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Biomedical subjects

R Roberts

Publications and source records attributed to R Roberts.

At least 307 records · Page 17Linked to original sources
PubMed1990

An accurate, nontraumatic ultrasonic method to monitor myocardial wall thickening in patients undergoing cardiac surgery.

Measurement of systolic wall thickening by sonomicrometry provides an accurate index of regional left ventricular function, but the trauma of crystal insertion limits its widespread clinical use. The first clinical application of a 10 MHz ultrasonic Doppler probe that can be either sutured or applied by suction to the epicardium and can measure wall thickening at any depth of the left ventricular wall is described. In 18 dogs, measurements obtained with the suction probe correlated well (r = 0.97) with those of a previously validated sutured probe. To assess clinical feasibility, the probe was applied to the epicardium of patients undergoing coronary bypass surgery. Good quality wall thickening signals were obtained with no complications. Transmural left ventricular thickening fraction before bypass surgery was 34 +/- 3% (mean value +/- SE) at the mid-ventricular lateral wall, 33 +/- 4% at the anterior basal wall and 26 +/- 4% at the mid-ventricular posterior wall. Right ventricular thickening fraction averaged 25 +/- 3%. Endocardial thickening fraction tended to exceed epicardial thickening fraction, although the difference attained statistical significance (p less than 0.05) only at the anterior basal wall. On average, thickening fraction during the immediate postoperative period remained unchanged compared with the preoperative values, but a marked individual variability was observed, with 7 of 15 patients exhibiting a decrease and 8 an increase. Exteriorization of the wires attached to the sutured probe allowed continuous in situ monitoring of wall thickening in the postoperative period and subsequent removal of the probe. In six patients the crystal was left in place for 48 to 72 h after surgery and then removed without complications; good wall thickening signals were obtained for the entire period during which the probe was implanted. Thus, the Doppler probe is an accurate, atraumatic method for measuring right and left ventricular regional function. Transmural, endocardial and epicardial function can be mapped at various sites during surgery, and post-operatively one can monitor serial changes of regional function and assess the effects of cardioplegia and other therapeutic interventions. This technique should be useful for both investigative and clinical purposes.

Adult↗
PubMed1990

Quantitative exercise thallium-201 single photon emission computed tomography for the enhanced diagnosis of ischemic heart disease.

The clinical utility of exercise thallium-201 single photon emission computed tomography was investigated in 360 consecutive patients who had concomitant coronary arteriography. Tomographic images were assessed visually and from computer-quantified polar maps. Sensitivity for detecting coronary artery disease was comparably high using quantitative and visual analysis, although specificity tended to improve using the former method (87% versus 76%, p = 0.09). Quantitative analysis was superior to the visual method for identifying left anterior descending (81% versus 68%, p less than 0.05) and circumflex coronary artery (77% versus 60%, p less than 0.05) stenoses and detected most patients (92%) with multivessel coronary artery disease. Multivessel involvement was correctly predicted in 65% of the patients with more than one critically stenosed vessel. Exercise variables in patients with significant coronary artery disease were similar whether the tomographic images were normal or abnormal. However, patients with coronary stenoses and normal versus abnormal tomograms had a trend toward more single vessel disease (79% versus 62%, p = 0.07) and moderate coronary stenosis (66% versus 28%, p less than 0.001), but had less proximal left anterior descending artery involvement (8% versus 34%, p = 0.05). Computer-quantified perfusion defect size was directly related to the extent of coronary artery disease. Intra- and interobserver agreement for quantifying defects were excellent (r = 0.98 and 0.97, respectively). In conclusion, quantitative thallium-201 tomography offers improved detection of coronary artery disease, localization of the anatomic site of coronary stenosis, prediction of multivessel involvement and accurate determination of perfusion defect size, while maintaining a high specificity. Quantification of perfusion defects with single photon tomography may become important for assessing the effects of coronary reperfusion and prognostically stratifying patients with coronary artery disease.

Aged↗
PubMed1990

Effect of human recombinant superoxide dismutase on canine myocardial infarction.

