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Biomedical subjects

A A Ziskind

Publications and source records attributed to A A Ziskind.

27 records · Page 2Linked to original sources
PubMed1990

Effect of blood upon the selective ablation of atherosclerotic plaque with a pulsed dye laser.

Laser angioplasty systems with laser energy preferentially absorbed by atherosclerotic plaque may offer a safe method of plaque removal. This study evaluated the effect of blood upon selective energy absorption using a pulsed dye laser at 480 nm. Intra-arterial laser irradiation of normal rabbit femoral arteries demonstrated a perforation threshold energy with blood perfusion of 13.1 mJ per pulse compared to 87.9 mJ with saline (P less than .0001), indicating a deleterious effect in the presence of blood. An adverse effect upon arterial healing at 3 days was noted in sheep following intra-arterial irradiation during blood but not saline perfusion. Normal and atherosclerotic human aorta ablation thresholds differed significantly (P less than .0002) under saline (plaque: 20 mJ and normal: 120 mJ) but the difference under blood (plaque: 5 mJ and normal: 20 mJ) was not significant. We conclude that absorption of laser energy by blood can reduce the effect of differential absorption by endogenous chromophores in normal and pathologic vascular tissues and, therefore, removal of blood may be a prerequisite for selective ablation of atherosclerotic plaques.

Animals↗
PubMed1990

Prevention of platelet-rich arterial thrombosis by selective thrombin inhibition.

The effect of heparin and of the synthetic competitive thrombin inhibitor (2R,4R)-4-methyl-1-[N2-(3-methyl-1,2,3,4-tetrahydro-8-quinolinesulfon yl)-L-arginyl]-2-piperidinecarboxylic acid monohydrate (argatroban) on platelet-rich arterial thrombosis was studied in a rabbit model, consisting of a 4-6-mm everted ("inside-out") femoral arterial segment. Intravenous injection of heparin (200 units/kg) failed to prevent occlusion within 60 minutes in all 10 rabbits, whereas intravenous argatroban infusion at a rate of 100 or 200 micrograms/kg/min for 60 minutes, which prolonged the thrombin time more than fourfold, prevented thrombosis in nine of 13 rabbits (p = 0.002 vs. i.v. heparin). Intra-arterial infusion of 200 units/kg heparin over 60 minutes prevented occlusion in six of nine rabbits (p = 0.003 vs. i.v. heparin), whereas intra-arterial argatroban at a rate of 100 micrograms/kg/min for 60 minutes prevented thrombosis in all 10 rabbits (p = 0.00001 vs. i.v. heparin). Patency of femoral arterial segments was maintained after the end of the intra-arterial heparin and intravenous or intra-arterial argatroban infusion for up to 3 hours despite normalization of the thrombin time and partial thromboplastin time. Pathologic examination of the graft revealed that the inverted adventitial surface was covered by layers of platelets without platelet aggregation or fibrin deposition. These findings indicate that thrombin plays an important role in platelet-rich arterial thrombosis, and that the thrombogenic stimulus is rapidly attenuated by short-term infusion of the synthetic thrombin inhibitor. Selective thrombin inhibition can constitute an alternative approach to the prevention of arterial occlusion after angioplasty or thrombolytic therapy in patients with unstable coronary syndromes.

Animals↗
PubMed1989

Synergistic combinations of recombinant human tissue-type plasminogen activator and human single-chain urokinase-type plasminogen activator. Effect on thrombolysis and reocclusion in a canine coronary artery thrombosis model with high-grade stenosis.

The synergistic effects of recombinant human tissue-type plasminogen activator (rt-PA) and single-chain urokinase-type plasminogen activator (scu-PA) on coronary arterial thrombolysis were investigated in open-chest dogs with thrombosis of the left anterior descending coronary artery and a superimposed high-grade stenosis. A 90% stenosis was generated by external constriction, reducing blood flow to 40 +/- 10% of baseline. Localized thrombosis was produced by endothelial cell injury and instillation of thrombin and fresh blood. Intravenous infusion for 60 minutes of either 30 micrograms/kg/min rt-PA alone or 10 micrograms/kg/min scu-PA alone consistently produced coronary artery recanalization (six of eight dogs and five of five dogs, respectively) but was almost always associated with reocclusion during or shortly after the end of the infusion (four of six dogs and five of five dogs, respectively). Infusion of either 15 micrograms/kg/min rt-PA or 5 micrograms/kg/min scu-PA for 60 minutes did not cause coronary artery recanalization (none of four dogs in each group). Combined infusion of 7.5 micrograms/kg/min rt-PA and 2.5 micrograms/kg/min scu-PA for 60 minutes (one fourth of the minimum thrombolytic dose of each agent) induced coronary artery recanalization (six of six dogs) but was also associated with early reocclusion (six of six dogs). Combined infusion of 3.75 micrograms/kg/min rt-PA and 1.25 micrograms/kg/min scu-PA for 60 minutes did not consistently cause recanalization (one of four dogs). Combined infusion of 15 micrograms/kg/min rt-PA and 5 micrograms/kg/min scu-PA for 60 minutes caused recanalization in all of six dogs but was associated with reocclusion in all six.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Differential sensitivity of erythrocyte-rich and platelet-rich arterial thrombi to lysis with recombinant tissue-type plasminogen activator. A possible explanation for resistance to coronary thrombolysis.

