First Degree AV Block
In the literature, there is now overwhelming evidence that first-degree AV block is not an entirely benign condition. Instead, the more interesting question seems to be whether a prolonged PR interval primarily identifies high-risk patients or if the prolonged PR interval is a part of the problem per se (e.g., via delayed ventricular activation) - Fredrik Holmqvist MD
image by: HWN
HWN Suggests
Marked First Degree AV Block
First-degree atrioventricular (AV) block is defined as an abnormally prolonged PR-interval >200ms. Although traditionally considered to be a benign clinical entity, not all first degree AV blocks are treated the same. Markedly prolonged PR-intervals (PR >300ms) can cause symptoms and hemodynamic compromise due to inadequate timing of atrial and ventricular contractions. Current ACC/AHA guidelines state that permanent pacemaker implantation is reasonable for marked first degree AV block with hemodynamic compromise or symptoms similar to those of pacemaker syndrome. (Class IIa, Level of Evidence B). The guidelines caution that pacemakers are not indicated in asymptomatic patients with isolated…
Articles of Interest
First Degree Heart Block
There is delay, without interruption, in conduction from atria to ventricles. ‘Marked’ first degree heart block is present if PR interval > 300ms.
First-degree atrioventricular block: risk marker or innocent finding?
First-degree atrioventricular (AV) block is a relatively common electrocardiographic finding, defined as PR interval >200 ms. Traditionally, isolated first-degree AV block or PR prolongation had been considered as a benign phenomenon, but this perception has been challenged by a report from the Framingham Heart Study, suggesting that first-degree AV block was associated with increased risk of atrial fibrillation, pacemaker implantation and all-cause mortality in this population.
First-Degree AV Block—An Entirely Benign Finding or a Potentially Curable Cause of Cardiac Disease?
Up until recently, first-degree AV block was considered an entirely benign condition. In fact, some complain that it is a misnomer since there is only delay and no actual block in the AV conduction system (usually within the AV node). However, it has long been acknowledged that extreme forms of first-degree AV block (typically a PR interval exceeding 0.30 s) can cause symptoms due to inadequate timing of atrial and ventricular contractions, similar to the so-called pacemaker syndrome.
Identifying and Treating First-Degree AV Block (First-Degree Heart Block)
Patients with a first-degree AV block are almost always asymptomatic. Often, this rhythm is found incidentally on an ECG, as patients may be unaware of this rhythm disturbance. For most patients with a first-degree AV block, this rhythm does not require treatment.
Resources
StatPearls
First-degree atrioventricular (AV) block is a condition of abnormally slow conduction through the AV node. It is defined by ECG changes that include a PR interval of greater than 0.20 without disruption of atrial to ventricular conduction. This condition is generally asymptomatic and discovered only on routine ECG.
