Contrast-enhanced Doppler hemodynamics for noninvasive assessment of patients with chronic heart failure and left ventricular systolic dysfunction.

We sought to evaluate whether contrast-enhanced Doppler echocardiography can improve the noninvasive estimation of hemodynamic variables in left ventricular (LV) dysfunction. Right-heart catheterization and Doppler echocardiography were simultaneously performed in 45 patients with LV dysfunction (ejection fraction: 29 +/- 7%) in sinus rhythm. Noninvasive variables were estimated as follows: cardiac output by pulsed Doppler of LV outflow tract; pulmonary capillary wedge pressure by a regression equation including mitral and pulmonary venous flow variables; pulmonary artery mean pressure from the calculated systolic and diastolic pulmonary artery pressures; and pulmonary vascular resistance from the previous measurements according to hemodynamic definition. Contrast enhancement increased the feasibility of pulmonary capillary wedge pressure estimation from 60% to 100%; of pulmonary artery mean pressure from 42% to 91%; and of pulmonary vascular resistance from 42% to 91%. Strong correlations between invasive and noninvasive hemodynamic variables were found: r = 0.90, standard error of the estimate (SEE) 0.45 L/min for cardiac output; r = 0.90, SEE 3.1 mm Hg for pulmonary capillary wedge pressure; r = 0.93, SEE 3.7 mm Hg for pulmonary artery mean pressure; and r = 0.85 SEE 1.0 Wood units for pulmonary vascular resistance. Weaker correlations for PAMP (r = 0.82, SEE 5.6 mm Hg) and PVR (r = 0.66, SEE 1.7 Wood units) were apparent prior to contrast enhancement. When patients were separated according to PVR threshold values, the contrast allowed the correct placement of 88% of patients, whereas only 57% were correctly assigned without it. The contrast increased accuracy and reduced interobserver variability in the evaluation of hemodynamic variables. The contrast-enhanced study is capable of increasing the value of noninvasive hemodynamic assessment in LV dysfunction.     

Doppler-based hemodynamic monitoring: a minimally invasive alternative

Doppler-based hemodynamic assessment affords a magnitude of diagnostic applications including evaluation of blood flow from the left ventricle. Doppler echocardiography, in the form of transthoracic and transesophageal echocardiography, allows for intermittent evaluation of hemodynamic information including aortic blood flow, global and regional wall motion, and valvular integrity. In the hands of a skilled operator, transthoracic and transesophageal echocardiography provides reliable cardiac output determinations. However, these are not considered routine for hemodynamic monitoring in the critically ill. Neither of the echocardiographic approaches provides the continuously available data needed for ongoing evaluation of response to interventions. In contrast, esophageal Doppler monitoring, a minimally invasive hemodynamic assessment tool, provides the ability for ongoing real-time hemodynamic assessment of the critically ill or compromised patient. This simple-to-use technology requires that a probe, similar in size and shape to a gastric tube, be inserted into the esophagus to obtain measurement of blood flow in the descending aorta. Hemodynamic variables such as cardiac output, preload, afterload, and contractility are measured or derived from the esophageal Doppler monitoring waveform.     

Doppler ultrasound in noninvasive cardiac evaluation. The growing range of applications

Ultrasound is of proven clinical utility for imaging cardiac structures. Doppler ultrasonic techniques can be used with or without echocardiography for noninvasive hemodynamic studies. The usefulness of Doppler ultrasonic techniques in the noninvasive laboratory has been shown recently at the Massachusetts General Hospital, Boston. In 61 of 100 consecutive patients in a prospective study, Doppler ultrasound provided clinical information that could not be obtained with echocardiographic studies alone. The advantages of this technique for noninvasive cardiac studies are now being recognized in the general medical community. The results of ongoing clinical investigations will help define the role of Doppler echocardiography as a clinically useful diagnostic tool for cardiac evaluation.     

Evolution of the continuity equation in the Doppler echocardiographic assessment of the severity of valvular aortic stenosis

The use of Doppler techniques has greatly enhanced the noninvasive ultrasound technique for evaluation of valvular aortic stenosis. M-mode and two-dimensional echocardiography could not reliably distinguish patients with severe aortic stenosis from those with milder obstructions. The hemodynamic information offered by Doppler complemented echocardiographic imaging and provided an alternative modality for evaluation of patients with aortic stenosis. By application of the modified Bernoulli equation, the pressure gradient across the stenotic aortic valve could be estimated by Doppler echocardiography. Though helpful and widely used, the information provided by the pressure gradient across the valve about the severity of the obstruction was not complete. The assessment of valvular aortic stenosis therefore includes an estimation of the valve area by application of the continuity equation. This review examines the maturation of the continuity equation by Doppler techniques and discusses the implications of the procedure.     

