Coronary Arteries

The coronary arteries arise from the bulb of the aorta from two openings known as the aortic sinuses (Sinuses of Valsalva) and are the first branches of the aorta, originating just above the aortic valve. They supply oxygen-rich blood to the heart muscle. These arteries run in a wavy path on the surface of the heart, embedded within the fatty tissue of the epicardium.

3 Sinuses exist corresponding with each aortic cusp. The right and left sinuses are the start of the Right Coronary Artery (RCA) and the Left Coronary Artery (LCA) respectively. The third sinus is known as the non-coronary sinus where no vessels arise.

Right Coronary Artery (RCA)

The right coronary artery originates from the right aortic sinus, passing behind the pulmonary trunk and running along the coronary sulcus between the right atrium and right ventricle. It travels down to the inferior (diaphragmatic) surface of the heart, moves toward the apex, and ends as the posterior interventricular branch in the groove between the ventricles.

Along its path a few branches arise:

• Conus branch (Ramus coni arteriosi):
  • The first branch of the RCA, running near the pulmonary trunk and the right ventricle. supplies right ventricular outflow tract
• Sinoatrial (SA) node branch (Ramus nodi sinuatrialis):
  • Loops around the superior vena cava and supplies the sinoatrial node.
• Atrial branches (Rami atriales dextri anteriores):
  • Small branches supplying the right atrium.
• Ventricular branches (Rami ventriculares dextri):
  • These supply the right ventricle. One prominent branch, the right marginal branch (Ramus marginalis dexter), runs along the heart’s right edge toward the apex.
• Septal branches (Rami interventriculares septales posteriores):
  • These branches arise from the posterior interventricular artery and penetrate the back of the interventricular septum.
• As mentioned above RCA then terminates as the Posterior Interventricular Artery which runs in the posterior interventricular sulcus.

Left Coronary Artery (LCA)

The left coronary artery is relatively short, it originates from the left aortic sinus, positioned between the left atrium and the pulmonary trunk. It quickly divides into two main branches:

1. Anterior interventricular branch (Ramus interventricularis anterior):
   • Also known as the left anterior descending artery (LAD), it descends along the anterior interventricular sulcus toward the apex of the heart and may extend to the back (diaphragmatic surface).
   • It gives off:
     • Ventricular branches (Rami ventriculares anteriores sinistri): Also known as Diagonal branches supplying the anterior and lateral walls of the left ventricle.
     • Septal branches (Rami interventriculares septales anteriores): Small branches penetrating the interventricular septum from the front.
2. Circumflex branch (Ramus circumflexus):
   • Wraps around the back of the heart, following the groove between the left atrium and left ventricle (coronary sulcus).
   • It gives rise to:
     • Atrioventricular branches (Rami atrioventriculares): Supplying the area between the left atrium and left ventricle.
     • Left marginal branch (Ramus marginalis sinister): Supplies the left border of the heart and runs toward the apex.
     • Atrial branches (Rami atriales): Supplying the left atrium.
     • Posterior branch of the left ventricle (Ramus posterior ventriculi sinistri): A terminal branch that may replace the posterior interventricular artery in 10% of cases.

Coronary Artery Dominance:

1. Right Dominance (~70-85%):
   • Posterior interventricular artery arises from the right coronary artery (RCA).
2. Left Dominance (~8-10%):
   • Posterior interventricular artery arises from the circumflex branch of the left coronary artery (LCA).
3. Codominance (~5-7%):
   • Posterior interventricular artery receives contributions from both RCA and LCA.

Coronary Veins

Coronary veins return deoxygenated blood to the right atrium:

1. Coronary sinus:
   • The largest vein, located on the back of the heart. It drains blood from:
     • The great cardiac vein (running with the LAD).
     • The middle cardiac vein (running with the posterior interventricular artery).
     • The small cardiac vein (associated with the RCA).
2. Thebesian veins:
   • Tiny veins draining directly into the heart chambers directly, primarily the right atrium and right ventricle. these can be seen as tiny holes in the walls of the chambers.

Nerves of the Heart

The cardiac plexus is a network of nerves that innervates the heart, regulating its autonomic functions. It is divided into two parts: the superficial cardiac plexus and the deep cardiac plexus.

Superficial Cardiac Plexus

• Located beneath the aortic arch and anterior to the right pulmonary artery.
• Formed by the superior cervical cardiac branch of the left sympathetic trunk and the inferior cardiac branch of the left vagus nerve.
• Supplies the deep cardiac plexus, anterior coronary plexus, and left anterior pulmonary plexus.

Deep Cardiac Plexus

• Located posterior to the aortic arch and anterior to the tracheal bifurcation (carina).
• Formed by branches from the superior, middle, and inferior cervical ganglia of the sympathetic trunk, and cardiac branches of the vagus and recurrent laryngeal nerves.

The autonomic innervation of the heart influences the cardiac frequency, impulse velocity and force of contraction.

Sympathetic increases heart rate frequency and contractility

Parasympathetic innervation has the opposite effect.

Coronography (Coronary Angiography)

Coronarography is an imaging technique used to visualize the coronary arteries. A catheter is inserted through an artery (usually the femoral or radial artery), contrast dye is injected, and X-ray images are taken. This helps diagnose blockages or narrowing in the coronary arteries and guides treatments like stent placement or bypass surgery.

References:

• Gray's Anatomy: The Anatomical Basis of Clinical Practice Standring, S. (Ed.). (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice (42nd ed.). Elsevier.
• Clinically Oriented Anatomy Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2018). Clinically Oriented Anatomy (8th ed.). Wolters Kluwer.
• Atlas of Human AnatomyNetter, F. H. (2018). Atlas of Human Anatomy (7th ed.). Elsevier.
• Sobotta Atlas of Human AnatomyPaulsen, F., & Waschke, J. (2023). Sobotta Atlas of Anatomy (17th ed.). Elsevier.