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

In order to study the occurrence and frequency of ischemia-induced ventricular arrhythmias, we analyzed 105 episodes of spontaneous angina pectoris occurring at rest in 28 hospitalized patients with unstable angina pectoris and proved coronary artery disease. Of 24 patients with serious ventricular arrhythmias during pain, 17 (57%) were arrhythmia-free during monitoring. In the other four patients, 17 of 29 (59%) pain episodes were associated with serious ventricular arrhythmias, and three of these four had serious ventricular arrhythmias during pain-free periods. Each patient tended to manifest the same type of arrhythmia during repeat episodes of pain. It appears that continuous electrocardiogram (ECG) monitoring is important during the initial hospitalization of the patient with unstable angina. The presence of ventricular arrhythmias during pain-free periods indicates a high risk for serious ventricular arrhythmias during episodes of spontaneous pain. These patients should be considered for continued ECG monitoring and antiarrhythmic therapy.
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PMID:Ventricular arrhythmias during unstable angina pectoris. 5 51

The hemodynamic effects of antimigraine drug ergotamine, which is considered contraindicated in patients with coronary artery disease, were studied in pigs with a normal myocardial circulation (doses of 8, 16, and 32 micrograms/kg, i.v.) or with acute coronary stenosis (8 micrograms/kg). In both groups of animals, ergotamine decreased heart rate, cardiac output, and arteriovenous anastomotic blood flow while increasing aortic blood pressure and systemic vascular resistance. No effects on total ventricular blood flow and its distribution within the myocardium were found in normal animals. In animals with a clamp on the left anterior descending coronary artery (LAD), the blood flow to the LAD-perfused area was reduced from 1.10 +/- 0.16 to 0.67 +/- 0.05 cm3/min/g. The endocardium was affected more than the epicardium and the endo/epi flow ratio decreased from 1.18 +/- 0.05 to 0.74 +/- 0.07. Ergotamine increased the blood flow to the ischemic zone towards normal values, and the endo/epi flow ratio to 1.05 +/- 0.21. However, myocardial wall thickness parameters, which showed functional deterioration during ischemia, did not change after ergotamine. The present study provides no clear support for cardiovascular contraindications to ergotamine administration.
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PMID:Regional myocardial perfusion and wall thickness and arteriovenous shunting after ergotamine administration to pigs with a fixed coronary stenosis. 9 33

Eleven patients with short P-R intervals and narrow QRS complexes had ventricular tachycardia due to organic heart disease: mitral valve prolapse with mitral insufficiency (2 patients); alcoholic (?) cardiomyopathy (2 patients); and coronary artery disease (7 patients). Intracardiac studies showed short A-H intervals during sinus rhythm in all cases. The onset of ventricular fibrillation (which, to our knowledge, has not been observed in patients having short P-R and A-H intervals coexisting with narrow QRS complexes) was documented in 4 cases. Only 1 patient (with quinidine syncope) had been premedicated. In the 3 other patients the episodes of ventricular fibrillation appeared during bouts of atrial fibrillation with rapid ventricular rates which could have been an exprerssion of the "enhanced A-V conduction" that had been manifested in sinus beats by short P-R and A-H intervals. In clinical settings and physiological conditions proven to be hemodynamically unstable (such as transient ischemia or acute myocardial infarction) these rapid ventricular rates could have led to ventricular fibrillation; directly because of the R-on-T phenomenon, and/or indirectly due to decreased coronary perfusion. Ventricular tachycardia and ventricular fibrillation due to organic heart disease probably occur more often than suggested by the few reported cases in the literature. Its significance, however, has to be clarified by further prospective studies.
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PMID:Ventricular tachycardia and ventricular fibrillation in patients with short P-R intervals and narrow QRS complexes. 9 18

Coronary arteriolar dilation adjusts blood flow according to local fluctuating metabolic needs of the myocardium. Because of high extravascular compression during systole, the subendocardial layer of the left ventricle is especially dependent on the duration and the perfusion pressure of the diastolic period. In patients with obstructive coronary artery disease, regional arteriolar dilation is utilized to compensate for focal arterial stenoses. Coronary blood flow may be compensated with the patient at rest, but loss of reserve arteriolar dilation limits further adjustment to superimposed transient increases in metabolic needs. Subendocardial perfusion in the region supplied by the stenosed artery is especially vulnerable to shortened diastolic time during tachycardia. In patients with chronic aortic valve disease, the metabolic rate of the left ventricle is increased in proportion to the increases in myocardial mass and work. Coronary blood flow and metabolic rate per gram of the hypertrophied myocardium are normal when the patient is at rest, at the expense of diminished coronary arteriolar reserve. High tissue pressure relative to the diastolic perfusion pressure probably contributes to the diffuse subendocardial ischemia that occurs in these patients during tachycardia.
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PMID:Myocardial oxygen supply in left ventricular hypertrophy and coronary heart disease. 15 5

Radionuclide techniques that assess regional myocardial perfusion and detect acute myocardial infarction promise to provide critical information in the detection and evaluation of coronary artery disease and in the assessment of therapies aimed at limiting the degree of ischemia and the extent of tissue necrosis. Radioindicators such as 99mTc-tetracycline and 99mTc-pyrophosphate which are sequestered by acutely infarcted myocardium provide a direct method to detect an infarct and to determine its size. Regional alterations in myocardial perfusion can be assessed by myocardial scintigraphy performed after the injection of radiopotassium or one of its analogues with the patient either at rest or at exercise. A somewhat more accurate evaluation of the extent of altered perfusion can be obtained after the intracoronary injection of macro-aggregated particles. A quantitative index of altered perfusion can be obtained after the intracoronary injection of an inert gas such as 133Xe.
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PMID:Radionuclide methods in the evaluation of myocardial ischemia and infarction. 17 72

