Electrocardiographic Manifestations of SA Node Dysfunction

What is defined as a rhythm driven by the SA node with a rate of less than 60 beats/min?

Which type of block results from intermittent failure of impulses originating in the sinus node to conduct to the atrial tissue?

What is the characteristic ECG finding in complete or third-degree SA block?

Which condition is characterized by alternating sinus bradycardia and atrial tachyarrhythmias?

What typically characterizes sinus pauses and sinus arrest?

What is the name of the condition where an individual has an inability to increase heart rate in response to exercise?

What is the maximum duration of sinus pauses that may commonly occur in awake athletes?

In type II second-degree SA block, what is the notable change in SA node conduction prior to the pause?

Electrocardiographic Manifestations of SA Node Dysfunction

Sinus bradycardia, sinus pauses, sinus arrest, sinus exit block, tachycardia, and chronotropic incompetence are ECG manifestations of SA node dysfunction.
Sinus bradycardia is defined as a heart rate less than 60 beats per minute, driven by the SA node.
Sinus bradycardia is common, especially in young healthy individuals and athletes.
A rate of less than 40 beats per minute in a non-athlete is considered abnormal.
Sinus pauses and sinus arrest occur when the SA node fails to discharge, resulting in a pause without P waves on the ECG.
Sinus pauses up to 3 seconds are common in athletes, and longer pauses may be observed in asymptomatic elderly individuals.
Sinus exit block occurs when there's an intermittent failure of conduction from the SA node.
Second-degree SA block, a type of sinus exit block, causes intermittent conduction from the SA node, resulting in a regularly irregular atrial rhythm.
Type I second-degree SA block is characterized by progressive prolongation of SA node conduction, leading to intermittent failure of impulse conduction to the surrounding atrial tissue.
In Type II second-degree SA block, there's no change in SA node conduction before the pause.
Complete or third-degree SA block causes no P waves.
Tachycardia-bradycardia syndrome alternates sinus bradycardia with atrial tachyarrhythmias, atrial fibrillation being the most common.
Chronotropic incompetence is the inability to increase heart rate appropriately in response to exercise or stress.

Second-Degree SA Block

Type I second-degree SA block appears as an intermittent absence of P waves on the ECG.
Type II second-degree SA block shows no change in SA node conduction before the pause.

This quiz covers the various ECG manifestations associated with SA node dysfunction, including concepts like sinus bradycardia, sinus pauses, and sinus exit block. It examines the definitions, typical occurrences, and distinctions between the different types of sinus dysfunction. Test your knowledge on these important cardiac rhythm abnormalities!