Sinus node dysfunction in non-medicational treatment of atrial fibrillation
Sinus node dysfunction or sick sinus syndrome (SSS) includes clinical conditions such as symptomatic sinus bradycardia, sinus pauses or arrest, sinus node exit block, atrial tachycardias and chronotropic incompetence. Even though SSS incidence increases in an exponential-like manner with age, it can occur at all ages, including in the newborn. The mean age of patients with the syndrome is 68 years, with both genders being affected in approximately equal proportion. This condition occurs in 1 of every 600 cardiac patients over 65. Degenerative fibrosis of the tissues of the node has been suggested to be a common cause of SSS. Although it is still disputed. SSS is frequently associated with atrial fibrillation and flutter, tachy-bradycardia syndrome. Tachy-bradycardia syndrome is defined as sinus bradycardia coupled with atrial flutter/fibrillation or reciprocal atrial tachycardia. This syndrome is common in young patients following a surgical treatment of a congenital heart disease. Patients with chronic or persistent atrial flutter/fibrillation show high rates of cardiovascular disorders and mortality while sinus bradycardia is thought as an independent risk factor of atrial flutter/fibrillation. There are certain restrictions to medical treatment: long-term administration of the same medication (sotalol, amiodarone) for atrial flutter/fibrillation can cause symptomatic bradycardia while administration of other medication (a class 1 drug) increases the likelihood of ventricular arrythmias or evident bradycardia that enhances the risk of sudden cardiac death. Following atrial fibrillation ablation patients saw a significant improvement in the sinus node function, or saw a better sinus node function disrupted due to remodelling that takes place during atrial fibrillation. The surgical methods applications proved most efficient in non-medicational treatment of atrial fibrillation. In the late 1980s American surgeon J. L. Cox developed a so-called Maze procedure. This is what it is about. The mechanism of atrial fibrillation is regarded as macro-reentry, i.e. there are several circuits for reentrant excitation (base of the pulmonary vein, mitral and tricuspid valves, other holes, particularly the auricle, etc.). The operation involves electrical isolation (cuts and criotherapy) of these areas and transition of three internodal paths into one. The operation was shown to be efficient in long-term maintenance of the sinus rhythm in permanent atrial fibrillation.