Background Cardiovascular diseases are an important cause of death worldwide, and ischemic heart diseases account for a considerable number of these deaths. COVID-19, a disease caused by SARS-CoV-2, may pose important cardiovascular complications and implications, including acute coronary syndromes. This study aimed to compare prevalence data of acute coronary syndromes during the COVID-19 pandemic period (2020) to the previous year (2019). Methods This is a retrospective, descriptive, analytical, and cross-sectional study, with variables acquired through the analysis of the medical records of all adult patients of both sexes admitted for acute myocardial infarction, unstable angina, and ischemic heart disease between the months of January to December 2019, and January to December 2020, to a cardiology reference hospital in Curitiba (PR). The variables obtained were about diagnosis of these diseases, clinical consultation, laboratory tests, and imaging tests. The data found were then correlated with each other to define possible causal relations. Results There was a 40.38% reduction in the incidence of hospitalizations for the cited diagnoses in 2020 compared to 2019. There was no difference between days of onset of symptom between the compared years, days of hospitalization, or number of comorbidities presented by patients, although there was a higher number of diagnoses of unstable angina and presence of chest pain in individuals seen in 2020. Conclusion The COVID-19 pandemic affected the lives of all people, including the search for care in health facilities and hospitals worldwide, resulting in a lower demand for health services, including for severe and acute diseases, which can lead to increased morbidity and mortality in the population.