Noninvasive estimation of the instantaneous first derivative of left ventricular pressure using continuous-wave Doppler echocardiography

Doppler-derived left ventricular rate of pressure rise and inotropic requirements during mitral valve surgery

BACKGROUND

The estimation of left ventricular (LV) contractility is difficult in the presence of significant mitral regurgitation (MR). Prediction of LV performance after MR repair is even more problematic. The intraoperative Doppler-derived LV rate of pressure rise (LV delta P/delta t) analyzed before cardiopulmonary bypass (CPB) was presumed to be a useful predictive parameter for LV performance. Therefore, its relation to perioperative inotropic requirements (PIR) necessary for separation from CPB after surgical MR repair was investigated.

METHODS

Twenty-eight patients scheduled for surgical MR repair fulfilled the selection criteria. Pre-CPB LV delta P/delta t, pre-CPB echocardiographic LV fractional area change (LV FAC), and pre-CPB thermodilution-derived cardiac index (CI) were recorded. After MR repair, separation from CPB was performed with regard to standardized guidelines. PIR during the first 60 minutes following separation were recorded.

RESULTS

Pre-CPB LV delta P/delta t could be assessed in 22 patients. Pre-CPB LV delta P/delta t was 882 +/- 450 mmHg/sec, pre-CPB LV FAC was 49% +/- 9%, and pre-CPB CI was 2.0 +/- 0.2 L/kg/min. Pre-CPB LV delta P/delta t was significantly correlated with pre-CPB LV FAC (r = 0.56), and with pre-CPB CI (r = 0.72). Inotropic support was necessary in 16 patients (73%), and was best predicted by the pre-CPB LV delta P/delta t, by means of logistic regression (p = 0.026).

CONCLUSIONS

Doppler-derived LV delta P/delta t was assessable in most patients with severe chronic MR, and was the best intraoperative predictive parameter of post-CPB inotropic requirements after surgical MR repair.

Echocardiography for hemodynamic assessment of patients with advanced heart failure and potential heart transplant recipients

OBJECTIVES

This study sought to assess the accuracy of Doppler echocardiographic techniques for the determination of right heart catheterization hemodynamic variables in patients with advanced heart failure and in potential heart transplant recipients.

BACKGROUND

Doppler echocardiographic techniques permit the noninvasive acquisition of hemodynamic variables traditionally used for the assessment of patients with advanced heart failure and potential heart transplant candidates. However, the accuracy of these techniques has not been sufficiently well documented for clinical application in individual patients.

METHODS

Echocardiographic data required for estimation of mean right atrial, pulmonary artery and mean left atrial pressures and cardiac output were obtained. Right heart catheterization was performed immediately after Doppler echocardiographic data were acquired, before any intervention that might have altered the subject's hemodynamic status.

RESULTS

A complete Doppler echocardiographic hemodynamic data set was acquired in 21 (84%) of 25 subjects. For all variables, invasive and noninvasive hemodynamic values were highly correlated (p < 0.001), with minimal bias and narrow 95% confidence limits. An algorithm constructed from the noninvasive hemodynamic variable values identified all patients with adverse pulmonary vascular hemodynamic variables (i.e., transpulmonary gradient > or = 12 mm Hg, pulmonary vascular resistance > or = 3 Wood units or pulmonary vascular resistance index > or = 6 Wood units x m2). This algorithm identified 12 (71%) of 19 patients for whom right heart catheterization was unnecessary.

CONCLUSIONS

Doppler echocardiographic estimates of hemodynamic variables in patients with advanced heart failure are accurate and reproducible. This noninvasive methodology may assist with monitoring and optimization of medical therapy in patients with advanced heart failure and may obviate the need for routine right heart catheterization in potential heart transplant candidates.

Comparison Between the Mean dP/dt During Isovolumetric Contraction and Other Echocardiographic Indexes of Ventricular Systolic Function

Echocardiographic assessments of ventricular function derived from estimates of the mean dP/dt during isovolumetric contraction (mean dP/dt(ic)) were compared with those obtained from measurements of the shortening fraction and the stress-velocity index (SVI). Mean dP/dt(ic) correlated well with the shortening fraction, r = 0.74, P < 0.0001. Furthermore, 10 out of 11 patients with mean dP/dt(ic) below 800 had a shortening fraction < 0.28, whereas all patients with a mean dP/dt(ic) > 1000 mmHg/sec had a shortening fraction > 0.28. A good correlation also existed between mean dP/dt(ic) and the SVI, r = 0.73, P < 0.0001. Nine out of 11 patients with a mean dP/dt(ic) < 800 mmHg/sec had an SVI > 2 standard deviations below normal, whereas all patients with mean dP/dt(ic) > 1000 mmHg/sec had normal or increased SVI. The correlation between mean dP/dt(ic) and the SVI was strengthened when mean dP/dt(ic) was adjusted for heart rate and preload. Hence, assessments of ventricular function derived from measurements of mean dP/dt(ic) appear to agree well with those provided by the shortening fraction and SVI. Because the determination of mean dP/dt(ic) is not hampered by unusual anatomy or wall motion (conditions which compromise the validity of the shortening fraction and SVI), mean dP/dt(ic) may be a good index of ventricular function in cases where measurements of the shortening fraction and SVI would be unreliable.

[Usefulness of the Doppler index delta P/delta t in the evaluation of left ventricular systolic dysfunction]

INTRODUCTION AND OBJECTIVES

It has been shown that the delta P/delta t index, derived from the continuous Doppler mitral regurgitation signal correlates strongly with dP/dt. This study evaluates the feasibility, reproducibility and correlation of the index with ejection fraction and other conventional echocardiographic parameters.

