Ambulatory blood pressure monitoring in potential renal transplant donors

F. Nurhan Özdemir1,, Galip Güz1, Siren Sezer1, Zübeyde Arat1 and Mehmet Haberal2

1 Departments of Nephrology and 2 General Surgery, Baskent University, Ankara, Turkey



   Abstract
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Background. Hypertension is considered to be a contraindication in potential renal transplant donors. Ambulatory blood pressure monitoring (ABPM) was developed as an alternative to in-office blood pressure measurement (OBPM). The aim of this study was to determine the sensitivity of ABPM in revealing hypertension in potential renal transplant donors, and to measure the correlation between ABPM results and target organ damage.

Methods. The study included 126 potential living–related renal transplant donors. The potential donors's blood pressures were measured during three separate clinic visits and then evaluated using 24-h ABPM. Cardiac and ophthalmological examinations were also performed to investigate target organ damage in all of the donors.

Results. According to the OBPM, 89 potential donors were normotensive and 37 had borderline or mild hypertension. Of the normotensive group, six were diagnosed as hypertensive after 24-h ABPM, and these subjects had target organ involvement. The status of the other 83 donors remained unchanged after ABPM and investigation for target organ damage. Thirteen of the 37 subjects who had borderline or mildly elevated pressures on OBPM were classified as normotensive after ABPM. These 13 individuals exhibited no hypertension-related target organ damage. The other 24 patients who had been classified as borderline or mildly hypertensive on OBPM fulfilled the criteria for hypertension after ABPM, and hypertensive changes were found at target organ evaluation. Before donor nephrectomy, 94 subjects who were classified as normotensive prior to transplantation underwent renal angiography for routine pretransplant evaluation, and none showed hypertensive or atherosclerotic changes.

Conclusion. In our study, ABPM was found to be more sensitive than OBPM in terms of identifying hypertension in potential renal transplant donors.

Keywords: ambulatory blood pressure monitoring; hypertension; renal transplant donors



   Introduction
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Much has been learned about ambulatory blood pressure monitoring (ABPM) over the past 15 years, and several consensus groups have recommended that this method be used in caring for certain patients. Ambulatory (non-invasive) blood pressure monitors have helped in the diagnosis of mild and borderline hypertension, and in the identification of so-called ‘office’ or ‘white coat’ hypertension [13]. Using this method of monitoring, ‘blood pressure (BP) load’ is defined as the percentage of blood pressure readings that are elevated during the day and night, over a 24-h period. The thresholds used are 140/90 mmHg for day and 120/80 mmHg for night. Normotensive subjects reportedly have a BP load of <10% [1]. Whereas, Heebels et al. [4] used the concept of ‘whole-day BP load’, defined as the percentage of BP readings >140/90 mmHg during a 24-h period, and a systolic BP (SBP) load of >50% and/or a diastolic BP (DBP) load in excess of 40% was defined as ‘hypertensive BP load’. The target organ damage seen in essential hypertension is more closely associated with ambulatory than with clinic blood pressure measurement [58]. We also know that clinic blood pressure measurements are related directly to mean levels and variability in ambulatory blood pressure [9,10]. Because target organ damage is a powerful predictor of morbidity and mortality in cases of hypertension, ABPM might offer prognostic information superior to that provided by clinic assessment [11,12].

Hypertension is considered to be a contraindication for renal transplantation in potential donors [13]. With the critical shortage of organ donors for renal transplantation, it is imperative that we evaluate each candidate carefully for absolute and relative contraindications. In this study, we compared the accuracy of blood pressure monitoring and office blood pressure measurement in donor candidates for living–related renal transplantation.



   Subjects and methods
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
The study population included 126 potential living–related renal transplant donors (65 males and 61 females) whose blood pressures were normal or borderline-to-mildly elevated. Mean donor age was 45.0±12.4 years. Office BP measurements (OBPM) were taken during clinical visits at the transplantation outpatient department prior to the start of 24-h ambulatory blood pressure monitoring, and all were carried out by the same physician under the same conditions, according to World Health Organization/International Society of Hypertension (WHO/ISH) guidelines. Three consecutive measurements were taken with a mercury sphygmomanometer, and the mean of the three measurements was recorded. Regarding office blood pressure measurement, donor candidates with BP <140/90 mmHg were classified as normotensive. Those with a SBP of 140–159 mmHg or a DBP of 90–104 mmHg were classified as borderline-to-mildly elevated.

Ambulatory BP was recorded using the fully automatic Accutracker II (SunTech Medical Instruments), an auscultatory unit that uses electrocardiographic leads for R-wave gating with the Korotkoff sounds. We set the instrument to take a measurement every 20 min through the day (6:00 am to 11:00 pm), and every 45 min through the night (11:00 pm to 6:00 am). The system's BP range was 10–250 mmHg for both systolic and diastolic pressures. The default setting for maximum pressure was 200 mmHg, and for minimum pressure was 40 mmHg.

