Thinking Outside the ‘Cage’
The America College of Cardiology/American Heart Association guidelines for valvular heart disease recommend that patients with mechanical prosthetic aortic valves should be started on a vitamin K antagonist with a target INR of 2 to 3. (Class 1A). Prosthetic mitral and high thromboembolic valves require a higher INR target above 3.0. The addition of antiplatelet agents, such as aspirin in doses of 75 to 100 mg, should be started to decrease risk of thromboembolic disease in all patients with prosthetic heart valves.12
CE is not a common cause of ACS. Nevertheless, it was considered in the differential diagnosis of this patient, and diagnostic criteria were reviewed. This patient met the diagnostic criteria for a definitive diagnosis of CE. These included 1 major and 2 minor criteria: angiographic evidence of coronary artery embolism and thrombosis without atherosclerotic components; < 25% stenosis on coronary angiography except for the culprit lesion; and presence of emboli risk factors (prosthetic heart valve).
CE is rare, and review of the literature reveals that it accounts for < 3% of all ACS cases. Despite its rarity, it is important to recognize its risk factors, which include prosthetic heart valves, valvuloplasty, vasculitis, AF, left ventricular aneurysm, and endocarditis. The difference in treatment between CE and the most frequently encountered etiologies of ACS reveals the importance in recognizing this syndrome. Management of CE remains controversial. Nevertheless, when the culprit lesion is located in a distal portion of the vessel involved, as was seen in our patient, and in cases where there is a low thrombi burden, anticoagulation instead of thrombectomy is usually preferred. Patients with prosthetic mechanical valves have a high incidence of thromboembolism. This sometimes leads to thrombi formation in uncommon locations. Guidelines of therapy in these patients recommend that all prosthetic mechanical valves should be treated with both antiplatelet and anticoagulation therapies to reduce the risk of thrombi formation.
Conclusion
Physicians involved in diagnosing ACS should be aware of the risk factors for CE and always consider it while evaluating patients and developing the differential diagnosis.
