Noninvasive Hemodynamic Measurements Research Articles

Chapter I: Definitions, Epidemiology, Clinical Presentation and Prognosis

The concept of chronic critical limb ischaemia (CLI) emerged late in the history of peripheral arterial occlusive disease (PAOD). The historical background and changing definitions of CLI over the last decades are important to know in order to understand why epidemiologic data are so difficult to compare between articles and over time. The prevalence of CLI is probably very high and largely underestimated, and significant differences exist between population studies and clinical series. The extremely high costs associated with management of these patients make CLI a real public health issue for the future. In the era of emerging vascular surgery in the 1950s, the initial classification of PAOD by Fontaine, with stages III and IV corresponding to CLI, was based only on clinical symptoms. Later, with increasing access to non-invasive haemodynamic measurements (ankle pressure, toe pressure), the need to prove a causal relationship between PAOD and clinical findings suggestive of CLI became a real concern, and the Rutherford classification published in 1986 included objective haemodynamic criteria. The first consensus document on CLI was published in 1991 and included clinical criteria associated with ankle and toe pressure and transcutaneous oxygen pressure (TcPO 2) cut-off levels <50 mmHg, <30 mmHg and <10 mmHg respectively). This rigorous definition reflects an arterial insufficiency that is so severe as to cause microcirculatory changes and compromise tissue integrity, with a high rate of major amputation and mortality. The TASC I consensus document published in 2000 used less severe pressure cut-offs (≤50–70 mmHg, ≤30–50 mmHg and ≤30–50 mmHg respectively). The thresholds for toe pressure and especially TcPO 2 (which will be also included in TASC II consensus document) are however just below the lower limit of normality. It is therefore easy to infer that patients qualifying as CLI based on TASC criteria can suffer from far less severe disease than those qualifying as CLI in the initial 1991 consensus document. Furthermore, inclusion criteria of many recent interventional studies have even shifted further from the efforts of definition standardisation with objective criteria, by including patients as CLI based merely on Fontaine classification (stage III and IV) without haemodynamic criteria. The differences in the natural history of patients with CLI, including prognosis of the limb and the patient, are thus difficult to compare between studies in this context. Overall, CLI as defined by clinical and haemodynamic criteria remains a severe condition with poor prognosis, high medical costs and a major impact in terms of public health and patients' loss of functional capacity. The major progresses in best medical therapy of arterial disease and revascularisation procedures will certainly improve the outcome of CLI patients. In the future, an effort to apply a standardised definition with clinical and objective haemodynamic criteria will be needed to better demonstrate and compare the advances in management of these patients.

Reproducibility of cardiac power output and other cardiopulmonary exercise indices in patients with chronic heart failure

Cardiac power output is a direct measure of overall cardiac function that integrates both flow- and pressure-generating capacities of the heart. The present study assessed the reproducibility of cardiac power output and other more commonly reported cardiopulmonary exercise variables in patients with chronic heart failure. Metabolic, ventilatory and non-invasive (inert gas re-breathing) central haemodynamic measurements were undertaken at rest and near-maximal exercise of the modified Bruce protocol in 19 patients with stable chronic heart failure. The same procedure was repeated 7days later to assess reproducibility. Cardiac power output was calculated as the product of cardiac output and mean arterial pressure. Resting central haemodynamic variables demonstrate low CV (coefficient of variation) (ranging from 3.4% for cardiac output and 5.6% for heart rate). The CV for resting metabolic and ventilatory measurements ranged from 8.2% for respiratory exchange ratio and 14.2% for absolute values of oxygen consumption. The CV of anaerobic threshold, peak oxygen consumption, carbon dioxide production and respiratory exchange ratio ranged from 3.8% (for anaerobic threshold) to 6.4% (for relative peak oxygen consumption), with minute ventilation having a CV of 11.1%. Near-maximal exercise cardiac power output and cardiac output had CVs of 4.1 and 2.2%, respectively. Cardiac power output demonstrates good reproducibility suggesting that there is no need for performing more than one cardiopulmonary exercise test. As a direct measure of cardiac function (dysfunction) and an excellent prognostic marker, it is strongly advised in the assessment of patients with chronic heart failure undergoing cardiopulmonary exercise testing.

