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A nationwide database confirmed the sharp reduction of adult cardiac surgery volumes and unexpectedly high procedural mortality during the COVID pandemic, one group reported.

Surgical cases had been fairly stable month to month until they dropped to 12,000 across the country during the month of April 2020, a 53% reduction (65% drop in elective cases and a 40% reduction in non-elective cases) from the 2019 monthly average that roughly coincided with the first wave of the pandemic.

The Mid-Atlantic and New England regions, hit hardest by COVID during the first surge, showed the biggest drops of cardiac surgery volumes (71% and 63% reductions, respectively). The Mid-Atlantic in particular had a whopping 75% reduction in elective cases and a 59% decline in non-elective ones in April, reported Tom Nguyen, MD, of University of California San Francisco, at the Society of Thoracic Surgeons (STS) virtual meeting.

These two regions also had spikes in operative mortality: their observed-to-expected (O/E) ratio for mortality rose by 75% from below 1.0 before the pandemic to nearly 1.2 in April. In particular, O/E mortality for isolated coronary artery bypass grafting (CABG) surgeries there jumped by 148%.

Meanwhile, other geographic regions in the U.S. had O/E operative mortality stable at around 1.2, according to the researcher.

"During the COVID-19 pandemic, cardiac surgery volumes suffered dramatically, particularly in New England and Mid Atlantic regions, with a significant increase in the expected mortality​," Nguyen concluded.

According to him, the "COVID effect" on mortality likely represents a combination of lack of preparedness, surgery in the setting of dwindling hospital resources, the volume-outcome relationship in surgery, and selection bias for urgent or salvage cases during the pandemic.

"Now that we know a little more about COVID, we're not seeing as much mortality in the hospital," he said, noting that additional research is being planned using other STS tools.

The study was based on the STS Adult Cardiac Surgery Database, with data on the pandemic linked from the Johns Hopkins COVID-19 database.

This report is the "largest description" of how COVID has affected surgical volumes and outcomes in the U.S.​, Nguyen said.

By July, nationwide case volumes bounced back to approximately pre-pandemic levels -- but not exceeding prior volumes, suggesting a continued backlog of surgeries. "Where did these elective cases go? We haven't seen that deficit come back," Nguyen said.

Study limitations included the lack of granularity in the dataset; for instance, there was no information on COVID-19 status on an individual patient level. Furthermore, the study did not probe the second or third waves of the pandemic.

Overall, the data confirm a directly correlation between COVID-19 and cardiac surgical volumes, said session discussant Ruggero De Paulis, MD, of The European Hospital in Rome, who asked if the reduction in surgeries might be mitigated by having dedicated COVID hospitals.

This may be a moot point, as Nguyen noted that compared with the first surge last spring, the largest, most recent surge in the pandemic was met with a "more tempered approach" in which business generally didn't shut down and the stock market stayed healthy.