Edit concept Question Editor Create issue ticket

Low Cardiac Output Syndrome

Low cardiac output syndrome is a postoperative complication caused by reperfusion and ensuing oxidative stress to the pulmonary and cardiac tissues. This syndrome is important to consider for its association with high morbidity and mortality due to impaired cardiovascular function.


Low cardiac output syndrome (LCOS) is a reduction in cardiac output often seen in postoperative situations, especially those of coronary artery bypass grafting (CABG), and cardiopulmonary bypass (CPB) [1] [2]. It happens on account of the oxidative stress caused by reperfusion after surgical manipulations. The oxidative stress, as well as inflammatory reactions, cause a disturbance of function in the myocardium resulting in a necessity of inotropic support [3]. Pulmonary tissues also undergo reperfusion that participates in the development of vascular reactivity and damage to the alveoli causing pulmonary edema; the latter is responsible for poor tissue oxygenation [4].

There are no strict clinical criteria for diagnosing the patient with possible LCOS. Strong indications for LCOS is hemodynamic instability and impaired tissue oxygenation occurring postoperatively. Additionally, one of the essential pointers is the need for administration of afterload reduction agents or inotropic agents e.g. dobutamine, epinephrine, and dopamine in order to maintain sufficient cardiac function [5]. Intra-aortic balloon counterpulsation support and positive pressure oxygenation are also important factors contributing to the diagnosis [3] [2].

On examination, the patient will reveal cold extremities, particularly in the most distal parts like toes, an absence of pedal pulse and a decrease in the systolic pressure measuring under 90 mmHg. Likewise, weakened perception of sensation may be noted [6]. LCOS is considered to be associated with high risk of morbidity and mortality, thus prompt recognition and preservation of adequate circulation are of immense importance [2].

  • Definition: oxygen delivery provided by CO does not meet oxygen demand (or CI 2.1 L/min/m2) due to inflammatory response of CPB, myocardial ischaemia from aortic crossclamp, hypo-/hyperthermia, reperfusion injury and surgical treatment (ventriculotomy[dontforgetthebubbles.com]
Wound Infection
  • Only one (1.7%) sternal wound infection occurred from a total of 147 patient-days of DSC.[ncbi.nlm.nih.gov]
Heart Disease
  • METHODS: After corrective surgery for congenital heart disease under CPB, 117 children (aged 10 days to 180 months) were enrolled in a prospective observational pilot study during a 2-year period.[ncbi.nlm.nih.gov]
  • BACKGROUND: Children with congenital heart disease often undergo heart surgery at a young age. They are at risk for postoperative low cardiac output syndrome (LCOS) or death.[ncbi.nlm.nih.gov]
  • PATIENTS: 99 consecutive eligible children who underwent a variety of surgical procedures for congenital heart disease, using cardiopulmonary bypass. All patients were cared for by a consistent perioperative care team.[ncbi.nlm.nih.gov]
  • Secondary postoperative outcomes investigated included myocardial injury, supraventricular arrhythmias, development of LCOS, acute kidney injury (AKI), duration of mechanical ventilation, intensive care unit and hospital lengths of stay, and incidence of hypotension[ncbi.nlm.nih.gov]
  • […] output syndrome (single vasoactive agent and mildly decreased perfusion), whereas 94% of those surveyed sometimes or always administer corticosteroids to patients with severe low cardiac output syndrome (two or more vasoactive agents and persistent hypotension[ncbi.nlm.nih.gov]
  • Etiology Syndrome ass. with CV instability and hypotension. • Sepsis ( Hypotension with ed SVR) • Anaphylactic reaction (blood products, drugs) • Adrenal insufficiency (primary or pt with preoperative steroids) • Protamine reaction 14.[slideshare.net]
  • A number of adverse events was examined, but differences between the treatment groups could not be proven for hypotension, intraventricular haemorrhage, hypokalaemia, bronchospasm, elevated serum levels of liver enzymes, or a reduced left ventricular[ncbi.nlm.nih.gov]
Left Ventricular Dysfunction
  • Prudent preoperative evaluation in patients with severe left ventricular dysfunction is critical. Further innovative research in myocardial protection and circulatory support is warranted in patients with severe left ventricular dysfunction.[ncbi.nlm.nih.gov]
  • Preoperative levosimendan decreases mortality and the development of low cardiac output in high-risk patients with severe left ventricular dysfunction undergoing coronary artery bypass grafting with cardiopulmonary bypass.[medintensiva.org]
Orthostatic Hypotension
  • Hypotension - Seizure, mental status change, diaphoresis, and signs of orthostatic hypotension and shock. Low cardiac output - Fatigue, weakness, dyspnea on exertion, lethargy, and lightheadedness.[en.wikipedia.org]
Refractory Shock
  • Hydrocortisone "stress dosing" is reported to provide hemodynamic benefits in some patients with refractory shock.[ncbi.nlm.nih.gov]
  • The symptoms occur because… … Medical dictionary Postural orthostatic tachycardia syndrome — (often referred to as just postural tachycardia syndrome or POTS) is a condition of dysautonomia, and more specifically, orthostatic intolerance, in which a change[medicine.academic.ru]


