Pressure Volume Index Research Articles

Atrial function in heart transplant recipients operated with the bicaval technique

Objectives: In heart transplantation (HTx) with the bicaval technique the whole right atrium (RA) is donor tissue while the left atrium (LA) consists of both donor and recipient tissue. The aims of the study were to describe atrial function in comparison with healthy controls and to identify determinants of dysfunction. Design: Forty-three patients and 30 controls were retrospectively included. Echocardiography was performed within 24 h of right heart catheterization (RHC) (HTx recipients). Results: The peak longitudinal atrial systolic strain (ɛ) described the atrial reservoir function. The LA and RA reservoir function were reduced versus controls (LA-ɛ 18 ± 8 versus 44 ± 10%; RA-ɛ 22 ± 10 versus 69 ± 17%, p < 0.001). There were moderate relationships between atrial-ɛ and ventricular filling pressure (r = −0.64 for LA-ɛ; r = −0.57 for RA-ɛ). In a multiple regression analysis the LA-ɛ was determined by pulmonary capillary wedge pressure (PCWP) and LA minimum volume index (r = −0.71) while RA-ɛ was dependent on the right ventricular ɛ (r = −0.77). Conclusions: Atrial reservoir function is markedly reduced in HTx recipients related to elevated PCWP and LA-enlargement in the LA and in the RA impaired longitudinal right ventricular function.

Safety of Intracoronary Human Cord Blood Stem Cells in a Lamb Model of Infant Cardiopulmonary Bypass

One potential approach for advancing univentricular heart surgical palliation outcomes is by stem cell therapy to augment right ventricular function and muscle mass. Whether the stem cell-inclusive cord blood mononuclear cells (CBMNCs) are safe to perfuse into the coronary vasculature during neonatal cardiopulmonary bypass (CPB) is unknown. We evaluated the acute safety, functional effects, and fate of human CBMNCs in a novel model of coronary vasculature delivery in a lamb model of infant CPB. Neonatal lambs were randomized in blinded fashion to receive control (n= 5) or human CD45(+) CBMNCs (8× 10(6) cells/kg body weight, n= 7) treatments during CPB. Aortic cross-clamp time was 40 minutes, with maintenance blood cardioplegia delivered every 10 minutes. Pressure-volume indices were used to measure left ventricular function before CPB and 60 minutes after CPB. CBMNCs were assessed by flow cytometry and immunohistochemistry. CBMNC-treated lambs were hemodynamically stable after CPB, with a decline in left ventricular pressure-volume indices similar to controls. The coronary vasculature was patent on microscopy, without evidence of cell aggregates or clots. Human CD45(+) cells were distributed in high abundance within all cardiac regions, predominantly the right atrium and ventricles, and trafficked beyond endothelial cell layers and between myocytes. CD45(+) cells localized at low incidence in the spleen, liver, lungs, and kidneys, but rarely remained in the circulation (<0.1% of infused cells). Coronary delivery of human CBMNCs during blood-cardioplegic arrest in a lamb model of CPB results in highly abundant myocardial distribution of cells without acute adverse effects on vascular patency and post-CPB cardiac function.

Grading diastolic function by echocardiography: hemodynamic validation of existing guidelines.

BackgroundWhile echocardiographic grading of left ventricular (LV) diastolic dysfunction (DD) is used every day, the relationship between echocardiographic DD grade and hemodynamic abnormalities is uncertain.MethodsWe identified 460 consecutive patients who underwent transthoracic echocardiography within 24 h of elective left heart catheterization and had: normal sinus rhythm, no confounding structural heart disease, no change in medications between catheterization and echo, and complete echocardiographic data. Patients were grouped based on echocardiographic DD grade. Hemodynamic tracings were used to determine time constant of isovolumic pressure decay (Tau), LV end-diastolic pressure (LVEDP) and end-diastolic volume index at a pressure of 20 mmHg (EDVi20).ResultsNormal diastolic function was found in 55 (12.0 %) patients, while 132 (28.7 %) patients had grade 1, 156 (33.9 %) grade 2 and 117 (25.4 %) grade 3 DD. The median value for Tau was 46.9 ms for the overall population (interquartile range 38.6-58.1 ms), with a prevalence of a prolonged Tau (>48 ms) of 47.5 %. While there was an association between DD grade and Tau (p = 0.003), LV dysfunction (ejection fraction <50 %) was more strongly associated with increased Tau (p < 0.001) than was DD grade (p = 0.19). There was also an association between DD grade and LVEDP (p < 0.001), with both LV dysfunction (p = 0.029) and DD grade (p < 0.001) independently associated with LVEDP. Calculated EDVi20 was related to DD grade, but this relationship was driven by findings of paradoxically increased compliance in patients with severe DD.ConclusionsAlthough echocardiographic grading of DD was related to invasive hemodynamics in this population, the relationship was modest.

