Coronary anatomy: Difference between revisions

It has become such a common tool in diagnosing coronary artery disease, that it is hard to understand it’s relatively short history. Radner was the first researcher in 1945 to visualize the coronary arteries in humans, through a transsternal puncture <cite>Radner</cite>. In 1958 Sones at the Cleveland Clinic succeeded in injecting small amounts of contrast material directly in the coronary arteries<cite>Sones</cite>. In the late sixties Judkins developed the percutaneous transfemoral approach and used pre-bent catheters to cannulate the coronary ostia. In the seventies Charles Dotter and Andreas Gruntzig extended the catheterization to therapeutic uses. In the nineties, vascular acces via the radial artery became a realistic alternative.

Cardiac catheterizations were performed 3 million times a year worldwide in 2010. In the Netherlands around 65.000 catheterizations are performed annually.

Patients with older age, diabetes mellitus, chronic renal insufficiency, multivessel disease, low ejection fraction have a higher risk of complications.

Before Judkins developed the percutaneous transfemoral approach in the late sixties, brachial arteriotomy was performed to introduce the catheter. This is seldomly used nowadays. In the majority of cases arterial catheters are introduced via the femoral artery or radial artery using the Seldinger technique.

The femoral artery is located just below the inguinal ligament. For the femoral artery access, the femoral head provides the best visible landmark. Arterial puncture at this site remains below the inguinal ligament, is generally above the bifurcation of the superfical femoral and deep femoral arteries, and allows for hemostasis. In obese patients the inguinal skin crease is generally too low.

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The catheter is inserted through the preferably the right radial artery which is punctured 1-2 cm proximal to the styloid process after subcutaneous local anesthesia. To prevent arterial spasm a spasmolytic coctail with nitroglycerin (200mcg) and verapamil (5mg) can be administered intravenously<cite>Jukema3</cite>. Repeated arterial trauma increases the risk for spasm. Arterial puncture can be performed with either a single anterior wall puncture or a double wall through-and-through puncture. A small calibre guidewire is inserted through the plastic cannula to facilitate sheath placement. Introducing sheaths are generally 5-French or 6-French, are hydrophilic and have a tapered tip. Catheter advancement is typically performed with a standard 0.035” J-tipped wire, gently advanced until resistance is met. Common causes of resistance are congenital anatomic variations such as the radial artery loop, tortuosity in the axillary, subclavian or inominate artery, and arterial spasm<cite>Caputo</cite>.  

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Complications from arterial access include arterial dissection, AV fistula formation, retroperitoneal hemorrhage and pseudoaneurysma formation. The femoral artery has traditionally been the artery of choice for procedures, but has serious limitations in patients with peripheral vascular disease or using anticoagulation. The radial artery has replaced the femoral artery approach as primary choice in most institutions in Europe. Main advantages are the less severe access site bleedings due to good hemostasis technique by p.e. the TR band, possible earlier mobilization of the patient and lower incidence of local bleeding complications. Disadvantages are the possibility of serious arterial spasm and the risk of radial artery occlusion.  

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A randomized trial published in 2008 shower that transradial coronary angiography was safe, feasible and effective with similar results to those of the transfemoral approach. The Access trial performed by Kiemeneij et al showed similar procedural and clinical outcomes of PCI in transradial, transbrachial and transfemoral PCI. Major access site complications were lower in the transradial group, but with higher access failure (coronary cannulation)<cite>Kiemeneij</cite>. Procedural duration and radiation exposure are higher using transradial access, but with significantly lower rate of major vascular complications<cite>Brueck</cite>. In STEMI patients, the HORIZONS-AMI trial showed that the transradial approach was associated with reduced major bleeding and improved event-free survival<cite>Genereux</cite>.

[[File:Coronary_anatomy1.png]]<cite>Fauci</cite>

The left main coronary artery (LMCA) originated in the left sinus of Valsalva. Its length varies from 5-10mm. Sporadically the LMCA is absent, resulting in separated ostia of RCx and LAD. Sometimes there is a trifurcation, with a branch between the RCx and LAD called intermediate artery. Usually the LAD runs in the anterior interventricular groove. The most important side branches are the septal branches and diagonal branches to the left ventricular wall. The RCx runs in the left atrioventricular groove. All branches to the left ventricular wall are classified as obtuse marginal or posterolateral branches. In 40% the sinus node artery arises from the proximal portion of the RCx.

[[File:NomenclatureOfSegments.png]]

Recommended projections for the RCA are:

Spider view

[[File:BloodSupplyCardiacConductionSystem.png]]

Collateral connections between coronary arteries are present in every individual<cite>Jukema5</cite>. Because of the higher perfusion pressures in major arteries, there is normally no flow in collateral connections. In case of a coronary obstruction of more than 70% diameter reduction, blood starts to flow to the artery distal of the obstruction. These pre-existent collaterals are called recruitable collaterals. Collaterals can also be newly formed and can be intra- or intercoronary. Cardiac ischemia stimulates formation of new collaterals and growth of recruitable collaterals. Recruitable vessels have a corkscrew aspect. Filling can be retrograde or antegrade (as by bridge collaterals: intracoronary collaterals). Coronary steal means that the flow through the epicardial coronary artery is diminished by the flow to collaterals that it is causing cardiac ischemia.  

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#Radner pmid=19023714