Patients diagnosed with heart failure at our clinic who routinely undergo CRT implantation will be included in the study. This decision is independent of the study. In patients included in the study, after routine placement of a coronary sinus catheter, 2 cc of blood will be drawn from this catheter without performing any additional invasive procedures on the patient. Additionally, one peripheral blood sample will be collected from the patient's routinely accessed antebrachial vein. The blood samples will be centrifuged at 4000 rpm (revolutions per minute) for 10 minutes to separate the serum and stored at -80 °C until analyzed. The demographic, clinical, laboratory, electrocardiographic, and echocardiographic data of these patients will be recorded. At the 6-month follow-up clinic visit after discharge, routine heart failure parameters, routine echocardiographic data, and routine ECG recordings will be obtained. The procedures to be performed after discharge are routine for patients who have undergone CRT implantation at our clinic, and no additional follow-up or tests will be performed for this study. After all data are recorded, statistical evaluation will be performed. Data will be reviewed through the ENLİL HBYS system. The best criteria for determining CRT response have not been clearly established. Many studies have been conducted to predict CRT response in advance. A review of the literature shows that YKL-40 levels in the blood are associated with cardiovascular diseases, but no study in the literature has shown the relationship between YKL-40 levels and CRT implantation in patients.

Patients diagnosed with heart failure who are under follow-up and have an EF <35 despite optimal medical treatment, and whose functional capacity is 2-3, or patients diagnosed with heart failure who routinely undergo CRT implantation at our clinic due to high-degree block will be included in the study. This decision was made independently of the study. Patients routinely undergo permanent pacemaker implantation with leads placed in the right ventricle, coronary sinus, and right atrium. In patients included in the study, after routine placement of the coronary sinus catheter, 2 cc of blood will be drawn from this catheter without performing any additional invasive procedures on the patient. In addition, one peripheral blood sample will be drawn from the patient's routinely opened antebrachial vein. The blood samples will be centrifuged at 4000 rpm (revolutions per minute) for 10 minutes to separate the serum and stored at -80 °C until analyzed. The demographic, clinical, laboratory, electrocardiographic, and echocardiographic data of these patients will be recorded. At the 6-month follow-up clinic visit after discharge, routine heart failure parameters, routine echocardiographic data, and routine ECG recordings will be obtained. The procedures to be performed after discharge are routine for patients who have undergone CRT implantation at our clinic, and no additional follow-up or tests will be performed for this study. After all data are recorded, statistical evaluation will be performed. Data will be reviewed via the ENLİL HBYS system. In the literature, patients with KRT are grouped as RESPONDERS and NON-RESPONDERS. Although the best criteria for determining KRT response have not been clearly established, three categories can be considered in the evaluation. The first is clinical measurements (New York Heart Association classification, functional capacity, etc.), the second is the assessment of left ventricular reverse remodeling (increase in ejection fraction on echocardiography, decrease in left ventricular end-systolic and end-diastolic volume), and the third is the reduction in heart failure-related hospitalization and all-cause mortality during follow-up. In addition, individual factors may also influence the outcome. These factors include genetic and gender differences, left ventricular lead position, left ventricular scarring in ischemic patients, and atrial fibrillation. Patients who are NON RESPONDERS are less likely to benefit from CRT, which is an undesirable outcome for invasive treatment. Patients with pacemakers are at risk for foreign body infection and infective endocarditis, and the presence of a device that does not enhance cardiac function is undesirable. Many studies have been conducted to predict the response to CRT. Reviewing the literature, it has been shown that YKL-40 levels in the blood are associated with cardiovascular diseases; however, no study in the literature has shown the relationship between YKL-40 levels and cardiac resynchronization therapy implantation in patients.

Inclusion Criteria:

• Patients diagnosed with heart failure, with an EF ≤35, who remain in heart failure stages 2-3-4 despite optimal medical therapy, and who have LBBB and a QRS duration of at least 130 msec.
• Those who agreed to participate in the study
• Patients diagnosed with heart failure and who have been monitored, and for whom a permanent pacemaker has been decided due to the presence of a high-degree heart block

Exclusion Criteria:

• Patients under the age of 18
• Patients not receiving optimal medical treatment
• Those who declined to participate in the study
• Malignancy patients with an expected survival period of less than 1 year
• Patients with chronic inflammatory and rheumatological diseases

Patients with heart failure who have been decided to undergo CRT treatment at Trakya University Cardiology Clinic