To determine whether human recombinant superoxide dismutase (h-SOD) produces sustained reduction of infarct size, anesthetized dogs underwent a 2-h coronary occlusion followed by either 48 or 4 h of reperfusion. In the 48-h study, dogs were randomized to three intravenous treatments: 1) "low-dose" h-SOD (2 mg/kg bolus 2 min before reperfusion followed by 4 mg/kg over 45 min), 2) "high-dose" h-SOD (8 mg/kg bolus 2 min before reperfusion followed by 8 mg/kg over 45 min), or 3) equivalent volumes of saline. In the 4-h study, dogs were randomized to high-dose h-SOD or saline. Occluded bed size was measured by postmortem perfusion and infarct size by triphenyl tetrazolium chloride staining and planimetry. Investigators performing the study and measuring infarct size were blinded to the treatment given. High plasma concentrations of h-SOD were present in the arterial blood of treated dogs in the early phase of reperfusion (greater than 60 and greater than 180 micrograms/ml in low- and high-dose groups, respectively). In both studies, control and treated groups were similar with respect to occluded bed size, collateral blood flow, and rate-pressure product during ischemia. In the 48-h study, infarct size, expressed as percent of occluded bed size, was 41.3 +/- 7.6% (mean +/- SE) in the control group, 37.1 +/- 7.2% in the low-dose h-SOD group, and 48.0 +/- 7.1% in the high-dose h-SOD group. In the 4-h study, infarct size was 30.6 +/- 4.9% in the control group and 31.5 +/- 9.6% in the high-dose h-SOD group. Analysis of the flow-infarct relationships confirmed that h-SOD did not reduce infarct size at any level of collateral flow in either the 48- or 4-h study. Recovery of regional myocardial function after reperfusion was also unaffected by h-SOD in both studies. Thus in this randomized blinded study, large doses of h-SOD given at the time of reperfusion failed to limit infarct size or enhance recovery of function, both early (4 h) and late (48 h) after reperfusion following a 2-h coronary occlusion.

Animals↗
PubMed1990

Lack of diurnal variation in the onset of non-Q wave infarction.

Data concerning the time of onset of myocardial infarction were obtained for 540 of the 544 patients with creatinine kinase (CK)-MB-confirmed non-Q wave myocardial infarction enrolled in the multicenter Diltiazem Reinfarction Study. Data were also collected for 627 patients who were screened but excluded. Among the 1,167 patients, no diurnal pattern of onset could be found at either 2- or 6-hour intervals. Among the 540 patients enrolled in the trial, no pattern could be found at these intervals either, although at 8-hour intervals, 27% of infarctions occurred between midnight and 8:00 AM, compared with 37% between 8:00 AM and 4:00 PM and 36% between 4:00 PM and 12:00 AM (p = 0.02). In contrast to the patterns previously noted for Q wave myocardial infarction, there was no preponderance of non-Q wave infarction in the late morning. Circadian rhythm was also absent among patients not treated with beta-blockers as well as among patients presenting with ST segment elevation on their enrollment electrocardiograms. Diabetics, women, and patients with first infarction were more likely to present during the afternoon hours. We conclude that the late morning preponderance seen for Q-wave myocardial infarction is not discernable in patients with non-Q wave myocardial infarction. This observation suggests that the pathogenesis of these two infarct subtypes is different or that the process of thrombotic coronary occlusion in Q wave infarction (sustained) differs from that in non-Q wave infarction (nonsustained).

Adrenergic beta-Antagonists↗
PubMed1990

Comparison of immediate invasive, delayed invasive, and conservative strategies after tissue-type plasminogen activator. Results of the Thrombolysis in Myocardial Infarction (TIMI) Phase II-A trial.

