1 Division of Nephrology and 2 Department of Internal Medicine, Marmara University Medical School, Istanbul, Turkey
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Methods. Seventy-four CAPD patients were included in the final analysis. All patients underwent echocardiographic examination and received ABPM. Patients undergoing CAPD were categorized into two groups: uncontrolled HT (Group A) and normotensive and controlled HT (Group B). Intravascular volume status was determined using the IVCD index and collapsibility index (CI) on the same day as ABPM.
Results. The prevalence of HT was 84% when using office measurements and 82% when using daytime ABPM. Daytime BP was 147/92 mm Hg by office measurements and 145/91 mm Hg by ABPM (P>0.05). The prevalence of uncontrolled HT measured by ABPM was 73% (n=54). Patients with uncontrolled HT (Group A) were taking more antihypertensive medications than patients with normotension and controlled HT (Group B, n=20; 1.0±0.8 vs 0.5±0.7, P=0.008). The IVCD index was higher in Group A than in Group B (9.2±2.1 vs 7.7±1.9 mm/m2, P=0.007). There was no correlation between IVCD index and office BP, ABPM measurements or LVMI. The LVMI was also higher in Group A than in Group B (145±39 vs 118±34 g/m2, P<0.01). Stepwise multiple regression analysis revealed that 24 h diastolic BP and haemoglobin were independent determinants of LVMI.
Conclusion. Uncontrolled HT on background therapy is highly prevalent among volume overloaded CAPD patients. Further long-term prospective studies examining effects of salt restriction and ultrafiltration on BP control and left ventricle wall thickness are warranted.
Keywords: CAPD; hypertension; inferior vena cava diameter (index); left ventricular hypertrophy; plasma volume overload
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Earlier studies suggested that patients on long-term CAPD treatment were more volume overloaded than patients on short-term CAPD [7]. Additionally, patients on long-term CAPD had higher left ventricular mass [8]. A recent study suggested that CAPD patients were more volume overloaded and had higher prevalence of left ventricular hypertrophy (LVH) compared with haemodialysis (HD) patients [9].
Ambulatory blood pressure monitoring (ABPM) has several advantages over office blood pressure (BP) measurements. A continuous 24 h measurement of BP can be performed by ABPM, providing a superior assessment of BP control. In addition, circadian BP variability was better associated with HT-induced end-organ damage in dialysis patients [10,11].
The present study aimed to determine the prevalence of uncontrolled HT during background therapy in CAPD patients by using office measurements and ABPM. We additionally determined whether intravascular volume status, which was assessed by IVCD index, contributes to higher BP and increased left ventricular mass index (LVMI).
![]() |
Subjects and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Blood pressure measurements
Patients were allowed to continue their antihypertensive treatment during ABPM and during office BP measurements. After a 5 min rest period, office BP measurements were performed three times and the average of the last two measurements was accepted as the final office BP [12]. During the same day, patients were monitored with Spacelab® 90207 ambulatory monitor (Spacelabs Medical, Redmond, USA) every 20 min from 07.00 to 23.00 and every 30 min from 23.00 to 07.00. Monitors were calibrated against a mercury sphygmomanometer at the beginning of each measurement and monitoring was performed in accordance with recent guidelines [13]. Ambulatory blood pressure monitoring data included 24 h systolic blood pressure (SBP), 24 h diastolic blood pressure (DBP), 24 h mean arterial blood pressure (MAP), daytime SBP, daytime DBP, daytime MAP, night-time SBP, night-time DBP and night-time MAP. Hypertension was defined as daytime SBP 135 mm Hg and/or daytime DBP
85 mm Hg using ABPM, SBP
140 mm Hg and/or DBP
90 mm Hg using office BP measurements, or current treatment with an antihypertensive drug [12]. Patients undergoing CAPD were categorized as uncontrolled HT with daytime ABPM
135/85 mm Hg and as normotensive or controlled HT with daytime ABPM below 135/85 mm Hg according to current definitions and criteria by Burt and colleagues [12,14]. Uncontrolled HT patients constituted Group A, and normotensive and controlled HT patients constituted Group B.