Use of non-invasive haemodynamic measurements to detect treatment response in precapillary pulmonary hypertension

BackgroundHaemodynamic measurements may be superior to the 6-min walk distance (6MWD) as outcome measures in pulmonary hypertension (PH) as they are directly linked to the mechanisms of disease and are...

The impact of acute reduction of continuous-flow left ventricular assist device support on cardiac and exercise performance

BackgroundThe use of the HeartMate II continuous-flow left ventricular assist device (LVAD) improves survival, quality of life and functional capacity of patients with advanced heart failure. However, no study so...

002 Can non-pulsatile continuous-flow left ventricular assist devices confer physiologically desirable cardiac and physical functional benefits during peak exercise?

<h3>Introduction</h3> Left ventricular assist devices (LVADs) have been used as an effective therapeutic option in patients with advanced heart failure either as a bridge to transplantation, as destination therapy or as a bridge to recovery. Most recently it has been shown that the use of continuous-flow LVAD (HeartMate II) improves the rate of survival, quality of life, and functional capacity of patients as compared with the pulsatile-flow LVAD. To date, no study has reported how well HeartMate II can improve organ function and patients9 exercise ability. The present project aimed to assess cardiac and exercise performance of patients implanted with continuous-flow LVADs under two conditions: (i) optimal device support, and (ii) reduced device support. These results were compared with those of LVAD explanted (recovered) patients, heart transplant candidates and healthy controls. <h3>Methods</h3> Fifty-eight male patients, 18 implanted with a HeartMate II LVAD, 16 LVAD explanted patients and 24 heart transplant candidates (HTx) and 101 healthy controls performed graded cardiopulmonary exercise test with respiratory gas exchange and noninvasive (rebreathing) haemodynamic measurements. Twelve of the 18 LVAD implanted patients performed an additional cardiopulmonary exercise test with reduced LVAD support (pump speed reduced from optimal 9000–9600 revs/min to 6000 revs/min). <h3>Results</h3> At lower HeartMate II support, peak exercise cardiac power output was 39% lower (1.42±0.41 vs 2.31±0.50 W; p&lt;0.05), peak cardiac output 30% lower (8.6±2.31 vs 12.2±1.55 l/min; p&lt;0.05), and mean blood pressure 13% lower (74±7 vs 85±12 vs mmHg; p&lt;0.05). Exercise capacity was also diminished with 23% lower peak oxygen consumption (14.1±5.3 vs 18.2±4.5 ml/kg/min; p&lt;0.05) and 18% shorter exercise duration (516±179 vs 628±142 s; p&lt;0.05). Peak cardiac power output was significantly higher in the LVAD explanted than in the HTx and the LVAD implanted patients (HTx: 1.31±0.31 W; implanted: 2.31±0.50 W; explanted: 3.39±0.61 W; p&lt;0.01) as was peak cardiac output (HTx: 8.0±1.5; implanted: 12.2±1.55 explanted, 14.6±2.9 l/min; p&lt;0.01). Peak oxygen consumption was higher in the LVAD explanted than the HTx and the implanted patients (HTx, 12.5±2.5; implanted, 18.2±4.5; explanted, 28.2±5.0 ml/kg/min; p&lt;0.05) as was oxygen consumption at anaerobic threshold (p&lt;0.05). In the explanted cohort, 38% achieved peak cardiac power output and 69% peak oxygen consumption within the ranges of healthy controls. <h3>Conclusion</h3> We have shown for the first time that complementary to reported prognostic benefits, non-pulsatile continuous-flow LVAD pumps can confer cardiac functional benefits to patients with end-stage heart failure to derive improved exercise capacity, while those who recovered sufficiently to allow explantation of LVADs can even achieve cardiac and physical functional capacities nearly equivalent to those of healthy controls.

