Effect of Glucocorticoids on Ultrastructure of Myocardial Muscle in the Course of Experimentally Induced Acute Myocardial Ischemia

The search for effective methods of myocardial cytoprotection against ischemia is the most significant issue in modern cardiology and cardiac surgery. Glucocorticoids are deemed very strong modulators of inflammatory response and thus can potentially protect heart muscle from postreperfusion injury and myocardial ischemia during cardiac surgery. Ultrastructural examination of the left ventricle heart samples revealed that the intravenous application of dexamethasone and hydrocortisone proved to exert cytoprotective effect on cardiomyocytes during experimentally induced acute ischemia in rats.

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Celebrating the 100th Birthday of the Electrocardiogram: Lessons Learned From Research in Cardiac Monitoring

American Journal of Critical Care ◽

10.4037/ajcc2002.11.4.378 ◽

2002 ◽

Vol 11 (4) ◽

pp. 378-386 ◽

Cited By ~ 14

Author(s):

Barbara J. Drew

Keyword(s):

Critical Care ◽

Myocardial Ischemia ◽

Current Trend ◽

Torsade De Pointes ◽

Acute Myocardial Ischemia ◽

Lessons Learned ◽

Cardiac Monitoring ◽

Acute Ischemia ◽

Antiarrhythmic Agents ◽

St Segment

The electrocardiogram continues to be the gold standard for the diagnosis of cardiac arrhythmias and acute myocardial ischemia. The treatment of arrhythmias in critical care units has become less aggressive during the past decade because research indicates that antiarrhythmic agents can be proarrhythmic, causing malignant ventricular arrhythmias such as torsade de pointes. However, during the same period, the treatment of acute myocardial ischemia has become more aggressive, with the goal of preventing or interrupting myocardial infarction by using new antithrombotic and antiplatelet agents and percutaneous coronary interventions. For this reason, critical care nurses should learn how to use ST-segment monitoring to detect acute ischemia, which is often asymptomatic, in patients with acute coronary syndromes. Because the electrocardiographic lead must be facing the localized ischemic zone of the heart to depict the telltale signs of ST-segment deviation, the challenge is to find ways to monitor patients continuously for ischemia without using an excessive number of electrodes and lead wires. The current trend is to use reduced lead set configurations in which 5 or 6 electrodes, placed at convenient places on the chest, are used to construct a full 12-lead electrocardiogram. Nurse scientists at the University of California, San Francisco, School of Nursing are at the forefront in developing and assessing the diagnostic accuracy of these reduced lead set electrocardiograms.

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Vagal reflexes and survival during acute myocardial ischemia in conscious dogs with healed myocardial infarction

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1991.261.1.h63 ◽

1991 ◽

Vol 261 (1) ◽

pp. H63-H69 ◽

Cited By ~ 15

Author(s):

G. M. De Ferrari ◽

E. Vanoli ◽

M. Stramba-Badiale ◽

S. S. Hull ◽

R. D. Foreman ◽

...

Keyword(s):

Myocardial Infarction ◽

Heart Rate ◽

Coronary Artery ◽

Ventricular Fibrillation ◽

Myocardial Ischemia ◽

Coronary Artery Occlusion ◽

Artery Occlusion ◽

Acute Myocardial Ischemia ◽

Acute Ischemia ◽

Control Test

The role of vagal tone and reflexes in the genesis of life-threatening arrhythmias was investigated in a clinically relevant animal model for sudden cardiac death. Forty-five dogs with a healed anterior myocardial infarction in which transient myocardial ischemia during exercise did not induce malignant arrhythmias were utilized for the study. They underwent a further exercise and ischemia test in which atropine (75 micrograms/kg) was injected before coronary artery occlusion. Novel occurrence of ventricular arrhythmia, or worsening of the type of arrhythmia present in the control test, occurred in 23 of 45 dogs (51%) and ventricular fibrillation occurred in 11 of 45 (24%, P = 0.001). Analysis of heart rate response to acute ischemia in the control test indicates that these 11 animals had powerful vagal reflexes during coronary artery occlusion, compared with the 34 survivors (-32 +/- 35 vs. +2 +/- 27 beats/min, P = 0.003). This study indicates that approximately 75% of animals resistant to ventricular fibrillation are characterized by weak sympathetic reflexes in response to acute myocardial ischemia. In the remaining 25% powerful vagal reflexes counteract concomitant reflex sympathetic hyperactivity, decrease heart rate, and are essential for survival.

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Regional wall stiffness during acute myocardial ischemia in the canine left ventricle

The American Journal of Cardiology ◽

10.1016/s0002-9149(79)80174-5 ◽

1979 ◽

Vol 43 (2) ◽

pp. 378

Keyword(s):

Myocardial Ischemia ◽

Left Ventricle ◽

Acute Myocardial Ischemia ◽

Regional Wall ◽

Wall Stiffness

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Detection of regional temporal abnormalities in left ventricular function during acute myocardial ischemia

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2001.280.4.h1770 ◽

2001 ◽

Vol 280 (4) ◽

pp. H1770-H1781 ◽

Cited By ~ 38

Author(s):

Victor Mor-Avi ◽

Keith A. Collins ◽

Claudia E. Korcarz ◽

Milind Shah ◽

Kirk T. Spencer ◽

...