Doppler spectrum analysis versus direct femoral artery pressure measurement for rapid assessment of aortoiliac obstruction.

Adequate patient selection is required to limit the clinical workload and improve the cost-effectiveness of noninvasive hemodynamic evaluation of the aortoiliac system. In a prospective blinded fashion the traditional invasive technique of direct femoral artery pressure measurements and the computerized Doppler spectrum analysis of blood flow velocities in the common femoral artery were studied. Both tests for rapid assessment of aortoiliac obstruction were compared with duplex ultrasonographic imaging, using a peak systolic velocity ratio of 2.5 to demonstrate stenoses of 50% or more. In a series of 17 consecutive patients (34 aortoiliac segments) with suspected aortoiliac obstructive disease, a good level of agreement (kappa = 0.6) was found for both methods when compared with duplex scanning. Analysis of deviations from the duplex registrations indicated an overestimation of the pathologic cases using femoral artery pressure measurements and an underestimation using Doppler spectrum analysis of blood flow velocities in the common femoral artery. Both methods were well tolerated, but femoral artery pressure measurements had a higher technical failure rate. Because of its noninvasive character and its feasibility the Doppler technique is preferred for the selection of patients for more extensive duplex sonographic investigation.     

Clinical utility of Doppler ultrasound in cardiac diseases

During the past decade Doppler echocardiography has evolved to an extent that it has become a major noninvasive tool for cardiac evaluation in both acquired and congenital heart disease. This article describes current applications of Doppler techniques in the evaluation of cardiac anatomy and hemodynamics. The principles and methods employed in the use of Doppler echocardiography are described and illustrated for assessment and quantitation of flow velocities, pressure gradients, valve areas, valve regurgitation, stroke volume, cardiac output, cardiac shunts, and diastolic filling indices. The increasing accuracy of these applications has led to a substantial reduction in the need for invasive diagnostic methods, such as cardiac catheterization, especially in patients where frequent follow-up evaluations are indicated.     

Occult cardiac tamponade detected by transesophageal echocardiography.

Transesophageal echocardiography is a safe, minimally invasive procedure that should be considered when the diagnosis of cardiac tamponade is a possibility and when conventional methods fail to provide conclusive diagnostic information. In this report, we describe a 74-year-old man in the intensive-care unit whose condition was unstable postoperatively because of an occult loculated pericardial effusion and cardiac tamponade. Routine noninvasive and invasive monitoring, including hemodynamic monitoring and transthoracic echocardiography, failed to confirm definitively the suspected diagnosis of cardiac tamponade. In addition, because of the hemodynamic instability of the patient, transporting him for definitive tests (such as fast computed tomographic scanning of the mediastinum, which could not be performed at the bedside) for assessment of cardiac tamponade was relatively contraindicated. In our patient, the diagnostic information obtained by transesophageal echocardiography may have been lifesaving.     

Assessment of valve disease: qualitative and quantitative

Evaluation of valve disease has changed significantly with the development of color Doppler echocardiography. Nevertheless, this technique has limitations, particularly in the assessment of valvular regurgitation. MR imaging, with its ability to provide three-dimensional morphologic data, dynamic cine information, and functional evaluation with flow-sensitive techniques, can be envisioned as a complementary noninvasive modality, able to provide the complete information required for planning therapeutic options. With MR imaging, qualitative as well as accurate and reproducible quantitative information such as volume measurements, cardiac function, and flow velocity profiles are unique for the evaluation of the severity of valve disease. This article reviews the different MR imaging techniques used in assessing valvular heart disease and discusses the advantages and limitations of these techniques in current clinical applications in comparison with classical imaging methods.     

Noninvasive evaluation of stroke risk in patients with subclavian steal

In patients with subclavian steal (SS), the risk of stroke must be evaluated before angiographic assessment or surgery is performed. The criteria for the evaluation of stroke risk in these patients have not yet been established. SS is a hemodynamic phenomenon that sometimes produces no clinical symptoms and is sometimes associated with neurologic symptoms. Transcranial Doppler provides a noninvasive method of obtaining information on cerebral hemodynamics; this information can be useful in the pathophysiologic evaluation of stroke risk. Transcranial Doppler findings from 63 patients (28 asymptomatic) (mean age, 56.4 years) with SS collected over a 4-year period were classified on the basis of the levels of hemodynamic changes within the intracranial circulation. The Doppler study findings revealed a significant association (P < 0.01, by chi-square test) only with neurologic symptoms, demonstrating hemodynamic involvement of the carotid-basilar collateral pathways.     

