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Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25969/1/0000035.pd

Serial assessment of circumferential regional left ventricular function following complete coronary occlusion

The effect of abrupt coronary artery occlusion on regional left ventricular (LV) function is well known, but serial changes in circumferential regional function over the first few hours have not been extensively investigated. Circumflex coronary artery occlusion was produced in nine closed-chest, conscious dogs and changes in LV circumferential function were assessed using two-dimensional echocardiography (2DE) performed in the short-axis projection at the mid-papillary muscle level. End-diastolic and end-systolic frames were manually digitized and regional area ejection fractions at 22.5-degree intervals were calculated using a fixed diastolic center of mass. Endocardial motion abnormality was measured from a circumferential regional ejection fraction map. The extent of wall motion abnormality was measured as that exceeding 95% confidence limits of normal controls; the degree of dyssynergy was measured as the planimetered area of the extent of wall motion abnormality. Following circumflex coronary artery occlusion, a wall motion abnormality was well defined with a minute of occlusion and its circumferential extent measured 146 +/- 16 degrees with 11 +/- 2 cm2 absolute degree of dyssynergy. These parameters did not change over the course of the coronary artery occlusion. We conclude that circumferential regional abnormalities produced by coronary occlusions are well defined early and do not change over the first 3 hours of acute ischemia and infarction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26064/1/0000138.pd

Long-term follow-up of coronary artery occlusion secondary to blunt chest trauma

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26913/1/0000479.pd

Radionuclide assessment of regional left ventricular function in acute myocardial infarction

To determine changes in global and regional left ventricular function following acute myocardial function, 17 patients underwent radionuclide angiography at 3 and 10 days post infarction. Five patients had nontransmural myocardial infarction and 12 had transmural infarction (six anterior and six inferior). There were no previous infarctions in 16 (94%) patients. Regional ejection fractions were calculated by dividing the left ventricle into four quadrants using the geometric center of the left ventricle on the end-diastolic frame as a reference point. At 3 days post infarction, 8 of 17 (47%) patients had an abnormality of global left ventricular ejection fraction (LVEF), whereas 16 of 17 (94%) patients had abnormalities of one or more regional ejection fractions (p p = NS). However, there were significant changes in 23 of 68 (34%) regional LVEFs. These changes did not relate to type, ECG location, creatine kinase (CK) size of infarction, or initial global LVEF. These data suggest that regional LVEF is a sensitive technique for identifying segmental dysfunction associated with myocardial infarction. In addition, significant changes occur in regional LV function during acute myocardial infarction despite stable serial global LV performance.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26327/1/0000414.pd

Spatial and temporal characteristics of circumferential flow-function relations during acute myocardial ischemia in the conscious dog

In the anesthetized open-chest dog the ischemic area produced by coronary occlusion is surrounded by an area of nonischemic contractile dysfunction, identified as the functional border zone. To establish whether a similar functional border zone exists in the conscious animal during acute regional ischemia and to determine its spatial dimensions and temporal changes, we performed simultaneous two-dimensional echocardiography and radioactive microsphere studies in nine chronically instrumented dogs. We produced circumferential flow-function maps at 22.5-degree intervals over the full circumference of the left ventricle at the midpapillary muscle level during control conditions, 5 minutes after left circumflex occlusion, and 2.5 hours after left circumflex occlusion. After occlusion there was no change in left ventricular end-diastolic area, an increase in left ventricular end-systolic area (p p p p < 0.01) in the functional border zone, there was no difference in subendocardial blood flow between the functional border zone and the control nonischemic area. We conclude that a discrete functional border zone exists in the conscious dog during acute regional ischemia produced by circumflex coronary occlusion, which does not change during the early evolution of myocardial infarction. The functional border zone likely contributes to minor overestimation of infarct size in the early hours after myocardial infarction if extent of left ventricular dysfunction is used as an index of infarction in humans.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27055/1/0000045.pd

Importance of overweight in studies of left ventricular hypertrophy and diastolic function in mild systemic hypertension

