Aorto-ventricular tunnel

Aorto-ventricular tunnel (AVT) is an extremely rare form of congenital heart disease, representing an anomalous extracardiac communication between the ascending aorta and the left or right ventricles.

Terminology

In most cases the anomalous communication is between the aorta and the left ventricle and therefore the term aorto-left ventricular tunnel (ALVT) is used. Rarely the abnormal connection is with the right ventricle, in which case the term aorto-right ventricular tunnel (ARVT) is used instead.

Epidemiology

Approximately 130 cases have been described in the literature, with an estimated prevalence ranging from ~0.001% to ~0.1% of all cases of congenital heart disease . There is a clear male predilection of 2:1, male: female cases. Very few cases have been seen in those with African or Asian ethnicity . 
In ~90% of cases, the connection is between the aorta and the left ventricle; a right ventricle connection only occurs in ~10%.

The anomaly usually occurs in isolation, and does not seem to be part of a syndrome.

Clinical presentation

It can be diagnosed antenatally on routine ultrasonography.

On physical examination, a "to-and-fro" murmur may be appreciated on precordial auscultation, along with an easily palpable pulse (due to rapid aortic runoff).

The commonest presentation is heart failure in the first year of life although there is a wide spectrum of severity, from in utero death, to rapid postnatal heart failure, and even some adults who are entirely asymptomatic.

Pathology

Congenital communication between the ascending aorta, distal to the sinotubular junction, and the left or right ventricles. The communication usually occurs distal to the right sinus of Valsalva.

The anomaly typically occurs in isolation, independent of other anomalies.

The spectrum of severity of the condition is related to the size of the anomalous connection and the degree of aortic incompetence.

Radiographic features

Echocardiography

Transthoracic echocardiography (both 2-D and 3-D have been used) is the modality of choice. The tunnel can be seen in its entirety on the parasternal long-axis view, as can both the aortic and ventricular apertures. On color Doppler the abnormal blood flows between the aorta and left/right ventricle may be seen.

MR angiography

MRA has been used with some success, but is of course, not widely available.

Cardiac catheterization angiography

Rarely used any more in view of its invasive nature and ionizing radiation. It is reserved for the trickier cases, in which non-invasive modalities have been equivocal.

Antenatal US

It can be diagnosed antenatally after gestation week 18. 
In 2015 a new sonographic finding, the cockade sign was described for the antenatal diagnosis of aorto-left ventricular tunnel .

Treatment and prognosis

In the majority of cases, even when the patient is asymptomatic, early surgical intervention is required to prevent permanent left ventricular dysfunction.

History and etymology

The first case, an aorto-left ventricular tract, was reported in 1957 by Jesse E Edwards (1912-2008), American cardiac pathologist , and Howard B Burchell (1908-2009), American cardiologist .

Differential Diagnosis

• sinus of Valsalva fistula
  • a sequela of rupturing an aneurysm of the sinus of Valsalva
  • more caudal location of anomalous connection (aorto-ventricular tunnel affects more craniad tubular aorta)