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Adams-Stokes syndrome: Recurrent episodes of syncope and additional neurological symptoms caused by a drastic decrease in cardiac output due to particularly low heart rate.
Arrhythmia: Disorder in the normal heart rhythm. Any disturbance in the creation of the electrical stimulus or its conduction can cause irregular heart rate (arrhythmia). Arrhythmias can be paroxysmal and intermittent or chronic. They can originate in the upper cardiac compartments (vestibules or atria) or from the lower compartments (ventricles). Arrhythmias can be rapid or slow, without any clinical significance or life-threatening. The therapeutic approach depends on the sort, risk level, frequency of the appearance of the disturbance and its clinical consequences.
Artificial pacemaker: A device used for generating electrical signals and maintaining regular heart rhythm in patients suffering from a disturbance in electricity generation or transfer in the heart.

The need for an artificial pacemaker can be temporary and transient or chronic and permanent.

There are external pacemakers (the pulse generation takes place outside the chest), which are usually used for pre-hospitalization period.

In permanent pacemakers, the battery is implanted subcutaneously and the electrodes are implanted into the heart.
Artificial respiration: A resuscitation activity aimed at preserving the gas exchange in the lungs. It can be accomplished by various methods, beginning with mouth to mouth respiration and ending by the use of very sophisticated respiration machines.
Asystole: Finding of a flat line on ECG, meaning that electrical and mechanical activity of the heart is absent. Practically, during Asystole the electrical stimulation system of the heart does not trigger or conduct electrical stimuli, the muscle does not contract, there is a dramatic decline in cardiac output and the result is loss of consciousness, respiratory arrest and death. The treatment is defined as reanimation and consists of external cardiac massage, mechanical respiration and intravenous injections of medicines
Atrial fibrillation: A frequent rhythm disturbance (most frequent in elderly patients) originating from the atria and resulting in ineffective atrial contractions. It can result in rapid heart rhythm.

Due to the ineffective contraction of the atria, cardiac output is reduced and this can be clinically manifested by congestive heart failure, especially in patients with a significant background heart disease.

In addition, Atrial Fibrillation harbors an increased risk of formation of thrombi in the heart.

For this reason, people with chronic or frequent paroxysmal Atrial Fibrillation are often treated with drugs preventing thrombus formation, such as Coumadin.

Atrial fibrillation can be reverted by drugs or by electrical shock (Cardioversion).
Atrio-ventricular (AV) node: A group of cells within the Myocardium serving as a relay station for electrical signals transferred from the atria to the ventricles.

The existence of these cells is helpful for the synchronous and coordinated transfer of electrical signals from the atria to the ventricles and thus for preserving effective contraction of all heart compartments.
Bigeminy: Heart rhythm characterized by intermittent appearance of one normal beat (originating from the Sinus) followed by a second beat of atrial or ventricular origin.
Block: Disturbed electrical conductance in any part of the electrical conductive system of the heart.

Causes for the appearance of a block can be temporary and transient or chronic and permanent.

The chronic condition is more frequent in old age.

The location of a block in the conductive system may be important for the clinical effect resulting thereof.

Blocks in some sites may be unnoticeable and are detected accidentally when ECG is recorded. On the other hand, blocks can cause significant slowing of the heart rate (Bradycardia), which is accompanied by symptoms.

Possible treatment modalities depend on the clinical manifestation, the duration of the disorder, its causative factor and its risk potential.
Bradycardia: Slow heart rate, less than 60 beats per minute.

Bradycardia can be physiologic and normal, for example during sleep or in athletes.

However, bradycardia can also constitute a pathological state, resulting from a problem in the generation of the electrical stimulus in the heart or in impaired electrical conduction. The clinical significance depends on rate (how slow the rhythm), on duration of the disturbance and on the general state of the patient.

If necessary, the treatment may be by medication or by implanting a pacemaker.
Cardiac arrest (cardiopulmonary arrest): This is a state, in which the pump action of the heart comes to a stop.

Cardiac action can cease due to rhythm disorder of the ventricular fibrillation type (a very rapid heart rate with complete lack of synchronization between the muscle fibers of the heart and a resulting lack of efficacious contraction) or when asystoly (total cessation of electrical and mechanical activity of the heart) is present.

Symptoms develop rapidly and include: loss of consciousness, respiratory arrest and cessation of pulse. Without treatment, irreversible brain damage ensues in a matter of minutes followed by death.

The principal mode of treatment (resuscitation) includes: external cardiac massage, mechanical ventilation, interrupting the rhythm disorder by electrical shock (defibrillation) and proper medications.
Cardiac block: see entry: Block
Cardiopulmonary resuscitation (CPR): Performing emergency procedures aimed at preserving (at least partially) the cardiac and pulmonary functions.

