Double-chambered right ventricle (DCRV) is an uncommon congenital malformation in which anomalous muscle bundles dissect the RV into two chambers. It is commonly associated with other congenital anomalies, most frequently perimembranous ventricular septal defect (PM-VSD). The majority of DCRV cases present early in life, however, infrequently it will manifest in adulthood. The nonspecific nature of the symptoms may be in part responsible for a delayed diagnosis. Surgical intervention of DCRV in adults is uncommon and long-term outcome is unclear.1)2)3)4) We herein report five patients with DCRV and PM-VSD with varying clinical presentation and different treatment strategies.

DCRV is considered an acquired cardiac defect. While there may be a genetic predisposition for abnormal muscle band formation that contributes to this anomaly, it has not been clearly elucidated.1)2) The majority of DCRV cases are diagnosed and repaired early in life, however, it infrequently manifests in adulthood, because of the nonspecific nature of symptoms leading to a delayed diagnosis.3) RVOT obstruction is progressive in adults, and patients may present with effort dyspnea. In affected individuals with a significant mid RV obstruction surgical intervention of DCRV is indicated. However long-term outcome is unclear.4)

Various mechanisms of DCRV have been postulated. Superior displacement of the septal marginal trabecula (moderator band) has been proposed, particularly in association with a VSD, and flow turbulence in the RVOT.1) This flow turbulence may trigger abnormal hypertrophy of the moderator band leading to DCRV. This might elucidate the concomitant association between DCRV and VSD.5)6)

TTE is an important first line diagnostic tool in congenital heart disease, but may have limited visualization of DCRV in adults due to the retrosternal position and asymmetrical shape of the RV. TEE is an excellent supplementary tool to assist delineation of the RV abnormalities as well as assess and quantify the severity of RV cavitary obstruction. Recently, contrast computed tomography and CMR have been introduced in the identification of DCRV. Those diagnostic tools are now sufficiently mature to preclude the need for invasive testing.7)8)9)

Surgical intervention is indicated in symptomatic patients or in asymptomatic patients where the peak gradient exceed 40 mm Hg.3)9) Different approaches for resection of the anomalous muscle bands can be utilized; including a right atriotomy, a right ventriculotomy, or a combined transatrial-transpulmonary access.3)4)9) The right atriotomy and the combined transatrial-transpulmonary incision are used most commonly. Right ventriculotomy is used rarely because of the presence of RV dysfunction or it can result in ventricular arrhythmias. Nonetheless, in select cases patients with massive and prominent bundles, right ventriculotomy is still used.3)4)9)

The pentad of cases presented show the diverse expressions of DCRV from a 'forme fruste' to highly symptomatic. All cases had an associated PM-VSD with abnormal muscle bundles in the RVOT. In the first patient, the main presenting symptoms were shortness of breath and chest pain. She was initially asymptomatic with an isolated small VSD discovered early in life. However, she developed progressive symptoms with a significant gradient across the RVOT in a relatively short period of time which warranted surgical repair. The second patient presented with shortness of breath later in life. She was initially asymptomatic with an isolated VSD discovered at age of 30. Nevertheless, she developed progressive symptoms with significant gradient across the RVOT which warranted surgical repair, but declined by the patient. The third one was born with patent ductus arteriosus, treated with surgical ligation early in life, and a small VSD. She was asymptomatic and developed DCRV later in life with no significant gradient across the RVOT. The fourth patient was born with VSD which warranted surgical closure at age of 12 years. He was asymptomatic and developed DCRV after VSD closure with no significant gradient across the RVOT. The fifth patient was asymptomatic, diagnosed initially with an isolated VSD. He developed DCRV later with no significant gradient across the RVOT. This series of patients reinforces the theory that progressive obstruction in DCRV, with concomitant VSD, might be an acquired phenomenon on a background of a genetic predisposition. The triggers for phenotypic expression or progression thereof are unclear.9)10)