Cardiac Findings in Swimming-Induced Pulmonary Edema – Implications for Acute Assessment

BACKGROUND: Pathological cardiac findings have been described in case reports of patients with swimming-induced pulmonary edema (SIPE). RESEARCH QUESTION: To characterize cardiac findings in patients with SIPE. STUDY DESIGN AND METHODS: A cohort study evaluated patients with SIPE and asymptomatic swimmers (controls) participating in Sweden's largest open water swimming event, Vansbrosimningen, in 2022-2024. Transthoracic echocardiogram (TTE), electrocardiogram (ECG) and cardiac biomarkers were assessed within two hours after swimming and at follow-up within 12 months. RESULTS: In total, 45 patients with SIPE and 45 controls were included. Systolic ventricular function on TTE was mildly impaired after swim in 43% of patients and 10% of controls (p=0.003). Systolic pulmonary artery pressure was increased in 30% of patients but none of the controls (p=0.005). TTE pathology had improved at follow-up in all but one patient. Findings on ECG after swim showed no difference between groups (p=0.746). High-sensitivity cardiac troponin I after swim was increased in 67% of patients and 40% of controls (median 47 pg/ml vs 14 pg/ml, p<0.001). N-terminal pro-B-type natriuretic peptide was higher in patients than controls (median 169 pg/ml vs 65 pg/ml, p<0.001). Two patients with myocardial infarction concurrently with SIPE had clinically significant chest pain and high levels of cardiac troponin. INTERPRETATION: In patients with SIPE, transient mildly affected cardiac function on TTE and a small to moderate elevation of cardiac biomarkers is likely to be found. ECG did not differ between groups. This study provides a reference of expected cardiac findings in patients with SIPE. CLINICAL TRIAL REGISTRATION: clinicaltrials.gov: NCT05391737.