The coronavirus killed tens of thousands in the United States during the pandemic's first months, but it also left a lesser-known toll: thousands more deaths than would have been expected from heart disease and a handful of other medical conditions, according to an analysis of federal data by the Washington Post.

The analysis suggests that in five hard-hit states and New York City there were 8,300 more deaths from heart problems than would have been typical in March, April and May — an increase of about 27% over historical averages.

That spike contributed to Illinois, Massachusetts, Michigan, New Jersey, and New York state and the city having a combined 75,000 "excess deaths" during that period, 17,000 more than the number officially attributed to COVID-19, the disease the virus causes.

While several experts said some of the excess deaths in the analysis were almost certainly unrecognized fatalities from COVID-19, the review suggests that many patients suffering from serious conditions died as a result of delaying or not seeking care as the outbreak progressed and swamped some hospitals.

Normally, heart disease is the leading cause of death in the United States.

But in the early months of the pandemic, some hospital departments were nearly devoid of the heart, cancer, stroke and other patients who populated them before.

More than 50 patients a day "died excess deaths just from heart disease, just in New York City," said Dr. John Puskas, a cardiovascular surgeon at Mount Sinai Hospital in Manhattan. "Frankly, that would explain where all the patients went."

The analysis of data from March 1 to May 30, using a model previously developed by the Yale University school of public health, shows that heart disease is the major driver of excess deaths, excluding those officially attributed to COVID-19.

As states in the South and West restart their economies and see new cases surge, the excess deaths should serve as a cautionary tale, said Dr. Nahid Bhadelia, medical director of Boston University medical school's Special Pathogens Unit.

"This data underlines the importance of not letting our health systems get to the point where they are so overwhelmed that it spills over and affects people with other medical conditions in our community," she said.

Several experts said the spikes in the causes of death in the new Post analysis suggested a deadly collateral effect of the pandemic. They said the surge in deaths from heart disease and several other conditions matches what they saw in clinics and hospitals and confirms their fears that many patients died after not seeking care.

On Wednesday, an article published in the Journal of the American Medical Association bolstered the findings from the Post and CDC analyses. The paper looked at excess deaths nationwide in March and April and found that 35% were attributed to causes other than COVID-19. The researchers, led by a team at Virginia Commonwealth University, concluded that those deaths may include unreported, "nonrespiratory manifestations" of the virus, or they could represent "secondary pandemic mortality caused by disruptions in society that diminished or delayed access to health care."