Journal of Human Hypertension (2006) 20, 543–545 & 2006 Nature Publishing Group All rights reserved 0950-9240/06 $30.00 www.nature.com/jhh
RESEARCH LETTER
Blood pressure measurement in patients with rate controlled atrial fibrillation using mercury sphygmomanometer and Omron HEM-750CP deice in the clinic setting Journal of Human Hypertension (2006) 20, 543–545. doi:10.1038/sj.jhh.1002016; published online 6 April 2006
We have compared accuracy of blood pressure (BP) readings using manual mercury sphygmomanometer and Omron HEM-750 CP oscillometric device, in patients with atrial fibrillation (AF) and subjects with sinus rhythm (SR). Our results suggest Omron HEM-750CP can be used in AF patients and importance of multiple readings with mercury sphygmomanometer in the clinic settings. Blood pressure is measured non-invasively in the clinical setting using manual or automatic devices. The mercury sphygmomanometer is the current gold standard device for measuring blood pressure that may be phased out due to safety issues and replaced by automated devices in the clinic settings. Blood pressure varies physiologically with each beat and is influenced by the circadian rhythm, the sympathetic and baro-receptor activity, emotional and humoral factors, seasons and levels of physical activity.1,2 Manual sphygmomanometer readings are subject to clinician errors due to inappropriate cuff size, digit bias, too rapid cuff deflation, white coat effect and use of non-validated devices.3 The European Society of Hypertension (ESH) provides guidelines on how to measure blood pressure and recommends machines that are calibrated and validated for patients in SR.4 In AF there are no generalised accepted methods of determining auscultatory end points. BP measuring devices vary greatly in their ability to accurately record blood pressure in patients with AF.5 Atrial fibrillation is the most common sustained arrhythmia with a lifetime incidence of 21.6% in females and of 22.7% in males.6,7 Hypertension may be the most common aetiology of AF.7 Hypertension and AF significantly increase risk of a stroke.8 It is important to measure blood pressure accurately in patients with AF.9,10 We compared the use of mercury sphygmomanometer and Omron HEM-750CP in 20 patients with AF, group matched for age and sex with 20 subjects in SR in a clinic setting. Both devices are recommended by the ESH.4 The study had ethical approval and each patient signed a written consent.
Patients had four BP readings taken with each device in supine position over right brachial artery at 2-min intervals, after a rest period of 15 min. Same clinician took the readings using an appropriate cuff size. All patients were selected from a cardiology clinic. In the AF group 11 patients were rate controlled, with either digoxin (n ¼ 8) or amiodarone (n ¼ 3). All patients had an ejection fraction 455% on the echocardiogram and 95% of the AF patients had 24 h Holter electrocardiogram to assess 24 h rate control. AF (50% (10/20)) patients and 45% (9/20) SR patients were on treatment for hypertension (majority of these patients were on more than one antihypertensive treatment). Inclusion criteria was medically stable patient with rate controlled AF. Exclusion criteria were end stage renal failure, uncontrolled blood pressure, dementia, congestive cardiac failure and unstable angina. We calculated the mean and the standard deviation (s.d.) of the four manual and the four Omron systolic (SBP) and diastolic blood pressure (DBP) readings. We then calculated the average s.d. of the mean manual and Omron systolic and diastolic readings for each group. An independent t-test was used to compare the difference in within subject s.d. between the two groups of patients that is, AF and SR. A paired t-test was used to compare the difference in within subject s.d. within each patient group using two devices, that is, manual and Omron machine. Mean age was 70.078.4 (mean7s.d.) years in AF group and 70.976.5 years in SR group (P ¼ 0.72), which was representative of the age group where AF is more prevalent.7 Sex ratio was 52.6% females in AF and 55.5% in SR group (P ¼ 0.74), 47.4% males in AF and 44.5% in SR group (P ¼ 0.63). Mean heart rate was 75711 beats per minute (b.p.m.) in AF group compared to 6579 b.p.m. in SR group (P ¼ o0.01). Mean body mass index in AF group was 27.6 compared to SR group 27.1 (P ¼ 0.73). 21% were current smokers in AF group compared to 10% in SR group. All patients had normal full blood count, thyroid function test and 97.5% had a normal renal function. The difference in SBP in the AF group between manual and Omron device was 5 mm Hg and the
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Table 1 Blood pressure measurements between two groups
Mean BP7s.d.
