Pilot interventional randomized clinical trial to study the efficacy of left bundle branch pacing in patients with hypertrophic cardiomyopathy after myectomy for the prevention of progression of heart failure, prevent the occurrence of life-threatening rhythm disturbances and promote reverse remodeling of the LV.

The aim of the study is to evaluate the comparative efficacy and safety of implantation of a cardioverter-defibrillator with left bundle branch block pacing and a dual-chamber cardioverter-defibrillator in patients with HCM and complete left bundle branch block after myectomy at high risk of SCD.

Objectives of the study:

1. To analyze the safety of ICD implantation procedures with LBBB pacing in patients with HCM and LBBB after myectomy at high risk of SCD;
2. To develop a technique for LBBB lead implantation in patients with HCM and LBBB after myectomy;
3. To conduct a comparative analysis of QRS complex duration data based on ECG data before and after surgery, LV activation time, and pacing threshold based on postoperative programming data;
4. To conduct a comparative analysis of the functional class of CHF, NT-proBNP, the presence/absence of interventricular and intraventricular dyssynchrony, the degree of diastolic dysfunction, LVEF, and LV EDV based on echocardiography data before and 12 months after surgery;
5. Conduct a comparative analysis of QRS complex duration data based on ECG data, LV activation time, pacing threshold, the presence of recorded episodes of AF, VT, VF, antitachycardia and shock therapy according to programming data at 3, 6, and 12 months after surgery;
6. Assess quality of life before and 12 months after surgery using the KCCQ-12 questionnaire; 30 patients (15 patients in each group) will be randomly separated into 2 groups. All participants go through ICD programming at 3, 6, and 12 months after myectomy, assessment of left ventricular remodeling based on ECG and echocardiography, NT-proBNP, assessment of quality of life before surgery and 12 months after surgery.

After a discussion about the possibility of participating in the study, the patient is presented with an informed consent form and all questions of interest are explained. If consent to participate in the study is obtained, the patient and the researcher fill in all the required fields of two copies of the informed consent form and sign it. If necessary, the researcher re-explains any information regarding the study. Once informed consent has been obtained, an Individual Registration Card (IRC) is completed for the patient enrolled in the study. Completion of the IRC also continues until the completion of all stages of the study.

30 patients (15 patients in each group) will be randomly separated into 2 groups: dual-chamber ICD and a dual-chamber ICD with LBB pacing.

Initial data:

• Demographic indicators: age, gender, height, weight, body mass index;
• Disease severity: SCD risk, CHF functional class, NT-proBNP, presence/absence of interventricular and intraventricular dyssynchrony, degree of diastolic dysfunction, LVEF, LVEDV;
• Comorbidities: myocardial infarction, hypertension, diabetes mellitus, atrial fibrillation, ventricular tachycardia, chronic kidney disease, liver failure, stroke.
• The quality of life questionnaire Kansas City Cardiomyopathy Questionnaire (KCCQ-12)

Intraoperative:

• QRS complex duration according to ECG;
• LV activation time;
• Pacing threshold.

Hospitalization period:

1. Complications related to the ICD implantation procedure;
2. Adequate ICD function according to ECG and programming data.

ICD Implantation with Left Bundle Branch Pacing: Incision in the left or right connector area parallel to the key. Vein puncture. Electrodes are passed through the introducer system. Before implantation, a safety electrode is implanted in the LBBB at the apex of the right ventricle.

The His bundle is recorded 1-1.5 cm apically (toward the apex of the right ventricle) in the area of the interventricular septum. Pacing from this area of the QRS complex in lead V1 has a "W" morphology. Insert the electrode into the thick interventricular septum. After each ventricular extrasystole, stop inserting and measure the following parameters:

1. Unipolar impedance. The deeper into the septum, the lower the impedance. The target impedance is at least 500 ohms.
2. Change the activation pattern from LBBB to RBBB.
3. Initially, an increase, then a decrease in the unipolar signal. Fix the electrode with invisible U-shaped sutures. Control programming. Layered wound closure.

Statistical analysis:

Comparisons of continuous outcomes will be performed using the Mann-Whitney test for non-normal variables and the Welch t-test for normal variables. Comparisons of binary outcomes will be performed using the chi-square test or Fisher's exact test.

Inclusion criteria:

• Men and women aged 18 years and older;
• Patients with post-myectomy HCM who develop LBBB with a QRS complex greater than 130 ms and a high risk of SCD (HCM Risk-SCD ≥ 6%);
• Signed informed consent to participate in the study;

Exclusion criteria:

• Absence of QRS complex morphology consistent with LBBB in LBBB with a positive QRS complex less than 130 ms;
• Presence of baseline complete RBBB;
• Heart transplantation or implantation of an LVAD is planned within the next 6 months;
• Patients with intermediate or low risk of SCD;
• History of AMI less than three months prior to study inclusion;
• Acute renal and hepatic failure;
• Acute infectious diseases;
• Presence of mental illness;
• Presence of other illnesses for which life expectancy is less than one year;
• Patient refusal to participate in the study at any stage;