Dynamic preload indicators decrease when the abdomen is opened.

BackgroundOptimizing cardiac stroke volume during major surgery is of interest to many as a therapeutic target to decrease the incidence of postoperative complications. Because dynamic preload indicators are strongly correlated with stroke volume, it is suggested that these indices can be used for goal directed fluid therapy. However, threshold values of these indicators depend on many factors that are influenced by surgery, including opening of the abdomen. The aim of this study was therefore to assess the effect of opening the abdomen on arterial pressure variations in patients undergoing abdominal surgery.MethodsBlood pressure and bladder pressure were continuously recorded just before and after opening of the abdomen in patients undergoing elective laparotomy. Based on waveform analysis of the non-invasively derived blood pressure, the stroke volume index, pulse pressure variation (PPV) and stroke volume variation (SVV) were calculated off-line.ResultsThirteen patients were included. After opening the abdomen, PPV and SVV decreased from 11.5 ± 5.8% to 6.4 ± 2.9% (p < 0.005, a relative decrease of 40 ± 19%) and 12.7 ± 6.1% to 4.8 ± 1.6% (p < 0.05, a relative decrease of 53 ± 26%), respectively. Although mean arterial pressure and stroke volume index tended to increase (41 ± 6 versus 45 ± 4 ml/min/m2, p = 0.14 and 41 ± 6 versus 45 ± 4 ml/min/m2, p = 0.05), and heart rate tended to decrease (73 ± 15 versus 68 ± 11 1/min, p = 0.05), no significant change was found. No significant change was found in respiratory parameter (tidal volume, respiratory rate or inspiratory pressure; p = 0.36, 0.34 and 0.17, respectively) or bladder pressure (6.0 ± 3.7 versus 5.6 ± 2.7 mmHg, p = 0.6) either.ConclusionsOpening of the abdomen decreases PPV and SVV. During goal directed therapy, current thresholds for fluid responsiveness should be changed accordingly.

Bringing back the old: time to reevaluate the high-frequency ventilation strategy

To examine the role of frequency in high-frequency ventilation (HFV) on carbon-dioxide (CO2) elimination and lung injury, independent of its effect on tidal volume. An anatomically representative lung model was attached to a mechanical ventilator capable of providing HFV with a constant volume. CO2 was infused directly into the lung, and a commercially available end-tidal CO2 detector was used to determine CO2 elimination. CO2 elimination and amplitude of pressure transmissions were evaluated using frequencies ranging from 5 to 15 Hz. The pressure-volume index (PVI) was described as the product of the volume and pressures delivered to the lung, a surrogate for lung injury. The use of increasing frequencies directly correlated with improved CO2 clearance when keeping the tidal volume fixed, expressed as percent CO2 remaining in the lung at 25 s (66.5 (±1.1)%, 50.5 (±0.1)% and 37.8 (±0.3)% at 5, 10 and 15 Hz, respectively, P<0.05). With a fixed tidal volume, there was a decrease in pressure amplitudes transmitted to the lung with a decline in the PVI (53.9 (±2.7) mmHg ml(-1), 41.1 (±0.9) mmHg ml(-1) and 23.4 (±3.6) mmHg ml(-1), at 5, 10 and 15 Hz, respectively, P<0.05). Frequency has a direct relationship with CO2 elimination when tidal volume is fixed. Using low delivered tidal volumes and high frequencies may allow for improved ventilation efficacy, while minimizing lung injury.

