| Abstract|| |
Fluid status in the body plays an important role on left ventricular (LV) filling in patients with end-stage renal disease (ESRD) on regular hemodialysis (HD), and plays a role in intra-dialysis hemodynamic derangement. Fifty-two patients with ESRD on regular HD, including 34 males with a mean age of 45.5 ± 13 years (range 18-72 years), were studied. All patients underwent Echo-pulsed Doppler study before and immediately after a HD session. The Echo Doppler indices noted were: LV cavity dimension and wall thickness, LV ejection fraction (LVEF%), trans-mitral early diastolic filling velocity (E wave), atrial filling diastolic velocity (A wave), E/A ratio, Deceleration Time (DT) of E wave, Isovolumic relaxation time (IVRT), Aortic Velocity Integral (AVI) and Inferior Vena Cava Diameter (VCD) at expiration. Patients were divided into two groups according to the amount of net ultra filtrate loss after HD. Group I comprised of 25 patients with fluid loss of < 2 liters, and Group II had 27 patients with fluid loss > 2 liters. During the HD session, each patient was observed for the development of acute clinical events such as arterial hypotension (systolic BP less than 90 mmHg), chest pain and arrhythmias. There was a significant difference between the two groups in the mean values, pre- and post- HD, of reduction of E wave velocity (p< 0.01), the reduction of E/A ratio (p< 0.05), the increment in DT of E wave (p< 0.05), the reduction in AVI (p< 0.01) and the reduction of VCD (p< 0.05). There was no significant difference between the groups in the reduction of A wave velocity and the reduction of IVRT. Among the study patients, 11 (21%) developed systolic hypotension during HD. The pre-dialysis mean values of E/A ratio and DT of E wave in patients who developed hypotension compared to those who did not was 0.7 ± 0.2 vs 1.1 ± 0.2.1 (p< 0.001) and 246 ± 40 vs 224 ± 34 msec (p< 0.05), respectively. Our study suggests that preload reduction in patients with ESRD on regular HD is directly proportional to the reduction of left ventricle early filling and prolongation of Deceleration Time of E wave. The potential risk of intra-dialysis hypotension can be predicted, if LV diastolic Pulse Doppler predialysis E/A ratio is less than 0.7 and Deceleration Time of E wave is more than 246 msec. Careful assessment of these patients is crucial to prevent hypotension, especially if a large preload reduction is required.
Keywords: Doppler, Hemodialysis, Hypotension
|How to cite this article:|
Alarrayed S, Garadah TS, Alawdi AA. The impact of left ventricular preload reduction on cardiac pulsed doppler indices during hemodialysis and its relation to intra-dialysis
hypotension: A pulsed doppler study. Saudi J Kidney Dis Transpl 2009;20:201-7
|How to cite this URL:|
Alarrayed S, Garadah TS, Alawdi AA. The impact of left ventricular preload reduction on cardiac pulsed doppler indices during hemodialysis and its relation to intra-dialysis
hypotension: A pulsed doppler study. Saudi J Kidney Dis Transpl [serial online] 2009 [cited 2014 Aug 23];20:201-7. Available from: http://www.sjkdt.org/text.asp?2009/20/2/201/45522
| Introduction|| |
Maintaining optimal fluid status in patients with end-stage renal disease (ESRD) on regular hemodialysis (HD) is crucial to avoid circulatory complications. , One of the common clinical manifestations of hemodynamic instability during HD is hypotension. The incidence of asymptomatic reduction in blood pressure during HD is in the range of 15-50%, which may contribute to increase in the morbidity among this patients.  Thus, the dialysis prescription should be individualized and designed to achieve optimal fluid status in the patients.
Pulsed wave Doppler echocardiography plays an important rule in the evaluation of the diastolic filling pattern of the left ventricle (LV). There are different types of cardiac filling paterns that have been described in various diseases such as hypertension, which is associated with abnormal relaxation pattern (Type I), and dilated cardiomyopathy, which is associated with restrictive filling pattern (Type IV).  Various parameters of Pulsed Doppler indices have been used to evaluate diastolic function in patients with ESRD including transmitral diastolic filling velocity which reflects filling dynamics of the left atrium (LA) and has been shown to be load dependent in subjects with various cardiac diseases. 
