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Biomedical subjects

B G Brown

Publications and source records attributed to B G Brown.

At least 91 records · Page 5Linked to original sources
PubMed1987

Percutaneous transluminal coronary angioplasty and subsequent restenosis: quantitative and qualitative methodology for their assessment.

Coronary arteriography is the most commonly used technique for documenting the immediate percutaneous transluminal coronary angioplasty result and for follow-up of the dilated arterial segment for restenosis within 6 months (which occurs in about 25% to 35% of cases). Acute success in dilation of the coronary lesion is likely if there is at least a resultant 1.3 mm2 minimum lumen area, equivalent to a 1.3 mm mean minimum lumen diameter, or about a 50% diameter stenosis of a typical proximal vessel. The measurement methods applied to this problem include a digital caliper, computer-assisted border recognition techniques and a video-densitometric approach to estimation of lumen area. Calipers are recommended because of their simplicity, precision and accuracy for the routine assessment of angioplasty result. Border-recognition techniques require considerable operator input to distinguish true flow channels from cul de sacs in the dissected segment. The automated scanning videodensitometry approach has theoretical appeal and has shown promise in preliminary reports; however, there is the potential for large measurement errors in the setting of dissection. Further, certain qualitative morphologic features of the dilated segment, such as longitudinal or transverse dissection or intraluminal thrombus, may effectively contribute to the prediction of acute complications and may be useful predictors of late restenosis. Because these features are best appreciated at increased arteriographic magnification, further high resolution studies will be necessary to better understand their importance.

Angiography↗
PubMed1987

Usefulness of recanalization to luminal diameter of 0.6 millimeter or more with intracoronary streptokinase during acute myocardial infarction in predicting "normal" perfusion status, continued arterial patency and survival at one year.

To determine whether arteriographic dimensions of the acutely recanalized coronary lumen provide information about regional perfusion or clinical outcome, quantitative arteriography was used to measure minimum luminal diameter achieved with intracoronary streptokinase administration in 44 patients with acute myocardial infarction (AMI). Degree of coronary reperfusion was independently assessed visually using the criteria applied in the multicenter Thrombolysis in Myocardial Infarction study. Minimum diameter and qualitative reperfusion grade were both assessed from 172 coronary injections during thrombolysis. Partial perfusion (grade 1 or 2) was seen in 95 of 135 injections (70%) in which the minimum diameter was less than 0.6 mm and complete perfusion (grade 3) was seen in 35 of 37 injections (95%) in which it was 0.6 mm or more (p less than 0.001). Repeat cardiac catheterization was performed at 5.5 +/- 4.9 weeks after AMI (n = 20). When vessels were opened acutely to a minimum diameter of less than 0.6 mm, 5 of 12 vessels (42%) were reoccluded at the time of restudy and 8 of 29 patients (28%) died within 12 months. By contrast, 0 of 8 vessels (0%) were reoccluded when the artery was opened to a diameter of at least 0.6 mm (difference not significant), and only 1 of 15 patients (7%) died (p less than 0.05). Of the patients with grade 1 o r 2 perfusion at the end of the thrombolytic infusion, 7 of 19 (37%) died within 12 months and 2 of 4 vessels (50%) reoccluded; of the patients with grade 3 perfusion, 2 of 25 (8%) died (p less than 0.05) and 2 of 16 vessels (13%) reoccluded (difference not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Evaluation of antiplatelet agents in the prevention of aorto-coronary bypass occlusion.

The cumulative occlusion rates of aorto-coronary artery venous bypass grafts average from 16 to 26% per distal anastomosis within 12 months and about 2% per following year. The potential benefit of oral anticoagulants and platelet inhibitor drugs has been tested to prevent graft occlusion and to retard the atherosclerotic process. Oral anticoagulants started on the third postoperative day do not significantly reduce graft occlusion after 6 months. Among the platelet inhibitor drugs, dipyridamole started before surgery, followed by dipyridamole and aspirin soon after surgery, was the drug regimen with the best results. More randomised double-blind clinical trials are highly desirable to confirm these findings and to resolve the question of relative efficacy and safety for the various drugs reported to have shown benefit when used in combination.

