Genesis and the Risk Score of Atrial Fibrillation for Personalized Management
Article ID: CJ-17-0871
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Article ID: CJ-17-0871
In general, atrial fibrillation (AF) is one of the most frequent clinical arrhythmias, and is a risk factor for cardiovascular disease, especially cardiogenic cerebral infarctions, peripheral embolisms, heart failure, and all-cause death.1 Further, it was recently noted that AF is related to sudden cardiac death2,3 and to cognitive impairment or dementia.4 Subclinical (silent) strokes occur 5-fold more often than clinical (obvious) strokes and may affect thinking, the mood, and personality. All major dementias have a vascular component, including 80% in Alzheimer disease. The integration of stroke and dementia prevention strategies is important because preventing strokes may prevent some dementias.5 The prevention of AF is an important clinical agenda for the extension of a healthy life expectancy because doing so may reduce cardiovascular diseases, including strokes and dementia, and improve or continue the quality of life.
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The mechanism of the occurrence of AF is diverse and there are mutual relationships among the risk factors of AF. Further, we cannot simply talk about the prominent risk factors of AF, because the factors leading to AF differ greatly depending on the person. We need to base the risk factors on the pathophysiological type of AF to ensure personalized management of AF in the future.6 However, while the relationship of the mechanism of AF genesis and AF pathology remains unclear, many studies have added to our understanding of how, and in whom, AF may develop.
Recent genetic studies7 still need to be connected in a better manner with the management of patients with AF. At present, we cannot yet repair genetic abnormalities. Furthermore, the simple question rises, is it effective for the prevention of AF to reduce or improve the risk factors of the onset of AF?
A large-scale clinical trial reported that new-onset AF was reduced by sufficient control of hypertension.8 Obesity is a risk factor for AF, which in turn is associated with strokes, heart failure, and an increased all-cause mortality rate. Prospective cohort studies have observed a 4–5% increased risk of an incident of AF per unit increase in the body mass index,9 and mechanisms including diastolic dysfunction,9 pericardial fat,10 and inflammation11 have been evoked to explain this link. However, it is unclear whether weight loss may reduce the risk of new-onset AF. Weight loss through bariatric surgery reduces the risk of AF among persons being treated for severe obesity,12 and the risk reduction is more apparent in younger people and in those with higher blood pressure.
AF following an alcohol binge, or “holiday heart syndrome”, is well characterized.13 Alcohol may act as a trigger for AF because acute alcohol consumption has direct cellular effects on atrial myocytes and influences autonomic function, forming an electrophysiological milieu for the onset and maintenance of AF and facilitating progressive atrial remodeling with regular long-term consumption.13
Pathak et al14 evaluated the effect of risk factors and weight management on AF ablation outcomes. After AF ablation, all 61 patients were assigned as the risk factor management (RFM) group, including blood pressure control, weight and lipid management, glycemic control, sleep-disordered breathing management, smoking cessation, and alcohol reduction. During the follow-up, AF frequency, duration, symptoms, and symptom severity decreased more in the RFM group than in the control group (all P<0.001). In the multivariate analysis, the type of AF (P<0.001) and RFM (hazard ratio 4.8 [95% confidence interval: 2.04–11.4]; P<0.001) were independent predictors of arrhythmia-free survival. Therefore, aggressive RFM improved the long-term success of AF ablation. In other words, reducing risk factors after AF occurs is not too late to prevent the onset of AF.
This evidence may support the importance of knowing the real risks for the onset of AF in the Japanese general population. It is known that Asians have a high prevalence of hypertension and strokes, and a low prevalence of coronary artery disease, obesity, and AF as compared with Westerners. Therefore, an AF risk score for Asians is necessary in order to realize these characteristics in Asia. In this issue of the Journal the research presented by Kokubo et al15 was an ambitious study to score the risk for AF in Japan for the first time. Of course, this study has several limitations as the authors mention. Mainly, it was difficult to determine all occurrences of AF in the general population, even though they examined the incidence of AF from not only standard ECGs but from routine check-up examinations every 2-year and/or the presence of illness. However, their methods for detecting AF were reasonable and as precise as possible for detecting paroxysmal AF in the clinical setting even in those without symptoms. They did not include subjects over 80 years old in the cohort, because it was difficult to follow them up and they were complicated by various diseases and treatments. However, we should recognize that age is a strong risk factor of not only AF but also strokes. They did not examine other risk factors of the onset of AF, such as heart failure, obstructive sleep apnea, thyroid disease, family history of arrhythmias, sudden cardiac death, or cardiovascular disease, or any other biomarkers at baseline.
Finally, according to their study, the basic risks of AF in the Japanese general population are age, male sex, hypertension, obesity, glucose intolerance, excessive drinking, smoking, coronary artery disease, cardiac murmur, and arrhythmias other than AF. The scoring of the prediction of AF in Japanese patients has just begun. The effect of this research will be increased by examining how much the actual treatment of these causes actually suppresses the occurrence of AF, and the value of scoring for personalized management of AF needs to be verified. We can expect further development of this study.