Doppler echocardiography: application to the assessment of successful thrombolysis of prosthetic valve thrombosis

Prosthetic valve thrombosis remains a significant problem despite anticoagulation therapy and advances in valve design. Thrombolytic therapy offers an alternative approach to valve replacement in patients with high surgical risk. In this article we discuss three cases in which Doppler echocardiography was used to confirm the diagnosis of prosthetic mitral valve obstruction and serially monitor the response of valvular hemodynamic measurements to thrombolysis with intravenous streptokinase. These cases illustrate how the Doppler technique, in addition to allowing the noninvasive diagnosis of prosthetic valve obstruction, is presently the ideal tool to follow serially the effect of thrombolytic therapy on prosthetic valve function.     

Coronary anomalies diagnosed with transesophageal echocardiography: complementary clinical value in adults

Introduction. Coronary arteriography remains a gold standard for the evaluation of coronary anatomy. In the case of anatomical anomalies, understanding of vessel course based upon a coronary angiogram may be difficult. Transesophageal echocardiography is a noninvasive method allowing tomographic visualization of proximal coronary arteries. Experience concerning its usefulness for the assessment of anomalous coronary arteries is limited. Material. Eleven patients with confirmed coronary anomalies studied between 1993-96 were identified in the cohort of those undergoing transesophageal echocardiography. Results. Transesophageal echocardiography revealed potentially serious anomalies (origin of left or right coronary artery from contralateral aortic sinus) in 3 patients and benign in 8. Coronary ostia and proximal course could be delineated in all patients. Anatomical information was consistent between methods, except for a separate origin of the left anterior descending and circumflex artery, where the angiogram missed a very short common left main coronary artery in 2 patients. The relationship between the coronary arteries, aorta and pulmonary trunk was better defined by the echocardiogram. Doppler flow analysis allowed us to exclude anomaly-related flow disturbances. Conclusions. Transesophageal echocardiography can be considered as a noninvasive technique with the potential for anatomical and functional evaluation of anomalous proximal coronary arteries and deserves a routine use whenever such a condition is suspected. This approach may simplify invasive procedures in this patient group.     

Noninvasive assessment and necropsy validation of changes in left ventricular mass in ascending aortic banded mice.

Although left ventricular (LV) hypertrophy can be induced by aortic banding, noninvasive assessment of changes in LV mass in mice with a banded ascending aorta by using 2-dimensional (2D) images has not been previously performed. In this study we serially assessed changes in LV mass by 2D echocardiography with a newly available 12-MHz transducer in mice with a banded ascending aorta and validated measurements at necropsy. Estimated by echocardiography, LV mass increased from 74+/- 17 mg before banding to 191.08+/-54 mg at 8 weeks after banding (P <.0001), and excellent correlation was shown with postmortem measurements (r = 0.97). Furthermore, with the use of pulsed Doppler 2-dimensionally guided echocardiography, noninvasive measurement of flow velocities in the ascending aorta before and after the band at the various time points was possible. We propose that 2D echocardiography with a 12-MHz transducer is a powerful tool for serial noninvasive evaluations as an adjunct to the study of cardiac hypertrophy in the murine model.     

Noninvasive monitoring of peripheral perfusion

Background Early hemodynamic assessment of global parameters in critically ill patients fails to provide adequate information on tissue perfusion. It requires invasive monitoring and may represent a late intervention initiated mainly in the intensive care unit. Noninvasive monitoring of peripheral perfusion can be a complementary approach that allows very early application throughout the hospital. In addition, as peripheral tissues are sensitive to alterations in perfusion, monitoring of the periphery could be an early marker of tissue hypoperfusion. This review discusses noninvasive methods for monitoring perfusion in peripheral tissues based on clinical signs, body temperature gradient, optical monitoring, transcutaneous oximetry, and sublingual capnometry.Discussion Clinical signs of poor peripheral perfusion consist of a cold, pale, clammy, and mottled skin, associated with an increase in capillary refill time. The temperature gradients peripheral-to-ambient, central-to-peripheral and forearm-to-fingertip skin are validated methods to estimate dynamic variations in skin blood flow. Commonly used optical methods for peripheral monitoring are perfusion index, near-infrared spectroscopy, laser Doppler flowmetry and orthogonal polarization spectroscopy. Continuous noninvasive transcutaneous measurement of oxygen and carbon dioxide tensions can be used to estimate cutaneous blood flow. Sublingual capnometry is a noninvasive alternative for gastric tonometry.This study was in part supported by materials provided by Hutchinson Technology and a grant from Philips USA. Both authors received a grant US $12,000 from Philips USA and $10,000 from Hutchinson Technology.     