Administration, Oral↗
PubMed1986

Molecular genetics of apolipoproteins and coronary heart disease.

A variety of DNA markers for apolipoprotein genes were examined among patients with angiocardiographically proven heart disease and among a variety of normal individuals with various lipid values. An increased frequency of an apoAI-CIII SstI RFLP and an apoB minisatellite (allele 5) was found among patients with CHD. Higher levels of cholesterol were found among carriers of the rare apoB TaqI and the common apoCII TaqI variants, whereas higher levels of triglycerides were found in carriers of the common apoAII MspI and the rare apoB XbaI variants. Lower levels of HDL were found among carriers of the common apoAII MspI and the rare apoB PvuII variants. The biological significance of these results and those of other investigators for the pathogenesis of CHD and hyperlipidemia is suggestive but not yet fully clarified. Additional genetic epidemiologic studies and family investigations will be required. Currently used statistical methodology may lead to false inferences regarding the genetic equilibrium or disequilibrium status of closely linked DNA variants. Conclusions regarding the presence of genetic equilibrium if closely linked flanking markers are in disequilibrium may be faulty.

Alleles↗
PubMed1986

Incomplete lysis of thrombus in the moderate underlying atherosclerotic lesion during intracoronary infusion of streptokinase for acute myocardial infarction: quantitative angiographic observations.

Thrombolytic recanalization of the obstructed coronary lumen was studied in 32 patients receiving intracoronary streptokinase for 60 to 90 min during acute myocardial infarction. The process was viewed at high arteriographic magnification and was quantified with computer-assisted measurements from repeated single-plane views. The variability of the method for this application was 0.15 to 0.18 mm on minimum diameter estimates. Structural details were seen that are not commonly appreciated at conventional magnification. The recanalized lumen appears to form along an interface between the thrombus and the vessel wall, progressively enlarging its minimum arteriographic diameter to 0.65 +/- 0.24 mm (+/- 1 SD) at the end of the short-term infusion of streptokinase reflecting a final percent stenosis of 77 +/- 10%. In nine infarct lesions found patent 5 +/- 3 weeks later, the recanalized lumen further improved an average of 0.34 mm in minimum diameter (p less than .005) and 13% stenosis (p less than .01). A thin film of contrast medium surrounding the obstructing thrombus faintly defined the boundaries of the original atherosclerotic lumen in all but two cases. The "original stenosis" measured 1.25 +/- 0.32 mm in minimum diameter and 56 +/- 14% stenosis when first visualized; it was unchanged throughout the course of infusion of streptokinase. In five patients catheterized 10 +/- 12 weeks before their infarction, the original stenosis averaged 1.15 +/- 0.22 mm in the preinfarct angiogram, as compared with 1.17 +/- 0.23 mm in its faintly defined form during thrombolytic therapy (p = NS). In 10 cases, this original lesion was less than a 50% stenosis, and in 21 cases less than 60%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Hyperemic myocardial perfusion imaging for noninvasive detection of coronary disease in man: comparison of treadmill exercise and intravenous dipyridamole infusion.

