Three years ago, the echocardiography group helped develop guidelines for appropriate use of the test. “We all recognized what we needed to do,” said Dr. R. Parker Ward, a cardiologist at the University of Chicago, who helped write the guidelines. He noted that noncardiologists ordered many of the unneeded exams, and that new applications, such as screening cancer patients for early warning signs of heart damage caused by chemotherapy, might expand the use of the tests.

While academic hospitals have led the call for more targeted use of echocardiograms, not all doctors comply, and “it’s a black hole what’s going on in offices,” said Dr. Rory B. Weiner, a professor at Harvard Medical School. There is not even a good estimate of how many of the procedures are performed in the United States, although it is clearly in the tens of millions annually.

The profit margin on the test is impossible to calculate because purchase prices for the machines are secret. GE declined to provide price information for its machines in the United States or other countries. Nor would it reveal how many machines it sold in the United States, other than to say that one-third of its global sales — $330 million out of $1.1 billion — were in this country.

A Boom of Low-Cost Scans

The Sakakibara Heart Institute, one of Tokyo’s finest private clinics, performs about 60 echocardiograms a day, or 16,000 a year.

As in the United States, doctors and hospitals in Japan are paid each time they deliver a service. (Japanese patients’ co-payments vary from 10 to 30 percent.) Perhaps predictably, as in the United States, doctors there order lots of tests.

In Japan, doctors’ visits tend to be brief, but patients expect to leave with a prescription — a drug or a scan. Ultrasounds, a technology developed in Japan, are a favorite. “We test everyone; we can grasp many things with this test,” said Dr. Keitaro Mahara, the director of echocardiography at the institute. “It’s harmless, so the patients can receive it repeatedly.”