Cardiologists are struggling to understand why hospital presentations for ACS plummeted during the initial COVID-19 lockdown in 2020, even in regional Australia with low rates of the virus.

Patient reluctance to attend hospital during the pandemic seem unlikely to be the main reason for the dramatic reduction, they believe.

A review of cardiology admissions and out-of-hospital cardiac arrest (OOHCA) ED presentations at the John Hunter Hospital in Newcastle compared the COVID lockdown period of 23 March to 31 May 2020 with the same dates in 2018 and 2019 and a pre-lockdown period of 6 January to 15 March 2020.

The study, published in Open Heart, found lockdown led to a significant decline in total cardiology and NSTEMI admissions.

“The number of ACS admissions per day was 4.4 in 2019 compared with 2.4 during COVID-19 isolation, which is a 45% reduction,” the study authors said.

“The IRR of NSTEMI admissions during isolation compared with 2019 was 0.59 (95% CI 0.47 to 0.73), p value <0.0001.”

Primary catheterisation laboratory activation rates for STEMI were also significantly lower during the COVID-19 isolation period.

“The IRR of STEMI presentations for the isolation period compared with 2019 was 0.24 (95% CI 0.14 to 0.40), p value <0.0001.”

“This was not accompanied by a change in OOHCA presentations to the major tertiary centre of the region.”

There was also no difference in symptom to balloon time for those with STEMI comparing prior time periods to COVID-19 isolation.

The study said the incidence of COVID-19 during the study period was 0.14 per 100,000 per day.

The investigators said the “profound effect” of lockdown on the incidence of STEMI was remarkable.

Possible reasons included the overall reduced incidence of respiratory infections in the community due to social isolation, activity modification during lockdown, and the fear of contracting COVID-19 from healthcare facilities.

“However, the most dramatic difference was on catheter laboratory activation for STEMI. This would be predicted to be the least affected, due to the typically more severe nature of symptoms, if patient reluctance were contributing to reductions in presentations.”

Senior investigator Dr Allan Davies, from the cardiology department at John Hunter Hospital, told the limbic that the data was purely observational but hypothesis generating.

“Perhaps what is bad for you in the long term isn’t so bad for you in the short term in terms of sitting around at home and not doing intense physical activity.”

“A sedentary lifestyle is not good for patients longer term but … there was something about that time period that had a pretty dramatic reduction especially in STEMI.”

He said they were planning to collect the data for the same period this year but anecdotally, the numbers of patients were steadily coming back without any obvious rebound effect.