To further understand hyperemic myocardial perfusion imaging, the effects of exercise and intravenous dipyridamole on coronary flow, coronary stenosis luminal area, stenosis flow resistance, and regional myocardial perfusion were evaluated in patients with arteriographically documented coronary artery disease. Coronary hemodynamics were assessed in 24 patients undergoing routine diagnostic catheterization. Coronary flow was measured by coronary sinus thermodilution. Computer assisted stenosis measurements were made. During isometric handgrip coronary sinus flow increased to 1.7 X baseline value, and epicardial coronary arteries constricted to increase predicted stenosis flow resistance by 40%. A 4-minute intravenous dipyridamole infusion (0.56 mg/kg) increased coronary sinus flow to 2.4 X baseline with, on average, no change in the stenotic coronary lumen diameter. During simultaneous isometric handgrip and dipyridamole infusion coronary sinus flow increased to 3.3 X baseline value and stenosis flow resistance increased an average of 36%. Regional myocardial perfusion was assessed in 33 patients by thallium201 myocardial perfusion imaging following maximal treadmill exercise and again following intravenous dipyridamole infusion. Regional thallium201 imaging effects were correlated with measurements of angiographic coronary disease. Sensitivity and specificity for detecting a greater than or equal to 50% stenosis were 85% and 64% (p less than .005), respectively, for dipyridamole and 84% and 68% (p less than .005) for exercise thallium201. In summary, coronary blood flow increases with isometric exercise and is near maximal following intravenous dipyridamole. Quantitative arteriographic techniques demonstrate isometric exercise-induced constriction of coronary stenoses and increased stenosis flow resistance. Stenosis flow resistance increases following intravenous dipyridamole only for severe (greater than or equal to 65%) lesions. Treadmill exercise and intravenous dipyridamole are comparably effective hyperemic stimuli for creating regional perfusion differences for the noninvasive detection of coronary disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Circulation↗
PubMed1985

Response of normal and diseased epicardial coronary arteries to vasoactive drugs: quantitative arteriographic studies.

Coronary vasodilators known to be effective in effort and vasospastic angina were studied in 93 patients undergoing catheterization for evaluation of chest pain. The ischemia-provoking stresses were isometric handgrip (25% of maximum for 4 to 5 minutes) or ergonovine maleate (0.2 mg intravenously). Hemodynamic changes and changes in angiographic diameter of epicardial coronary arteries were measured during these stresses, with and without drug administration. Drugs included intravenous diltiazem (0.25 mg/kg load + 0.003 mg/kg/min), intravenous verapamil (0.14 mg/kg load + 0.0075 mg/kg/min) and intracoronary (0.012 mg/min X 4 minutes) and sublingual (0.4 mg) nitroglycerin. From these studies, the following statistically valid conclusions were reached. First, nitroglycerin is a potent dilator of epicardial coronary arteries, increasing normal luminal area an average of 28% and luminal area in significantly stenotic segments by 29%. Second, verapamil and diltiazem are nonsignificant epicardial coronary dilators (9% and 4% luminal area increase, respectively). Similarly, diltiazem does not dilate significant coronary stenoses. Third, sustained isometric handgrip increases systemic blood pressure and heart rate by reflex activation of the sympathetic nervous system. By this means, handgrip also constricts luminal area in normal and diseased coronary segments by 20% and 22%, respectively. One result of these changes is a handgrip-induced, ischemic 56% rise in pulmonary wedge pressure in patients with significant stenosis. Fourth, intracoronary nitroglycerin, in very small doses, does not block the systemic hemodynamic response to handgrip, but prevents handgrip-induced coronary constriction and the associated ischemic left ventricular dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Arterial Occlusive Diseases↗
PubMed1985

Coronary artery dilation and hemodynamic responses after isosorbide dinitrate therapy in patients with coronary artery disease.

