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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of varying perfusion pressure on the adequacy and distribution of coronary flow was studied in normothermic and hypothermic beating hearts. At 37 degrees C., lowering perfusion pressure from 100 to 50 mm. Hg did not change oxygen uptake or total or regional coronary flow or cause biochemical or histochemical ischemia. Vasodilator reserve capacity, however, was expended in order to maintain adequate subendocardial perfusion. At 28 degrees C., myocardial oxygen uptake per minute fell but oxygen consumption per beat rose significantly. Reduction of perfusion pressure to 50 mm. Hg caused a 44 percent (p less than 0.01) reduction in subendocardial flow and resulted in redistribution of flow away from the subendocardium (endocardial/epicardial flow ratio fell from 1.25 to 1.0). Ischemia was evident from intracavitary electrocardiogram, abnormal glycolysis, and histochemical staining. These studies show that during normothermia the coronary arteries dilate to provide adequate coronary flow when perfusion pressure is reduced. In contrast, compensatory vasodilatation is inadequate in hypothermic hearts and ischemia occurs at low perfusion pressures.
J Thorac Cardiovasc Surg 1977 Jan
PMID:Studies of the effects of hypothermia on regional myocardial blood flow and metabolsim during cardiopulmonary bypass. II. Ischemia during moderate hypothermia in continually perfused beating hearts. 83 Oct 13

This study compares (1) the effects of slowing heart rate by topical hypothermia in hearts perfused at 37 degrees C. with bradycardia produced by perfusion hypothermia (28 degrees C.) and (2) the consequences of counteracting the bardycardic effects of perfusion hypothermia by atrial pacing. Topical atrial hypothermia (myocardial temperature 37 degrees C.) produced a level of bradycardia comparable to perfusion hypothermia (82 vs. 71 beats per minute), but reduced myocardial oxygen requirements 25 per cent more than perfusion with 28 degrees C. blood. Myocardial oxygen uptake per beat did not change with topical atrial hypothermia but increased 40 per cent with perfusion hypothermia. Counteracting the bradycardic effects of perfusion hypothermia with atrial pacing (to 130 beats per minute) reduced subendocardial flow 25 per cent, caused a redistribution of flow away from the subendocardium, and produced evidence of ischemia on the intracavitary electrocardiogram. This study shows that (1) topical atrial hypothermia with systemic normothermia reduced myocardial oxygen demands as effectively as perfusion hypothermia and (2) subendocardial ischemia develops in beating empty hearts when the expected bradycardia of hypothermia does not occur.
J Thorac Cardiovasc Surg 1977 Feb
PMID:Studies of the effects of hypothermia on regional myocardial blood flow and metabolism during cardiopulmonary bypass. IV. Topical atrial hypothermia in normothermic beating hearts. 83 58

A total of 204 patients, ages 3 months to 84 years, underwent open-heart surgery with the aid of cardiopulmonary bypass with moderate hypothermia. For protection of the myocardium, cardioplegia was induced by washing out the coronary arteries with an iced, buffered, isoosmolar, potassium-based infusate. After aortic cross-clamping, the aortic root or individual coronary arteries were perfused with 500 to 2,000 c.c. of an aqueous solution (at zero to 4 degrees C.) containing 20 mEq. of potassium. Periods of ischemic arrest as long as 208 minutes have been well tolerated, with only two of the eleven hospital deaths considered heart related. Defibrillation occurred spontaneously in 41 per cent and after one shock in 47 per cent of patient, without apparent correlation between duration of ischemia and restoration of effective rhythm.
J Thorac Cardiovasc Surg 1977 Mar
PMID:Myocardial protection with cold, ischemic, potassium-induced cardioplegia. 83 26

The effects of isoproterenol and dopamine on regional myocardial blood flow were studied in 10 open-chest dogs after acute stenosis of the proximal circumflex coronary artery. Blood flow was determined by the radioactive microsphere technique. Isoproterenol led to a homogenous increase in blood flow in the normal myocardium. In the myocardium with compromised coronary blood flow, isoproterenol led to a relative subendocardial ischemia. This occurred despite increased aortic flow and peak left ventricular dp/dt. Dopamine also increased aortic flow and peak left ventricular dp/dt, but it did not cause regional myocardial ischemia. The findings suggest that dopamine is the preferable inotropic agent in managing low cardiac output in patients with significant coronary artery disease.
J Thorac Cardiovasc Surg 1977 Mar
PMID:The effects of isoproterenol and dopamine on regional myocardial blood flow after stenosis of circumflex coronary artery. 83 34

