What is the prognosis of first-degree atrioventricular (AV) block?

Updated: Jan 06, 2020
  • Author: Jamshid Alaeddini, MD, FACC, FHRS; Chief Editor: Jose M Dizon, MD  more...
  • Print

The prognosis for isolated first-degree AV block usually is very good. Progression from isolated first-degree heart block to high-degree block is very uncommon. [13] Patients with first-degree AV block and infranodal blocks, however, are at increased risk for progression to complete AV block.

Heart block in children with Lyme carditis tends to resolve spontaneously, with median recovery in 3 days (range, 1-7 days). [14]

Cheng et al found that first-degree heart block is associated with increased long-term risks of atrial fibrillation, pacemaker implantation, and all-cause mortality. [15] Their community-based cohort included 7575 individuals from the Framingham Heart Study who underwent baseline routine 12-lead ECG in 1968-1974 and were followed prospectively through 2007.

Traditionally, first-degree AV block has been considered a benign condition. However, epidemiologic data from the Framingham Study have shown that first-degree AV block is associated with increased risk of all-cause mortality in the general population. Compared with individuals whose PR intervals were 200 msec or shorter, those with first-degree AV block had a 2-fold adjusted risk of atrial fibrillation, a 3-fold adjusted risk of pacemaker implantation, and a 1.4-fold adjusted risk of all-cause mortality. [15] Each 20-msec increment in PR interval was associated with an adjusted hazard ratio (HR) of 1.11 for atrial fibrillation, 1.22 for pacemaker implantation, and 1.08 for all-cause mortality. [16]

A study by Uhm et al of 3816 patients indicated that in the presence of hypertension, patients with first-degree AV block have a greater risk of developing advanced AV block, atrial fibrillation, and left ventricular dysfunction than do hypertensive patients with a normal PR interval. [17]

Crisel showed that patients with stable coronary artery disease who had a PR of 220 msec or more had a significantly higher risk of reaching the combined end point of heart failure or cardiovascular death over a follow-up of 5 years. [18]

The Korean Heart Failure registry selected 1,986 patients with acute heart failure in sinus rhythm and divided them into four groups, depending on the presence of first-degree AV block and/or QRS prolongation. During the median follow-up of 18.2 months, overall death rate was highest in patients who had both first-degree AV block and prolonged QRS. This group also showed worst outcomes regarding the requirement of invasive managements during the index admission, in-hospital mortality, post discharge death/rehospitalization, and cardiac device implantation. [19]

In an analysis of the COMPANION Trial, 1520 patients fulfilling criteria for cardiac resynchronization therapy (CRT) implant were assigned to normal (PR < 200 msec) or prolonged (PR ≥200 msec) AV delay and cohorts were compared within the optimal pharmacologic therapy and CRT groups regarding an endpoint of all-cause mortality or heart failure hospitalization. CRT was compared with optimal pharmacologic therapy in normal and prolonged PR interval groups. Randomization to CRT was associated with a reduction in the endpoint in all patients; the strength of the association was greater for those with first-degree AV block versus normal PR intervals. This analysis demonstrated that the deleterious effect of first-degree AV block in patients with systolic dysfunction, heart failure, and wide QRS complexes be attenuated by CRT. [20]

More recently, a 2018 subgroup analysis from the INSIGHT XT study that evaluated the outcomes of patients with baseline first-degree AV block who received an insertable cardiac monitor (ICM) found the presence or progression to a higher grade block in 53% of patients or detected an already existing more severe bradycardia that warranted an IPG in 40.5% of patients. [21]  The findings led the investigators to conclude first-degree AV block may be a risk marker for more severe intermittent conduction disease.

These studies suggest that first-degree AV block is not necessarily a benign condition. In patients with chronic systolic heart failure and wide QRS, CRT may attenuate its deleterious effect.

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!