The response to sublingual isosorbide dinitrate (ISDN) was studied in 10 men with suspected coronary artery disease undergoing coronary arteriography. A Swan-Ganz catheter was placed in the pulmonary artery to record hemodynamic response. Diseased coronary segments were identified during routine Judkins selective coronary angiograms. Sublingual isosorbide dinitrate (ISDN) (5 or 10 mg) was then given with the catheters in place. Multiple sequential single-view coronary angiograms and pulmonary and systemic hemodynamic responses were recorded over 30 minutes after drug administration. At 30 minutes, there was a 53% reduction (p less than 0.01) in pulmonary capillary wedge pressure and a 15% decrease (p less than 0.05) in systemic and pulmonary vascular resistance, with a net 13% decrease (p less than 0.01) in cardiac output and 20% decrease (p less than 0.01) in mean arterial pressure. Quantitative arteriography demonstrated substantial dilation of luminal cross-sectional area in both normal and diseased coronary arterial segments. Normal epicardial segments were grouped according to luminal area (1 to 4, 4 to 8 and more than 8 mm2) and demonstrated maximal area dilation at 10 minutes of 55% (p less than 0.01), 29% (p less than 0.01) and 16% (p less than 0.05), respectively. Diseased epicardial segments (stenosis 50% or greater) dilated 51% (p less than 0.01) at 10 minutes. Calculated stenosis resistance decreased 40% (p less than 0.01). Diseased segments in small and middle-sized arteries (1 to 8 mm2) are 4 times more reactive than those in larger arteries (more than 8 mm2), with peak dilation of 77 vs 21% (p less than 0.01) at 30 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1985

Preparation for barium enema: comparison of a commercial formula diet and low-residue, clear-liquid diets in inpatients.

The barium enema examination is the most frequently done initial diagnostic evaluation for disease of the lower gastrointestinal tract. Adequate preparation of the colon is essential because inadequate preparation necessitates repetition, with patient discomfort, decreased caloric intake, and increased cost. A formula diet (Ensure) has been reported as superior to the usual low-residue, clear-liquid diet for bowel preparation. We evaluated the feasibility of using this formula diet in a general medical inpatient population. We found no significant difference in the quality of preparation (72% and 76% optimal or adequate preparation, respectively) for our inpatient population. The formula diet has several theoretical advantages, including a greater number of calories, lower cost, and better patient acceptance.

Barium Sulfate↗
PubMed1985

Improved graft patency in patients treated with platelet-inhibiting therapy after coronary bypass surgery.

One hundred forty-seven consecutive coronary bypass patients were enrolled in a randomized, double-blind, risk-stratified, placebo-controlled prospective trial evaluating the effect on graft patency of 325 mg tid aspirin (ASA) plus 75 mg tid dipyridamole (DP) or ASA alone. One hundred twenty-seven patients (399 total grafts) underwent surgery, initiation of drug therapy 67 +/- 27 (SD) hr postoperatively, five clinic visits, and repeat angiography at 1 year. A logistic regression statistical model was used to determine the effects of 28 different measured variables on graft patency and to adjust for these effects in determining the relationship between antiplatelet therapy and graft occlusion. No patient-specific variable contributed significantly to the prediction of occlusion in either the placebo or the treated group. Six graft-specific variables (arterial diameter, severity of stenosis, graft flow, reactive hyperemia, presence or absence of collaterals, and graft type) did contribute and were included in the model. Twenty-one percent of placebo-treated grafts became occluded. Compared with placebo, the relative risk of graft occlusion with ASA was 0.47 (p = .04); with ASA + DP, it was 0.50 (p = .04). This benefit was principally due to reduction of occlusion in the most common and presumably most important groups of grafts, those in which flow exceeded 40 ml/min, or supplying arteries having luminal diameters greater than 1.5 mm. Grafts lacking reactive hyperemia had a 32% occlusion frequency in placebo-treated patients; relative risk of their occlusion averaged 0.26 (p less than .01) with platelet-inhibiting therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Usefulness of coronary artery bypass graft surgery or percutaneous transluminal angioplasty after thrombolytic therapy.