The relations of Metropolitan Life Insurance Co. Relative Weight values and blood pressure (BP) to minimal forearm vascular resistance, ventricular septal and posterior wall thickness, left ventricular (LV) mass index and cardiac diastolic function were assessed in 31 men, 37 +/- 2 (mean +/-standard error of the mean) years of age. Eighteen patients with untreated mild hypertension were compared with 13 normotensive control subjects of similar age and weight. The hypertensives had higher clinic (137 +/-3/96 +/- 2 vs 121 +/-4/81 +/- 3 mm Hg, p 2). Furthermore, diastolic peak filling rate, an index of LV diastolic function, was virtually identical in the 2 groups (2.71 +/- 0.14 vs 2.69 +/- 0.07 liters/s, difference not significant). Correlates of peak filling rate included relative weight (r = -0.62, p The results suggest that relative weight is an important determinant of diastolic function and LV dimensions. These findings highlight the importance of controlling for weight in comparative studies of cardiovascular structure and function.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27747/1/0000139.pd

Streptokinase thrombolysis in experimental coronary artery thrombosis: pattern of reflow and effect of a stenosis

We studied recanalization of an obstructed left circumflex coronary artery by streptokinase in open-chest anesthetized dogs. Thrombotic occlusion was induced by a 100 [mu]A anodal current selectively delivered to the intimal surface of the vessel. Intracoronary streptokinase (50,000 U) or saline was infused over a 50-min period beginning at either 30 min or 90 min after occlusion. Continous recordings were made of antegrade circumflex flow and regional myocardial function, which was quantitated using sonomicrometer crystals in the regions of the left anterior descending and circumflex coronary arteries. In some experiments a fixed stenosis, having no effect on mean circumflex coronary artery blood flow, was placed at the site of subsequent thrombus formation. The presence of a stenosis decreased the weight of occlusive thrombi obtained from nonreperfused saline controls by 40% and increased the proportion of animals successfully reperfused by streptokinase from 13 to 76%. Streptokinase reduced thrombus mass by 44% in animals recanalized in the presence of the stenosis. On the average, reflow was established after 26 min of streptokinase infusion, was less in magnitude than pre-occlusion flow, and was unstable and intermittent, being marked by frequent reocclusions. Initiating treatment at 30 min or 90 min post-occlusion did not influence characteristics of the reflow. Return of myocardial contractility in the ischemic bed was not detected during the immediate reperfusion period in the majority of these experiments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24656/1/0000069.pd

The effect of different mechanisms of myocardial ischemia on left ventricular function

Myocardial ischemia may be produced by limitation of blood flow as in abrupt coronary occlusion, termed supply-type ischemia, or by increasing myocardial oxygen demand in the setting of restricted flow, termed demand-type ischemia. To examine the comparative extent and severity of the dysfunction related to both forms of ischemia, we studied anesthetized, open-chest dogs by means of two-dimensional echocardiography and tracer microspheres. Supply-type ischemia was produced by total occlusion of the LCx (n = 7); demand-type ischemia was induced by infusion of dobutamine after creation of a critical LCx stenosis (n = 6). At the time of the production of ischemia, the group with demand-type ischemia had significant increases in both heart rate (p p p p p p < 0.05). Thus these data suggest that supply-type ischemia produced by coronary occlusion results in a greater extent and degree of left ventricular functional abnormality than pharmacologically induced demand-type ischemia.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27575/1/0000619.pd

Assessment of dysfunction in aortic regurgitation by stress-shortening relationship

Some patients with aortic regurgitation develop irreversible left ventricular dysfunction. The purpose of this study was to noninvasively examine left ventricular function in patients with aortic regurgitation by determining the end-systolic stress-shortening relationship using M-mode echocardiography. Ten normal volunteers and 10 patients with chronic, isolated aortic regurgitation were studied at rest and following load and inotropic alteration by cold pressor testing. The baseline ejection phase indices of ejection fraction and percent fractional shortening did not distinguish between normals and patients with aortic regurgitation (74.6% +/- 2.8% versus 67.0% +/- 4.2%, P = NS and 37.6% +/- 2.4% versus 31.6% +/- 2.7%, P = NS, respectively.) Endsystolic stress was significantly greater in patients with aortic regurgitation both at rest (107.8 +/- 11.6 dynes/cm2 x 10-3 versus 68.4 +/- 4.8 dynes/cm2 x 10-3, P 2 x 10-3 versus 80.1 +/- 4.0 dynes/cm2 x 10-3, P < 0.005). Normals showed increased fractional shortening in the presence of increasing end-systolic stress. Patients with aortic regurgitation showed decreased fractional shortening during increased stress. This response suggests either left ventricular dysfunction with increasing stress or decreased myocardial contractile reserve after cold pressor inotropic stimulation. End-systolic stress-percent fractional shortening relationship may be a sensitive indicator of early left ventricular dysfunction in patients with aortic regurgitation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25611/1/0000159.pd