Evolutionary paths in arrhythmia management: influences of substrate, studies, and seismology.
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Biomedical subjects
Publications and source records attributed to J Correia.
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The fourth heart sound (S4) has been associated with vigorous atrial contraction. However, the presence of S4 has not been previously correlated with quantitated left atrial filling fraction. In this study, the presence of an auscultatory S4 was compared with the Doppler echocardiographically quantitated left atrial filling fraction in 41 consecutive patients in whom S4 was judged to be present or absent according to the consensus of cardiologists. Left atrial filling fraction in patients with S4 was 49% and was significantly greater than 33% found in patients without S4 (p less than 0.005). Using atrial filling fraction of 35% as a dividing line, S4 had a sensitivity of 84% and a specificity of 75% for determining left atrial filling fraction greater than or equal to 35%. Furthermore, of 25 patients with S4, 21 (84%) had atrial filling fraction greater than or equal to or less than 35%, and of 16 patients without S4, 12 (75%) had atrial filling fraction less than 35%. Thus, the presence or the absence of S4 is quantitatively related to the left atrial filling fraction and appears to predict atrial filling fraction greater than or equal to or less than 35% reasonably well.
Cerebral blood flow was measured by xenon-133 washout in 13 patients 6-46 hours after being resuscitated from cardiac arrest. Patients regaining consciousness had relatively normal cerebral blood flow before regaining consciousness, but all patients who died without regaining consciousness had increased cerebral blood flow that appeared within 24 hours after resuscitation (except in one patient in whom the first measurement was delayed until 28 hours after resuscitation, by which time cerebral blood flow was increased). The cause of the delayed-onset increase in cerebral blood flow is not known, but the increase may have adverse effects on brain function and may indicate the onset of irreversible brain damage.
The absorption characteristics of 3 sustained release quinidine formulations were assessed in 12 healthy male volunteers in a randomised 3-way crossover trial. Each formulation ('Quinidex' 300mg, 'Biquin Durules' 250mg and 'Quinaglute Dura-Tabs' 324mg) was administered as a single tablet every 12 hours for 5 days. Peak quinidine serum concentrations of 2.7 +/- 0.8 mg/L occurred 2.5 +/- 1.1 hour after 'Quinaglute' administration, significantly higher (p less than 0.01) than concentrations of 1.6 +/- 0.4 mg/L achieved 4.2 +/- 1.1 hours following 'Biquin' dosing and 1.7 +/- 0.6 mg/L attained 3.9 +/- 2.7 hours after 'Quinidex' ingestion. The extent of absorption based on AUC infinity and normalised for the anhydrous quinidine content was similar for the 3 products. Following multiple dosing, the mean steady-state trough concentration of quinidine was 2.06 +/- 0.56 mg/L for 'Quinidex', significantly greater (p less than 0.05) than that of 'Biquin' (1.18 +/- 0.67 mg/L) or 'Quinaglute' (1.58 +/- 0.58 mg/L). The rate of absorption was found to be much slower for 'Quinidex' than for the other 2 sustained release quinidine formulations. Comparison of the residual sums of squares from simple linear regression of Wagner-Nelson plots did not demonstrate a preference for a zero- or first-order absorption model. Nevertheless, the absorption of 'Quinidex' was twice as prolonged as that of 'Biquin' and 'Quinaglute' regardless of model; first-order absorption half-lives were 2.83 +/- 1.02 hours, 1.25 +/- 0.6 hours and 1.43 +/- 0.88 hours, respectively. The data also suggest that 'Quinidex' absorption may continue beyond 12 hours in some subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
A sustained-release theophylline preparation (Theo-Dur Sprinkle) was evaluated in young asthmatic patients aged 1 to 6 years and receiving a daily dose of 23.4 +/- 2.0 mg/kg (mean +/- SD) to determine, on the basis of serial serum concentrations obtained over a 12-hour dosing interval at steady state, the suitability of such a product in patients likely to metabolize the drug very rapidly. Peak theophylline concentrations of 15.1 +/- 4.1 mg/L were achieved 5.5 +/- 1.5 hours after dosing. The mean maximum to minimum concentration difference was 6.9 +/- 2.2 mg/L for the dosing interval studied. Fluctuations in theophylline concentration less than 100% were achieved in nine of the 12 study patients. Use of the "sprinkle-technique" with Theo-Dur Sprinkle appears to be a simple and effective method of maintaining acceptable fluctuations in serum theophylline concentrations in preschool asthmatic children.
