Introduction

An aorticoventricular tunnel, sometimes referred to as an "aorto-ventricular tunnel," is an abnormal endotheliazed channel between the ascending aorta and a cardiac chamber.[1][2] The left ventricle is the most common location for this anomalous connection (more than 90% of the time), though right ventricular involvement has also been described.[3][4][5]

The tunnel most frequently originates just cephalad to the sinotubular junction over the right coronary sinus. This location of the aortic orifice differentiates a tunnel from a ruptured sinus of Valsalva aneurysm. The ventricular orifice is just below the aortic valve (proximal) in the interleaflet triangle of the left and right leaflets.[6] An aorticoventricular tunnel does not pass through intracardiac myocardium on its path to the ventricular cavity, differentiating it from a coronary-cameral fistula.[7]

The surgical classification of the 4 types of aortico-left ventricular tunnel was introduced in 1988:

• Type I: a simple tunnel with a slit-like aortic orifice and no aortic valve distortion
• Type II: an aneurysmal extracardiac aortic wall component, an oval aortic orifice, with or without aortic valve distortion
• Type III: an aneurysmal intracardiac component (septal), an oval orifice, with or without right ventricular outflow tract obstruction
• Type IV: a combination of types II and III

Proper classification of aorticoventricular tunnel cases guides management strategies and prognosis.[8] 

Etiology

The etiology of aorticoventricular tunnels remains unknown. Some theories include abnormal differentiation of the primordial muscle that forms the base of the left ventricle or failure of the outflow cushions to develop.

Epidemiology

The exact incidence of aortico-left ventricular tunnel is unknown, but the condition is extremely rare, especially as an isolated lesion. In the largest series, aortico-left ventricular tunnel exists in less than 0.5% to 1% of hearts with other congenital malformations.[9] This anomaly has been reported approximately twice more frequently in men, and nearly half of all patients have other associated congenital cardiac anomalies. The most commonly associated congenital cardiac anomalies are proximal coronary artery and semilunar valve abnormalities, bicuspid aortic valve, and ascending aortic dilatation.[10][11]

Pathophysiology

Aortic-to-ventricular tunneling results in steal from the aorta to the ventricle during diastole without impacting systemic circulation during systole. This phenomenon results in volume overload of the affected ventricle, leading to ventricular hypertrophy and dilation with subsequent heart failure. Most patients present in the first year of life with a murmur or heart failure symptoms. However, the presentation timing can vary.

Results from a study of 31 patients had an age range of a few months to 62 years, with about 50% presenting older than 18. However, a recent literature review of aortico-left ventricular tunnels showed a median age at diagnosis of 25 days, with 77.8% undergoing surgery before the age of 6 months.[12] These variations in presentation have not been associated with anatomic classification but with the size and location of any aneurysmal component. Specifically, outflow tract obstruction or coronary artery compression has been associated with earlier presentation and sudden death.[13]

History and Physical

Symptoms of an aortico-left ventricular tunnel, if present, would be consistent with heart failure. The symptoms may include tachypnea, labored breathing, feeding intolerance, and failure to thrive in infants and children. Adults may present with palpitations, chest pain, fatigue, or shortness of breath.

On cardiac exam, patients with an aortico-left ventricular tunnel have a to-and-fro murmur that radiates throughout the precordium, often associated with systolic and diastolic thrills. Patients often have a normal 2nd heart sound, distinguishing this lesion from severe aortic valve regurgitation. This finding is usually associated with low diastolic blood pressure and bounding peripheral pulses. 

Evaluation

Radiography

Chest radiography in these patients may show pulmonary edema or cardiomegaly. A prominent bulge of the enlarged right aortic sinus or a dilated ascending aorta may also be evident.