066 Vasodilatory capacity at peak exercise in treated heart failure patients are not diminished

Background Previous received dogma has propagated the concept that heart failure (HF) patients have compromised vasodilatory capacity during exercise through various vascular mechanisms, thereby reducing their exercise capacity through peripheral (vascular) factors rather than central (cardiac) factors. We tested whether such a concept is still valid in modern HF patients receiving current standard HF therapies. Methods and Results We recruited 150 female participants (133 normal healthy controls, age 48.5±13.1 (SD) years; 17 DCM patients, age 41.5±14.2 years) with no known coronary or other vascular diseases, and compared their central haemodynamic responses during volitional maximal exercise. The exercise capacity of controls spanned the same ranges as those of the HF patients. All patients performed symptom-limited cardiopulmonary exercise testing (CPX) with breath-by-breath analyses of respiratory gases and non-invasive haemodynamic measurements employing standard auscultatory sphygmomanometric and rebreathing methods. The patients performed a total of 30 CPX9s. The peak O2 consumption spanned from 1.20 to 2.45 L/min in DCM patients and from 1.15 to 2.44 L/min in controls. As shown in the figure, at peak exercise the systemic vascular resistances (SVR) of DCM patients were lower (532±154 dyn.s.cm-5) than those of controls (654±118 dyn.s.cm-5). Conclusion With modern HF therapy, the lower peak exercise SVR in HF patients compared to normal healthy controls demonstrates that there is no evidence of compromised systemic vasodilatory capacities in HF patients. The long-held dogma of vasodilatory incapacity in HF propagated >3 decades ago is no longer valid nowadays.

A Comprehensive Noninvasive Hemodynamic Assessment of Systolic Heart Failure

Article see p 387 The prevalence of systolic and diastolic heart failure increases with advancing age between 5% and 10% of all subjects beyond the age of 60 years. The cause of heart failure in the majority of patients is occlusive coronary artery disease, hypertension, and idiopathic dilated cardiomyopathy. The current estimated costs for the treatment of heart failure in the United States alone are approaching $40 billion per year, and for this reason, heart failure has been identified as a major health care initiative. Some of these costs could be defrayed if recurrent hospital admissions for serial hemodynamic assessments could be replaced by noninvasive hemodynamic measurements with the use of Doppler echocardiography in a more cost-effective outpatient setting. Although right heart catheterization remains the gold standard for measurement of intracardiac pressures,1,2 enthusiasm for placement of Swan–Ganz catheters has dwindled over the past decade on account of complications that include infection, cardiac perforation, and tamponade. Doppler echocardiography is generally acknowledged to be a noninvasive alternative to Swan–Ganz catheterization for hemodynamic assessment at the bedside.3–8 Hitherto, a number of isolated noninvasive Doppler echo measurements of left ventricular (LV) filling pressure, right atrial pressure, and cardiac output and the changes following load interventions have correlated closely with measurements made by Swan–Ganz catheterization.3,8,9 What has been notable by its absence is a consensus regarding a portfolio of measurements that can be used in all patients with heart failure to provide a comprehensive hemodynamic assessment at the bedside that will determine the subsequent treatment strategy. An important prerequisite of such a panel of hemodynamic tests is that they are quick to perform, easy to interpret, previously validated, and reproducible. Doppler echocardiography in addition to enabling numerous hemodynamic measurements to be made also provides …

Reduced cardiac functional reserve and quality of life in adults with GH deficiency

Patients with severe GH deficiency (GHD) suffer with a reduced quality of life in addition to diverse changes in cardiac size and performance. So far, the cardiac reserve ability to maintain the circulation during peak exercise has not been measured. We tested the hypothesis that patients with severe GHD have reduced cardiac reserve function compared with healthy controls and that this could explain, in part, their reduced quality of life. Eighteen patients with severe GHD and an assessment of GHD in adults (AGHDA) score > or =11 (mean 20.0, range 12-25) were studied and compared with 18 age-, sex- and body mass index-matched healthy controls. Peak cardiac power and cardiorespiratory fitness were investigated using noninvasive haemodynamic measurements during maximal cardiopulmonary exercise testing. Compared with matched controls, the cardiac power of GHD patients during exercise to volitional exhaustion was significantly reduced by 15% (mean +/- SD 4.4 +/- 1.0 W vs. 5.2 +/- 1.0 W, P = 0.02). Patients with GHD also had lower cardiac chronotropic reserve (peak heart rate 154 +/- 21/min vs. 174 +/- 11/min, P = 0.001) and a lower cardiac pressure-generating capacity (systolic blood pressure 160 +/- 25 mmHg vs. 200 +/- 15 mmHg, P < 0.0001). We found no correlation between any measure of peak cardiac power or function and the AGHDA score. Using this robust noninvasive method of assessing functional cardiac pumping capacity, we have for the first time shown that, while patients with severe GHD have a significantly impaired cardiac functional reserve associated with chronotropic incompetence and impaired pressure-generating capacity, this does not correlate with their reduced quality of life assessed using the current standard AGHDA score.

