Search PubMed⌕ Search

Biomedical subjects

K A Reimer

Publications and source records attributed to K A Reimer.

126 records · Page 7Linked to original sources
PubMed1976

Rheumatoid arthritis with rheumatoid heart disease and granulomatous aortitis.

Aortic insufficiency and aortitis are frequent complications of ankylosing spondylitis but are considered rare in rheumatoid arthritis. A 49-year-old woman with severe rheumatoid arthritis had the cardiovascular changes common to both diseases. At autopsy, the heart and aorta showed granulomatous ane fibrinous pericarditis and epicarditis, "core" granulomas in the aortic valve cusps and mitral valve leaflets, and coronary arteritis. These are considered to be classical changes of rheumatoid carditis. In addition, there were mesoaortitis with obliterative endarteritis of the vasa vasorum and fibrosis of the aortic cusps with separation of the commissures. These are considered to be changes of ankylosing spondylitis. This case, therefore, represents a mixed form of cardiovascular involvement within the spectrum of the rheumatoid diseases.

Aorta↗
PubMed1976

On the nature of protection by propranolol against myocardial necrosis after temporary coronary occlusion in dogs.

Propranolol has been shown to reduce the extent of necrosis that develops after temporary coronary occlusion in dogs. To determine whether this protective action was related to beta adrenergic blockade or to direct effects, necrosis was quantitated in the posterior papillary muscle 2 to 4 days after 40 minute periods of coronary occlusion in anesthetized open chest dogs. Groups of dogs either were untreated or were pretreated with doses of d,l-propranolol, 0.005 to 5 mg/kg body weight, or doses of d-propranolol 2.5 or 5 mg/kg. Necrosis was greatly reduced in dogs treated with 5 mg/kg of d, l-propranolol. This protective effect was significant but quantitatively less with 0.5 and 0.05 mg/kg of d, l-propranolol. A dose of 0.005 mg/kg d, l-propranolol and d-propranolol failed to alter myocardial necrosis significantly. The dose-related reduction of necrosis with d, l-propranolol correlated with a similar dose relation for beta adrenergic blockade and suggested that a protective effect was related to beta blockade. The reduction of necrosis with 0.05 and 0.5 mg/kg of d, l-propranolol (a level at which direct "membrane stabilizing" effects are insignificant) suggested that direct effects were not essential for protection. The negative results with d-propranolol further support our conclusion that propranolol reduces myocardial ischemic injury through beta adrenergic blockade rather than through direct myocardial actions.

Animals↗
PubMed1976

Distribution of coronary collateral flow in acute myocardial ischaemic injury: effect of propranolol.

The local distribution of coronary collateral flow was mapped using 8 mu tracer microspheres following circumflex coronary occlusions in dogs. Overall flow to the ischaemic posterior papillary muscle and subjacent myocardium decreased to 21% of anterior free wall flow. Collateral flow was non-uniform, however, and was lower in the subendocardium (14%) than in the subepicardium (27%). Brief temporary occlusions with and without propranolol therapy showed that collateral flow was less and the inner/outer wall ratio was unaltered in treated animals. Although propranolol reduces infarct size after coronary occlusions, this effect appears not to be related to increases in collateral flow.

Acute Disease↗
PubMed1976

Reduction of experimental myocardial infarct size with hyperosmolar mannitol.

Hypertonic mannitol previously has been shown to improve cardiac function, increase collateral flow, and decrease epicardial ST segment elevation following coronary occlusion in anesthetized or awake dogs. The present study quantitates by morphologic techniques, the effect of hypertonic mannitol on infarct size. Ischemic injury was produced by proximal occlusion of the circumflex artery for 40 min and necrosis was assessed after 48 hr of reflow. One group of dogs was given isotonic saline and the other hypertonic mannitol beginning the infusions just prior to, during, and for a short period after the release of the circumflex coronary artery occlusion. Serum osmolality increased by approximately 40 mOsm in the mannitol group. The administration of hypertonic mannitol was associated with a 40-50% reduction in infarct size ventricular fibrillation during occlusion and following release of the circumflex coronary artery occlusion was greater in mannitol-treated dogs although the difference was not statistically significant. Thus, the data obtained in this study extend previous observations and provide direct evidence that hypertonic mannitol can reduce infarct size in dogs with temporary circumflex artery occlusion and reflow.

