LONDON.- Researchers from the School of Biomedical Engineering & Imaging Sciences and University di Pisa, have for the first time, from genetic data, revealed that high blood pressure is a risk factor for the most common heart rhythm disorder, atrial fibrillation, and importantly confirms the hypothesis that it is preventable.

Published in the European Journal of Preventive Cardiology the study used genetic information in the analyses to minimise the likelihood of reverse causality, showing that increased blood pressure causes atrial fibrillation and that this association is not dependent on other traits commonly associated to atrial fibrillation (confounders), including coronary artery disease and obesity.

Lead author Dr Georgios Georgiopoulos, clinical research fellow in MRI at the School of Biomedical Engineering & Imaging Sciences and National and Kapodistrian University of Athens, Greece said the results provide strong evidence of a causal relationship between blood pressure and atrial fibrillation.

"The results presented in the paper indicate that strict blood pressure control could be an effective strategy to reduce the risk of developing atrial fibrillation," he said.

"This might have a substantial impact on public health, considering the debilitating diseases commonly associated with the development of atrial fibrillation, which include stroke, heart failure, dementia, and depression." – Dr Georgiopoulos, clinical research fellow in MRI at the School of Biomedical Engineering & Imaging Sciences

Dr Georgiopoulos said establishing that elevated blood pressure causes atrial fibrillation provides further impetus for public health strategies aimed at improving blood pressure control in the general population and for individual efforts to keep levels in check.

Atrial fibrillation is the most common heart rhythm disorder, affecting more than 40 million individuals globally. People with the disorder have a five times greater risk of having a stroke.

The researchers said while several observational studies have shown a strong relationship between blood pressure and the risk of atrial fibrillation, the design of these studies might be susceptible to systematic biases and cannot support a causal association between exposure (elevated blood pressure) and the outcome (the risk of atrial fibrillation).

"Our study, in turn, uses genetic information to overcome most limitations of previous studies and to increase the confidence by which causality can be inferred from data collected in large population-based studies,"Dr Georgopoulos said.




"In a further subanalysis reported in the manuscript, we also show that the association between blood pressure and risk of atrial fibrillation is not driven by other conditions commonly associated to both diseases, including coronary artery disease and obesity."

To investigate whether blood pressure has a direct impact on the risk of atrial fibrillation, the researchers conducted a naturally randomised controlled trial – called Mendelian randomisation.

They used data from the largest genome-wide association study (GWAS) on blood pressure and atrial fibrillation which included more than one million individuals of European ancestry – of which 60,620 had atrial fibrillation and 970,216 did not.

The first step was to identify 894 genetic variants associated with blood pressure. Next, the researchers analysed which of those variants play a role in atrial fibrillation. To conduct the naturally randomised controlled trial, the 894 genetic variants were randomly allocated to all participants at conception, giving each individual a blood pressure level. The investigators then analysed the association between blood pressure and atrial fibrillation.

Elevated blood pressure was associated with an increased risk of atrial fibrillation. Specifically, 1 mmHg rises in systolic blood pressure, diastolic blood pressure and pulse pressure were associated with 1.8%, 2.6% and 1.4% relative increases in the risk of atrial fibrillation, respectively.

Joint senior author Dr Stefano Masi, Associate Professor at University di Pisa said through his work at a hypertension clinic, there are many patients experiencing complications related to long-term exposure to high blood pressure values.

Among these, atrial fibrillation is a very common finding and represents a burdensome disease associated with a reduced quality of life and worsened outcome.

"An important question that remained unaddressed in daily clinical practice was whether the coexistence of both diseases in the same patient represents a simple manifestation of ageing, or the prolonged exposure to high blood pressure values could genuinely increase the risk of developing atrial fibrillation, independently of the age of the subject." – Dr Stefano Masi, Associate Professor at University di Pisa

"From a clinical perspective, this critical question had to be addressed to improve the management of hypertensive patients."

"By showing that arterial hypertension is on the causal pathway for atrial fibrillation, our study's results open the opportunity to develop more effective prevention strategies aimed to improve blood pressure control at the population level."

"This has the potential to reduce the incidence of atrial fibrillation, enhancing the quality of life and prognosis of people with arterial hypertension while reducing healthcare systems' economic costs related to the management and complications of atrial fibrillation."