It is a group of disorders involving the system that generates and transmits the electrical impulses needed by the heart.

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 atria are called the sinus node or sinoatrial node.

This is where the first electrical impulse that causes the heart to beat in an orderly fashion is generated. The electrical impulse travels along the atrial wall to the atrioventricular node (another group of specialized cells 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 is the regular succession of cardiac cycles (relaxation/contraction) with a resting, awake 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 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 for ventricular disorders

• ECG
• 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 (brady-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

Driving disorders (blocks):

• Atrial level - sino-atrial blocks
• Atrioventricular node - atrioventricular blocks (may be clinically insignificant or may require pacemaker implantation)
• Ventricular level - bundle branch block (left or right bundle branch block, complete or partial, with possible need for pacemaker depending on symptoms)

In patients who are given medication that causes a significant drop in heart rate, a pacemaker may need to be implanted to prevent syncope (episodes of loss of consciousness).

See also:

www.stimulator.ro - Pacemaker
www.pace-maker.ro - Pace-maker
www.defibrilator-cardiac.ro - Cardiac Defibrillator / Implantable Cardioverter