MATERIAL AND METHODS

One hundred and ten patients with mitral regurgitation demonstrated by colour Doppler were studied. delta P/delta t were calculated by the ratio between the interval of pression between two points of the Doppler signal (-1 and -3 m/s; 32 mmHg, applying the modified Bernouilli equation) and the interval of time (s) which separates both. Ejection fraction was measured in 70 patients by non-echocardiographic methods (isotopic ventriculography, n = 52, and angiography, n = 18).

RESULTS

The index was feasible in 91 cases, the variability of intra and interobserver was 5% and 7% respectively. The correlation between delta P/delta t and ejection fraction was significant although weak (r = 0.59; p < 0.001; n = 70). It was better in the group of dilated idiopathic myocardiopathy (r = 0.72; p < 0.001; n = 18) than in the group of myocardial infarction (r = 0.54; p < 0.01; n = 25). No significant correlation was founded in the cases with mitral rheumatic valvulopathy. Regarding to the echocardiographic parameters, the best correlation was obtained with end systolic diameter (r = -0.64; p < 0.001; n = 49). Finally, a value of delta P/delta t < 1,000 mmHg/s predicted the existence of left ventricular systolic dysfunction with high accuracy (84%), sensitivity (80%) and specificity (92%).

CONCLUSIONS

High feasibility when mitral regurgitation exists, adequate reproducibility and heightened precision in diagnosing left ventricular systolic dysfunction, are characteristics which make delta P/delta t useful in the echocardiographic routine practice.

Computation of flow pressure fields from magnetic resonance velocity mapping

Magnetic resonance phase velocity mapping has unrivalled capacities for acquiring in vivo multi-directional blood flow information. In this study, the authors set out to derive both spatial and temporal components of acceleration, and hence differences of pressure in a flow field using cine magnetic resonance velocity data. An efficient numerical algorithm based on the Navier-Stokes equations for incompressible Newtonian fluid was used. The computational approach was validated with in vitro flow phantoms. This work aims to contribute to a better understanding of cardiovascular dynamics and to serve as a basis for investigating pulsatile pressure/flow relationships associated with normal and impaired cardiovascular function.

Quantitative Doppler tissue imaging as a correlate of left ventricular contractility

Doppler tissue imaging is a new noninvasive imaging modality that allows quantitation of the low intensity, high amplitude Doppler shifts in the range of myocardial tissue motion. This study was performed to test the hypothesis that Doppler tissue imaging may provide unique information reflecting left ventricular systolic function, and to test the relationship between myocardial tissue velocity and noninvasive measures of ventricular contractility. Nine patients with mild or moderate mitral insufficiency and no regional wall motion abnormality were studied during dobutamine stress echocardiography. Left ventricular ejection fraction and peak systolic velocity of the sub-endocardial left ventricular posterior wall were quantified at baseline and at peak stress and compared with estimated peak dP/dt. During dobutamine infusion, ejection fraction increased from 41.7 +/- 22.2 (range 14 to 70) % to 56.6 +/- 27.9 (range 17 to 84)% (p = 0.001), peak systolic velocity increased from 22.7 +/- 4.2 (range 18 to 28) mm/sec to 35.3 +/- 10.1 (range 20 to 47) mm/sec (p = 0.004), and dP/dt increased from 1050 +/- 322 (range 613 to 1574) mm Hg/sec to 1766 +/- 768 (range 936 to 3000) mm Hg/sec (p = 0.01). Although there were good correlations between left ventricular dP/dt and both ejection fraction (R = 0.75) and peak systolic velocity (R = 0.81), the correlation between change in dP/dt and change in myocardial velocity (R = 0.75) was better than that between change in dP/dt and change in ejection fraction (R = 0.36). These data support the hypothesis that myocardial velocity determined with Doppler tissue imaging reflects myocardial contractility, and that catecholamine-induced alteration in contractility is better reflected by changes in myocardial velocity than by changes in ejection fraction.

Quantification of Mitral and Tricuspid Regurgitation Using Jet Centerline Velocities: An In Vitro Study of Jets in an Ambient Counterflow

A method for quantifying mitral and tricuspid regurgitant volume that utilizes a measure of jet orifice velocity U(0) - m/sec), a distal centerline velocity (U(m) - m/sec), and the intervening distance (X - cm) was recently developed; where jet flow rate (Q(cal) - L/min) is calculated as Q(cal) = (U(m)X)(2)/(26.46U(o)). This method, however, modeled the regurgitant jet as a free jet, whereas many atrial jets are counterflowing jets because of jet opposing intra-atrial flow fields (counterflows). This study concentrated on the feasibility of using the free jet quantification equation in the atrium where ambient flow fields may alter jet centerline velocities and reduce the accuracy of jet flow rate calculations. A 4-cm wide chamber was used to pump counterflows of 0, 4, and 22 cm/sec against jets of 2.3, 4.8, and 6.4 m/sec originating from a 2-mm diameter orifice. For each counterflow-jet combination, jet centerline velocities were measured using laser Doppler anemometry. For free jets (no counterflow), flow rate was calculated with 98% mean accuracy. For all jets in counterflow, the calculation was less accurate as: (i) the ratio of jet orifice velocity to counterflow velocity decreased (U(o)/U(c), where U(c) is counterflow velocity), i.e., the counterflow was relatively more intense, and (ii) centerline measurements were made further from the orifice. But although counterflow lowered jet centerline velocities beneath free jet values, it did so only significantly in the jet's distal portion (X/D > 16, i.e., >16 orifice diameters from the origin of the jet). Thus, the initial portion (X/D < 16) of a jet in counterflow behaved essentially as a free jet. As a result, even in significant counterflow, jet flow rate was calculated with >93% accuracy and >85% for jets typical of mitral and tricuspid regurgitation, respectively. Counterflow lowers jet centerline velocities beneath equivalent free jet values. This effect, however, is most significant in the distal portion of the jet. Therefore, regurgitant jets, although not classically free because of systolic atrial inflow or jet-induced intra-atrial swirling flows, will decay in their initial portions as free jets and thus are candidates for quantification with the centerline technique. (ECHOCARDIOGRAPHY, Volume 13, July 1996)

