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Biomedical subjects

J L Ritchie

Publications and source records attributed to J L Ritchie.

At least 73 records · Page 4Linked to original sources
PubMed1988

Rotational atherectomy in atherosclerotic rabbit iliac arteries.

PTCA is not technically possible in many patients with symptoms of coronary artery disease. In addition, atheroma is not physically removed by PTCA, and restenosis of the treated vessel is common. We have tested a new, rotating, abrasive-tipped angioplasty device in vivo in 13 atherosclerotic rabbit iliac vessels. Atherosclerosis was generated in rabbit iliac vessels by a 2% cholesterol diet combined with balloon endothelial injury for 10 weeks. The diseased vessels were then treated with the rotational atherectomy device. Before treatment, contrast angiograms demonstrated that initial percent diameter stenosis was 81% +/- 9%. After atherectomy, there was significant improvement, with residual 38% +/- 22% narrowing (p less than 0.001). One perforation resulted from distal guidewire manipulation, and one vessel was occluded by the device. Histologic examination demonstrated loss of portions of the diseased intima in all cases. Particles were produced for analysis in vitro by operating the atherectomy device in atherosclerotic rabbit aortas perfused with saline solution. Ninety-eight percent of the particles produced by the device were less than 10 micron in diameter. We conclude that this new rotational device can remove atheromatous material from diseased arteries in rabbits. Such a device may complement other angioplasty techniques and lead to wider application of catheter-based therapeutic interventions.

Animals↗
PubMed1988

Ventricular function and infarct size: the Western Washington Intravenous Streptokinase in Myocardial Infarction Trial.

The Western Washington Intravenous Streptokinase in Acute Myocardial Infarction Trial randomized 368 patients with symptoms and signs of acute myocardial infarction of less than 6 h duration to either conventional care or 1.5 million units of intravenous streptokinase. The mean time to randomization was 209 min and 52% of patients were randomized within 3 h of symptom onset. Quantitative, tomographic thallium-201 infarct size and radionuclide ejection fraction were measured at 8.2 +/- 7.5 weeks in 207 survivors who lived within a 100 mile radius of a centralized laboratory. Overall, infarct size as a percent of the left ventricle was 19 +/- 13% for control subjects and 15 +/- 13% for treatment patients (p = 0.03). For anterior infarction in patients entered within 3 h of symptom onset, infarct size was 28 +/- 13% in the control group versus 19 +/- 15% for the treatment group (p = 0.09). Left ventricular ejection fraction was 47 +/- 15% in the control versus 51 +/- 15% in the treatment group (p = 0.08). For anterior infarction of less than 3 h duration, the ejection fraction was 38 +/- 16% in the control versus 48 +/- 20% in the treatment group (p = 0.13). By statistical analysis incorporating the nonsurvivors, p values for all of these variables were less than or equal to 0.08. There was no benefit for patients with inferior infarction or for anterior infarction of greater than 3 h duration. It is concluded that intravenous streptokinase, when given within 3 h of symptom onset to patients with anterior infarction, reduces infarct size and improves ventricular function.

Clinical Trials as Topic↗
PubMed1988

Relation of global and regional left ventricular function to tomographic thallium-201 myocardial perfusion in patients with prior myocardial infarction.

To determine the relation between regional myocardial perfusion and regional wall motion in humans, tomographic thallium-201 imaging and two-dimensional echocardiography at rest were performed on the same day in 83 patients 4 to 12 weeks after myocardial infarction. Myocardial perfusion and wall motion were assessed independently in five left ventricular regions (total 415 regions). Regional myocardial perfusion was quantitated as a percent of the region infarcted (range 0 to 100%) using a previously validated method. Wall motion was graded on a four point scale as 1 = normal (n = 266 regions), 2 = hypokinesia (n = 64), 3 = akinesia (n = 70), 4 = dyskinesia (n = 13) or not evaluable (n = 2). Regional wall motion correlated directly with the severity of the perfusion deficit (r = 0.68, p less than 0.0001). Among normally contracting regions, the mean perfusion defect score was only 2 +/- 4. Increasingly severe wall motion abnormalities were associated with larger perfusion defect scores (hypokinesia = 6 +/- 5, akinesia = 11 +/- 7 and dyskinesia = 18 +/- 5, all p less than 0.01 versus normal. Among regions with normal wall motion, only 3% had a perfusion defect score greater than or equal to 10. Conversely, among 68 regions with a large (greater than or equal to 10) perfusion defect, only 13% had normal motion whereas 87% had abnormal wall motion. The relation between perfusion and wall motion noted for the entire cohort was also present in subgroups of patients with anterior or inferior infarction. In patients with prior myocardial infarction, the severity of the tomographic thallium perfusion defect correlates directly with echocardiographically defined wall motion abnormalities, both globally and regionally.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1988

Rotational endarterectomy in normal canine coronary arteries: preliminary report.

