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The sinoatrial node artery (SANa) has significant anatomic variability
and some variants have been described to be associated with a greater
risk of iatrogenic injury during surgical or percutaneous procedures.
An 11-year-old boy affected by pulmonary atresia with intact ventricular
septum was evaluated at our center for a follow-up visit. He had
previously undergone multiple percutaneous pulmonary valvuloplasty.
Given the echocardiographic finding of significant gradient through the
pulmonary valve and spontaneous right-to-left atrial shunt, the boy was
listed for the fourth percutaneous pulmonary valvuloplasty and
percutaneous closure of multi-fenestrated atrial septal defect (ASD).
The largest ASD was located antero-superiorly just behind the Aorta. A
static sizing by using an 18 mm Amplatzer® Sizing Balloon (Abbott,
Plymouth, MN) showed a stretched diameter of 11 mm. In addition, a
patent foramen ovale (PFO) and a small, more central, ASD were found.
Intraprocedural transesophageal echocardiography (TEE) showed an unusual
flow behind the non-coronary aortic sinus, rising the suspect of
abnormal coronary artery pattern (figure 1). For this reason, selective
coronary angiography was performed. Left coronary angiogram documented a
single SANa having a course compatible with the echocardiographic
finding. Indeed, this artery appeared to originate from the left
circumflex coronary artery (LCCA), turn posteriorly, run close the
non-coronary aortic cusp, cross the antero-superior interatrial groove
and continue with a precaval course towards the sinoatrial node (figure
2). Coronary angiography highlighted the proximity relationship between
the ASD and the SANa, the latter intersecting the antero-superior rim of
the interatrial septum. On the basis of the haemodynamic data collected,
after successful pulmonary valvuloplasty, we proceeded with the ASD
closure by using a 30 mm Gore® Septal Occluder device (WL Gore &
Associates, Flagstaff, AZ) deployed in the central side hole rather than
a self-centering device in the larger antero-superior ASD.
At the end of the procedure, good conformation of the device and absence
of residual shunts were documented. The left coronary artery (LCA) was
rechecked by selective coronary angiography: the SANa ran adjacent to
the device, without being touched by it (figure 3). The ECG didn’t show
any changes in the heart rhythm. The follow-up was uneventful.
Pulmonary atresia with intact ventricular septum (PA-IVS) is a rare
congenital heart disease (3% of congenital heart disease, with an
incidence of 4-8 out of 100,000 live births). It can be associated with
anomalies in the development of the coronary arteries, linked to the
peculiar pathophysiology that leads to the creation of
ventriculo-coronary fistulas or atretic coronary
tracts.1 To our knowledge, no anomalies in the course
of the SANa associated with PA-IVS have been reported to
date.2
Autoptic or imaging study described a wide anatomical variability of the
SANa in the general population, regarding either the origin and the
course.3–6 Most commonly, SANa arises from right
coronary artery (RCA)(54-68% of cases) or from LCCA (22-40% of cases).
Regarding the relationship with the superior vena cava, SANa can present
a retrocaval or a precaval or a pericaval course. The former is
described to be about 47% of total cases and is the most frequent in
the case of origin from the LCA/LCCA in the European population. The
precaval and pericaval courses follow, representing respectively 39%
and 14% of the total cases. High risk anatomical variants, such as
S-shaped artery, are described to be more associated with possible sinus
node dysfunction during surgical or percutaneous procedures, which
involve a manipulation of atrial walls or interatrial
septum.3,4 They must be taken into account to prevent
iatrogenic injuries. In fact, the damage of the SANa is associated with
dysfunction of the sinus node and the onset of arrhythmias, such as
junctional rhythm or supraventricular tachycardia.7–9
Saremi et al (2008) in a study of 250 patients undergoing coronary CT,
described 13.9% of cases having the S-shaped variant, which originated
from LCCA, turned posteriorly and passed in a groove at the junction
between the orifice of the left upper pulmonary vein and the mouth of
the left atrial appendage. Only one third of these cases presented a
precaval course.4
In our case, conversely, the SANa didn’t embrace the left atrial
appendage and the superior left pulmonary vein: after detaching from the
LCCA, our SANa immediately turned posteriorly with an acute angle
towards the non-coronary aortic cusp, crossed the antero-superior rim of
the interatrial septum and continued with a precaval course towards the
atrial sinus node (figure 4).
In conclusion, our case describes a new variant of SANa course, which
crossed the antero-superior groove of the atrial septum, found in a
patient with AP-IVS. Despite a coronary angiography is not routinely
performed before ASD closure, a careful echocardiographic assessment of
the defect, and the surrounding structure as well, is mandatory to
minimize the risk of procedural complications. Indeed, it can be
speculated that at least part of the ASD closure procedures complicated
by rhythm alterations (0,6-2,7% of cases),10 such
as junctional rhythm or supraventricular tachycardias, might sometimes
be due to an unrecognized SANa course anomalies.