Measurement of dry weight is a common approach to design fluid management for patients with ESRD on regular HD.  Quantitive measurements of preload reduction on the LV Doppler velocities in systole and diastole is not a common practice in these patients. Also, the relationship of these measurements to the changes of systolic blood pressure during HD has not been adequately investigated.
The aim of this study was to assess the following:
- to examine the effect of net volume ultrafiltrate loss (measured by the HD machine) during HD on the diastolic and systolic pulsed Doppler indices of LV and the systolic flow of the aortic valve and,
- to validate the best derived parameter of Doppler indices in order to predict those patients who may have tendency to develop hypotension during HD.
| Materials and Methods|| |
The study population consisted of 52 patients, 34 male and 18 female, with a mean age of 45.5 ± 13 years. The study was performed in the renal dialysis and cardiac units at the Salmanyia Medical Complex, Bahrain, over a period of twelve months.
Patients included are those with ESRD on regular HD for more than six months, had normal LV function on echocardiogram with no clinical evidence of coronary artery disease based on history, symptoms of angina and normal twelve-lead electrocardiogram (ECG). Each patient, before enrolment in the study, signed a consent form. The study protocol was approved by the ethics committee of both hospitals.
Patients were excluded from the study if they were not willing to participate, if they had severe mitral or aortic valve disease, if they had LV systolic dysfunction with LV ejection fraction of less than 50% and/or if they were known to have coronary artery disease.
The study protocol
Before entry in the study, each patient underwent detailed clinical evaluation complemented with 12-lead ECG and calculated body mass index (BMI). History of diabetes mellitus (DM), hypertension, hyperlipidemia and current medications were recorded. The study patients were not allowed to take any medications up to six hours before commencement the dialysis session in order to eliminate the effect of the medication on the study outcome.
Overnight fasting blood specimens were drawn from each patient to measure the fasting blood sugar, lipid profile including total cholesterol, low density lipoprotein (LDL), high density lipoprotein (HDL) and triglyceride (TG) and hemoglobin level (Hb) levels. Patients were regarded hyperlipidemic if LDL level was more than 160 mg/dL (4.1 mmol/L). 
Pulsed Doppler echocardiogram was performed using Hewlett parker echo system (mode 5500) incorporating a 2.0-2.5 mhz Phase array transducer. The M mode measurements were used for the LV cavity and wall thickness, left atrial diameter, and LV ejection fraction (EF). Echocardiographic measurements were carried out according to the recommendation of the American Society of Echocardiography.  Pulsed Doppler measurements of the LV diastolic velocity were made in the apical four chamber view. They included; E wave of early diastolic filling of LV in cm/s, A wave of the atrial contraction in cm/s, the E/A ratio, isovolumic relaxation time in ms, Deceleration Time (DT) of the E wave in msec and the Time velocity integral of aortic valve velocity integral (TVI) in cm. The diameter of the inferior vena cava (VCD) in mm on sub-costal view was obtained at the end of expiration.  All the 2-D echo and pulsed Doppler readings were taken as a mean of three consecutive cardiac cycles and were calculated by a second operator who was blinded for the clinical status of the patients.
During a HD session, the heart rate and blood pressure (BP) were recorded for each patient every 15 minutes automatically and monitored for cardiac events such as hypotension (defined as reduction of systolic BP < 90 mmHg), arrhythmia or chest pain. Immediately after the HD session, the heart rate, BP, net volume loss of the ultrafiltate in liters and duration of dialysis session in hours as measured by the machine were recorded. A second post-dialysis pulsed Echo Doppler echocardiogram was performed immediately after the HD session. The measured M mode and 2-D values and pulsed Doppler data were tabulated.
The study population (n = 52) was divided into two groups according to the net volume fluid loss at the end of the dialysis session: Group I, (n = 25) with net fluid loss of less than two liters and Group II, (n=27) with net fluid loss > 2 liters. The clinical data and the echo Doppler data were all tabulated and analyzed for each patient.
Fifty healthy normotensive volunteers with normal renal function, without history of cardiovascular disease were enrolled as controls for 2-D echo and Pulsed Doppler examination. The findings were compared with those of the study population.
