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A 31-year-old man presented at another institution with a 1-year history of mild dyspnea on exertion. A cardiac murmur was found, and he was referred to our hospital. Physical examination revealed a 4/6 systolic murmur with an audible thrill from the 2nd to 5th intercostal spaces along the left sternal border. Electrocardiography (ECG) indicated complete right bundle branch block. Transthoracic echocardiography (TTE) showed high turbulent flow from the proximal right ventricular outflow tract (RVOT) to the subpulmonary area. Continuous-wave Doppler echocardiography revealed a pressure gradient of 80 mmHg. Transesophageal echocardiography showed a secundum-type atrial septal defect, a left-to-right shunt at the atrial level, and a muscular band near the RVOT. Angiography confirmed an atrial left-to-right shunt and indicated a systolic pressure gradient of 50 mmHg between the right ventricle and the subpulmonary area.
The patient underwent contrast-enhanced cardiac computed tomographic (CT) imaging by 64-slice multidetector-row computed tomography (MDCT) scanner (Aquilion 64, Toshiba Medical Systems Corporation; Tokyo, Japan) with retrospective ECG gating within a single breath-hold. The acquisition protocol was as follows: 0.5-mm section width, 400-msec gantry rotation time, a tube voltage of 120 kVp, and a tube current of 500 mA. The images revealed an anomalous muscle bundle extending from the interventricular septum to the free wall of the right ventricle, and discontinuities at the middle portion of the interatrial septum and at the membranous portion of the interventricular septum. The patient underwent surgical correction of the double-chambered right ventricle (DCRV) and the atrial and ventricular septal defects.
Most adults with DCRV have other cardiac anomalies, but atrial septal defects are uncommon in such patients.1 Physical examination usually reveals a loud murmur, and ECG indicates right ventricular hypertrophy in patients with DCRV.2 Cardiac angiography and noninvasive imaging are important for the differential diagnosis. Transthoracic echocardiography is of limited use for examining the right ventricle because of that chamber's irregular sharp and retrosternal location, especially in adults.3 In our patient, TTE did not reveal any muscular bundles. Cardiac angiography has been reported to have better sensitivity for identifying DCRV in adults,3 and it may demonstrate the pressure gradient of DCRV by pressure tracing. Pullback pressure record reveals a decrease of end-diastolic pressure from the pulmonary artery to the RVOT with the same systolic pressure. However, a systolic pressure gradient is seen from the RVOT to the right ventricle, which is compatible with RVOT stenosis. Anomalous muscle bundles, however, are not always easily detected on ventriculograms, because they often appear to be insignificant in the diastolic phase.
Cardiac CT is performed under a single breath-hold condition to minimize the effect of respiratory motion artifacts in reconstructed images. The scan time is substantially reduced to avoid involuntary diaphragmatic and residual motion.4 Magnetic resonance imaging (MRI) provides high-quality images of DCRV; however, the overall study time with MRI is longer than that with CT, and metal can cause local field distortion in MRIs.5 Our case illustrates that 64-slice CT is a noninvasive imaging method that provides clear anatomic images of DCRV, atrial septal defect, and ventricular septal defect. Few cases of DCRV evaluated with use of MDCT have been reported.6
Address for reprints: Po-Ming Ku, MD, Department of Cardiology, Chi-Mei Medical Center, No. 901, Jhong-hua Rd., Yong-kang City, Tainan County, Taiwan. E-mail: moc.liamg@gnimopuk