Cardiac Functional Reserve is Diminished in Growth Hormone‐Deficient Adults

Various studies have shown that patients with severe growth hormone deficiency (GHD) have diverse changes in left ventricular (LV) size or performance but so far there is no direct indication of cardiac reserve ability to maintain the circulation during peak exercise. We tested the hypothesis that patients with severe GHD have reduced cardiac reserve function compared with healthy controls. Eighteen patients with severe GHD were studied and compared with 18 age-, sex-, and body mass index (BMI)-matched healthy controls. Peak cardiac power and cardiorespiratory fitness were investigated using noninvasive hemodynamic measurements during maximal cardiopulmonary exercise testing. Compared with matched controls, the cardiac power of GHD patients during exercise to volitional exhaustion was significantly reduced by 15% (mean +/- SD: 4.4 +/- 1.0 watts (W) vs. 5.2 +/- 1.0 W, P= 0.02), despite attaining similar aerobic exercise peaks (VO(2max), GHD: 2390 +/- 822 mL/min vs. controls: 2461 +/- 872 mL/min, P= 0.80) and similar peak respiratory exchange ratios. The lower peak cardiac power could not be accounted for by peripheral alterations because both groups reached similar peak exercise systemic vascular resistances. Patients with GHD also had lower cardiac chronotropic reserve (peak heart rate: 154 +/- 21 bpm vs. 174 +/- 11 bpm, P= 0.001) and a lower cardiac pressure-generating capacity (systolic blood pressure [SBP] 160 +/- 25 mmHg vs. 200 +/- 15 mmHg, P < 0.0001). Using this robust noninvasive method of assessing functional cardiac pumping capacity we have for the first time shown that patients with severe GHD have a significantly impaired cardiac functional reserve associated with chronotropic incompetence and impaired pressure-generating capacity.

Impedance cardiography versus invasive measurements of stroke volume index in patients with chronic heart failure

We assessed the hypothesis that non-invasive measurement of stroke volume index can replace invasive measurements in patients with chronic heart failure. Non-invasive impedance cardiography (ICG) measurements together with invasive hemodynamic thermodilution (TD) measurements were performed in 13 patients with severe chronic heart failure (NYHA III–IV). Agreement between ICG and TD regarding stroke volume index was poor. Correlation between non-invasive and invasive hemodynamic measurements was low ( r = 0.29). In conclusion, non-invasive measurements of stroke volume index using impedance cardiography did not result in sufficient agreement with invasive thermodilution measurements in this study with patients suffering from severe chronic heart failure.

NeuroMath: Advanced Methods for the Estimation of Human Brain Activity and Connectivity

NeuroMath: Advanced Methods for the Estimation of Human Brain Activity and Connectivity

Cardiac magnetic resonance stress testing: Results and prognosis

Cardiac stress magnetic resonance (MR) testing has been developed and optimized in the past decade, reaching a high diagnostic performance. Its efficacy, together with its excellent safety profile and increasing availability, make cardiac stress MR testing one of the diagnostic modalities of choice for detecting ischemia. A noticeable series of studies validated the diagnosis of ischemia with MR compared with coronary angiography and other noninvasive diagnostic techniques and invasive hemodynamic measurements. In addition, first data on the usefulness of cardiac stress MR testing in assessing prognosis has become available. This article reviews the available literature about diagnostic performance of cardiac stress MR testing and its results in the prognostication of cardiac patients.