Echocardiographic assessment
Two-dimensional and M-mode echocardiographic examinations were performed using an Ultramark 9 (Advanced Technology Laboratories, Bothell, WA) with a 2.25 MHz transducer. Echocardiographic examinations were performed at midday after having completely emptied the peritoneal dialysate. All examinations were recorded on videotape and assessed at study completion by two independent physicians (AT, HT) who were blinded with respect to patient group. At least three consecutive cardiac cycles were analysed for each patient. All echocardiographic parameters, including interventricular septal thickness (IVST), left ventricular posterior wall thickness (PWT), and left ventricular internal dimension (LVID), were measured at end-diastole (d). Ventricular dimensions were assessed through 2-D guided M-mode tracings according to American Society of Echocardiography (ASE) recommendations using leading edge to leading edge conventions [15]. Left ventricular (LV) mass was calculated using the formula [16]: ASE-cube LV mass=1.04x((IVSTd+LVIDd+PWTd)3LVIDd3). Because ASE-cube LV mass calculation results in overestimation of LV mass by about 25%, the regression formula of Devereux et al. [17] was used to correct LV mass measurements, which is similar to the Penn convention measurement [18] (0.80x(ASE-cube LV mass)+0.6). The LVMI was calculated by dividing LV mass by body surface area (BSA, m2). Left ventricular hypertrophy was defined as LVMI >131 g/m2 in males and >100 g/m2 in females [19].
Determination of intravascular volume status
Intravascular volume status was determined using the IVCD index and collapsibility index (CI) on the same day as ABPM. The IVCD was measured by two-dimensional guided M-mode echocardiography during expiration and maximal inspiration while avoiding Valsalva-like manoeuvres [6]. Index of IVCD was calculated as the ratio of IVCD at experium to BSA. Collapsibility index was defined as ((maximal diameter on expiration-minimal diameter on deep inspiration)/maximal diameter on expiration) x100.
Laboratory measurements
Whole blood counts and blood chemistry were analysed by standard laboratory procedures. Intact parathyroid hormone (PTH) levels were determined using radioimmunoassay (Sigma-Aldrich Laboratories, The Woodlands, Texas, USA). Kt/V was calculated from total loss of urea nitrogen in the spent dialysate using the Watson equation [20]. Serum albumin concentration was measured by the bromocresol green method. The peritoneal equilibration test (PET) and Kt/V measurement were done within two weeks of ABPM measurement.
Statistical analysis
All calculations were done using SPSS. Data were expressed as mean±SD. Office BP measurements and ABPM data were compared by using one-way ANOVA, and comparison between Groups A and B were done by MannWhitney U tests. Categorical variables were analysed by the Fisher's exact test and McNemar test. Stepwise multiple regression analysis was performed to define the predictors of LVMI. A two-tailed P value less than 0.05 was considered significant.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The 24 h SBP and DBP with ABPM were 143±26 and 90±18 mm Hg, daytime were 145±26 and 91±18 mm Hg, and night-time were 139±28 and 86±19 mm Hg, respectively (Table 1). Office BP values were similar to daytime ABPM values (147±27 vs 145±26 mm Hg SBP, P=0.991; 92±18 vs 91±18 mm Hg DBP, P>0.05). Sixty-two patients (84%) were hypertensive according to office BP measurements and 61 patients (82%) were hypertensive according to daytime ABPM (P>0.05). The prevalence of uncontrolled HT was 73% (n=54) according to daytime ABPM measurements.
|
|
|
Office BP measurements and ABPM levels were significantly higher in Group A compared with Group B (Table 3). Group A used more antihypertensive drugs than Group B (1.0±0.8 vs 0.5±0.7, P=0.008). Index of IVCD at experium was higher in Group A than in Group B (9.2±2.1 vs 7.7±1.9 mm/m2, P=0.007). The CI was similar in both groups (52.5±10.6% vs 55.5±10.8%, P=0.64). The IVCD index did not correlate with any of the variables, including 24 h SBP, 24 h DBP, duration of CAPD treatment, age, serum albumin or haemoglobin. In addition, ABPM did not correlate with age, duration of CAPD treatment, serum PTH or albumin.