We educated subjects in how to care for the monitor during the study period. Since arm motion can lead to substantial error, potential donors were told to keep their arms still and relaxed during each individual BP measurement. Ambulatory BP measurements were recorded during the donor candidate's daily routine. The BP and heart rate data were downloaded into customized software and edited, and summary statistical and graphical displays were generated. Candidates were re-evaluated with ambulatory BP measurements if more than 10% of their measurements were unsuccessful.

We analysed the ambulatory BP monitoring by examining BP load, calculating the percentage of BP readings that were elevated during the period of interest. BP load was calculated 24-hours-a-day, including both waking and sleeping periods. Thresholds were 140/90 mmHg during the waking period and 120/80 mmHg during sleep. Candidates were classified as hypertensive according to ABPM if their BP load exceeded 20%.

Two-dimensional echocardiographic imaging was carried out to investigate left ventricular hypertrophy. The same physician did the imaging in all cases, according to standard recommendations [14,15]. All recordings were coded and read by a blind observer. Criteria for left ventricular hypertrophy were also investigated in all subjects using telecardiography. Ophthalmological studies were also performed on all the donor candidates and the Keith-Wagener classification was used to identify hypertensive retinopathy.

Statistics
Statistical analysis was performed using the program SPSS 7.5 for Windows. The differences in distribution of candidates as normotensive or hypertensive according to OBPM and ABPM, and the frequency of target organ damage in hypertensive candidates evaluated by OBPM vs ABPM were tested using chi-square analysis. P-values <0.05 were considered statistically significant.



   Results
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
According to the OBPM, 89 donor candidates were normotensive and 37 had borderline or mild hypertension. Based on ABPM, 96 candidates were normotensive and 30 were hypertensive. There was a significant difference in the numbers of normotensive and hypertensive candidates based on OBPM vs ABPM (P<0.05). The status of six normotensive donor candidates with OBPM changed to hypertensive after ABPM was performed. Target organ involvement was also present in these subjects. The status of the other 83 potential donors who were normotensive on OBPM remained unchanged after ABPM and investigation for target organ damage. Going in the opposite direction, 7 of the 13 subjects who had borderline or mildly elevated pressures on OBPM were classified as normotensive after ABPM. These individuals exhibited no hypertension-related target organ damage or cardiological and ophthalmological evaluation. The other 24 patients who had been classified as borderline or mild hypertensive on clinic BP measurement fulfilled the criteria for hypertension after ABPM. These results are shown in Table 1Go. Twenty-four of 37 (64.9%) candidates who were hypertensive based on OBPM had target organ damage, and all 30 candidates who were hypertensive based on ABPM had target organ damage. There was a statistically significant difference between the frequency of target organ damage in candidates who were hypertensive on OBPM and the frequency in those who were hypertensive on ABPM (P<0.05). The differences in distribution of candidates as normotensive or hypertensive according to OBPM and ABPM, and the frequency of target organ damage in hypertensive candidates evaluated by OBPM vs ABPM are shown in Table 2Go. The 96 subjects who were classified as normotensive based on ABPM, cardiological and ophthalmological examination underwent selective renal angiography as routine preparation for renal transplantation. None showed hypertensive or atherosclerotic change on selective renal angiogram.


View this table:
[in this window]
[in a new window]
 
Table 1. Results of donor candidate evaluation

 

View this table:
[in this window]
[in a new window]
 
Table 2. The distribution of candidates and the frequency of target organ damage according to OBPM and ABPM

 



   Discussion
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 
Measurement of blood pressure by a physician generally produces higher values than those recorded by patients themselves. ‘White coat’ hypertension is defined as persistent clinic hypertension despite normal BP during daily life. This phenomenon, which may be due to an alerting reaction associated with the clinic measurement of BP, often leads to the diagnosis of hypertension in certain normotensive individuals [1,16]. Mancia et al. [17] observed that the approach of a physician and recording of blood pressure from an arm was accompanied by an abrupt increase in arterial pressure at the same time that continuous intra-arterial blood pressure was recorded. In the present study, we investigated the importance of the white coat effect in evaluating potential living–related renal transplant donors, comparing ABPM and OBPM and observing for target organ damage. Our investigation confirms that ABPM is more sensitive than OBPM with regard to identifying hypertension in potential renal transplant donors. The findings using this method were positively correlated with corresponding cardiac and ophthalmological assessment of target organ damage.

Hypertension is a contraindication for living-donor kidney transplantation [13]. Torres et al. [18] reported an increased prevalence, or acceleration, of hypertension after nephrectomy in renal transplant donors who had been diagnosed previously with borderline or definite hypertension. This finding underlines the importance of studying hypertension in living–related transplant donor candidates with regard to the health of the donors themselves. In addition, Cho [19] emphasized that prolonged donor hypertension has a statistically significant deleterious effect on graft survival.