Newer Doppler measures of left ventricular diastolic function

Left ventricular (LV) diastolic dysfunction is an important cause of heart failure, and recent advances in the application of Doppler techniques allow a semiquantitative assessment of LV diastolic performance. This review discusses the use of Doppler echocardiography in the comprehensive assessment of LV diastolic function and performance in terms of the normal mitral and pulmonary venous flow profiles, their physiologic basis, and alterations in diseased states. There is also a discussion on the newer aspects of mitral flows such as relative durations of mitral A and pulmonary vein AR waves, E- and A- wave propagation inside the LV with their hemodynamic correlates, and derivation of ventricular dP/dt and Tau from the mitral regurgitation velocity profile. Analysis of these flow profiles and the other Doppler measures alluded to above allow one to make a fairly precise hemodynamic assessment of a patient in terms of left atrial pressure, LV relaxation and stiffness and the profile of LV diastolic pressure in terms of pre- 'a' wave and 'a' wave pressures and ventricular end-diastolic pressure.

Echocardiography assessment of left ventricular function in the critically ill

Echocardiography is fast becoming the technique of choice for noninvasive evaluation of left ventricular function in the critically ill patient. Current technology allows for assessment of overall left ventricular performance and for diastolic and systolic function. Doppler technology has greatly enhanced the diagnostic capability of two-dimensional echocardiography. The critical care physician should be aware not only of currently available techniques, but also those which will be used in the routine care of the critically ill subject in the foreseeable future.

Comparison of simultaneous Doppler- and catheter-derived right ventricular dP/dt in hypoplastic left heart syndrome

Doppler estimation of RV dP/dt correlates well with micromanometer catheter-measured values in children with hypoplastic left heart syndrome. Doppler estimation of RV dP/dt is a method of quantifying RV systolic function independent of geometric assumptions, and may be a valuable method for longitudinal analysis of RV function.

New method for accurate calculation of regurgitant flow rate based on analysis of Doppler color flow maps of the proximal flow field. Validation in a canine model of mitral regurgitation with initial application in patients

OBJECTIVES

The purpose of this study was to develop a rational and objective method for selecting a region in the proximal flow field where the hemispheric formula for calculating regurgitant flow rates by the flow convergence technique is most accurate.

BACKGROUND

A major obstacle to clinical implementation of the proximal flow convergence method is that it assumes hemispheric isovelocity contours throughout the Doppler color flow map, whereas contour shape depends critically on location in the flow field.

METHODS

Twenty mitral regurgitant flow rate stages were produced in six dogs by implanting grommet orifices into the anterior mitral leaflet and varying driving pressures so that actual peak flow rate could be determined from the known effective regurgitant orifice times the orifice velocity. Because plotting flow rate calculated by using a hemispheric formula versus alias velocities produces underestimation near the orifice and overestimation far from it, this plot was fitted to a polynomial function to allow identification of an inflection point within a relatively flat intermediate zone, where factors causing overestimation and underestimation are expected to be unimportant or balanced. The accuracy of flow rate calculation by the inflection point was compared with unselective and selective averaging techniques. Clinical relevance, initial feasibility and correlation with an independent measure were tested in 13 consecutive patients with mitral regurgitation who underwent cardiac catheterization.

RESULTS

1) The accuracy of single-point calculations was improved by selecting points in the flat portion of the curve (y = 1.15x - 3.34, r = 0.87, SEE = 22.1 ml/s vs. y = 1.34x - 1.99, r = 0.71, SEE = 45.6 ml/s, p < 0.01). 2) Selective averaging of points in the flat portion of the curve further improved accuracy and decreased scatter compared with unselective averaging (y = 1.08x + 4.8, r = 0.96, SEE = 11.6 ml/s vs. y = 1.30x + 0.6, r = 0.90, SEE = 20.9 ml/s, p < 0.01). 3) The proposed algorithm for mathematically identifying the inflection point provided the best results (y = 0.96x + 4.5, r = 0.96, SEE = 9.9 ml/s), with a mean error of 1.6 +/- 9.7 ml/s vs. 11.4 +/- 11.7 ml/s for selective averaging (p < 0.01). In patients, the proposed algorithm identified an inflection point at which calculated regurgitant volume agreed best with invasive measurements (y = 1.1x - 0.61, r = 0.93, SEE = 17 ml).

CONCLUSIONS

The accuracy of the proximal flow convergence method can be significantly improved by analyzing the flow field mathematically to identify the optimal isovelocity zone before using the hemispheric formula to calculate regurgitant flow rates. Because the proposed algorithm is objective, operator independent and, thus, suitable for automatization, it could provide the clinician with a powerful quantitative tool to assess valvular regurgitation.

