Aspirin--effective in males threatened with stroke

Antithrombotic Therapy in Valvular Heart Disease—Native and Prosthetic

This chapter about antithrombotic therapy in native and prosthetic valvular heart disease is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following: For patients with rheumatic mitral valve disease and atrial fibrillation (AF), or a history of previous systemic embolism, we recommend long-term oral anticoagulant (OAC) therapy (target international normalized ratio [INR], 2.5; range, 2.0 to 3.0) [Grade 1C+]. For patients with rheumatic mitral valve disease with AF or a history of systemic embolism who suffer systemic embolism while receiving OACs at a therapeutic INR, we recommend adding aspirin, 75 to 100 mg/d (Grade 1C). For those patients unable to take aspirin, we recommend adding dipyridamole, 400 mg/d, or clopidogrel (Grade 1C). In people with mitral valve prolapse (MVP) without history of systemic embolism, unexplained transient ischemic attacks (TIAs), or AF, we recommended against any antithrombotic therapy (Grade 1C). In patients with MVP and documented but unexplained TIAs, we recommend long-term aspirin therapy, 50 to 162 mg/d (Grade 1A). For all patients with mechanical prosthetic heart valves, we recommend vitamin K antagonists (Grade 1C+). For patients with a St. Jude Medical (St. Paul, MN) bileaflet valve in the aortic position, we recommend a target INR of 2.5 (range, 2.0 to 3.0) [Grade 1A]. For patients with tilting disk valves and bileaflet mechanical valves in the mitral position, we recommend a target INR of 3.0 (range, 2.5 to 3.5) [Grade 1C+]. For patients with caged ball or caged disk valves, we suggest a target INR of 3.0 (range, 2.5 to 3.5) in combination with aspirin, 75 to 100 mg/d (Grade 2A). For patients with bioprosthetic valves, we recommend vitamin K antagonists with a target INR of 2.5 (range, 2.0 to 3.0) for the first 3 months after valve insertion in the mitral position (Grade 1C+) and in the aortic position (Grade 2C). For patients with bioprosthetic valves who are in sinus rhythm and do not have AF, we recommend long-term (> 3 months) therapy with aspirin, 75 to 100 mg/d (Grade 1C+).

In vitro bleeding test--a simple method for the detection of aspirin effects on platelet function

We investigated platelet function of 21 healthy blood donors before, 4 hrs and 1 to 7 days after a single oral dose of 0.02 (n = 3), 0.05 (n = 3), 0.1 (n = 3), 0.5 (n = 2) and 1.0 g (n = 10) aspirin. Three additional donors received 0.02 g aspirin/day for 5 days. A new and simple in vitro bleeding test (Thrombostat) using whole blood was far more sensitive than all other tests for platelet function (subaquatic bleeding time, thrombelastrogram, resonance-thrombogram, platelet adherence, spreading and aggregation). With this method using 2mM CaCl2 as additional agent all donors showed significantly increased in vitro bleeding volumes, for at least 2 days after ingestion of 0.1 to 1 g aspirin. In the majority of cases the aspirin effect could be detected even after 5-6 days. In 2 of 3 donors even 0.05 g aspirin was detectable. There was already a definite effect seen after 2 days in all 3 cases when 0.02 g was ingested daily. The new in vitro bleeding test should be suitable for the control of low dose aspirin prophylaxis of arterial thromboembolic disorders.

Increased excretion of immunoreactive thromboxane B2 in cerebral ischemia

Thromboxane B2 (TXB2) is the stable metabolite of thromboxane A2 (TXA2), a potent vasoconstrictor which induces irreversible platelet aggregation. The inhibition of TXA2 by aspirin and other agents has been associated with improved outcome following cerebral ischemia in clinical and laboratory studies. To investigate the relation of TXA2 production to cerebral ischemia, we measured the urinary excretion of TXA2 metabolites in 30 patients with acute cerebral ischemia. Urinary immunoreactive TXB2 for this group of ischemic patients was elevated compared to normals, 1818 +/- 344 pg/mg Cr (mean +/- SE) vs 880 +/- 122 pg/mg Cr (p less than .05). Among various subsets of the ischemic patients, those with severe stroke (2108 +/- 536 pg/mg Cr), large vessel disease (1646 +/- 335 pg/mg Cr), and cardiogenic stroke (2712 +/- 1045 pg/mg Cr) were all significantly elevated. Of the stroke patients, only the males demonstrated this significant elevation. These elevations of urinary immunoreactive TXB2 are consistent with a role for increased platelet activation in the pathogenesis of some forms of cerebral ischemia and suggest that gender differences in arachidonate metabolism may exist for stroke patients.

