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Biomedical subjects

R W Brower

Publications and source records attributed to R W Brower.

At least 19 recordsLinked to original sources
PubMed1989

Increased serum levels of fibrinogen degradation products due to treatment with recombinant tissue-type plasminogen activator for acute myocardial infarction are related to bleeding complications, but not to coronary patency. European Co-operative Study Groups for rt-PA.

The association of increasing serum levels of fibrinogen degradation products after recombinant tissue-type plasminogen activator (rt-PA) therapy with bleeding and early coronary patency was assessed in 242 patients with acute myocardial infarction. After administration of 5,000 IU heparin, a median of 40 mg (range 35 to 60) of double chain rt-PA was given intravenously in 90 min. Bleeding occurred in 62 patients; in 73% of patients it was observed within the 1st 24 h and 84% of events consisted of hematoma or prolonged bleeding, or both, at puncture sites. Bleeding events occurred 2.12 times as often in patients with serum levels of fibrinogen degradation products greater than 85 mg/liter as in patients with serum levels less than 22 mg/liter (95% confidence interval 1.01 to 4.43). The infarct-related coronary vessel was patent in 65% of patients at 90 min after the start of rt-PA infusion. In patients with high serum levels of fibrin(ogen) degradation products, coronary patency at 90 min after the start of rt-PA infusion was not better (13% less, 95% confidence interval - 33%, 13%) than in patients with low serum levels. This uncoupling of thrombolytic effect in terms of coronary patency and systemic fibrinogenolysis confirms the experimentally demonstrated fibrin specificity of double chain rt-PA in human subjects. Because fibrin specificity of single chain rt-PA is at least similar to that of double chain rt-PA, the observations in this analysis most likely hold also for single chain rt-PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Coronary patency after intravenous infusion of recombinant tissue-type plasminogen activator in acute myocardial infarction.

The relation between coronary patency after infusion of recombinant tissue-type plasminogen activator (rt-PA) and clinical and laboratory findings was assessed in patients with acute myocardial infarction. This study focused primarily on information available early in the hospitalization phase. Data were available for 243 patients who received the full dose of rt-PA and who had assessable coronary angiograms 90 min after the start of the intravenous infusion. The infarct-related vessel was scored by an independent assessment committee as being patent in 65% of patients. The left anterior descending coronary artery was involved in 53% of patients, and proximal localization of the infarct-related vessel occurred in 65%. In the majority of patients (85%), the infusion was started within 4 h of the acute event. Neither the angiographic location of the infarct-related vessel nor electrocardiographic evidence of infarct severity or location appeared to have a bearing on thrombolysis with rt-PA. Multivariate logistic regression analysis identified three independent predictors of coronary patency: hematocrit 43 to 47%, blood plasminogen level greater than or equal to 90% of normal and serum alkaline phosphatase greater than or equal to 82% of the local upper normal limit. In addition, the use of intravenous nitrates suggests a positive association with patency.

Aged↗
PubMed1988

[Randomized double-blind study comparing tissue-type plasminogen activator with placebo in acute myocardial infarct].

In a double-blind randomised trial 129 patients with first myocardial infarction of less than 6 h duration were allocated to treatment with human recombinant tissue-type plasminogen activator (rt-PA) given intravenously over 90 min, or to placebo infusion. Coronary angiography at the end of this infusion showed that the infarct-related vessel was patent in 61% of 62 assessable coronary angiograms in the rt-PA-treated group compared with 21% in the control group. Treatment with rt-PA was not accompanied by any major complications. In the rt-PA group the circulating fibrinogen level at the end of the catheterisation was 52 +/- 29% (mean +/- SD) of the starting value.

Adult↗
PubMed1987

Acute coronary thrombolysis with recombinant human tissue-type plasminogen activator: initial patency and influence of maintained infusion on reocclusion rate.

