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Biomedical subjects

J R Logic

Publications and source records attributed to J R Logic.

At least 37 records · Page 2Linked to original sources
PubMed1979

Use of blood-pool imaging in evaluation of diffuse activity patterns in technetium-99m pyrophosphate myocardial scintigraphy.

It has been suggested that diffuse Tc-99m pyrophosphate precordial activity may be due to persistent blood-pool activity in routine delayed views during myocardial imaging. To answer this question, we reviewed myocardial scintigrams recorded 60--90 min following the injection of 12--15 mCi of Tc-99m pyrophosphate for the presence of diffuse precordial activity, and compared these with early images of the blood pool in 265 patients. Diffuse activity in the delayed images was identified in 48 patients: in 20 with acute myocardial infarction and in 28 with no evidence of it. Comparison of these routine delayed images with early views of the blood pool revealed two types of patterns. In patients with acute infarction, 95% had delayed images that were distinguishable from blood pool either because the activity was smaller than the early blood pool, or by the presence of localized activity superimposed on diffuse activity identical to blood pool. In those without infarction, 93% had activity distribution in routine delayed views matching that in the early blood-pool images. The usefulness of the diffuse TcPPi precordial activity in myocardial infarction is improved when early blood-pool imaging is used to exclude persistence of blood-pool activity as its cause. Moreover, it does not require additional amounts of radioactivity nor complex computer processing, a feature that may be of value in the community hospital using the technique to "rule out" infarction 24--72 hr after onset of suggestive symptoms.

Angina Pectoris↗
PubMed1977

Technetium-99m stannous pyrophosphate myocardial scintigraphy. Reliability and limitations in assessment of acute myocardial infarction.

Two hundred-three patients had -echnetium 99m (stannous) pyrophosphate myocardial scintigrams for the evaluation of chest pain and suspected acute myocardial infarction. In addition to routine imaging at 60--90 minutes after injection of the radio-pharmaceutical, the blood pool was imaged immediately in each patient for comparison with routine anterior, left anterior oblique, and left lateral views. Further delayed studies were obtained when residual blood pool activity was identified. Seventy patients had acute myocardial infarction by clinical, electrocardiographic, and enzymatic (CK-MB) criteria. Sixty-five of these 70 patients with acute infarction had positive myocardial scintigrams, with one technically unsatisfactory study. Only four of the 70 patients had negative scintigrams when imaged 18--72 hours after infarction in this study. Technically satisfactory scintigrams were recorded in 125 patients without evidence of infarction. Ninety-six had negative scintigrams at 60--90 minutes, while 19 patients (15%) had precordial activity at 60--90 minutes which was identical in distribution to early blood pool images and cleared with further delay. With these included, the true negative incidence was 92%. Ten of 125 patients had false positive scintigrams; two had recent cardioversion with resultant chest wall damage. The other eight patients had previous infarction 1 1/2 to 72 months earlier and had akinetic segments shown angiographically in the areas of the persistently positive scintigrams. Myocardial scintigraphy correlates well with the presence of other evidence of acute infarction, as well as with the absence of acute infarction when residual blood pool activity is identified. False positive scintigrams can occur following cardioversion and in patients with previous myocardial infarction and resultant ventricular wall motion abnormalities.

Acute Disease↗
PubMed1977

Visualization of atrial myocardium with thallium-201: case report.

An adult patient evaluated for cyanotic congenital heart disease was found to have pulmonary atresia with intact ventricular septum, hypoplastic right ventricle, and right atrial enlargement. Thallium-201 myocardial imaging before surgical correction showed thallium activity in the right atrium. Following the establishment of a conduit from the right atrium to pulmonary artery, the right-atrial thallium uptake was even more prominent.

Adult↗
PubMed1975

Rapid assessment of ventricular fibrillation thresholds during experimental infarction in the canine heart.

Sophisticated instrumentation is described which allows the rapid estimation of vulnerability of the ventricle to multiple responses and fibrillation with the classical technique described by Wiggers and Wegria. It seems particularly pertinent to the assessment of the significance of "R on T" type of ventricular extrasystoles in myocardial infarction. The thresholds to tachyarrhythmia were decreased by about 64% within 10 min of coronary occlusion and persisted at that level for 60-90 min, suggesting the usefulness of this model in assessing anti-fibrillatory drug regimes during the early evolutionary stage of myocardial infarction.

