Įxercise stress tests can be utilized to identify intrinsic causes of sinus node dysfunction. If Holter or telemetry monitoring fails to identify ECG changes and suspicion of sinus node dysfunction remains high due to severe symptoms or episodes of syncope, implantable loop recorders should be considered for extended monitoring up to 24 months. If ECG findings cannot be identified, prolonged cardiac monitoring should be pursued either with a Holter monitor in an outpatient setting or telemetry while inpatient, due to the transient nature of abnormal ECG findings. Clinical diagnosis ĭiagnosing sinus node dysfunction requires clinical symptoms as well as ECG abnormalities. Sinus node dysfunction can also present with sudden sinus arrest with or without junctional escape, sinoatrial block, prolonged asystolic period followed by tachycardias, or tachycardia-bradycardia syndrome presenting as various atrial arrhythmias such as atrial fibrillation, flutter, tachycardia, or paroxysmal supraventricular tachycardia. The primary 12-lead electrocardiogram (ECG) finding in sinus node dysfunction is inappropriate sinus bradycardia. Diagnosis Įlectrocardiogram (ECG) of a 64-year-old female with sinus bradycardia. Hypothyroidism, hypoxia, hypothermia, and various toxins have also been associated with sinus node dysfunctions. Electrolyte abnormalities such as hyperkalemia, hypokalemia, and hypocalcemia can also alter normal sinus node functioning. Extrinsic causes Ĭommon cardiac pharmacology such as beta-blockers, calcium channel blockers, digoxin, sympatholytic medication, and other antiarrhythmics can alter sinus node function to create an arrhythmia such as sick sinus syndrome. Inherited sinus node dysfunction has been associated with mutations of the gene responsible for the formation of the alpha subunit of the sodium channel ( SCN5A). Other intrinsic causes include inherited ion channel dysfunctions, remodeling diseases such as heart failure and atrial fibrillation, infiltrative diseases such as sarcoidosis, amyloidosis, hemochromatosis, and connective tissue diseases, inflammatory etiology such as rheumatic fever, Chagas disease, and Lyme disease, as well as atherosclerotic and ischemic changes to the sinus node artery. Intrinsic causes Īge-related degenerative fibrosis of the sinus node is often identified as the most common intrinsic cause. Intrinsic causes tend to be responsible for permanent sinus node dysfunction while extrinsic causes are more commonly temporary. Intrinsic causes can include degeneration, dysfunction, or remodeling of the sinus node while extrinsic causes can create or worsen underlying atrial arrhythmias. Sinus node dysfunction can be caused by intrinsic and extrinsic factors that affect the normal functioning of the sinus node. Sinus node dysfunction has a close association with the presence of atrial fibrillation due to their shared etiology of remodeling. ĭeveloping sinus arrest, sinus node exit block, sinus bradycardia, atrioventricular block, and other types of abnormal rhythms are also common complications. These rhythms increases the risk of clot formation in the atrium, embolization, and stroke. The most common complication of sinus node dysfunction is the development of tachycardia-bradycardia syndrome with abnormal atrial rhythms such as atrial tachycardia, atrial fibrillation, and flutter. This ECG from the same patient shows atrial fibrillation at around 126 beats per minute. Patients can also present with symptoms of congestive heart failure, stroke or transient ischemic attacks due to the abnormal rhythm. Signs and symptoms usually appear in more advanced disease and more than 50% of patients will present with syncope or transient near-fainting spells as well as bradycardias that are accompanied by rapid heart rhythms, referred to as tachycardia-bradycardia syndrome Other presenting signs or symptoms can include confusion, fatigue, palpitations, chest pain, shortness of breath, headache, and nausea. Often sinus node dysfunction produces no symptoms, especially early in the disease course. Tachycardia-bradycardia syndrome is a variant of sick sinus syndrome in which the arrhythmia alternates between fast and slow heart rates. Sinus node dysfunction (SND), also known as sick sinus syndrome (SSS), is a group of abnormal heart rhythms ( arrhythmias) usually caused by a malfunction of the sinus node, the heart's primary pacemaker. Telemetry strip of a 44-year-old female with asymptomatic sinus pause found while admitted for mildly symptomatic COVID-19 pneumonia.
Sick sinus syndrome or sinoatrial node disease Medical condition Sinus node dysfunction (SND)
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