PubMed Health⌕ Search

Biomedical subjects

K C Allman

Publications and source records attributed to K C Allman.

32 records · Page 2Linked to original sources
PubMed1993

Noninvasive assessment of cardiac diabetic neuropathy by carbon-11 hydroxyephedrine and positron emission tomography.

OBJECTIVES: The purpose of this investigation was to evaluate the sympathetic nervous system of the heart by positron emission tomographic (PET) imaging in patients with diabetes mellitus with and without diabetic autonomic neuropathy. BACKGROUND: The clinical assessment of cardiac involvement in diabetic autonomic neuropathy has been limited to cardiovascular reflex testing. With the recent introduction of radiolabeled catecholamines such as carbon (C)-11 hydroxyephedrine, the sympathetic innervation of the heart can be specifically visualized with PET imaging. METHODS: Positron emission tomographic imaging was performed with C-11 hydroxyephedrine and rest myocardial blood flow imaging with nitrogen-13 ammonia. Three patient groups were studied, including healthy volunteers as control subjects, diabetic patients with normal autonomic function testing and diabetic patients with varying severity of autonomic neuropathy. Homogeneity of cardiac tracer retention as well as absolute tracer retention was determined by relating myocardial tracer retention to an arterial C-11 activity input function. RESULTS: Abnormal regional C-11 hydroxyephedrine retention was seen in seven of eight patients with autonomic neuropathy. Relative tracer retention was significantly reduced in apical, inferior and lateral segments. The extent of the abnormality correlated with the severity of conventional markers of autonomic dysfunction. Absolute myocardial tracer retention index measurements showed a 45 +/- 21% decrease in distal compared with proximal myocardial segments in autonomic neuropathy (0.069 +/- 0.037 min-1 vs. 0.13 +/- 0.052 min-1, p = 0.02). CONCLUSIONS: This study demonstrates a heterogeneous pattern of neuronal abnormalities in patients with diabetic cardiac neuropathy. The extent of this abnormality correlated with the severity of neuropathy assessed by conventional tests. Future studies in larger groups of patients are required to define the relative sensitivity of this imaging approach in detecting cardiac neuropathy and to determine the clinical significance of these scintigraphic findings in comparison with conventional markers of autonomic innervation.

Adult↗
PubMed1993

Carbon-11 hydroxyephedrine with positron emission tomography for serial assessment of cardiac adrenergic neuronal function after acute myocardial infarction in humans.

OBJECTIVES: The purpose of this study was to assess the extent and reversibility of neuronal abnormalities in patients with an acute myocardial infarction. BACKGROUND: Previous experimental studies have described ischemic injury to sympathetic neurons exceeding the area of myocardial necrosis. Carbon-11 (C-11) hydroxyephedrine (HED) is a norepinephrine analogue that can be used for the noninvasive evaluation of neuronal integrity using positron emission tomography. METHODS: We studied 14 volunteers and 16 patients experiencing a first acute myocardial infarction. Positron emission tomographic imaging was used to quantitatively compare regional perfusion, as assessed with nitrogen-13 ammonia, with myocardial retention of C-11 hydroxyephedrine early after myocardial infarction as well as > 6 months after the acute event. RESULTS: C-11 hydroxyephedrine and flow images demonstrated homogeneous tracer retention in volunteers but were abnormal in all patients. C-11 hydroxyephedrine abnormalities were more extensive than those for blood flow assessed by semiquantitative polar map analysis (31 +/- 15% vs. 17 +/- 17% left ventricle; p < 0.05), particularly in five patients with non-Q wave infarction (31 +/- 11% vs. 3.5 +/- 2.5% left ventricle; p = 0.008). Eleven patients with Q wave infarction had matched defects (28 +/- 17% vs. 21 +/- 17% left ventricle; p = NS). C-11 hydroxyephedrine tissue retention fraction was quantified in three tissue zones: zone 1 (abnormal rest flow) had retention fraction 0.037 +/- 0.022-min; zone 2 (normal rest flow but decreased carbon-11 hydroxyephedrine retention) had retention fraction 0.068 +/- .034-min, and zone 3 (normal flow and carbon-11 hydroxyephedrine retention) had retention fraction 0.087 +/- 0.041-min (p = 0.0004). Follow-up studies at 8 +/- 3 months in eight patients revealed no change in extent of abnormalities or absolute tissue tracer retention in infarct and peri-infarct territories. CONCLUSIONS: The results of abnormal regional sympathetic innervation in patients with infarction confirm previous experimental data and suggest persistent neuronal damage in infarct and peri-infarct territories, without evidence of reinnervation of reversibly injured myocardium.

