It refers to a syndrome characterized by the successive or simultaneous appearance of numerous arrhythmias , caused by an alteration in the functioning of the NSA and, to a lesser extent, the rest of the structures of the specific system of generation and conduction of the cardiac impulse .
They are defined by the accompanying arrhythmias :
- Sinus bradycardia
It is the most common and earliest manifestation; It is usually persistent, without significant variations during exercise or administration of atropine, and sometimes severe. Alterations of the P wave may occur, characterized by changes in the electrical axis and the configuration of the wave, without variations in the PR interval or duration of the cycles, expression of intra-atrial conduction disorders
- Pauses sinus by blocking or stoppage SA
They constitute the most specific manifestation of the indicated syndrome .
- AV junction disorders
They can lead to longer, symptomatic sinus pauses , and escape rates, if they occur, are significantly bradycardial . Variable-grade AV blocks may be present , usually first-degree.
- Intraventricular conduction disorders
Especially from the anterior bundle of the left branch.
- Other atrial and ventricular arrhythmias
They are frequent and occur paroxysmally; alternate with the reported slow rhythms – bradycardia-tachycardia syndrome . The most common is the fibrillation atrial , but there may be atrial flutter, tachycardia paroxysmal supraventricular – reentrant, and more specifically of the NSA-, tachycardia nonparoxysmal AV junction; as well as atrial and ventricular premature complexes , and ventricular tachycardia .
- Slow ventricular response
It is characteristic during tachycardias , due to AV block, and abnormally long pauses after a salvo of tachycardia or an early stimulus.
It has an organic base, although a group of medicines , with antiarrhythmic action or not, can precipitate or aggravate its manifestations. It is observed more frequently in older adults , but it can occur in young people , and even children , associated with specific causes. The patients may be asymptomatic; the symptoms are nonspecific and depend on the duration of the pauses, the previous state of the cerebral circulation and the presence of the temporary tachyarrhythmia crises . Include palpitations , dizziness , fatigue, alterations of the intellectual capacity, syncope, presyncope, heart failure and angina .
It is related to the basic rhythm disorder and associated clinical manifestations, which must be attributed to the syndrome , in order for it to be justified. The bradycardia isolated with few symptoms may improve with administration of aminophylline . Patients with more severe symptoms are candidates for implantation of a permanent pacemaker . On the other hand, temporary rapid arrhythmias cannot be treated with specific drugs without adequate protection from a PM, a measure with which the symptoms often disappear .