An intravenous infusion of 40 mg of recombinant tissue-type plasminogen activator (rt-PA) was given intravenously over 90 minutes to 123 patients with acute myocardial infarction (AMI) of less than 4 hours' duration. A coronary angiogram was recorded at the end of the infusion in 119 patients. Central assessment of the angiograms revealed a patent infarct-related artery in 78 patients (patency rate 66%, 95% confidence limits 57 to 74%). Patients with a patent infarct-related artery at the first angiogram were randomized in a double-blind manner to receive a subsequent 6-hour infusion of either 30 mg of rt-PA or placebo. All patients had received an initial bolus of 5,000 IU of heparin and then 1,000 IU/hour until a second angiogram was recorded 6 to 24 hours after the start of the second perfusion. At central assessment of the second coronary angiogram the reocclusion rate was 2 of 36 patients who received rt-PA at the second infusion and 3 of 37 patients not receiving this drug (or the 2 groups combined 7%, 95% confidence limits 2 to 15%). Three of 60 patients (5%, 95% confidence limits 1 to 14%) with patent arteries on both previous angiograms had a later occlusion as judged on the angiogram recorded at hospital discharge. No difference in late reocclusion rates between the 2 treatment groups was observed.

Clinical Trials as Topic↗
PubMed1987

Effect of continued rt-PA administration on the residual stenosis after initially successful recanalization in acute myocardial infarction--a quantitative coronary angiography study of a randomized trial.

Quantitative angiography was performed in 68 out of 123 patients treated with intravenous rt-PA for acute myocardial infarction. At 90 min angiography, the median minimal cross-sectional area was 1.11 mm2 and the median percentage area stenosis was 80%. A percentage area stenosis greater than 70% was seen in 78% of the patients. Patients with a patient infarct related artery at the first angiogram were randomized to receive subsequent infusions either of rt-PA + heparin or placebo + heparin. There was a persistent trend of improvement in minimal lumen diameter and percentage diameter stenosis of the residual stenosis in the infarct related artery in both treatment groups when re-examined 6-24 hours later and at the time of hospital discharge. A reduction in 'plaque area', the area between the detected and the reference contours of the infarct related segment, was more frequently seen in patients receiving a second infusion of rt-PA than in patients with no prolonged thrombolytic therapy (83% versus 57%, P less than 0.025, chi square).

Cineangiography↗
PubMed1985

Double-blind randomised trial of intravenous tissue-type plasminogen activator versus placebo in acute myocardial infarction.

In a double-blind randomised trial 129 patients with first myocardial infarction of less than 6 h duration were allocated to treatment with human recombinant tissue-type plasminogen activator (rt-PA) given intravenously over 90 min, or to placebo infusion. Coronary angiography at the end of this infusion showed that the infarct-related vessel was patent in 61% of 62 assessable coronary angiograms in the rt-PA-treated group compared with 21% in the control group. Treatment with rt-PA was not accompanied by any major complications. In the rt-PA group the circulating fibrinogen level at the end of the catheterisation was 52 +/- 29% (mean +/- SD) of the starting value.

Adult↗
PubMed1985

Randomised trial of intravenous recombinant tissue-type plasminogen activator versus intravenous streptokinase in acute myocardial infarction. Report from the European Cooperative Study Group for Recombinant Tissue-type Plasminogen Activator.

In a single-blind randomised trial in patients with acute myocardial infarction of less than 6 h duration, the frequency of coronary patency was found to be higher after intravenous administration of recombinant human tissue-type plasminogen activator (rt-PA) than after intravenous streptokinase. 64 patients were allocated to 0.75 mg rt-PA/kg over 90 min, and the infarct-related coronary artery was patent in 70% of 61 assessable coronary angiograms taken 75-90 min after the start of infusion; 65 patients were allocated to 1 500 000 IU streptokinase over 60 min, and the infarct-related vessel was patent in 55% of 62 assessable angiograms. The 95% confidence interval of the differences ranges from +/- 30 to -2% (p = 0.054). Bleeding episodes and other complications were less common in the rt-PA patients than in the streptokinase group. Hospital mortality was identical in the 2 treatment groups. At the end of the rt-PA infusion the circulating fibrinogen level was 61 +/- 35% of the starting value, as measured by a coagulation-rate assay, and 69 +/- 25% as measured by sodium sulphite precipitation. After streptokinase infusion, corresponding fibrinogen levels were 12 +/- 18% and 20 +/- 11%. In the rt-PA group only 4.5% of the fibrinogen was measured as incoagulable fibrinogen degradation products, compared with 30% in the streptokinase group. Activation of the systemic fibrinolytic system was far less pronounced with rt-PA than with streptokinase.

Adult↗
PubMed1985

Aorto-coronary bypass surgery in 62 patients with severe left ventricular dysfunction--a follow-up study.

