Coronaries

CoronariesDr. SUMIT GUPTA CTVS RESIDENT

Coronary Arteries

1 - From an anatomic point of view, the coronary artery system divides naturally into two distributions, left and right

2- Fromthe standpoint of the surgeon, the coronary artery system is divided into four parts: - the left main coronary artery, - the left anterior descending coronary artery and its branches, - the left circumflex coronary artery and its branches, - the right coronary artery and its branches

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1. Left Main Coronary Artery (LMCA)A. Left Anterior Descending (LAD)

• Septal Perforators• Diagonals (D1, D2, D3)• Ramus intermedius branch• Left posterior descending branch

B. Left Circumflex Artery (LCx)• Obtuse Marginal (OM1, OM2, OM3)• Left Posterolateral (First , Second & Third)

2. Right Coronary Artery (RCA)• Conus Artery (Infundibular Artery, Adipose Artery, 3rd Coronary Artery,

Arteria Of Vieussens)• Sinoatrial Node Artery• Right posterior descending (PDA) branch• Acute marginal segment• Posterior descending septals• Right Posterolateral (First , Second & Third)

The major coronary arteries form a circle and a loop around the heart

- The circle is formed by the right coronary and left circumflex arteries as they traverse the AV sulci.

- The loop between the ventricles and at rightangles to the circle is formed by the left anterior descending(interventricular) coronary artery and the posterior descending(interventricular) coronary artery as they encircle theseptum

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LEFT CORONARY ARTERY

Left Main Coronary Artery

• The LMCA arises from the superior portion of the left aortic sinus, just below the sinotubular ridge of the aorta, which defines the border separating the left sinus of Valsalva from the smooth (tubular) portion of the aorta.

• The LMCA ranges from 3 to 6 mm in diameter and usual length is 10 to 20 mm, with a range of 0 to 40 mm

• It normally courses between the pulmonary trunk and the left atrial appendage to reach the left AV groove

• The LMCA usually bifurcates into the LAD artery and LCx branches.

• Rarely 1%, the LMCA is absent, and there are separate ostia of the LAD and LCx arteries.Occasionally, additional vessels originate from the LMCA and course parallel to the diagonal branches of the LAD branch.Such an additional artery (formerly called a ramus intermedius) is termed the first diagonal branch of the left anterior descending artery.

Left Anterior Descending Artery (LAD)

• The LAD courses along the epicardial surface of the anterior interventricular groove toward the cardiac apex.

• The major branches of the LAD are the septal and diagonal branches. The septal branches arise from the LAD at approximately 90-degree angles and pass into the interventricular septum, varying in size, number, and distribution.

• One or more branches to the right ventricle connect with infundibular branches from the proximal right coronary artery. This important route for collateral flow is the loop of Vieussens.

• A variable number of diagonalarteries course obliquely between the anterior descending and left circumflex arteries and supply the left ventricular free wall anteriorly and laterally.

• Variations in the left anterior descending artery are infrequent, although in about 4% of hearts, it exists as two parallel vessels of about equal size. It may terminate before the apex or extend as far as the posterior AV groove

• During its course, the LAD is often covered by superficial muscle fibers, which run at right angles to the vessel, creating what is known as a “myocardial bridge.”

• On cine arteriograms, the bridged portion of the vessel can be visualized during systole, when the bridging fibers contract and distort the vessel lumen. Myocardial bridging has been associated with angina, myocardial infarction, and sudden death.

Left Circumflex Artery (LCx)• The LCx artery originates from the LMCA and courses within

the posterior (left) atrioventricular groove toward the inferior interventricular groove.

• The LCx usually gives off one to three large obtuse marginal (OM) branches as it passes down the atrioventricular groove. These are the principal branches of the LCx because they supply the lateral free wall of the left ventricle. Often their position can then be identified at operation by the altered color (reddish or light tan) of the overlying thin muscle layer compared with that ofthe remainder of the ventricular wall

• Beyond the origins of the obtuse marginal branches, the distal LCx tends to be small.

• The sinus node artery occasionally originatesfrom the first few millimeters of the left circumflex artery.

• Rarely, the circumflex artery terminates before the obtusemargin.

• A large branch originating from the proximal left circumflex artery and coursing around the left atrium near the AV groove is termed the atrial circumflex artery

Right Coronary Artery (RCA)• The RCA originates from the right anterior aortic sinus

somewhat inferior to the origin of the LCA. • It passes along the right atrioventricular groove toward the crux

(a point on the diaphragmatic surface of the heart where the anterior atrioventricular groove, the posterior atrioventricular groove, and the inferior interventricular groove coalesce).