Low cardiac output syndrome can be the cause of decreased tissue oxygenation and disturbance in the cardiovascular system. Parameters evaluating the dynamics of this syndrome are linked with measurements of the arterial blood gas, central venous pressure, blood pressure, and estimates of the cardiac output.

It is possible to assess cardiac output (CO) directly by thermodilution. This technique includes a placement of the pulmonary artery catheter and is considered a gold standard for measuring the CO. It also gives data of right ventricle activity, such as right ventricular ejection fraction and right ventricular end diastolic volume. Although there are some drawbacks to this method, firstly it is an invasive procedure and secondly, it is not meant for continuous measurement of the CO [7]. There are other less invasive techniques for measuring the CO e.g. with transthoracic (TTE) or transesophageal (TEE) echocardiography.

LCOS is considered if the cardiac index (which is calculated with CO as a variable) is less than 2.2 L/min/m2, pulmonary artery occlusion pressure (PAOP) is more than 16 mmHg, and oxygen saturation drops to less than 60% [6] [8].

In the case of poor oxygenation caused by LCOS, serum lactate levels increase to more than 2 mmol/L for at least 2 hours and metabolic acidosis is recognized. Compensatory mechanisms will be exhibited by oliguria with urine output of less than 1.0 mL/kg/h [6].

Arterial blood gas analysis may uncover changes in partial arterial oxygen tension with less than 100 mmHg and partial arterial carbon dioxide tension of value exceeding the normal range of 35–45 mmHg. Central venous pressure is also likely to deviate from the norm of 6–8 mmHg [6] [9].


  • Milrinone , epinephrine, dopamine and dobutamine are mostly used, and should be prioritised for future research on LCOS treatment.[ncbi.nlm.nih.gov]
  • These haemodynamic effects were maintained over the 48 h of treatment and persisted 3 h after discontinuation of treatment.[ncbi.nlm.nih.gov]
  • Three trials with high overall risk of bias compared levosimendan to standard treatment (enoximone or dobutamine) or placebo.[ncbi.nlm.nih.gov]
  • While there is a broad body of evidence for the treatment of people with acute coronary syndrome under stable haemodynamic conditions, the treatment strategies for people who become haemodynamically unstable or develop CS remain less clear.[ncbi.nlm.nih.gov]
  • Treatment with levosimendan improved left heart function, and decreased lactate and brain natriuretic peptide levels.[ncbi.nlm.nih.gov]


  • In this respect, the prognosis was clearly poorer among the patients with cardiogenic shock. Two relevant findings were made in our study: 1.[medintensiva.org]
  • In this type of surgery, prior cardiovascular status is extremely important for prognosis and the, considerably higher, perioperative mortality is the most important individual factor taken into account when evaluating the quality of surgical programs[revespcardiol.org]
  • […] syndrome A clinical condition in which the cardiac output falls below tissue needs for O 2 Lab Vascular resistance and O 2 consumption, lactic acidosis, cardiac index, O 2 saturation Treatment Digitalis, vasopressors, dopamine, dobutamine, vasodilatation Prognosis[medical-dictionary.thefreedictionary.com]
  • "Relation of prognosis in sick sinus syndrome to age, conduction defects and modes of permanent cardiac pacing". Am. J. Cardiol. 65 (11): 729–35. doi : 10.1016/0002-9149(90)91379-K.[en.wikipedia.org]
  • Cardiac troponins are useful in diagnosis, risk stratification, and determination of prognosis.[eccguidelines.heart.org]


  • Multifactorial in etiology, this article will discuss the pathophysiology of low cardiac output syndrome, including myocardial depression following bypass, altered cardiac loading conditions, and inflammation driving a hypermetabolic state.[ncbi.nlm.nih.gov]
  • This article provides an overview of the determinants involved in oxygen transport, the physiologic factors influencing cardiovascular function, the assessment of hemodynamic variables, the etiology of LCOS, and management strategies, including a brief[unboundmedicine.com]
  • Etiology ed after load • Vasoconstriction • Fluid overload Diastolic dysfunction ( common finding after cardioplegic arrest) 13.[slideshare.net]


