Introduction It is difficult to diagnose atrial septal defect (ASD) in asymptomatic young healthy individuals even with ASD being the most common congenital heart disease. If left untreated, it leads to pulmonary hypertension (PHT) in 6% to 35% of cases.

Case Presentation During routine military health assessment in September 2023, a 30-year-old active serviceman was noted to have an abnormal chest X-ray (CXR) which was reported as right hilar haziness consistent with chronic infection resembling Pulmonary Tuberculosis (PTB). Unfortunately, no further assessment was done until he was called back 9 months later for re-evaluation. Repeated CXR showed similar findings and working diagnosis of Latent TB infection (LTBI) was made as he remained asymptomatic. The case was discussed with us for initiation of LTBI treatment. Upon revisiting both CXRs, noted the signs of left main pulmonary artery (mPA) enlargement was overlooked and confirmed with lateral view CXR. His ECG changes were not classical for PHT, but incomplete RBBB with RAD and S wave in V6 in addition to Crochetage Sign in Lead 3 and aVF raised the suspiciousness of neglected ASD with PHT. His Echo confirmed the presence of mild PHT changes with enlargement of right sided chambers. Although resting bubble test was negative but with modified Valsalva manoeuvre early bubble crossing was detected with evidence of negative filling defect. TOE confirmed 1.3cm Secundum ASD. He was then referred for device closure under IJN.

Discussion The above-mentioned ECG changes is common among Athlete’s heart especially in men. Hence, in the setting of managing an active military personnel, enlargement of the mPA is often overlooked and reported to be normal especially in young patient with lower lobe infection. If CXR changes are interpreted along with the ECG findings, pathological cause such as PHT can be diagnosed.

Conclusion Knowing the art of assessing medical health in military personnel is an essential component for early detection and diagnosis of Secundum ASD with PHT by careful ECG and CXR evaluation. If left undiagnosed, ASD can lead to multiple long-term complications which can be mitigated with early and timely defect closure.