Animals↗
PubMed1975

Comprehensive evaluation of renal function in the transplanted kidney.

By means of a comprehensive renal function test based on the analysis of orthoidohippurate kinetics carried out 223 times in 86 renal transplatn patients, we have been able to separate clearly five clinical entities: normally functioning transplanted kidneys, acute tubular necrosis, cell-mediated rejection, humoral (chromin) rejection, and postrenal obstruction. Accurate prediction of the fate of the rejecting kidney can be made while still subclinical as much as a week before manifestations by other techniques are evident. Data on 22 donors studied 44 times are also presented. The comprehensive test consists of measurements of effective renal plasma flow (ERPF), sequential scintigraphy, calculations of excretory index (EI) (percent dose actually found in bladder and voided urine as a fraction of the percent dose expected at a given time after injection at the patient's specific ERPF), and residual urine volume. Formulas and regression equations for the calculation of ERPF, EI, residual urine, etc., are presented.

Female↗
PubMedDate not supplied

Antiarrhythmic anesthetic action I: the effect of halothane on canine intracardiac impulse conduction during sinus rhythm.

The effect of halothane on intracardiac impulse conduction was assessed in dogs before and after pharmacologic vagotomy. Impulse conduction was measured by anesthetic-related changes in the A-H and H-V intervals of the His bundle electrogram. Prior to vagotomy, both "light" and "deep" halothane prolonged the A-H interval significantly. Maximal A-H interval prolongations corresponded to the maximal decrease in heart rate with either dose of anesthetic. Following vagotomy, the A-H prolongation produced by light halothane was abolished and the prolongation produced by the deep level greatly reduced. Neither dose of halothane had a measurable effect on the H-V interval before or after vagotomy. In one animal in which the effects of increasing rates of atrial pacing were measured without the addition of halothane, the A-H interval lengthened with no measurable change in the H-V interval. In two dogs in which the heart rate was held near pre-halothane levels by atrial pacing, the A-H interval was slightly prolonged and the H-V interval unchanged during the administration of deep halothane. These studies indicate that during sinus rhythm: (1) halothane prolongs A-V impulse conduction, (2) that this effect is correlated with a concomitant decrease in heart rate, and (3) that these effects are largely dependent upon intact vagal innervation of the heart. During atrial pacing, A-V conduction is prolonged by increased heart rate or by deep halothane when the heart rate is held constant. Thus, in addition to the known effects of halothane on pacemaker automaticity, concomitant changes in conduction may contribute to the antiarrhythmic action of this anesthetic.

Anesthesia, Inhalation↗
PubMedDate not supplied

Conversion from cyclosporine to azathioprine following heart transplantation.

Eleven patients receiving cyclosporine were converted to azathioprine immunosuppression because of persistent creatinine elevation greater than 2 mg/dl 6 months or more following heart transplantation. During conversion, the maintenance steroid dose was doubled for 3 months then tapered to the preconversion dose. Pretransplant renal function in these converted patients was similar to that in a group of azathioprine patients and a group of nonconverted cyclosporine patients. One year following transplant, the nonconverted group had stable but impaired renal function (mean creatinine, 1.45 +/- 0.06 mg/dl; effective renal plasma flow, 407 +/- 39 ml/min; glomerular filtration rate, 68 +/- 8.8 ml/min). The converted patients had evidence of progressive renal dysfunction (mean creatinine, 2.65 +/- 0.19 mg/dl; effective renal plasma flow, 193 +/- 16 ml/min; glomerular filtration rate, 29 +/- 5.1 ml/min). Following conversion, renal function improved toward normal in all patients. There were three episodes of rejection that were successfully treated. An important number of infective and noninfective complications occurred following conversion during the period of steroid augmentation. There were two deaths during the follow-up period. Conversion can be undertaken with low risk of rejection, death, or both, but protocols that employ prolonged periods of steroid augmentation are associated with important morbidity.

Alabama↗