For a related story, see rankings on hospitals for weight-loss surgery.

Patients have a 70% higher chance of dying at the nation's lowest-rated hospitals than at the best ones, according to the 11th annual HealthGrades Hospital Quality in America Study, issued Tuesday by HealthGrades ( HGRD), an independent health care ratings organization.

From 2005 to 2007, 237,420 Medicare patients' deaths could have been prevented if all hospitals performed at the level of five-star-rated hospitals, said the study, which took into account 17 procedures and conditions. That represents 12% of all Medicare patient deaths. Five is the highest rating, three is average and one is the lowest. Extrapolating information that included all operations, the number of deaths prevented would have been much higher, said study co-author Rick May, a surgeon and a senior physician adviser to HealthGrades.

Although overall death rates declined, the country's best-performing hospitals reduced death rates at a much faster clip than poor performers, resulting in large state, regional and hospital-to-hospital variations in quality of care, May said.

The best area in the country to undergo hospitalization or surgery and survive was the so-called rust belt in the Midwest, home to General Motors ( GM), Ford ( F) and Chrysler, according to May. The worst region was most of the Deep South. The study did not publish names of individual hospitals.

Some 128,749 deaths, or 54% of the total, were associated with four conditions: sepsis (a life-threatening illness caused by systemic response to infection), pneumonia, heart failure and respiratory failure. The study supports research and academic papers that show hospitals performing a higher number of operations lead to better outcomes, the doctor said.

If you liked this article you might like

Driving This Beastly Cadillac CTS Reminded Me That Sexism Is Alive and Well

Your Complete Guide to Living Like Billionaire Warren Buffett

Irma and Harvey Busted Algos; Probably Done Deals Under Trump: Best of Cramer

Your Guide to Making a Lot of Money on the Driverless Car Boom

How to Live Just Like Billionaire Warren Buffett