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Sick Sinus Syndrome

Sick sinus syndrome, Tachycardia-Bradycardia (Tachy-Brady) syndrome, Sinus node dysfunction, Sinoatrial node disease

Sick Sinus Syndrome and the Conduction System
ECG and Sick Sinus Syndrome
Diagnosis of SSS
Tachy-Brady Syndrome and Overdrive Suppression
SA Node Recovery Time and Post-Tachycardic Pause

Sick Sinus Syndrome and the Conduction System

Heart conduction system, sick sinus syndrome

Sick Sinus Syndrome (SSS)

It translates to sick sinus syndrome (SA node)
It's not just a disorder of the SA node, as the name implies

It is a generalized disorder

primarily of the atrial conduction system
In which the SA node is always affected

Occurs mainly in elderly people due to

Fibrosis of the atrial conduction system
Atherosclerotic stenoses of the atrial arteries

SSS is a combined irreversible disorder

SA node
Atrial myocardium
Part of the conduction system (especially AV junction)

ECG and Sick Sinus Syndrome

In the conduction system and atrial myocardium

All arrhythmias can occur in any combination

SSS most commonly manifests as a combination of arrhythmias:

Supraventricular tachycardia (SVT)

Atrial fibrillation (the most common SVT in SSS)
Atrial flutter

Inadequate sinus bradycardia

The patient has unexplained bradycardia

Does not take bradycardia-inducing medications, is not an athlete...

Chronotropic incompetence (SA node). The patient under stress:

Does not reach tachycardia (rate > 100/min.)
Does not reach 85% of maximum heart rate (220-age)

A 50-year-old should have a maximum heart rate of 170/min. (220-50)
With SSS, the heart rate does not exceed 144/min. (85% of 170 is 144)

SA blocks
SA pauses > 3s

Tachycardia-Bradycardia Syndrome

Occurs in 50% of patients with SSS
Following a run of supraventricular tachycardia

Followed by sinus pauses or bradycardia

Diagnosis of SSS

Diagnosis of SSS is difficult because arrhythmias in SSS can combine randomly and may be:

Persistent
Sporadic

During arrhythmias patients may or may not have subjective difficulties:

Palpitations (heart pounding)
Syncope (loss of consciousness)
Vertigo (dizziness)
Shortness of breath during exertion
Weakness

SSS is most commonly diagnosed using

24-hour ECG Holter monitor
Post-tachycardia pause after atrial pacing

Tachy-Brady Syndrome and Overdrive Suppression

Atrial fibrillation, tachy brady syndrome, sick sinus syndrome

Atrial Fibrillation

Is the most common supraventricular (SVT) arrhythmia in SSS
Impulses originate in the atrial myocardium with a frequency of 350-600/min.
The high frequency of impulses deactivates the SA node (overdrive suppression)

Overdrive suppression

Is an electrophysiological phenomenon
A focus (foci) with the highest frequency

deactivates foci with a lower frequency

Tachy-Brady Syndrome

Affects 50% of patients with SSS
Following SVT, a post-tachycardic pause occurs

Afterwards, it may be followed by another SVT, bradycardia, or sinus rhythm

Bradycardia does not have to follow the pause

Tachy-Brady Syndrome can also have a pattern

where SVT alternates with post-tachycardic pauses

The term Bradycardia-Tachycardia Syndrome is incorrect

Because tachycardia through overdrive suppression

Induces bradycardia (SA pause)
The correct sequence is Tachycardia-Bradycardia

SA Node Recovery Time and Post-Tachycardic Pause

Sinus Node Recovery Time (SNRT)

Is the time it takes for the SA node to resume function after tachycardia (after overdrive suppression)
Most commonly occurs after

When suspecting SSS, an electrode is inserted into the right atrium

which generates tachycardic impulses for 30 seconds (tachycardic atrial pacing)
During pacing, the SA node is suppressed (deactivated) due to overdrive suppression
Then, the atrial pacing is turned off

and a post-tachycardic pause follows

This is the time it takes for the SA node to resume its function

Post-Tachycardic Pause

> 1.5s: indicates sick sinus syndrome (a disorder of the SA node)
< 1.5s: the SA node is intact

ECG sick sinus syndrome, tachy-brady syndrome, Sinus node recovery time (SNRT), long pause after tachycardia

Sick Sinus Syndrome (Tachy-Brady Syndrome)

Initially, there is atrial fibrillation with a rapid ventricular response (ventricular rate 130/min.)

During atrial fibrillation, the atria generate impulses at a rate of 350-600/min.

