The hemodynamic determinants of the isovolumic index

The isovolumic index is a recently described echocardiographic parameter of left ventricular function that is calculated as the ratio between the sum of the time of isovolumic contraction and relaxation divided by the ejection time. Although the individual components of this index may be altered by heart rate and loading conditions, an analysis of the net effect of such alterations on the isovolumic index has not been undertaken. Thus, dogs were instrumented with high-fidelity micromanometers in the left ventricle, ascending aorta, and left atrium to allow determination of the individual comoonents of the isovolumic index and calculation of the index itself. Four sets of experiments were undertaken in random order. Left atrial pacing was used to increase heart rate by approximately 10 bpm in five steps. Preload was elevated in five stages by saline infusions which caused successive increases of 1 to 2 mm Hg in the left ventricular end-diastolic pressure. Systolic blood pressure was lowered or raised by approximately 10 mm Hg per stage by three progressive, steady-state infusions of nitroprusside and phenylephrine, respectively. These experiments demonstrated little change in the isovolumic index over a broad range of heart rate. Increased left ventricular end-diastolic pressure and decreased systemic pressure caused shortening of the index. Multiple regression analysis of all experiments yielded the following: isovolumic INDEX = 0.41 - 0.015 (left ventricular end-diastolic pressure) + 0.004 (systolic blood pressure); r = 0.57, standard ERROR = 0.13, p < 0.0001. Therefore, this investigation establishes the hemodynamic determinants of the isovolumic index and provides the basis for interpretation of directional changes in response to cardiac diseases and cardioactive drugs that can alter loading conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26036/1/0000109.pd

Cardiac care unit admission criteria for suspected acute myocardial infarction in new-onset atrial fibrillation

Management of new-onset atrial fibrillation (AF) varies between institutions and individual physicians. Because AF often occurs in elderly patients and is associated with coronary artery disease, patients presenting for the first time are often selected for admission to the coronary care unit to exclude the possibility of acute myocardial infarction (AMI). A review of 245 patients with AF admitted to an intensive care unit revealed 45 cases that were of new onset. AMI was diagnosed in 5 (11 % ) on the basis of elevated serum creatine kinase-MB levels. Evaluation of 56 clinical variables available during initial assessment indicated that infarction patients could be distinguished from others by the presence of left ventricular hypertrophy (p <0.01), electrocardiographic evidence of old myocardial infarction (p <0.01), typical cardiac chest pain (p <0.01), and duration of cardiac symptoms less than 4 hours (p <0.05). The presence of 2 or more of these features identified all AMI patients and 7 others at high risk for serious cardiac complications. The findings indicate that new-onset AF in the absence of clinical predictors suggesting myocardial ischemia or AMI does not warrant routine admission to the coronary care unit.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26764/1/0000316.pd

Rapidly progressive heart failure resulting from cardiac sarcoidosis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27288/1/0000307.pd

Dissection of genetic associations with language-related traits in population-based cohorts

Recent advances in the field of language-related disorders have led to the identification of candidate genes for specific language impairment (SLI) and dyslexia. Replication studies have been conducted in independent samples including population-based cohorts, which can be characterised for a large number of relevant cognitive measures. The availability of a wide range of phenotypes allows us to not only identify the most suitable traits for replication of genetic association but also to refine the associated cognitive trait. In addition, it is possible to test for pleiotropic effects across multiple phenotypes which could explain the extensive comorbidity observed across SLI, dyslexia and other neurodevelopmental disorders. The availability of genome-wide genotype data for such cohorts will facilitate this kind of analysis but important issues, such as multiple test corrections, have to be taken into account considering that small effect sizes are expected to underlie such associations

Vilhelm Lundstedt’s ‘Legal Machinery’ and the Demise of Juristic Practice

This article aims to contribute to the academic debate on the general crisis faced by law schools and the legal professions by discussing why juristic practice is a matter of experience rather than knowledge. Through a critical contextualisation of Vilhelm Lundstedt’s thought under processes of globalisation and transnationalism, it is argued that the demise of the jurist’s function is related to law’s scientification as brought about by the metaphysical construction of reality. The suggested roadmap will in turn reveal that the current voiding of juristic practice and its teaching is part of the crisis regarding what makes us human

Relation between graded, subcritical impairments of coronary flow reserve and regional myocardial dysfunction induced by isoproterenol infusion in dogs

Isoproterenol has been used experimentally and clinically to elicit ischemia. The usefulness of this approach, however, in eliciting regional dysfunction in the presence of mild to moderate single-vessel coronary disease quantitated on the basis of coronary flow reserve measurements has not been previously defined. Open-chest, anesthetized dogs were instrumented with an electromagnetic flow probe, high-fidelity micromanometers, and subendocardial ultrasonic crystals. A rigid, screw occluder was used to produce five subcritical coronary stenoses in each dog associated with varying impairment of postocclusion reactive hyperemia at rest but no impairment of resting coronary blood flow. Regional function at rest and in response to the isoproterenol challenge (0.25 [mu]g/kg/min) in nonstenotic and stenotic conditions was assessed. Relative regional function was maintained during the infusion until nearly total loss of coronary flow reserve. With this near-critical stenosis, function was lower than in the nonstenotic state but remained greater than resting control values. Moderate impairments of coronary flow reserve were not associated with isoproterenol-induced deterloration of regional function. In conclusion, detection of impaired coronary flow reserve at rest is a more sensitive index of the severity of a coronary stenosis than is detection of regional dysfunction during isoproterenol challenge. Fallure to maintain the expected isoproterenol-induced increase in regional function is manifested only when stenoses are associated with nearly total loss of resting coronary flow reserve. This suggests that the clinical use of isoproterenol challenge is not effective in eliciting regional dysfunction when mild coronary disease is present.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26766/1/0000318.pd