Endarterectomy was performed in vivo using a high speed rotating abrasive-tipped catheter device in 11 normal canine coronary arteries. The device is designed to remove atheromatous material from diseased arteries by the abrasive action of its rotating tip. It was operated percutaneously from a femoral approach using conventional angioplasty guiding equipment. The rotating device was advanced over a guide wire from just beyond the tip of the guide catheter into the distal vessel. Six arteries were harvested immediately after endarterectomy and five were left in place for 7 +/- 2.8 days; in the latter group, the animals were maintained on a regimen of aspirin, 325 mg/day. Angiography before and after treatment demonstrated vessel patency in all cases. Caliper-measured luminal diameters were not significantly changed after endarterectomy. Histologic examination of pressure-fixed vessels showed extensive intimal loss and 20 to 30% loss of the internal elastic lamina. Medial damage was superficial and never exceeded 40% of the total medial thickness. There were no vessel perforations. Results of histologic study of the myocardium supplied by the treated vessels were normal without evidence of distal embolization or infarction. It is concluded that a high speed rotating abrasive device can be safely operated percutaneously in normal coronary arteries and results in minimal vessel damage and continued patency at 7 +/- 2.8 days.

Angioplasty, Balloon↗
PubMed1988

The Western Washington Intravenous Streptokinase in Acute Myocardial Infarction Randomized Trial.

Three hundred sixty-eight patients were randomly assigned to receive intravenous streptokinase (IVSK) (n = 191) or standard therapy (n = 177) to determine the efficacy of IVSK in the treatment of acute myocardial infarction. The mean time to treatment was 3.5 hr. At 14 days there were 12 deaths in the treatment group (6.3%) and 17 deaths in the control group (9.6%) (p = .23). Early mortality was related to infarct location. Fourteen day mortality for anterior infarctions was 10.4% for treatment with IVSK and 22.4% for control patients (p = .06) and was similar for IVSK-treated patients with inferior infarctions, 4.0% vs 1.8% (p = .32). For those randomized under 3 hr, 14 day mortality tends to be lower in treated patients, 5.2% vs 11.5% (p = .11). There was significant improvement in long-term survival for patients with anterior infarction; 2 year survival was 81% for IVSK-treated patients and 65% for control patients (p = .05). There was no improvement in survival for patients with inferior myocardial infarction (p = .27). We conclude that patients with anterior myocardial infarction have improved survival when treated within the first 6 hr of symptoms. Patients with inferior infarction do not appear to have improved survival with thrombolytic therapy. Some of this improvement in survival in patients with anterior infarction may be due to a higher frequency of revascularization procedures in the treatment group.

Aged↗
PubMed1988

Intravenous streptokinase for acute myocardial infarction. Effects on global and regional systolic function.

The Western Washington Intravenous Streptokinase Trial randomized 368 patients with acute myocardial infarction to receive either intravenous streptokinase or standard therapy. The ventriculograms and coronary angiograms obtained in 170 patients 10.4 +/- 7.4 days after infarction were analyzed to evaluate the effects of thrombolytic therapy on global and regional systolic function. Streptokinase treatment resulted in a higher patency rate of the infarct-related artery (68.5%) than did standard therapy (44.8%) (p = 0.003). Ejection fraction was higher in streptokinase-treated patients (54% vs. 51%, p = 0.056), and the difference was most marked in patients with anterior myocardial infarction (53% vs. 44%, p = 0.03). Regional wall motion was measured by the centerline method and expressed in mean +/- SD motion in 52 normal subjects. There was a trend toward better function of the infarct zone in streptokinase-treated patients (SD, -2.48 vs. -2.70, p = 0.24). Additionally, streptokinase-treated patients had significantly better wall motion of noninfarct areas (SD, 0.36 vs. -0.08, p = 0.02). Treatment effects on function of noninfarct regions were most apparent in the subset of patients with multivessel disease. Thus, intravenous streptokinase preserves left ventricular function in patients with acute myocardial infarction. This benefit includes favorable effects on the function of regions remote from the site of infarction.

Cardiac Catheterization↗
PubMed1988

The influence of collimators on SPECT center of rotation measurements: artifact generation and acceptance testing.