This leads to overdrive suppression of the SA node (overdrive suppression)

After the spontaneous termination of atrial fibrillation, a post-tachycardic pause follows

During the pause, the secondary pacemaker - junctional rhythm - is not activated

This is because, in this case of SSS, the AV junction is also damaged (AV junction)

After a 4.2s pause, the SA node resumes activity

This is followed by one sinus contraction and then atrial fibrillation resumes

A healthy SA node would resume function within 1.5s after tachycardic overdrive suppression

The patient has Tachy-Brady Syndrome

Characterized by alternating supraventricular tachycardia and abnormal post-tachycardic pauses
50% of patients with SSS present with Tachy-Brady Syndrome

ECG sick sinus syndrome (SSS), abrupt sinus arrest junctional escape beat

Sick Sinus Syndrome

Initially, there is a sinus rhythm

Heart rate: 75/min.

After the spontaneous arrest of the SA node, a 3s sinus pause follows

After the pause, the SA node does not reactivate; instead, the secondary pacemaker - junctional rhythm - takes over

This is a case of SSS manifesting as sinus pauses with junctional rhythm

It is not Tachy-Brady Syndrome

Because the pause did not occur after tachycardia

Sick sinus syndrome (SSS), sinus dysfunction, sinoatrial node disease (SND), Tachycardia-bradycardia syndrome, paroxyzmal atrial fibrillation, 7second sinus pause, overdrive suppression, ventricular asystole

Sick Sinus Syndrome (Tachy-Brady Syndrome)

Initially, there is atrial fibrillation with a rapid ventricular response (ventricular rate 130/min.)

This is not atrial flutter because the heart rate is irregularly irregular

After the spontaneous termination of atrial fibrillation, a post-tachycardic pause (7s) follows

After the pause, the SA node does not reactivate, but atrial fibrillation resumes

The patient has Tachy-Brady Syndrome

There is an alternation between supraventricular tachycardia and abnormal post-tachycardic pauses
50% of patients with SSS manifest as Tachy-Brady Syndrome

ECG sick sinus syndorme (SSS), atrial fibrillation, prolonged sinus arrest, atrial premature complex - beat

Sick Sinus Syndrome (Tachy-Brady Syndrome)

Initially, there is atrial fibrillation with a rapid ventricular response (ventricular rate 110/min.)
After the spontaneous termination of atrial fibrillation, a post-tachycardic pause (5s) follows

After the pause, the SA node does not reactivate, but numerous atrial extrasystoles occur

The patient has Tachy-Brady Syndrome

There is an alternation between supraventricular tachycardia, post-tachycardic pauses, and extrasystoles
50% of patients with SSS manifest as Tachy-Brady Syndrome

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers

Sick Sinus Syndrome

Sick sinus syndrome, Tachycardia-Bradycardia (Tachy-Brady) syndrome, Sinus node dysfunction, Sinoatrial node disease

Sick Sinus Syndrome and the Conduction System
ECG and Sick Sinus Syndrome
Diagnosis of SSS
Tachy-Brady Syndrome and Overdrive Suppression
SA Node Recovery Time and Post-Tachycardic Pause

Sick Sinus Syndrome and the Conduction System

Sick Sinus Syndrome (SSS)

It translates to sick sinus syndrome (SA node)
It's not just a disorder of the SA node, as the name implies

It is a generalized disorder

primarily of the atrial conduction system
In which the SA node is always affected

Occurs mainly in elderly people due to

Fibrosis of the atrial conduction system
Atherosclerotic stenoses of the atrial arteries

SSS is a combined irreversible disorder

SA node
Atrial myocardium
Part of the conduction system (especially AV junction)

Heart conduction system, sick sinus syndrome

ECG and Sick Sinus Syndrome

In the conduction system and atrial myocardium

All arrhythmias can occur in any combination

SSS most commonly manifests as a combination of arrhythmias:

Supraventricular tachycardia (SVT)

Atrial fibrillation (the most common SVT in SSS)
Atrial flutter

Inadequate sinus bradycardia

The patient has unexplained bradycardia

Does not take bradycardia-inducing medications, is not an athlete...

Chronotropic incompetence (SA node). The patient under stress:

Does not reach tachycardia (rate > 100/min.)
Does not reach 85% of maximum heart rate (220-age)

A 50-year-old should have a maximum heart rate of 170/min. (220-50)
With SSS, the heart rate does not exceed 144/min. (85% of 170 is 144)

SA blocks
SA pauses > 3s

Tachycardia-Bradycardia Syndrome

Occurs in 50% of patients with SSS
Following a run of supraventricular tachycardia

Followed by sinus pauses or bradycardia

Diagnosis of SSS

Diagnosis of SSS is difficult because arrhythmias in SSS can combine randomly and may be:

Persistent
Sporadic

During arrhythmias patients may or may not have subjective difficulties:

Palpitations (heart pounding)
Syncope (loss of consciousness)
Vertigo (dizziness)
Shortness of breath during exertion
Weakness

SSS is most commonly diagnosed using

24-hour ECG Holter monitor
Post-tachycardia pause after atrial pacing

Tachy-Brady Syndrome and Overdrive Suppression

Atrial Fibrillation

Is the most common supraventricular (SVT) arrhythmia in SSS
Impulses originate in the atrial myocardium with a frequency of 350-600/min.
The high frequency of impulses deactivates the SA node (overdrive suppression)

