Influence of age on the incidence of acute complete atrioventricular block in right coronary artery infarction
Authors: Martinez Nunez R , Izquierdo Bajo A , Lopez Flores C , Lucas Garcia M , Garcia Gonzalez N , Hidalgo Urbano R J 
Published: May 2024

Abstract

Funding Acknowledgements
None.

Introduction
Bezold-Jarisch is a cardioinhibitory reflex originating in cardiac vagal receptors, more concentrated in the inferoposterior wall of left ventricle, whose stimulation produces bradycardia and hypotension. The limited evidence suggests that vagal tone would predominate in younger individuals, whereas sympathetic tone would predominate in the elderly, resulting in a more striking Bezold-Jarisch reflex response among younger patients. Its maximum expression would be the occurrence of acute complete atrioventricular block (cAVB).

Methods
Observational, retrospective, single-centre analysis of consecutive patients hospitalised in the CCCU for STEACS with RCA or ADA as culprit artery (CA) between July 2011 and September 2022. We analysed the influence of age on the incidence of acute cAVB. Linear trend analysis and multivariate analysis were performed.

Results
A total of 723 patients with RCA as CA were included, with the baseline characteristics listed in Table1. Patients were divided into 4 groups: under 60 years (n=316 43.7%), 60-69 (n=223 30.8%), 70-79 (n=122 16.9%) and 80 or older (n=62 8.6%). The incidence of acute cAVB was 10.4%, 14.3%, 16.4% and 25.8% respectively (Fig1). A Cochran-Armitage analysis was performed, showing a significant linear trend between age and the incidence of acute cAVB (p=0.001). A multivariate analysis was performed using stepwise regression including age, sex, diabetes, hypertension, obesity, peripheral arterial disease, systolic blood pressure (SBP) at admission, renal failure, COPD, Killip-Kimbal (KK) score at admission and treatment with ticagrelor (for its described adenosine-like effect). Age (p=0.011), KK score (p&lt;0.001) and lower SBP (p&lt;0.001) were associated with a higher incidence of acute cAVB. Regarding the need for transient pacemaker, 6.2% of patients under 60, 7.7% aged 60-69, 10.1% aged 70-79, and 22.0% aged 80 and over required its implantation. As with cAVB, there was a significant linear trend between age and device implantation (p&lt;0.001). Permanent pacemaker was implanted in only 6 patients. In-hospital mortality was significantly higher in patients with acute cAVB than all other patients with RCA infarction (7.9% vs 2.1%; p=0.001). Finally, as controls, acute cAVB data were analysed in patients with STEACS with ADA as CA (N=837). 366 patients (43.7%) were under 60 years, 204 (24.4%) 60-69, 155 (18.5%) 70-79 and 112 (13.4%) 80 or older. Only 10 patients presented with cAVB (1.2%), with no differences between those younger and older than 75 years (1.0% vs 2.3% respectively; p=0.13). Given the low incidence of cAVB in this group no further analysis was performed.

Conclusion
In RCA STEACS patients, there is a significant trend towards a higher incidence of acute cAVB with increasing age. These data suggest that older patients do not have a mitigated response to Bezold-Jarisch reflex. The inverse relationship between SBP and occurrence of cAVB supports the reflex nature of the mechanism.Table 1.Baseline characteristics.Fig 1.cAVB incidence among age groups.