Misalignment between the electronic and mechanical axes of rotation will result in artifact generation and image degradation during single photon emission computed tomography (SPECT) reconstruction. Acceptance and quality control testing procedures have not emphasized the variability in center of rotation (COR) measurements caused by collimators and the need to verify uniformity across the full collimator field of view (FOV). Variation from the mean COR across the FOV was tested in four different collimators using multiple point source acquisitions. The mean COR was different for each collimator and two of the four had a greater than 0.5 pixel difference from the mean COR on some area of the FOV. This variation makes these collimators unacceptable for SPECT acquisition. Thus, initial acceptance testing of SPECT collimators should verify a uniform COR across the full FOV and collimators with a variability from the mean COR greater than 0.5 pixels should be rejected.

Calibration↗
PubMed1987

Mechanical thrombectomy: a comparison of two rotational devices and balloon angioplasty in subacute canine femoral thrombosis.

In this study, two prototype rotational devices were compared to balloon angioplasty in a canine model of subacute arterial thrombosis. Radiographic 2- to 8-day-old total thrombotic occlusions were produced in 30 canine femoral arteries. A high-speed rotating device with a cutting tip was used in 18 arteries. Successful opening occurred in every case, with a residual percent diameter stenosis at 45 +/- 25%. Vessel perforation was seen in 6 of the 18 arteries. A noncutting rotational thrombectomy catheter was used in six arteries. Radiographic patency was established in two of six (residual stenosis 86 +/- 28%), with one perforation with the use of the noncutting thrombectomy catheter. Balloon angioplasty reestablished radiographic patency in three of six arteries (residual stenosis 77 +/- 2%). No perforations were seen with balloon dilation, but radiographic distal emboli were always observed. No radiographic emboli were observed with either of the rotational devices. We conclude that subacute arterial thromboses are easily opened with an abrasive-tipped rotating angioplasty device. Although perforations are relatively common with this prototype equipment, design changes may produce a clinically useful angioplasty device.

Angioplasty, Balloon↗
PubMed1987

Evaluation of myocardial perfusion and function by single photon emission computed tomography.

Although planar radionuclide techniques provide accurate, noninvasive measurements of myocardial perfusion and function that are of proven clinical value in the evaluation of the cardiac patient, they are limited by poor object contrast and superimposition of surrounding structures. Due to incomplete angular sampling and significant longitudinal distortion, limited angle tomography did not solve these problems. Single photon emission computed tomography (SPECT) can acquire scintillation information over very small angles of rotation and, thus, improve both object contrast and delineation of overlying or adjacent structures without distortion. The early SPECT systems were cumbersome, dependent on individual user developed software, and had extremely long acquisition and processing time. Improved camera design, new software algorithms, and the use of array processors have simplified and standardized quality control, decreased processing time, and minimized the number of user interventions. New image display formats and quantitative methods of analysis have made interpretation less cumbersome, more reliable and highly reproducible. Cardiac SPECT has been used with thallium-201 and gated blood pool imaging in both research and clinical applications and shown an improvement over planar methods of acquisition.

Algorithms↗
PubMed1987

Rotational approaches to atherectomy and thrombectomy.

We have developed and tested a rotational, mechanical approach to arterial plaque removal (PTRA or Percutaneous Transluminal Rotational Atherectomy). An elliptical burr is rotated by a helical driveshaft at 150,000 rpm. The tip of the burr is embedded with small diamond chips, 30 micron in diameter. Plaque is thus abraded and particles of 2-5 micron in diameter are released downstream. Preliminary studies in a rabbit model of iliac atherosclerosis showed a reduction in percent diameter stenosis from more than 80% to less than 40%. Perforations are the current principal complication, occurring in 2 of the 13 rabbit arteries. A second rotational catheter system has been developed for removal of fresh thrombus (PRT-Percutaneous Rotational Thrombectomy). Low speed rotation (5000 rpm) of a non-cutting catheter promotes the selective winding of fibrin with subsequent lysis of thrombus. This was effective in 20 out of 21 total thrombotic occlusions in a canine model of fresh clot, with a single perforation early in the experiment.

Animals↗
PubMed1986

Effect of suloctidil on tomographically quantitated platelet accumulation in Dacron aortic grafts.

