It is a group of disorders involving the system of generation and transmission of electrical impulses necessary for the heart's activity. The electrical phenomena precede and trigger the sequence of mechanical phenomena that result in the pumping activity of the heart (heart contraction).

The electrical impulses are transmitted via specialized cells in the atria and ventricles.
The specialized cells in the atrium are called the sinus node or sinoatrial node.

This is where the first electrical impulse is generated, causing the heart to beat in an orderly fashion. The electrical impulse travels along the atrial wall to the atrioventricular node (another group of specialized cells located at the junction of the atria and ventricles), where a small delay occurs (allowing the ventricles to fill with blood from the atria) and then propagates through a specialized network in both ventricles via the two main branches (right and left).

Normal cardiac activity consists of a regular succession of cardiac cycles (relaxation/contraction) with a resting, waking heart rate that varies in adults between 60 and 100 beats per minute. Heart rate is influenced by many factors (activity, stress, emotions, medication, acute or chronic conditions).

Any disturbance in the sequence of cycles in frequency or regularity, by the appearance of electrical stimuli from areas other than the usual areas and/or slowing, stopping or desynchronization of conduction at any level, constitutes a rhythm/conduction disorder.
It translates clinically as palpitations, arrest, skipped beats, dizziness, syncope (loss of consciousness), depending on the duration and type of cardiac arrhythmia.

Diagnostic methods of electrical conduction disorders

• LECG
• Stress test
• Holter ECG 24/48 hours
• Electrophysiologic study
• Tilt test
• Event loop recorder

Treatment

• Medications: antiarrhythmics
• Implantable antiarrhythmic devices aimed at the prevention, diagnosis and treatment of rhythm/conduction disorders:
• Pacemakers, including resynchronization therapy;
• Cardiac defibrillators
• Interventional cardiology procedures: ablative treatment (interrupting the arrhythmia maintenance mechanism)
• Surgical procedures

The most common rhythm disturbances are:

Supraventricular, originating in the atria:

• Sinus tachycardia - increased discharge frequency of electrical impulses from the sinoatrial node
• Sinus bradycardia - a decrease in the discharge frequency of electrical impulses from the sinoatrial node
• Atrial extrasystoles
• Presence of electrical impulses from the atria in places other than the sinus node
• Sinus node disease (brahi-tahi syndrome)
• Paroxysmal supraventricular tachycardia
• Atrial fibrillation/ atrial flutter
• Pre-excitation syndromes

Ventricular

• Ventricular extrasystoles - electrical impulses from the ventricular myocardium
• Ventricular tachycardia
• Ventricular fibrillation

Another category of electrical disturbances are conduction disturbances, i.e. blocks, which can be located at:

• Atrial level - sino-atrial blocks;
• Atrio-ventricular node - atrio-ventricular blocks, which represent blockage of the electrical impulse transmission from the atria to the ventricles, which can be without clinical significance or can reach complete block, with indication for pacemaker implantation;
• Ventricular level - branch blocks, which represent complete or partial block of the conduction of the electrical impulse through the ventricular branches (left or right bundle branch block, complete or partial), may require pacemaker implantation, depending on their association and symptomatology.

In patients who are required to take medication that causes a significant decrease in heart rate, pacing (implanting a pacemaker) may be necessary to prevent syncope (episodes of loss of consciousness).