Hemodynamic Observations of Tumo Yoga Practitioners in a Himalayan Environment

Few attempts have been made to evaluate the physiology of traditional Eastern health practices. The goal of this study was to evaluate the hemodynamic effects of the mysterious Buddhist practice of tumo. Tumo is a meditative practice that produces inner heat through the alleged cultivation of body energy-channels. This study was performed by members of an international expedition to the Himalayan Mountains in the Republic of India. The study was performed in an unpopulated outdoor mountainous area at an altitude of 16,400 ft with ambient temperatures between -10 and -15(°)C. Two (2) cohorts of subjects were studied: healthy non-yogi volunteers and tumo practitioners. All of the subjects were stripped down to their underclothes and exposed to the subzero atmospheric temperatures for 5 minutes. The volunteers were then passively rewarmed while the tumo practitioners performed tumo for up to 10 minutes. Blood pressure, heart rate, and stroke volume index (SVI) and cardiac index were measured noninvasively using a NICOM™ hemodynamic monitor, while carotid blood flow and biventricular performance were determined echocardiographically at each stage of the experiment. The total peripheral resistance index (TPRI), left ventricular ejection fraction (LVEF), and tricuspid annular plane systolic excursion (TAPSE) were determined using standard formula. Fourteen (14) subjects (six volunteers and eight tumo practitioners) completed the study. There was one female subject in each group. With cold exposure, the SVI and carotid blood flow decreased while the TPRI increased significantly in both groups. In the volunteer group, these changes retuned to baseline with rewarming. Following tumo, the cardiac index (4.8±0.6 versus 4.0±0.5 l/m(2); p<0.01), carotid blood flow (445±127 versus 325±100 mL/min/m(2), p<0.01), LVEF (68±5 versus 64±7%; p<0.05) and TAPSE (2.9±0.4 versus 2.4±0.5 cm; p<0.01) were significantly higher when compared with baseline, while the TPRI was significantly lower (1786±189 versus 2173±281; p<0.01). Tumo was associated with a hyperdynamic vasodilated state with increased biventricular performance. We postulate that tumo results in a massive increase in sympathetic activity with activation of brown adipose tissue and marked heat production. The increased heat production may explain the paradoxical vasodilatation in tumo practitioners exposed to subzero temperatures.

Low molecular weight pentastarch is more effective than crystalloid solution in goal-directed fluid management in patients undergoing major gastrointestinal surgery

This prospective observational study compared the volume effect between hydroxyethyl starch (HES) and crystalloid solution and its context dependency in intraoperative goal-directed fluid management. With institutional review board (IRB) approval, 35 patients undergoing major gastrointestinal surgery were enrolled. Fluid challenge consisting of 250 ml of either bicarbonate Ringer solution (BRS) or low molecular weight pentastarch (HES 70/0.5) was given to maintain stroke volume index >35 ml/m2. The context of fluid challenge was classified as related to either epidural block (EB) or blood loss (BL) or as nonspecific. The primary end point was the interval between index fluid challenge and the next fluid challenge, and the secondary end point was the hemodynamic parameter at the end of fluid challenge. Differences in these parameters in each clinical context were compared between BRS and HES 70/0.5. A p value <0.05 was considered statistically significant. Eighty-eight, 77, and 127 fluid challenges were classified as related to EB and BL and as nonspecific, respectively. In the nonspecific condition, the median (range) interval after fluid challenge with HES 70/0.5 and BRS was 45 (11-162) min and 18 (8-44) min, respectively, and the difference was statistically significant. Also, mean arterial pressure and stroke volume index significantly increased, whereas stroke volume variation significantly decreased after fluid challenge with HES 70/0.5 compared with BRS. Such differences were not observed in the other situations. HES 70/0.5 exerted larger volume effects than did crystalloid under nonspecific conditions. However, similar volume effects were observed during volume loss and extensive sympathetic blockade.

Left atrial pressure as predictor for recurrence of atrial fibrillation after pulmonary vein isolation

Identification of reliable risk factors for recurrence of atrial fibrillation (AF) after pulmonary vein isolation (PVI) has important implications. Left atrial (LA) pressure is a largely observator-independent parameter that can easily be determined after transseptal puncture. The purpose of this study was to investigate the predictive value of LA pressure for AF recurrence after PVI. Two hundred five consecutive patients with paroxysmal or persistent AF scheduled for first PVI were included. Baseline clinical data were collected. During PVI, LA pressure was determined invasively after transseptal puncture. PVI was performed with radiofrequency or cryoenergy, and patients were followed for 25 ± 7months. One hundred five (51%) patients had AF recurrence. Patients with persistent AF prior to ablation had significantly more recurrences than patients with paroxysmal AF (70.1 vs. 42.0%, p < 0.001). Mean LA pressure was significantly higher in patients with recurrence of AF (13.4 ± 7.1 vs. 11.0 ± 5.2mmHg, p = 0.007), as was mean LA volume index (40.1 ± 18.5 vs. 33.0 ± 11.2mL/m(2), p < 0.001). In the multivariate analysis, mean LA pressure was predictive in patients with normal or mildly enlarged LA, while AF type was not predictive. For each 1-mmHg increase in LA pressure, the risk of AF recurrence increased by 11% in this subgroup. In patients with moderately or severely enlarged LA, AF type was predictive whereas LA pressure was not. LA pressure, AF type, and LA volume index are independent predictors for recurrence of AF after PVI. LA pressure may be helpful especially in patients with small atria, where AF type is not predictive.

