Sunday, July 28, 2013

Blood Pressure and Atrial Fibrillation

An epidemiological study shows that pulse pressure is an important risk factor for atrial fibrillation – a 20 mm Hg increase in pulse pressure was associated with a 24% increase in the risk for developing atrial fibrillation.
Atrial fibrillation (previously called auricular fibrillation) is what cardiologists once described as an “irregular irregularity” of the heartbeat – in other words, the perceived rhythm from the ventricles is rapid but totally irregular. There are about 2½ million people in the USA with atrial fibrillation; it’s more common in old age, along with higher systolic pressure, diabetes, obesity, and conditions affecting the left heart ventricle.
As people age, the likelihood of increased pulse pressure also rises. This is attributed to age-related increase in aortic stiffness. It’s been suggested that the subsequent increased load on the heart’s work may be responsible for an increase in atrial fibrillation.
Data from the Framingham Heart Study were analyzed. Over 5,300 participants aged 35 and older and free of atrial fibrillation provided the necessary information. Their average age was 57, with 55% of them women and 45% men.
Medical history, physical exam, and electrocardiography were done at baseline. Subsequent diagnosis of atrial fibrillation was based on electrocardiograms from a hospital or physical exam, or done at one of the routine 2-4 yearly Framingham clinic exams.
Statistical analyses sought an association between pulse pressure and newly-developed atrial fibrillation, the relationships between atrial fibrillation and other blood pressure components, and whether the relationship with pulse pressure was influenced by changes in the left ventricular structure and function.
At baseline the average pulse pressures in the whole collective were 51 mm Hg in the men and 53 mm Hg in the women. As expected, individual pulse pressure was linked closely to the systolic pressure, and only weakly to the diastolic pressure.
During the follow-up period, which averaged 16 years, there were 363 new cases of atrial fibrillation in the men, and 335 in the women. The probability of developing atrial fibrillation over time increased with increasing pulse pressure; thus the incidence was 5.6% for people with pulse pressures of 40 mm Hg or less, and 23.3% for those with pressures above 70 mm Hg.
After adjusting for age, sex, body mass index (BMI), smoking, diabetes, and heart disease, a 20 mm Hg increase in pulse pressure was found to be associated with a 24% increase in the risk for developing atrial fibrillation.
Adding left ventricle structure and function factors (obtained from the electrocardiogram) to the analysis failed to alter the association, showing that elevated pulse pressure (representing arterial stiffness) remains a modifiable risk factor for atrial fibrillation; it cannot be explained fully by left ventricle enlargement.
This study shows that pulse pressure is the single blood pressure component most predictive of future atrial fibrillation. This association remains after adjustment for age, diabetes, obesity, left ventricle enlargement, and smoking. This means that older people must check their pulse pressure, and not concentrate exclusively on systolic or even diastolic pressures. The good news is that it’s possible to reduce aortic and arterial stiffness, as shown in a smoking/non-smoking study. With values over 40 mm Hg, initial steps should be lifestyle modifications – those that address high blood pressure, chiefly – followed by antihypertensive medication, if necessary. Atrial fibrillation is to be avoided, if possible.

Blood Pressure and Atrial Fibrillation -

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