SBP-manual (mm Hg) SBP-Omron (mm Hg) DBP-manual (mm Hg) DBP-Omron (mm Hg)
Average within subject s.d.
Difference in within subject s.d. between manual and Omron BP readings in AF Paired t-test
Difference in within subject s.d. between manual and Omron BP readings in SR Paired t-test
Difference in Difference in within subject within subject s.d. between s.d. between manual BP Omron BP readings in AF readings in AF and SR and SR Unpaired t-test Unpaired t-test
AF
SR
P1
AF
SR
P*
P*
P2
P2
126718
139723
0.08
5.2
1.8
0.18
o0.01
0.01
0.50
131712
141716
0.04
6.5
5.8
72715
74712
0.40
3.2
2.1
0.49
0.40
0.03
0.40
73715
77710
0.40
3.8
5.0
Abbreviations: AF, atrial fibrillation; BP, blood pressure; DBP, diastolic blood pressure; SBP, systolic blood pressure; s.d., standard deviation; SR ¼ sinus rhythm. P1 compares BP taken by the two machines in the two groups. P* (paired t-test) – difference in within subject s.d. between manual and Omron in AF group and sinus rhythm group (within group comparison). P2 (unpaired t-test) – difference in within subject s.d. between manual readings in AF and SR groups and Omron difference in AF and SR groups (between group comparison).
difference in SBP in the SR group between manual and Omron device was 2 mm Hg. The difference in within-subject variation in SBP and DBP readings was higher with manual readings in the AF group compared with the SR group, which was statistically significant (P2 ¼ 0.01 SBP, P2 ¼ 0.03 DBP). The difference in within-subject variation in SBP and DBP was not statistically significant between the two groups with the Omron machine (P2 ¼ 0.50 SBP, P2 ¼ 0.40 DBP). In the SR group the within-subject variability with SBP and DBP was lower with the manual manometer than with the Omron device (P*o0.01 SBP, P* ¼ 0.40 DBP) but in AF group there was no statistical difference between the two machines (P* ¼ 0.18, P* ¼ 0.49) (Table 1). The Omron HEM-750CP device is approved by ESH grade B/A. With Grade A approval, 95% of Omron readings are within 15 mm Hg difference between the two machines.4 Our results are within 15 mm Hg difference. The higher within subject variability in AF group with both devices may be explained by exaggerated beat-to-beat changes in stroke volume and LV contractility.9,10 In AF, the variability with manual readings may be higher due to observer expectation of variability and a greater possibility of clinician error in listening to the first sound compared to SR.10 Inter-observer variability has been shown to be higher than intra-observer variability with manual manometer for the systolic than the diastolic readings in sinus rhythm. This variability would be exaggerated in AF patients.10 Changes in baroreceptor activity and endothelial – nitric oxide sensitivity may also contribute to enhanced short-term blood pressure variability in AF.11 Lower variability with Journal of Human Hypertension
manual readings in SR compared to Omron may be due to expected bias of less variation. The within subject variability between the two groups using the Omron machine there was no statistical difference. The Omron HEM-750CP is an oscillometric device, which detects variations in the pressure oscillations due to arterial wall movement beneath an occluding cuff. An empirically derived algorithm is employed which calculates SBP and DBP from the mean pressure. Measurements with oscillometric devices may be affected by arrhythmia’s;3 however, this was not confirmed by our results. Our study shows that the Omron HEM-750CP device had similar within subject variations in both groups and can be used in the clinic setting in patients with controlled AF. It is important to take multiple readings with the mercury manometer in AF patients. Our study should be confirmed using a larger group with the clinician blinded to preceding manual readings, in patients with uncontrolled AF and record between observer variability. Conflict of interest: None.
What is known about this topic? Atrial fibrillation is a common condition. Hypertension and AF are important risk factors for stroke.6–8 Blood pressure has short and long term variability which is exaggerated in AF patients.11 What this study adds? OMRON HEM-750 CP device can be used in the clinic setting in AF patients. It is important to take multiple readings with the mercury sphygmomanometer in patients with AF.
Research Letter 545
B Jani1, CJ Bulpitt1 and C Rajkumar1,2 1 Section of Care of the Elderly, Imperial College, Hammersmith Hospital, London and 2 Faculty of Medicine, Brighton & Sussex Medical School, Brighton, UK E-mail:
[email protected] Published online 6 April 2006
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