Long-term follow-up of 62 consecutive patients with severe left ventricular dysfunction (ejection fraction = less than 0.30) and disabling angina pectoris following aorto-coronary bypass surgery was investigated. Prior to surgery all patients had angina pectoris and a history of remote myocardial infarction, 35% were in congestive heart failure (CHF). Significant stenoses in 3 major coronary vessels were present in 51 patients (82%). An average of 3.5 grafts per patient were employed. Operative mortality (30 days) rate was 4.8% (3 patients) and 13 patients died during the following period. The average follow-up was 37 months (range: 6 to 116 months). At follow-up, the 5-year survival probability for these patients was 70% (SD = 9%). Thirty-one patients (67%) of the 46 survivors had complete relief of angina, but signs of CHF were still evident in 17 patients (36%). Compared to patients with ejection fractions above 0.30% (surgical mortality 1.4% and 5-year survival rate 94% (SD = 3%] the outcome of coronary artery bypass grafting in patients with poor left ventricular function showed a significantly higher surgical mortality (P = 0.03) and impaired long-term survival (P = 0.02). However, aorto-coronary bypass grafting can be performed in patients with severe left ventricular dysfunction with reasonable relief of angina and with an acceptable surgical mortality.

Adult↗
PubMed1985

Left ventricular function during transluminal angioplasty: a haemodynamic and angiographic study.

The response of left ventricular function, was studied in a series of patients undergoing percutaneous transluminal coronary angioplasty (PTCA). From 4 to 6 balloon inflations procedures per patient were performed with an average duration per occlusion of 51 +/- 12 sec (mean +/- SD), total occlusion time 252 +/- 140 sec. Analysis of left ventricular (LV) haemodynamics showed that the relaxation parameters peak negative rate of change in pressure and the early time constant of relaxation responded earliest to acute coronary occlusion while other parameters such as peak pressure, LV end-diastolic pressure, and peak positive rate of change of pressure responded more gradually and suggested a progressive depression in myocardial mechanics during the entire procedure. LV angiogram available in 14 patients indicate an early onset of asynchronous relaxation concurrent with the early response in peak -dP/dt and the time constant of early relaxation. All haemodynamic parameters fully recovered within minutes after the end of PTCA. The results of this study indicate no permanent dysfunction to global or regional myocardial mechanics, after PTCA with 4 to 6 coronary occlusions each lasting 40 to 60 seconds.

Angiography↗
PubMed1979

Left ventricular function and compliance in swine during halothane anesthesia.

Halothane (0.05--1.7 vol per cent end-tidal) in nitrous oxide (N2O), 60 per cent: oxygen (O2), 40 per cent was administered to nonmedicated, closed-chest pigs. Ventricular function was analyzed from cardiac output (thermodilution) and left ventricular (LV) pressure indices. Ventricular volumes and compliance were estimated from single and biplane LV angiography. In separate experiments, the effects of N2O, time, and the angiographic dye injections were shown to be minimal. Halothane caused dose-dependent decreases in aortic blood pressure, cardiac output, peak first derivative of left ventricular pressure (LV dP/dt), the in-vivo maximum velocity of fiber shortening (Vmax), and ejection fraction; non-dose-dependent decreases in heart rate and circumferential fiber shortening rate. Although a pronounced dose-related negative inotropic effect of halothane in the pig heart was demonstrated, there was no definite effect on ventricular pressure-volume relationships (compliance). If there was any such effect of halothane, it was obscured by the cardiac depression produced.

Animals↗
PubMed1979

[Regional myocardial shortening and blood flow through the graft after aorto-coronary bypass surgery].

In 56 patients operated on for coronary artery bypass grafting the relation between regional epicardial shortening, bypass flow, reactive hyperemia, and time postoperative was determined. Regional shortening in the newly perfused region was measured by a new technique employing four to six radiopaque markers sutured in pairs to the epicardium juxtaposed by 2 cm, and from 0 to 3 cm distal to the coronary anastomosis. Marker pairs were filmed sequentially at each follow up. Excluding dyskinesia, shortening fraction (ratio of shortening to maximum marker separation) for all graft regions at 1 week was 9.8 p. 100, 1 month 12.8 p. 100, 3 months 13.3 p. 100, and 6 months 13.9 p. 100. Average graft flow was 56 ml/mn and average reactive hyperemia was 25 p. 100 with 37 p. 100 of grafts having no response. There was a positive correlation between shortening fraction and flow, becoming significant (null hypothesis: r = 0) when reactive hyperemia exceeded 20 p. 100. Correlation was greatest at 1 week and 1 month, but became non-significant at 6 months implicating other factors such as new collateral development, bypass closure, new infarction, or altered medical therapy. It appears that bypass flow and reactive hyperemia do have a certain predictive value as to regional shortening up to 1 to 3 months postoperative.

