A healthy heart contracts approximately 70 to 80 times per minute and 100.000 times a day. So, it pumps around 300 liters of blood to the whole body per hour. A normal heart contains four cavities. Upper two cavities are called right and left atria while the lower ones are referred to as right and left ventricles. The function of the heart is to pump oxygen-rich blood to the whole body. The blood passes through the four heart valves until it travels through the cardiac cavities and finally is pumped to the body. These are tricuspid, pulmonary, mitral and aortic valves. The blood, which is cleared and oxygenated in the lungs, passes through these four cavities and then is ejected from aortic valve to the “Aorta”, finally pumped to the whole body.
The heart valves are opened when the heart contracts as a pump, allowing the blood to pass. They close immediately between the heartbeats, preventing the blood from flowing back. A possible defect in this normal organization will prevent the heart from functioning effectively as a pump.
Tricuspid valve is located between the right atrium and the right ventricle.
Pulmonary Valve is localized between the right ventricle and the pulmonary artery.
Mitral valve is localized between the left atrium and the left ventricle.
Aortic valve is localized between the left ventricle and the aorta. It helps the heart to pump the blood to the organs.
Valve diseases associated with childhood rheumatic fever and wear in older ages, and congenital valve diseases mostly occur in mitral and aortic valves. Pulmonary and Tricuspid valves are infrequently involved.
Degenerative (related to wear) heart valve diseases mostly occur as Aortic Valve Stenosis and Mitral regurgitation. Incidence of Aortic Valve Stenosis increases over the age of 70. This increases with the increased average of age in healthy societies.
Aortic valve is calcified and deformed, resulting in further stenosis and incapability of opening. This means that the heart forces the blood through a highly narrowed valve when pumping. The myocardium is therefore exposed to a larger stress and load. This leads to thickening of myocardium in time and may result in weakening and dysfunctional in further stages. And this is called heart failure that causes impaired health and restriction of moves of an individual. Consistent valve stenosis and heart failure is a life-threatening state.
What Causes Aortic Stenosis?
Aortic stenosis is wear of aortic valve and calcification mostly associated with the age, which results in restricted moves of the valve. Previous rheumatic fever, radiotherapy, and high cholesterol promote the development of disease.
The patients may complain about chest pain, sensation of compression on the chest, feeling faint, syncope after a tiring work, loss of balance, fatigue, shortness of breath, and heart-throb.
It is not likely to repair calcified stenosis of aortic valve through a drug therapy. However, adjuvant drug therapies for heart failure and arrhythmia developed secondary to aortic vale disease, and the risk of clot formation can be considered.
Surgical procedures and catheters are used for treatment of aortic stenosis.
A large number of surgeries for heart valves (two third) is performed for aortic stenosis. Surgical treatment of aortic valve has been utilized for over 40 years. In this method, the calcified valve is replaced with metal or biological tissue valve by an open heart surgery. Biological tissue valves are mostly used for elderly patients. Anticoagulant drugs (warfarine) should be regularly used during follow-up period after valve operation. It is possible to use anticoagulant drugs for a certain period of time then cease when using tissue valves.
Under normal circumstances, this operation involves 1% of vital risk for patients in low-risk group and who are under 70 years old. It is performed under safe conditions. This rate is reported to be 4% when considering together elderly and all patients with previous surgeries.
Transcatheter aortic valve implantation (TAVI) has been developed for elderly patients with aortic stenosis associated with wear, and patients in high-risk group because of coexisting diseases and for who an open heart surgery is considered risky, and started to use widely in the world after 2005. The valve used in line with the developed technology, and the application of implant system become easier each year. It is currently applied on over 10.000 patients across the world.
There are two valves mostly used through catheter, Sapien XT (Edwards) and Corevalve (Medtronic). This valves are similar to bioprosthesis valves which are surgically implanted.
TAVI procedure is performed at catheter laboratory by teamwork of invasive cardiology, cardiovascular surgery, echocardiogram, and anesthesia staff.
Inguinal region is mostly accessed when the patient is under anesthesia. The heart is reached through aorta and calcified aortic valve is enlarged by a balloon then biological tissue prosthesis valve is implanted. The entire procedure is monitored by echocardiogram through esophagus so that precise measurements can be provided.
If it impossible to perform TAVI because of atherosclerosis and calcification of inguinal vessels and aorta, a small incision is made below the breast and bioprosthesis valve is implanted on the apex of the heart.
TAVI procedure is performed when surgical valve replacement operation is highly risky for elderly patients. Time of life is shortened in patients with advanced aortic stenosis who are elderly and in high risk group. It produces a life-threatening state of over 50% when they are left untreated. Although surgical replacement of valves does not reduce the risk sufficiently, PARTNER US and PARTNER EU studies show that this risk is reduced by approx 30% for Edwards valve through TAVI procedure. After CoreValve, significant European studies indicate an annual rate of life ranging between 72% and 82%.
There are risks, which may occur after TAVI procedure, also in this patient group as in surgical and other interventions. Important scientific studies report complications including stroke: 4.5%, severe problems with vascular access: 17%, and severe hemorrhage: 22%. The rate of complications, e.g. acute renal damage, infarction, re-intervention to the heart, and arrhythmia, is around 1-2%. The possibility of implanting a permanent pacemaker after the procedure varies between the valves and is reported to be 4% to 40% in different series.
Such complications are expected to reduce in the forthcoming years by means of innovations and developments in device and valve systems..
The start-point in preparation of the patient for this procedure is clinical evaluation. Complaints, examination findings, and laboratory tests are evaluated for compatibility with TAVI. The risk group of the patient is determined using EuroScore and STS (Society of Thoracic Surgeons) scores which are international risk determination scores. If the risk is determined to be over 20% for EuroScore and over 10% for STS, benefit-harm index is evaluated that TAVI procedure should be more beneficial.
Echocardiogram: Considered golden standard in examination of aortic valve. The diameter of valve, severity of calcification, measurements at origin of aorta, and evaluation of contraction capacity of heart are the most important steps.
Transesophageal Echocardiogram: It must be performed, if applicable, prior to TAVI to ensure most precise measurements. This procedure involves inserting a probe along esophagus as in the gastroscopy to evaluate heart valves and cavities. Thus, it is possible to evaluate at the nearest point to the heart. During TAVI procedure, the valve is constantly monitored by transesophageal echocardiogram.
Coronary Angiography and Catheterization: Coronary arteries must be checked by angiography before TAVI procedure. The measurements for aortic valve should be taken by catheterization. If coronary arteries are narrowed, they must be treated. If it is possible to insert a stent, stent should be inserted before TAVI procedure then valve should be inserted at the second session.
CT Angiography for Aorta and Leg Vessels: The diameter and calcification rate of aorta and leg vessels are mostly examined by angiography which is performed with computerized tomography. It is very useful to measure diameter of vessels for applicability of valve and implantation system.
The success achieved in this practice of aortic valve has increased the hope that this practice can be performed for other types of valves. Clips-type applications have been initiated for mitral valve around the world. There have been studies for types of mitral valve as well.