Aortocoronary bypass is a cardiac surgery procedure used to bypass coronary artery blockage. Arterial or venous autografts are used to take blood above and bring it under the coronary artery stenosis. This way heart will receive enough blood and oxygen for a normal function. Therefore, aortocoronary bypass will provide normal life for patients with chest angina, prevent myocardial infarction and preserve heart function.
Vessels used for coronary bypass grafting are either peripheral veins or arteries. Great saphenous vein is the most common used vein graft. Because of its wall and endothelial properties veins are inferior grafts when compared to arterial ones in terms of graft patency and durability. Durability of venous coronary graft is about ten years. On contrary, arterial coronary grafts has excellent long-term durability and better clinical outcomes. Therefore the use of left mammary artery on the left anterior descendent branch of left coronary artery is a mandatory procedure. Patient will benefit from multiple arterial coronary revascularization as well, so total arterial revascularization is of highest importance particularly in younger patients. Alternative arterial grafts are right mammary artery, radial artery, gastroepiploic artery and inferior epigastric artery.
Left internal mammary artery - LIMA was grafted side-toside on the first diagonal branch of left coronary artery and to mid LAD.
Aortocoronary bypass surgery is usually performed on a steady or arrested heart. During the procedure the heart will be protected from ischemia by potassium reach solution we call cardioplegia. In some cases coronary bypass could be done on a beating heart.
Coronary patients should be aware of the fact that bypass surgery will relieve symptoms but will not stop the disease progression. Therefore prevention and risk factor control is of the highest importance in order to provide long-term graft patency and atherosclerosis control.
Aortic valve is a tri-leaflet fibrotic tissue structure located between the left ventricle and the aorta. During the left ventricle contraction – systole, aortic valve opens while closes during left ventricle relaxation - diastole. When closed, aortic valve stops blood return to the heart and that way provides one-way blood flow through the aorta.
Aortic stenosis is the most common disease of the aortic valve. In some patients durring the time leaflets gets thick, less mobile and blocked with calcium deposits, and so obstructs blood ejection from the heart. Patients generaly support well significant aortic stenosis durring the years. Meanwhile heart is suffering, and symptom onset indicates important heart dysfunction. From this point on, the disease prognosis without the surgery is similar to malignant disease. Main syptoms are syncopes, chest angina and heart failure as the most severe one. Aortic regurgitation or insuficiency is a condition when aortic valve closes uncompletely and allows retrograde blood flow into the heart. Such a volume overload dilates left ventricle. Aortic regurgitation is much better tolerated then stenosis.
Aortic stenosis and insuficiency are clearly mechanical problem and only surgery could remove obstruction or make valve competent. Generaly aortic valve is replaced either by mechanical or bioprosthesis. Procedure could be done through the full lenght mid-sternotomy, upper „J“ sternotomy or through the small right side intercostal chest incision.
Mitral valve is a complex structure located between left atrium and left ventricle. Mitral valve prevents retrograde blood flow to the left atrium during systole. The most frequent mitral valve pathology today is mitral regurgitation or innsuficiency (MR). Degenerative etiology followed by ischemic heart disease are main causes or MR. Rheumatic mitral valve is today, due to widespread antibiotic use the third most common cause of mitral valve disease, and generally results in mitral stenosis.
Mitral valve can be repaired in many patients, so they are directed to surgery in early stages of disease. The most important condition for an early reconstructive approach is to have a surgical team to guarantee high probability of repair. Best results are achieved in degenerative disease, where 95 to 98% of valves could be repaired, with excellent long-term durability. see more …..
Aorta is the largest arterial blood vessel. It takes blood from the heart to limb, head and visceral arteries. Cardiac surgery takes care of its chest portion called thoracic aorta that is made of ascending, arch and descending aorta. Ascending aorta begins with aortic valve, while branches for head and arms arise from aortic loop called aortic arch at upper chest level. Descending aorta goes down to the diaphragm after the arch, where abdominal aorta begins.
Aortic aneurism is a bulging of aortic wall that is filled with blood, grows over time, and eventually ruptures. Connective tissue disorders, degeneration, atherosclerosis, infection and hypertension can provoke aneurism formation. Aneurism is most frequently found in ascending aorta because of weak outer support and major pressure stress exposure during systole. Aneurism diameter of 50 to 55 mm has to be operated in order to prevent rupture.
Aortic dissection is a serious and urgent medical condition in which rupture of inner aortic layer allows blood to enter the aortic wall and to dissect it between layers. Most of ascending aorta dissections is going to rupture within first 24h, and if not treated only 10 % of patients will survive first two weeks. Therefore, ascending aorta dissection is an urgent surgical condition that has to be operated immediately. De Bakery tips I and II (Stanword type A) mean that entire thoracic or just ascending aorta respectively dissected. De Bakey tip III (Stanford B) dissection two means that only descending thoracic aorta disected.
If aortic valve is competent, aneurism or dissected aorta has to be replaced with tubular Dacron graft. If aortic valve is insufficient, it should be treated either by replacement or repair. Bentall procedure refers to ascending aorta and aortic valve replacement with composite graft along with coronary artery reinplantation. Composite grafts are made of tubular graft attached to aortic valve prosthesis.
Valve sparing procedures (David, Jacoub) preserve native aortic valve, while ascending aorta replacement and coronary reinplantation are done in the same way as in Bentall procedure.
Blood is delivered to the myocardium through the left and right coronary artery. Left coronary artery gives two branches, left anterior descedent (LAD) and marginal branch. Right coronary artery vascularise posterior part of ventricular septum in almost 90% of patients, and only if case its desease is of clinical importance.
Stenosis of left coronary main stem so called „left main“ stenosis or proximal stenosis of LAD requires revascularisation as soon as possible because of large miocardial volume endangered with such a stenosis.
Valve prosthesis could be mechanical or bioprosthesis. Mechanical prosthesis consists of two leaflets that are opening through the heart cycle. Leaflets and valve body are made of special hypotrombogenic material called pyrolitic-carbon.Although hypotrombogenic, mechanical valves requires life time anticoalgulation therapy.bioprosthesis
Bioprosthesis are made either of bovine pericardium, or porcine valves. Bioprosthesis are atrombogenic and do not requre anticoalgulation therapy. Unfortunately they are of limitted durability and has to be replaced 15 years after implantation (3rd valve generation). Generaly patient under 65 years should receive mechanical while in older one bioprosthesis is better solution.
Transcatheter Aortic Valve implantation – TAVI is an invasive procedure in which aortic valve is replaced via a catheter, using femoral, trans apical, subclavian or direct aortic minimally invasive access. Generally it means that catether mounted biological valve is delivered at aortic position. Stenotic valve has to be dilated by balloon before valve implantation. Because of high morbidity and mortality, TAVI procedure is indicated in high-risk patients, and in such a group outcomes are very similar to the surgery.