Noninvasive Hemodynamic Monitoring of Critical Patients in the Emergency Department

Objective : To evaluate the feasibility of multicomponent noninvasive hemodynamic monitoring in critical emergency patients and to compare this technique with simultaneous invasive monitoring by the pulmonary artery thermodilution catheter.
Methods : A prospective observational study was done comparing invasive monitoring and noninvasive monitoring in 60 critically ill or injured patients who required hemodynamic monitoring shortly after entering the ED of a university-affiliated county hospital. Cardiac output (CO) values measured by the standard thennodilution pulmonary artery catheter technique were compared with simultaneously obtained measurements using a noninvasive bioimpedance method. Concurrent measurements were made of pulse oximetry to screen pulmonary function and transcutaneous oximetry to assess tissue perfusion.
Results : The impedance CO values closely approximated those for the thermodilution method; r 0.81, p < 0.001. Significant circulatory abnormalities, including hypotension, reduced cardiac index, arterial hemoglobin desaturation, tissue hypoxia, reduced O₂ delivery, and consumption, were found in 54 of the 60 (90%) patients. The cardiac index decreased in 44% of the patients, the transcutaneous O₂ decreased in 39%. and the O₂ saturation by pulse oximetry fell in 22% during the observation period in the ED (commonly lasting 2–8 hours).
Conclusions: Noninvasive monitoring can provide hemodynamic and perfusion information previously available only by invasive thermodilution catheters. Such noninvasive monitoring can display continuous on-line real-time data, allowing immediate recognition of circulatory abnormalities and providing a means to titrate therapy to appropriate therapeutic goals.     

Noninvasive assessment of flow velocity and flow velocity reserve in the right gastroepiploic artery graft by transcutaneous Doppler echocardiography: comparison with an invasive technique.

BACKGROUND: The measurement of flow velocity (FV) in coronary artery bypass grafts using a Doppler guidewire has provided useful clinical and physiologic information. The recently developed transcutaneous Doppler echocardiography is a noninvasive technique to measure FV and FV reserve (FVR) in the right gastroepiploic artery (GEA) graft. The purpose of this study was to evaluate whether transcutaneous Doppler echocardiography accurately measures FV and FVR in the right GEA graft in a clinical setting. METHODS: In 33 patients who underwent graft angiography for the assessment of the right GEA graft, FV in the right GEA graft was measured by transcutaneous Doppler echocardiography under the guidance of color flow Doppler imaging at the time of examination using a Doppler guidewire. FV in the midportion of the right GEA graft was measured at baseline and during hyperemic conditions using both transcutaneous Doppler echocardiography and a Doppler guidewire. RESULTS: There were excellent correlations between the value of FV obtained by transcutaneous Doppler echocardiography and those obtained with the Doppler guidewire (averaged peak velocity: y = 0.95 x + 1.46, r = 0.98, standard error of the estimate [SEE] = 2.94 cm/s; averaged systolic peak velocity: y = 0.94 x + 1.18, r = 0.97, SEE = 3.15 cm/s; diastolic peak velocity: y = 0.97 x + 1.62, r = 0.98, SEE = 4.40 cm/s; averaged diastolic peak velocity: y = 0.95 x + 1.75, r = 0.98, SEE = 3.60 cm/s). The FVR as determined by transcutaneous Doppler echocardiography showed a good correlation with that determined using the Doppler guidewire method (y = 0.90 x + 0.21, r = 0.92, SEE = 0.31). CONCLUSIONS: Transcutaneous Doppler echocardiography proved to be an accurate noninvasive method to measure FV and FVR in the right GEA graft.     

Brachial artery peak velocity variation to predict fluid responsiveness in mechanically ventilated patients

Introduction  

Although several parameters have been proposed to predict the hemodynamic response to fluid expansion in critically ill patients, most of them are invasive or require the use of special monitoring devices. The aim of this study is to determine whether noninvasive evaluation of respiratory variation of brachial artery peak velocity flow measured using Doppler ultrasound could predict fluid responsiveness in mechanically ventilated patients.     

