biology

Low cardiac output syndrome

Low cardiac output syndrome is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Low cardiac output syndrome rather than just read about it. In short: Low cardiac output syndrome (LCOS), or simply low cardiac output, also known as decreased cardiac output (DCO), is a transient cardiovascular syndrome in which cardiac output is below normal and acceptable limits. It can result in tissue hypoperfusion and associated symptoms.

Key takeaways

Low cardiac output syndrome belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Low cardiac output syndrome to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Low cardiac output syndrome from memory before moving on to harder problems.

Reference excerpt

Low cardiac output syndrome (LCOS), or simply low cardiac output, also known as decreased cardiac output (DCO), is a transient cardiovascular syndrome in which cardiac output is below normal and acceptable limits. It can result in tissue hypoperfusion and associated symptoms. When complicated by multiorgan dysfunction due to hypoperfusion, LCOS is instead defined as cardiogenic shock (CS).

Definition Cardiac output (CO) is defined as the volume of blood that is pumped by the heart to the systemic circulation per minute and represents the total blood flow in the body. It can be calculated as cardiac output equals heart rate (HR) times stroke volume (SV). Cardiac index (CI) is CO adjusted or normalized by body size, and has the formula CO divided by body surface area (BSA). There is no absolute definition of LCOS, but definitions sometimes include a CI of less than 1.8 L/min/m2, or less than 2.2 L/min/m2 with inotropic drugs.

Causes There are various different causes of LCOS, for instance shock, cardiac surgery, arrhythmias like bradycardia, and acute decompensated heart failure (ADHF), among others.

Signs, symptoms, and diagnosis Presenting signs and symptoms of LCOS include hypotension (systolic blood pressure of less than 90 mmHg for at least 30 minutes) and end-organ hypoperfusion such as cool extremities, low urine output of less than 30 mL/hour, altered mental status, or elevated lactate. Other signs and symptoms include tachycardia, narrow pulse pressure, other indications of poor perfusion like weak pulses and slow capillary refill time (CRT), and oliguria or anuria (low or absent urine output). Defining characteristics of LCOS that occur with high frequency have been found to include altered heart rate/rhythm (77%), dyspnea (43–77%), labile blood pressure (69%), rales (69%), oliguria or anuria (62%), edema (61–71%), cold and/or clammy skin (53%), jugular vein distension (43%), fatigue and/or weakness (43–46%), decreased peripheral pulses (46%), and decreased peripheral perfusion (46%). Various other symptoms were also found to occur with lower frequency. There is a continuum between LCOS and cardiogenic shock (CS). In CS, there is additionally multiorgan dysfunction. CS is an acute and life-threatening condition requiring immediate medical attention.

Treatment Little evidence is available to inform treatment of LCOS. Possible treatments may include inotropic agents and vasodilators. Examples of specific medications include the catecholamine sympathomimetics dopamine, dobutamine, epinephrine, norepinephrine, and isoprenaline (isoproterenol); the calcium sensitizer levosimendan; the phosphodiesterase PDE3 inhibitors amrinone, milrinone, and enoximone; and, in some subgroups, pure vasodilators like nitroglycerin, nitroprusside, or inhaled nitric oxide (NO).

Research The calcium sensitizer levosimendan and the HCN4 blocker ivabradine are under formal development for treatment of low cardiac output. Levosimendan is in phase 3 clinical trials for this indication, while ivabradine is in phase 2 trials.

References

Worked examples

Example 1 — a first encounter with Low cardiac output syndrome

Start with the simplest possible case. Write down what Low cardiac output syndrome claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Low cardiac output syndrome before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Low cardiac output syndrome ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Low cardiac output syndrome

In research: Low cardiac output syndrome appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Low cardiac output syndrome in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Low cardiac output syndrome is common in secondary-school and first-year university syllabi. It links to neighbouring topics Heart diseases, Intensive care medicine, Medical emergencies, so understanding it makes those chapters shorter.
In everyday life: Look for Low cardiac output syndrome outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Low cardiac output syndrome in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Low cardiac output syndrome means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Low cardiac output syndrome out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Low cardiac output syndrome in simple terms?

Why does Low cardiac output syndrome matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Low cardiac output syndrome?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Low cardiac output syndrome.