Overdrive suppression

Is an electrophysiological phenomenon
A focus (foci) with the highest frequency

deactivates foci with a lower frequency

Tachy-Brady Syndrome

Affects 50% of patients with SSS
Following SVT, a post-tachycardic pause occurs

Afterwards, it may be followed by another SVT, bradycardia, or sinus rhythm

Bradycardia does not have to follow the pause

Tachy-Brady Syndrome can also have a pattern

where SVT alternates with post-tachycardic pauses

The term Bradycardia-Tachycardia Syndrome is incorrect

Because tachycardia through overdrive suppression

Induces bradycardia (SA pause)
The correct sequence is Tachycardia-Bradycardia

Atrial fibrillation, tachy brady syndrome, sick sinus syndrome

SA Node Recovery Time and Post-Tachycardic Pause

Sinus Node Recovery Time (SNRT)

Is the time it takes for the SA node to resume function after tachycardia (after overdrive suppression)
Most commonly occurs after

When suspecting SSS, an electrode is inserted into the right atrium

which generates tachycardic impulses for 30 seconds (tachycardic atrial pacing)
During pacing, the SA node is suppressed (deactivated) due to overdrive suppression
Then, the atrial pacing is turned off

and a post-tachycardic pause follows

This is the time it takes for the SA node to resume its function

Post-Tachycardic Pause

> 1.5s: indicates sick sinus syndrome (a disorder of the SA node)
< 1.5s: the SA node is intact

ECG sick sinus syndrome, tachy-brady syndrome, Sinus node recovery time (SNRT), long pause after tachycardia

Sick Sinus Syndrome (Tachy-Brady Syndrome)

Initially, there is atrial fibrillation with a rapid ventricular response (ventricular rate 130/min.)

During atrial fibrillation, the atria generate impulses at a rate of 350-600/min.

This leads to overdrive suppression of the SA node (overdrive suppression)

After the spontaneous termination of atrial fibrillation, a post-tachycardic pause follows

During the pause, the secondary pacemaker - junctional rhythm - is not activated

This is because, in this case of SSS, the AV junction is also damaged (AV junction)

After a 4.2s pause, the SA node resumes activity

This is followed by one sinus contraction and then atrial fibrillation resumes

A healthy SA node would resume function within 1.5s after tachycardic overdrive suppression

The patient has Tachy-Brady Syndrome

Characterized by alternating supraventricular tachycardia and abnormal post-tachycardic pauses
50% of patients with SSS present with Tachy-Brady Syndrome

ECG sick sinus syndrome (SSS), abrupt sinus arrest junctional escape beat

Sick Sinus Syndrome

Initially, there is a sinus rhythm

Heart rate: 75/min.

After the spontaneous arrest of the SA node, a 3s sinus pause follows

After the pause, the SA node does not reactivate; instead, the secondary pacemaker - junctional rhythm - takes over

This is a case of SSS manifesting as sinus pauses with junctional rhythm

It is not Tachy-Brady Syndrome

Because the pause did not occur after tachycardia

Sick sinus syndrome (SSS), sinus dysfunction, sinoatrial node disease (SND), Tachycardia-bradycardia syndrome, paroxyzmal atrial fibrillation, 7second sinus pause, overdrive suppression, ventricular asystole

Sick Sinus Syndrome (Tachy-Brady Syndrome)

Initially, there is atrial fibrillation with a rapid ventricular response (ventricular rate 130/min.)

This is not atrial flutter because the heart rate is irregularly irregular

After the spontaneous termination of atrial fibrillation, a post-tachycardic pause (7s) follows

After the pause, the SA node does not reactivate, but atrial fibrillation resumes

The patient has Tachy-Brady Syndrome

There is an alternation between supraventricular tachycardia and abnormal post-tachycardic pauses
50% of patients with SSS manifest as Tachy-Brady Syndrome

ECG sick sinus syndorme (SSS), atrial fibrillation, prolonged sinus arrest, atrial premature complex - beat

Sick Sinus Syndrome (Tachy-Brady Syndrome)

Initially, there is atrial fibrillation with a rapid ventricular response (ventricular rate 110/min.)
After the spontaneous termination of atrial fibrillation, a post-tachycardic pause (5s) follows

After the pause, the SA node does not reactivate, but numerous atrial extrasystoles occur

The patient has Tachy-Brady Syndrome

There is an alternation between supraventricular tachycardia, post-tachycardic pauses, and extrasystoles
50% of patients with SSS manifest as Tachy-Brady Syndrome

Sources

ECG from Basics to Essentials Step by Step
litfl.com
ecgwaves.com
metealpaslan.com
medmastery.com
uptodate.com
ecgpedia.org
wikipedia.org
Strong Medicine
Understanding Pacemakers