First-degree atrioventricular block and very long PR

Tracé
N° 2
Patient
68-year-old man, exertional dyspnea, NYHA IIB (moderate exercise);
First-degree atrioventricular block and very long PR
Commentaires

A significant prolongation of the PR interval due to a relatively fast heart rate can lead to a superposition of the P wave on the preceding T wave which renders interpretation difficult, with a risk of misinterpretation with a junctional rhythm. Variations in heart rate generally allow rectifying the diagnosis by helping in the visualization of the P waves. Generally, prolongation does not exceed 400 ms even though PR interval values exceeding 800 ms have been observed. In extreme cases, the duration of the PR can exceed that of the PP and the P wave responsible for the QRS complex is not the one preceding it on the tracing. The location of the slowing is most often...

Exergue
First-degree AV block most often reflects a delay in atrioventricular node conduction; the longer the PR interval, the greater the likelihood of an intra-nodal slowing; when the PR interval is extremely prolonged, the physiological activation/contraction sequence between atria and ventricles is no longer respected, leading to a contraction of the atria while the mitral valves are closed. A pacemaker may be indicated in this setting if the patient is symptomatic during exercise.
First-degree atrioventricular block and very long PR