This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Aerial disorders, Subject name: Surgery
An ankle-brachial index (ABI) that suggests increased risk of myocardial infarction would be 
Select and explain. 
A. <0.9, B. <0.6, C. >0.9, D. >0.6
A: <0.9
Answer: A: <0.9 
Explanation: There is increasing interest in the use of the ankle-brachial index (ABI) to evaluate patients at risk for cardiovascular events. An ABI less than 0.9 correlates with increased risk of myocardial infarction and indicates significant, although perhaps asymptomatic, underlying peripheral vascular disease.