[Current status of noninvasive hemodynamics in hypertension]. / Estado actual de la hemodinamia no invasiva en hipertensión arterial.

Hypertension is a haemodynamic disorder resulting from a persistent mismatch between cardiac output and peripheral resistance. Hypertension undergoes haemodynamic progression during its natural history. Impedance cardiography is a method of evaluating the cardiovascular system that obtains haemodynamic information from beat to beat through the analysis of variations in the impedance of the thorax on the passage of an electric current. Impedance cardiography unmasks the haemodynamic deterioration underlying the increase in blood pressure as age and systolic blood pressure increases. This method may help to improve blood pressure control through individualized treatment with reduction of peripheral resistance, maintenance of cardiac output or its increase, improvement of arterial compliance and preservation of organ-tissue perfusion. It is useful in the management of patients with resistant hypertension, since a greater percentage of patients controlled with changes in the treatment in relation to the haemodynamic measurements are obtained. Impedance cardiography is important and has prognostic utility in relation to a haemodynamic deterioration pattern and increased cardiovascular events.

Impedance cardiography: a rapid and cost-effective screening tool for cardiac disease.

Impedance cardiography (ICG) charts the rises and falls of thoracic impedance as the fluid content of the chest changes with each heartbeat. Breathing, arrhythmia, movements and posture interfere with the ICG. Modern pattern recognition software can now produce a composite signal-averaged ICG that considerably simplifies interpretation. The first derivative velocity waveform shows a smooth S wave that corresponds with systole, while the second derivative acceleration waveform (dZ/dt) contains several reference points that outline the A, S and O waves. Normally, the A wave follows atrial contraction and occurs in late diastole. It can, therefore, be abnormal in both atrial and ventricular arrhythmias and is abnormally increased when there is diastolic dysfunction. The S wave reflects ventricular contractility and is deformed by ventricular dyssynchrony. The O wave is associated with mitral valve opening and is abnormally enlarged in heart failure. These different patterns of ICG waveform are relatively easy to recognise and can be cost-effectively and quickly obtained to reliably distinguish between normal and abnormal cardiac function.

A new approach for low-cost noninvasive detection of asymptomatic heart disease at rest.

It would be useful to have an inexpensive, noninvasive point-of-care test for early detection of asymptomatic heart disease. This study used impedance cardiography (ICG) in a new way to assess heart function that did not use stroke volume or cardiac output. There is a model of the ICG dZ/dt waveform that may be used as a template to represent normal heart function. The hypothesis was that a dZ/dt waveform which deviates from that template should indicate heart dysfunction and therefore heart disease. The objective was to assess the accuracy of this new ICG approach, using echocardiography as the standard. Thirty-four outpatients undergoing echocardiographic testing were tested by ICG while sitting upright and supine. All patients had no symptoms or history of a structural or functional heart disorder. Echocardiographic testing showed 17 patients with abnormalities and 17 as normal. ICG testing yielded 16 true positives for heart dysfunction with 1 false negative (sensitivity = 94%) and 17 true negatives with no false positives (specificity = 100%). Considering that the cost, technical skill, and time required for this ICG test are comparable to those of an electrocardiograph, this new approach has potential as a point-of-care screening test for asymptomatic heart disease.

Cost-effectiveness of impedance cardiography testing in uncontrolled hypertension.

To evaluate the short- and long-term cost-effectiveness of impedance cardiography (ICG) testing in uncontrolled hypertensives, we analyzed the Consideration of Noninvasive Hemodynamic Monitoring to Target Reduction of Blood Pressure Levels (CONTROL) trial results that compared the blood pressure-lowering effects of standard vs ICG care. Short-term cost-effectiveness was evaluated as the incremental cost per incremental mm Hg reduced during the trial. Long-term cost-effectiveness was evaluated as incremental cost per quality-adjusted life-year gained over 10 years. ICG care short-term cost-effectiveness was 20 US dollar per incremental mm Hg reduced for systolic blood pressure (vs standard care, 36 US dollar per mm Hg reduced) and 23 US dollar per incremental mm Hg reduced for diastolic blood pressure (vs standard care, 79 US dollar per mm Hg reduced). In the long term, ICG resulted in a 476 US dollar cost savings and 0.109 quality-adjusted life-years gained per patient (-4,371 US dollar per quality-adjusted life-year gained, sensitivity analysis -8,764 to 13,163 US dollar). The use of ICG testing to reduce blood pressure in uncontrolled hypertensive patients is cost-effective from both a short- and long-term perspective.

[New noninvasive methods of cardiovascular system function assessment]. / Nowe nieinwazyjne metody oceny funkcji ukladu krazenia.

Increasing development of noninvasive methods of the cardiovascular system assessment as a consequence of increasing experience and technological progress cause more increasing aviability and interest of this techniques from the side of clinicians and scientists. The aim of this study was to present two noninvasive techniques: photoplethysmography and impedance cardiography with explanations of the basis of action, possibilities and limitations. Employment of this two methods opening new perspectives in haemodynamic assessment in many clinical situations for instance: shock, pulmonary edema, heart insufficiency, arterial hypertension and eclampsia. These methods could optimize farmacotherapy or stimulation parameters in patients with heart stimulation as well as to come to know and understand correlations between autonomic nervous system activity and haemodynamic changes. Noninvasivity and low costs of these procedures cause that impedance cardiography and photoplethysmographic blood pressure measurement will become wide use and acceptable methods all over the world.