The effect of a critical coronary artery stenosis on myocardial blood flow and metabolism in the fibrillating heart was assessed by placing 10 dogs on cardiopulmonary bypass, venting the ventricle, inducing ventricular fibrillation, and applying critical stenosis to the left anterior descending coronary artery (LAD). Endocardial and epicardial blood flows were measured by the radioactive microsphere technique prior to the application of the stenosis and after one hour and 2 hours of fibrillation. Intramyocardial oxygen tension (PO2) and carbon dioxide tension (PCO2) were continuously monitored in the LAD-supplied myocardium by a mass spectrometer probe inserted at midmyocardial depth. Selective arterial-coronary venous lactate differences were determined at control, one hour, and 2 hours. At the end of the 2 hour period, vital dye injection defined the distribution of the LAD. Endocardial flow to the myocardium of the stenosed LAD was reduced by 50 per cent after one hour and by 70 per cent after 2 hours (p less than 0.05). Epicardial flow fell 40 per cent after one hour and 50 per cent after 2 hours (p less than 0.05). Endocardial and epicardial flow in the distribution of the unstenosed circumflex coronary artery remained unchanged. Changes in myocardial PO2 and PCO2 in the LAD-supplied myocardium indicated the development of severe ischemia in all 10 dogs and suggested myocardial infarction in 5. There was a conversion from lactate extraction to lactate production during the 2 hour period of ventricular fibrillation. From this study, it is concluded that the myocardium distal to a critical stenosis suffers a progressive reduction in flow during ventricular fibrillation which does not occur in regions supplied by unstenosed coronary arteries. Thus prolonged fibrillation in the presence of a flow-limiting coronary stenosis may play a role in the pathogenesis of myocardial infarction during coronary bypass surgery.
J Thorac Cardiovasc Surg 1977 May
PMID:Myocardial ischemia during cardiopulmonary bypass. The hazards of ventricular fibrillation in the presence of a critical coronary stenosis. 85 Apr 34

During reperfusion, functional and metabolic recovery of the isolated working rat heart from one hour of ischemia was best in hearts selectively cooled at the onset of the ischemic interval by perfusion with 5 to 10 ml. of 10 degrees C. or 15 degrees C. Krebs-Henseleit buffer. Hearts similarly perfused at 4 degrees C., 20 degrees C. recovered significantly less well or not at all. Immediately after the hour of ischemia and prior to reperfusion, the absolute levels of glycogen and high-energy phosphates were best in the hearts perfused at 4 degrees C. However, metabolic function was best preserved in those perfused at 10 degrees C. and 15 degrees C., as evidenced by rapid recovery of high-energy phosphates and glycogen to control levels compared to metabolic deterioration in the 4 degrees C. group.
J Thorac Cardiovasc Surg 1977 May
PMID:Effect of perfusate temperature on myocardial protection from ischemia. 85 Apr 37

A number of cardioplegic and protective solutions have been described for the reduction of cellular damage during ischemic cardiac arrest. These solutions are designed to induce diastolic arrest rapidly and to combat the various deleterious effects of ischemia. The efficacy of three different infusates (Bretschneider, Kirsch and St. Thomas' Hospital) has been compared. The results indicate that, whereas some solutions are able to afford striking protection, others may be ineffective and may exacerbate damage. Until the mechanisms underlying ischemic damage and its prevention are understood, it would seem undesirable to advocate the use of solutions containing extremes of concentration or solutions devoid of ions normally found in the extracellular fluid.
J Thorac Cardiovasc Surg 1977 Jun
PMID:Myocardial protection during ischemic cardiac arrest. A possible hazard with calcium-free cardioplegic infusates. 85 52

Axillary-to-contralateral brachial artery by-pass was applied in two female patients affected by unilateral obstructive lesion of the subclavian artery with significant symptoms of arm ischemia. The result, at 10 and 12 months of follow-up, is good. The technique and its advantages are shortly outlined.
J Cardiovasc Surg (Torino)
PMID:Axillary-to-contralateral brachial artery by-pass in the treatment of arm ischaemia. 86 67

We compared moderate (29 degrees C.) and profound (5 degrees C.) (ice chips) cardiac hypothermia for myocardial preservation during aortic cross-clamping for 30 or 60 minutes in a canine right heart bypass preparation. Ventricular function deteriorated significantly at 29 degrees C. but not at 5 degrees C. Maximum dp/dt declined only after 60 minutes of ischemia at 29 degrees C., and Vmax decreased after one hour at either temperature. Lactate and pyruvate washout were greater after 29 degrees C., and pyruvate production persisted after 60 minutes of ischemia at 29 degrees C. Reactive hyperemia was greater after 30 minutes of ischemia at 29 degrees C. Reactive hyperemia was greater after 30 minutes of ischemia at 29 degrees C., and total coronary flow remained elevated after 60 minutes of ischemia at 29 degrees C. Coronary flow distribution was not altered by hypothermia. Ultrastructural changes were primarily time dependent and not temperature dependent. Ice-induced subepicardial injury was not evident in the ultrastructure or by flow distribution. Sixty minutes of profound topical cardiac hypothermia is moderately well tolerated by the canine heart, but functional and structural alterations are evident.
J Thorac Cardiovasc Surg 1977 Jun
PMID:Topical cardiac hypothermia for myocardial preservation. 87 Jul 64

A study of two-stage pulmonary autotransplantation was performed on 29 dogs; 12 dogs died after the first stage, which was always a right lung reimplantation, and 17 dogs underwent the second stage after varying intervals of time. In the group of six dogs operated upon with very short intervals between stages (2 to 8 days) there were no survivors. There were seven long-term survivors in the subgroup with an interval longer than 4 weeks, and they constitute the largest published series obtained with this particular procedure. The interval between operative stages was the only significant controlled variable, as only minor technical or operative differences were allowed to occur. Ischemia times of the lungs were usually quite short. The surviving animals were utilized for studies of the regeneration of the afferent pulmonary nerves (Hering-Breure reflex and effects of capsaicin) as permitted by a long follow-up period of up to 3 years.
J Thorac Cardiovasc Surg 1977 Aug
PMID:Two-stage bilateral lung reimplantation in the dog. 88 77


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