Introduction

Double-chambered right ventricle (DCRV) was first described in 1858 by TB Peacock, but it is now understood to be a form of congenital heart disease wherein there is a mid-cavitary obstruction that dived the right ventricle into a high-pressure proximal portion and a low-pressure distal portion.[1] DCRV can classify into two main types based on the tissue responsible for the mid-cavitary obstruction. Patients with type 1 DCRV have an anomalous muscle bundle that crosses the right ventricle while type 2 DCRV has parietal and septal muscle hypertrophy that is responsible for the obstruction, and they often are more likely to present with a ventricular septal defect (VSD).[2] Associated anomalies include VSD (most common and can be seen in up to 90% of DCRV patients), transposition of the great arteries, tetralogy of Fallot, ruptured sinus of Valsalva aneurysm, atrial septal defect, aortic valve regurgitation, persistent left superior vena cava, tricuspid valve regurgitation, Ebstein anomaly, and valvar pulmonary stenosis.[3][4][5]

Etiology

Proposals posit various mechanisms to explain the development of abnormal muscle bundles in a double-chambered right ventricle. They include the following:

1. Increased blood flow among patients with VSD causes hypertrophy of the supraventricular crest resulting in an acquired obstruction.
2. Superior displacement of the septomarginal trabecula or moderator band causes it to undergo progressive hypertrophy over time.
3. Extension of a muscular shelf from the septoparietal trabeculations to the trabecular component of the right ventricular apex in conjunction with other acquired factors results in the formation of obstructive muscle bundles.[6]

Epidemiology

Double-chambered right ventricle presents in 0.5% to 2% of all patients with congenital heart disease.[7] It has a 2 to 1 male to female predilection ratio of presenting at birth.[8] It can present in 10% of children undergoing correction of a VSD, 3.1% of patients who have undergone repair of tetralogy of Fallot, and it can also present atypically in adults with a prevalence of 2.1%.[9]

History and Physical

Patients with isolated double-chambered right ventricle and mild-to-moderate right ventricular outflow tract obstruction (RVOTO) are asymptomatic.[10] When RVOTO is severe, the patient may experience exertional fatigue, dyspnea, light-headedness, or chest discomfort (right ventricular angina). Severe right ventricle hypertension may also lead to right ventricular failure, failure to thrive, and fatigue. If there is an interatrial communication or if the VSD is proximal to the obstruction, cyanosis may occur. Severe RVOTO results in right ventricular heave. The ejection systolic murmur, which is characteristically long and loud, is of maximal intensity in the third or even fourth left intercostal space. The site of the thrill, if present, is also low. A diminished right ventricular cardiac output caused by the small, high-pressure proximal chamber and the relatively low subvalvular pressure allows the pulmonary valve to close earlier. Hence, the pulmonic component of the second heart sound is not too soft or too delayed.

Evaluation

Electrocardiogram

It usually shows right ventricular hypertrophy and right axis deviation, but may have atypical features like dominant R in lead V4R, with only an rS complex in V1. These electrocardiographic abnormalities are attributable to the absence of hypertrophy of the distal right ventricular chamber.

Echocardiography

Transthoracic echocardiography (TTE) often serves as an initial diagnostic modality, but it has been reported to be often less effective than transesophageal echocardiography (TEE), cardiac catheterization, and cardiac magnetic resonance imaging (MRI). The diagnostic effectiveness of TTE has limitations because of the right ventricle’s irregular shape, retrosternal position, and proximity to the precordium; the mid-cavitary turbulent jet on TTE can also be confused for an intracardiac shunt or high right ventricular pressure may be incorrectly assumed to represent pulmonary hypertension.[11] However, these problems can be overcome as the right ventricle and outflow tract may be visualized better, and the turbulent jet can be aligned better to make accurate pressure gradient measurements by using the subcostal view on TTE.[11] The best view for diagnosing DCRV is the subcostal short-axis view in infants and young children. In older patients, the parasternal short-axis view at the level of the aortic valve and subcostal views are useful. TEE allows for better definition of the lesion in the adults. Helpful TEE views include the  mid esophageal 4-chamber view with color flow doppler that can show intracavitary narrowing, the mid-esophageal right ventricular view with color flow doppler of the inflow and outflow areas that can demonstrate anomalous muscle tissue and RVOTO inferior to the pulmonic valve, and the upper esophageal aortic arch short-axis view or transgastric basal right ventricular view with color flow doppler that can help locate the source of turbulent flow in the right ventricle and then measure the pressure gradient through the outflow tract.[12]