All quantitative values were expressed as mean ± standard deviation. The two-tailed paired Student's t test was used for comparison of pre- and post-dialysis parameters within the same group. Chi-square analysis was applied for qualitative data. The probability value (P) less than 0.05 was considered significant.
| Results|| |
Adult patients with ESRD on regular HD were enrolled into the study; 52 out of 64 fulfilled the inclusion criteria. Of the 12 patients who were excluded four had significant mitral or aortic valve disease, seven had coronary artery disease and/or left ventricle dysfunction on echo and one was not willing to participate. The 52 study patients were divided into two groups: Group I (n = 25) where ultrafiltration was less than two liters at the end of the HD session and, Group II (n = 27) where ultrafiltration was equal to or more than two liters. The characteristics of the whole study population, the two sub-groups and the control group were comparable and there was no statistical difference between them [Table 1] and [Table 2]. The etiology of ESRD in the study population was diabetic nephropathy in twelve, chronic glomerulonephritis in ten, interstitial nephritis in ten, lupus nephritis in five, adult polycystic kidney disease in two and unknown in thirteen patients. There was no statistical difference between Group I and II in regard to age, sex, predialysis heart rate and blood pressure, body mass index, hemoglobin level, prevalence of diabetes, hypertension and hyperlipidemia and the duration of the dialysis session [Table 2] and [Table 3]. The hydration status was similar in both groups, as assessed by pre-dialysis measurement of inferior vena cava diameter (VCD) which was 10.6 ± 2.5 mm and 10.2 ± 2.9 mm in Groups I and II respectively [Table 3] and [Table 4].
The medications of each patient were recorded. All patients were on oral one alpha and calcium carbonate tablets. Other oral medications were beta blockers in 32, calcium channel blockers in 38, cholesterol lowering agents (statin) in 14 and alpha blockers in four patients.
Eighteen patients were on oral hypoglycemic drugs and four were on insulin injections.
The LV diastolic velocities
In the study population, the analysis of the LV diastolic Doppler velocities showed three different patterns. The pattern of abnormal relaxation was found in 40 patients (78%) with E/A ratio reversal of < 1 with prolonged DT of E wave. Pattern of constrictive type was seen in six patients (10%) while in another six patients (10%), a pseudonormal pattern was seen.
In Group I, there was no statistical difference between pre- and post- mean values of the blood pressure or heart rate while there was a significant drop in the systolic blood pressure in patients in Group II from 137.7 ± 28 down to 112.7 ± 26 mmHg (p< 0.01) [Table 3] and [Table 4]. The differences between the pre- and postmean values of the M mode echo parameters were not statistically significant concerning the LV end-systolic dimension (LVESD), septal wall thickness (IVS) and posterior wall thickness (PW), in the two groups.
In Group II, there was a significant increment of mean left ventricular ejection fraction (LVEF) from 56.6 ± 6.7% to 60.8 ± 6.4% and significant reduction in the LV end-diastolic dimension (LVEDD) from 4.6 to 4.28 cm (p< 0.05). The VCD reduced from 10.2 ± 2.9 to 8.4 ± 2.3 mm (p< 0.05) [Table 3] and [Table 4].
The analysis of pulsed Doppler data in Group I showed that the differences between the preand post-HD Doppler variables were not statistically significant although there was a trend of velocity reduction noted for all the variables except for the DT [Table 5]. In group II, the difference in the mean values between the post and pre-HD pulsed Doppler variables were of statistical significance in regards to reduction of the mean E wave velocity by 32 mm (42%), E/A ratio by 0.14 and time velocity integral of aortic valve by 6.3 cm (26%). The prolongation of DT of the E wave was significantly high, by 43 ms (18%), as shown in [Table 6].
Left ventricular hypertrophy
The total number of patients with LV hypertrophy (LVH) shown by the 12-lead ECG was 26 (50%) in the study population. The total number of patients who had LVH on M mode was 36 (69%). All patients, except one, with LVH on M mode had abnormal relaxation pattern on pulsed Doppler.
Clinical events during dialysis
In the study population, 11 patients (21%) developed episode(s) of intra-dialysis hypotension towards the end of the dialysis session. None of them had syncope, giddiness or angina. There was no need to discontinue any HD session. There was an episode of atrial fibrillation in one patient.