A novel non invasive measurement of hemodynamic parameters: Comparison of single-chamber ventricular and dual-chamber pacemaker

We carried out a cross sectional study to analyze hemodynamic parameters of single-chamber ventricular pacemaker compared with dual-chamber pacemaker by using thoracic electrical bioimpedance monitoring method (Physio Flow™) - a novel simple non-invasive measurement. A total of 48 consecutive outpatients comprised of 27 single chamber pacemaker and 21 dual chamber were analyzed. We measured cardiac parameters: heart rate, stroke volume index, cardiac output index, estimated ejection fraction, end diastolic volume, early diastolic function ratio, thoracic fluid index, and systemic parameters: left cardiac work index and systemic vascular resistance index. Baseline characteristic and pacemaker indication were similar in both groups. Cardiac parameters assessment revealed no significant difference between single-chamber pacemaker and dual-chamber pacemaker in heart rate, stroke volume index, cardiac index, estimated ejection fraction, end-diastolic volume, thoracic fluid index. There was significantly higher early diastolic function ratio in single-chamber pacemaker compared to dual-chamber pacemaker: 92% (10.2-187.7%) vs. 100.6% (48.7-403.2%); p=0.006. Systemic parameters assessment revealed significantly higher left cardiac work index in single-chamber group than dual-chamber group 4.9 kg.m/m² (2.8-7.6 kg.m/m²) vs. 4.3 kg.m/m² (2.9-7.2 kg.m/m²); p=0.004. There was no significant difference on systemic vascular resistance in single-chamber compared to dual-chamber pacemaker. Single-chamber ventricular pacemaker provides similar stroke volume, cardiac output and left cardiac work, compared to dual-chamber pacemaker. A non-invasive hemodynamic measurement using thoracic electrical bioimpedance is feasible for permanent pacemaker outpatients. (Med J Indones 2008; 17: 25-32)

Utility of impedance cardiography for dyspneic patients in the ED

Background Dyspnea is one of the most common emergency department (ED) symptoms, but early diagnosis and treatment are challenging because of multiple potential causes. Hemodynamic parameters may aid in the evaluation of dyspnea, but are difficult to assess. Impedance cardiography is a noninvasive hemodynamic measurement method that may assist in early ED decision making. Methods This study is intended to determine the accuracy in differentiating cardiac from noncardiac causes of dyspnea using impedance cardiography–derived hemodynamic parameters compared to ED physician opinion in light of initial history, and physical and laboratory tests. The final diagnosis, made after patient hospital record review, was compared with ED physician and impedance cardiography diagnoses. Results A total of 52 patients were included: 14 women and 38 men, aged 68.5 ± 14.2 years. There were significant differences in values of stroke index (25.7 vs 32.9, P < .05), cardiac index (2.3 vs 3.1, P < .0001), velocity index (35.1 vs 53.2, P < .01), and systolic time ratio (0.55 vs 0.44, P < .05) between the cardiac and noncardiac groups, respectively. Impedance cardiography measurements demonstrated better sensitivity (75% vs 60%), specificity (88% vs 66%), and positive and negative predictive values (79% vs 52% and 85% vs 72%, respectively) compared with those of the ED physician in distinguishing cardiac from noncardiac causes of dyspnea. Conclusion Impedance cardiography data result in improvement in ED physician differentiation of cardiac from noncardiac causes of dyspnea.

Biventricular Pacing Using Dual‐Site Right Ventricular Stimulation: Is It Placebo Effect?

Alternate site lead placement in cardiac resynchronization therapy has been used successfully but remains to be validated. A 62-year-old heart failure patient in whom coronary sinus lead placement was not possible underwent implantation of the lead in the right ventricular outflow tract (RVOT) and demonstrated clinical improvement as measured by New York Heart Association class and noninvasive parameters. When heart failure recurred, it was determined that his RVOT electrode had been pulled back (Twiddler's syndrome). Repositioning again improved his clinical status and noninvasive hemodynamic measurements. With dual-site right ventricular (RV) pacing there was no echocardiographic measurable intraventricular dyssynchrony. Tissue Doppler imaging correlated with clinical improvement using dual-site RV pacing, providing evidence that this technique may represent a viable alternative in cardiac resynchronization therapy.

