Biomarkers in white-coat hypertension

2017-02-08T01:12:05Z (GMT) by Martin, Catherine Ann
The introduction of ambulatory blood pressure monitoring in the 1960s provided new insights into the nature of high blood pressure disorders. Blood pressure is now categorised into four quadrants:normotension, masked hypertension, hypertension and white-coat hypertension. In white-coat hypertension blood pressure is elevated when taken at the doctor’s office but normal if taken outside the doctor’s office. Several controversies are associated with white-coat hypertension, which are discussed in Chapter 1. Whether white-coat hypertension is a condition of increased cardiovascular risk is the most important current issue. The consensus from prospective studies has been that the cardiovascular risk in white-coat hypertension is similar to normotensives, but recent studies suggest that white-coat hypertension is associated with an increased risk for the development of hypertension, which may mean an increased cardiovascular risk is present but delayed in white-coat hypertension. Examining the literature (Chapter 2)at the time of the thesis commencement highlighted inconsistencies in the definition for white-coat hypertension, which makes it difficult to determine if white-coat hypertension is associated with biomarkers of increased cardiovascular risk. This thesis by publication investigated whether white-coat hypertension is a condition of increased cardiovascular risk by determining: (1) if biomarkers of increased cardiovascular risk that are known to be present in essential hypertension are present in strictly defined white-coat hypertension based on a consensus definition for white-coat hypertension (Chapter 4); (2) if white-coat hypertension is associated with an increased morning blood pressure surge (Chapter 5); (3) if white-coat hypertension is associated with increased risk for the development of new-onset hypertension; and (4) if biomarkers measured at baseline predict the development of sustained hypertension in white-coat hypertension (Chapter 7). Participants underwent measurement of artery stiffness, autonomic function, glucose and insulin status,circulating measures of inflammation and endothelial dysfunction, and twenty-four hour ambulatory blood pressure monitoring to confirm blood pressure status. White-coat hypertension participants required two twenty-four hour ambulatory blood pressure monitorings to confirm blood pressure status. Participants returned yearly for ambulatory blood pressure monitoring for three years. New-onset hypertension was defined based on elevated mean ambulatory blood pressure. This research has identified that white-coat hypertension is associated with markers of increased cardiovascular risk, including an elevated baseline two-hour glucose post glucose load and increased progression to sustained hypertension compared to normotensives. Elevated baseline measures of waist circumference, artery stiffness and two-hour load blood glucose were elevated in white-coat hypertension who progressed to sustained hypertension. White-coat hypertension was not associated with an increased morning blood pressure surge but univariate analysis found lipids were associated with the morning blood pressure surge (Chapter 5), which was confirmed in a larger study that included normotensive, treated and untreated hypertensive participants (Chapter 6). White-coat hypertension should be considered a condition of increased cardiovascular risk. Based on the results of this thesis treating doctors are advised that they should not focus solely on the white-coat hypertensive subject’s blood pressure but on their total cardiovascular risk and such subjects should be monitored for the development of both hypertension and type 2 diabetes.