Arterial supply of heart

ANATOMY • THORAX • HEART

Coronary Arteries of Heart

Coronary Arteries of Heart — Anatomy Study Notes

01

Coronary Arteries of Heart

The heart is supplied by two coronary arteries, arising from the ascending aorta.

Both arteries run in the coronary sulcus.

02

Features of Coronary Arteries

  1. Blood flows through these arteries during diastole of heart.
  2. Left coronary artery is larger in calibre and supplies more myocardium.
  3. These arteries are functional end arteries.
  4. Their branches anastomose with each other.
  5. However, one artery cannot compensate for the other in case of thrombosis.
  6. The origin of the posterior interventricular artery determines the dominance of the artery.
  7. Sympathetic stimulation:
  • Dilates the intramuscular arteries.
  • Constricts the epicardial arteries.
  1. They are prone to development of atherosclerosis.
03

Right Coronary Artery

Position

  • Smaller than the left coronary artery.
  • Arises from the anterior aortic sinus of the ascending aorta.

Course

1. First Segment

  • Passes forwards and to the right.
  • Emerges on the surface of the heart between:
Root of pulmonary trunk
Right auricle

Then runs downwards in the right anterior coronary sulcus to the junction of the right and inferior borders of the heart.

2. Second Segment

  • Winds around the inferior border to reach the diaphragmatic surface of the heart.
  • Runs backwards and to the left in the right posterior coronary sulcus.
  • Reaches the crux of the heart.
  • Terminates by anastomosing with the circumflex branch of left coronary artery at the crux (60%).

Branches

1. Atrial Branches

Anterior
Posterior
Lateral

SA Nodal Artery

  • One of the anterior atrial branches.
  • Arises from the right coronary artery in 60% cases.
  • In 40% cases, it arises from the circumflex branch of the left coronary artery.

2. Right Conus Artery

  • Forms an arterial circle around the pulmonary trunk with a similar branch from the left coronary artery.
  • This circle is called annulus of Vieussens.

3. Ventricular Branches

Two groups:

Anterior group
Lies on the sternocostal surface.
Posterior group
Traverses the diaphragmatic surface of the heart.

4. Right Marginal Artery

  • Arises as the right coronary artery crosses the right border of heart.
  • Runs along its inferior border till the apex of heart.

5. Posterior Interventricular Branch

  • Arises close to the crux of heart.
  • Lies in the posterior interventricular groove.
  • Gives:
a. Septal branches → for posteroinferior 1/3rd of interventricular septum.
b. Nodal branch → in 60% individuals, for AV node.
c. Ventricular branches → for inferior surface of right and left ventricles.

Area of Distribution

  1. Right atrium
  2. Ventricles
    • Greater part of right ventricle, except the area adjoining the anterior interventricular groove.
    • Small part of left ventricle adjoining the posterior interventricular groove.
  3. Posterior 1/3rd of interventricular septum.
  4. Whole conducting system of heart, except a part of the left branch of the AV bundle.
SA Node

SA node is supplied by the left coronary artery in about 40% cases.

04

Left Coronary Artery

Position

  • Larger than the right coronary artery.
  • Arises from the left posterior aortic sinus of ascending aorta.

Course

  1. First runs forwards and to the left.
  2. Emerges between:
    Pulmonary trunk
    Left auricle
  3. Here it gives the anterior interventricular branch, which runs downwards in the groove of the same name.
  4. The further continuation of the left coronary artery is called the circumflex artery.

Anterior Interventricular Artery

  • Descends along the anterior interventricular groove.
  • Turns around the inferior heart border.
  • Enters the posterior interventricular groove.
  • Ends by anastomosing with the posterior interventricular artery.

Circumflex Artery

  • Runs to the left in the left anterior coronary sulcus.
  • Winds around the left border of the heart.
  • Continues in the left posterior coronary sulcus.
  • Near the posterior interventricular groove, terminates by anastomosing with the right coronary artery.

Branches of Left Coronary Artery

1. Anterior Interventricular Artery / Left Anterior Descending (LAD) Artery

It gives:

a. Anterior ventricular branches

Supply the sternocostal surface of right and left ventricles.

b. Diagonal artery
  • Largest anterior ventricular artery.
  • Occasionally arises from the junction of:
Anterior interventricular artery
Left circumflex coronary artery
c. Left conus artery

Supplies pulmonary conus.

Septum Branches

Supply anterior 2/3rd of interventricular septum.