Adult↗
PubMed1979

Regional myocardial shortening in relation to graft-reactive hyperemia and flow after coronary bypass surgery.

Extent of regional shortening of myocardium in areas newly perfused by bypass grafting was determined in 56 patients by a new technique employing four to six radiopaque markers sutured in pairs to the epicardium near the coronary anastomosis. Paradoxical systolic expansion (PSE) was manifest in 16 regions (a 12% incidence) during the follow-up period, and six of these showed spontaneous remission. All cases of PSE were in the region of the left anterior descending artery. Correlation between graft flow measured during operation and regional shortening during the postoperative period revealed that the development of PSE could not be predicted from the hemodynamic measurements. In the majority of cases postoperative myocardial infarction could also be excluded as an explanation. At 1 year after operation most grafts were patent in PSE regions but collaterals, apparent preoperatively, could not be visualized. Excluding PSE, shortening fraction (ratio of shortening to maximum marker separation) for all graft regions at 1 week was 9.8%; 1 month, 12.8%; 3 months, 13.3%; and six months, 13.9%. Average graft flow was 56 ml. per minute and average reactive hyperemia was 25% with 37% of grafts showing no response. For those regions that did not develop PSE there was a positive correlation between shortening fraction and flow that became significant (null hypothesis: r = 0) when reactive hyperemia exceeded 20%. Correlation was greatest at 1 week and 1 month, but became nonsignificant at 6 months. These results are consistent with a simple interpretation of reactive hyperemia: Graft-reactive hyperemia is related to the dependence of viable tissue on the functioning of the graft.

Adult↗
PubMed1978

Direct method for determining regional myocardial shortening after bypass surgery from radiopaque markers in man.

A new method is described for determining localized epicardial shortening in regions newly perfused after saphenous vein bypass grafting. Four to six radiopaque markers are sutured to the ventricular epicardium in pairs, 2 cm apart and 0 to 3 cm distal to the coronary anastomosis. Shortening fraction and time to onset of shortening are reported in 56 patients examined noninvasively with use of cinefluorography 1 week to 6 months after operation. The right coronary bypass region showed the greatest improvement in shortening fraction in 6 months (from 10.1 to 16.7 percent); the left anterior descending region showed the least (but still significant) improvement (from 8.6 to 11.5 percent). Paradoxical systolic expansion occurred predominantly in the region of the left anterior descending coronary bypass (95 percent of all such occurrences). Measurement error, observer variability and beat to beat variability were less important than the physiologic changes in the postoperative period. This technique is a direct method providing heretofore unavailable follow-up information on localized shortening in newly perfused myocardium after coronary bypass grafting.

Adult↗
PubMed1977

Automatic data processing in the cardiac catheterization laboratory.

A review of automatic data processing in the cardiac catherization lab is presented. The emphasis placed on on-line manometry, indicator dilution and off-line quantitative ventriculography. The system organization is described and several specific examples given to illustrate the level of detail necessary to specify such a system. The clinical use of the system is described together with an evaluation of the original design goals in terms of the actual performance of the system. A few unexpected benefits have emerged with respect to quality control and reliability, but one of the original design goals, speeding up the catheterization procedure, has proven to be unrealistic. The next logical steps in the software and hardware evolution are described with the emphasis placed on making the system a more effective tool for the clinician.

Cardiac Catheterization↗
PubMed1977

Myocardial radiopaque markers used to quantify minor axis shortening for follow-up studies in experimental surgery. I. Recording and analysis techniques. II. Comparison with contractility indices.

This work further validates the use of radiopaque epicardial marker motion for quantifying myocardial shortening in long duration follow-up studies. Mean velocity and extent of minor axis shortening were determined in 8 dogs filmed daily for 6--10 days postoperative. As an independent measure of contractility, peak dP/dt was also determined. A useful approximation to the mean ejection slope was developed which uses the end diastolic minor axis 50 msec after the Q wave, and end systolic minor axis 150 msec after the Q wave of the ECG.

Animals↗