1. INTRODUCTION
Mitral regurgitation (MR) is the second most common disease in heart valve surgery and affects approximately 2% of the population.1,2 Ischemic mitral regurgitation (IMR) ranks third among the causes of mitral valve surgery and constitutes approximately 10% of mitral valve operation indications.3 When we look at the causes of MR, it is important to distinguish between primary and secondary disease groups, especially according to the development of the disease. In primary MR, one or more components of the valve apparatus may be affected as a result of mitral valve degeneration, including rheumatic heart disease, fibroelastic insufficiency, or Barlow’s disease. Endocarditis is one of the main causes of primary MR, which is especially discussed in the guidelines of the European Society of Cardiology and the European Society of Cardiac and Thoracic Surgery. In secondary MR, the valve apparatus is anatomically intact, and MR disease may develop due to insufficiency, particularly valve closure and valve attachment points. Secondary to MR, ischemic cardiomyopathy due to left ventricular dilatation and dysfunction is observed.1,4
IMR develops as a complication of coronary artery disease.5 IMD is a ventricular disease, not a valvular disease, and it begins to be seen with regional and all-encompassing left ventricular remodeling after AMI.6,7 Today, morbidity and mortality due to ischemic heart disease (IHD) and its complications are quite high. A significant number of these patients (40%) die due to AMI and its complications.8
Ischemic mitral regurgitation is one of the most controversial problems in cardiac surgery practice. In recent years, surgical revascularization and mitral repair attempts have been performed in moderate and severe ischemic mitral regurgitation. Mitral valve repairs in the heart working with retrograde normothermic perfusion can be counted among these interventions. These approaches not only reduce operative mortality, but also affect long-term survival.9,10
Papillary muscle dysfunction is prominent in the acutely developing group of these cases, which can also be classified as acute and chronic ischemic mitral regurgitation. Papillary muscle rupture is rarely encountered and its incidence in total acute myocardial infarctions is less than 1%. Rupture can involve the entire muscle, or it can be seen only in one head of the muscle. Rupture of the entire muscle is extremely dangerous and causes severe mitral regurgitation as the movement of half of both leaflets will be impaired. The ruptured papillary muscle should be sutured to the adjacent ventricular free wall. If there is damage only to the tip of the papillary muscle, not the whole, the insufficiency will be less. The ruptured papillary muscle head is repaired by suturing it to the papillary muscle right next to it.
Chronic ischemic mitral regurgitation, on the other hand, develops as a result of papillary muscle elongation secondary to infarction or due to excessive changes in ventricular anatomy that move the papillary muscles away from the mitral annulus. Clinically, leaflet prolapse due to chordae rupture or papillary muscle elongation is seen in some patients. More commonly, restricted mitral leaflet movement caused by left ventricular anatomical changes is observed. Valve repair in ischemic mitral regurgitation depends on the presence of restricted leaflet movement or excessive leaflet movement. In ventricular dilatations that develop as a result of ischemic heart disease, cases of mitral insufficiency are frequently encountered even without papillary muscle damage. In such cases, the papillary muscles displace laterally, causing restricted movement of the leaflets. Pathological examinations show that there is no annular dilatation in these patients and there is no correlation between annulus diameter and regurgitation.11
On the other hand, even annuloplasty alone reduces the diameter of the annulus and eliminates the failure by providing leaflet closure. Cases with restricted leaflet movement are only repaired by annuloplasty. In cases where prolapse develops, other surgical repair interventions such as papillary shortening, chordae shortening, leaflet resection are needed in addition to annuloplasty. Cases with restricted leaflet movement seem to have a shorter life expectancy than those with prolapse. In ischemic mitral regurgitation, papillary muscle dysfunction and ventricular deformation cause some problems in mitral valve repairs. As is known, ischemic mitral insufficiency occurs as a result of changes in ventricular anatomy. Since this condition develops after acute myocardial infarction, there is a decrease in left ventricular function. Patients with this condition adversely affect the outcome of cardiac surgery procedures.12 Therefore, since the results of long-term medical treatment in patients with mitral regurgitation are not at the desired level, some surgeons suggest that valve replacement surgery should be performed to prevent reoperation, assuming that mitral regurgitation may progress.13,14
Prolidase is a cytosolic exopeptidase that cleaves proline or hydroxyproline at the carboxyl terminal position of dipeptides. It is found in various organs such as the brain, heart, uterus and thymus, and in plasma.15 They have important roles in physiological and pathological processes such as embryonic development, wound healing, inflammation, carcinogenesis, angiogenesis, cell migration and cell differentiation.16,17 Proline is commonly found in the central nervous system.18 It has been reported that proline plays a role as a neuromodulator in synaptic transmission.19 Serum prolidase (U / L) levels have been evaluated in many diseases and have been found to be high in fibrotic liver disease, metabolic syndrome, hypertension, coronary artery disease (CAD) and valve disease.20,21
In this study, we evaluated the prolidase level in patients with and without ischemic mitral insufficiency. In conclusion, wide tissue distribution suggests that changes in prolidase enzyme activity may gain importance in the development and outcome of many diseases.