Acute myocardial infarction is triggered by coronary artery occlusion that may be recanalized by thrombolytic therapy with a success rate of up to 75% only. The resistance of coronary artery occlusion to thrombolysis may either be due to obstruction of the lumen by a nonthrombotic mechanism or by intrinsic resistance of thrombus to dissolution. Coronary arterial thrombi are composed of platelet-rich and erythrocyte-rich material in variable proportions. To evaluate the relative sensitivity of these thrombus components to thrombolysis, we have used two femoral arterial thrombosis models in the rabbit, consisting of erythrocyte-rich clot produced by injecting whole blood and thrombin in an isolated segment and of platelet-rich thrombus spontaneously formed on an everted (inside out) femoral arterial segment. Intravenous infusion of recombinant tissue-type plasminogen activator (rt-PA) at a rate of 30 micrograms/kg/min consistently reperfused arteries occluded with erythrocyte-rich clot (six of six animals compared with zero of six placebo-treated animals, p = 0.002), whereas infusion of 30 or 100 micrograms/kg/min was significantly less efficient for reperfusion of everted segments occluded with platelet-rich material (only four of 12 animals, p = 0.01). Intra-arterial infusion proximal to the occlusion, at a rate of 20 micrograms/kg/min reperfused six of seven rabbits with erythrocyte-rich clots but only one of seven rabbits with occluded everted segments (p = 0.03). A dose of 100 micrograms/kg/min was necessary to reperfuse platelet-rich occlusions in five of six rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Correlation between template bleeding times and spontaneous bleeding during treatment of acute myocardial infarction with recombinant tissue-type plasminogen activator.

The purpose of this study was to correlate bleeding complications during and after treatment with recombinant tissue-type plasminogen activator (rt-PA) with serial template bleeding time measurements, with ADP-induced platelet aggregation, with clinical characteristics, and with hemostatic parameters. Fifty-two of 55 consecutive patients with acute myocardial infarction and template bleeding times (Ivy method) of less than 9.5 minutes were treated with rt-PA in a total dose of 55-212 mg (mean, 109 mg) over 90 to 360 minutes (median, 240 minutes) combined with heparin. The mean bleeding time was significantly prolonged at 90 minutes (from 5.0 +/- 1.9 to 8.2 +/- 4.3 minutes, p less than 0.0001) but returned toward baseline after 4 hours (from a median of 8.0 to 7.0 minutes, p less than 0.05). Thirteen patients (25%) suffered relatively minor but spontaneous bleeding that did not correlate with age, hypertension, smoking, partial thromboplastin time, platelet count, ADP-induced platelet aggregation, steady-state rt-PA level, or extent of fibrinogen degradation. In multivariate analysis, only the 90-minute bleeding time correlated with spontaneous bleeding (p = 0.01). Prolongation of the 90-minute bleeding time to greater than or equal to 9 minutes, which occurred in 21 patients, correlated with spontaneous bleeding with a sensitivity of 69% (95% confidence interval, 39-90%) and a specificity of 69% (95% confidence interval, 52-83%). Retrospective analysis revealed that in 14 patients taking aspirin, the bleeding time at 90 minutes was significantly more prolonged (p less than 0.05) and spontaneous bleeding significantly more frequent (p less than 0.01) than in patients not taking aspirin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1988

Transdermal scopolamine-induced psychosis.

Transdermal scopolamine (Transderm-Scop) is being increasingly used for effective prophylaxis of motion sickness. It is reported to have a lower incidence of CNS side effects than orally administered scopolamine. Although uncommon, such side effects occur more often in the elderly, in those with preexisting psychiatric disease, and in patients concurrently taking other medications with anticholinergic activity. Correct diagnosis may be delayed by the occult location of the delivery system, delayed onset of symptoms, prolonged action, absence of peripheral manifestations, and negative toxicologic screening tests. Treatment is usually supportive. Physostigmine should be reserved for the treatment of severe symptoms.