Evaluation of impedance cardiography as an alternative to pulmonary artery catheterization in critically ill patients.

Invasive pulmonary artery catheterization has historically been the method of choice for the evaluation of hemodynamic status. Impedance cardiography (ICG) is an accurate, noninvasive technique to obtain hemodynamic status information without the risk and cost associated with invasive methods. The purpose of this prospective, observational study was to determine whether the availability of ICG could decrease the need for placement of a pulmonary artery catheter in critically ill patients in coronary care units. After the need for hemodynamic data was determined, ICG parameters were provided to the attending physician who then decided whether pulmonary artery catheter insertion was still necessary. Of 107 subjects enrolled in the study, 14 (13%; 95% confidence interval, 7.3%-21.0%) were judged by the treating physicians to have indications for hemodynamic monitoring. In these subjects, the provision of ICG data allowed the physician to avoid placement of a pulmonary artery catheter in 10/14 patients (71%; 95% confidence interval, 41.9%-91.6%). When ICG was utilized, clinicians reported that the information was helpful in 10/10 patients (100%; 95% confidence interval, 74.1%-100.0%) and improved outcome in 6/10 patients (60%; 95% confidence interval, 26.2%-87.8%). ICG can replace the pulmonary artery catheter in coronary care unit patients, and clinicians utilizing ICG believe it aids medical decision making and improves patient outcomes.

Impedance cardiography (ICG) noninvasive hemodynamic monitoring provides an opportunity to deliver cost effective, quality care for patients with cardiovascular disorders.

Hemodynamic evaluation is an essential component in diagnosing cardiovascular disorders and managing patient care. There are numerous invasive, semi-invasive, and noninvasive methods available for evaluating hemodynamic function, which vary widely in equipment, procedural complexity, cost, quality of data, and risks. This paper summarizes information needed for administrative decision-making about employing one method--ICG hemodynamic monitoring--and provides an overview of the technology, its accuracy and reproducibility, clinical applications, financial consideration and references for further evaluation of the technology.

Advances in continuous, noninvasive hemodynamic surveillance. Impedance cardiography.

In the current climate of shrinking health care reimbursement and increasing importance of patient centered care, impedance cardiography is one method of enhancing quality of patient care and appropriate use of resources. Hemodynamic and thoracic fluid status data may be obtained quickly, accurately, and without risk, providing a global clinical perspective. Patients benefit from the ability to immediately obtain real time hemodynamic data, particularly those patients who otherwise may not be afforded a high level of monitoring or those needing hemodynamic monitoring when assessment and treatment are delayed because of inaccessibility of critical care beds or in the cardiac catheterization laboratory. Application of a technology assessment model to impedance cardiography illustrates the utility of this method of hemodynamic monitoring. Careful review and critique of the literature differentiates the available impedance technologies, supports use in areas not traditionally associated with hemodynamic monitoring, such as the home and emergency department, and validates the use of impedance cardiography in place of, or as an indication for, pulmonary artery catheterization.

The view within: the emerging technology of thoracic electrical bioimpedance.

With the increasing incidence of catheter-related sepsis and recognition of increased mortality and cost of care with pulmonary artery catheters, the need for a safe, cost-effective, and clinically accurate means of obtaining hemodynamic data has become evident. Through the technology of thoracic electrical bioimpedance (TEB), non-invasive hemodynamic monitoring is now possible with the BioZ.com, manufactured by CardioDynamics International Corporation. The BioZ.com provides continuous hemodynamic readings safely, accurately, and inexpensively. TEB is proving to be a valuable adjunct to patient assessment and treatment across multiple health care settings.

Cardiac output measurement in critical care patients: Thoracic Electrical Bioimpedance versus thermodilution.

Thoracic Electrical Bioimpedance (TEB) is a method for measuring cardiac performance which is noninvasive, continuous, has minimal technical requirements, and no patient risk. We used a commercially available TEB device to measure cardiac output in patients with thermodilution catheters in place. We compared the cardiac output measurements for the two modalities. We also compared the average hospital cost for initial cardiac assessment using the two techniques. The mean difference between the two cardiac output measurements was small (0.23 +/- 0.56) and not affected by the magnitude of the cardiac output readings. There was a strong correlation between COTD and COTEB (r = 0.91) and the regression slope was 0.91 with a Y intercept of 0.76. Cost analysis demonstrated that the use of TEB was approximately $600 less than thermodilution. Thoracic electrical bioimpedance measurement of cardiac output may offer a valuable alternative to the invasive measurement of the thermodilution catheter.

A practical, cost-effective, noninvasive system for cardiac output and hemodynamic analysis.

Impedance cardiography is a relatively inexpensive, noninvasive technique for measuring cardiac output on the basis of resistive changes in the thorax to electrical current flow. In conjunction with blood pressure monitoring and physiologic maneuvers, the technique may be used to monitor thoracic and total body fluid volume and express a variety of contractility indexes as well as relative and absolute measurements of stroke volume. We have tested hemodynamics in our laboratory by using a cost-effective, powerful microcomputer-based portable noninvasive technique, which makes possible the ensemble averaging of impedance cardiographic waveforms. In conjunction with physiologic maneuvers, the technique has been implemented at our institution and has provided helpful information in our experience in evaluating volume overload, hypertension, hypotension, shock, and heart failure. It is hoped that this noninvasive, relatively cost-effective approach will be more widely appreciated in the future, given the economic realities of medicine today.