Assessment effect of central venous pressure in fluid resuscitation in the patients with shock: a multi-center retrospective research

Background Central venous pressure (CVP) and intrathoracic blood volume index (ITBVI) were used to assess the fluid status. It has previously been shown that CVP is not as accurate as ITBVI for all the shock patients. We therefore hypothesized that the change of CVP has the ability to predict fluid responsiveness in some clinical cases of shock. Methods From September 1st 2009 to September 1st 2011, sixty-three patients with shock from different Intensive Care Unit (ICU) were collected into this retrospective study. All the patients received fluid challenge strategy (infusing 300 ml hydroxyethyl starch in 20 minutes), were monitored with CVP and pulse-indicated continuous cardiac output (PICCO). The correlation between changes in cardiac index (ΔCI), CVP (ΔCVP) and ITBVI (ΔITBVI) were analyzed. Fluid responsiveness was defined as an increase in CI ≥10%. Receiver operating characteristic (ROC) curves were generated for ΔCVP and ΔITBVI. Results For all the patients, there was no correlation between ΔCI and ΔCVP (P=0.073), but in the subgroup analysis, the correlation between ΔCI and ΔCVP was significant in those younger than 60 years old (P=0.018) and those with hypovolemic shock (P=0.001). The difference of areas under the ROC curves of ΔCVP and ΔITBVI were not statistically significant in the group younger than 60 years old or hypovolemic shock group (P &gt;0.05, respectively). However, no similar results can be found in the group older than 60 years old and the other two shock type groups from ROC curves of ΔCVP and ΔITBVI. Conclusions ΔCVP is not suitable for evaluating the volume status of the shock patients with fluid resuscitation regardless of their condition. However, in some ways, ΔCVP have the ability to predict fluid responsiveness in the younger shock patients or in the hypovolemic shock patients.

Impact of Epoetin Alfa on Left Ventricular Structure, Function, and Pressure Volume Relations as Assessed by Cardiac Magnetic Resonance: The Heart Failure Preserved Ejection Fraction (HFPEF) Anemia Trial

Anemia, a common comorbidity in older adults with heart failure and a preserved ejection fraction (HFPEF), is associated with worse outcomes. The authors quantified the effect of anemia treatment on left ventricular (LV) structure and function as measured by cardiac magnetic resonance (CMR) imaging. A prospective, randomized single-blind clinical trial (NCT NCT00286182) comparing the safety and efficacy of epoetin alfa vs placebo for 24 weeks in which a subgroup (n=22) had cardiac magnetic resonance imaging (MRI) at baseline and after 3 and 6 months to evaluate changes in cardiac structure and function. Pressure volume (PV) indices were derived from MRI measures of ventricular volume coupled with sphygmomanometer-measured pressure and Doppler estimates of filling pressure. The end-systolic and end-diastolic PV relations and the area between them as a function of end-diastolic pressure, the isovolumic PV area (PVAiso), were calculated. Patients (75±10 years, 64% women) with HFPEF (EF=63%±15%) with an average hemoglobin of 10.3±1.1 gm/dL were treated with epoetin alfa using a dose-adjusted algorithm that increased hemoglobin compared with placebo (P<.0001). As compared with baseline, there were no significant changes in end-diastolic (-7±8 mL vs -3±8 mL, P=.81) or end-systolic (-0.4±2 mL vs -0.7±5 mL, P=.96) volumes at 6-month follow-up between epoetin alfa compared with placebo. LV function as measured based on EF (-1.5%±1.6% vs -2.6%±3.3%, P=.91) and pressure volume indices (PVAiso-EDP at 30 mm Hg, -5071±4308 vs -1662±4140, P=.58) did not differ between epoetin alfa and placebo. Administration of epoetin alfa to older adult patients with HFPEF resulted in a significant increase in hemoglobin, without evident change in LV structure, function, or pressure volume relationships as measured quantitatively using CMR imaging.

