Preoperative levosimendan infusion in combined aortic valve and coronary bypass surgery.

BACKGROUND: Cardiopulmonary bypass may have detrimental effects on intestinal function and decrease the concentrations of the active, long-acting metabolites of levosimendan, an inodilator used to improve cardiac function. The aim of this study was to evaluate the haemodynamic effects of preoperative levosimendan in patients undergoing high-risk cardiac surgery. METHODS: Twenty-four patients were randomized to receive levosimendan (12 µg bolus followed by an infusion of 0.2 µg kg(-1) min(-1)) or a placebo 24 h before surgery. The inclusion criteria were left ventricular ejection fraction (LVEF) <50% or LV hypertrophy indicated by a wall thickness of >12 mm. Haemodynamics were recorded every hour for 24 h (pulmonary artery catheter) and daily until postoperative day 4 (whole-body impedance cardiography). Doppler echocardiography with tissue Doppler imaging was used to assess systolic and diastolic cardiac function. RESULTS: The cardiac index (CI) and stroke volume index (SI) were higher in the levosimendan group (LG) for the 4 day postoperative period (P<0.05); on the fourth postoperative day, the CI was 3.0 litre m(-2) min(-1) in the LG compared with 2.4 litre m(-2) min(-1) in the control group (CG) and the SI was 30 vs 25 ml m(-2), respectively. The LVEF measured at baseline and on the fourth postoperative morning decreased in the CG, but was maintained in the LG. CONCLUSIONS: Levosimendan improved haemodynamics compared with a placebo in patients undergoing high-risk cardiac surgery. The concentrations of levosimendan's metabolites were higher compared with earlier studies using perioperative dosing.

Computational and physiological background of the baroreflex sensitivity.

All the commonly used definitions of baroreflex sensitivity (BRS) are based on a slope of linear relationship between systolic blood pressure and pulse interval (R-R interval). However, heart rate (HR) and R-R interval bear an inverse non-linear relationship, which distorts determination of BRS when different HR levels are present. We analysed data of 117 healthy, normal-weight, non-smoking men and women aged 23-77 to show how BRS depends on the initial HR. In this data, 43% of variation in BRS is solely explained by HR. Comparisons of BRS between patients with different HR and even within the same patient with changing HR (e.g. tilt-table test and nocturnal changes in HR) should be questioned. Consideration of the baseline HR is even more crucial, if the patients are subjected to an intervention affecting not only baroreflexes but also HR. If baseline HR is not taken into account, using the R-R interval in the estimation of BRS may lead to partially misleading values and possibly also to misinterpretation of physiological processes. We discuss alternative definitions of BRS to allow varying HRs.

The prognostic value of haemodynamic parameters in the recovery phase of an exercise test. The Finnish Cardiovascular Study.

We tested the hypothesis that the change from the peak to recovery values of systolic arterial pressure (SAP recovery) and rate-pressure product (RPP recovery) can be used to predict all-cause and cardiovascular mortality, as well as sudden cardiac death (SCD) in patients referred to a clinical exercise stress test. As a part of the Finnish Cardiovascular Study (FINCAVAS), consecutive patients (n=2029; mean age+/-SD=57+/-13 years; 1290 men and 739 women) with a clinically indicated exercise test using a bicycle ergometer were included in the present study. Capacities of attenuated SAP recovery, RPP recovery and heart rate recovery (HRR) to stratify the risk of death were estimated. During a follow-up (mean+/-s.d.) of 47+/-13 months, 122 patients died; 58 of the deaths were cardiovascular and 33 were SCD. In Cox regression analysis after adjustment for the peak level of the variable under assessment, age, sex, use of beta-blockers, previous myocardial infarction and other common coronary risk factors, the hazard ratio of the continuous variable RPP recovery (in units 1000 mm Hg x b.p.m.) was 0.85 (95% CI: 0.73-0.98) for SCD, 0.87 (0.78-0.97) for cardiovascular mortality, and 0.87 (0.81 to 0.94) for all-cause mortality. SAP recovery was not a predictor of mortality. The relative risks of having HRR below 18 b.p.m., a widely used cutoff point, were as follows: for SCD 1.28 (0.59-2.81, ns), for cardiovascular mortality 2.39 (1.34-4.26) and for all-cause mortality 2.40 (1.61-3.58). In conclusion, as a readily available parameter, RPP recovery is a promising candidate for a prognostic marker.