Animals↗
PubMed1975

Distribution of coronary arterial flow in acute myocardial ischemia.

Thioflavin S (TS), a fluorescent dye, was used to visualize the distribution of coronary flow within the area of ischemia produced by circumflex artery occlusions. In the ischemic region, TS failed to penetrate the subendocardium and was seen in the subepicardium. Even though collateral flow was noted in the subepicardium, studies with methylene blue showed that it was inadequate to prevent the development of ischemia. The proportion of the posterior papillary muscle and subjacent myocardium showing TS nonfluorescence was similar after 15 and 60 minutes of ischemia and correlated with maximum lead II ST segment elevation and the percent of grossly injured myocardium found at 60 minutes postocclusion. The results suggest that flow to ischemic myocardium is reduced to the greatest extent in the subendocardium, ie, the site where irreversible injury first appears.

Acute Disease↗
PubMed1975

Ischemic tissue injury.

The subendocardial to subepicardial gradient in the severity of ischemia following acute coronary occlusion is described. The effects of mild, moderate, and severe ischemia on cell structure and function are compared in summary form, and special attention is given to the effects of severe ischemia on myocardial cells. The characteristics of reversible and irreversible ischemic injury are defined in biologic terms. The failure of cell volume regulation in cells which have entered an irreversible state of ischemic injury is demonstrated by the use of free-hand slices in vitro. Irreversibility is associated with structural defects in the plasma membrane and is reflected in an increased slice inulin-diffusible space, increased slice H2O and Na+ content, and failure of the tissue to maintain the high K+ and Mg2+ levels characteristic of normal left ventricular myocardium. Defective cell membrane function is an early feature of irreversible ischemic injury and may be a primary event in the genesis of the irreversible state.

Animals↗
PubMed1975

Demonstration of the "no-reflow" phenomenon in the dog heart after temporary ischemia.

The effect of 40- or 90-min periods of temporary myocarardial ischemia on the distribution of coronary flow and capillary structure were assessed in groups of mongrel dogs. Thioflavin S. a fluorescent dye which stains vascular endothelium when injected intravenously, was used to demonstrate the distribution of microvascular perfusion at 10 sec, 5 min, or 20 min following release of a 40-or 90min circumflex coronary artery occlusion. Hearts which demonstrated perfusion defects were sampled for electron microscopy. Following 40 min of occlusion, thioflavin S was distributed uniformly throughout the myocardium. In contrast, following 90-min periods of coronary occlusion, perfusion defects always were present in the subendocardial half of the posterolateral left ventricular wall. Several morphological features in these areas of no reflow were observed by electron microscopy, including decreased endothelial pinocytotic vesicles, endothelial gaps and bleb formation, capillaries packed with erythrocytes, occasional intraluminal thrombi, and extravascular erythrocytes and fibrin. Myocardial cells showing severe injury always were seen within but also extended beyond the areas of poor perfusion. These results demonstrate that areas of no reflow occur following 90-min periods of ischemic injury in the dog, but that primary myocardial cell injury occurs during the ischemic period and not as a function of the "no-reflow" phenomenon.

Animals↗
PubMedDate not supplied

Three-dimensional distribution of collateral blood flow within the anatomic area at risk after circumflex coronary artery occlusion in dogs.

