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

Signs of sympathetic activation are frequent during the early hours of anterior wall acute myocardial infarction, whereas parasympathetic reflexes predominate in inferior wall acute myocardial infarction. To assess the immediate autonomic responses to acute coronary occlusion, the high-frequency power and root-mean-square successive difference, frequency and time domain measures of heart rate (HR) variability were analyzed in 73 cases of significant (50 to 95%) coronary artery stenosis immediately before and during balloon occlusion (mean 99 seconds). The range of nonspecific changes was formed on the basis of a control group with no ischemia during dilatations of 16 totally occluded coronary arteries. Balloon occlusion of the left anterior descending artery (n = 35) caused an abnormal increase in the measures of HR variability as a sign of vagal activation in 8 patients (23%), and a significant decrease in HR variability in 4 (11%). Occlusion of the left circumflex artery (n = 19) caused an increase in HR variability in 5 patients (26%), and a decrease in 2 (11%). Right coronary artery occlusion (n = 19) caused an increase in HR variability in 5 patients (26%) and a decrease in 4 (21%). Thus, coronary occlusion causes immediate changes in HR variability in greater than one third of patients with coronary artery disease. The direction of these initial HR variability changes cannot be predicted by the site of coronary occlusion.
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PMID:Responses of heart rate variability to coronary occlusion during coronary angioplasty. 821 82

Right ventricular (RV) ischemia occurs in 50% of patients with acute inferior myocardial infarction, and may result in severe hemodynamic compromise associated with poor clinical outcome. Right coronary artery occlusion proximal to the RV branches results in RV systolic dysfunction, which decreases transpulmonary delivery of left ventricular (LV) preload and diminishes cardiac output. The ischemic right ventricle is stiff, dilated, and volume dependent, resulting in pandiastolic RV dysfunction. Under these conditions, RV pressure generation and output depend on LV-septal contractile contributions. When the culprit coronary lesion is distal to the right atrial (RA) branches, augmented RA contractility enhances RV performance and optimizes cardiac output. Conversely, more proximal occlusions result in ischemic depression of RA contractility, which impairs RV filling and performance, leading to more severe hemodynamic compromise. Bradyarrhythmias limit the output generated by the rate-dependent noncompliant ventricles. Patients with RV ischemia and hemodynamic compromise often respond to volume resuscitation and restoration of a physiologic rhythm. In some patients, parenteral inotropic stimulation may be required. The ischemic right ventricle appears to be relatively resistant to infarction and has a remarkable ability to recover. The term RV infarction appears to be a misnomer, as RV performance improves spontaneously even in the absence of reperfusion. Reperfusion, however, enhances the recovery of RV performance and improves the clinical course.
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PMID:Pathophysiology and clinical management of right heart ischemia. 1044 14