2. Left Circumflex Coronary Artery

It gives:

a. Ventricular branches

Supply:

  • Sternocostal surface
  • Left surface
  • Inferior surface of left ventricle
b. Atrial branches

Supply adjacent area of left atrium.

c. Sinoatrial nodal artery

Arises from left circumflex coronary artery in 40% individuals.

d. Left marginal artery

Runs along the left heart border towards the apex.

e. Posterior interventricular artery

Left circumflex coronary artery continues as posterior interventricular artery in 10–20% individuals.

f. Kugel’s artery
  • An atrial branch of left coronary artery.
  • Anastomoses with a similar branch of right coronary artery along the anterior wall of atria.

Area of Distribution

  1. Left atrium
  2. Ventricles
    • Greater part of left ventricle, except the area adjoining the posterior interventricular groove.
    • Small part of right ventricle adjoining the anterior interventricular groove.
  3. Anterior 2/3rd of interventricular septum.
  4. A part of the left branch of AV bundle.
05

Cardiac Dominance

  • In about 10% of hearts, the right coronary artery is rather small and cannot give the posterior interventricular branch.
  • In these cases:
    • The circumflex artery, which is the continuation of the left coronary artery, provides the posterior interventricular branch.
    • It also supplies the AV node.
    • Such cases are called left dominant.
  • Mostly, the right coronary artery gives the posterior interventricular artery.
  • Such hearts are called right dominant.
  • Therefore, the artery giving the posterior interventricular branch is the dominant artery.
06

Anastomosis of Coronary Arteries

Interarterial Circulation

Coronary arteries, though end arteries, do anastomose:

In interventricular septum
As Kugel’s arteries near crux of heart
As annulus of Vieussens around pulmonary trunk
Rate of Anastomosis

Rate of anastomosis is better in older persons.

Arteriovenous Anastomosis

  • Blood from a blocked artery flows back into the veins and into the coronary sinus, giving nutrition to myocardium.
  • Branches of coronary arteries divide into a number of sinusoids, which drain into the coronary sinus.
  • Some branches of coronary artery may open directly into the chambers of the heart.
  • Venae cordis minimi open directly into the cavity of right-sided chambers.
  • Blood in the various chambers supplies some of the myocardium.

Cardiac Anastomoses

The two coronary arteries anastomose with each other in the myocardium.

Extracardiac Anastomoses

Coronary arteries anastomose with:

  1. Vasa vasorum of the aorta
  2. Vasa vasorum of the pulmonary arteries
  3. Internal thoracic arteries
  4. Bronchial arteries
  5. Pericardiacophrenic arteries
  • The last three anastomose through the pericardium.
  • These channels may open up in emergencies when both coronary arteries are obstructed.
  • Retrograde flow of blood in the veins may irrigate the myocardium.
  • These anastomoses are of some practical value.
  • They may provide an alternative source of blood in case of blockage of a branch of a coronary artery.
  • Blockage of arteries or coronary thrombosis usually leads to death of myocardium.
Myocardial Infarction

This condition is called myocardial infarction.

07

Clinical Anatomy

01

Ischaemic Heart Disease

  • Ischaemic heart disease is a condition in which myocardium does not receive adequate supply of blood and oxygen.
  • Coronary atherosclerosis is the major cause of ischaemic heart disease.

Classification According to Severity

1. Angina pectoris Stable Unstable
2. Myocardial infarction
3. Heart failure
4. Arrhythmias
5. Sudden cardiac death
02

Angina Pectoris

  • Pain occurring in the chest due to reduced blood (oxygen) supply to the heart.
  • Angina is paroxysmal and usually consists of recurrent attacks of:
    • Substernal chest discomfort
    • Precordial chest discomfort
  • Caused by transient (15 seconds to 15 minutes) myocardial ischemia.
  • This ischemia is insufficient to induce necrosis of cardiac myocytes.

Pain is Described as

Heavy
Tight
Gripping
Typically retrosternal.

Pain is Also Referred To

Left shoulder
Medial side of arm
Medial side of forearm
03

Stable Angina

Begins on exercise or physical activity.

04

Unstable Angina

  • Occurs at rest.
  • Lasts for more than 20 minutes.
  • Pain gets relieved by putting sorbitrate tablets below the tongue.
05

Myocardial Infarction (Heart Attack)

  • A sudden occlusion of a branch of coronary artery leads to complete loss of blood supply of a specific area of the heart.
  • In this area:
    • Myocardium undergoes infarction (reduced blood supply).
    • Finally progresses into necrosis (tissue death).

Symptoms of Myocardial Infarction

Angina pectoris lasting longer than 30 minutes
Nausea and vomiting
Shortness of breath
Sweating
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