• The first branch of the RCA is generally the Conus Artery, which arises at the right coronary ostium or within the first few millimeters of the RCA in about 50% of patients.

• In the remaining patients, the conus artery arises from a separate ostium in the right aortic sinus just above the right coronary ostium.

• The second branch of the RCA is usually the Sinoatrial Node Artery.

• It has been found that this vessel arises from the RCA in just under 60% of patients, from the LCx artery in just under 40%, and from both arteries with a dual blood supply in the remaining cases.

• The midportion of the RCA usually gives rise to one or several medium-sized Acute Marginal branches.

• These branches supply the anterior wall of the right ventricle and may provide collateral circulation in patients with LAD occlusion.

• The RCA terminates in a PDA and one or more right posterolateral branches.

Coronary Arterial Supply to Specialized Areasof the Heart

Blood supply to the ventricular septum

• The predominant blood supply to the ventricular septum is from the left anterior descending coronary artery via four to six large septal arteries 70 to 80 mm in length. In contrast, the septal arteries from the posterior descending coronary artery (except for the AV node artery) are rarely more than 15 mm in length (Fig. 1-30). They supply only a small zone of the ventricular septum near the posterior interventricular sulcus and in the region of the AV node.

• The septal arteriesfrom the posterior descending artery may, however, serve as an important source of collateral circulation. Until their final terminations, the septal arteries from both anterior and posterior descending arteries course along the right ventricular side of the septum, where pressure is lower than on the leftside.

• In the 10% of hearts with a left dominant circulation,the entire blood supply is from the left coronary artery

Blood supply to the SA Node• The sinus node artery is a single artery in 89% and double in 11%

of hearts.• Its origin is from the right coronary artery in 55% to 65% of cases

and from the left circumflex or left main coronary artery in the remainder.

• When it arises from the right coronary artery, it courses posteriorly and superiorly over the anterior wall of the right atrium beneath the right atrial appendage to the base of the superior vena cava

• The sinus node artery may penetrate the interatrial septum in its course to the superior vena cava. It then encircles the cava clockwise or counterclockwise, or bifurcates and encircles it in both directions.

• If the sinus node artery arises from the left circumflex artery, it courses over the left atrialwall, variably penetrates the interatrial septum, and ascends to the base of the superior vena cava, encircling that vessel as when it originates from the right coronary artery

Blood supply to the AV Node • The AV node artery arises from the characteristic U-turn of the right coronary

artery as it crosses the crux of the heart.• The AV node is usually supplied by the dominant coronary artery. • The AV node artery courses superiorly and anteriorly and terminates with a

distinctive angulation• An important accessory blood supply to the AV node is Kugel artery, which

originates from the proximal segment of either the right coronary artery or the left circumflex artery and courses through the interatrial septum to the crux of the heart to anastomose with the AV node artery

• In the atrial septum,Kugel artery anastomoses with branches of the sinus nodeartery.

• Kugel artery is the source of blood supply to the AV node in 40% of normal hearts.

• The bundle of His and proximal few millimeters of the• main bundle branches are supplied by the AV node

artery.• The remainder of the bundle branches and the

Purkinje arborization• within the septum are supplied by septal arteries• originating from the left anterior descending artery

• The anterolateral papillary muscle of the right ventricle, located near the junction of apical septum and free wall, is supplied by branches from the left anterior descending coronary artery

• The anterolateral papillary muscle of the left ventricle is supplied primarily by one or more branches from the left anterior descending coronary artery, but it may also be supplied by circumflex marginal branches

• The arterial supply of the posteromedial papillary muscle of the left ventricle is from terminal branches of the right or circumflex arteries, depending on the distribution of these arteries to the inferior surface of the left ventricle.

• LMA, left main coronary artery

• LAD, left anterior descending coronary artery

• D, diagonal branch of the left anterior descending coronary artery

• LCX, left circumflex coronary artery

• OM, obtuse marginal branch of the circumflex coronary artery

• PD, posterior descending coronary artery

• RCA, right coronary artery

• RM, right marginal branch

Left Coronary Artery Area of distribution : - 1- ventricles - - greater part of left ventricle expect the area adjoining the posterior interventricular groove - small part of right ventricle adjoining anterior interventricular groove 2- left artium 3- anterior part of interventricular septum 4- part of the left branch of the AV bundle

RCA Coronary Artery

• Area of distribution- 1- right atrium 2 - ventricles - greater part of RV expect the area adjoining the anterior interventricular groove - small part of LEFT ventricle adjoining posterior interventricular groove 3 - posterior part of interventricular septum 4 - whole of the conducting system except part of the left branch of the AV bundle

Dominance - A right dominant coronary circulation is one in which the posterior descending coronary artery is a terminal branch of the right coronary artery artery. • -The PDA courses in the inferior interventricular groove and gives

rise to a number of small inferior septal branches, which pass upward to supply the lower portion of the interventricular septum and interdigitate with superior septal branches passing down from the LAD artery.