The influence of hemodynamic factors on left ventricular mass.

We evaluated the relationship between the variability in the left ventricular mass index (LVMI) and different hemodynamic factors. LVMI was associated with blood pressure and, in one subgroup, strongly to arterial pulse wave velocity (PWV). High physical activity was connected to increased LVMI, and a combination of low stroke index (SI) and high heart rate (HR) to decreased LVMI.

Potassium channel KCNH2 K897T polymorphism and cardiac repolarization during exercise test: The Finnish Cardiovascular Study.

OBJECTIVE: Cardiac repolarization is regulated, in part, by the KCNH2 gene, which encodes a rapidly activating component of the delayed rectifier potassium channel. The gene expresses a functional single nucleotide polymorphism, K897T, which changes the biophysical properties of the channel. The objective of this study was to evaluate whether this polymorphism influences two indices of repolarization--the QT interval and T-wave alternans (TWA)--during different phases of a physical exercise test. MATERIAL AND METHODS: The cohort consisted of 1,975 patients undergoing an exercise test during which on-line electrocardiographic data were registered. Information on coronary risk factors and medication was recorded. The 2690A>C nucleotide variation in the KCNH2 gene corresponding to the K897T amino acid change was analysed after polymerase chain reaction with allele-specific TaqMan probes. RESULTS: Among all subjects, the QTc intervals did not differ between the three genotype groups (p> or =0.31, RANOVA). Women with the CC genotype tended to have longer QT intervals during the exercise test, but the difference was statistically significant only at rest (p = 0.011, ANOVA). This difference was also detected when the analysis was adjusted for several factors influencing the QT interval. No statistically significant effects of the K897T polymorphism on TWA were observed among all subjects (p = 0.16, RANOVA), nor in men and women separately. CONCLUSIONS: The K897T polymorphism of the KCNH2 gene may not be a major genetic determinant for the TWA, but the influence of the CC genotype on QT interval deserves further research among women.

Pulse wave velocity reference values in healthy adults aged 26-75 years.

The stiffening of arteries is associated with various cardiovascular diseases. Arterial stiffening can be studied utilizing arterial pulse wave velocity (PWV), but the absence of reliable reference values for PWV has limited its use in clinical practice. The aim of this study was to establish a range of reference values for PWV. PWV was examined by measuring the time difference of systolic pulse waves in arteries from the aortic arch to the popliteal artery using whole-body impedance cardiography (ICG). The study population consisted of 799 individuals (age range 25-76 years), 283 of whom had no evidence of cardiovascular disease, and a low burden of risk factors was selected to represent an apparently healthy population. In healthy study population, PWV was higher in males (8 x 9 +/- 1 x 8 m s(-1)) than females (8 x 1 +/- 2 x 0 m s(-1), P<0 x 001). Young males had lower PWV values than old males. Correspondingly, young females also had lower PWV values than old females. PWV was clearly associated with age, and PWV was higher in young and middle-aged males than in females. There was no statistically significant difference between old males and females in PWV. In conclusion, whole-body ICG provides a practical method for PWV measurement. Reference values can be useful in the clinical management of patients, especially in detecting early vascular disease or an increased risk of cardiovascular complications.

Maternal haemodynamics in pre-eclampsia compared with normal pregnancy during caesarean delivery.

OBJECTIVE: To determine how pre-eclampsia modifies maternal haemodynamics during caesarean delivery. DESIGN: Prospective study. SETTING: Tampere University Hospital, Finland. POPULATION: Ten pre-eclamptic parturients and ten healthy parturients with uncomplicated pregnancies scheduled for elective caesarean section under spinal anaesthesia. METHODS: Haemodynamic parameters were assessed by whole-body impedance cardiography noninvasively. MAIN OUTCOME MEASURES: Stroke index (SI), heart rate (HR), cardiac index (CI), systemic vascular resistance index (SVRI) and mean arterial pressure (MAP) were recorded before operation, continuously during caesarean section, during the period of dissipation of anaesthesia and on the second to fifth postpartum day. RESULTS: Baseline haemodynamics in women with pre-eclampsia differed significantly from healthy women in higher SVRI and MAP and lower SI and CI. In women with pre-eclampsia, preload infusion increased both SI and HR, causing a significant rise in CI, while in healthy parturients, only HR rose. In both the groups, spinal blockade reduced SVRI but CI remained stable. At the moment of delivery, CI increased in both groups. In uncomplicated pregnancies, both SI and HR increased, but in women with pre-eclampsia, SI was not altered and the rise in CI was due to an increase in HR only. After the reversal of anaesthesia, haemodynamics in the control group returned to baseline values, whereas in women with pre-eclampsia, SI and CI fell to levels that were significantly lower than the levels observed before surgery. CONCLUSIONS: In women with pre-eclampsia, inability to increase SI at the moment of delivery may suggest dysfunction of the left ventricle to adapt to volume load caused by delivery and prompts concern for the increased risk of pulmonary oedema.

