01(20): The irony of the innominate artery, and other things

One of my topics this semester is Pathophysiology. According to the topic co-ordinator, the “purpose of this topic is to introduce you to the pathophysiology of the cardiovascular system with a special interest in Acute Coronary Syndrome (ACS) & ECG Interpretation. The cardiovascular system is an integral part of every patients’ [sic] presentation and understanding its function in health and disease is essential for optimal assessment and managment [sic] of your patients. This topic will briefly review cardiac A&P, then analyse the cardiac conduction system and what happens when it becomes pathological in cardiac emergencies such as ACS, STEMIs & cardiac failure.”

The content this week consisted of a review of cardiac anatomy and physiology. Allow me to share some stuff I found interesting.

1. Below is an image that depicts some of the main branches of the aorta.

What I wish to talk about is the brachiocephalic artery. Did you know that apart from its alternative name, brachiocephalic trunk, it has yet another name? The brachiocephalic trunk is also known as the innominate artery. How ironic. Yet, it is interesting to note that “brachiocephalic artery/trunk” started getting coined earlier than “innominate artery”. Why then is this trunk described as “brachiocephalic”? As I discussed in a previous post, a lot of medical jargon consists of Greek and Latin roots cobbled together. In this case, the term “brachiocephalic” can be broken down into “brachio-” and “-cephalic”. The former and latter terms mean “arm” and “head” respectively. It is easy to see how in many cases, the name of something gives a clue as to its function. It is thus not surprising to learn that the innominate artery supplies blood to the right arm, head, and neck.

2. Another thing I found interesting was the word coronary. Why are the coronary vessels described as “coronary”? For a long time, I thought this adjective came from the Latin word for heart – “cor”. However, the true etymology is such that the word comes the Latin word “corona”, which means “wreath” or “crown” (cf Elizabeth II’s coronation in 1952).

In the image above, the green line is the interface of contact between the crown and the person’s head. The way the right and left coronary arteries encircle the heart makes the term “coronary” an apt descriptor.

3. What do you know about the coronary dominance of hearts?

As I watched the video, this diagram came up. What is depicted above is the most typical form of the heart. Here, the posterior interventricular artery branches from the right coronary artery. However, as I saw this diagram, I thought to myself: “Wow, the end of the right coronary artery is so close to the end of the circumflex artery. I wonder if they join together, in some people, to produce a true “crown” that encircles the heart.”

Regarding coronary dominance, according to the video at least, dominance of the coronary arterial system is defined by which artery gives rise to the posterior descending artery (PDA)/posterior interventricular artery. Apparently, the PDA arises from the RCA (see image below) 60-80% of the time. Hence, we don’t normally talk about a “right dominant heart” because that is usually the assumption.

In a minority of people, the PDA arises from the circumflex artery, which ultimately comes from the left coronary artery. The hearts of such people would be termed “left dominant”.

In an EVEN smaller minority of people, the PDA would arise from both the circumflex artery and the right coronary artery. Such people are said to have co-dominant hearts.

Interesting, isn’t it? It turned out my intuition was right after all. Haha.

Yours faithfully,
Nic Loh
8 March 2019

References
1. https://www.youtube.com/watch?time_continue=488&v=xSnFf62GDBI

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