الفهرس 
Physiological aspects of the heartOnly 14 pages are availabe for public view
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Abstract
Although off-pump surgery has emerged as an innovative technique, cardiopulmonary bypass (CPB) is performed in the majority of cardiac surgeries including coronary artery bypass grafting (CABG), valvular repair/replacement, congenital heart defects repair, and correction of abnormalities of great vessel.
Ventricular function has been reported to be impaired in as much as 96% of patients following CPB with complete recovery being achieved 24 to 48 h after surgery. In the operating room, low cardiac output syndrome (LCOS) has been defined as the inability to wean off CPB despite maximal support with a low cardiac index (<2.0-2.5 l/min/m 2) and evidence of end-organ dysfunction (e.g., urine output < 0.5 ml/kg/h).
The prevalence of LCOS in cardiac surgical patients range from 0.2% to 6% and it is associated with increased postoperative morbidity and mortality, increasing hospital length of stay, resource utilization, and overall costs.
The causes of ventricular dysfunction are multifactorial, including surgical tissue trauma, myocardial ischaemia-reperfusion injuries, down-regulation of beta-adrenergic receptors, coronary embolization (e.g., air, atheroma particle), activation of inflammatory and coagulation cascades, as well as uncorrected pre-existing cardiac disease. Perioperative myocardial infarction occurs in 7% to 15% of cardiac surgical patients and has also been incriminated in causing LCOS.
Knowledge of specific risk factors of post-CPB ventricular dysfunction is important for planning prophylactic cardioprotective interventions as well as early supportive therapy with cardiovascular drugs and eventually with mechanical circulatory devices.
Successful management involves more than ”inotropy”, the management of LCOS is based on a multi pronged strategy addressing the inflammatory, metabolic and hormonal causes of myocardial dysfunction. Systolic and/or diastolic dysfunction needs to be diagnosed and managed appropriately. Therapy also needs to be ”tailored” according to which ventricle is dysfunctional as the management of right ventricular and left ventricular dysfunction being quite different. Ventilatory adjustments are increasingly used as a ”haemodynamic tool” with better understanding of cardiopulmonary interactions in different circulations.
Inotropes are agents administered to increase myocardial contractility whereas vasopressor agents are administered to increase vascular tone. Inotropes and vasopressors are biologically and clinically important compounds that originate from different pharmacological groups and act at some of the most fundamental receptors and signal transduction systems in the body.
Mechanical circulatory support is life saving in patients who fail to improve or stabilize with intravenous inotropes or vasodilators, IABP support and mechanical ventilation, many types of mechanical support become available nowadays to bridge patients to another step of treatment plan.