Ten-year prognosis of Puumala hantavirus-induced acute interstitial nephritis.

Nephropathia epidemica (NE) is a hemorrhagic fever with renal syndrome caused by Puumala hantavirus. Its long-term prognosis is considered favorable. There are, however, some reports about subsequent hypertension, glomerular hyperfiltration, and proteinuria after previous hantavirus infection. Therefore, we studied 36 patients 5 and 10 years after acute NE, with 29 seronegative controls. Office blood pressure, ambulatory 24-h blood pressure (ABP), glomerular filtration rate (GFR), and proteinuria were examined. Hypertensive subjects were defined as those patients having increased ambulatory or office blood pressure, or receiving antihypertensive therapy. Office blood pressure was used to define hypertension only if ABP was not determined. At 5 years, the prevalence of hypertension was higher among NE patients than in controls (50 vs 21%, P=0.020). At 10 years, the difference between the groups was no more significant (39 vs 17%, P=0.098). Five years after NE, patients showed higher GFR (121+/-19 vs 109+/-16 ml/min/1.73 m(2), P=0.012) and urinary protein excretion (0.19 g/day, range 0.12-0.38 vs 0.14 g/day, range 0.09-0.24, P=<0.001) than controls. At 10 years, there were no more differences in GFR or protein excretion between the groups (GFR: 113+/-20 vs 108+/-17 ml/min/1.73 m(2), P=0.370; proteinuria: 0.14 g/day, range 0.07-0.24 vs 0.13 g/day, range 0.06-0.31, P=0.610). In conclusion, the 10-year prognosis of NE is favorable, as glomerular hyperfiltration and slight proteinuria detected at 5 years disappeared during the longer follow-up. However, the possibility exists that NE may predispose some patients to the development of hypertension.

A new method for measuring the ballistocardiogram using EMFi sensors in a normal chair.

Ballistocardiography is a non-invasive technique for the assessment of cardiac function. We built a measurement setup to measure the ballistocardiogram from a normal chair using EMFi sensors. The ballistocardiogram is recorded from a subject sitting on the chair. The measured signal is amplified by a specially-designed charge amplifier and digitized by a circulation monitor. A PC provides a user interface for the measurement devices, records the data and displays the results. Impedance cardiography and ECG serve as reference measurements for the ballistocardiography. To test the system, one healthy 24-year-old male and one healthy 22-year-old female were measured. It is concluded that the ballistocardiogram waveforms described in the literature can be recognized from the EMFi signal measured from a normal chair.

Effects of hypertonic saline (7.5%) on extracellular fluid volumes in healthy volunteers.

This study evaluated the effects of 7.5% saline on plasma and other extracellular fluid volumes. After baseline measurements, eight healthy postmenopausal female volunteers received 4 ml.kg-1 of hypertonic saline over 30 min. After the fluid infusion, the volunteers were studied for 60 min. Plasma volume was measured using a dilution of 125-iodine-labelled human albumin. Extracellular water and cardiac output were measured by whole body impedence cardiography. The infused volume was 4 ml.kg-1 (average 260 ml). Plasma volume increased rapidly during the infusion (mean +/- standard deviation, 442 +/- 167 ml). At the end of the 1-h follow-up period, plasma volume had increased by on average 465 ml (SD 83). The increase of extracellular water at the end of infusion and at the end of study was 650 ml (SD 93) and 637 ml (SD 192), respectively. The highest serum sodium recorded in the volunteers was 158 mmol.l-1. The effect of 7.5% saline on plasma volume was rapid and lasted for at least 1 h. Plasma volume remained elevated by more than the infused volume at the end of the study. The increase in plasma and extracellular fluid volumes was partly achieved by mobilizing intracellular water to extracellular compartment.

Isolated ultrafiltration affects dynamic vectorcardiographic ischemia monitoring parameters.