The influence of 3-9 months of combined low dose oral contraceptives on theophylline pharmacokinetics was studied in 10 adolescent females (age 15-18 years, mean +/- SD 17 +/- 1) and compared to 10 age-matched control subjects (age 13.8-19 years, mean +/- SD 16.5 +/- 1.6). The distribution volume (0.44 +/- 0.06 L/kg in control vs. 0.44 +/- 0.09 L/kg oral contraceptive group), total body clearance (0.78 +/- 0.13 ml/kg/min vs 0.78 +/- 0.18 ml/kg/min) and elimination T 1/2 (402 +/- 78 min vs. 409 +/- 126 min) were identical in the two groups. It appears that during the first 3-9 months of low dose oral contraceptive treatment, these steroids do not alter the pharmacokinetic behaviour of theophylline in adolescent females.
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The parameter derived from right anterior oblique angiocardiography (end diastolic and end systolic volumes, stroke volume, ejection fraction, wall thickness and myocardial mass) are used to decide the most appropriate management of cardiac disease. It is important to assess their reliability especially as other clinical data may be underestimated and the objective results may play a prominent role in the decision. Therefore, good quality cinefilms of 31 patients were reinterpreted by three observers (A, B and C); the contours were traced on a Vanguard console with an electromagnetic pet and the data treated automatically by the SNIASS SYSCOMORAN program (Simpson's method, assimilating the left ventricle to an ellipsoid divided into n identical cylinders). The interobserver variability (A and B; A and C; B and C) was good in the assessment of end diastolic volume (R = 0,96; 0,98; 0,99), end systolic volume (R = 0,96; 0,96; 0,98). On the other hand, it was poor in the measurement of wall thickness (R = 0,63; 0,73; 0,69) and myocardial mass (R = 0,85; 0,83; 0,89). In addition, the ejection fraction and end systolic volume were perfectly reproducible from one observer to another whether or not the left ventricle was dilated. End diastolic volumes seemed to be more reproducible in dilated cavities (EDV greater than 104 ml/m2). These results confirm that monoplane RAO cineangiography remains a good method of assessing left ventricular performance.
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This report describes the statistical relationship of several whole blood viscosity parameters and cerebral blood flow (CBF) in 53 consecutive patients and normal controls. Significant correlations were present between CBF and serum fibrinogen (P = .05), hematocrit (P less than .05), and a relationship involving both fibrinogen and hematocrit (P less than .01). We conclude that heightened whole blood viscosity does correlate with decreased cerebral blood flow in the ranges measured in our patients, that both fibrinogen and hematocrit must be taken into consideration in viscosity determinations, and that changes in viscosity may have an important effect on CBF in regions of low flow.
The authors describe their experience concerning silent myocardial ischemia diagnosed by Holter monitoring technique, and present an update review about this issue. The new concepts of stunned and hibernated myocardium are analyzed, as well as the concepts of ischemic cascade, total ischemic burden and variable residual coronary reserve. Diagnostic methods and therapeutic decisions are also reviewed.
Tuberculous mesenteric lymphadenitis is a rare clinical entity and non-surgical diagnosis of this condition remains a challenge. A 38-year-old Indian woman presented with a six-week history of epigastric pain, low-grade fever and anorexia. Upper endoscopy showed a gastric ulcer of the posterior wall of the stomach. On CT scan there was a 8 cm abdominal mass involving the pancreatic body and tail and the endoscopic ultrasonography was also compatible with a cystic pancreatic tumor which had eroded into the stomach. An exploratory laparotomy was performed and the diagnosis of tuberculous mesenteric lymphadenitis was confirmed by bacteriological and histological examinations. Medical therapy was started after surgery. At 18 months she is asymptomatic and abdominal CT scan is normal. Tuberculosis of mesenteric lymph nodes usually raises serious diagnostic problems. A high grade of suspicion is necessary in order to perform a pre-operative diagnosis.
Prenatal diagnosis (PND) has assistencial, psychological and economical consequences; it is very important to evaluate cost effectiveness for the population. A prospective study was done (longitudinal and descriptive) on a population referred to Maternidade Dr. Alfredo da Costa, divided into two groups. Group one with PND performed on proper time and second group a PND procedure performed on a adequate time. The general characterization, indications for reference and consequences were evaluated. The conclusions are that the indications for reference were correct and the diagnosis was effective in 17% of patients. Social, economical levels and multiparity were the most important factors affecting adequate PND. However concerning the results, the termination of pregnancy was more performed on the group 1 and more abnormalities were seen on the newborns of group 2.