Complete Heart Block and Third-Degree AV Block: Terminology
Yes, complete heart block is the same as third-degree atrioventricular (AV) block—these terms are used interchangeably to describe the complete absence of atrioventricular conduction. 1
Definition and Terminology
Third-degree AV block is defined as the complete absence of all atrioventricular conduction, where no atrial impulses reach the ventricles 1
The terms "complete heart block," "third-degree AV block," and "complete AV block" all refer to the same condition and are used synonymously in clinical practice 1, 2, 3
This represents complete dissociation between atrial and ventricular activity, with the ventricles being depolarized by an escape rhythm independent of atrial activity 1, 3
Distinguishing Features from Other AV Blocks
Unlike first-degree AV block (where every P wave conducts with prolonged PR interval >200 ms), third-degree block has no conducted P waves 1, 2
Unlike second-degree AV block (where some but not all P waves conduct), third-degree block has zero atrial impulses reaching the ventricles 1, 2
The ventricular rate in complete heart block depends entirely on the location of the escape pacemaker within the conduction system 3
Clinical Significance
Complete heart block is a cardiovascular emergency requiring prompt recognition and treatment 3
The escape rhythm characteristics help determine prognosis: junctional escape (narrow QRS, 40-60 bpm) versus ventricular escape (wide QRS, 20-40 bpm) 3
Symptomatic third-degree AV block is a Class I indication for permanent pacemaker implantation 1, 2
Non-randomized studies demonstrate that permanent pacing improves survival in patients with complete AV block, especially when syncope has occurred 1, 2