Platelet deposition contributes to the thrombotic and embolic complications of prosthetic materials in man. To determine if the investigational platelet inhibitory drug suloctidil (200 mg 3 times daily) reduces platelet deposition on Dacron aortic grafts, a randomized, double-blind, crossover trial was conducted in 12 men with grafts that had been in place more than 9 months. Platelet deposition in the graft was assessed by quantitative analysis of planar images obtained at 24, 48 and 72 hours after injection of indium-111-labeled platelets. Also, a tomographic method of imaging and quantitating labeled platelet deposition in the graft was developed. Tomographic imaging was performed at 24 and 72 hours after platelet injection and was quantitated by a graft/blood ratio that compared indium-111 platelet activity in summed 1.8-cm-thick transaxial tomographic slices of the aortic graft to indium-111 platelet activity in well-counted whole blood. Compared with placebo, suloctidil failed to decrease the tomographic graft/blood ratio at 24 hours (6.2 +/- 1.3 vs 5.7 +/- 0.8) and 72 hours (11.4 +/- 2.9 vs 10.7 +/- 2.2). Similarly, the graft/blood ratio determined by planar imaging was not different between placebo and suloctidil therapy at 24 hours (1.7 +/- 0.3 vs 1.6 +/- 0.2), 48 hours (2.2 +/- 0.4 vs 2.4 +/- 0.4) or 72 hours (2.6 +/- 0.5 vs 2.8 +/- 0.5) after labeled platelet injection. Thus, suloctidil does not significantly reduce platelet deposition on chronically implanted Dacron grafts in humans.

Adult↗
PubMed1986

Reduction of indium-111 platelet deposition on Dacron vascular grafts in humans by aspirin plus dipyridamole.

Aspirin plus dipyridamole reduces platelet accumulation on short-term Dacron vascular grafts in man. To determine whether drug inhibition of platelet deposition is sustained on older grafts, we studied 18 men aged 41 to 87 years who had Dacron aortic bifurcation grafts in place a mean of 43.4 months (range 9.8 to 121.0) before and during short-term therapy with aspirin (325 mg tid) plus dipyridamole (75 mg tid). During both the baseline and drug studies, indium-111 (111In) platelet deposition was quantitated by two techniques, standard planar imaging performed at 24, 48, and 72 hr after injection of platelets and single photon emission computed tomographic imaging performed at 24 and 72 hr after injection. All analyses were performed in a blinded fashion. On both the planar and tomographic images, platelet accumulation on the graft was quantitated by a graft/blood ratio that compared activity in the graft to simultaneously collected whole blood 111In platelet activity. Aspirin plus dipyridamole reduced the tomographic graft/blood ratio at 24 hr (20.6 +/- 3.5 vs 17.3 +/- 2.5) (+/-SEM) and at 72 hr (29.0 +/- 4.8 vs 25.0 +/- 4.1) after injection of platelets (p = .02). Dacron vascular grafts. Similarly, the planar graft/blood ratio was reduced at 24 hr (2.7 +/- 0.5 vs 2.4 +/- 0.5), 48 hr (3.7 +/- 0.9 vs 3.1 +/- 0.7), and 72 hr (4.0 +/- 0.9 vs 3.6 +/- 0.8) (p = .04). We conclude that aspirin (325 mg tid) plus dipyridamole (75 mg tid) reduces platelet accumulation on long-term Dacron vascular grafts.

Adult↗
PubMed1986

Mechanical thrombolysis: a new rotational catheter approach for acute thrombi.

We tested a new rotational thrombectomy catheter in acute thrombi formed both in vitro and in vivo. The catheter consisted of a rounded platinum tip, 0.025 inch diameter by 0.08 inch long, attached to a flexible steel guidewire supported by an external sheath. In vitro, the force required to penetrate thrombus was reduced fivefold by rotation of the catheter at 4000 rpm (0.75 +/- 1.2 g rotating vs 3.9 +/- 2.1 g static; p less than .001). Fibrin was extracted selectively from the thrombus and tightly wound about the shaft (3.8 +/- 1.5 mg rotating vs 0.75 +/- 0.4 mg static; p less than .001). In vivo, subtotal or complete thrombosis of the canine femoral artery was created. Thrombectomy by catheter rotation always produced tightly wound adherent fibrin on the catheter shaft. Angiographic patency was restored in 20 of 22 (91%) arteries, totally in seven of 22 (32%) and partially (greater than 20% increase in lumen diameter) in 13 of 22 (59%). There was one arterial perforation (5%). We conclude that this new mechanical catheter device reduces the force required to penetrate thrombus. Additionally, by winding fibrin about its shaft, the catheter is able to selectively remove the fibrin matrix of thrombus. Thus both the ease of initial thrombus recanalization as well as physical removal of thrombus are promoted by this new approach. Such an approach may be relevant to the treatment of recent thrombosis in acute myocardial infarction.