The treatment includes external heart massage, by which sort of "squeezing" of the heart from outside is performed. By this squeezing partial filling and emptying of the heart is achieved.

In addition, resuscitation includes artificial ventilation that preserves oxygen vs. carbon dioxide exchange, which is the normal function of the lungs.

The term advanced resuscitation refers to medical treatment and electrical shock applied together with basic resuscitation procedures.
Cardioversion: Using electrical shock for stopping rapid rhythm disorder. In most cases, this procedure is applied when the rhythm disorder deteriorates the patient's state and requires immediate stop.

In contradistinction to the term "Defibrillation", which designates treatment by electric shock in Ventricular Fibrillation, a lethal rhythm disorder, the term "Cardioversion" is reserved for electrical treatment of rapid rhythm disorders that are not Ventricular Fibrillation.
Defibrillation: An electrical shock applied to the heart as treatment aimed at an immediate stopping of rapid rhythm disorders, which constitute a life threatening condition (for example Ventricular Fibrillation).
Defibrillator: A medical device destined for exerting an electrical shock to the heart for immediate stopping of rhythm disorders. Electricity is conducted by means of metallic plates located at predefined points on the chest. Some defibrillators are equipped with an automatic mechanism capable of recognizing a rhythm disorder and initiating the electrical shock accordingly. Some other subcutaneously implantable defibrillators deliver the electrical shock directly to the heart when dangerous rapid rhythm disorders are detected.
Electrical conduction system: A system originating from the natural pacemaker (Sinus) and ending in cells in the ventricles.

This system is capable of rapid transfer of electrical stimuli.

Its composition and structure assure that electric stimuli are transferred in a fully synchronized manner, i.e. each electrical pulse emerging from the Sinus reaches the cells in the ventricles at exactly the same time, which enables effective and powerful contraction.

With age, the conduction systems may be subject to different degenerative processes that in some cases necessitate the implantation of an artificial pacemaker.
Extra systole, premature beat: Normally, any electrical pulse engaging the heart muscle during each heart beat begins in the tissue called Sinus (SA node). This tissue has autonomic potential of generating such pulses.

This tissue is also known as natural pacemaker.

In some instances, for various reasons, electrical stimulation can be elicited from other sites in the heart, outside the Sinus, by cells that are under normal conditions not electrically active.

Usually, such impulse will be generated before the normal next impulse from the natural pacemaker, the Sinus, and it is therefore called "premature beat".

Another name for such premature beats is Extra-Systole.

Premature beats can be generated from a supra-ventricular source (from sites located above the ventricles) or from sites located in the ventricles.

In many instances, the reason for the generation of such premature beats is unknown. They are more frequent under the influence of substances such as caffeine, nicotine or alcohol. They can be also associated with cardiac diseases.

Sometimes such premature beats can give a sensation of irregular pulse or of interruptions in the normal heart action.

Most extra systoles do not require medical treatment. The decision about initiating medical treatment for the suppression of premature beats will depend on the subjective feeling of the patient as well as on the cause for their appearance.
Extrasystole, premature beat: See under Premature beat.
Flutter: A kind of rapid rhythm disorder causing the contraction of the afflicted part of the heart to be ineffective.

When such rapid rhythm affects the atria, it is called atrial flutter. Its consequences are similar to those of Atrial Fibrillation.

However, if this is found in the ventricles, ventricular flutter is an emergency situation requiring immediate life saving intervention. Without treatment this condition deteriorates to Ventricular Fibrillation and cardiac arrest.
Natural cardiac pacemaker: See entry: Sinus
Normal sinus rhythm (NSR): Heart rate originating from the Sinus (natural pacemaker) activity, i.e. resulting from an electrical stimulus generated in the Sinus and propagated normally by the electrical conduction system of the heart.

Sinus rhythm is defined as normal if the rate is between 60 and 100 per minute.

This rhythm can be above or below the limits of range in certain physiological situations, for instance during exercise or during sleep, respectively, but also as a reaction to pathological situation.
Palpitations: Awareness of heart beats.

This can be an unpleasant and an anxiety arising sensation.

The awareness of heart beats can be a normal phenomenon, for example in states of excitation, fear or exertion, in which the heart rate is accelerated.

Sometimes, the awareness of heart beat can be an evidence of a rhythm disorder, such as irregular, rapid or very slow heart beat.
Pounding of the heart: See entry: Palpitations.
Rhythm disturbances: see Arrhythmia

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