Coronary-cameral fistula with double-chambered right ventricle: appearance on cardiac magnetic resonance imaging and 3D printed anatomic modeling

Abstract

The present case illustrates cardiac magnetic resonance imaging (MRI) and three-dimensional (3D) printed anatomic model findings of a coronary-cameral fistula (CCF) and double-chambered right ventricle (DCRV). A pregnant woman presented with palpitations and near syncope. A non-contrast cardiac MRI showed CCF connecting to a DCRV. Post-delivery, the patient had a contrast-enhanced MRI and 3D printed anatomic model to better evaluate her aberrant anatomy.

1. Background

Double-chambered right ventricle (DCRV) is an uncommon congenital cardiac anomaly common in children that occurs when the right ventricle cavity is split into a high and low-pressure cavity by either a hypertrophied muscular or fibrous partition [1]. Depending on the location of the hypertrophied muscle, patients can present with significant right ventricular obstruction [1]. Coronary-cameral fistulas (CCF) are generally asymptomatic connections between the coronary arteries and ventricles that can be congenital or acquired due to trauma [2]. CCF treatment may require transcatheter or surgical intervention especially if the CCF leads to a hemodynamically significant shunt. Symptomatic CCFs can lead to congestive heart failure caused by progression in the left-to-right shunt, endocarditis, or a steal phenomenon causing myocardial ischemia [3]. In this report, we present a case of a 25-year-old pregnant woman presenting with palpitations and near syncope found to have a CCF connected to a DCRV. Her anatomy was better visualized and understood using cardiac magnetic resonance imaging (MRI) techniques and a three-dimensional (3D) printed anatomic model.

2. Case report

A 25-year old pregnant woman with a history of a restrictive perimembranous ventricular septal defect (VSD) presented at 14 weeks estimated gestational age with palpitations and near syncope. Electrocardiogram demonstrated a wide complex tachycardia which spontaneously reverted to sinus rhythm. Transthoracic echocardiogram showed normal left ventricular (LV) size and systolic function, but the right ventricle (RV) was enlarged with a thick-walled cystic-appearing structure at the apex (not pictured). Non-contrast electrocardiogramgated cardiac MRI was performed to further define the enlarged cystic structure found on echocardiogram. MRI demonstrated a coronary-cameral fistula (CCF) connecting a dilated and tortuous left anterior descending (LAD) coronary artery to a double-chambered right ventricle (DCRV). Following an uneventful pregnancy and delivery, a postpartum contrast-enhanced cardiac MRI was performed to further delineate the non-contrast MRI examination (Figs. 1 and 2). MRI data were used to segment the cardiac and extra-cardiac anatomy and subsequently 3D print an anatomic model of the double chamber right ventricle supplied by the CCF (Fig. 3abc). The 3D printed anatomic model shows the anatomic relationship of the translucent double-chambered right ventricle (Fig. 3, shown in green) supplied by the aberrant left coronary artery and CCF (Fig. 3, shown in red). Postpartum catheterization showed a markedly ectatic LAD with a small CCF to the DCRV and small channels through the fibrous band connecting both RV chambers (not pictured). The patient was started on warfarin because of the slow flow in her ectatic LAD and right ventricular apex. The patient had an episode of recurrent hemodynamically stable ventricular tachycardia managed with amiodarone and mexiletine. She declined both implantable cardioverter-defibrillator and ventricular tachycardia ablation procedures.

Fig. 1.

A) Individual 2-D images from a gadolinium-based contrast enhanced respiratory navigator, ECG-gated whole heart cardiac MRI shows dilated coronary artery (arrow) B) joining right ventricle apex (arrowhead).

Fig. 2.

Static transverse (A and B) and cine 4-chamber and 3 chamber long axis (B and C) A) SSFP imaging show the coronary-RV connection (single thin arrow), the B) apical chamber (multiple thin arrows), and the D) dilated LAD coronary artery (single thick arrow).

Fig. 3.

3D segmentation and 3D printed anatomic model. A) 3D computer reconstruction of LCA and CCF with associated tributaries that flow into B) green DCRV. C) 3D computer re-construction with all cardiac chambers and pulmonary vasculature. D) 3D printed model of patient anatomy showing LCA (thin white arrow) and clear double right ventricle chamber (thick white arrow). E) Posterior image of 3D printed model CCF and tributaries (white dashed arrow) within clear DCRV.Key: SVC- Superior Vena Cava, RA- right atrium, RV-right ventricle, Pulm Artery: Pulmonary Artery, Pulm Vein- Pulmonary Vein, Ao- Aorta, LCA- left coronary artery, CCF- coronary cameral fistula, DCRV- double chamber right ventricle, LV-Left Ventricle.

3. Discussion

DCRV is an uncommon congenital or acquired cardiac anomaly, occurring in 0.5% to 2% of patients with congenital heart disease [4] and is rare as an isolated anomaly. CCF, even more rare, is estimated to occur in 0.07% of patients [5]. Patients with DCRV often require multiple modalities for diagnosis or planning treatment including echocardiography, right heart catheterization, and MRI [6]. Our patient's DCRV was diagnosed with multiple different modalities, with high-resolution, contrast-enhanced 3D respiratory-gated cardiac MRI showing enough anatomic detail to provide a three-dimensional (3D) printed anatomic model of the patient's unique anatomy. While most cardiac MRI sequences are 2D, 3D printing requires a high resolution 3D data set [7]. To obtain this we used a high resolution (1.2 mm isovolumetric) gradient-recalled (GRE) sequence with both prospective respiratory navigator and electrocardiographic (ECG) gating with an inversion pulse to null the myocardial signal in comparison to the contrast-enhanced blood pool [8]. Scanning was performed on a standard whole body 1.5T scanner (Aera, Siemens, Erlangen, Germany) using standard torso phased-array coils. Contrast (0.1 mmol/kg gadobenate dimeglumine) was infused intravenously, with half of the dose administered prior to imaging at 2 mL/secs, and the remainder administered during image acquisition at a slow drip of 0.1 mL/secs [8].

DCRV pathology can be caused by increased ventricle septal defect aberrant flow or abnormal development of outflow cushions that generally form the subpulmonary infundibulum and the supraventricular crest. Either of these etiologies may account for the patient's anatomy in this report. Treatment for symptomatic DCRV generally involves myomectomy for symptomatic right ventricular outflow tract obstruction. In our patient, the apical location of the fibromuscular band in our patient did not result in outflow tract obstruction. Instead, the patient in the current report had a DCRV combined with a coronary-cameral fistula (CCF). Conceivably a CCF and DCRV paired association may be due to right ventricular outflow tract malformation affecting coronary development. Coronary artery development is multifactorial and involves complex interactions between the developing cardiac chambers, outflow tract, and aorta [9,10].

Along with various imaging and diagnostic modalities, 3D printing has been used more frequently to generate anatomic models of congenital cardiac anomalies [11-12]. The Radiological Society of North America 3D Printing Special Interest Group's published a consensus document on the appropriateness of various 3D printed anatomic models used in various cardiac anomalies [11]. Although that appropriateness document does not specifically include double chamber right ventricle, a 3D printed anatomic model may be helpful for treatment and diagnosis of select right ventricle anomalies and pathologies . The present case had unique cardiac anatomy that posed multiple challenges to model and plan treatment. For this patient, 3D computer modeling and printed structures were useful for visualizing and contextualizing complicated anatomy including the connection between the CCF and double chamber right ventricle. In conclusion, this case highlights the utility of cardiac MRI and 3D printing technology in the diagnosis of a patient with unusual right ventricle and coronary anatomy.