Despite significant advances in cardiovascular imaging, certain congenital and valvular lesions may remain clinically silent for decades, particularly in individuals with limited medical care. Coexistence of an atrial septal defect (ASD) and severe mitral regurgitation (MR) in adults represents an uncommon clinical constellation, only sporadically described in the literature.1 Early recognition and timely intervention in congenital and valvular heart disease are strongly associated with improved long-term outcomes.2-4

A 59-year-old male music teacher, smoker, with no significant medical or family history, was admitted to a hospital due to recurrent palpitations. He had been taking a low dose of a β-blocker (bisoprolol, 2.5 mg daily). On admission, his vital signs were within normal limits, and electrocardiography (ECG) demonstrated sinus rhythm with a right bundle branch block. A systolic murmur was identified on cardiac auscultation. Routine laboratory test results were unremarkable, except for a mildly elevated N-terminal pro–B-type natriuretic peptide level (498 pg/ml; reference range <⁠125 pg/ml). Twenty-four–hour Holter ECG monitoring showed no atrial fibrillation.

Transthoracic echocardiography demonstrated a large ASD measuring 26 mm in diameter (Figure 1A and 1B), with a pulmonary-to-systemic blood flow (Qp/Qs) ratio of 3.7:1, and a high likelihood of pulmonary hypertension. Additionally, severe eccentric MR was identified (proximal isovelocity surface area [PISA] radius, 13 mm; mitral annulus, 48 mm; Figure 1C and 1D), along with moderate tricuspid regurgitation (TR; tricuspid annulus, 51 mm; vena contracta, 5 mm; PISA radius, 5 mm; Figure 1E and 1F). Left ventricular ejection fraction was preserved at 65%.

Figure 1. Valvular heart disease on multimodality imaging, demonstrating underlying structural and functional abnormalities; A – transthoracic echocardiography (TTE); substernal view showing an ASD (arrow); B – TTE; 4-chamber view showing the ASD (arrow); C – TTE focusing on the MV, with a PISA measurement (arrow); D – TTE showing MR measurements (arrow); E – TTE focusing on the tricuspid valve; measurement of the vena contracta (arrow); F – TTE showing the RVSP measurements (arrow); G – transesophageal echocardiography (TEE) 2-chamber view focusing on the MV and MR (arrow); H – 3-dimesional (3D) TEE showing the MV; view from the atrium; P1/P2 prolapse (arrow); I – TEE; bicaval view of the ASD (arrow); J – 3D TEE; bicaval view of the ASD (arrow); K – TEE; bicaval view of the ASD dimensions (arrow)

Abbreviations: ASD, atrial septal defect; LA, left atrium; LV, left ventricle; MR, mitral regurgitation; MV, mitral valve; PISA, proximal isovelocity surface area; RA, right atrium; RV, right ventricle; RVSP, right ventricular systolic pressure; VC, vena contracta; VTI, velocity time integral

Transesophageal echocardiography confirmed severe primary MR due to P1/P2 prolapse (effective regurgitation orifice area, 0.38 cm2; PISA radius, 9 mm; regurgitant volume, 60 ml; Figure 1G and 1H), moderate TR, and an ASD measuring 21 mm × 15 mm with a left-to-right shunt (Figure 1I–1K). Detailed data on the measurements are presented in Supplementary material, Tables S1 and S2.

The case was discussed by a multidisciplinary heart team, which recommended mitral valve replacement or repair, tricuspid valve annuloplasty, and ASD closure. Prior to final qualification, right heart catheterization (RHC) was performed. Coronary angiography excluded significant coronary artery disease. RHC demonstrated a large left-to-right shunt (Qp/Qs ratio, 3.1:1), elevated pulmonary artery pressures with normal pulmonary vascular resistance, a significant oxygen step-up in the right heart chambers, and an increased pulmonary capillary wedge pressure.

Intraoperative detection of severe leaflet calcification prompted mitral valve replacement with a 31-mm St. Jude Medical mechanical prosthesis (Abbott Laboratories, Abbott Park, Illinois, United States), tricuspid repair with a 34-mm Carpentier–Edwards Physio ring (Edwards Lifesciences Corporation, Irvine, California, United States), surgical ASD closure, and placement of an epicardial pacing lead. The postoperative course was complicated by the development of a third-degree atrioventricular block, requiring implantation of a dual-chamber pacemaker. The patient remains under structured longitudinal surveillance of cardiac surgery, cardiology, and cardiology clinics.

This clinical image illustrates how an apparently benign clinical picture in a middle-aged adult can mask advanced structural heart disease. It highlights the enduring value of careful auscultation, the diagnostic power of imaging, and the importance of decision-making by a heart team. Importantly, an ASD can remain clinically undetected for decades until severe MR and moderate TR cause hemodynamic instability.