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Query: UMLS:C0151814 (coronary occlusion)
 3,687 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In 14 dogs the effects on regional tension (Walton-Brodie gauges) and length (mercury-in-silastic) following 50% reduction (52.9 +/- 2.1) in coronary flow for two hours and reperfusion afterwards for one hour were addressed. Within five minutes of partial coronary occlusion, ejection tension in the ischemic zone decreased to 36.3 +/- 7.2% (P less than 0.001) and total tension to 64.4 +/- 5.7% of control (P less than 0.001) while phasic segment length increased to 165.2 +/- 16.3% control. No further significant changes in regional tension or length were observed throughout the two hour period of partial occlusion. Ejection tension remained positive and segment length maintained systolic shortening during the ejection phase throughout the period of occlusion. Following reperfusion, ejection tension in the ischemic zone increased from 35.1 +/- 5.9 to 87.0 +/- 22.0% (P less than 0.05) and total tension increased from 56.6 +/- 5.4 to 70.2 +/- 7.2% (P less than 0.02) while segment length decreased from 149.3 +/- 6.5 to 105.7 +/- 5.7% (P less than 0.001) within five to 15 min of reperfusion. The improvement in both regional tension development and segment length shortening was maintained throughout the one hour period of reperfusion. No significant changes were seen in the nonischemic zone. The present experimental study suggests that partial coronary occlusion producing a 50% reduction in coronary blood flow results in regional contractile changes. These changes are reversible at least twice as long as those following complete occlusion.
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PMID:Effects of reperfusion on the regional contraction of ischemic and nonischemic myocardium following partial coronary obstruction. 61 97

Controversy has existed concerning the value of nitroglycerin therapy in acute myocardial infarction. With use of Walton-Brodie strain gauge arches and mercury-in-Silastic segment length gauges, the effects of nitroglycerin (30 mug/kg intravenously) were studied on local tension and length characteristics of the ischemic, border and nonischemic zones of the left ventricle in 10 open chest dogs. In the nonischemic zone total tension increased to 144.8 +/- 13.6 (mean +/- standard error of the mean) percent (P less than 0.005) of control levels, and segment length decreased to 79.4 +/- 4.4 percent (P less than 0.01) with infusion of nitroglycerin 15 to 30 minutes after coronary ligation. Changes were similar in the groups given nitroglycerin 45 to 60 minutes and 2 to 3 hours after ligation. The border zone exhibited an increase in total tension to 132.3 +/- 8.4 percent (P less than 0.005) of control level and a decrease in segment length to 79.0 +/- 2.4 percent (P less than 0.001) in the 15 to 30 minute group. In the 45 to 60 minute group, tension increased to 117.9 +/- 4.8 percent (P less than 0.005), whereas length decreased to 86.8 +/- 1.4 percent (P less than 0.001); and in the 2 to 3 hour group tension increased to 124.9 +/- 6.0 percent (P less than 0.005), and length decreased to 91.9 +/- 3.5 percent (P less than 0.001). The decrease in magnitude of responsiveness in the 45 to 60 minute and 2 to 3 hour postligation groups compared with the 15 to 30 minute postligation group was highly significant (P less than 0.005). The central ischemic zone showed no significant change in tension or length in any group. Maximal response to nitroglycerin administration in both tension and length parameters was observed within 30 to 60 seconds and was concomitant with a decrease in systolic pressure to 73.3 +/- 1.9 percent (P less than 0.001) and an increase in heart rate to 107.2 +/- 1.0 percent. Nitroglycerin improves the contractile performance of the nonischemic and border zones after coronary occlusion without affecting the central ischemic zone. However, the border zone exhibits a progressive decrease in contractile response as a function of time. These data suggest that nitroglycerin has the overall effect of functionally reducing the extent of the ischemic area and strongly supports its potential clinical usefulness in acute myocardial infarction.
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PMID:Nitroglycerin in experimental myocardial infarction. Effects on regional left ventricular length and tension. 81 Nov 6

