Cardiac Dysrhythmias Overview

Sinus Bradycardia

• Heart rate (HR) is less than 60 beats per minute.
• Characterized by a normal rhythm and regular P waves.

1st Degree Heart Block

• HR can be normal or slightly slow.
• Regular rhythm is present; PR interval is prolonged (greater than 0.20 seconds).

2nd Degree Heart Block Type I (Wenckebach)

• HR is typically slow.
• Regular rhythm with a PR interval that progressively lengthens until a QRS complex is dropped.

2nd Degree Heart Block Type II

• HR remains slow and has a regular rhythm.
• PR interval may be normal or prolonged; often leads to multiple dropped QRS complexes.

3rd Degree Heart Block (Complete Heart Block)

• HR is slow with a regular rhythm, but no correlation between P waves and QRS complexes.
• P waves are normal; QRS complexes can be either normal or wide.

Junctional Dysrhythmias

• HR can be normal or slow with a regular rhythm.
• P waves are often hidden within the QRS complex due to retrograde conduction.

Atrial Fibrillation

• HR ranges from 350 to 600 beats per minute.
• Irregular rhythm with the presence of fibrillatory waves instead of distinct P waves.

Atrial Flutter

• HR varies between 200 to 350 beats per minute.
• Can be regular or irregular; characterized by "sawtooth" flutter waves.

Supraventricular Tachycardia (SVT)

• HR exceeds 150 beats per minute.
• Presents a regular rhythm with absent or hidden P waves among the rapid beats.

Ventricular Tachycardia (VT)

• HR typically ranges from 150 to 250 beats per minute.
• Regular rhythm with wide and distorted QRS complexes.

Ventricular Fibrillation (VF)

• HR is not measurable due to chaotic electrical activity.
• Irregular rhythm with no discernible waves or measurable parameters.

ST Depression

• Indicative of myocardial ischemia.
• Appears as a downward deflection from the baseline on the ECG.

ST Elevation

• Often signifies acute myocardial infarction (heart attack).
• Appears as an upward deflection from the baseline on the ECG.

Asystole

• Represents a complete lack of electrical activity in the heart.
• HR is absent, and there are no identifiable waves on the ECG.

Artifact

• Refers to distortion or interference on an EKG that does not represent cardiac activity.
• Generally caused by patient movement, poor electrode contact, or external electrical signals.