Cardiac Catheterization

The pressure data characteristically shows a low pressure tracing in the pulmonary artery, and the infundibular chamber, while the pressure is high (often supra systemic) in the right ventricular apex. Angiography should merit consideration if the pressure gradients cannot be evaluated by echocardiography or if the patient needs evaluation for suspected co-morbid coronary artery disease.

Cardiac MRI

This modality can be helpful as an adjunct to TTE and/or TEE. It is a non-invasive option that can help to confirm the presence of any associated cardiac anomalies, quantify the pressure gradient in the right ventricle, and evaluate the wall thickness of the right ventricle.[3] This is important because it would provide additional information on considering pre-surgical medical therapies versus going directly with surgical intervention not only to resect the anomalous muscle bundle but also fix any associated structural anomalies.

Differential Diagnosis

Double-chambered right ventricle can be mistaken for tetralogy of Fallot, isolated pulmonic valve stenosis, isolated VSD, pulmonary valve stenosis with a VSD causing a left to right shunt, and idiopathic hypertrophic obstructive cardiomyopathy affecting the right side of the heart.[18] The location of the VSD can be helpful. If the VSD connects to the distal low-pressure compartment, it will present similarly to an isolated VSD. But if the VSD connects with the high-pressure proximal compartment, it will present like tetralogy of Fallot; pulmonary flow is also essential to consider as it will be higher in patients with isolated VSD while it will be lower in those with tetralogy of Fallot.[19] Echocardiography will help show that only the left side of the heart is showing structural abnormalities, which would suggest hypertrophic obstructive cardiomyopathy instead of DCRV that is based primarily on right-sided heart pathology.

Prognosis

One study mentions that children who undergo surgery for DCRV had positive long term outcomes, did not require re-operation for any recurrent anomalous tissue acting as an intracavitary obstruction, and did not die in adulthood from complications from the management of DCRV.[20] Outcomes after surgery in adults have also been mostly positive, with minimal mortality noted.[20]

Complications

Complications after surgery are not very likely. However, patients may be at risk for death from low cardiac output states after surgery despite successful resection of the anomalous muscle bundle or heart failure, and they may experience arrhythmias and occurrence of right ventricular dysfunction that would require close follow up and additional interventions.[21]

Deterrence and Patient Education

It is important to discuss with patients about early correction after diagnosis in childhood if possible, to avoid the progressive developments of the anomalous muscle bundles. They should be aware of the positive outcomes reported when patients undergo surgery. If they do still refuse, they should be encouraged to follow up appropriately in the outpatient setting.

Enhancing Healthcare Team Outcomes

For the diagnosis of the double-chambered right ventricle, a high index of suspicion is necessary from the physician, cardiologist, and the cardiothoracic surgeon. It should always receive a thorough preoperative evaluation. Encouraging surgery when appropriate, is important, but patients may refuse. If and when they refuse, alternative options that are not curative but can provide symptomatic relief and reduce future hospitalizations are available and should be offered as well. These should have outpatient follow up with their primary care physician and a cardiologist to monitor them.

Nursing will play a critical role in the management of this condition, primarily by preparing the patient for surgery, monitoring vitals, and assisting during surgery, and administering postoperative care, reporting to the surgeon, or managing physician any concerns that may arise. Only with this type of strong interprofessional team dynamic can patients with a double-chambered right ventricle achieve optimal outcomes. [Level 5]