Quantitative Echoca rdiograpy Part III

A comprehensive two-dimensional echocardiographic examination provides useful information that is superior to MT-mode regarding left ventricular chamber sizes and systolic performance, including ejection fraction. Although we rely on visual estimates, quantitative measurements can be particularly valuable in patients with mild or moderate left ventricular systolic dysfunction. Measurements of left ventricular mass by two-dimensional echocardiography is supenror to Ml-mode to detect left ventricular hypertrophy. Two-dimensional echocardiography combined with pulsed Doppler echocardiography can be used to accurately measure stroke volume and to assess changes during medical therapy or after interventions. Future work is needed to assess the significance of continuous-wave Doppler-derived rate of pressure change in patients with mitral regurgitation.

Mechanisms, diagnosis, and treatment of diastolic heart failure

Diastolic heart failure, in the absence of LV systolic dysfunction, is a common clinical condition that can be demonstrated in as many as one third of patients with congestive heart failure. Diastolic dysfunction caused by abnormalities in LV filling can be a result of many pathologic conditions, including hypertrophy, infiltrative cardiomyopathies, or myocardial ischemia. The major physiologic determinants of LV filling can be divided into cellular mechanisms, hemodynamic characteristics, and hormonal influences. Cellular mechanisms for impaired LV inactivation are determined by the handling of calcium within the myocyte during excitation-contraction-relaxation coupling. The hemodynamic characteristics of LV diastolic filling are determined by loading conditions, the time constant of isovolumic relaxation, heart rate, ventricular nonuniformity, pericardial restraint, myocardial elasticity, chamber compliance, and coronary blood flow. The sympathetic nervous system and the renin-angiotensin system are important modulators of diastolic filling, directly or indirectly. The diagnosis of heart failure is confirmed by a combination of clinical tests including invasive and noninvasive techniques, each of which has advantages and disadvantages. Treatment of medical conditions in which diastolic heart failure is a prominent component include pharmacotherapy with calcium channel antagonists, beta-adrenergic blocking agents, diuretic agents, and angiotensin-converting-enzyme inhibitors. Certain conditions associated with diastolic filling abnormalities such as pericardial disease or severe ischemic heart disease may be best managed by surgical or percutaneous intervention. Future research will include further delineation of the cellular mechanisms of active myocardial relaxation and clinical investigation into treatment directed at improving outcome.

Clinical evaluation of left heart Doppler contrast enhancement by a saccharide-based transpulmonary contrast agent. The Levovist Cardiac Working Group

OBJECTIVES

A multicenter study was carried out to evaluate the efficacy with which SHU 508A enhances left heart Doppler signals and improves the clinical quantification of valve disease.

BACKGROUND

Poor signal-to-noise ratio often limits the Doppler interrogation of left heart flows. This problem may be resolved by the enhancement of Doppler signals by an ultrasound contrast agent capable of pulmonary transmission, such as the recently developed SHU 508A.

METHODS

Left heart contrast enhancement was tested for 1) continuous wave Doppler evaluation in 51 patients with aortic stenosis, 2) pulsed Doppler transthoracic evaluation of pulmonary venous flow in 85 patients, and 3) color Doppler evaluation of mitral regurgitation in 60 patients. Studies were performed immediately before and during the intravenous administration of SHU 508A (16 ml of 200 mg/ml) and compared with unenhanced transesophageal data in representative subsets of patients.

RESULTS

SHU 508A had no serious adverse effects. A significant increase in left heart Doppler signal intensity lasted for 30 to 300 s. The continuous wave Doppler velocity envelope was enhanced for all jets, but Doppler peak velocity was not altered in high quality baseline studies. However, Doppler contrast enhancement resulted in higher measured peak gradients (p < 0.001) in 29 patients with aortic stenosis who had poor quality baseline studies. This improved the overall correlation with invasive pressure measurements (r = 0.73 vs. r = 0.89, p < 0.01). The enhanced pulsed Doppler traces of transthoracic pulmonary venous flow allowed quantitative analysis in 92% patients (vs. 27% at baseline) and correlated well with peak velocities and velocity profiles obtained by transesophageal echocardiography (r = 0.91, p < 0.001). The enhanced color Doppler display of regurgitant jets increased jet area with a high interindividual variability (mean 276%), resulting in almost identical jet areas as unenhanced transesophageal values (r = 0.97, p < 0.001).

CONCLUSIONS

SHU 508A is a safe transpulmonary contrast agent that significantly enhances both spectral and color Doppler signals in the left heart. In specific patient subsets, the increase in signal-to-noise ratio improved the quantitative assessment of aortic stenosis, pulmonary venous flow and mitral regurgitation.

Doppler reconstruction of left ventricular pressure from functional mitral regurgitation: potential importance of varying orifice geometry

OBJECTIVE

To assess the left ventricular pressure pulse, in particular its time course, reconstructed from the continuous wave Doppler signal of functional mitral regurgitation using the simplified Bernoulli equation.

DESIGN

Prospective study with simultaneously recorded high fidelity left ventricular pressure and continuous wave Doppler traces of functional mitral regurgitation, along with indirect left atrial pressure, electrocardiograms, and phonocardiograms.

SETTING

Tertiary referral cardiac centre.

PATIENTS

9 patients (age 60 (17) years) were studied immediately before or 1-20 h after routine cardiac surgery.

