What is an Arrhythmia?
A cardiac arrhythmia is an abnormal or irregular heart beat. It occurs when there is abnormal electrical activity in the heart that drives the heart to beat too fast (tachycardia), beat too slow (bradycardia), or beat irregularly. The normal adult heart rate is between 60-100 beats per minute, and is called “sinus rhythm”. Some arrhythmias are very serious and can result in cardiac arrest or death, while other arrhythmias may not be so serious.
Some of the different names of arrrhythmias you may hear are:
- Supraventricular tachycardias (Atrial Fibrillation, Atrial Flutter)
- Ventricular tachycardias (Ventricular Fibrillation, Ventricular tachycardia)
- Bradycardias (heart blocks)
To understand the possible effects of an arrhythmia, we need to look at the way the cardiovascular system works.
What does the cardiovascular system do?
The cardiovascular system (CVS) consists of the heart and blood vessels. It is responsible for the transportation of nutrients (such as glucose), oxygen and hormones throughout the body. The heart functions as the central pump with the blood vessels acting as the pipes to the body. The CVS is controlled by a number of internal and external systems, with the goal of supplying as much oxygen and nutrients as the body needs. The heart is divided into a right and left side, each side having an atrium and ventricle. The contraction of the heart muscle pushes blood through the heart, and the heart valves control the direction of the flow by opening and closing at the right moments. The right side receives blood (with low oxygen content) from the major veins of the body and pumps this blood to the lungs. The blood picks up oxygen as it passes through the lungs, and then moves on to the left side of the heart. The left side of the heart pumps this blood into the aorta and arteries of the body. This pumping action is normally a complex well-coordinated activity. The heart muscle receives its blood supply via the left and right coronary arteries.
This image was sourced using a google image search
The heart muscle contracts when an electrical signal is generated from the part of the heart called the pacemaker (sinoatrial [SA] node) (See step 1 of diagram). The electrical signal travels through the 2 upper chambers of the heart (atria), which then contract and force blood into the 2 lower chambers (ventricles) (See step 2). The electrical signal then continues to passes through the atrioventricular node, which is near the centre of the heart, until it reaches the lower 2 chambers (ventricles) (See step 3). This electrical signal moves through the ventricular muscle, causing contraction of the 2 ventricles, and the blood moves out of the heart into the arteries (See step 4). In a healthy person, this process results in a normal resting heart rate of 60 to 100 beats a minute. The movement of blood through the arteries can be felt as a ‘pulse’ in the wrist and the neck.
What are the causes of Arrhythmias?
There are a number of possible causes, but only some of the people who have these conditions with get an arrhythmia.
- A person with a weak heart muscle (heart failure) is more likely to suffer from an arrhythmia
- Imbalance in electrolytes (eg too much or too little potassium or magnesium)
- Over-active or under-active thyroid gland
- Extremes of physical exertion
- Extreme heat (hyperthermia) or cold (hypothermia)
- Heart attack (when part of the heart muscle dies because there has been a blockage in a coronary artery).
What are the signs and symptoms of Arrhythmias?
What are the treatment options?
What happens in Intensive Care?
When a person is admitted to Intensive Care with a dysrhythmia the main aim of therapy is to reverse the cause of the irregular heart rhythm. The management of the patient will depend on how critical they are
- Monitoring of the heart rate, blood pressure, respiratory rate, oxygen saturation and temperature. This will be seen on a bedside monitor.
- An arterial line may be inserted to monitor blood pressure and to take blood samples.
- A central venous catheter may be inserted so that that anti-dysrhythmic medication can be given as well as intravenous fluids. These will be given via infusion pumps.
- Oxygen may be delivered via a face mask.
- Mechanical ventilation via an endotracheal tube to assist with breathing. The ventilated patient will require suctioning to remove secretions from the lungs and airways.
- If the patient is unable to eat, nutrition may be provided via a nasogastric tube. This is a tube that is placed in the nose and goes down the throat into the stomach Fluid can also be removed from the stomach via the nasogastric tube.
- Insertion of an indwelling urinary catheter to drain and measure urine output.
- Chest x rays and other tests such as blood tests, CT scan, MRI, echocardiogram, electrocardiogram (ECG), and urine tests.
- Sequential compression devices may be put on the legs to prevent the formation of blood clots.
- An air mattress may be used to prevent pressure areas developing on the skin.
How long will the patient remain in ICU for?
The length of time a person stays in the ICU depends on what type of arrhythmia they have, and if any complications have occurred as a result. Please ask the ICU nurse or doctor if you have any questions.
The information contained on this page is general in nature and therefore cannot reflect individual patient variation. In addition it reflects Australian intensive care practice which may differ from other countries. It is meant as a back up to specific information which will be discussed with you by the Doctors and Nurses caring for your loved one. ICCMU attests to the accuracy of the information contained here BUT takes no responsibility for how it may apply to an individual patient. Please refer to the full disclaimer.
Arrhythmias Version 1
Authors Kathleen Ryan CNC ICCMU & Dr Louise Cole Staff Specialist Nepean ICU
Published August 2008