The branching pattern of the human cardio-vascular tree is as unique as one’s fingerprint. One such hugely variable anatomy is the SA nodal blood supply.
Certain salient features
- Variation can be seen in origin, course, and termination.
- Now it is estimated to arise from RCA in 70% (Moved up from 55% in old studies )
- From LCX (25%)
- Dual SA node supply(5%)
- Direct from Aorta
It is heartening to find this good anatomical review on this topic.
A) From the Right Coronary Artery; (B) From the Left Circumflex Artery (proximal); (C) From the Left Circumflex Artery (distal); (D) From the Left Coronary Artery; (E) From the Aorta; (F) Dual origin from the Right Coronary Artery and the Left Circumflex Artery. Image source : Vikse J, PLoS ONE 11(2): e0148331
Implication for the surgeon
The whereabouts of this tiny, yet important artery is critical to the surgeons’ as they incise and explore the atrial roof. (A gateway, that gives access to so many cardiac surgeries) The SA nodal artery mostly goes retro caval but it can be peri-caval or even anterior to SVC.
This image shows (a,b,c) the course in relation to SVC, Developmentally as the venous pole go posteriorly to fix the SA artery behind it.Image source : Vikse J, PLoS ONE 11(2): e0148331
For the Interventional cardiologist
A rare but distinct mechanical compression of SA node artery is reported with large ASD closure device. The plane of compression is usually occurring in the superior aspect of IAS when the SA node artery cross over the RA to reach the SA node. Should be suspected whenever unusual bradycardia occurs during the manipulation of the device or just after deployment. Always mind the delicate gap between the antero superior rim and disc where SA nodal artery is likely to trespass.
AV node Ischemia with ASD device
With precise imaging modalities, new secrets are emerging. Additional AV node arteries from proximal RCA is documented.This is a surprising learning point for us. This artery is referred to as the right superior descending artery, which provides an alternative blood supply to the AV node from the proximal right coronary artery. The transient compromise of this hitherto unknown AV nodal twigs by the ASD device cause AV blocks. With this new info, we also got an answer to one more lingering question, why would disproportionate bradycardias are observed in inferior MI even when distal RCA is flowing well. We can’t blame high vagal tone always.
A CT angiogram showing how the ASD device encroaches the SA node artery. Image Source:Tsunehisa Yamamoto JACC 2016 (Linkedbelow)
The original article has an excellent video clipping of how an ASD device hugs the SA node at the superior edge of ASD.
Final message
Human anatomy is not the subject meant to be read in the first-year medical school cadavers, & forget thereafter. Surprisingly. the field of anatomy is also evolving with new mysteries exposed by modern imaging.SA nodal arterial blood supply is one such interesting aspect of cardiac anatomy. Young fellows in cardiology shall pursue further anatomical dark spaces in the heart (One such topic is how cardiac lymphatics compete with the venous system in draining cardiac interstitium)
Reference
It’s gratifying a unique and committed group exclusively doing research in Anatomy. It Department of Anatomy, Jagiellonian University Medical College, Krakow Poland.
Dr.S.Venkatesan MD 