Blood Supply of Heart

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 BLOOD  SUPPLY  OF  HEART

(Arterial  Supply  &  Venous  Drainage  of  Heart)


ARTERIAL  SUPPLY  OF  HEART

  • The heart is supplied mostly by 2 coronary arteries – right & left.
  • Only the inner endothelial surface of the heart gets nutrition directly from blood in the cardiac chambers.
  • Each coronary artery is a vasa vasorum of the ascending aorta.
  • Anatomically, coronary arteries are not end-arteries, because they anastomose at pre-capillary level.
  • Functionally, they behave like end-arteries, since most of the anastomoses remain impervious.

RIGHT  CORONARY  ARTERY

Origin

  • It arises from the anterior aortic sinus of ascending aorta.

Course

  • Course of the artery can be divided into 2 segments –
    • First segment – from origin to the inferior border of heart
    • Second segment – from inferior border of the heart to crux

At first it passes forwards and to the right between pulmonary trunk and right auricle

Then it passes downwards and to the right along the right part of atrio-ventricular groove

It winds round the inferior border of heart

Passes upwards and to the left along the posterior part of atrio-ventricular groove

Reaches crux of the heart

  • In 60% subjects it anastomoses with circumflex branch of left coronary artery to the left side of the crux.

Branches

Branches from first segment of the artery :–

Right conus artery –

  • It is usually the first branch.
  • It supplies the infundibulum of right ventricle.
  • It anastomoses with left conus artery from circumflex artery, forming Annulus of Vieussens around the infundibulum.
Right anterior ventricular rami  –
  • These are 3 or 4 in number
  • They arise at right angles from the trunk of coronary artery.
  • They supply sternocostal wall of the right ventricle.
  • The longest ventricular ramus is right marginal artery, which runs along the inferior border of heart towards the apex.
Right anterior atrial rami –
  • These are arranged in anterior, lateral groups.
  • They supply myocardium of right atrium.
  • One of the atrial rami supplies SA node in 65% cases, known as sinu-atrial nodal artery.

Branches from second segment of the artery :–

Right posterior ventricular rami  –

  • They arise in the posterior part of atrio-ventricular groove.
  • They supply the diaphragmatic surface of right ventricle.
Right posterior atrial rami –
  • They supply posterior surface of both right & left atria.
Posterior interventricular branch  –
  • It arises near the crux of heart in 70% subjects.
  • It passes along the posterior interventricular groove.
  • Close to the apex of heart it anastomoses with anterior interventricular branch of left coronary artery.
  • It supplies-
  • Diaphragmatic surface of the right and left ventricles.
  • Postero-inferior 1/3rd of the ventricular septum through septal rami.
  • First septal ramus supplies atrio-ventricular node, in 80-90% subjects.

LEFT  CORONARY  ARTERY

Origin :-

It arises from the left posterior aortic sinus of ascending aorta.

Course :-

At first it appears behind the pulmonary trunk

Then passes forwards and to the left between the pulmonary trunk and left auricle

Then it divides into 2 branches – anterior interventricular & circumflex arteries.

Branches

The trunk of left coronary artery does not provide any significant branches.

ANTERIOR  INTERVENTRICULAR  ARTERY

Course :-

It descends in the anterior interventricular groove towards the apex

Winds round the incisura apicis cordis

Enters on to the inferior surface of heart and runs in the posterior interventricular groove

It ends by anastomosing with posterior interventricular artery at the junction of anterior 1/3rd and posterior 2/3rd of the groove.

Branches :-

Anterior ventricular rami  –

  • These are for both right and left ventricles.
  • One of the left ventricular rami is large known as diagonal artery, which arises from the junction of anterior interventricular and circumflex arteries.
  • One of the right ventricular rami forms the left conus artery, which supplies the infundibulum of right ventricle.
Septal rami –
  • They supply antero-superior 2/3rd of ventricular septum.

CIRCUMFLEX  ARTERY

Course :-

It passes along the left part of atrio-ventricular groove

Winds round the left border of heart

Occupies the posterior part of atrio-ventricular groove

Here it anastomoses with right coronary artery, on the left side of the crux.

