The federal government deserves a modest pat on the back for identifying hospitals that have the very best — and very worst — mortality rates for cardiac patients. One can only hope that the information will goad underachieving hospitals into improving their performance. Unfortunately, the ratings are too broad to help most patients decide which institution they can entrust with their lives.

The new ratings — based on how many Medicare patients die within 30 days of being admitted for a heart attack or heart failure — were published by federal Medicare officials last week as part of a growing movement to provide more information to medical consumers and to hold hospitals accountable for the quality of care they deliver.

While the hospitals were told how they scored and were given data allowing them to compare their performance with other institutions, the public is being kept mostly in the dark. No mortality numbers for any institution were published. The hospitals instead were lumped into three broad categories — “better than the national rate,” “worse than the national rate” and “no different than the national rate” — with more than 98 percent placed into the vast middle category.

Of nearly 4,500 hospitals evaluated for heart attack outcomes, 17 were rated better than the national rate, 7 were rated worse and 4,453 were placed in the middle category. Of some 4,800 hospitals evaluated for heart failure outcomes, 38 were better than the national average, 35 were worse and 4,734 were rated no different than the national average.

The Medicare agency justified its refusal to publish the death rates for individual hospitals on the grounds that a shift in the period studied might modify the results while a small, chance increase in the number of deaths at hospitals that treat few patients could have a big impact on their mortality rates. Those are understandable concerns, but the result is a ratings list that will do most consumers little good.

Famed medical institutions like Johns Hopkins, the Cleveland Clinic and Massachusetts General Hospital are lumped into the broad national average category when perhaps they deserve better (we can’t tell), and no doubt many other hospitals deserve a lesser ranking. In the next round of evaluations, the Medicare program ought to make public every institution’s mortality rates along with any caveats needed to help patients understand them.