Key references. Pulmonary embolism. Part I.
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Biomedical subjects
Publications and source records attributed to G V Sharma.
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To develop a way to prevent the occlusion of the aortocoronary saphenous vein bypass grafts, we conducted a prospective, randomized, double-blind trial in 176 patients, some of whom received aspirin alone (975 mg/day) and some of whom took a combination of aspirin and dipyridamole (225 mg/day), and compared them with a parallel control group. Therapy was started 3 to 5 days after surgery. Follow-up angiography was performed in 142 patients (80%) at 1 year. Graft patency in the aspirin group (78%) was not significantly different from that in the aspirin-dipyridamole group (83%) or the control group (80%). Even in the patients at high risk for graft occlusion, i.e., those who had small recipient coronary arteries and poor graft flows, patency rates were not improved by the antiplatelet agents. When administered 3 to 5 days after surgery, aspirin alone or in combination with dipyridamole does not improve graft patency.
For prognostication of aorta-coronary bypass graft patency, preoperative angiographic assessment of the recipient vessel and the regional left ventricle was compared with the intraoperative measurement of the internal diameter of the vessel and graft flow in 98 patients, in whom graft patency was evaluated at 1 year. Preoperative assessment of the recipient vessel did not correlate with the intraoperative measurement of the internal diameter or with the graft patency. Preoperative assessment of the regional left ventricular wall motion, on the other hand, was more valuable for prognosticating graft patency. Regions assessed as normal or hypokinetic had equally good graft patency, whereas akinetic or dyskinetic areas had only a 54% patency rate. Intraoperative measurement of the internal diameter of the vessel and graft flow were reliable predictors of graft patency: The larger the internal diameter and the greater the graft flow, the better the graft patency. Best surgical results can therefore be predicted when the internal diameter of the recipient vessel is 2.5 mm or more, graft flow is 100 ml/min or more, and the regional left ventricle moves well.
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Urokinase and streptokinase are the two fibrinolytics approved for clinical use. Streptokinase has the broader application, being used to treat deep vein thrombosis (DVT), pulmonary embolism (PE), arterial thromboembolism, and occluded arteriovenous shunts in renal dialysis. Bleeding, the most significant complication of fibrinolytic therapy, arises mostly from invaded sites and can be significantly reduced by minimizing venipuncture and other invasive procedures.
The use of thrombolytic agents in venous thromboembolism has been shown to be highly effective. Patients treated with lytic agents show more rapid clot resolution and lung reperfusion and more rapid and greater reversal of the abnormal hemodynamic responses to pulmonary embolism than patients receiving heparin. Moreover, lytic therapy removes thromboemboli more completely from the pulmonary microcirculation, whereas residual thromboemboli tend to accumulate with heparin therapy. In addition, lytic therapy tends to preserve the venous valves, whereas distortion and destruction occur with heparin therapy. Hence, lytic therapy confers a number of short- and long-term benefits not observed with heparin therapy.
Two dimensional echocardiography is just beginning to be used to characterize cardiac damage in patients with acute myocardial infarction. The two dimensional approach allows for a more comprehensive evaluation of cardiac anatomy and is able to detect with high sensitivity changes in regional wall motion that previously were sometimes missed or only found with difficulty using M mode echocardiography. Two dimensional echocardiography appears to offer a basis for quantifying the extent of myocardial damage in acute myocardial infarction and thus may permit objective assessment of therapeutic modalities and prognosis. In addition, the technique facilitates recognition of specific complications in acute myocardial infarction. In particular, the technique offers te ability to distinguish true from false ventricular aneurysm, postinfarction ventricular septal defect from papillary muscle dysfunction and rupture, and right ventricular infarction from cardiac tamponade.
To compare the effects of heparin thrombolytic agents in pulmonary thromboembolic disease, we randomly assigned 40 patients with pulmonary emboli but without other clinical cardiopulmonary disease either to heparin followed by oral anticoagulants (21 patients) or to urokinse or streptokinase followed by heparin and then by oral anticoagulants (19 patients). The effects on pulmonary-capillary blood volume and diffusing capacity were compared at two weeks and at one year. The pulmonary-capillary blood volume (in milliliters per square meter of body-surface area) was abnormally low (30 +/- 2.4) [+/- S.E.]; normal, 47 +/- 1.5) in the heparin-treated group at two weeks and remained unchanged at one year. In contrast, it was normal (45 +/- 2.5) in the group receiving thrombolytic agents, both at two weeks and at one year (P < 0.001). The pulmonary diffusing capacity was reduced to 69% of the predicted value in the heparin group at two weeks and 72% at one year, whereas it was 85% of the predicted value in the thrombolytic group at two weeks and 93% at one year (P < 0.001). These results indicate that thrombolytic agents allow more complete resolution of thromboemboli than do heparin and anticoagulants and that they improve capillary perfusion and diffusion.
Using a tri-lumen graduated 10F catheter we attempted to record static (lateral) pressures at successive points in the urethra, synchronous with intravesical pressure recorded during voiding. Based on our understanding of the essential physical principles described by many earlier investigators we attempted numerous studies in a predominantly male population, which included normal male and female subjects, and male subjects with bladder outlet obstruction of varied etiology. We also attempted to evaluate the effects of the Valsalva maneuver, augmenting the detrusor contraction and artificial distal obstruction (penile compression) on the micturitional static urethral pressure profiles. Studies also were performed to compare the static urethral pressure profiles obtained with the anterograde (catheter withdrawal) and with the retrograde (catheter insertion during voiding) techniques. All of these studies have helped in understanding the various factors, such as double obstructions, artifactual catheter obstructions and incompetent distal sphincter mechanisms, in the interpretation of the micturitional static urethral pressure profile.
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