Branches :-

Atrial & Ventricular rami –

  • They supply the adjoining surfaces of left atrium and left ventricle.
Kugel’s artery –
  • It is an atrial branch.
  • It communicates with similar branch of right coronary artery along the anterior atrial wall.
Sinu-atrial nodal artery –
  • It arises from circumflex artery in 35% subjects.
Left marginal artery –
  • It follows the left border of heart towards apex.
Posterior interventricular artery –
  • It is a continuation of circumflex artery in 10 – 20% individuals.
  • In those individuals AV node is supplied by septal rami of left coronary artery.


CORONARY  DISTRIBUTION

Right Coronary Artery

  • It supplies – right atrium, right ventricle except along the anterior interventricular groove, postero-inferior 1/3rd of ventricular septum, SA node & AV node.

Left Coronary Artery

  • It supplies – left atrium, left ventricle except along the posterior and inferior surfaces of the heart, antero-superior 2/3rd of the ventricular septum.


CORONARY  PREDOMINANCE

Right Coronary Predominance

  • In majority of people posterior interventricular artery is derived from the right coronary artery.

Left Coronary Predominance

  • In minority of people posterior interventricular artery extends as a continuation of the left coronary artery.
  • In these people left ventricle and ventricular septum are under the nutritional control of left coronary artery.
  • Obstruction of left coronary artery may produce output failure of systemic circulation.

Balanced Type

  • Posterior interventricular arteries are derived from both coronary arteries.
  • These individuals are least affected by coronary diseases.


VENOUS  DRAINAGE  OF  HEART

  • 60% of venous blood of the heart drains into right atrium via coronary sinus.
  • 40% of the blood drains into the different chambers of heart via venae cordis minimi & anterior cardiac veins.

CORONARY SINUS

  • It is a wide venous channel, situated in the posterior part of atrio-ventricular groove.

Course

It begins in the left part of atrio-ventricular groove

Here it receives great cardiac vein

Then it passes downwards and to the right along the posterior part of atrio-ventricular groove

Finally, it ends in the sinus venarum of right atrium between the opening of inferior vena cava and right atrio-ventricular orifice.

  • Opening of the sinus is situated in the lower part of atrial septum and guarded by a semilunar Eustachian valve.

Tributaries

Great cardiac vein

  • It begins from the apex of heart.
  • Passes upwards along the anterior interventricular groove.
  • It receives left marginal vein and joins the coronary sinus.

Middle cardiac vein

  • It passes from the apex along the posterior interventricular groove.
  • Terminates close to the right end of the sinus.

Small cardiac vein

  • It is situated in the right posterior atrio-ventricular groove.
  • It opens at the right end of the sinus.
  • It receives right marginal vein.

Posterior vein of left ventricle

  • It ends in the sinus on the left side of middle cardiac vein.

Oblique vein of left atrium

  • It joins close to the left end of the sinus.

 

APPLIED  ASPECTS

ISCHAEMIC HEART DISEASE (IHD)

  • It results from the occlusion of coronary artery or its major branches.

Angina pectoris –

  • Incomplete and spasmodic obstruction of coronary arteries leads to pain in the chest referred along the left upper arm.

Primary cause –

  • Formation of atheromatous plaque beneath the endothelial lining of the artery.
  • Ulcer develops in the plaque on which platelets are aggregated to form a thrombus.
  • It results in narrowing of the vessel.
  • Sudden and complete obstruction of a major branch leads to sudden death by myocardial infarction.
  • In gradual and complete occlusion, the person may survive with collateral anastomoses.

Locations of occlusion –

  • First 2 cm of left anterior descending branch of left coronary artery with 40% – 50% of frequency.
  • First 2 cm of circumflex branch of left coronary artery with 15% - 20% of frequency.
  • Proximal and distal third of right coronary artery.

Surgical approach –

Aortic-coronary by-pass operation- (Coronary Artery Bypass Grafting-CABG)

  • A vascular auto-graft taken from tributaries of great saphenous vein.
  • It is grafted between the peripheral patent portion of occluded coronary artery and the aorta.
Percutaneous Transluminal Angioplasty-
  • A balloon is introduced percutaneously to dilate the obstructed coronary artery.




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