Acute Disease↗
PubMed1986

Risk stratification for 1 year survival based on characteristics identified in the early hours of acute myocardial infarction. The Western Washington Intracoronary Streptokinase Trial.

We evaluated the relationship between baseline factors defined at 4.6 +/- 2.1 hr after onset of acute myocardial infarction and 1 year survival in 245 patients entered in the Western Washington Intracoronary Streptokinase Trial. Univariate statistics identified a significant relationship between 10 of these factors and survival. Multivariate analysis identified three factors as being most closely related to survival: (1) left ventricular ejection fraction (LVEF) (p less than .0001), (2) treatment with streptokinase (p = .03), and (3) location of infarction (p = .04). Mathematic models based on this analysis and applied to our patients identified high- and low-risk subgroups for 1 year mortality. Patients receiving standard, not interventional, therapy with anterior infarction and an LVEF of 50% or less and those with inferior infarction and an LVEF of 39% or less comprised the high-risk group. For patients receiving standard therapy, 1 year mortality was 41% in the high-risk group and 4% in the low-risk group. The models illustrated the magnitude of benefit of streptokinase treatment and achievement of complete reperfusion for those at low and high risk. We conclude that LVEF determined in the first hours of acute myocardial infarction is the most important of all baseline factors for prediction of 1 year survival. Mathematic models based on left ventricular function measured as ejection fraction are useful for risk stratification in this setting.

Adult↗
PubMed1986

Effects of thrombolytic therapy on evolution of left ventricular function in acute myocardial infarction.

Use of thrombolytic therapy in the early hours of acute myocardial infarction (AMI) has gained widespread acceptance. One potential benefit of early reperfusion could be improved left ventricular (LV) function. Experimental animal studies have demonstrated that duration of coronary occlusion determines ultimate infarct size and have also raised the issue of reperfusion injury. The evolution of LV function after AMI in man where there is no attempt at early reperfusion is discussed. Studies of LV function following thrombolytic therapy in man have illustrated the following points. Time to successful reperfusion appears to be a critical determinant for potential for LV functional recovery. If reperfusion is achieved within 2.5 hours after onset of symptoms, consistent recovery of function within the infarct zone appears to be possible. With reperfusion from 2.5 to six hours after onset of symptoms, there is no predictable, substantial improvement in either global or regional LV function. Within the framework of this general conclusion, there are three potential exceptions: Successful reperfusion up to six hours after onset of symptoms may prevent infarct expansion. Patients with subtotal occlusion of the infarct vessel prior to therapy in this time period may have more potential for recovery of LV function than those with initial total occlusion. A tight residual stenosis following thrombolytic therapy may mask potential for functional recovery in the infarct zone. Earlier diagnosis and treatment of AMI is one obvious solution for the overall lack of beneficial results on evolution of LV function seen in most studies to date.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMed1985

The western Washington randomized trial of intracoronary streptokinase in acute myocardial infarction. A 12-month follow-up report.

After cardiac catheterization and coronary arteriography, 134 patients who had had an acute myocardial infarction were randomly assigned to treatment with intracoronary streptokinase (4000 U per minute, begun approximately 4 1/2 hours after the onset of symptoms, for a total of 286,000 +/- 77,800 U over 72 +/- 24 minutes); 116 control patients received standard care after they returned to the coronary care unit, immediately after angiography. Preliminary results of this trial have been published in the Journal (1983; 309:1477-81). During the first 30 days, 5 deaths occurred in the streptokinase group and 13 occurred in the control group (3.7 vs 11.2 per cent, P = 0.02); during the first year, the corresponding figures were 11 and 17 deaths (8.2 vs. 14.7 per cent, P = 0.10). However, when a minor imbalance in the ejection fraction and infarct location between the two groups was adjusted by logistic regression, the difference in one-year mortality became significant (P = 0.03). In the streptokinase group, 2 of the 80 patients in whom perfusion was reestablished (2.5 per cent) had died by one year, whereas 3 of the 13 with partial reperfusion (23.1 per cent) and 6 of the 41 with no reperfusion (14.6 per cent) had died (P = 0.008). Mortality among patients with partial reperfusion was not significantly different from that among those without reperfusion (P greater than 0.90). No base-line clinical, angiographic, or hemodynamic variable was predictive of successful reperfusion, according to univariate and multivariate analyses. We conclude that intracoronary streptokinase reduces one-year mortality among patients with acute myocardial infarction, but this improvement occurs only among those in whom thrombolysis results in coronary artery reperfusion.

Coronary Angiography↗