The measurement of orthostatic blood pressure as a screening tool for masked hypertension with abnormal circadian blood pressure rhythm

Abstract

I t has been repeatedly noted that cardiovascular events often occur in individuals who have never been diagnosed with hypertension. These events occur in part because it is difficult to identify masked hypertension in untreated individuals. However, the elevation of subclinical blood pressure (BP) in individuals with masked hypertension can exacerbate damage to the hypertensive target organ and result in an overt cardiovascular event. 1,2 Although home BP measurements in the morning and evening are recommended by the Japanese Society of Hypertension 2014 guidelines, 3 home BP monitoring may not always detect a BP elevation if the BP is elevated at times other than the time of the home BP measurement (for example, other than in the morning and evening). Ambulatory BP monitoring (ABPM) is thus useful to detect masked hypertension because it provides BP data at many more time points compared with home BP monitoring.Physicians should try to identify individuals who are at a high risk for masked hypertension, with the goal of preventing cardiovascular events in this population. The reported characteristics of masked hypertension are male sex, middle age, smoking, regular alcohol drinking and high daytime physical activity; 4 in fact, such populations show increased arterial damage. 5 However, an effective method for identifying masked hypertension has not yet been established.In this issue of Hypertension Research, Tabara et al. 6 demonstrate a relationship between masked hypertension and orthostatic hypertension in healthy individuals. Although this association between orthostatic hypertension and masked hypertension has been reported in hypertensive patients, 7 it is notable that the subjects in the study by Tabara et al. were healthy individuals, and the results illustrate an association between orthostatic BP changes and awake BP obtained by ABPM. The findings by Tabara et al. clearly demonstrate that orthostatic hypertension has a common pathophysiology with masked hypertension. However, the mechanisms underlying the link between orthostatic hypertension and masked hypertension are not clearly understood.One possible mechanism underlying this link is enhanced sympathetic nervous system activity. It was observed that the plasma noradrenaline level was increased after standing in patients with orthostatic hypertension. 8,9 This abnormality in the sympathetic nervous system would cause an abnormal circadian BP rhythm, such as a morning BP surge, stress hypertension or exercise-induced hypertension, and these conditions may be expressed as masked hypertension. In a study by Tabara et al., the average awake BP values measured by ABPM and office BP are used to define masked hypertension. The masked hypertension observed in that study would thus include morning hypertension-type masked hypertension. Considering past and present findings, it is apparent that masked hypertension, orthostatic hypertension and the morning BP surge are closely related to one another 9,10 ( Figure 1).According to the results reported by Taba...

Standing orthostatic blood pressure measurements cannot be replaced by sitting measurements

“…28 Moreover, a relation between hypertension and an increase in SBP after postural change has been described. 29,30 Although the DBP curves showed a similar trend, the decrease in DBP was larger in the sitting position compared with that in the standing at the last five timeframes after postural change. As muscle activity in the sitting position is almost 2.5 times lower compared with the standing, 31 the lower DBP could be a physiological effect from reduced activation of the skeletal muscle pump.…”

Home Blood Pressure in Health and Disease

“…The morning BP surge, which in theory affects half of all home BP registrations, may also contribute to the higher home vs office BP, MH, and the increased risk it is associated with (180). BP decreases by 10-20% during sleep, and then surges in the morning with a peak after waking (181,182).…”

Consensus statement on the definition of orthostatic hypertension endorsed by the American Autonomic Society and the Japanese Society of Hypertension

“…Others may also be hypertensive while supine or seated with further worsening of blood pressure when standing. It is possible that these subgroups require a different diagnostic and therapeutic approach [ 2 , 9 ].…”