Intracoronary streptokinase (STK) was given to 52 patients and 2 million U of intravenous urokinase was given to 15 patients with acute myocardial infarction less than 3 hr from onset of symptoms. Wall motion in the infarct region improved in 20 patients receiving STK alone (-2.5 +/- 1 to 2.1 +/- 1.1 SD/chord) and in 22 patients receiving STK and undergoing coronary bypass surgery within 24 hr (-2.5 +/- 1 to -1.5 +/- 1.0 SD/chord). Wall motion was unchanged in 10 patients not successfully reperfused with STK (-2.9 +/- 0.7 to -3.1 +/- 0.7 SD/chord). Regional wall motion improved at least 1.0 SD/chord in 71% of 14 patients treated within 2 hr of onset of symptoms, but in only 29% of 34 treated after 2 hr. Mean coronary artery stenosis after thrombolysis was 77 +/- 9%. Rethrombosis was associated with a stenotic cross-sectional area of less than 0.4 mm2. Ventricular function did not improve, with a residual stenosis of 0.4 mm or less in diameter. The Western Washington randomized trial reported a 1 year mortality of 2.5% in 80 successfully reperfused patients, but a mortality of 23% in 13 in whom reperfusion was partial and of 14.6% in 41 in whom reperfusion failed. The improved survival with successful reperfusion and improved ventricular performance with early and more complete reperfusion has stimulated interest in the need for angioplasty and coronary artery bypass grafting after thrombolytic therapy.

Angioplasty, Balloon↗
PubMed1984

A new digital electronic caliper for measurement of coronary arterial stenosis: comparison with visual estimates and computer-assisted measurements.

Visual analysis of the severity of coronary stenosis is limited by observer variability. However, more complex techniques of proved accuracy are tedious and costly. Therefore, a new digital electronic caliper (DEC) was evaluated as a potentially more accurate, rapid and less costly alternative for measuring stenosis severity. Stenosis minimum diameter (Dmin) and percent diameter reduction (% S) were measured from the screen of the cine projector using a DEC. These measurements were compared with visual estimates (VIS) by 4 experienced angiographers and with measurements made by a computer-assisted method (QCA) of proved accuracy. In routine cineangiograms from 7 patients, 10 lesions were significant (greater than 50% S) and 8 were mild (less than 50% S). Variability, the standard deviation of multiple estimates of Dmin and % S, averaged 0.09 mm and 3.1% for QCA; 0.18 mm and 5.9% for DEC; and 0.26 mm and 7.4% for VIS. Compared with QCA, the visual determination of % S significantly underestimates (-5%; p less than 0.02) mild and overestimates (+11%; p less than 0.002) significant stenosis. VIS underestimates Dmin in significant lesions by 20% (p less than 0.04). In contrast, the mean error for DEC measurement of Dmin and % S was not significantly different from 0 in either lesion group. For the entire group of lesions, and particularly in significant lesions, the mean error for measurement of these 2 indexes of disease was significantly less with DEC than with VIS. Thus, variability and error with DEC are acceptably low for clinical use.(ABSTRACT TRUNCATED AT 250 WORDS)

Cineangiography↗
PubMed1984

Reflex constriction of significant coronary stenosis as a mechanism contributing to ischemic left ventricular dysfunction during isometric exercise.

To study the mechanisms of myocardial ischemia during isometric exercise, handgrip was sustained, for 4.5 min at 25% of maximum by 11 patients with at least one significant coronary stenosis each, during cardiac catheterization. After recovery, the handgrip that was repeated with simultaneous infusion of nitroglycerin (50 micrograms over 4 min) directly into the diseased vessel. The cardiovascular response was assessed by hemodynamic and by computer-assisted measurements of stenosis. During the first handgrip test pulmonary capillary wedge pressure rose 56% (15 to 23 mm Hg; p less than .001), the heart rate-systolic pressure product rose 33% (p less than .01), and the diseased epicardial arteries constricted. Luminal area in the stenotic segment was reduced by 35% (p less than .01), resulting in a 243% increase in estimated stenotic flow resistance (30 to 103 mm Hg/ml/sec; p less than .001). During handgrip with intracoronary nitroglycerin, the pressure-rate product again increased 33%, but relative to resting control, capillary wedge pressure fell 4 mm Hg in association with a 32% increase in luminal area of the stenosis and a 28% reduction in flow resistance (all significantly different from the response to handgrip alone: p less than .001, .01, and .005, respectively). Thus, coronary vasoconstriction, not increased pressure-rate product, is the dominant mechanism for ischemic left ventricular dysfunction during isometric exercise in patients with significant coronary stenoses.