AIMS: The present study was undertaken to assess the role of isolated ultrafiltration (UF phase) and hemodialysis with minimal ultrafiltration (HD phase) in changes in parameters reflecting myocardial ischemia: QRS vector difference (QRS-VD), ST change vector magnitude (STC-VM) and ST vector magnitude (ST-VM6) registered by MIDA (myocardial infarction dynamic analysis). PATIENTS AND METHODS: Twelve patients on maintenance hemodialysis were first ultrafiltrated for 2.5 h without dialysis (UF) followed by a 2.5-hour session of hemodialysis with minimal ultrafiltration (HD). Computerized vectorcardiography (VCG) was used for on-line dynamic analysis of ST segment and QRS complex changes. Blood volume (BV) changes were monitored non-invasively and continuously with the CRIT-LINE instrument. Whole-body bioelectric impedance analysis (BIA) was used for extracellular water (ECW) estimation. RESULTS: During the UF phase QRS-VD and STC-VM showed a statistically significant increasing linear trend (time effect for both QRS-VD and STC-VM p < 0.0001, while no changes were noted in ST-VM6; time effect p = 0.986). During the HD phase none of these parameters changed (time effect for QRS-VD p = 0.855, for STC-VM p = 0.275 and for ST-VM6 p = 0.976). During the UF, phase changes in QRS-VD were in close relation to those in ECW. CONCLUSION: Isolated ultrafiltration leads to an increase in the VCG ischemia monitoring parameters QRS-VD and STC-VM. The increase of QRS-VD is related to changes in ECW. Hemodialysis with minimal ultrafiltration has no effect on VCG ischemia monitoring parameters.

Effects of hypertonic 75 mg/ml (7.5%) saline on extracellular water volume when used for preloading before spinal anaesthesia.

BACKGROUND: Prevention of hypotension during spinal anaesthesia is commonly achieved using fluid preloading. This may result in a substantial amount of excess free water retained in the body after spinal anaesthesia. We aimed to evaluate the effects of 7.5% hypertonic saline on extracellular water volume and haemodynamics when used for fluid preloading before spinal anaesthesia. METHODS: This randomised double-blind study evaluated the effects of 75 mg/ml (7.5%) hypertonic saline (HS) on extracellular water volume and haematocrit in patients undergoing arthroscopy or other lower limb surgery under spinal anaesthesia. Amounts of 1.6 ml/kg of HS (20 patients) or 13 ml/kg of 9 mg/ml normal saline (20 patients) were administered for preloading before spinal anaesthesia with a 10 mg dose of 0.5% hyperbaric bupivacaine. Etilefrine was administered in order to maintain mean arterial pressure (MAP) at >or=80% of its baseline value. Whole-body impedance cardiography-derived cardiac index (CI) and extracellular water (ECW) were measured. RESULTS: There were no significant differences in demographic data or in the number of blocked segments. ECW remained similar in both groups despite the much smaller amount of infused free water in the HS group. There were no significant differences between the groups in CI values during the study. The amount of etilefrine administered was similar in the treatment groups. Dilution of haematocrit was also similar in both groups. CONCLUSION: Hypertonic 75 mg/ml (7.5%) saline is an alternative for preloading before spinal anaesthesia in situations where excess free water administration is not desired. It is effective in small doses of 1.6 ml/kg, which increase the extracellular water, plasma volume and cardiac output, and thus maintain haemodynamic stability during spinal anaesthesia.

TERVA: system for long-term monitoring of wellness at home.

Long-term monitoring of physiological and psychosocial variables in out-hospital conditions would be beneficial for investigating changes in wellness status of an individual or to understand interaction between physiological and behavioral processes. We aimed to design a personal wellness monitoring system (TERVA), which would allow monitoring of wellness-related variables at home for several weeks or even months. The designed TERVA system runs on a laptop computer and interfaces with different measurement devices through a serial interface. Measured variables include beat-to-beat heart rate, motor activity, blood pressure, weight, body temperature, respiration, ballistocardiography, movements, and sleep stages. In addition, self-assessments of daily well-being and activities are stored by keeping a behavioral diary. To test the system, one healthy man used the system for 10 weeks. The system was successfully applied in out-hospital conditions. The success rate of the measurements was 70-91%, depending on the variable under consideration. The pilot study indicated that the recorded data accurately reflected the health status of the subject. The TERVA system provides a method to record and investigate wellness-related data over several weeks, or even months, outside the hospital among subjects capable of using a personal computer. Several applications of the system are discussed.

