Antithrombotic Therapy for Cerebrovascular Disorders: Sick Sinus Syndrome

Sick Sinus Syndrome
The risk of cardioembolic stroke in patients with sick sinus syndrome (SSS) is substantial and may approximate 8-10%/year. Patients with SSS who present initially with tachybradyarrhythmias may be at higher risk for embolic stroke than those who have only bradyarrhythmias. The frequent development of AF after SSS diagnosis may identify an additional subgroup at higher risk. It has been suggested that pacemaker insertion might reduce the substantial stroke risk in SSS patients, but this proposition has not been carefully studied. A recent report described 10 SSS patients who developed ischemic stroke after pacemaker implantation. These patients represented 6% of 156 consecutive completed stroke patients, suggesting that this association may not be rare. Eight of the patients had a ventricular demand cardiac pacemaker, 1 an atrial inhibited pacemaker, and 1 a dual-chamber pacemaker. Six patients were taking aspirin and 1 was anticoagulated at stroke onset. Six of the patients developed AF after pacemaker insertion but before their ischemic stroke occurred. This study implies that ventricular demand cardiac pacemakers and aspirin may not substantially alter the stroke risk in SSS patients. The role of anticoagulants for stroke prophylaxis in SSS has not been studied but is an area that needs exploration. read only
Acute Myocardial Infarction
About 2.5% of consecutive patients with AMI experience stroke within 2-4 weeks in recent studies. Stroke complicates about 6% (range, 4-12%) of anterior AMI during the acute course, but only about 1% of inferior AMI unless prior ischemia contributes to ventricular dysfunction. Almost half of emboli occur within 1 week of AMI, another one fourth during the second week, and the bulk of the remainder during weeks 2-12 following AMI. Previously summarized randomized trials of large numbers of unselected patients with AMI demonstrated statistically significant reduction in early stroke risk, 2.9-1.2% in anticoagulated patients compared with nonanticoagulated patients. However, the small absolute magnitude of stroke reduction questions its clinical significance in unselected AMI patients, especially when considering bleeding complications. Hence, recent emphasis has focused on identification of subgroups of AMI patients at high risk for embolism, particularly those with ventricular thrombi detected echocardiographically. However, the issue of antithrombotic prophylaxis for embolism prevention in AMI is often complicated by concurrent use of fibrinolygic agents, aspirin, and/or heparin for limitation of myocardial damage.