To assess the value and timing of percutaneous transluminal coronary angioplasty (PTCA) after thrombolytic therapy for acute myocardial infarction (AMI), 586 patients in the Thrombolysis in Myocardial Infarction Study Phase II-A were randomized among three treatment strategies, one using immediate coronary arteriography followed by PTCA if appropriate (immediate invasive strategy group, n = 195), a second that deferred angiography and PTCA for 18-48 hours (delayed invasive strategy group, n = 194), and a third, more conservative, approach in which PTCA was used only if ischemia occurred spontaneously or at the time of predischarge exercise testing (conservative strategy group, n = 197). Predischarge contrast left ventricular ejection fraction, the primary study end point, was similar among the patients in all three treatment groups and averaged 49.3%. The finding of a patent infarct-related artery at the time of predischarge arteriography was equally common among the patients in the three groups (mean, 83.7%); however, the mean residual infarct artery stenosis was greater in the patients in the conservative strategy group (67.2%) as compared with the patients in the immediate invasive (50.6%) and the delayed invasive strategy groups (47.8%) (p less than 0.001). Immediate invasive strategy led to a higher rate of coronary artery bypass graft surgery (CABG) after PTCA (7.7%) than did delayed invasive and conservative strategies (2.1% and 2.5%, respectively; p less than 0.01). Furthermore, among patients not undergoing CABG during the first 21 days, blood transfusion of more than 1 unit was used in 13.8% of the patients in the immediate invasive strategy group, 3.1% of the patients in the delayed invasive strategy group, and 2.0% of the patients in the conservative strategy group (p less than 0.001). At 1-year follow-up, the three treatment groups had similar cumulative rates of mortality (8.7%, pooled over all groups), fatal and nonfatal reinfarction (8.5%), combined death and reinfarction (14.5%), and CABG (17.2%), although the cumulative performance rate of PTCA remained higher in the invasive groups (immediate invasive strategy group, 75.8%; delayed invasive strategy group, 64.3%; and conservative strategy group, 23.9%; p less than 0.001). Thus, because conservative strategy achieves equally good short- and long-term outcome with less morbidity and a lower use of PTCA, it seems to be the preferred initial management strategy.

Aged↗
PubMed1990

Intravenous recombinant tissue-type plasminogen activator in patients with unstable angina pectoris. Results of a placebo-controlled, randomized trial.

Because thrombus formation may contribute to coronary obstruction in patients with unstable angina pectoris, we performed a pilot investigation to determine whether thrombolytic therapy can relieve coronary narrowing in this acute ischemic syndrome. Sixty-seven patients with rest angina and angiographic evidence of coronary stenosis were randomly assigned to receive either low-dose intravenous recombinant tissue-type plasminogen activator (rt-PA) (0.75 mg/kg over 1 hour), high-dose intravenous rt-PA (0.75 mg/kg over 1 hour; total dose, 100 mg over 6 hours), or intravenous placebo followed by repeat coronary angiography at 24-48 hours to assess change in the severity of coronary narrowing. Each patient also received oral aspirin and intravenous heparin. Mean values of coronary stenosis severity (percent of diameter reduction) declined to a similar extent in each group: placebo, 75 +/- 14% to 72 +/- 14% (p = 0.07); low-dose rt-PA, 75 +/- 16% to 71 +/- 18% (p = 0.03), and high-dose rt-PA, 82 +/- 11% to 77 +/- 17% (p = 0.18), with only the low-dose rt-PA group achieving statistical significance. Resolution of intracoronary filling defects, increase in antegrade flow grade, or both also occurred equally among the three groups. There was considerable variation in individual patient response. Between 29% and 50% of patients within each group demonstrated a decrease in stenosis severity, whereas 50% to 57% noted either improvement in antegrade flow or resolution of intracoronary thrombus. There was no difference in incidence of major bleeding events among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Early diagnosis of acute myocardial infarction based on assay for subforms of creatine kinase-MB.

