Sick Sinus Syndrome: Causes, Treatments and Preventions

What Is Sick Sinus Syndrome?

Sick sinus syndrome, also known as sinus node dysfunction or sinus node disease, is a type of arrhythmia originating from the sinoatrial node. This condition is relatively rare and mostly occurs in older adults due to age-related degeneration of the heart’s electrical conduction system.

In a healthy individual, the heart beats regularly at 60 -100 beats per minute, governed by the conduction system. Electrical impulses begin at the sinoatrial (SA) node in the right atrium, then propagate to the left atrium, the atrioventricular (AV) node, the bundle of His, and the Purkinje fibers, activating the ventricles. This coordinated contraction ensures efficient blood pumping throughout the body.

The SA node adjusts its firing rate based on the body’s physiological needs. During rest, the SA node slows the heart rate to conserve energy. In contrast, during physical exertion, stress, or sympathetic nervous stimulation, it increases the rate to meet the oxygen and nutrient demands of tissues.

In sick sinus syndrome, the SA node malfunctions, resulting in a heart rate that is too slow, irregular, or unable to increase appropriately. This leads to reduced cardiac output and impaired organ perfusion.

Causes of Sick Sinus Syndrome

Sick sinus syndrome can have various causes. Identifying the exact cause guides effective treatment and helps prevent complications.

• Age-related SA node degeneration: The most common cause, especially in the elderly, due to fibrosis or tissue degeneration, which may be worsened by underlying conditions like hypertension or diabetes.
• Surgical damage or scarring: Heart surgeries involving the right atrium (e.g., tricuspid valve replacement or congenital heart defect repair) may directly or indirectly damage the SA node.
• Cardiovascular diseases:
  • Coronary artery disease: Reduced blood supply to the SA node diminishes its activity.
  • Cardiomyopathies: Structural or functional changes in the heart disrupt electrical conduction.
  • Valvular heart disease: Hemodynamic disturbances from valve disorders can affect the SA node.
  • Myocarditis, endocarditis, or pericarditis: These inflammatory conditions may directly damage the SA node or surrounding pathways.
• Sleep apnea: Obstructive sleep apnea may trigger vagal stimulation, causing transient SA node pauses or bradycardia, and chronic hypoxia may damage conduction tissues.
• Medications: Beta-blockers, calcium channel blockers, and antiarrhythmic drugs may suppress SA node function.
• Genetic mutations: Some inherited mutations (e.g., HCN4, SCN5A) are linked to congenital forms of the condition.

Symptoms of Sick Sinus Syndrome

Symptoms may be absent or nonspecific, which makes diagnosis difficult. Common signs include:

• Palpitations or skipped heartbeats
• Chest discomfort
• Dizziness or lightheadedness
• Fatigue and exercise intolerance
• Shortness of breath, especially on exertion
• Confusion, memory lapses
• Fainting or near-fainting spells

These symptoms can resemble those of other arrhythmias, so medical evaluation is necessary to confirm the diagnosis.

Health Impact of Sick Sinus Syndrome

If left untreated, the condition can seriously impact health:

• Decreased cardiac output: Prolonged bradycardia or sinus pauses reduce blood and oxygen delivery, causing dizziness, fatigue, or fainting.
• Stroke risk: Alternating fast and slow heart rhythms (e.g., tachy-brady syndrome) may lead to atrial fibrillation and blood clot formation, increasing stroke risk.
• Heart failure: Persistent arrhythmias weaken the heart, potentially leading to chronic heart failure.
• Reduced quality of life: Symptoms such as fatigue and fainting affect daily function and emotional well-being.

Diagnosis

Patients should undergo a comprehensive evaluation at a cardiology clinic. Doctors will review symptoms and medical history, then perform a physical examination.

Diagnostic tests may include:

• Electrocardiogram (ECG): Detects abnormal heart rhythms linked to SA node dysfunction.
• Holter monitor: 24 – 48-hour portable ECG to capture intermittent arrhythmias.
• Event recorder: Activated during symptoms to capture transient arrhythmic events.
• Implantable loop recorder: A small device implanted under the skin to monitor heart rhythms over several months.
• Electrophysiology study (EPS): Invasive procedure to evaluate conduction pathways and localize dysfunction.

Treatment Options

The goal of treatment is to control symptoms, prevent complications, and improve quality of life.

Medication adjustments:

• Discontinue or reduce medications that suppress SA node function.
• Use antiarrhythmics cautiously in patients with both fast and slow rhythms.
• Prescribe anticoagulants (e.g., warfarin or DOACs) in patients with atrial fibrillation to prevent stroke.

Pacemaker implantation:

• Indicated for significant symptomatic bradycardia or sinus pauses.
• A small battery-powered device is implanted under the skin near the clavicle.
• Types:
  • Single-chamber: Lead in the right atrium or right ventricle.
  • Dual-chamber: Leads in both atrium and ventricle for synchronized pacing.
  • Biventricular (CRT): For patients with heart failure and conduction abnormalities.

Ablation therapy:

• Catheter ablation targets abnormal heart tissue causing tachyarrhythmias.
• AV node ablation is reserved for uncontrollable atrial fibrillation; requires permanent pacemaker afterward.

Prevention

Although not entirely preventable, progression can be slowed by:

• Healthy diet: Limit salt, saturated fats, processed foods. Increase intake of fruits, vegetables, and omega-3-rich fish.
• Regular exercise: Aim for 30 minutes/day of appropriate intensity.
• Blood pressure and cholesterol control: Through lifestyle and medication.
• Quit smoking and limit alcohol.
• Manage stress and ensure adequate sleep.
• Routine check-ups: Especially in older adults or those with cardiovascular risk factors.

HFH – Hanoi French Hospital provides expert cardiovascular services, including diagnosis and treatment of sick sinus syndrome. Dr. Alain Patrice Lebon, a certified cardiac electrophysiologist with 20 years of experience, leads the care team.

The hospital is equipped with:

• Electrocardiogram and Holter monitoring
• Personalized treatment protocols based on European Society of Cardiology guidelines
• 3D cardiac mapping (Abbott EnSite X EP System)
• Advanced DSA catheterization lab with top-tier infection control

For consultation or appointment, contact HFH at 024 3577 1100.