Among the patients with hypotension, eight patients (8/27, 29%) patients were in Group II and three (3/25, 12%) were in Group I. Analysis of pulse Doppler variables for patients who developed intra-dialysis hypotension from those who did not showed that the mean DT of the E wave was 246 ms ± 40 in Group I vs. 210 ± 15 ms in Group II (p< 0.01) and the E/A wave ratio was 0.7 ± 0.3 in Group I vs 1.01 ± 0.25 in Group II, respectively (p< 0.001).
| Discussion|| |
In this study, the impact of preload reduction during HD on the pulse Doppler indices of LV diastolic flow was evaluated. The diastolic flow of the LV was of abnormal relaxation pattern (type I) in 78% of the study population. This finding was seen in the normotensive as well as the hypertensive patients with or without LVH. This suggests that ESRD in itself may be the cause of the abnormal relaxation pattern seen in these patients. Similar findings were observed by other investigators with the reported incidence of abnormal relaxation pattern being 77%. ,
The pre-dialysis hydration status was similar in both groups as evidenced by the Inferior vena caval diameter on 2-D echocardiogram. The post-dialysis data of M mode echo and Pulsed Doppler indices in the study patients showed a trend towards reduction of all Doppler indices except DT of E wave, which was prolonged. In Group II, the reduction in the mean value of E wave velocity, E/A ratio and Time velocity integral of aortic valve (TVI) and the prolongation of DT of E wave were of statistical significance. Such findings have been reported earlier in the literature. ,, The systolic and diastolic Pulsed Doppler velocity reduction in the hypotensive patients in our study population is probably due to the significant reduction of venous return by 17%, as evidenced by the diameter of the inferior vena cava, in Group II patients. This may suggest that the reduction in the preload during dialysis is possibly the main mechanism responsible for the development of acute changes in the pulsed Doppler indices.
The mean ultrafilitration volume at the end of HD was 2.9 liters in Group II, which was 2.3 folds higher than in Group I patients. This probably led to a significant reduction in E wave velocity, E/A wave ratio, inferior vena cava diameter and Time velocity integral of aortic valve, in Group II. These findings are in agreement with observations noted in the lite rature by others. ,
The post-dialysis LV end-diastolic dimension was significantly reduced by 0.4 cm coupled with an increment of the left ventricular ejection fraction by 4.2 % in Group II. This is probably due to the reduction of the LV end-diastolic volume, which is probably caused by the reduction in the after load and the improvement in the emptying of the LV. This was in agreement with others where an overall improvement of LVEF was noted. ,,
Hypotension with SBP of less than 90 mmHg was observed in more than 29% of Group II patients, which may be due to reduction of venous return caused by the rapid removal of large volume (> 2.9 liters) during dialysis. One may argue that autonomic dysfunction, which is common among diabetics, may contribute to the episodes of hypotension.  However; the intra-dialysis hypotension is most likely of multi-factorial etiology as it was observed in 12% of patients in Group I as well.
Hypovolemia is mostly due the imbalance between the amount of fluid removed and the refilling capacity of the intravascular compartment.  The most powerful predictors for those patients who had intra-dialysis hypotension were the DT of E wave more than 246 msec and the E/A ratio less than 0.7 on the pulsed Doppler indices. This observation is in keeping with previous reports in the literature. ,, In this study, majority of the patients with intradialysis hypotension had abnormal relaxation pattern (Type I) despite the similarity with those who stayed normotensive, with respect to hydration status, LVH and patients with diabetes mellitus. This finding is different from other previous reports where intra-dialysis hypotension was observed exclusively among diabetic patients. 
Limitations of the study
Patients with ischemic heart disease, valve disease or low LV ejection fraction for any other reason were excluded in order to eliminate potential errors of measuring the Doppler indices; thus, the study represents one portion, but not all, ESRD patients.
| Conclusion|| |
Pulsed Doppler data showed that the preload reduction gauged by the net fluid loss during HD is directly proportional to the reduction of LV early diastolic filling velocity and E/A wave ratio. Prolonged DT of E of more than 246 msec and E/A ratio of less than 0.7 on predialysis pulsed Doppler echocardiogram are probably powerful predictors of intra-dialysis hypotension and necessitate careful assessment of the patient, pre-, intra- and post-dialysis, especially on planning large preload reduction.
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Department of Nephrology, Salmanyia Medical Complex, Arabian Gulf University, P.O. Box 18725 Manama
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]