RESULTS

104 cardiac cycles were analysed. There were no consistent differences between directly measured and reconstructed pressures in the time intervals from Q to + dP/dt (mean (SD) 125 (35) v 130 (35) ms and from Q to -dP/dt (389 (30) v 387 (28) ms or from Q to maximum pressure (267 (40) v 270 (40) ms, all P = NS). The time from Q to the onset of pressure rise (67 (30) v 64 (30) ms, P < 0.01) and the duration of total left ventricular systole (404 (50) v 408 (50) ms, P < 0.01) measured by the two methods were effectively identical, though the small difference was consistent enough to be statistically significant. The calculated peak pressure drop between the left ventricle and the left atrium (45-100 mm Hg) significantly underestimated left ventricular pressure (72-150 mm Hg; 70 (11) v 105 (15) mm Hg, P < 0.01) even if mean left atrial pressure (14 (4.0) mm Hg) was taken into account. Compared with those directly derived from left ventricular pressure, values of pressure measured at + dP/dt (26 (6.5) v 53 (10) mm Hg, P < 0.01) and -dP/dt (30 (8.0) v 60 (10) mm Hg, P < 0.01), and those of the rates of increase (675 (155) v 815 (155) mm Hg/s, P < 0.01) and fall (610 (145) v 845 (175) mm Hg, P < 0.01) were all significantly underestimated by Doppler. The underestimation in peak rates of pressure change could not entirely be explained by a scaling effect of absolute pressure. To investigate interrelations between the two methods throughout the cardiac cycle, reconstructed left ventricular pressure was plotted against the direct record. The plots confirmed that the reconstructed pressure was always less than directly measured pressure, the relative degree of underestimation falling as the pressure rose. This was not the effect of acceleration but probably reflects changing geometry of the regurgitant orifice.

CONCLUSION

The continuous wave Doppler trace of functional mitral regurgitation is suitable for studying the timing of overall mechanical events and normalised rates of change of pressure in the left ventricle. Estimates of atrioventricular pressure drop by this method and particularly its absolute rates of change seem to be less reliable.

Noninvasive evaluation of contractile state by left ventricular dP/dtmax divided by end-diastolic volume using continuous-wave Doppler and M-mode echocardiography

The maximum rate of left ventricular (LV) pressure rise (dP/dtmax) is commonly used in the assessment of directional change in LV contractility and, recently, estimated by analyzing continuous-wave Doppler ultrasound velocity curve of mitral regurgitation. As an alteration in ventricular preload is known to affect dP/dtmax, normalized dP/dtmax for preload might be more reliable to assess LV contractile state. To investigate the usefulness of a new index of LV contractile state determined by continuous-wave Doppler analysis of mitral regurgitation and M-mode echocardiogram-derived LV end-diastolic volume, we studied 18 patients with mild mitral regurgitation. The continuous-wave Doppler velocity curves of mitral regurgitation were digitized and converted to instantaneous pressure gradient between the LV and left atrium using the simplified Bernoulli equation. The maximum value of its first derivative (Doppler-derived dP/dtmax) correlated well with LV dP/dtmax using simultaneously recorded LV pressures by manometer-tipped catheter (n = 20, r = 0.97, p < 0.001). Corrected Doppler-derived dP/dtmax for LV end-diastolic volume using Teichholz's method significantly increased by inotropic stimulation with dobutamine (p < 0.01); however, it remained unchanged by augmentation of afterload with angiotensin II. Thus, the LV dP/dtmax can be accurately estimated in humans by analyzing the continuous-wave Doppler velocity curve of mitral regurgitation, and corrected Doppler-derived dP/dtmax for LV end-diastolic volume is relatively independent of loading alteration and sensitive to inotropic stimulation. We concluded that echocardiographic assessment by combined Doppler- and M-mode measurements provides a useful and sensitive index of LV contractile state noninvasively.

Comparison of Doppler derived haemodynamic variables and simultaneous high fidelity pressure measurements in severe pulmonary hypertension

OBJECTIVE

To assess relations between right ventricular pressure measured with a high fidelity transducer tipped catheter and the characteristics of tricuspid regurgitation recorded with Doppler echocardiography.

DESIGN

A prospective non-randomised study of patients with severe pulmonary hypertension referred for consideration of lung transplantation.

SETTING

A tertiary referral centre for cardiac and pulmonary disease, with facilities for invasive and non-invasive investigation, and assessment for heart and heart-lung transplantation.

PATIENTS

10 patients with severe pulmonary hypertension being considered for lung transplantation.

ENDPOINTS

Peak right ventricular, pulmonary artery, and right atrial pressures; peak positive and negative right ventricular dP/dt; peak Doppler right ventricular-right atrial pressure drop; Doppler derived peak positive and negative right ventricular dP/dt; and time intervals of Q to peak right ventricular pressure and to peak positive and negative right ventricular dP/dt.

RESULTS

The mean (SD) pulmonary artery systolic pressure was 109 (29) mm Hg. The peak Doppler right ventricular-right atrial pressure drop underestimated peak right ventricular pressure by 38 (21) mm Hg, and by 21 (18) mm Hg when the Doppler value was added to the measured right atrial pressure (P values < 0.05). This discrepancy was greater for higher pulmonary artery pressures. The timing of peak right ventricular pressure differed, with the Doppler value consistently shorter (mean difference 16 ms, P < 0.05). Values of peak positive and negative right ventricular dP/dt and the time intervals Q-peak positive right ventricular dP/dt and pulmonary closure to the end of the pressure pulse differed between the two techniques in individual patients, but not in a consistent or predictable way.