Myocardial ischemia results from an imbalance of energy supply and demand. Because of the essentially aerobic nature of myocardial metabolism and the high oxygen extraction from the blood, ischemia is usually equatable with limitation of blood supply. Coronary atherosclerosis is a patchy disorder, and therefore, ischemia usually occurs in segmental fashion throughout the topography of the heart. Ischemia is invariably seen earliest and most intensely in the deep or subendocardial layers of myocardium. Ischemia leads to biochemical disruption, including initiation of glycolysis, which in turn causes electrophysiological and mechanical disturbances. Myocardial ischemia can be induced naturally or experimentally in the human subject in a variety of ways, some of which have been studied in the laboratory.
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PMID:Myocardial ischemia. 18 72

As has been shown in a large number of animal experiments, there is a marked difference between the systolic-to-diastolic flow ratios of the right coronary artery and the left. We examined these ratios in 107 patients who were undergoing aorto-coronary bypass surgery as treatment for coronary artery disease. After cessation of cardio-pulmonary bypass, the blood flow was recorded electromagnetically in a total of 126 venous grafts to the right or to the branches of the left coronary arteries. From these tracings, the following magnitudes were calculated: coronary stroke flow per heart beat, systolic and diastolic stroke flows, mean flow, systolic and diastolic flows. The ratio of the systolic to the diastolic stroke flow was 0.30 +/- 0.17 for the branches of the left coronary artery (n = 79) and 0.61 +/- 0.30 for the right coronary artery (n = 47). The ratio of systolic to diastolic flow was found to be 0.46 +/- 0.25 (branches of the left coronary artery) and 1.01 +/- 0.62 (right coronary artery), respectively. All these values differ statistically on a probability level of p less than 0.001. In principle, our results agree with those of canine experiments. The considerable variation of the individual values of the systolic-to-diastolic flow ratios can be explained by the following: 1. the variability of the pattern of coronary blood supply in man; 2. the actual right and left ventricular pressures; 3. the extent of stenoses present; 4. the degree of myocardial impairment due to ischemia. These factors combined determine the actual value of the extravascular (myocardial) component of the peripheral coronary resistance, which is most effective during systole.
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PMID:[Dependence of blood flow in human aorto-coronary bypass grafts on the extravascular resistance (author's transl)]. 30 35

Left ventricular echocardiograms and phasic instantaneous Doppler aortic blood velocities were simultaneously recorded during short paroxysms of rapid right ventricular pacing in 20 conscious subjects. Right ventricular pacing at rates of 100, 120, 140, 160 and 180/min produced stepwise reductions of mean estimates for diastolic (D) and systolic (S) left ventricular internal dimensions (LVID) along with a diminution of aortic blood velocity. Mean (X +/- 1 standard deviation) per cent decline of LVID-D, LVID-S and peak aortic blood velocities for the study group ranged from 8.9 +/- 6.1, 8.5 +/- 5.7 and 13.7 +/- 7.7 at 100 beats/min to 29.3 +/- 10.6, 25.2 +/- 10.5 and 55.2 +/- 13.1 at 180 beats/min, respectively. When LVID-D, LVID-S, and aortic blood velocity X % reductions were plotted for all heart rates there was a high degree of positive correlation (r = 0.99). Two types of abnormal septal motion were observed during rapid pacing: Type I--paradoxical septal motion at all pacing rates (n = 7, 6/7 with left coronary artery disease); Type II--hypokinetic septal motion at lower pacing rates with flat or paradoxical motion at rates greater than 140/min (n = 13, 10/13 with normal coronary arteries). It is concluded that short episodes of rapid right ventricular pacing result in reduced LVID and abnormal septal motion with the latter possibly related to septal ischemia. Such study provides insight into the untoward influence of rapid ventricular rhythms on cardiac performance.
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PMID:Simultaneous left ventricular echocardiography and aortic blood velocity during rapid right ventricular pacing in man. 32 84

Echocardiographic findings in patients with ischemic heart disease are described; their correlations with clinical, hemodynamic and angiographic data are presented and discussed. Regional abnormalities of left ventricular wall motion and/or thickening during systole are detected in 84 per cent of patients with acute myocardial infarction and in a high percentage of patients with larger than or equal to 75 per cent narrowing of a major coronary artery. These abnormalities may occur with stress and may be reversible. Left ventricular wall thinning during systole indicates acute ischemia or infarction and thin, dense myocardial echoes indicate scar. Echocardiographic evidence of left ventricular dysfunction is useful in predicting heart failure and mortality in patients with acute myocardial infarction and in predicting surgical mortality for patients undergoing aneurysmectomy and/or coronary artery bypass surgery. Echocardiography has not proved useful in determining graft patency following coronary artery bypass surgery. Technical difficulties and limitations of echocardiography in patients with coronary artery disease are discussed.
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PMID:Echocardiography in ischemic heart disease. 32 1

Myocardial ischemia causes a series of anatomic and physiologic abnormalities that can be detected and quantified by assessment of myocardial perfusion, mechanical function, electrophysiology, and metabolism. These methods of assessment vary widely in sensitivity, specificity, relevance, cost, and ease of application. Although occasionally the appropriate choice of diagnostic procedures is clinically difficult, the demonstrated potential of coronary artery bypass surgery to reverse both acute and chronic myocardial ischemia makes the detection of ischemia an important effort in the care of patients with coronary artery disease.
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PMID:Detection of myocardial ischemia. 33 74


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