Screening for hypertension is the initial step in evaluating renal transplant donor candidates, and requires testing methods that are accurate and noninvasive. This study indicates that ABPM shows promise as a reliable and important technique for the first-step evaluation of potential renal transplant donors.



   Notes
 
Correspondence and offprint requests to: F. Nurhan Özdemir, MD, Assoc. Prof. Of Nephrology, Baskent University, Faculty of Medicine, Fevzi Çakmak Bulvari 10. Sokak No: 45, Bahçelievler, Ankara, 06490, Turkey. Back



   References
 Top
 Abstract
 Introduction
 Subjects and methods
 Results
 Discussion
 References
 

  1. Mansoor GA, White WB. Ambulatory blood pressure monitoring is a useful clinical tool in nephrology. Am J Kidney Dis1997; 30: 591–605[ISI][Medline]
  2. White WB, Lund-Johansen P, Omvik P. Assessment of four ambulatory blood pressure monitors and measurements by clinicians versus intraarterial blood pressure at rest and during exercise. Am J Cardiol1990; 65: 60–66[ISI][Medline]
  3. Verdecchia P, Schillaci G, Guerrieri M et al. Circadian blood pressure changes and left ventricular hypertrophy in essential hypertension. Circulation1990; 81: 528–536[Abstract]
  4. Heebels AE, Nube MJ, van Limbeek J, Grooteman MP, van Geelen JA. CAPD patients exhibit a nocturnal fall in blood pressure: a single-centre study. Neth J Med1995; 46: 225–231[ISI][Medline]
  5. Rowlands DB, Glover DR, Ireland MA et al. Assessment of left ventricular mass and its response to anti-hypertensive treatment. Lancet1982; 1: 467–470[Medline]
  6. Drayer JIM, Weber MA, De Young JL. BP as a determinant of cardiac left ventricular muscle mass. Arch Intern Med1983; 143: 90–92[Abstract]
  7. Devereux RB, Pickering TG, Harshfield GA et al. Left ventricular hypertrophy in patients with hypertension: Importance of blood pressure response to regular recurring stress. Circulation1983; 68: 470–476[ISI][Medline]
  8. Devereux RB, Reichek N. Echocardiographic determination of left ventricular mass in man: validation of the method. Circulation1977; 5: 613–618
  9. Verdecchia P, Schillaci G, Boldrini F et al. Risk stratification of left ventricular hypertrophy in systemic hypertension using non-invasive ambulatory blood pressure monitoring. Am J Cardiol1990; 66: 583–590[ISI][Medline]
  10. Parati G, Pomidossi G, Albini F, Malaspina D, Mancia G. Relationship of 24-hour blood pressure mean and variability to severity of target organ damage in hypertension. J Hypertens1987; 5: 93–98[ISI][Medline]
  11. Koren MJ, Devereux RB, Casale PN, Savage DD, Laragh JH. Relation of left ventricular mass and geometry to morbidity and mortality in uncomplicated essential hypertension. Ann Intern Med1991; 114: 345–352[ISI][Medline]
  12. Mensah GA, Koren MJ, Ulin R et al. Comparison of classification of the severity of hypertension by blood pressure level and by World Health Organisation criteria in the prediction of concurrent cardiac abnormalities and subsequent complications in essential hypertension. J Hypertens1993; 11: 1429–1440[ISI][Medline]
  13. Kasiske BL. The evaluation of prospective renal transplant recipients and living donors. Surg Clin North Am1998; 78: 27–39[ISI][Medline]
  14. Devereux RB, Reichek N. Echocardiographic determination of left ventricular mass in man: validation of the method. Circulation1977; 5: 613–618
  15. Gosse P, Roudaut R, Dallocchio M. Is echocardiography an adequate method to evaluate left ventricular hypertrophy regression? Eur Heart J1990; 11(Suppl. G): 107–112[ISI][Medline]
  16. Gosse P, Promax H, Durandet P, Clementy J. ‘White coat’ hypertension. No harm for the heart. Hypertension1993; 22: 766–770[Abstract]
  17. Mancia G, Parati G, Pomidossi G, Grassi G, Casadei R, Zanchetti A. Alerting reaction and rise in blood pressure during measurement by physician and nurse. Hypertension1987; 9: 209–215[Abstract]
  18. Torres VE, Offord KP, Anderson CF, Velosa JA, Frohnert PP, Donadio JV Jr, Wilson DM. Blood pressure determinants in living-related renal allograft donors and their recipients. Kidney Int1987; 31: 1383–1390[ISI][Medline]
  19. Cho YW. Expanded criteria donors. Clin Transpl1998; 421–436
Received for publication: 4.10.99
Revision received 28. 1.00.