Hemodynamic assessment of critically ill patients using echocardiography Doppler

PURPOSE OF REVIEW: The evaluation of hemodynamic status in critically ill patients is a leading recommended indication of transesophageal echocardiography in the intensive care unit. Advantages and diagnostic yield of transesophageal echocardiography in this setting are particularly relevant when considering limitations and questioned prognostic impact of pulmonary artery catheterization. RECENT FINDINGS: Recent clinical studies have been performed to validate and assess the value of transesophageal echocardiography in determining cardiac output, cardiac preload dependence, right ventricular function, and left ventricular filling pressure. In addition, diagnostic capacity and therapeutic impact of transesophageal echocardiography have been widely reported in various intensive care unit settings. SUMMARY: Transesophageal echocardiography appears well suited for the determination of cardiac index and to track its variations after therapeutic interventions. Although repeated measurements of left ventricular end-diastolic dimension allows to accurately track preload variations, a single determination is not reliable to predict fluid responsiveness in intensive care unit patients. Identification of preload dependence in hemodynamically unstable patients currently tends to rely mainly on dynamic parameters that use cardiopulmonary interactions under mechanical ventilation. Transesophageal echocardiography also allows to adequately assess right ventricular function and left ventricular filling pressure using combined Doppler modalities. Adequate education and training of intensivists and anesthesiologists is crucial to further develop the use of transesophageal echocardiography in the intensive care unit setting. Despite the absence of randomized controlled studies documenting transesophageal echocardiography benefits on patient outcome, present evidence and experience strongly recommend a larger use of echocardiography Doppler for a comprehensive functional hemodynamic assessment of critically ill patients with circulatory failure.     

A practical approach to the echocardiographic evaluation of diastolic function.

A number of recent community-based epidemiologic studies suggest that 40% to 50% of the cases of heart failure have preserved left ventricular systolic function. Although diastolic heart failure is often not well clinically recognized, it is associated with marked increases in morbidity and all-cause mortality. Doppler echocardiography has emerged as the principal clinical tool for the assessment of left ventricular diastolic function. Doppler mitral inflow velocity-derived variables remain the cornerstone of the evaluation of diastolic function. Pulmonary venous Doppler flow indices and mitral inflow measurements with Valsalva's maneuver are important adjuncts for differentiating normal and pseudonormal mitral inflow patterns. Unfortunately, these Doppler flow variables are significantly influenced by loading conditions and, therefore, the results from these standard techniques can be inconclusive. Recently, color M-mode and Doppler tissue imaging have emerged as new modalities that are less affected by preload and, thus, provide a strong complementary role in the assessment of diastolic function. This review will discuss the diastolic properties of the left ventricle, Doppler echocardiographic evaluation, and grading of diastolic dysfunction.     

Évaluation des pressions de remplissage ventriculaire gauche par échocardiographie-doppler

The evaluation of left ventricular (LV) filling pressures is crucial to identify a congestive heart failure in a patient presenting with an acute respiratory failure. This evaluation traditionally relies on the invasive measurement of the pulmonary artery occlusion pressure during right heart catheterization. Echocardiography Doppler is an unparalleled alternative technique to assess LV filling pressures, which also provides anatomical and functional information on the heart and great vessels. Pulsed wave Doppler of the mitral valve and pulmonary veins provides indices that are easy to measure and allow a semi-quantitative assessment of LV filling pressures. Their accuracy increases in the presence of a LV systolic dysfunction. New Doppler indices, which assess more specifically LV diastolic properties (Doppler Tissue Imaging of the mitral ring, color M-mode propagation velocity) can be combined to traditional Doppler parameters to more precisely assess LV filling pressures. In addition, echocardiography allows a comprehensive assessment of both the left and right ventricular function, the diagnosis of an underlying cardiopathy, or the identification of an acute condition of the heart or great vessels that precipitated the acute respiratory failure. Accordingly, echocardiography Doppler is a cornerstone in the evaluation of patients presenting to the intensive care unit with a respiratory failure and a high index of suspicion of pulmonary venous congestion. This imaging modality is particularly valuable for the evaluation of patients with a medical history of chronic respiratory failure and cardiac failure, to confirm or confidently rule out a cardiogenic pulmonary edema, or to identify a cardiac source of ventilator weaning failure.     

Tissue Doppler imaging: A useful echocardiographic method for the cardiac sonographer to assess systolic and diastolic ventricular function

Tissue Doppler imaging (TDI) has evolved to become a useful noninvasive method that can complement other echocardiographic techniques in the assessment of left ventricular myocardial velocities in a variety of clinical conditions. Color 2-dimensional and color M-mode TDI are used for quantification of systolic myocardial velocities during myocardial ischemia at rest and with pharmacologic stress testing. Spectral pulsed TDI can provide measurements of regional systolic and diastolic myocardial velocities, and it is particularly useful in the identification of abnormalities of left ventricular diastolic relaxation. This review summarizes the clinical applications of TDI to promote understanding of its utility in the evaluation of left ventricular myocardial function.