Measurement of CSF dynamics with oscillating pressure infusion

Infusion tests are used to diagnose and select patients with idiopathic normal pressure hydrocephalus (INPH) for shunt surgery. The test characterizes cerebrospinal fluid dynamics and estimates parameters of the cerebrospinal fluid system, the pressure-volume index (PVI) and the outflow conductance (Cout). The Oscillating Pressure Infusion (OPI) method was developed to improve the test and reduce the investigation time. The aim of this study was to evaluate the new OPI method by comparing it with an established reference method. Forty-seven patients (age 71.2 ± 8.9 years) with communicating hydrocephalus underwent a preoperative lumbar infusion investigation with two consecutive infusion protocols, reference (42 min) and new (20 min), that is, 94 infusion tests in total. The OPI method estimated Cout and PVI simultaneously. A real-time analysis of reliability was applied to investigate the possibility of infusion time reduction. The difference in Cout between the methods was 1.2 ± 1.8 μl/s/kPa (ΔRout = -0.8 ± 3.5 mmHg/ml/min), P < 0.05, n = 47. With the reliability analysis, the preset 20 min of active infusion could have been even further reduced for 19 patients to between 10 and 19 min. PVI was estimated to 16.1 ± 6.9 ml, n = 47. The novel Oscillating Pressure Infusion method produced real-time estimates of Cout including estimates of reliability that was in good agreement with the reference method and allows for a reduced and individualized investigation time.

The Impact of Portopulmonary Hypertension on Intraoperative Right Ventricular Function of Living Donor Liver Transplant Recipients

Portopulmonary hypertension (PPH) burdens a right ventricle (RV) already exposed to physiologic stress during liver transplantation. The magnitude of the impact of PPH on RV function, especially early reperfusion, has not been evaluated adequately by prospective controlled trials. In this study, we prospectively quantified the impact of PPH on the RV function in living donor liver transplant recipients. Twenty patients undergoing living donor liver transplant were stratified based on mean pulmonary artery pressure (mPAP) into a control group (mPAP <25 mm Hg) and a PPH group (mPAP ≥25 mm Hg). Standard anesthetic technique and monitoring were used. Fiberoptic pulmonary artery catheters enabled to measure RV ejection fraction (RVEF) were used. Hemodynamics were recorded after induction of anesthesia, the end of hepatectomy, before portal unclamping, 5 and 30 minutes after reperfusion, and at skin closure. The PPH group had significantly lower RVEF, stroke volume, and higher central venous pressure and RV end-diastolic volume index after portal unclamping versus the controls. Pulmonary vascular resistance index and mPAP were significantly higher throughout the operation in the PPH group, but RV stroke work index did not differ significantly between groups. RVEF was significantly reduced in the PPH group after reperfusion compared with baseline, but the control group did not experience such a reduction. Mild to moderate PPH was associated with reduced RVEF during liver transplantation, especially after reperfusion, likely because of a reduced RV contractile reserve in PPH patients. This reduction in RVEF was clinically well tolerated by patients with mild to moderate PPH.

Electrophysiological and Hemodynamic Characteristics Associated With Obesity in Patients With Atrial Fibrillation

The authors sought to characterize the left atrial (LA) and pulmonary vein (PV) electrophysiological and hemodynamic features in obese patients with atrial fibrillation (AF). Obesity is associated with increased risk for AF. A total of 63 consecutive patients with AF who had normal left ventricular (LV) ejection fraction and who underwent catheter ablation were studied. Atrial and PV electrophysiological studies were performed at the time of ablation with hemodynamic assessment by cardiac catheterization, and LA/LV structure and function by echocardiography. Patients were compared on the basis of body mass index (BMI): <25 kg/m(2) (n = 19) and BMI ≥30 kg/m(2) (n = 44). At a 600-ms pacing cycle length, obese patients had shorter effective refractory period (ERP) in the left atrium (251 ± 25 ms vs. 233 ± 32 ms, p = 0.04), and in the proximal (207 ± 33 ms vs. 248 ± 34 ms, p < 0.001) and distal (193 ± 33 ms vs. 248 ± 44 ms, p < 0.001) PV than normal BMI patients. Obese patients had higher mean LA pressure (15 ± 5 mm Hg vs. 10 ± 5 mm Hg, p < 0.001) and LA volume index (28 ± 12 ml/m(2) vs. 21 ± 14 ml/m(2), p = 0.006), and lower LA strain (5.5 ± 3.1% vs. 8.8 ± 2.8%; p < 0.001) than normal BMI patients. Increased LA pressure and volume, and shortened ERP in the left atrium and PV are potential factors facilitating and perpetuating AF in obese patients with AF.

