Septal branch aneurysm during coronary computed tomography angiography: a cause of right bundle branch block?

Abstract

A 59-year-old male was referred to our institution for a cardiology consultation due to unexplained dizziness and recent episodes of near syncope. He had previously been diagnosed with right bundle branch block (RBBB) (Panel A), which was re-demonstrated on an electrocardiogram. Otherwise, he has been free of chest pain or palpitations. The medical history, however, did include cardiac risk factors such as hypertension, dyslipidemia, and a family history of premature cardiac disease, thus a coronary computed tomography angiography (CTA) was obtained. Multidetector row CTA revealed a focal aneurysmal dilatation of the first septal perforator branch of the left anterior descending artery. This localized pooling of contrast measured 10 mm in diameter was completely surrounded by the interventricular myocardium, and did not communicate with the chambers at either side. There are four prior reports of septal perforator aneurysms in the literature; three of them as an iatrogenic complication after either bypass grafting or septal ablation procedure and the fourth one as an incidental finding in an asymptomatic patient during a diastolic murmur work-up. While the three iatrogenic cases resolved spontaneously, the latter one persisted and has been only under close observation. It is of interest that the presented patient had a known diagnosis of RBBB of unknown aetiology. We postulate that this aneurysm may play a causative role by compromising the conduction through the right bundle by creating direct pressure near its course on the right ventricular subendocardial side of the septum.Panel A. Twelve-lead ECG shows right bundle branch block (QRS widening, 154 ms). Black arrows point to wide terminal S wave (Lead I, V6). The white arrows point to rSR' (Lead V1).Panel B. Multiplanar reconstruction in the short axis near the base re-demonstrates the septal perforator (black arrow) aneurysm (white arrow) and its lack of communication to either chamber. LV, left ventricle; RV, right ventricle.Panel C. Sagittal oblique multiplanar reformation of coronary CTA shows a contrast filled cavity (white arrow) within the interventricular septum arising from the first septal perforator branch (black arrow).Panel D. Axial image of coronary CTA show a contrast filled cavity (white arrow) within the interventricular septum with no communication to either chamber. LV, left ventricle; RV, right ventricle.Published on behalf of the

Structural Causes of Right Bundle Branch Block—Time for a Closer Look?

“…Recently, Shah et al . [5] described a case of a septal branch aneurysm which caused a right bundle branch block by causing direct pressure on the right bundle branch near it’s subendocardial course on the right ventricular side of the interventricular septum.…”