Association Between Circadian Blood Pressure Patterns With Asymptomatic Episodes of Paroxysmal Atrial Fibrillation in Hypertensive Subjects

Atrial fibrillation, also known as AF or Afib, is an abnormal and irregular heart rhythm in which electrical signals are generated chaotically throughout the upper chambers (atria) of the heart. According to the NICE clinical guidelines, a patient who experiences recurrent (two or more) AF episodes that terminate spontaneously without any treatment in less than seven days, and usually within 48 hours is classified as having paroxysmal AF. It has been shown that paroxysmal AF comprises approximately between 25% and 62% of cases of AF, and it is estimated that both its incidence and prevalence are likely to rise as the worldwide population ages dramatically over the next twenty years. Interestingly, hospitalizations due to AF have increased sharply in the US during the last decade, posing thereby a heavy economic burden on the health care system and society.

Likewise, hypertension (HTN) also constitutes a major public health problem globally, and its prevalence is set to increase owing to widespread population ageing. This epidemiological trend is especially prevalent in rapidly developing countries where early routine screening at any point of health care is underutilized among risk subjects, due to several perceived barriers. Moreover, HTN awareness is critical for optimal BP control since under-diagnosis, under-treatment and/or un-treatment of high BP levels can have deleterious effects on the cardiovascular system. In addition, HTN is the single most important risk factor for cerebrovascular stroke, and it has been clearly demonstrated that it is also associated with structural and functional changes in the myocardium that favor the development of AF, further increasing the risk of thromboembolism. Among those alterations, left ventricular hypertrophy (LVH), impaired ventricular filling, left atrial enlargement and slowing of atrial conduction velocity have been identified as important heralds of cardiovascular morbidity and mortality. More specifically, since HTN and AF are two conditions that often co-exist, especially in patients with advanced age, the risk for considerable morbidity and mortality is increased even more, which points towards the significance that optimal BP control holds in the prevention of cardiovascular events. To our knowledge, in the Framingham Heart Study, after controlling for age and other predisposing conditions, HTN and diabetes emerged as the only cardiovascular risk factors predicting AF.

It has also been suggested that nocturnal HTN and non-dipping of BP during sleep are distinct entities that often occur together and are regarded as important harbingers of poor cardiovascular prognosis. Recently, Pierdomenico et al., showed that non-dipper sustained hypertensives have a two-fold greater risk of developing AF than dipper ones. This may be due to the fact that nighttime HTN may be a powerful determinant of long-standing left ventricular diastolic dysfunction, which subsequently increases atrial stretch. Furthermore, it has been observed that nighttime hemodynamics, are associated with higher sympathetic and reduced vagal activity, which may trigger AF. Additionally, sympathetic activation is associated with the stimulation of the renin-angiotensin-aldosterone axis (RAAA), which leads to increased left ventricular diastolic preload, both atrial and ventricular fibrosis, exerting thus direct cellular electrophysiological effects. Besides, scientists suggested that nighttime HTN is better associated with cardiovascular target organ damage (TOD) as compared with the non-dipping pattern.

According to the most recent guidelines of the ESH, the presence of microalbuminuria, increased pulse wave velocity, LVH on echocardiogram and carotid plaques detected during carotid ultrasonography, constitute markers of asymptomatic organ damage and it has been clearly demonstrated from multiple studies that they can predict CV mortality independently of SCORE stratification.

In our study we will try to investigate whether abnormalities in the circadian rhythm of BP (such as extreme dipping or non-dipping pattern, and/or morning surge) in hypertensive subjects with or without TOD are associated with the development of new-onset paroxysmal AF.