This study investigated whether first-degree atrioventricular block, which is delay in the electrical conduction in a heartbeat, increase the risks of developing irregular heartbeat conditions and heart failure among patients with high blood pressure. 

The heart consists of 4 chambers – two atria and two ventricles. These chambers contract in sequence to produce a heart beat that pumps blood around the body. The chambers contract when nerves around the heart are activated and conduct electrical sigals. Impairment of the electrical conduction between the heart chambers can occur such as with an atrioventricular block (AVB).

An AVB refers to when the electrical conduction from the atria to the ventricles is delayed (first-degree ABV) or stopped (advanced ABV). A first-degree ABV does not cause any symptoms. A first-degree AVB is often seen in patients with high blood pressure. High blood pressure is a condition where the pressure inside blood vessels is too high and can cause irregular heart beats. An irregular heartbeat can lead to chest pain, blood clots, a heart attack and stroke. However it is not known whether a first-degree ABV in high blood pressure patients results in irregular heart beats.

An AVB can be measured using an electrocardiogram that measures when the nerves around the atria and ventricles become activated to contract the chamber. When the atrial nerves become activated it is known as the P wave and when the ventricles become activated it is known as the R wave. The duration between the P and R wave is normally between 120 and 200 ms. When the electrical conduction is delayed, like in a first-degree AVB, and the duration between the P and R wave is >200ms.

A total of 3,816 patients with high blood pressure were included in this study. P-R wave interval times were measured. The patients were split into two groups: normal PR interval (between 120ms and 200ms) and first-degree AVB (>200ms). Irregular heat beat conditions such as advanced ABV, and atrial fibrillation, as well as left ventricular dysfunction (a type of heart failure) were measured in both groups for an average of 9 years. 

The study found that patients with high blood pressure and who had first-degree AVB had a higher incidence of irregular heartbeat conditions and heart failure, compared to those with high blood pressure but with normal P-R intervals. Patients with first-degree AVB were nearly 3 times as likely to develop advanced AVB, twice as likely to develop atrial fibrillation, and had a 50% increased risk of developing heart failure.

First-degree AVB in patients with high blood pressure increases the risk of developing irregular heart beat conditions and heart failure. 

This type of study collected data from past hospital records which introduces the possibility of there being selection bias for choosing patients and may not accurately reflect real-time life incidences. 

If you or someone you know have high blood pressure, consider talking to a doctor about testing to see if you have atrioventricular block in order to receive accurate treatment and avoid irregular heartbeat complications.