Effects of hypertonic saline (7.5%) on extracellular fluid volumes compared with normal saline (0.9%) and 6% hydroxyethyl starch after aortocoronary bypass graft surgery.

OBJECTIVE: To compare the effects of hypertonic (7.5%) saline (HS), normal (0.9%) saline (NS), and 6% hydroxyethyl starch (HES) on extracellular fluid volumes in the early postoperative period after cardiopulmonary bypass. DESIGN: A prospective, randomized, double-blind study. SETTING: University teaching hospital. PARTICIPANTS: Forty-eight patients scheduled for elective coronary artery bypass graft surgery. INTERVENTIONS: Patients were randomly allocated to receive 4 mL/kg of HS, NS, or HES during 30 minutes when volume loading was needed during the postoperative rewarming period in the intensive care unit. Plasma volume was measured using a dilution of iodine-125-labeled human serum albumin. Extracellular water and cardiac output were measured by whole-body impedance cardiography. MEASUREMENTS AND MAIN RESULTS: Plasma volume had increased by 19 +/- 7% in the HS group and by 10 +/- 3% in the NS group (p = 0.001) at the end of the study fluid infusion. After 1-hour follow-up time, the plasma volume increase was greatest (23 +/- 8%) in the group receiving HES (p < 0.001). The increase of extracellular water was greater than the infused volume in the HS and HES groups at the end of the infusion. One-hour diuresis after the study infusion was greater in the HS group (536 +/- 280 mL) than in the NS (267 +/- 154 mL, p = 0.006) and HES groups (311 +/- 238 mL, p = 0.025). CONCLUSION: The effect of HS on plasma volume was short-lasting, but it stimulated excretion of excess body fluid accumulated during cardiopulmonary bypass and cardiac surgery. HS may be used in situations in which excess free water administration is to be avoided but the intravascular volume needs correction.

Can stroke volume and cardiac output be determined reliably in a tilt-table test using the pulse contour method?

The applicability of the finger pressure-derived pulse contour (PC) technique was evaluated in the measurement of stroke volume (SV), cardiac output (CO) and their changes in different phases of the tilt-table test. The reference method was whole-body impedance cardiography (ICG). A total number of 40 physically active patients, aged 41 +/- 19 years, were randomly chosen from a pool of 230. Specifically speaking, 20 of the patients experienced (pre)syncope (tilt+ patients) during the head-up tilt (HUT), and 20 did not (tilt-). A total number of three measurement periods, 30-60 s each, were analysed: supine position, 5 min after the commencement of HUT, and 1 min before set down. SV and CO values measured by PC underestimated significantly those measured by ICG (biases +/- SD 19 +/- 14 ml and 1.55 +/- 1.14 l min-1, respectively) in agreement with earlier reports. The bias between the methods was almost the same in the different phases of the test. However, the SD of the bias was bigger for tilt+ (P < 0.05). When the bias between the methods was eliminated by scaling the first measurement to 100%, the agreement between the methods in the second and third measurements was clearly better than without scaling. Both methods showed a physiological drop in SV after the commencement of HUT. These results indicate that PC suffices in tracking the changes in CO and SV, but for absolute values it is not reliable.

The comparison of hypertonic saline (7.5%) and normal saline (0.9%) for initial fluid administration before spinal anesthesia.

Hypertonic saline can be used for initial fluid administration before spinal anesthesia. It is effective in small-volume fluid resuscitation. This randomized double-blinded study compared the effects of 7.5% hypertonic saline (HS) and 0.9% normal saline (NS) in doses containing 2 mmol/kg of sodium in 40 ASA physical status I-II patients undergoing arthroscopy or other lower limb surgery under spinal anesthesia. We infused 1.6 mL/kg of HS or 13 mL/kg of NS for initial fluid administration before spinal anesthesia induced with a 10-mg dose of 0.5% hyperbaric bupivacaine. Etilefrine was administered to maintain mean arterial pressure at > or =80% of its control value. Systolic and diastolic blood pressure, heart rate, and cardiac index did not differ between the groups, and the amount of etilefrine administered was similar in the treatment groups. In all our patients, the plasma sodium concentrations were within the normal range after surgery and serum osmolality was within the normal range after spinal anesthesia. The time and the volume of the first micturition were similar in both groups, despite the much smaller amount of infused free water in the HS group. We conclude that 7.5% HS was as good as NS for the initial fluid administration before spinal anesthesia when the amount of sodium was kept unchanged.

