A Hidden Shunt Behind Post-COVID-19 Dyspnea: Partial Anomalous Pulmonary Venous Connection.

Persistent exertional dyspnea following SARS-CoV-2 infection is frequently attributed to post-viral pulmonary pathology. When symptoms are accompanied by right ventricular (RV) dilation and pulmonary hypertension without elevated left-sided filling pressures, alternative etiologies including congenital heart disease must be considered. A 52-year-old man with prior COVID-19 pneumonia presented with one year of progressive exertional dyspnea. Transthoracic echocardiography demonstrated preserved left ventricular systolic function with RV dilation. Right heart catheterization revealed mild precapillary pulmonary hypertension with a significant oxygen saturation step-up at the superior vena cava-right atrial level. Cardiac computed tomography angiography confirmed partial anomalous pulmonary venous connection (PAPVC) with a sinus venosus atrial septal defect. This case emphasizes the necessity of maintaining a broad differential in patients with persistent dyspnea following COVID-19, cautioning against anchoring bias toward post-viral sequelae. While initial suspicion focused on Group 3 pulmonary hypertension, the findings of RV dilation and a normal pulmonary capillary wedge pressure mandated further investigation. This suggests that the acute pulmonary insult may have physiologically unmasked a previously compensated, hemodynamically significant PAPVC. Ultimately, the integration of invasive hemodynamics, specifically identifying an oxygen saturation step-up, and multimodality imaging is essential to identify rare but correctable congenital anomalies in adults presenting with non-specific respiratory complaints.