Thrombolytic therapy for patients with acute myocardial infarction (AMI) has produced the need for an accurate early diagnostic marker. We previously developed and assessed an assay for the creatine kinase (CK)-MB subforms; assay time is 25 minutes. Plasma MB2 (tissue subform) activity, MB1 (plasma-modified subform) activity, and MB2/MB1 ratio in 56 healthy individuals were 0.61 +/- 0.33 units/l, 0.63 +/- 0.33 units/l, and 0.94 +/- 0.39, respectively. Only one individual had both an MB2 activity greater than 1.0 units/l and an MB2/MB1 ratio of more than 1.5. Similar results were obtained in 50 hospitalized patients without cardiac disease; two of these patients had both an MB2 activity and an MB2/MB1 ratio greater than the cutoff values. Among 49 patients with AMI, MB2 activity and the MB2/MB1 ratio began to increase 2 hours after AMI; the ratio reached a plateau of 3.1 by 4-6 hours. The first available plasma sample was abnormal by the subform assay in 67% of patients and by a conventional MB assay in 27% of patients. Assay sensitivities in samples collected at 2-4, 4-6, and 6-8 hours after AMI were 59%, 92%, and 100% for the subform assay and 23%, 50%, and 71% for the conventional assay (p less than 0.03 versus subform assay at each time interval). False-negative results were obtained by the subform and conventional assays in 15 and 45 samples at a mean of 2.3 and 5.8 hours, respectively. Subform assay provides rapid and reliable diagnosis of AMI within 4-6 hours after the onset of symptoms, which is 6 hours before conventional CK-MB assays are accurate.

Creatine Kinase↗
PubMed1990

Rotec Theory: planning tool to position hospitals on the technology curve.

The mission statement of a prominent California hospital has been revised as part of a strategic planning process less than two years before the hospital began experiencing substantial financial difficulties. When the "red numbers" began to appear, management was quick to blame changing demographic patterns and the competitive environment. Those were not the only problems. A major contributing factor that management failed to recognize was a delay in how quickly the hospital moved to adopt high technology or new medical procedures. In a few short years, it had changed from being the first community hospital to implement state-of-the-art programs to one that was slow to introduce technology. In retrospect, the hospital's mission statement did not address the role of technology and therefore it could not detect the movement away from one of its critical success factors. The Rotec Theory was developed to assist this hospital to understand the economics of technology on its current and planned operations.

Cost-Benefit Analysis↗
PubMed1990

Endocarditis in intravenous drug abusers.

IE due to parenteral drug use is an ever-increasing problem for physicians working in the ED. IE may present with a multitude of signs and symptoms of variable severity. Patients may complain of only vague symptoms consistent with a viral syndrome, or they may present with a neurologic or cardiovascular catastrophe. ED physicians must have a high degree of suspicion for IE whenever they evaluate a patient who could possibly be abusing drugs.

Ambulatory Care↗
PubMed1989

Nuclear magnetic resonance imaging of acute myocardial infarction within 24 hours of chest pain onset.

The present study was intended to establish the feasibility, safety and usefulness of conventional spin-echo nuclear magnetic resonance (NMR) imaging for the detection of acute myocardial infarction within 24 hours of the onset of chest pain. Monitoring facilities were established in the NMR imaging suite that provided the same level of reliability and safety found in a standard coronary care unit. An imaging protocol was developed that allowed the acquisition of a complete study in 30 minutes while providing useful information about mechanical function and myocardial tissue contrast. Eighteen postthrombolysis patients were imaged within 21 +/- 2 hours of chest pain onset. No patient developed recurrent chest pain or arrhythmias in the NMR imaging suite. Relatively T2-weighted spin-echo images (echo time = 60 ms; repetition time = heart rate) provided interpretable images in 16 patients. Fourteen normal subjects were imaged for comparison. Thirteen of 16 patients had an increase in signal intensity in the region of the infarction. Regional wall thickening was assessed using a floating endocardial centroid technique. Wall motion abnormalities detected by NMR corresponded to those noted by 2-dimensional echocardiography and contrast angiography. Sensitivity, specificity and accuracy for the detection of infarction were 93, 80 and 87%, respectively, when signal intensity and wall thickening abnormalities were combined. In summary, NMR imaging is feasible in patients with acute myocardial infarction within 24 hours of chest pain onset. The study can be conducted safely and it provides useful information about acute myocardial infarction.

Adult↗