PRESSURE–VOLUME INDEX‐BASED VOLUME CALCULATION OF CONTRAST MEDIUM FOR ATLANTO‐OCCIPITAL MYELOGRAPHY IN DOGS

Subarachnoid pressure recordings were made during atlanto-occipital myelography in 45 dogs with clinical signs of spinal disease. Iohexol was injected at a dosage of 0.3 ml/kg body weight and simultaneous pressure values were recorded in the cerebellomedullary cistern. The mean subarachnoid pressure was 9 ± 3 mmHg before and 70 ± 32 mmHg at the end of administration. From the pressure change induced by the volume load, the pressure-volume index (PVI) of the subarachnoid space was calculated and found to be in close correlation with body weight and the crown-rump length (r = 0.94 and 0.87). Using the estimated PVI values, the appropriate volume of contrast medium can be calculated for an animal according to body weight. Dogs of a large body size require relatively less contrast medium than small-sized dogs (range 0.17-0.35 ml/kg). This calculated volume is unlikely to increase the subarachnoid pressure above 40 mmHg as a specific pressure limit. Using these data, simplified recommendations for the choice of contrast medium volumes have been generated.

Chapter 10. Cerebrospinal fluid drainage

Chapter 10. Cerebrospinal fluid drainage

Chapter 4. Threshold for treatment of intracranial hypertension

Chapter 4. Threshold for treatment of intracranial hypertension

Non-invasive assessment of arterial stiffness using oscillometric blood pressure measurement

BackgroundArterial stiffness is a major contributor to cardiovascular diseases. Because current methods of measuring arterial stiffness are technically demanding, the purpose of this study was to develop a simple method of evaluating arterial stiffness using oscillometric blood pressure measurement.MethodsBlood pressure was conventionally measured in the left upper arm of 173 individuals using an inflatable cuff. Using the time series of occlusive cuff pressure and the amplitudes of pulse oscillations, we calculated local slopes of the curve between the decreasing cuff pressure and corresponding arterial volume. Whole pressure-volume curve was derived from numerical integration of the local slopes. The curve was fitted using an equation and we identified a numerical coefficient of the equation as an index of arterial stiffness (Arterial Pressure-volume Index, API). We also measured brachial-ankle (baPWV) PWV and carotid-femoral (cfPWV) PWV using a vascular testing device and compared the values with API. Furthermore, we assessed carotid arterial compliance using ultrasound images to compare with API.ResultsThe slope of the calculated pressure-volume curve was steeper for compliant (low baPWV or cfPWV) than stiff (high baPWV or cfPWV) arteries. API was related to baPWV (r = -0.53, P < 0.05), cfPWV (r = -0.49, P < 0.05), and carotid arterial compliance (r = 0.32, P < 0.05). A stepwise multiple regression analysis demonstrated that baPWV and carotid arterial compliance were the independent determinants of API, and that API was the independent determinant of baPWV and carotid arterial compliance.ConclusionsThese results suggest that our method can simply and simultaneously evaluate arterial stiffness and blood pressure based on oscillometric measurements of blood pressure.

Determination of cranio‐spinal canal compliance distribution by MRI: Methodology and early application in idiopathic intracranial hypertension

To develop a method for derivation of the cranial-spinal compliance distribution, assess its reliability, and apply to obese female patients with a diagnosis of idiopathic intracranial hypertension (IIH). Phase contrast-based measurements of blood and cerebrospinal fluid (CSF) flows to, from, and between the cranial and spinal canal compartments were used with lumped-parameter modeling to estimate systolic volume and pressure changes from which cranial and spinal compliance indices are obtained. The proposed MRI indices are analogous to pressure volume indices (PVI) currently being measured invasively with infusion-based techniques. The consistency of the proposed method was assessed using MRI data from seven aged healthy subjects. Measurement reproducibility was assessed using five repeated MR scans from one subject. The method was then applied to compare spinal canal compliance contribution in seven IIH patients and six matched healthy controls. In the healthy subjects, as expected, spinal canal contribution was consistently larger than the cranial contribution (average value of 69%). Measurement variability was 8%. In IIH, the spinal canal contribution is significantly smaller than normal controls (60 versus 78%, P < 0.03). An MRI-based method for derivation of compliance indices analogous to PVI has been implemented and applied to healthy subjects. The application of the method to obese IIH patients suggests a spinal canal involvement in the pathophysiology of IIH.

