The government insurance program for older people paid nearly 4,000 physicians in excess of $1 million each in 2012, according to the new data. Those figures do not include what the doctors billed private insurance firms…

Among the highest billers were a cardiologist in Ocala, Fla., who took in $18.1 million, mainly putting in stents. A New Jersey pathologist who received $12.6 million performing tissue exams and other tests. And a Michigan vascular surgeon who got $10.1 million.

Some of the highest billing totals may simply reflect a physician who is extremely efficient or who has an unusually large number of Medicare patients.