Ranolazine a Potential New Therapeutic Application

Overview

Despite surgical and medical innovation have reduced mortality rates in cardiac surgery, the disease severity and operative procedural complexity have increased and morbidity rate is still high. Ischemia-reperfusion (I/R) injury, redefined in cardiac surgery "post-cardioplegic injury" (2) as a whole of ischemia-reperfusion, cardiopulmonary bypass and surgical trauma, has been recognized as a significant contributor to mortality and morbidity. I/R injury is classified as reversible or irreversible. Reversible injury includes arrhythmias, edema, vascular dysfunction and contractile stunning expressed as low output syndrome without cell death and without apparent signs of infarction or other serum injury markers. Irreversible reperfusion injury includes apoptosis and necrosis. I/R injury is a complex process associated with increase of radical, oxidant and cytokines production, complement and neutrophil activation and endothelial activation leading to microvascular dysfunction and deterioration of coronary flow reserve. In the hypoxic heart increase anaerobic lactate production, K+ efflux and membrane depolarization. The intracellular Na+ concentration rises as a consequence of slow Na+ channels inactivation and the induction of voltage-gated Na+ channel late current component (late INA). Intracellular Na++ accumulation enhanced activity of reversed-mode Na+-Ca++ exchanger causing intracellular Ca++ overload and ventricular dysfunction. Therefore inhibition of late INA has been shown to be cardioprotective. Ranolazine, an FDA-approval antianginal and anti-ischemic agent, high selective blocker of late INA, inhibits the late sodium current in myocardial ischemia, decreases Na+ and Ca2+ overload and improves left ventricular function in experimental animal models. For this reason it was also adjuncted to cardioplegia improving diastolic function in isolate Langerdoff-perfused rat hearts. The authors test the hypothesis that ranolazine improve myocardical protection in patients undergoing coronary artery surgery with cardiopulmonary by-pass (CPB).

We aim to perform a prospective, single-center, investigator-initiated, randomized (1:1), blinded, placebo-controlled study. The patients undergoing elective and complete CABG revascularization performed by the same surgeon, will be randomized in two different groups to receive, in the three days before surgery, Ranolazine at a dose of 375 mg twice daily or placebo. After the enrollement in the research according the inclusion and exclusion criteria, the randomization list will be computer-generated. The study participants, the reserchers responsible for data reporting and analysis and the ecocardiographers will be blinded to the treatment that each patient will receive. In a previous phase all data for the recruitment will be considered and registered before surgery: basic clinical parameters (age, gender, height, weight, body surface, systolic blood pressure and diastolic blood pressure, mean heart rate); medical history (diabetes mellitus type I or II, smoking status, chronic obstructive pulmonary desease, systemic arterial hypertension, dyslipidemia, family history of cardiovascular events, angina, percutaneous coronary interventions (PCI), acute myocardial infarction (AMI), previous cardiac surgery, chronic peripheral arterial disease, cerebral ischemia, bleeding and chronic renal failure); basic hematologic parameters (creatinine, glucose, hemoglobin, hematocrit, white blood cell counts and equation, platelets number, aPTT, INR); baseline transthoracic echocardiographic (TTE) parameters (left ventricular ejection function (LVEF), left ventricular volumes, left ventricular regional wall motion, diastolic function (mitral inflow velocities as Early diastolic velocity (E), late diastolic velocity with atrial contraction (A), and deceleration time (DT), early diastolic velocity (e') and late diastolic velocity with atrial contraction (a') using tissue Doppler imaging, pulmonary artery systolic pressure (PASP), valvulopathy and aortic desease); assestment of risk stratification according to different scores (New York Heart Association (NYHA) classes, Canadian Cardiovascular Society (CCS) Angina grading scale, EUROSCORE II, American Society og Anesthesiologists (ASA) physical status classification system); preoperative patient therapy. In a following phase laboratory, hemodynamic and imaging evaluation will be carried out during and subsequent to CABG surgery. Through a coronary sinus inserted catheter will be dosed Troponine I (TnI) immediately before CPB and after the release of aortic cross clamp, about 10 minutes after the end of reperfusion. TnI will be also dosed at arrival on intensive care unit and 6, 12, 24, 48 h after unclamping of the aorta. Blood samples will be collected simultaneously from the radial artery and the coronary sinus before starting CPB and after removal of aortic cross clamp to evaluate lactates extraction, oxygen consumption (VO2) and oxygen extraction (O2ER), and C-reactive protein (CRP) pre and post-CPB. Hemodynamic measurements will be obtained by an arterial and a pulmonary artery catheter (PAC) inserted before surgery, and will include arterial pressure (systolic, diastolic and mean pressure), pulmonary artery pressure (PAP), right atrial pressure (RAP), pulmonary artery wedge pressure (PAWP), cardiac output (CO) and cardiac index (CI), systemic vascular resistance (SVR), left ventricular stroke work (LVSW), left stroke volume variaton (LSVV) and coronary artery perfusion pressure (CPP); these measurements will be conducted 30 min after intubation, after sternotomy, 10 min after protamin, after sternosynthesis, at arrival in the intensive care unit, 6, 12, 24, 36, 48 h after CPB. Lastly a transesophageal echocardiographic study will be performed by two expert echocardiographers following the protocols of the Society of Cardiovascular Anesthesiologists (21) and American Society of Echocardiography (22). Left ventricle myocardial performance index, LVEF, left ventricular regional wall motion, E/A ratio, E', E/E' and deceleration time (DT) of mitral inflow velocity will be measured; these measurements will be obteined 30 minute after intubation before sternotomy and ten minute after protamin. All collected data will be entered into a database in Excel format.