It is generally accepted that occlusion of a major coronary artery in the dog results in a transmural gradient of collateral blood flow, with the subepicardial region receiving the greatest perfusion. The lateral and base to apex distribution of collateral blood flow and of metabolic and functional consequences of ischemia have been more difficult to define. One reason for such difficulties has been the failure to define the anatomic boundaries of the ischemic vascular bed so that uncontaminated samples of ischemic and non-ischemic tissue could be selected for study. In the present study, the three dimensional distribution of myocardial blood flow during occlusion of the circumflex artery was mapped in seven dogs. At the end of the study, the boundaries of previously ischemic and non-ischemic regions were identified by simultaneous coronary perfusion with red and blue dyes. Left ventricular slices were separated into ischemic and non-ischemic vascular beds based on the dye boundaries, with 1-2 mm of tissue trimmed from this interface to eliminate visually apparent admixture. The ischemic vascular bed of each cross sectional slice then was cut into five transmural wedges, each 3-5 mm wide; each wedge was further subdivided into subendocardial, middle, and subepicardial thirds. The results of blood flow measurements in these samples indicate that the dye injection technique identifies a real interface with a sharp lateral transition in blood flow between ischemic and non-ischemic vascular beds. Within the ischemic vascular bed, there is a transmural gradient of collateral blood flow, but within a given mural layer, there is no consistent gradient from the center to lateral edge or from base to apex of the ischemic region. Thus, in studies designed to characterize the properties of myocardium on either side of the ischemic/non-ischemic interface, reasonable resolution can be achieved by coronary dye infusions to permit visual identification of this interface. On the other hand, in studies in which collateral blood flow is measured as a baseline predictor of infarct size, measurements can be made in a central ischemic block which will be representative of most or all of the ischemic region. Borderzone samples can be excluded to avoid contamination of ischemic samples with non-ischemic tissue.

Animals↗
PubMedDate not supplied

Cardiac pathology following resuscitative circulatory support. Direct mechanical ventricular actuation versus cardiopulmonary bypass.

Cardiopulmonary bypass (CPB) is currently advocated for treating refractory cardiac arrest. Direct Mechanical Ventricular Actuation (DMVA) is an alternative method that does not contact the blood and has other unique advantages for providing resuscitative circulatory support, including rapid application and relative technical simplicity. The purpose of this study was to assess pathologic changes in the heart following resuscitation with either CPB or DMVA. Dogs (n = 22) received 1 hr of CPB (n = 11) or DMVA (n = 11) following a 12.5 min cardiac arrest. All deaths [4/11 (CPB) vs. 2/11 (DMVA), p = 0.31] occurred during the initial 24 postoperative hours. At 7 days, survivors had magnetic resonance imaging to determine cardiac ejection fraction [46% (CPB) vs. 51% (DMVA), p = 0.39], as well as the presence of cardiac wall motion abnormalities [50% (CPB) vs. 33% (DMVA), p = 0.57] and gross cardiac lesions [17% (CPB) vs. 17% (DMVA)]. The survivor's hearts were then extirpated, fixed, and examined for gross lesions [2/7 (CPB) vs. 0/9 (DMVA), p = 0.17]. Transmural sections of the anterior and posterior papillary muscles were histologically evaluated. The severity and extent of epicardial fibrosis and focal myocyte necrosis did not differ between groups. These data demonstrate that DMVA does not cause more myocardial trauma than CPB when used to provide resuscitative circulatory support. Therefore, the unique attributes of DMVA may improve resuscitation outcome in patients who suffer refractory cardiac arrest, without additional risk of cardiac injury.

Animals↗
PubMedDate not supplied

Prolonged total circulatory support using direct mechanical ventricular actuation.

Direct mechanical ventricular actuation (DMVA) is a unique, non blood contacting method for biventricular cardiac assist. Although DMVA has successfully provided cardiac assist for more than 7 days in humans, with long-term survival, its potential for long-term circulatory support has not been adequately investigated. DMVA has not been studied in the large ruminants commonly used to evaluate support devices. To develop a large animal experimental model of prolonged total circulatory support using DMVA, Suffolk sheep (n = 10) underwent sterile instrumentation for hemodynamic and chemistry monitoring. After baseline values were obtained, a left lateral thoracotomy and pericardotomy were performed. Upon electrical ventricular fibrillation (VF), DMVA was begun and the thoracotomy closed. Total circulatory support was continued until mean arterial pressure (MAP) persisted below 50% of the baseline value for more than 1 hr, with a goal of 7 days' support. Mean duration (plus or minus the standard deviation [SD]) of circulatory support was 65.9 +/- 56.8 hr (range, 10-168 hr). Pressors were not used during DMVA support. The subject supported for the maximal time (7 days) was defibrillated into sinus rhythm. No CK-MB fraction was greater than 1%, suggesting that DMVA, even with prolonged application during VF, does not result in myocardial injury. Blood urea nitrogen and creatinine levels indicate renal function was preserved. The model described represents the longest period any animal has been supported in VF using DMVA. This new model will be useful in determining what limitations, if any, exist to the prolonged use of DMVA for circulatory support.

Animals↗