrip was sustained, for 4.5 min at 25% of maximum by 11 patients with at least one significant coronary stenosis each, during cardiac catheterization. After recovery, the handgrip that was repeated with simultaneous infusion of nitroglycerin (50 micrograms over 4 min) directly into the diseased vessel. The cardiovascular response was assessed by hemodynamic and by computer-assisted measurements of stenosis. During the first handgrip test pulmonary capillary wedge pressure rose 56% (15 to 23 mm Hg; p less than .001), the heart rate-systolic pressure product rose 33% (p less than .01), and the diseased epicardial arteries constricted. Luminal area in the stenotic segment was reduced by 35% (p less than .01), resulting in a 243% increase in estimated stenotic flow resistance (30 to 103 mm Hg/ml/sec; p less than .001). During handgrip with intracoronary nitroglycerin, the pressure-rate product again increased 33%, but relative to resting control, capillary wedge pressure fell 4 mm Hg in association with a 32% increase in luminal area of the stenosis and a 28% reduction in flow resistance (all significantly different from the response to handgrip alone: p less than .001, .01, and .005, respectively). Thus, coronary vasoconstriction, not increased pressure-rate product, is the dominant mechanism for ischemic left ventricular dysfunction during isometric exercise in patients with significant coronary stenoses.
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PMID:Reflex constriction of significant coronary stenosis as a mechanism contributing to ischemic left ventricular dysfunction during isometric exercise. 642 17

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 less than 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 less than 0.01) at the narrowest point in moderate lesions, a 22% area increase, and 0.14 mm2 (p less than 0.001) in severe lesions, a 36% area increase. Stenosis dilation resulted in an average 25% reduction (p less than 0.01) in estimated stenosis flow resistance in moderate lesions and a 38% reduction (p less than 0.001) in severe lesions. A statistically significant resistance reduction of greater than 20% occurred in 15 to 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 stenosis 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.
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PMID:The mechanisms of nitroglycerin action: stenosis vasodilatation as a major component of the drug response. 679 31

It is not known whether the individual lesions that constitute tandem lesions of the coronary artery are developmentally or rheologically related. Luminal changes and their rheological significance were examined by percutaneous angioscopy in 44 tandem lesions of 21 patients with ischemic heart disease. Angioscopically, individual narrowing of angiographically documented tandem lesions appeared only as a tangentially expressed prominent portion of an atherosclerotic spiral fold. The directions of the fold were counterclockwise in the proximal to middle segments and clockwise in the distal segment of the right coronary artery, clockwise in the proximal to middle segments and counterclockwise in the distal segment of the left anterior descending artery, and counterclockwise in the proximal to middle segments of the left circumflex artery. The bloodstream always ran along the spiral folds in the tandem lesions. The results suggest that angiographically documented tandem coronary lesions are merely a tangential expression of atherosclerotic spiral folds and that they may act to prevent blood turbulence by generating a spiral laminal flow.
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PMID:Rheological significance of tandem lesions of the coronary artery. 778 64