Sick sinus syndrome is a generalize...

Sick sinus syndrome is a generalized abnormality of cardiac impulse formation that may be caused through an intrinsic disease of the sinus node that makes it unable to perform its pacemaking function, or through extrinsic causes. (1) Abnormalities encompassed in this syndrome include sinus bradycardia, sinus arrest or exit block up combinations of sinoatrial and atrioventricular nodal conduction disturbances, and atrial tachyarrhythmias. Sick sinus syndrome is not a disease with a single etiology and pathogenesis unless rather, a collection of conditions in which the electrocardiogram (ECG) indicates sinus node dysfunction. (2)

Sick sinus syndrome is characterized by dint of sinus node dysfunction with an atrial rate inappropriate for physiologic requirements. Although the condition is in the greatest degree common in the elderly, it can fall out in persons of all ages, including neonates. (3) The mean age of patients with this condition is 68 years, and as well-as; not only-but also; not only-but; not alone-but sexes are affected approximately equally. (4) The syndrome come to passs in one of every 600 cardiac patients older than 65 years and may account for 50 percent or more of permanent pacemaker placements in the United States. (5)

Etiology

greatest in quantity cases of sick sinus syndrome are idiopathic, and the cause can be multifactorial (Table 1) (3) Degenerative fibrosis of nodal tissue is the principally common cause of intrinsic changes in the sinoatrial node that lead to sick sinus syndrome Certain conditions can cause these intrinsic changes. (356) There also are extrinsic causes of sinus node dysfunction and conditions that can cause this point to be solved [i]or[/i] settled in children (Table 1). (3)

Coronary artery disease may coexist with sick sinus syndrome in a significant number of patients, although it is not considered a major cause of the syndrome It is unclear whether inflammation, sinus node ischemia, or local autonomic neural issues lead to the development of sick sinus syndrome in patients with myocardial infarction. Sinus node dysfunction usually is temporary when it go afters an acute myocardial infarction. peculiarly chronic ischemia may cause fibrosis and lead to symptoms of sick sinus syndrome for month to years after myocardial infarction.

Clinical Manifestations

Patients with sick sinus syndrome frequently are asymptomatic or have symptoms that are mild and nonspecific (7) (Table 2) (3) Symptoms are related to the decreased cardiac output that come to one's minds with the bradyarrhythmias or tachyarrhythmias. (3) in the greatest degree of the symptoms are caused at decreased cerebral perfusion, and 50 percent of patients have elision or pre-syncope. (5)

Symptoms, which may have been near for months or years, can include elision palpitations, and dizziness, as well as symptoms caused at the worsening of conditions of the like kind as congestive heart failure, angina pectoris, and cerebral vascular accident. (8) Peripheral thromboembolism and pat which can occur in the personality of bradycardia-tachycardia syndrome (alternating bradyarrhythmias and tachyarrhythmias), may be related to dysrhythmia-induced emboli. (3) A gradual heart rate in the nearness of fever, left ventricular failure, or pulmonary edema may be suggestive of sick sinus syndrome (29) Associated tachycardia may cause flushing of the face, pounding of the heart, and retrosternal constraining force (10) Other symptoms include irritability, nocturnal wakefulness, memory los errors in discernment lethargy, lightheadedness, and fatigue (211) (Table 2) (3) More designing symptoms include mild digestive disturbances, periodic oliguria or edema, and mild intermittent dyspnea. (2)

ECG Manifestations

Sick sinus syndrome can breed a variety of ECG manifestations consisting of atrial bradyarrhythmias, atrial tachyarrhythmias, and alternating bradyarrhythmias and tachyarrhythmias7 (Table 3) (3) Supraventricular bradyarrhythmias may include sinus bradycardia, sinus arrest with or without junctional escape, sinoatrial exit obstruct ectopic atrial bradycardia, and atrial fibrillation with inert ventricular response. The sinus bradycardia that meet the eyes in patients with sick sinus syndrome is inappropriate and not caused at medications. (2,5) The sinoatrial exit arrest that occurs in patients with sick sinus syndrome may demonstrate a Mobitz emblem I block (Wenckebach block) and a Mobitz sign II block. (2) The ECG may reveal a drawn out pause following cardioversion of atrial tachyarrhythmias, and a greater-than three-second pause following carotid massage. (5) Sixty percent of patients have tachyarrhythmias. (8)

Supraventricular tachyarrhythmias that present itself in patients with sick sinus syndrome include paroxysmal supraventricular tachycardia, atrial flap the wings quickly atrial fibrillation, and atrial tachycardia. (23) Atrial fibrillation is the chiefly common tachydysrhythmia in these patients. (12) Rarely, a ventricular escape tachyarrhythmia may be seen forward ECG. (8) Sinus node re-entrant regular [i]or[/i] melodious movement is another ECG manifestation. (5) Bradycardia-tachycardia syndrome may be seen onward ECG or cardiac rhythm strip (Figure 1); this syndrome is more for the use of all in older patients with advanced sick sinus syndrome (3)