Adrenergic Fibers↗
PubMed1993

Myocardial glucose uptake in patients with insulin-dependent diabetes mellitus assessed quantitatively by dynamic positron emission tomography.

BACKGROUND: Animal studies have demonstrated reduced myocardial glucose utilization in the diabetic heart, suggesting abnormalities in glucose transport. This study was designed to evaluate myocardial glucose uptake as assessed by 2-fluoro-(fluorine-18)2-deoxy-D-glucose (FDG) and positron emission tomography (PET) in patients with insulin-dependent diabetes mellitus (IDDM) under standardized metabolic conditions. METHODS AND RESULTS: A hyperinsulinemic-euglycemic clamp technique was used during PET data acquisition in nine healthy male volunteers and seven young male patients with a history of IDDM for less than 5 years. Oxidative metabolism was assessed with C-11 acetate, and glucose uptake was quantitatively measured with FDG using Patlak graphic analysis. Hemodynamic data and C-11 acetate kinetics were comparable. Myocardial glucose uptake averaged 0.44 +/- 0.12 mumol.g-1.min-1 in normal subjects and 0.43 +/- 0.16 mumol.g-1.min-1 in patients with IDDM (P = NS). Blood tracer clearance was also similar in both groups as determined by the ratio of peak blood tracer activity to the activity at 55 to 60 minutes after tracer injection. F-18 activity ratio between myocardium and blood pool averaged 7.2 +/- 3.4 in the normal heart and 7.5 +/- 3.0 in the diabetic heart (P = NS). CONCLUSIONS: These data indicate that metabolic standardization and supplementation with insulin in young patients with IDDM is associated with myocardial glucose uptake similar to that observed in the normal heart. Chronic therapy with insulin may prevent the metabolic abnormalities observed in diabetic animal models.

Acetates↗
PubMed1992

Determination of extent and location of coronary artery disease in patients without prior myocardial infarction by thallium-201 tomography with pharmacologic stress.

Seventy-six patients undergoing pharmacologic stress 201TI tomography and coronary angiography within 14 +/- 12 days were studied to determine how well coronary artery disease extent and location could be determined by this scintigraphic technique. No patient had prior myocardial infarction or revascularization. Scintigrams were scored visually and quantitatively. Angiographic lesions > or = 50% were considered significant. Receiver operating characteristic curves were generated for the scintigrams against the angiographic gold standard. Predictive accuracies were determined and compared with the quantitative results. Predictive accuracy was 0.49 for visual and 0.58 for computer identification of single-vessel disease, 0.52 for both visual and computer identification of multivessel disease, 0.64 for both in correctly localizing left anterior descending artery disease, 0.78 versus 0.70 for the right coronary artery and 0.72 versus 0.68 for the left circumflex artery. For the overall detection of disease, the predictive accuracies were 0.79 and 0.80. Although high diagnostic accuracy for detection of coronary artery disease by this approach has been previously documented, the assessment of extent of disease in patients without prior myocardial infarction appears limited.

Adenosine↗
PubMed1991

Prognostic significance of right ventricular ejection fraction following inferior myocardial infarction.

The prognostic significance of right ventricular ejection fraction, measured by radionuclide ventriculography, was assessed in 168 consecutive patients with inferior myocardial infarction. Right ventricular ejection fraction was 0.40 or less in 35 patients. Over a follow-up period of 40 months, there were 15 deaths in the total group of 168 patients, eight (23%) in the 35 with right ventricular ejection fraction of 0.40 or less, and seven (5%) in the remainder of the group. The one year survival of patients with right ventricular impairment (84 +/- 6%) was significantly worse (P less than 0.01) than those with a right ventricular ejection fraction over 0.40 (95 +/- 2%). A multivariate Cox model analysis showed age (P less than 0.001), left ventricular ejection fraction (P less than 0.01), and right ventricular ejection fraction (P less than 0.03) to be independent predictors of survival. Impaired right ventricular function is an adverse prognostic factor in patients with inferior infarction, particularly in those with impaired left ventricular function.

Female↗
PubMed1991

Prognostic significance of a predischarge exercise test in risk stratification after unstable angina pectoris.

