Sick sinus syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Sick sinus syndrome (also known as sinus node dysfunction) is a group of related heart conditions that can affect how the heart beats. "Sick sinus" refers to the sino-atrial (SA) node, which is an area of specialized cells in the heart that functions as a natural pacemaker. The SA node generates electrical impulses that start each heartbeat. These signals travel from the SA node to the rest of the heart, signaling the heart (cardiac) muscle to contract and pump blood. In people with sick sinus syndrome, the SA node does not function normally. In some cases, it does not produce the right signals to trigger a regular heartbeat. In others, abnormalities disrupt the electrical impulses and prevent them from reaching the rest of the heart.

Sick sinus syndrome tends to cause the heartbeat to be too slow (bradycardia), although occasionally the heartbeat is too fast (tachycardia). In some cases, the heartbeat rapidly switches from being too fast to being too slow, a condition known as tachycardia-bradycardia syndrome. Symptoms related to abnormal heartbeats can include dizziness, light-headedness, fainting (syncope), a sensation of fluttering or pounding in the chest (palpitations), and confusion or memory problems. During exercise, many affected individuals experience chest pain, difficulty breathing, or excessive tiredness (fatigue). Once symptoms of sick sinus syndrome appear, they usually worsen with time. However, some people with the condition never experience any related health problems.

Sick sinus syndrome occurs most commonly in older adults, although it can be diagnosed in people of any age. The condition increases the risk of several life-threatening problems involving the heart and blood vessels. These include a heart rhythm abnormality called atrial fibrillation, heart failure, cardiac arrest, and stroke.

Inheritance

From: MedlinePlus Genetics, National Library of Medicine

Autosomal recessive; Autosomal dominant

Understanding terms used in the source

These definitions explain medical words used above. A definition is not evidence that another condition is present, and it does not predict how a symptom will develop. Ask the clinician which terms apply to the actual examination or test result.

Atrial fibrillation

An atrial arrhythmia characterized by disorganized atrial activity without discrete P waves on the surface EKG, but instead by an undulating baseline or more sharply circumscribed atrial deflections of varying amplitude an frequency ranging from 350 to 600 per minute.

Sick sinus syndrome

An abnormality involving the generation of the action potential by the sinus node and is characterized by an atrial rate inappropriate for physiological requirements. Manifestations include severe sinus bradycardia, sinus pauses or arrest, sinus node exit block, chronic atrial tachyarrhythmias, alternating periods of atrial bradyarrhythmias and tachyarrhythmias, and inappropriate responses of heart rate during exercise or stress.

Palpitations

A sensation that the heart is pounding or racing, which is a non-specific sign but may be a manifestation of arrhythmia.

Bradycardia

A slower than normal heart rate (in adults, slower than 60 beats per minute).

Tachycardia

A rapid heartrate that exceeds the range of the normal resting heartrate for age.

Inheritance in the source

From: MedlinePlus Genetics, National Library of Medicine

Autosomal recessive; Autosomal dominant

Which doctor should you see?

The suggested department for discussing Sick sinus syndrome is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Sick sinus syndrome. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.