The effects of digoxin priming dose of 0.04 mg/kg body weight followed by infusion of 0.02 mg/kg per min) on local tension and length characteristics of the nonischemic, border and ischemic left ventricular zones were studied in 30 dogs using Walton-Brodie strain gauge arches and mercury-in-Silastic segment length gauges. Total tension in the nonischemic zone increased to 130.9 plus or minus 5.3 percent (P smaller than 0.001) of the control level in association with parallel changes in preejection and ejection tension and rate of rise of tension when infusion of digoxin was instituted 15 to 30 minutes after ligation. Consistent increases in tension variables were noticed when infusion of digitalis was initiated 45 to 60 minutes or 2 to 3 hours after ligation. Segment length remained unchanged. In the border zone, total tension decreased to 68.9 plus or minus 5.9 percent (P smaller than 0.01) after infusion of digitalis. When infusion of digitalis was instituted 45 to 60 minutes or 2 to 3 hours after occlusion, similar increases in total tension and other tension variables were seen. Segment length again showed no significant changes. There was an increase in total tension in 5 of the 12 ischemic zones studied when digitalis was infused 15 to 30 minutes after coronary arterial ligation, whereas a consistent (3 to 5 percent) decrease in tension was observed when infusion of digitalis was instituted 45 to 60 minutes and 2 to 3 hours after coronary occlusion. There was no increase in segment length. In summary, digitalis uniformly increased contraction of the nonischemic and border zones after coronary arterial ligation, but the effects on contraction and aneurysmal bulging in the ischemic zone were minimal.
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PMID:Digitalis in experimental acute myocardial infarction. Differential effects on contractile performance of ischemic, border and nonischemic ventricular zones in the dog. 113 Feb 89

The performance characteristics of both ischemic and "adjacent" and "remote" nonischemic myocardium were studied in open chest dogs by three mercury-in-Silastic length gauges sutured to the anterior surface of the left ventricle before and after occlusion of the distal left anterior descending coronary artery. The adjacent gauge was separated from the ischemic segment by one large nonoccluded diagonal branch of the left anterior descending artery. Remote myocardium was separated from the ischemic area by two such branches. At the time of occlusion epicardial S-T segment elevation appeared in the ischemic region but not in the adjacent or remote regions. Immediately after occlusion, typical changes of ischemic dysfunction appeared. Late systolic lengthening, depression of systolic shortening and increased diastolic compliance occurred consistently and simultaneously in ischemic and adjacent regions and inconsistently in the remote region. Five minutes after occlusion, fiber shortening was depressed to 21, 58 and 67 percent of control values in ischemic, adjacent and remote regions, respectively. Heart rate did not change, and mean arterial pressure decreased slightly. These changes persisted over time. In 11 of these dogs, end-diastolic pressure was maintained constant 20 minutes after occlusion. Systolic shortening was depressed to 40 and 74 percent of control values in the ischemic and adjacent regions, respectively. In six dogs, end-diastolic pressure was varied form 5 to 20 mm Hg by rapid volume loading during the control state and 30 minutes after occlusion. Systolic shortening in ischemic, adjacent and remote regions was depressed to 20, 40 and 65 percent of control values, respectively. The severity of all functional alterations after coronary occlusion was directly related to proximity to the ischemic region. These results indicate that depression of left ventricular function after coronary occlusion may be partially related to previously unrecognized depression of function in apparently "nonischemic" myocardium.
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PMID:Functional abnormalities in nonoccluded regions of myocardium after experimental coronary occlusion. 125 69