Keyword(s):

Myocardial Ischemia ◽

Wall Motion ◽

Left Ventricular ◽

Acute Myocardial Ischemia ◽

Acute Ischemia ◽

Left Ventricular Performance ◽

Ventricular Performance ◽

Early Markers ◽

Custom Software ◽

Echocardiographic Images

Echocardiographic diagnosis of myocardial ischemia is based on visualizing hypokinesis, which occurs late in the ischemic cascade. We hypothesized that temporal changes in endocardial motion may constitute sensitive early markers of ischemia. Two protocols were performed in 19 anesthetized pigs. Protocol 1 included 54 intracoronary balloon occlusions. Transthoracic images were acquired at baseline and every 15 s during 5 min of occlusion and reperfusion. In protocol 2, ischemia was induced in 12 animals by use of graded dobutamine infusion, after creating significant partial occlusions without a resting wall motion abnormality. Systolic and diastolic endocardial motion was color encoded using color kinesis and analyzed using custom software. All ischemic episodes caused detectable and reversible changes. The earliest sign of ischemia was tardokinesis in 31/54 occlusions, whereas hypokinesis appeared first in 23/54 cases. Dobutamine-induced ischemia caused tardokinesis first in 9/12 and hypokinesis in 3/12 animals. Reversible ischemic changes in regional left ventricular performance can be objectively detected using analysis of echocardiographic images and will likely improve the early noninvasive diagnosis of acute ischemia.

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Ultrasound Characterization of Acute Myocardial Ischemia by Quantitative Texture Analysis

Ultrasonic Imaging ◽

10.1177/016173468600800401 ◽

1986 ◽

Vol 8 (4) ◽

pp. 227-240 ◽

Cited By ~ 20

Author(s):

David D. McPherson ◽

Philip E. Aylward ◽

Boyd M. Knosp ◽

Judy A. Bean ◽

Richard E. Kerber ◽

...

Keyword(s):

Myocardial Ischemia ◽

Texture Analysis ◽

False Positive ◽

Image Data ◽

Axial Direction ◽

Acute Myocardial Ischemia ◽

Depth Of Field ◽

Acute Ischemia ◽

Azimuthal Direction ◽

Ischemic Region

In this study we tested the efficacy of quantitative texture analysis in the identification of acute myocardial ischemia using an ultrasound data acquisition system that digitizes and stores echocardiographic data in polar format. In nine closed-chest dogs, data were acquired before and after coronary occlusion using a 2.4 MHz echocardiographic system. Regions of interest were analyzed at end-diastole and end-systole from the ischemic area and normal area at the same depth of field. Ultrasound data were evaluated using previously reported quantitative gray level texture measures. After occlusion, texture changes indicative of ischemia were found in systolic images. The directional component of the data analysis was important; analysis in the azimuthal direction was more accurate than in the axial direction. Six texture measures exhibited significant changes in the ischemic region from control to occlusion when analyzing data in the azimuthal direction. One false positive result occurred (significant texture change in the normal region from control to occlusion) in the azimuthal direction. Several false positive alterations in the normal regions from control to occlusion were found when the texture was evaluated in the axial direction. For accurate assessment of ischemic changes, preocclusion image data were required. We conclude that quantitative echocardiographic texture analysis using polar format data can identify subtle changes in myocardial texture such as that due to acute ischemia, using data acquired through the Chest Wall.

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Heparin from Intestine and Lung Source Administered in Large Dose to Dogs with Acute Myocardial Ischemia

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648674 ◽

1978 ◽

Vol 40 (02) ◽

pp. 407-417

Author(s):

Michael J Saliba ◽

Richard J Pavalec

Keyword(s):

Coronary Artery ◽

Myocardial Ischemia ◽

Adenosine Triphosphate ◽

Intestinal Mucosa ◽

Large Dose ◽

Acute Myocardial Ischemia ◽

Ischemic Myocardium ◽

Atp Levels ◽

Initial Control ◽

The Difference

SummaryIntestinal mucosa heparin (IMH) and beef lung heparin (BLH) were infused into dogs subjected to myocardial ischemia by intermittent coronary artery occlusions. The IMH was from a mixture of beef, sheep, and pig intestinal mucosa. Initial control occlusion and recovery was followed by a second occlusion with 60,000 units of IMH or BLH added. Electrocardiographic S-T segment elevations (ST) were measured acutely. There were no significant differences in ST in non-ischemic myocardium before occlusions or with occlusions. In ischemic myocardium, IMH significantly lowered control ST 84% in amount (t = 6.1 p <0.00005), and 76% in number (t = 11.6 p <0.00001). BLH lowered control ST a significant, lesser, 36% in amount (t = 3.6 p <0.008), and 35% in number (t = 3.2 p <0.01). The difference between IMH and BLH in ischemic myocardium was a significant 48% in amount (t = 4.0 p <0.0007), and 41% in number (t = 2.0 p <0.06). Myocardial adenosine triphosphate (ATP) levels were assayed after 90 min. ATP levels were 31% higher in both ischemic and non-ischemic myocardium in IMH-treated dogs than in BLH- treated. It was concluded that IMH and BLH are functionally different, and IMH was significantly more effective.

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