CONCLUSIONS

Doppler echocardiography significantly underestimates the peak right ventricular pressure and the time interval to peak right ventricular pressure in pulmonary hypertension, particularly when severe. These differences may be related to orifice geometry. Digitisation of Doppler records of tricuspid regurgitation provides useful semiquantitative estimates of absolute values and timing of peak positive and negative right ventricular dP/dt. Clinically significant differences may exist, however, and must be considered in individual patients.

Nature of ventricular activation in patients with dilated cardiomyopathy: evidence for bilateral bundle branch block

OBJECTIVE

To investigate the nature of ventricular activation and its relation with mechanical events in patients with dilated cardiomyopathy.

STUDY DESIGN

Retrospective and prospective study with 12 lead electrocardiograms, signal averaged electrocardiograms, and M mode and Doppler echocardiograms.

SETTING

Tertiary cardiac referral centre.

PATIENTS

77 patients (mean (SD) age 59(13)) with dilated cardiomyopathy, four after aortic valve replacement and three after coronary bypass surgery, and six patients with a normal sized left ventricle and complete right bundle branch block were studied. 15 normal subjects (age 45(20)) were used as controls.

RESULTS

In patients with dilated cardiomyopathy, QRS duration was longer (127(25) ms v 90(10), P < 0.05) than normal and was normally distributed (r = 0.991, P < 0.01) on a normal probability plot. 20 had classic left bundle branch block, 29 intraventricular conduction delay, four right bundle branch block, and one bifascicular block. The PR interval was prolonged (185(30) ms v 150(15), P < 0.05). Electromechanical delay, Q to the onset of thickening of the interventricular septum as seen on the transverse M mode echocardiogram, was 75(15) ms in controls, but reduced to 43(15) ms in the patients (P < 0.01). Q to the onset of mitral regurgitation was also short (50(15)) ms, and correlated inversely with PR interval (r = -0.67, n = 73, P < 0.01). Early potentials (< 40 microV) were recorded on the signal averaged electrocardiogram in 33 representative patients and in all controls. Their overall duration was 30(12) ms in the patients, much longer than normal (12(7), P < 0.01)). Early potential time correlated positively with PR interval (r = 0.75, P < 0.01) and QRS duration (r = 0.60, P < 0.01) on a 12 lead electrocardiogram, and negatively with apparent electromechanical delay (r = -0.71, P < 0.01, n = 33), but not with true electromechanical delay (73(15)ms) or true PR interval (163(30)ms), calculated by correcting apparent values for early potential. The onset of left ventricular free wall motion was delayed with respect to the septum beyond 95% of the upper normal limit in all the patients with classic left bundle branch block and intraventricular conduction defect. Motion in the right ventricular free wall was delayed in 13 of 20 patients with left bundle branch block and 24 of 29 with intraventricular conduction defect by 65(20) ms, similar to that (75(10) ms) in patients with right bundle branch block.

CONCLUSION

In most patients with dilated cardiomyopathy and an electrocardiographic pattern of left bundle branch block or intraventricular block, the onset of mechanical systole is strikingly and symmetrically delayed in both ventricles, compatible with bilateral bundle branch block. Complete atrioventricular block does not occur. The ventricle is activated through the upper septum and this activation is detectable only by signal averaged electrocardiography. The anatomical substrates for this abnormal activation could be the high connections described by Mahaim and Winston.

Noninvasive estimation of left ventricular Max(dP/dt) from aortic flow acceleration and pulse wave velocity

The Doppler method of obtaining left ventricular Max(dP/dt) proposed recently was based on the measurement of mitral regurgitation velocity. Since Max(dP/dt) is an isovolumic phase index, its use in cases of mitral regurgitation may be open to argument. However, we had proposed a noninvasive method of estimating left ventricular Max(dP/dt) based on different principles. In our method, Max(dP/dt) had been given by Max(dP/dt) = (rho)cMax (du/dt), where rho is the blood density, c is the pulse wave velocity, and u is the flow velocity in the aorta. We had derived the above equation theoretically, and confirmed its validity by animal experiments. In our previous study, we also applied our method in the clinical setting. The aortic flow velocity was measured by Doppler echocardiography, and the pulse wave velocity by mechanocardiography or Doppler echocardiography. (Rho)cMax(du/dt) obtained noninvasively was compared with Max(dP/dt) measured with a catheter-tip micromanometer. We found an excellent correlation between (rho)cMax(du/dt) and Max(dp/dt), and concluded that (rho)Max(du/dt) is useful in assessing noninvasively the contractile state of the left ventricle. Here, we summarize our method, review previous results, and report new results of the clinical application of our method.

Validation of continuous wave Doppler-determined right ventricular peak positive and negative dP/dt: effect of right atrial pressure on measurement

OBJECTIVES

The present study aimed to validate the peak positive and negative values of the first derivative of right ventricular pressure (dP/dt) using Doppler echocardiography and to determine the impact of right atrial pressure on the measurements.

BACKGROUND

A pressure gradient between the right ventricle and the right atrium can be obtained by continuous wave Doppler-derived tricuspid regurgitant velocity using the simplified Bernoulli equation. If right atrial pressure fluctuation during systole and isovolumic diastole were small compared with right ventricular pressure changes, right ventricular pressure could be evaluated, and maximal positive and negative dP/dt could also be determined with Doppler echocardiography.