  • Criteria abstracted from The Users' Guide to Medical Literature, from the Health Information Research Unit and Clinical Epidemiology and Biostatistics, McMaster University Highlighted lines and questions below provide links to the pertinent description[pedsccm.org]
  • After consulting an electrophysiologist, possibly an additional pacemaker lead placement is needed, which eventually relieve some of the symptoms. [1] [4] Epidemiology [ edit ] The reported incidence of pacemaker syndrome has ranged from 2% [16] to 83%[en.wikipedia.org]
  • Epidemiology The prevalence of the ‘low cardiac output state’ is difficult to define.[clinicaladvisor.com]
Sex distribution
Age distribution


  • Multifactorial in etiology, this article will discuss the pathophysiology of low cardiac output syndrome, including myocardial depression following bypass, altered cardiac loading conditions, and inflammation driving a hypermetabolic state.[ncbi.nlm.nih.gov]
  • Pathophysiological mechanisms as well as the management of these major complications caused by LOS are also discussed. Some patients developed multiple organ failure (MOF). Plasma exchange (PE) was performed on 16 patients who developed MOF.[ncbi.nlm.nih.gov]
  • None of the currently used dosing regimens for milrinone achieved the therapeutic target range across all paediatric age groups and adult patients, so optimised dosing regimens were developed that considered the age-dependent and pathophysiological differences[ncbi.nlm.nih.gov]
  • Management---Inotropic and vasoactive drugs Selection of drugs Adequate understanding of underlying cardiac pathophysiology. Knowledge of α, ß or non adrenergic haemodynamic effects of these drugs. 52.[slideshare.net]


  • OBJECTIVE: Characterize current hospital practices related to preventive drug therapy for low cardiac output syndrome (LCOS) in children with open heart surgery (OHS) in Europe.[ncbi.nlm.nih.gov]
  • Thus potentially, levosimendan is a beneficial alternative to standard medication for the prevention of low cardiac output syndrome in paediatric patients after open heart surgery.[ncbi.nlm.nih.gov]
  • OBJECTIVES: This review examines the effectiveness of prophylactic postoperative use of milrinone to prevent LCOS or death in children having undergone surgery for congenital heart disease.[ncbi.nlm.nih.gov]



  1. Nashef SA, Roques F, Sharples LD, et al. EuroSCORE II. Eur J Cardiothorac Surg. 2012;41:734–44.
  2. Chandler HK, Kirsch R. Management of the Low Cardiac Output Syndrome Following Surgery for Congenital Heart Disease. Curr Cardiol Rev. 2016;12(2):107-111.
  3. Kunt AS, Andac MH. Decrease of Total Antioxidative Capacity in Developed Low Cardiac Output Syndrome. Oxid Med Cell Longev. 2012;2012:356301.
  4. Hiramatsu T, Imai Y, Kurosawa H, et al. Effects of dilutional and modified ultrafiltration in plasma endothelin-1 and pulmonary vascular resistance after the Fontan procedure. Ann Thorac Surg. 2002;73(3):861–865.
  5. Kucewicz-Czech E, Kiecak K, Urbańska E, et al. Perioperative care in elderly cardiac surgery patients. Kardiochir Torakochirurgia Pol. 2016;13(4):340-346.
  6. Chowdhury UK, Sheil A, Kapoor PM, et al. Short-term prognostic value of perioperative coronary sinus-derived-serum cardiac troponin-I, creatine kinase-MB, lactate, pyruvate, and lactate-pyruvate ratio in adult patients undergoing open heart surgery. Ann Card Anaesth. 2016;19(3):439-453.
  7. Huygh J, Peeters Y, Bernards J, Malbrain MLNG. Hemodynamic monitoring in the critically ill: an overview of current cardiac output monitoring methods. F1000Res. 2016;5:2855.
  8. Levin R, Degrange M, Del Mazo C, Tanus E, Porcile R. Preoperative levosimendan decreases mortality and the development of low cardiac output in high-risk patients with severe left ventricular dysfunction undergoing coronary artery bypass grafting with cardiopulmonary bypass. Exp Clin Cardiol. 2012;17(3):125-130.
  9. Lobos A-T, Lee S, Menon K. Capillary refill time and cardiac output in children undergoing cardiac catheterization. Pediatr Crit Care Med. 2012;13(2):136–140.

Ask Question

5000 Characters left Format the text using: # Heading, **bold**, _italic_. HTML code is not allowed.
By publishing this question you agree to the TOS and Privacy policy.
• Use a precise title for your question.
• Ask a specific question and provide age, sex, symptoms, type and duration of treatment.
• Respect your own and other people's privacy, never post full names or contact information.
• Inappropriate questions will be deleted.
• In urgent cases contact a physician, visit a hospital or call an emergency service!
Last updated: 2019-06-28 09:55