In addition, the sinus rate was 80 bpm -normal heart rhythm-, which also confirmed that the increased vagal tone was not the etiology of the AV block.
Atrioventricular (AV) block is a partial or complete interruption of the transmission of impulses from the atria to the ventricles. Photo: Shutterstock.
Atrioventricular (AV) block is defined as the delay in the conduction of electrical impulses as they move through the heart’s atrioventricular conduction system.
VA is classified as: first degree, when electrical conduction to the ventricles is delayed; second degree, when electrical conduction is intermittently blocked; and third degree or complete, when electrical conduction is completely blocked.
Precisely high-endurance athletes can often present sinus bradycardia – a slower than normal heart rate that usually begins in the area of the heart called the sinus node – secondary to increased vagal tone, which is defined as the inhibitory control exerted by the nerve vagus on heart rhythm and atrioventricular conduction.
However, according to a clinical case recorded in Puerto Rico, different degrees of VA can also occur in this population, which does not result from increased vagal tone and often suggests an underlying pathology.
Precisely advanced AV block has been related to lower long-term survival when not treated on time. Sometimes, the decision to recommend pacemaker implantation in athletes can be challenging, as doctors point out, in the case they handled in a 62-year-old man.
The patient presented asymptomatic and without systemic disease and was referred for evaluation after incidentally finding complete AV block.
The man is a marathon runner and usually runs 8 miles a day without difficulty. On evaluation, he denied chest pain, shortness of breath, dizziness, or other symptoms. He was not taking medication and his physical examination was normal, except for marked bradycardia.
The patient underwent a 12-lead electrocardiogram that showed sinus rhythm with complete AV block and ventricular escape rhythm at 32 bpm. After walking for 6 minutes, the AV block persisted, but the patient reported no symptoms. Laboratory results were normal.
The doctors maintain that even though the patient was asymptomatic, they made the decision to proceed with the implantation of a pacemaker.
Upon evaluating the patient again, a ventricular escape rhythm was found with less than 40 bpm -still indicative of bradycardia-, indicative of a blockage of the His-Purkinje system -structures that conduct the electrical impulse to the rest of the muscle cells at high speed of the ventricle-, which could not be attributed to an increase in vagal tone.
In addition, the sinus rate was 80 bpm -normal heart rhythm-, which also confirmed that the increased vagal tone was not the etiology of the AV block.
In conclusion, doctors maintain that there are very few reported cases like this and that the decision to implant a pacemaker in this situation must consider the symptoms, physiology and the place where the heart block originates in the patient.
Access the case here.