Ectopic supraventricular rhythm.

These are the various rhythms that originate from supraventricular sources (usually the atria). Many conditions are asymptomatic and do not require treatment.

Atrial extrasystole (PES), or premature atrial contraction, is a common episodic extra impulse. They can occur in a normal heart with or without provoking factors (e.g., coffee, tea, alcohol, ephedrine analogues) or may be a sign of cardiopulmonary disorders. Sometimes they cause palpitations. The diagnosis is established based on ECG data. Atrial extrasystoles can be normal, aberrant, or without conduction. Normally conducted atrial extrasystoles are usually accompanied by an uncompensated pause. Aberrantly conducted atrial extrasystoles (usually with right bundle branch block) must be distinguished from ventricular extrasystoles.

Atrial escape beats are ectopic atrial beats that follow a prolonged sinus pause or arrest. They may be single or multiple. Escape beats from a single focus may create a continuous rhythm (called an ectopic atrial rhythm). The heart rate is usually decreased, the shape of the P wave may be variable, and the P-P interval is somewhat shorter than in sinus rhythm.

Migrating atrial pacemaker (multifocal atrial rhythm) is an irregular rhythm resulting from random excitation of a large number of foci in the atria. By definition, the heart rate must be < 100 beats per minute. This arrhythmia occurs more often in patients with lung disease and in a state of hypoxia, acidosis, theophylline overdose, or a combination of these causes. On the electrocardiogram, the shape of the waves is different with each contraction: three or more different R wave shapes are detected. The presence of waves distinguishes migrating pacemaker from atrial fibrillation.

Multifocal atrial tachycardia (chaotic atrial tachycardia) is an irregular rhythm resulting from the random excitation of a large number of foci in the atria. By definition, the heart rate must be > 100 beats per minute. Except for this sign, all other characteristics are similar to pacemaker migration. Symptoms, if they occur, are the same as in severe tachycardia. Treatment is directed at the primary pulmonary cause.

Atrial tachycardia is a regular rhythm resulting from continuous rapid activation of the atria from a single focus in the atria. The heart rate is usually 150-200 beats per minute. However, with very high atrial excitation rate, dysfunction of the nodes of the conduction system, intoxication with digitalis preparations, AV block may occur and the ventricular rate will decrease. Mechanisms include increased atrial automaticity and an intra-atrial re-entry mechanism. Atrial tachycardia is the least common (5%) of the supraventricular tachycardias; it usually develops in patients with structural heart disease. Other causes include atrial irritation (eg, pericarditis), drug effects (digoxin), alcohol intake, and exposure to toxic gases. Symptoms are similar to those of other tachycardias. Diagnosis is based on ECG data. R waves, which differ in shape from normal sinus waves, precede the QRS complex but may be "hidden" by the preceding T wave. Vagal maneuvers may be used to slow the heart rate, which help visualize the P waves if they are "hidden," but these maneuvers usually do not terminate the arrhythmia (indicating that the AV node is not an essential part of the impulse circulation). Treatment consists of correcting the underlying cause and slowing the ventricular rate with beta-blockers or calcium channel blockers. The arrhythmia may be terminated by direct cardioversion. Pharmacological approaches to stopping and preventing atrial tachycardias include antiarrhythmic drugs of classes Ia, Ic, and III. If noninvasive methods are ineffective, suppressive cardiac pacing and radiofrequency ablation of the excitation focus are alternatives.

Nonparoxysmal junctional tachycardia results from abnormal automaticity in the AV junction or other tissue (often associated with open-heart surgery, acute anterior myocardial infarction, myocarditis, or digitalis intoxication). The heart rate is usually between 60 and 120 beats per minute, and symptoms are usually absent. The ECG shows a regular, normally formed QRS complex without well-defined waves or with retrograde waves (inverted in the inferior leads) that appear immediately before (< 0.1 sec) or after the ventricular complex. The rhythm differs from paroxysmal supraventricular tachycardia by its lower heart rate and gradual onset and offset. Treatment depends on the cause.

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