The prognostic significance of exercise testing was compared with clinical and electrocardiographic (ECG) variables in a prospective study of 107 patients with unstable angina discharged from the hospital on medical therapy. During a follow-up period of 12.8 +/- 1.4 months, 10 patients (9%) had a nonfatal myocardial infarction (n = 8) or died (n = 2) and 22 (20%) were readmitted with recurrent unstable angina. The relation between 20 clinical, ECG and exercise test variables and the risk of adverse outcome (death, nonfatal myocardial infarction or recurrent unstable angina) was analyzed using both univariate and multivariate (logistic regression) analysis. Univariate predictors of adverse outcome included diabetes mellitus, evolutionary T wave changes, T wave changes on the preexercise ECG and low maximal rate-pressure product during exercise. Independent predictors of adverse outcome in multivariate analysis included diabetes mellitus, evolutionary T wave changes after admission, rest pain during hospitalization, ST depression during exercise and low maximal rate-pressure product. A predictive model constructed using the regression equation and all independent predictors stratified patients into high and low risk groups (41% and 5% risk of adverse outcome, respectively). The result of a predischarge exercise test adds independent prognostic information to clinical and ECG data in medically treated patients with unstable angina and could be used in combination with clinical and ECG data to identify patients at risk of adverse events.

Angina, Unstable↗
PubMed1990

Current role of gallium scanning in the management of lymphoma.

Gallium 67 scanning in the malignant lymphomas has been done, with variable success, for over 20 years. After initial enthusiasm, the technique fell into disrepute and it was not until the early 1980s that it enjoyed a revival. There have been many major contributions to the literature, both favourable and unfavourable. The reasons for the latter include: poor instrumentation (only single-pulse height analysis), low gallium 67 doses, impatient and careless scanning techniques, timing of the study after treatment (chemotherapy, radiation) and insensitive methods of confirmation of the presence or absence of disease ("truth"). Anatomical diagnostic techniques (computed tomography, plain X-radiography, magnetic resonance imaging and others) are incapable of distinguishing viable tumour in normal-size lymph nodes or necrotic/fibrotic residual masses. With improvements in instrumentation (triple-pulse height analysis, gamma camera resolution and tomographic techniques) gallium 67 can detect active tumour in residual masses and in normal-size nodes. This is due to gallium 67's unique ability to localize in viable tumour cells. It has greater than 90% sensitivity, specificity, accuracy and positive predictive value in patients with lymphoma. Its major contributions are in: staging (changing management of mediastinal disease, obviating the need for a laparotomy and clearly identifying stage IV disease); detecting relapse or residual, progressive disease (it establishes true complete remission and is often the first and only evidence of relapse before clinical evidence); predicting response to therapy (failure to convert to a negative scan post-treatment signals a poor prognosis and alternative therapy is required); and predicting outcome--prognosis (it is the only diagnostic modality to predict outcome accurately).

Gallium Radioisotopes↗
PubMed1989

Patterns of left ventricular dilation during the six months after myocardial infarction.

Changes in left ventricular volume after a first myocardial infarction were studied in 50 patients. Serial radionuclide angiograms were obtained 48 h, 10 days and 1 and 6 months after infarction and left ventricular volume measured by a nongeometric method. Left ventricular dilation (greater than or equal to 20% increase in end-diastolic volume) occurred within 10 days of infarction in 11 patients, who had a mean volume increase of 34 +/- 15% (p = 0.002 versus 48 h) at 10 days and 61 +/- 43% (p = 0.01 versus 10 days) at 6 months. Ten other patients manifested left ventricular dilation between 10 days and 6 months with a lesser volume increase of 42 +/- 18% by 6 months. Among the 21 patients with ventricular dilation, progressive dilation (serial volume increases greater than or equal to 20% on two or more occasions) occurred in 8 patients, who all had a large anterior infarct. Mean volume increases at 10 days and 1 and 6 months were 27 +/- 20%, 49 +/- 40% (p = 0.03 versus 10 days) and 79 +/- 37% (p = 0.006 versus 1 month), respectively, in this group. In patients with progressive dilation, left ventricular ejection fraction decreased from 35 +/- 6% at 48 h to 24 +/- 10% at 1 month (p less than 0.001) and 27 +/- 10% (p = 0.006) at 6 months. Between 1 month and 2 years after infarction six patients died, of whom four had progressive dilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMedDate not supplied

Streptococcal abscesses following diphtheria-tetanus toxoid-pertussis vaccination.

Abscesses developed in seven children who received diphtheria-tetanus toxoid-pertussis vaccine at a clinic in Indiana. Epidemiologic investigation revealed that all seven children had received vaccine from the same multidose vial and had been vaccinated by the same nurse at the office of one physician. Group A beta-hemolytic Streptococcus was isolated from abscesses in six of the seven children. No source was identified as the cause of this cluster of abscesses. Vaccine of the same lot number used elsewhere was not associated with the development of abscesses. It appears that the vaccine became contaminated during use.

Abscess↗