• After giving rise to the PDA, the dominant RCA continues beyond the crux cordis (the junction of the atrioventricular and interventricular grooves) as the right posterior atrioventricular branch along the distal portion of the posterior (left) atrioventricular groove, terminating in one or several posterolateral branches that supply the diaphragmatic surface of the left ventricle.

A left dominant circulation, which occurs in about 10% to 15% of hearts, is one in which the posterior descending coronary artery is a branch, usually the last one, of the left circumflex coronary artery.

- The remaining patients have an RCA that gives rise to the PDA, with the LCx artery providing all the posterolateral branches (balanced or codominant circulation).-Left dominance occurs more frequently in males than in females

This distinction as to whether the right or left coronary artery supplies the posterior descending artery is important in evaluating patients with coronary artery disease and in planning coronary artery bypass grafting

Super dominanance

• A vessel is considered super-dominant when it is extremely large and supplies the territory that is normally supplied by the other vessel.

• RCA• LCX• LAD

Coronary Veins

• The coronary venous circulation is comprised of Coronary sinus anterior Cardiac veins, and venae cordis minimi

• The coronary venous sinus isthe largest vein ofthe heart.it is about 3cm long

• it is situated in the left posterior coronary sulcus .• it ends by opening into the posterior wall ofthe right atrium, to

the left of the opening of the inferior vena cava.

The ostium of the coronary sinus is guarded by a crescent-shaped valvular remnant, the Thebesian valve. Rarely, the coronary sinus drains directly into the left atrium.

• The Great Cardiac Vein (of Galen) arises near the apex in the interventricular sulcus. It ascends to the atrioventricular sulcus, where it turns to the left in company with the left coronary circumflex artery. At the obtuse margin, the great cardiac vein joins the oblique vein of the left atrium (this is where the coronary venous sinus has its embryologic beginning).

• The Oblique Vein (of Marshall) of the left atrium drains the posterior wall of the left atrium. It is the vestigial remnant of the left common cardinal vein or duct of cuvier.

• Its junction with the great cardiac vein marks the beginning of the coronary venous sinus.

• If the embryonic left common cardinal vein is retained, bilateral superior venae cavae will be present, with great enlargement of the coronary sinus occurring with the formation of the left superior vena cava.

• The posterior vein or Marginal Vein of the left ventricle run on the the diaphragmatic surface of the left ventricle. It ends in themiddle of coronary sinus.

• The Middle Cardiac Vein passes upward in the posterior interventricular sulcus, superficial to the interventricular artery. It receives tributaries from both ventricles and the interventricular septum. It ends in the coronary sinus, near its termination.

• The Small Cardiac Vein arises on the acute margin of the right ventricle. It passes in the right coronary sulcus to join the extreme right end of the coronary venous sinus.

• The Anterior Cardiac Veins, three or four variably sized veins, arise from the sternocostal surface of the right ventricle. They cross superficial to the right coronary artery and pierce the margin of the right auricle to drain directly into it. Some anterior cardiac veins join the small cardiac vein.

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• venous cordis minimi / thebesian veins / smallest cardiac veins -

1. numerous in number 2. present in all four chambers of the heart which open directly into the cavity 3. more on right side of the heart than left

• During cardiac operations, cardioplegic solution can be administered retrogradely into the coronary sinus.

• In patients with the Wolff-Parkinson-White preexcitation syndrome and left-sided bypass tracts, the ablation catheter during electrophysiologic studies can be positioned within the coronary sinus and great cardiac vein adjacent to the mitral valve ring to localize the aberrant conduction pathway.

• The coronary veins, via the coronary sinus, provide access to percutaneous epicardial mapping and pacing of the ventricles and ablation of subepicardial arrhythmogenic.

• For biventricular pacing, optimal left ventricular pacing lead position is within the posterolateral branch of the coronary sinus, followed by the lateral branch.

Coronary Lymphatics

• The lymphatic flow passes from the lymphatic capillaries to the epicardial vessels which follow the coronary arteries.

• At the right and left collecting trunks, the lymphatic flow diverges.

From the right collecting trunk, it passes to the mediastinal nodes.

From the left collecting trunk, it passes to the caval node of the tracheobronchial group, which is located between the aorta and the superior vena cava.

