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PREVALENCE OF MASKED HYPERTENSION IN A LARGE 24 HOUR AMBULATORY BLOOD PRESSURE MONITORING POPULATION

PREVALENCE OF MASKED HYPERTENSION IN A LARGE 24 HOUR AMBULATORY BLOOD PRESSURE MONITORING POPULATION


Author Block: A Johri, D Armstrong, D Brouillard, M Matangi
Kingston, Ontario

Abstract:
INTRODUCTION: Masked hypertension is detected by documenting an elevated home or average 24hr ambulatory blood pressure (ABPM) in patients who are normotensive in the office. The purpose of our study was to determine the prevalence of masked hypertension in both a treated and a medication free population using 24hr ABPM.
METHODS: We obtained 12,747 ABPM recordings in patients presenting to the Kingston Heart Clinic from May 1999 to October 2006. 4,841 24hr ABPMs were recorded on patients without any medication and 7,005 ABPMs were recorded on known hypertensives taking antihypertensives drugs. For simplicity we have confined our analysis to systolic BP values. We defined normotensive as an office systolic BP of 130mmHg. The second was an average daytime (7am-10pm) ABPM systolic BP >135mmHg.
RESULTS: Refer to Table 1.
CONCLUSIONS: The prevalence of masked hypertension in a treated population varies from 10.3% to 14.1% depending on the definition used. In an unmedicated normotensive population the prevalence of masked hypertension varies from 7.8% to 10.6%. Masked hypertension is relatively common. This brings into clinical practice the need to monitor BP outside the clinic using either patient directed home BP measurements or 24hr ABPM. There is mounting evidence that in treated patients, masked hypertension is associated with increased cardiovascular morbidity. Treatment goals were achieved in 42.7% of the 7,005 treated hypertensives.

Table 1
Total 24hr ABPM 12,747 % Mean SBP SD SBP
Total 24hr ABPM on drug treatment 7,005      
Controlled (24hr SBP <130mmHg 2,991 42.7    
Controlled (office SBP <140mmHg) 1,071 15.3 130.5 8.1
Masked (24hr SBP >130mmHg) 151 14.1 136.9 7.0
Masked (7am-10pm SBP>135mmHg) 110 10.3 141.5 6.6
Total without any medication 4,841      
Controlled (office SBP <140mmHg) 716 14.8 132.0 6.3
Masked (24hr SBP >130mmHg) 76 10.6 135.3 5.9
Masked (7am-10pm SBP>135mmHg) 56 7.8 140.1 6.2