Morbidly Obese Patients are Hemodynamically Stable During Laparoscopic Surgery: A Thoracic Bioimpedance Study

Morbid obesity caries an increased risk of cardiovascular morbidity and might be associated with intraoperative hemodynamic instability. Based on clinical observation, we hypothesized that during laparoscopic surgery, morbidly obese patients behave hemodynamically similar to the nonobese patients and remain hemodynamically stable. In a prospective trial, thirty nonobese and tthirty morbidly obese (BMI > or = 35 kg/m(2)) patients scheduled for elective laparoscopic surgery were assigned to receive standard balanced anesthesia. We aimed at equianesthetic levels by keeping the BIS (bispectral index) value between 40-50 throughout surgery. End-tidal isoflurane was measured every 5 min. Noninvasive hemodynamic measurements included cardiac index (CI), mean arterial pressure (MAP) and heart rate (HR), recorded every 5 min and at specific predetermined times. Systemic vascular resistance (SVR) was calculated. Episodes of MAP < or = 60 and MAP > or = 130 mmHg or HR < or = 50 and HR > or = 110 bpm occurring throughout surgery and requiring pharmacological intervention were considered main end-points. Additionally, hemodynamic variables were compared at specific time points and overall throughout surgery. Secondary end-points were CI and SVRI. Heart rate was higher in obese patients in head-up position (79 +/- 15 mmHg vs. 65 +/- 12 mmHg - P=0.011). SVR was higher in the nonobese group with head-up position (1978 +/- 665 dynes s cm(-5) vs. 1394 +/- 496 dynes s cm(-5) P=0.01). Mean overall intraoperative MAP, HR, CI and SVR were similar. There were no episodes of MAP < or = 60 and > or =130 mmHg or HR < or = 50 and > or =110 bpm in either of the groups. Our study confirmed our hypothesis that for the most periods of laparoscopic surgery, obese patients are hemodynamically as stable as their nonobese counterparts.

Noninvasive Hemodynamic Measurements

It has been well established that effective blood pressure (BP) lowering, using various antihypertensive agents with different mechanisms of action, lowers the risk for cardiovascular morbidity and mortality.1–4 However, when hypertensive populations are partitioned into subgroups by race, sex, geography, and age, differences in BP responses to single antihypertensive drugs emerge, albeit at the group level, that have been used to guide therapy for individuals within these contrasted groups.1,5,6 With respect to race, perhaps the most widely used group characteristic used to guide individual therapy, we5 and Sehgal6 have argued that the observed racial differences in BP response overlap to such a large degree that, by far, the greatest source of variation in BP response is within rather than between groups. This observation renders the use of group characteristics as grossly suboptimal criterion on which to base therapy for all individuals of a group. The inaccuracy of blanket extrapolation of group characteristics to predict BP responses for individuals is also likely to be true for traits such as geographic residence, age, and sex. Thus, the findings reported by Smith et al7 in this issue of Hypertension were very encouraging. These investigators showed that consideration of hemodynamic parameters, as determined noninvasively by impedance cardiography (IC) (BioZ, Cardiodynamics), in the selection of antihypertensive therapy in primary care practice settings improved rates of BP control and normalization of selected hemodynamic parameters in drug-treated hypertensives with BP >140/90 mm Hg. They …

Myocardial Contractility and Cardiac Filling Measured by Impedance Cardiography in Patients with Nitroglycerine‐Induced Vasovagal Syncope