To study the effects of nitroprusside infusion on the regional contractile performance of the left ventricle after coronary occlusion, local tension and segment length of the ischemic, border and nonischemic zones were studied using Walton-Brodie strain gauge arches and mercury-in-Silastic tubing segment length gauges in open chest dogs. The effect of this intervention on the time period for functional reversibility of the affected areas after revascularization was also examined. Fifteen minutes after occlusion of the left anterior descending coronary artery, nitroprusside (4 to 11 mug/kg per min) was infused to keep systolic pressure 20 to 25% below control levels for 2 hours after occlusion and then 1 hour after reperfusion. The ischemic zone showed no change in either tension or length although there was a gradual continuing decrease in tension. However, in the border zone total tension which had decreased to 81.4 +/- 9.6 (standard error of the mean) percent of control level 15 minutes after coronary occlusion, increased to 87.5 +/- 11.3% immediately after nitroprusside infusion and continued at that level for 2 hours. Preejection tension rate of tension rise and ejection tension demonstrated parallel increases. Segment length, which had increased to 144.1 +/- 4.5% of control level after coronary occlusion, declined to 115 +/- 10.7% (P less than 0.02) immediately after the onset of infusion. The nonischemic zone showed a sustained increase in all tension variables (P less than 0.01) and a decrease in segment length during the period of nitroprusside infusion with a return to control value after discontinuation of the infusion. The immediate deterioration in tension in the ischemic zone caused by reperfusion after 2 hours of occlusion was prevented by nitroprusside. The border zone continued to maintain improved tension after reperfusion but exhibited an immediate decrease from 84.1 +/- 7.8% to 69.1 +/- 11.7% (P less than 0.05) after discontinuation of nitroprusside. In summary, nitroprusside infusion provides a sustained increase in tension and decrease in length of the border and the nonischemic zones after acute coronary occlusion whereas the ischemic zone remains unaffected. Although administration of nitroprusside fails to prolong the time period for functional reversibility of the affected zones with reperfusion, it appears to prevent further deterioration.
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PMID:Effect of nitroprusside on local contractile performance after coronary ligation and reperfusion. 125 91

The mechanical behavior of ischemic myocardium was studied in anesthetized open chest dogs. In each animal, a small well localized myocardial infarction was produced by ligation of a single ventricular branch of the left circumflex coronary artery. Serial in situ measurements of segment length were made by mercury-in-Silastic gauges sutured directly to the left ventricular surface. After coronary ligation, systolic aneurysmal bulging of the ischemic segment was uniformly noted. This was quantified as follows: normalized segment length change in this region, expressed in muscle lengths (where muscle lengths = phasic segment length amplitude/end-diastolic segment length), immediately increased from 0.06 +/- 0.01 (standard error of the mean) to 0.10 +/- 0.02 muscle lengths (+67 percent, P less than 0.02). Over a 6 hour period, muscle lengths progressively declined to near control values, but retained an aneurysmal contour. End-diastolic segment length increased 5 percent above control values after coronary occlusion and remained fixed at this level for 6 hours. In contrast, noninfarcted myocardium exhibited no significant changes in muscle length or end-diastolic segment length. These studies demonstrate that the degree of systolic aneurysmal bulging in infarcted myocardium, although initially great, resolves within 6 hours but retains an aneurysmal contour. These findings are consistent with either partial return of contractility or diminished local compliance, but persistence of an aneurysmal shape favors the latter mechanism. The fixed increase in end-diastolic segment length suggests that "stress-relaxation" takes place in the infarcted region. It is possible that diminished compliance in zones of infarction, previously noted after several days, begins within a few hours after the onset of ischemia.
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PMID:Experimental myocardial infarction: XII. Dynamic changes in segmental mechanical behavior of infarcted and non-infarcted myocardium. 126 50

Regional function parameters under myocardial ischemia are frequently clearly changed when the parameters as the stroke volume, cardiac output, ejection fraction and the like are still unchanged by a compensation mechanism. Length changes can be measured regionally and phasically by means of a mercury wire strain gauge. The active shortening during the ejection time in relation to the total length change in this region is a possibility for the registration of the relative systolic shortening (delta LS%). Changes will be quantified still clearer and earlier if in the x-y display a vector representation of the regional displacements with the pressure in the left ventricle takes place. The plane of this vector decreased already a few seconds after the coronary occlusion. This is therefore a special early change in ischemia. The important for the estimation of therapeutic measures and other indirect measuring methods is accentuated.
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PMID:[Evaluation of regional heart function by means of local changes in pressure and direction in the vector cardiogram]. 721 Jul 62