METHODS

We investigated 11 patients with a wide range of right atrial pressure with tricuspid regurgitation using simultaneous examination by Doppler ultrasound and catheterization. Hemodynamic conditions were altered by the Valsalva maneuver, and a total of 40 beats were analyzed.

RESULTS

There was good correlation between Doppler-derived and catheterization-derived peak positive dP/dt (y = 1.0x - 15.4, r = 0.98, n = 40), irrespective of the level of right atrial pressure. Doppler-derived peak negative dP/dt also showed good correlation with that determined by catheterization (y = 0.9x + 58.2, r = 0.93, n = 40). However, in patients with high right atrial pressure (v wave pressure > or = 10 mm Hg), Doppler-derived peak negative dP/dt tended to show lower values than those from catheterization measurements, except in patients with pulmonary hypertension.

CONCLUSIONS

We conclude that right ventricular dP/dt can be estimated by the Doppler method accurately and noninvasively. However, when right atrial pressure is relatively high compared with corresponding right ventricular pressure changes during isovolumic diastole, Doppler-derived peak negative dP/dt might underestimate catheter-derived measurements.

Quantitative evaluation of left ventricular systolic function by Doppler echocardiographic techniques

Doppler echocardiography provides the ability to measure blood flow velocities noinvasively. These blood flow velocities can be used to obtain powerful hemodynamic information about systolic contractility of the left ventricle, which in the past could only be determined from invasive cardiac catheterization or cumbersome pulse recordings. Volumetric flow rates can be measured using the hydraulic principle of flow through a rigid tube, providing a measurement of stroke volume and cardiac output. The rate of the left ventricular pressure rise derived from a mitral regurgitation velocity curve provides a nonejection phase index of systolic contractility. Acceleration time can be obtained from an ascending aortic velocity and is an indicator of maximum myocardial force. Systolic time intervals can now be quickly and accurately obtained from the standard Doppler tracings. These quantitative measurements of the status of the left ventricular are accurate, reproducible, and should be incorporated into the routine noninvasive assessment of patients with cardiac disease.

Quantification of cardiac jets: theory and limitations

Jet flows are consequences of many cardiac lesions. With the advent of color Doppler flow mapping, these jet flows can be visualized noninvasively. Currently, an intense effort is underway to quantify cardiac jet flows as a means to assess the severity of jet forming lesions. Two techniques, PISA and jet centerline decay, have been suggested as methods to quantify jet flow volume. Although both techniques are theoretically sound, both formulations are based on ideal flow conditions that may not be completely realized in cardiac chambers. Thus, the complex dynamics of cardiac jet flows must be considered as they may diminish the accuracy of flow rate calculations. However, realistic in vitro experiments that mimic the impact of cardiac flow conditions on converging flows and jets, combined with carefully controlled in vivo testing of both PISA and centerline techniques, may eventually produce clinically useful quantification formulations.

Noninvasive assessment of cardiac contractility by using (dP/dt)/P of carotid artery pulses during exercise

In earlier studies we have shown that both the pressure (P) of the carotid artery pulse (CAP) and its first derivative (CAP dP/dt) could be recorded during moderate exercise. To establish that the CAP (dP/dt)/P is a noninvasive substitute for the left ventricular (LV) value, LV (dP/dt)/P, an index of cardiac contractility, we studied CAP (dP/dt)/P under various states of activity in the autonomic nervous system in 12 healthy male subjects. Increased sympathetic nerve activities yielded by passive tilting, emotional load, or cold stress increased CAP (dP/dt)/P significantly (P < 0.05). Increased parasympathetic nerve activity by ocular compression, however, did not significantly affect the value. Moderate exercise at a heart rate of approximately 150 beats.min-1 increased it significantly from 16.7 to 25.2.s-1 in a supine position (P < 0.001) and from 16.6 to 24.8.s-1 in an upright position (P < 0.001). It increased monotonically as heart rate increased, but the slope was steeper when the heart rate was greater than approximately 100 beats.min-1 than it was when the rate was less than 100 beats.min-1. In conclusion, the present study indicated that CAP (dP/dt)/P can be used as a noninvasive index of cardiac contractility even in moderate exercise.

Continuous wave Doppler echocardiography for noninvasive assessment of left ventricular dP/dt and relaxation time constant from mitral regurgitant spectra in patients

OBJECTIVES

We previously demonstrated experimentally that the mitral regurgitant velocity spectrum can be used to estimate left ventricular pressure throughout systole and may provide a new noninvasive method for estimating maximal dP/dt and the relaxation time constant. This study was designed to test this method in patients.

BACKGROUND

The maximal first derivative of left ventricular pressure (dP/dt) and the time constant of left ventricular isovolumetric relaxation (tau) are important variables of left ventricular function, but the need for invasive measurement with high fidelity catheters has limited their use in clinical cardiology.

METHODS

Twelve patients with mitral regurgitation were studied. The Doppler mitral regurgitant velocity spectrum was recorded simultaneously with micromanometer left ventricular pressure tracings in all patients. The regurgitant velocity profiles were digitized and converted to ventriculoatrial (VA) pressure gradient curves using the simplified Bernoulli equation and differentiated into instantaneous dP/dt. The relaxation time constant (tau) was calculated assuming a zero pressure asymptote from catheter left ventricular pressure decay (tau c) and from the Doppler-derived VA gradient curve with corrections. Two methods were used to correct the Doppler gradient curve to better approximate the left ventricular pressure decay before calculating the relaxation time constant: 1) adding an arbitrary 10 mm Hg (tau 10), and 2) adding the actual mean pulmonary capillary pressure (tau LA).

