The COVID-19 pandemic disrupted healthcare delivery worldwide, beginning in early 2020. While cardiac non-invasive testing (NIT) plays a critical role in the evaluation and management of cardiovascular disease, the population-level association of pandemic-related public health measures on cardiac diagnostics remains unclear.

To compare the rates and patterns of cardiac NIT before and after the implementation of the first and subsequent provincial COVID-19 lockdown measures.

A population-based and registry-based retrospective time series analysis conducted in Ontario, Canada, a single-payer healthcare system.

All individuals receiving transthoracic echocardiography, stress echocardiography, nuclear imaging, cardiac CT or cardiac MRI between 17 March 2018 and 16 March 2022.

Standardised weekly testing rates compared across pre-pandemic and pandemic intervals using ARIMA (autoregressive integrative moving average) modelling.

Among 5 269 897 cardiac tests performed, the cumulative rates decreased from 228.8 (95% CI 228.5 to 229.0) tests per 100 000 person-weeks in the pre-pandemic period to 204.3 (95% CI 204.0 to 204.5) tests per 100 000 person-weeks in the pandemic period (p

During the COVID-19 pandemic in Ontario, cumulative cardiac NIT rates declined significantly and did not fully recover by early 2022. The magnitude and patterns of these declines raise concerns about delayed cardiovascular diagnoses while also signalling a possible shift in diagnostic strategies. Efforts should prioritise preserving access to essential diagnostic testing during future health crises.