Electrocardiogram

Electrocardiography (EKG) may show varying degrees of left ventricle and atrial hypertrophy. Left ventricle hypertrophy EKG findings include increased amplitude or duration of the QRS complex with a left shift in the frontal plane, T wave changes, and ST-segment deviation.[14] Left atrial enlargement would be indicated by a P wave greater than or equal to 110 milliseconds in any lead or a notched P wave with an interpeak duration greater than or equal to 40 milliseconds.[15]

Echocardiography

Transthoracic echocardiography is the primary test to identify an aorticoventricular tunnel.[16][17] Diagnosis of an aortico-left ventricular tunnel is suggested by findings that may include flow through the tunnel, a dilated aortic root, and aortic valve insufficiency. Echocardiography can also identify concomitant congenital heart lesions. Tunnels may be identified on fetal echocardiography after 18 weeks gestation.[18][19][20] 

Computed tomography and magnetic resonance imaging

Cross-sectional imaging with cardiac computed tomography and magnetic resonance imaging with angiography can help identify the relationship of the tunnel to nearby structures and the course it takes.[21][22] Prospective gated cardiac computed tomography with contrast can provide additional details. These imaging modalities are increasingly used to assist with operative planning and may be helpful when considering a catheter-based intervention.[23]

Cardiac catheterization

Cardiac catheterization is indicated when the diagnosis is in question or if better delineation of associated defects is needed.[24] Catheterization may also be used to obtain invasive hemodynamic measurements in the setting of severe heart failure.

Treatment / Management

Treatment guidelines for aortico-left ventricular tunnels have not been established. However, experts agree that surgical closure of the aortico-left ventricular tunnel should be performed shortly after diagnosis.[25][26] While closure is rarely emergent or urgent, early correction prevents ventricular volume overload. Thus, patients should be referred to an experienced pediatric and congenital heart disease program. Care should be assumed by a pediatric or adult congenital cardiologist (depending on the patient's age), a congenital cardiothoracic surgeon, and possibly an interventional cardiologist.

Medical Treatment

Medical management should only be used for symptomatic control of heart failure while awaiting surgical repair. Patients who are asymptomatic typically do not require medical therapy while awaiting surgery. However, patients with active heart failure symptoms, eg, dyspnea, tachypnea, and failure to thrive, may need treatment to improve these symptoms before surgery. Treatment typically includes loop diuretic therapy, eg, furosemide or bumetanide.

Mild respiratory symptoms may be managed with oral diuretic therapy on an outpatient basis. More severe respiratory manifestations may require inpatient treatment with intravenous diuretic therapy, with the addition of supplemental oxygen if needed to maintain adequate peripheral oxygen saturation. Infants who are losing weight or not gaining weight (failure to thrive) may require enteral or intravenous caloric supplementation for medical optimization before undergoing surgical repair.

Surgical Treatment

Open surgery is the most established and commonly used approach for the closure of an aorticoventricular tunnel. Many techniques have been described, often modifying surgery based on the specific tunnel anatomic type. All surgical techniques are undertaken via a median sternotomy. Heparin is given after opening the pericardium, and the heart is cannulated for cardiopulmonary bypass with mild hypothermia using arterial access in the aorta and venous drainage from the right atrium or both vena cavae. The aorta is cross-clamped, and the heart is arrested with a high-potassium cardioplegia solution delivered into the aortic root or selectively to the coronary artery ostia. The aorta is opened to identify the origin of the tunnel once the heart is arrested. The trajectory to the exit site, including aneurysmal tissue, should be delineated. 

The commonly described methods for closing the tunnel include suture obliteration of the tunnel's aortic side, patch closure of the aortic side only, and patch closure of both the aortic and ventricular sides. Dacron, glutaraldehyde-treated autologous pericardium, polytetrafluoroethylene, and bovine pericardium have all been used for patch techniques, anchored to the tissue with polypropylene suture material.

The aorta is closed after the repair is completed. Some cases require external obliteration of aneurysmal tissue in addition to the closure procedure. Concomitant cardiac lesions are typically repaired in the same operation. Liberation from a cardiopulmonary bypass requires a transesophageal echocardiogram to confirm the absence of intracardiac air and ensure adequate cardiac repair.

Catheter-Based Treatment

Transcatheter closure of the tunnel may be performed by an interventional cardiologist with experience closing intracardiac shunts, as described in more recent reports.[27][28] This procedure involves femoral arterial access through a sheath placed using a modified Seldinger technique under ultrasound guidance. The tunnel is crossed with a wire that enters the left ventricle after defining the anatomy with an angiogram. An intracavitary occlusive device, eg, a plug, disc, or coil, is placed in the tunnel. An angiogram is performed, and a transesophageal or transthoracic echocardiogram is used to confirm the position and ensure that the device does not interfere with the aortic valve before deployment. This option is limited to tunnels not located near a coronary ostium and in the absence of additional intracardiac lesions, such as aortic valve regurgitation, that should also be repaired surgically during tunnel closure.