Elevated vascular resistance and afterload reduce the cardiac output response to dobutamine in early growth-restricted rats in adulthood

Epidemiological studies have linked intra-uterine growth restriction (IUGR) with an increased risk of CVD later in life. The aim of the present study was to examine the effect of maternal protein restriction on cardiac function in adulthood during dobutamine (DOB) stimulation. IUGR was induced in Wistar Kyoto dams through administration of a low-protein diet (LPD; 8.7 % casein) during pregnancy and lactation; the control group received a normal-protein diet (NPD; 20 % casein). At 14 weeks of age, cardiac function was assessed in male and female NPD (eight females and eight males) and LPD offspring (ten females and ten males) by pressure volumetry using an anaesthetised closed-chest approach. We determined mean arterial pressure (MAP), heart rate and left ventricular pressure-volume indices under baseline conditions and DOB stimulation (2 and 4 μg/kg per min). During β-adrenergic activation in LPD offspring, increases in cardiac output (CO, P < 0.018) and stroke volume (SV, P < 0.005) were attenuated in comparison with NPD offspring, while increases in ejection fraction and the maximal rate of ventricular pressure development were not affected. LPD females maintained a smaller end-diastolic volume (P < 0.017). MAP did not differ between the groups and did not change significantly during DOB infusion. Arterial elastance and total peripheral resistance decreased in all rats but remained significantly elevated in LPD offspring (P < 0.015 and < 0.01). Early growth restriction did not affect ventricular contractility but led to an increased afterload and impaired the ability to increase SV and CO during β-adrenergic stimulation.

A Haemodynamic Study during OPCAB Surgery Using a New Multi-Suction Cardiac Positioner

Displacement of the heart is necessary to expose the target vessel for distal anastomosis to achieve successful multivessel off-pump coronary artery bypass (OPCAB) grafting. In addition to complete revascularisation of the heart, a main challenge during the operation is to maintain haemodynamic stability during this procedure. A new heart positioner (Tentacles) was tested. In a prospective clinical study we used the Tentacles device in 50 patients scheduled for multivessel OPCAB procedures and investigated the haemodynamic effects during displacement of the heart and while performing the anastomoses to the anterior, lateral and posterior wall. The following haemodynamic parameters were investigated: mean arterial blood pressure (MAP), cardiac index (CI) and stroke volume index (SVI). The incidence of myocardial ischaemia was monitored by transoesophageal echocardiography (TEE) and by ST-segment analysis in the electrocardiogram (ECG). The Tentacles device permitted rapid, secure and excellent exposure of the lateral and posterior wall of the heart. During exposure of the anterior wall there was a small decrease in MAP (77 ± 10 vs.71 ± 9 mmHg, P = 0.02) in combination with an increase in the CI (3.0 ± 0.7 l vs. 3.1 ± 0.8 l/min/m2, P = 0.03). When the lateral and posterior walls of the heart were exposed, the SVI decreased significantly (36 ± 11 and 38 ± 8 mL/m2, P < 0.01 and P = 0.04, respectively) compared to baseline (44 ± 11 mL/m2) while CI and MAP remained stable. The amount of norepinephrine administered during displacement of the heart was significantly higher in all three positions (0.05 ± 0.05, 0.06 ± 0.05 and 0.04 ± 0.03 µg/kg/min, P < 0.01) compared to the physiological position (0.02 ± 0.02 µg/kg/min). Sinus rhythm was maintained throughout the operation. Neither significant changes of the ST-segment in the ECG nor incidences of wall motion abnormality in TEE were observed. Six hours postoperatively the troponin I concentration was 11.7 ± 4.3 ng/mL. The Tentacles device provided excellent access in multivessel OPCAB surgery. Haemodynamic stability was maintained in all patients; however additional catecholamine support was used when the heart was displaced. This was the case when carrying out an anastomosis on the anterior, lateral, or posterior wall.