Adult↗
PubMed1984

Diltiazem-induced blockade of sympathetically mediated constriction of normal and diseased coronary arteries: lack of epicardial coronary dilatory effect in humans.

To determine mechanisms of benefit from diltiazem, 13 patients with coronary disease performed sustained isometric handgrip exercise and repeated the procedure during intravenous infusion of diltiazem (0.25 mg/kg bolus followed by 0.003 mg/kg/min). Cardiovascular responses to handgrip, diltiazem, their combination, and nitroglycerin were assessed by hemodynamic and electrocardiographic measurements and by computer-assisted measurements of normal and diseased segments of epicardial coronary arteries. Handgrip produced increases in heart rate (12%; p less than .001), pulmonary arterial pressure (19%; p less than .005), and pulmonary wedge pressure (33%; p less than .005). Diltiazem produced significant reductions in heart rate (7%; p less than .05) and aortic pressure (14%; p less than .001). Pulmonary arterial pressure and pulmonary wedge pressure were unchanged by diltiazem. Diltiazem did not prevent the increase in heart rate or in aortic or wedge pressure associated with handgrip. Diltiazem prolonged atrioventricular conduction from 0.18 +/- 0.03 to 0.20 +/- 0.03 sec (p less than .001). Compared with control values, nitroglycerin reduced aortic pressure (14%; p less than .005), pulmonary arterial pressure (38%; p less than .001), and pulmonary wedge pressure (42%; p less than .005). Heart rate was unchanged. The constriction (20%) in lumen area of normal coronary arterial segments during handgrip was effectively prevented by infusion of diltiazem (1%; p less than .001). Nitroglycerin produced a significantly greater increase (20%) in diameter of normal coronary arterial segments than diltiazem (3%; p less than .001) and tended to have a more favorable effect than diltiazem on stenosis minimum area and flow resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzazepines↗
PubMed1984

Dynamic mechanisms in human coronary stenosis.

At the clinical level, coronary stenoses frequently behave as though the obstruction to flow were variable and not as rigidly fixed as previously imagined. Pressure (energy) lost in flow through a stenosis is the primary determinant of its hemodynamic impact. Ischemic episodes occur when pressure distal to the stenosis falls below that needed to perfuse the subendocardium. Three important properties of the stenosis contribute to variation in its pressure loss. First, loss is proportional to the square of stenosis flow. Thus proper distribution of perfusion is doubly vulnerable to conditions such as exercise, anemia, or pharmacologic vasodilation, which ordinarily increase myocardial blood flow. Second, pressure loss is proportional to the inverse fourth power of minimum lumen diameter. As a result, seemingly small changes in diameter are amplified to large changes in stenosis resistance. Third, a compliant arc of normal arterial wall borders part of the lumen in the majority of coronary lesions. This extremely important morphologic feature of stenoses permits transient variation in stenosis lumen diameter in response to drugs or to variation in endogenous vasomotor activity or intraluminal pressure. Although our understanding is incomplete, many of the clinical features of coronary disease and its pharmacologic responses are explained in terms of these stenosis properties and their interaction.

Arteriosclerosis↗
PubMed1984

Surgical technique to cannulate the rete testis of the goat.

A surgical technique was devised to collect rete testis fluid from 14 mature goats. The tubular portion of the extratesticular rete testis was cannulated where it penetrated the tunica albuginea of the testis under the center of the head of the epididymis. The tip of the cannula was sutured in place in the extratesticular rete testis and the opposite end was passed through the scrotum and into a plastic collection bottle. The bottle was glued to pillow ticking, which was sutured to the scrotum. Continuous flow of rete testis fluid occurred for 0 to 14 days and was usually terminated by a sperm clot in the cannula. The flow rate was 0.59 +/- 0.37 ml/hr.

Animals↗