Angiographic Veiws

Standard Angiographic Views An easy way to identify the tomographic views is to use the anatomic

landmarks - catheter in the descending aorta, spine and the diaphragm. The rough rules are: RAO vs. LAO- If the spine and the catheter are to the right of

the image, it is LAO and vice versa. If central, it is likely a PA view

Cranial vs. caudal - If diaphragm shadow can be seen on the image, it is likely cranial view, if not, it is caudal

Catheter and spine to the LEFT

RAO view

No diaphragm shadow

Caudal view

Catheter at the CENTER

PA view

No diaphragm shadow

Caudal view

Spine to the

RIGHTLAO view

Diaphragm shadow

Cranial view

Standard Angiographic Views

RAO-Caudal view: 100 to 200 RAO and 150 to 200 caudal Best for visualizing- Left main bifurcation Proximal LAD Proximal to mid LCx

Left Coronary Artery

Standard Angiographic ViewsLeft Coronary Artery

RAO 20 Caudal 20LMLAD

Diagonal

SeptalsDistal LAD

LCx

Best for visualization of LM bifurcation and

proximal LAD and LCx

LAO-Cranial view: 300 to 600 LAO and 150 to 300 cranialBest for visualizing mid and distal LAD Distal LCx in a left dominant system Separates out the septals from the diagonals

Left Coronary Artery

Standard Angiographic ViewsLeft Coronary Artery

LAO 50 Cranial 30

LM

LAD

DiagonalSeptals

Distal LAD

LCx

LCx

Best for visualization of proximal and mid LAD and splaying of the septals

from the diagonals. Also ideal for visualization of distal LCx

Left Coronary Artery

PA-Cranial view: 00 lateral and 300 cranial Best for visualizing - Mid LAD Distal LAD

Left Coronary Artery

PA projection: 00 lateral and 00 cranio-caudal

Best for visualizing Ostium of the left main

Left lateral view:

Best for visualizing

Proximal LCx,

Proximal and distal LAD

Also good for visualizing LIMA to LAD anastomotic site

Left Coronary Artery

Standard Angiographic Views

LAO 30: 300 LAO Best for visualizing ostial and proximal RCA

RAO 30: 300 RAO Best for visualizing mid RCA and PDA

PA Cranial: PA and 300 cranial Best for visualizing distal RCA bifurcation and the PDA Left lateral view: Left Lateral 900

Ostium of the RCA

Midportion of the RCA

Separation of RCA with its RV branches

Right Coronary Artery

Standard Angiographic ViewsRight Coronary Artery

LAO 30

Proximal RCA

PDADist

al RCA

Mid RCA

RAO 30

Mid RCA

PDA/PLV

PA 0 Cranial 30

Proximal RCA

PDA

Distal RCA

Mid RCA

Best for visualization of ostial and proximal RCA

Best for visualization of mid RCA and PDA

Best for visualization of distal RCA and its bifurcation

Angiographic Assessment of Coronary Artery Narrowings• An angiographic lumen narrowing is commonly referred

to as a stenosis, which may be caused by atherosclerosis, vasospasm, or angiographic artifact.

• The evaluation of a stenosis relates the percentage reduction in the diameter of the narrowed vessel site to the adjacent unobstructed vessel.

• The diameter stenosis is calculated in the projection where the greatest narrowing is seen.

• An exact evaluation of dimensions is impossible and, in fact, the severity of stenotic lesions are roughly classified.

It should be noted that the stenotic lumen is compared to a nearby unobstructed lumen, which indeed may have diffuse atherosclerotic disease and thus is angiographically normal but may still be diseased. This fact explains why postmortem examinations report much more plaque than is seen on angiography.

CAD is defined as a more than 50% diameter stenosis in one or more of these vessels, although it is clear that stenoses of less than 50% have major prognostic implications because these lesions most commonly lead to plaque rupture and acute myocardial infarction.

Subcritical stenoses of less than 50% are best characterized as non-obstructive CAD

Obstructive CAD is classified as one-, two-, or three-vessel disease.

Angiographically Estimated Coronary Blood Flow (TIMI Flow)

Myocardial blood flow has been assessed angiographically using the thrombolysis in myocardial infarction (TIMI) score for qualitative grading of coronary flow. TIMI flow grades 0 to 3 have become a standard description of angiographic coronary blood flow in clinical trials.

In acute myocardial infarction trials, TIMI grade 3 flows have been associated with improved clinical outcomes.

The four grades of flow are described as follows:1. Flow equal to that in noninfarct arteries (TIMI-3) 2. Distal flow in the artery less than non infarct arteries (TIMI-2)3. Filling beyond the culprit lesion but no antegrade flow (TIMI-1)4. No flow beyond the total occlusion (TIMI-0)

References

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