Hemodialysis causes changes in dynamic vectorcardiographic ischemia monitoring parameters.

AIMS: The aim of this study was to establish whether changes in parameters reflecting myocardial ischemia QRS vector difference (QRS-VD), ST change vector magnitude (STC-VM) and ST vector magnitude (ST-VM6) during hemodialysis (HD) registered by MIDA (myocardial infarction dynamic analysis) are related to changes in blood volume (BV), extracellular water (ECW) and blood biochemistry. PATIENTS AND METHODS: Fifteen hemodialysis (HD) patients were studied. Computerized vectorcardiography was used for on-line dynamic analysis of ST segment and QRS complex changes. BV changes were monitored non-invasively and continuously with the CRIT-LINE instrument. Bioelectric impedance analysis (BIA) was used for ECW estimation. Blood samples were taken before and after hemodialysis for hemoglobin (B-Hb), hematocrit (B-Hcr), sodium (P-Na), chloride (P-Cl), magnesium (P-Mg), potassium (P-K), ionized calcium (P-iCa), phosphate (P-Pi) and astrup measurement. RESULTS: During dialysis treatment QRS-VD, ST-VM6 and STC-VM did not change in parallel. According to the linear mixed model, no statistically significant changes were noted in ST-VM6 during dialysis (time effect p = 0.5635). On the other hand, QRS-VD and STC-VM showed a statistically significant linear trend (time effect for QRS-VD p = 0.0001 and for STC-VM p = 0.0004). Changes in both ECW and BV affected the change in QRS-VD and in STC-VM. CONCLUSION: During HD treatment changes in the vectorcardiographic ischemia monitoring parameters QRS-VD and STC-VM are mostly related to ECW and BV changes and may give a false positive impression of myocardial ischemia. The ST-VM6 trend is less markedly influenced by volume changes.

Comparison of bioimpedance and radioisotope methods in the estimation of extracellular water volume before and after coronary artery bypass grafting operation.

To estimate extracellular water volume (ECW) changes in connection with coronary artery bypass grafting operation, simultaneous ECW estimations by 51Cr-EDTA dilution and whole-body bioimpedance techniques were performed in 15 patients. The assessments of ECW were compared with patients' weighing results. Whole-body bioimpedance-derived ECW correlated significantly with 51Cr-EDTA dilution-based ECW in the pre-operative period (r=0.74; P<0.005); the bias was 0.2 +/- 1.1 l (+/-SD). In the post-operative period, the agreement between these methods was poor, the bias being 0.5 +/- 2.5 l, and no significant correlation between the methods was found (r=0.38; P>0.05). Whole-body bioimpedance-derived ECW changes correlated significantly with weight changes of the patient induced by the operation (r=0.52; P<0.05). 51Cr-EDTA dilution-based ECW changes correlated neither with weight changes (r=0.33; P>0.05) nor with bioimpedance-derived ECW changes (r=0.03; P>0.05). Alterations in radioisotope tracer distribution and loss of it due to blood leakage in the post-operative period were presumed to explain the discrepancy between dilution technique and weighing results. The results suggest that bioimpedance is a useful non-invasive method for assessment of extracellular volume changes induced by coronary artery bypass grafting operations. 51Cr-EDTA dilution-based ECW determination is not suitable in related conditions.

Segmental composition of whole-body impedance cardiogram estimated by computer simulations and clinical experiments.

Whole-body impedance cardiography (ICGWB) has been proposed as a feasible means of measuring cardiac output (CO). However, the source distribution of heart-related impedance variations in the whole body is not known. To establish how much of a signal originates in each segment of the body and what the contribution of each is to stroke volume (SV) in ICGWB, impedance in the extremities and trunk were investigated in 15 healthy volunteers. In addition, the theoretical measurement properties of ICGWB were studied using a computer model of the whole-body anatomy as a volume conductor. The model confirmed the expected result that most of the basal impedance originates from the extremities. Clinical experiments revealed that the heart-related amplitude variations in the ICGWB signal originate more evenly from various body segments, the trunk slightly more than the arms or legs. The heart-related ICGWB signal represents a weighted sum of segmental pulsatile events in the body yielding physiologically meaningful data on almost the whole circulatory system.