Evaluating and predicting outcome of acute cerebral vascular accident

An innovative evaluation method is used to study the outcomes and clinical predictions for 97 patients with acute cerebral vascular accidents. The technique involved the participation of several professional disciplines in selecting baseline and treatment variables and making independent predictions about the functional status of patients upon discharge from the stroke treatment center. The data suggest that (1) baseline variables were more important than treatment variables in the participants' predictions about the patients' short-term outcomes; (2) stroke unit staff members were generally successful in predicting patients' functional status; and (3) stroke extensions and other complications are important factors which affect stroke patients' short-term outcomes.

A randomized trial of aspirin and sulfinpyrazone in patients with TIA

In a double-blind multicenter study, 124 patients with transient ischemic attacks were randomly allocated to one of two groups treated with aspirin (ASA) or sulfinpyrazone respectively. Patients were followed up to assess the relative efficacy of the two treatments in the prevention of the outcomes of stroke, myocardial infarction, vascular death, and worsening or no improvement of TIAs. No significant difference was observed between the two treatments at the end of the follow-up period. Statistical analysis revealed a significant interaction of sex, treatment, and occurrence of events. Analysis of the results according to sex showed that male patients treated with ASA had a highly significant benefit (p less than 0.001) with a 53% risk reduction for further events. In female patients, sulfinpyrazone showed a favorable trend which was not statistically significant.

Stenoses of the distal segments of the internal carotid artery

In 31 of 51 patients with stenosis of the distal segments of the internal carotid artery, the first symptom was a transient ischemic attack. In spite of the high incidence of angiographically proved emboli, 46 patients remained in good neurological condition. Aspirin was given to all patients. In 4 patients a total occlusion developed, causing severe neurological deficit. This indicates that the danger of occlusion is significantly higher than that of embolization. External carotid-internal carotid artery bypass was carried out in 23 patients; occlusion developed during the postoperative observation period in 4 patients without any neurological consequences. It can be concluded that an EC/IC bypass operation is the method of choice in treating patients with severe distal stenosis or recent mural thrombi.

Influence of epinephrine on the aggregation response of aspirin-treated platelets

We have evaluated the influence of epinephrine on the sensitivity of aspirin-treated platelets to aggregating agents. Concentrations of ADP, thrombin and arachidonate that caused reversible stimulation of aspirin platelets produced irreversible aggregation when the aspirin samples had been pretreated with epinephrine. The correction was not due to improvement in the ability of aspirin platelets to synthesize prostaglandins or secrete products of the release reaction. Epinephrine induced correction of refractory aspirin platelets may help to explain why aspirin is not a universally effective anti-thrombotic agent.

Further evidence relating mitral-valve prolapse to cerebral ischemic events

Echocardiography demonstrates prolapse of the mitral valve in at least 5 per cent of the population. Since some observations have linked this condition to stroke, we studied its incidence in two groups of patients with cerebral ischemia. The older group contained 141 patients over 45 years of age (mean, 64.7 years) who had transient ischemia or partial stroke. Prolapse was found in eight (5.7 per cent) of these patients and in 10 (7.1 per cent) of 141 age-matched controls. The second group contained 60 patients who had transient ischemia or partial stroke and were under 45 years old (mean 33.9 years). Prolapse was detected in 24 patients (40 per cent) but in only five (6.8 per cent) of 60 age-matched controls (mean age, 33.7 years). The odds ratio, 9.33, was highly significant (P less than 0.001). In six of the 24 patients there were other potential causes for cerebral ischemia leaving 18 whom the only recognizable potential cause was a prolapsing mitral valve (odds ratio, 7.00; P less than 0.001). This study suggests that this entity has a role in cerebral ischemia, at least in younger patients. (N Engl J Med 302:139-144, 1980).

Chronic subdural hematoma presenting as transient neurologic deficits

Four patients with symptoms of transient neurological dysfunction were subsequently found to have chronic subdural hematomas (CSDH). The frequency of these episodes diminished significantly after evacuation of the hematoma. The effects of vascular compromise due to the CSDH and to cardiovascular events, more commonly implicated in transient ischemic attacks (TIAs) may be additive. The inclusion of a computerized axial tomographic (CAT) scan in the evaluation of some patients with presumed TIAs is recommended.

The surgical management of extracranial and intracranial occlusive disease

The role of surgery in preventing transient ischemic attacks and stroke in certain occlusive vascular lesions is well-established. This is well-established when carotid endarterectomy for carotid stenosis with transient ischemic attacks is used. The overall surgical results are best achieved by the frequent performance of the procedure and meticulous attention to technical as well as medical features of this group of patients at risk. Continuing medical care of these patients is essential. The long-term mortality rate is augmented by the high incidence of myocardial infarctions. Complete cardiac evaluation and good medical care, at the time the patient is initially treated, should subsequently minimize this event. Although the microvascular bypass procedures are technically feasible and associated with a low mortality rate, their exact role in the medical management of patients with intracranial occlusive lesions is unproven. However, the procedure offers great promise and an exciting future for neurosurgery in stroke therapy.