The function of the human heart is to pump oxygenated blood around the body and return deoxygenated blood to the lungs where carbon dioxide is exhaled and fresh oxygen enters the blood stream. In normal circumstances, the heart is a very efficient pump with the rate of its beating matched to meet the needs of the body. At rest, the adult heart typically beats at between 60 and 100 beats per minute.
Women tend to have faster heart rates than men and athletes have lower rates than sedentary individuals (as low as 40 to 60 beats per minute at rest). Under stress (e.g. anaerobic exercise), the heart rate can increase substantially to meet the body’s oxygen demands. As a rule of thumb, maximum heart rate is typically estimated as 220 minus a person’s age, but the real value depends on a range of factors, including body mass and general health.
This article looks at circumstances where the heart does not beat as efficiently as it should and considers the difference between ventricular flutter versus ventricular fibrillation.
The human heart consists of four chambers: the left and right ventricles and the left and right atria. Oxygenated blood enters the left atrium of the heart and is then pumped out and around the body via the left ventricle. Deoxygenated blood enters the heart through the right atrium and is then returned to the lungs after being pumped out of the right ventricle.
The synchronisation of the expansion and contraction of the heart is controlled by a group of cells known as the sinus node, located in the right atrium. It is the sinus node that is responsible for producing the electrical stimulus to cause the heart to beat. Atrial fibrillation is the most common form of an irregular heartbeat, or arrhythmia. An arrhythmia is caused by a problem with the electrical conductivity of the heart and can cause the heart to beat too slowly; too quickly, or irregularly. If the heart beats too quickly, the condition is known as tachycardia whereas if the rate is too slow, it is called brachycardia.
Ventricular flutter and ventricular fibrillation are conditions where the ventricles beat too quickly (tachycardia) or irregularly. These arrhythmias are usually because of an underlying heart disease and they originate in the ventricles of the heart. Since the output of the heart is affected, ventricular tachycardia (VT) often produces symptoms which may include breathlessness; chest pain; sweating, nausea and feeling faint — the condition can lead to a collapse. The duration of VT may last from a few seconds to a few minutes, but can have a longer duration. VT usually occurs in a damaged heart, for instance, in the hours following an initial heart attack, but it may have a genetic component. VT can progress into ventricular fibrillation or a heart attack.
Flutter Versus Fibrillation
In ventricular fibrillation, the heart beats at a very fast rate that the body can’t cope with. It ceases to pump efficiently and the heart “fibrillates" or quivers – a cardiac arrest.
The difference which differentiates ventricular flutter versus ventricular fibrillation is the nature of the arrhythmia. In the case of ventricular flutter, the electrical stimulation is regular, but very fast, leading to a circular depolarisation of the ventricle and loss of output, although some blood may be ejected from the heart. Often, ventricular flutter will deteriorate into ventricular fibrillation. In this case, depolarisation of the ventricle becomes chaotic and the frequency of beating is much higher. Somebody suffering from ventricular fibrillation (VF) is likely to become unconscious within a few seconds. In VF there is no coronary output. Unless a heart in ventricular fibrillation can be defibrillated (by applying a shock to the heart) and a normal rhythm be restored, death is inevitable.
- Anatomy of the heart: https://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_anatomy.html
- British Heart Foundation: HIS 14 (download) https://www.bhf.org.uk/plugins/PublicationsSearchResults/DownloadFile.aspx?docid=e1e03844-81e9-489a-ac88-b13a704148c9&version=-1&title=HIS14+Heart+Rhythms&resource=HIS14
- American Heart Association: https://www.americanheart.org/presenter.jhtml?identifier=4784