Risk Factors Associated With Atrioventricular Block

Atrioventricular (AV) block is a common heart conduction abnormality caused by the disruption where the electrical impulse generated in the atria or ventricles fails to reach and depolarize the respective AV node, bundle of His, or Purkinje fibers. In clinical settings, different definitions of AV blocks have been proposed and used to describe different degrees of delay in conduction through the AV node. The use of AV block is strongly associated with mortality, particularly in high-risk populations as elderly men with cardiovascular risk factors, especially if there is evidence of left bundle branch block pattern.

Third Degree Atrioventricular Block (AVB) is a type of complete heart block, occurring when the electrical impulse from the sinoatrial node cannot pass through the atrioventricular node (AVN) to reach the ventricle.

AV block is a complex electrocardiographic (ECG) pattern of bradycardia caused by conduction delay between the atria and ventricles. It is associated with increased mortality and major adverse cardiovascular events. This study analyzed patients with AV block in routine health check-up by 12-lead ECG during 2018 in public health centers in Korea and includes 5,725,819 participants aged ≥18 years)

Due to the low prevalence of all 3 types of AV block a random sample of 52 880 men and 58 577 women was drawn, resulting in an overall response rate of 63% (n = 35 948). Of these, 36 785 men and 44 341 women were free of cardiovascular disease at baseline. In total, 21.9% (n = 8149) of all participants had first-degree AV block, 6.3% (n = 2582) had second-degree AV block and 3.3% (n = 1470) had third-degree AV block on admission EKG .

This study presents the estimated prevalence of atrial fibrillation (AF) and its four grade in Chinese adults by using data from the China Kadoorie Biobank. The overall prevalence rates were estimated to be 7.6% for 12,553,735 participants without AF, 6.4% for 2646,088 with first-degree AV block (1D AVB), 0.2% for 1498,080 with second-degree AV block (2D AVB) and 0% for 578 participants with third-degree AV block (3D AVB).

It is likely that modifiable risk factors for AF also increase the risk of atrioventricular block (AV block), but no study has so far investigated this association in a contemporary population.

AV block was more common in middle-aged and older adults. The prevalence of AV block was higher among the middle-aged, male, and those with a family history of AV block or diagnosed with cardiovascular disease and diabetes mellitus (CMV).  The risk of AV block was associated with age ≥ 55 years, being male and having had suffered from diabetes mellitus and alcohol abuse.

First-degree, also termed paroxysmal, is a transient inability of the myocardium to conduct electrical impulses, caused by intermittent functional blockage of impulse transmission across the AV junction. The second, or type I, AV block can be further subdivided into three subtypes: Mobitz Type I (Wenckebach), Mobitz Type II and accelerated idioventricular rhythm.

First-degree, type-I second-degree, and type-II second-degree AV block are types of atrioventricular block (AV block), a slow heart rate due to a delay in transmission between the atria and ventricles. Prolongation of the PR interval is another electrocardiograph feature of the first-degree and type-I second-degree AV block.

Moreover, prolongation of the PR interval is a feature of type II second-degree and third degree AV block as well. The prognosis of these three types of AV block are not similar and therefore require appropriate treatment such as medication or pacemaker implantation. If they are not treated timely or adequately, AV block might lead to death

Alternating (first-degree) atrioventricular block (AVB) has been found to be associated with multiple CVDs including coronary heart disease, heart failure, stroke and hypertension. However, prevalence of first-degree AVB remains largely unexplored in Chinese population. Thus, this study was to investigate the prevalence of first-degree AVB among apparently healthy general population with focus on the impact of gender, age, height and weight.

While the overall prevalence of second-degree (Mobitz type I) and third-degree atrioventricular (AV) block (Mobitz type II and III) was 23.8% and 3.2%, respectively, in our study population, isolated second-degree AV block was far more common than isolated first- or third-degree AV block. The prevalence of first-, second-, and third-degree AV block increased from 13.9% to 36.5%, 4.5% to 12.7%, and 0–4.0% with increasing age groups, respectively (p for trend <0.0001).

A 12-lead ECG is an important tool for diagnosis and management of coronary heart disease, which could be affected by various risk factors. However, no large study has been conducted to explore the prevalence of different degree of atrioventricular block and its related risk factors in China. Therefore, using the dataset from the 1,398 th province-level administrative center in China, we retrospectively analysed the prevalence of first-, second-, and third-degree AV block and explored related risk factors.