The indexes of LVID, IVST and PWT were higher in Group A (uncontrolled HT) compared with Group B (normotensive or controlled HT), but these differences did not reach statistical significance. Our calculations revealed that low statistical power was due to inadequate patient numbers (Table 4). Similarly, the difference in prevalence of LVH was not significant (70% in Group A vs 60% in Group B, P=0.41). The LVMI in Group A (145±39 g/m2) was significantly higher than in Group B (118±34 g/m2, P<0.01). The LVMI correlated positively with 24 h SBP (r=0.46, P<0.0001), 24 h DBP (r=0.50, P<0.0001), daytime SBP (r=0.45, P<0.0001), daytime DBP (r=0.49, P<0.0001), night-time SBP (r=0.43, P=0.0001), night-time DBP (r=0.48, P<0.0001), office SBP (r=0.41, P<0.0005) and office DBP (r=0.24, P<0.05), and inversely with haemoglobin (r=-0.40, P=0.0005). There was a positive correlation between IVCD index and LVID, but not with other echocardiographic measurements of the left ventricle.
|
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Rocco et al. [2] reported that the prevalence of HT was 35% in a cohort of 926 CAPD patients, whereas Gunal et al. [5] found 60% using office measurements. Currently, ABPM is used frequently for diagnosing HT, and ABPM data correlated better with end-organ damage compared with office measurements in ESRD patients [2123]. In our study, ABPM was as effective as office measurements in diagnosing HT and determining adequacy of BP control.
In the present study, LVMI was higher in patients with uncontrolled HT compared with patients having controlled HT and normotension. This finding is in agreement with previous studies. Takeda et al. [8] reported higher LVMI in CAPD patients having higher BP levels. In another group of CAPD patients that were followed for 18 months, the initial 52% prevalence of LVH increased to 76% [24]. On multiple regression analysis in the current study, 24 h DBP and haemoglobin were independent determinants of LVMI. However, we failed to show any correlation between IVCD index and LVMI. When analysing chest X-ray in ESRD patients, previous studies demonstrated a correlation between volume control and cardiac structure [5,25]. Ozkahya et al. [26] demonstrated regression of cardiothoracic index and LVH in HD patients by ultrafiltration. In this study, LVID index, IVST index and PWT index were increased in uncontrolled HT compared with normotension and controlled HT, but the difference did not reach statistical significance due to low patient numbers. The higher LVMI and regression of LVMI by ultrafiltration may be also be explained by higher LVID in the former studies. In contrast to our study, Enia et al. [9] reported a higher degree of LVMI in their CAPD population and compared these results with HD patients. To our knowledge, there have been no reports examining the effect of fluid removal on LV wall thickness in CAPD patients.
A positive correlation between IVCD index and intravascular volume status has been described previously in HD patients [27]. Similarly, serum levels of atrial natriuretic peptide, a biochemical marker of intravascular volume status, correlated positively with IVCD index in CAPD patients [28]. In our study, there was no difference in urine output or ultrafiltration between Groups A and B. A volume overload in Group A may have been due to higher salt and water intakes. In a crossover, placebo-controlled study, Fine et al. [29] showed that the addition of 60 mmol of sodium to the daily diet significantly increased blood pressure from 135/77 to 144/82 mm Hg in normotensive or mildly hypertensive CAPD patients. Recent studies have also suggested that peritoneal dialysis solutions with low sodium concentrations improve control of blood pressure by removal of excess sodium without a change in body weight or ultrafiltration volume [30]. Furthermore, Gunal et al. [5] reported normalization of BP in 78% of 47 hypertensive CAPD patients by salt restriction and ultrafiltration with hypertonic solutions.
The independent determinants of LVMI in our study were haemoglobin and 24 h DBP. Studies aiming to define the determinants of increased LVMI in CAPD patients are rare in the literature. In reports examining both HD and CAPD patients, haemoglobin and BP values were the primary determinants of LVMI [3133]. Our study agrees with these previous reports by showing that uncontrolled HT had higher BP values and lower haemoglobin levels compared with controlled HT and normotensive patients.
The present study has several limitations. Firstly, this study was cross-sectional and the effect of volume status on the progression of LVM should be prospectively investigated in a larger group. The effect of volume removal by ultrafiltration on LVMI and on left ventricular wall thickness should also be investigated prospectively. Secondly, the reproducibility of ABPM may be questionable in ESRD patients. However, a previous report indicated that ABPM reproducibility was better than pre- or post-HD office BP measurements [34].
In conclusion, hypervolaemia as indicated by a higher IVCD index is a risk factor for uncontrolled HT and increased LVMI. Dietary instructions to limit salt intake may prevent volume overload in CAPD patients. We believe that a new prospective study with increased patient numbers would probably overcome the limitations of the present study.
![]() |
Acknowledgments |
---|
![]() |
Notes |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|