Administration, Cutaneous↗
PubMed1988

Rapid and sustained coronary artery recanalization with combined bolus injection of recombinant tissue-type plasminogen activator and monoclonal antiplatelet GPIIb/IIIa antibody in a canine preparation.

The effects of bolus injections of recombinant single-chain tissue-type plasminogen activator (rt-PA) and of F(ab')2 fragments of a murine monoclonal antibody (7E3) against the human platelet GPIIb/IIIa receptor [7E3-F(ab')2] on coronary arterial thrombolysis and reocclusion was studied in a canine preparation of coronary artery thrombosis superimposed on high-grade stenosis. Bolus intravenous injections of rt-PA at a dose of 0.45 mg/kg, repeated at 15 min intervals until reperfusion occurred (maximum of four injections) caused reperfusion in five of seven dogs within 100 min (33 +/- 15 min, mean +/- SD). Reperfusion was rapidly followed (generally within 10 min) by reocclusion and then by periods of cyclical reflow and reocclusion. A single intravenous injection of 7E3-F(ab')2 alone at 0.8 mg/kg caused reperfusion within 100 min in two of six dogs (19 and 37 min) without subsequent reocclusion. Single bolus injections of different amounts (0.1 to 0.8 mg/kg) of 7E3-F(ab')2 were then combined with bolus injections of 0.45 mg/kg of rt-PA. Stable reperfusion without reocclusion was accomplished with 0.8 or 0.6 mg/kg 7E3-F(ab')2 and a single injection of 0.45 mg/kg rt-PA within 6 +/- 3 min (n = 6, p less than .01) and 8 +/- 5 min (n = 5, p less than .02), respectively. None of these animals suffered reocclusion of the coronary artery. Lower doses (0.1 to 0.2 mg/kg) of 7E3-F(ab')2 did not significantly shorten the time to reperfusion and did not prevent reocclusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Prevention of coronary artery reocclusion and reduction in late coronary artery stenosis after thrombolytic therapy in patients with acute myocardial infarction. A randomized study of maintenance infusion of recombinant human tissue-type plasminogen activator.

Sixty-eight patients with acute "transmural" myocardial infarction presenting within 6 hours (range, 1.3-5.8 hours) of onset of chest pain were given intravenous recombinant tissue-type plasminogen activator (rt-PA) at a dosage of 1 mg/kg during 90 minutes. Coronary angiography at 90 minutes revealed a patent infarct-related coronary artery in 52 patients (76%). These patients were randomized either to treatment by continuous infusion of heparin alone (27 patients) or to treatment by heparin and a maintenance infusion of rt-PA at a dosage of 0.8 mg/kg during 4 hours (25 patients). Coronary angiography was repeated 60 minutes after the start of the maintenance infusion and again after 8-14 days. Acute symptomatic reocclusion of the infarct-related artery occurred during the 1-hour observation period in five (19%) patients treated with heparin alone but in none of the patients treated with rt-PA (p = 0.05). The measured residual stenosis of the patent infarct-related coronary artery was similar in the heparin-treated and the rt-PA-treated groups at 90 minutes infusion: 66 +/- 14% versus 68 +/- 13% diameter stenosis, respectively (mean +/- SD) and 1.1 +/- 1.1 mm2 versus 0.82 +/- 0.7 mm2 area (p = 0.35). At 8-14 days after infusion, residual stenosis was unchanged in the heparin-treated group, but it improved to 55 +/- 17% (p = 0.001) and 1.6 +/- 1.2 mm2 (p = 0.003) in the rt-PA-treated group. At 90 minutes of infusion, residual intraluminal thrombus was observed in 29 of the 52 patients (56%) with a comparably measured distribution in the two groups (p = 0.43). At 150 minutes, however, the extent of intraluminal thrombus was significantly reduced in the rt-PA-treated group as compared with the heparin-treated group (p = 0.03). In-hospital ischemic events (symptomatic reocclusion, unstable angina, or cardiovascular death) occurred in 12 patients of the heparin-treated group but only in three patients of the rt-PA-treated group (p = 0.03). Fibrinogen levels decreased to 65 +/- 21% of baseline at 90 minutes of rt-PA infusion. During the rt-PA maintenance infusion, fibrinogen fell slightly from 63 +/- 26 to 57 +/- 28% (p = 0.18). This study shows that after successful reperfusion with 1 mg/kg rt-PA during 90 minutes, a maintenance infusion of 0.8 mg/kg rt-PA during 4 hours prevents acute symptomatic coronary artery reocclusion, and it reduces the frequency of ischemic events and the severity of residual coronary artery stenosis at hospital discharge.

Aged↗