Increased myocardial contractility and inadequate cardiac filling leading to activation of the Bezold-Jarisch reflex were proposed as possible triggering mechanisms of vasovagal syncope (VVS). In the present study noninvasive hemodynamic measurements were performed in order to examine the role of myocardial contractility and cardiac filling in pathogenesis of VVS. Hemodynamic parameters were measured during head-up tilt test (HUT) by impedance cardiography in 46 patients with unexplained syncope. Myocardial contractility was measured as index of contractility (IC), acceleration index (ACI), and ejection fraction (EF). Afterload was measured as systemic vascular resistance index (SVRI) and preload was expressed as end-diastolic index (EDI). Serial measurements were done 1 minute before HUT, during HUT at 1-minute intervals, and 1 minute after completion of HUT. HUT was positive in 30 patients (10 men, 20 women, mean age 36 +/- 16 years) and negative in 16 patients (8 men, 8 women, mean age 31 +/- 14 years). No significant differences were observed between HUT(+) and HUT(-) groups in hemodynamic parameters at supine rest and during HUT until the development of syncope. SVRI was lower in HUT(+) than in HUT(-) group at syncope (122.7 + 66.3 vs 185.6 + 51.4 dyn sec cm(-5)/m2, P = 0.002) and after syncope (117.0 + 61.1 vs 198.0 + 95.7 dyn sec cm(-5)/m2, P = 0.007). ACI, IC, EF, and EDI did not differ between groups at syncope. After syncope EF was higher in HUT(+) group compared to HUT(-) group (59.2 + 6.1 vs 52.7 + 9.4%, P = 0.02). The role of increased myocardial contractility and decreased cardiac filling is not confirmed in the present study.

Utility of Impedance Cardiography to Improve Physician Estimation of Hemodynamic Parameters in the Emergency Department

Emergency physicians must often make assessments of complex hemodynamic parameters. To assess the utility of impedance cardiography (ICG) in the emergency department, the authors examined treating physicians' abilities to assess stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) by comparing the clinicians' estimates of these values to ICG measurements. Treating physicians were asked to estimate the SV, CO, and SVR of acutely ill patients as being low, normal, or high. ICG measurements of SV, CO, and SVR were also categorized as low, normal, or high. Physician estimates were compared with ICG measures for concordance. Changes of therapy initiated as a result of discordance between physician's estimates and ICG measurements were recorded. The treating physician assessments and ICG hemodynamic measurements were concordant in 62 of 101 (62%) cases for SV (kappa=0.068), in 53 of 101 (53%) cases for CO (p=0.125), and in 50 of 101 (50%) measurements for SVR (p=0.148). The low concordance suggests that treating physicians did not consistently estimate SV, CO, and SVR accurately. ICG provides noninvasive hemodynamic measurements of SV, CO, and SVR that offer clinical utility and potential value in the emergency department.

Prediction of Intracranial Pressure From Noninvasive Transocular Venous and Arterial Hemodynamic Measurements: A Pilot Study

Continuous measurement of intracranial pressure (ICP) requires the invasive placement of epidural, parenchymal, or intraventricular devices. For critical single-point assessments, lumbar puncture may not always be practical. An accurate, reliable, portable and noninvasive method to estimate absolute ICP remains an elusive goal. The arteries that perfuse and the vein that drains the orbit are exposed to the ambient ICP while coursing through the cerebrospinal fluid or optic nerve. The venous outflow pressure (VOP) of the central retinal vein was measured using occlusion in six intensive care patients treated for acute hydrocephalus or brain hemorrhage and in whom transducers of intracranial pressure could provide standardized continuous output. A novel adaptation of the Balliart ophthalmodynamometer was developed for use. Simultaneously, the central retinal (CRA) and ophthalmic (OA) arterial flow velocities were recorded using color Doppler imaging technique. Repeat noninvasive measurements were performed at various ICPs, (n=22 independently collected observations). Linear regression and correlation testing were performed to evaluate these variables for ICP predictability. The VOP increased linearly with ICP (r=0.87). The arterial pulsatility indices for both OA and CRA decreased inversely with ICP (r=0.66). An empiric index combining both venous and arterial parameters (VOP/Gosling Pulsatility Index [GPI]) was significantly more correlated with absolute ICP than either parameter alone (r=0.95, p<0.005, ICP=0.29+0.74 [VOP/GPI(OA)]). The feasibility to estimate ICP from transocular sonographic and dynamometric data is suggested by these preliminary data. Retinal arterial properties are important in modeling the effect of ICP on the venous outflow pressure. Our pilot results serve as a basis on which to conduct a larger prospective and blinded study.