Differential Diagnosis

A to-and-fro murmur and low diastolic blood pressure are concerning for an intracardiac-shunting lesion leading to diastolic runoff. The differential diagnosis includes:

• Aortico-left ventricular tunnel
• Patent ductus arteriosus
• Sinus of valsalva fistula
• Aortic valve regurgitation
• Aortopulmonary window

A careful clinical evaluation and appropriate diagnostic examination can help differentiate these conditions and determine the proper management strategies.

Prognosis

Most patients with aortico-left ventricular tunnels develop progressive heart failure if untreated, though a few survive to adulthood without symptoms. Untreated cases produce shunts, resulting in native aortic valve insufficiency that worsens the left ventricular volume load and contributes to cardiac failure. Early repair typically leads to the eventual normalization of the left ventricle size and function due to decreasing volume load.[29] Outcomes of surgically repaired aortico-left ventricular tunnels are generally good in the modern era. A recent large multicenter review revealed that early operative mortality, ie, within 30 days of surgery, was 8.3%, and all early deaths were related to severe residual aortic valve insufficiency and heart failure. Long-term survival was 93.8% at a median follow-up of 22 years in the same study.

Complications

Residual or recurrent aorto-ventricular tunnels can be seen early or late after surgical repair.[30] Patients are generally at risk of progressive aortic valvular regurgitation and aneurysmal aortic root dilatation later in life.[31] Thus, routine follow-up with a cardiologist is recommended for surveillance even after surgical correction of an aortico-left ventricular tunnel. 

Postoperative and Rehabilitation Care

Postoperatively, all patients who undergo aortico-left ventricular tunnel repair should be admitted to an intensive care unit that specializes in their care. The interprofessional team should include, at a minimum, an intensivist, a cardiac surgeon, a cardiac anesthesiologist, and a cardiologist. Children should be in pediatric-specific units cared for by pediatric-trained clinicians. Depending on the clinical status, the patient may require mechanical ventilation and hemodynamic support with vasopressors or inotropes in the first 24 to 48 hours postoperatively. Cardiac function may take longer to improve in cases with more severe or longstanding heart failure preoperatively, prolonging intensive care needs. 

Given the rarity of this lesion, guidelines have not been established regarding follow-up or surveillance after repair. This part of the management remains at the discretion of the treating surgeon and cardiologist. Association with other findings, ie, other lesions or concomitant aortic valve insufficiency, would likely prompt a closer, more frequent follow-up. An echocardiogram is typically performed at discharge from the hospitalization of the index operation and every few months until cardiac function appears stable. Patients should remain in the care of a congenital cardiologist, even in the absence of scheduled imaging.

Deterrence and Patient Education

Patients with aortico-left ventricular tunnel should continue routine health maintenance care by their clinician. These individuals should also be followed by a cardiologist for routine lifelong cardiac function surveillance. The frequency and duration of follow-ups can be determined individually based on the severity of the patient's disease and the presence of any residual lesions after repair.

Enhancing Healthcare Team Outcomes

Patients with congenital heart disease should be under the supervision of an interprofessional team. The team should include the primary care provider, a pediatric or congenital cardiologist, an interventional cardiologist experienced with congenital heart lesions, and a congenital cardiothoracic surgeon. The decision to perform surgical or catheter-based closure of the defect and the timing of such procedures should be made on a case-to-case basis, with full input from the interprofessional team. Institutional experience with certain procedures should be considered in these decisions. Perioperatively, patients require specialized care by pediatric anesthesiologists and intensive care providers. Even after surgical correction, patients with congenital heart disease require lifelong follow-up to prevent and manage the cardiac disease sequelae. 

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Disclosure: Tracy Geoffrion declares no relevant financial relationships with ineligible companies.

Disclosure: Madonna Lee declares no relevant financial relationships with ineligible companies.