Clinical significance of nocturnal blood pressure monitoring

Although there are certain technical problems in determining nocturnal BP by ambulatory BP monitoring, the information provided on nocturnal BP has possible clinical significance. Short-term BP variability, an elevated BP during sleep and amplitude and sleep of nocturnal BP decline might be responsible for cardiovascular mortality. Furthermore, circadian BP variation might also be responsible for cardiovascular morbidity and mortality. The nocturnal BP level, even in extreme dippers with diurnal hypertension, is equivalent to or higher than that in normotensive subjects. Antihypertensive effects of drugs with different pharmacologic properties positively correlate with basal ambulatory BP. Therefore, there is a critical BP level at which the antihypertensive effect disappears. The critical BP level for each drug is in normal BP range but not in the hypotensive range. Therefore, an antihypertensive regimen would be safe even in extreme-dipper hypertension without excessive nocturnal hypotension, and might even be beneficial because of the decreasing amplitude and speed of the nocturnal BP decline. We conclude that an antihypertensive drug regimen should control BP throughout a 24-h period regardless of circadian BP variation.