RESULTS

The Doppler-derived maximal positive dP/dt (1,394 +/- 302 mm Hg/s [mean +/- SD]) correlated well (r = 0.91) with the catheter-derived maximal dP/dt (1,449 +/- 307 mm Hg/s). Although the Doppler-derived negative maximal dP/dt differed slightly from catheter measurement (1,014 +/- 289 vs. 1,195 +/- 354 mm Hg/s, p < 0.01), the correlation between Doppler and catheter measurements was similarly good (r = 0.89, p < 0.0001). The correlation between tau 10 and tau c was excellent (r = 0.93, p < 0.01), but the Doppler-derived tau 10 (50.0 +/- 11.0 ms) slightly underestimated the catheter-derived tau c (55.5 +/- 12.8 ms, p < 0.01). This slight underestimation could be corrected by adding the actual pulmonary capillary wedge pressure to the Doppler gradient curve.

CONCLUSIONS

Doppler echocardiography provides an accurate and reliable method for estimating left ventricular maximal positive dP/dt, maximal negative dP/dt and the relaxation time constant (tau) in patients with mitral regurgitation.

Quantitative hemodynamics by Doppler echocardiography: a noninvasive alternative to cardiac catheterization

Doppler echocardiography has greatly enhanced the information provided by two-dimensional echocardiography. By providing information concerning pressure gradients, intracardiac pressures, volumetric flow, and diastolic filling of the heart, most hemodynamic information that in the past could be obtained only from cardiac catheterization can now be provided accurately and noninvasively by Doppler echocardiography. Future developments in instrument technology and understanding of the various Doppler velocity curves should further aid in the ability to obtain a complete, noninvasive hemodynamic assessment of the patient with cardiac disease.

A simultaneous study of Doppler-echo and catheterization in noninvasive assessment of the left ventricular dp/dt

To confirm the feasibility and accuracy of the method for the noninvasive measurement of the left ventricular dp/dt, 53 patients with mitral regurgitation underwent simultaneous determination of left ventricular dp/dt by continuous-wave Doppler echocardiography and cardiac catheterization. Doppler-determined left ventricular dp/dt is derived from the Doppler mitral regurgitant spectrum by dividing the magnitude of the left ventricular-atrial pressure gradient rise between 1 and 3 m/s of the mitral regurgitant velocity signal by the time taken for this change. Left ventricular dp/dt by Doppler ranged from 629 to 3494 mmHg/s (mean +/- SD, 1971 +/- 785 mmHg/s), and that by catheterization varied between 716 and 3650 mmHg/s (mean +/- SD, 1974 +/- 727 mmHg/s). There was a high correlation (r = 0.93, y = 0.862x + 274.77, SEE = 271 mmHg/s, p < 0.001) of left ventricular dp/dt between the two techniques. It is concluded that left ventricular dp/dt is one of the most commonly used parameters for the evaluation of left ventricular systolic function and that Doppler echocardiography provides a new, accurate and noninvasive method of evaluation.

Differing effects of right ventricular pacing and left bundle branch block on left ventricular function

OBJECTIVE

To compare the different effects of right ventricular pacing and classic left bundle branch block on left ventricular function.

DESIGN

Retrospective and prospective study of 48 patients by electrocardiography, and M mode, cross sectional, and Doppler echocardiography.

SETTING

A tertiary cardiac referral centre.

PATIENTS

48 patients (age range 21 to 89 years, 15 women), 24 with a VVI pacemaker implanted and 24 with classic left bundle branch block. Functional mitral regurgitation was present in all those with right ventricular pacing and 22 of those with left bundle branch block.

RESULTS

Age, RR interval, and left ventricular size were similar in the two groups, as were conventional measurements of overall systolic function: shortening fraction and pre-ejection and aortic ejection times. In right ventricular pacing, however, QRS duration (p < 0.01) and electromechanical delay were much longer (p < 0.001), whereas the time intervals from onset of mitral regurgitation to aortic opening (contraction time) and from A 2 to the end of mitral regurgitation (relaxation time) were consistently shorter (p < 0.01) than corresponding values in patients with left bundle branch block. Reversed splitting of the second heart sound was much commoner in left bundle branch block (p < 0.02), and only these patients showed an early systolic ventricular septal contraction. Its onset followed the initial deflection of the QRS complex by 40(15) ms and preceded mitral regurgitation by a small but consistent interval of 10 ms (p < 0.01). The onset of posterior wall thickening was synchronous with the onset of mitral regurgitation in right ventricular pacing but much later (p < 0.01) in patients with left bundle branch block. The extent of incoordinate wall motion measure as relative dimension change during pre-ejection and isovolumic relaxation period was much greater (p < 0.01) in left bundle branch block. These major differences were not altered by left ventricular cavity size in either group, nor by the presence of previous left bundle branch block in patients who were subsequently paced.

CONCLUSIONS

The left ventricle seems to be activated much more rapidly with right ventricular pacing than with left bundle branch block. This applies even when left bundle branch block is present before pacing. Electromechanical delay, contraction and relaxation times, and extent of incoordinate ventricular wall motion differ strikingly between the two conditions. The use of right ventricular pacing as an experimental model of left bundle branch block in humans must be re-examined.

Effects of intravenous milrinone on left ventricular function in ischemic and idiopathic dilated cardiomyopathy

M-mode echocardiography and Doppler were used to assess the effects of phosphodiesterase inhibition on subendocardial function in dilated cardiomyopathy, and in particular, to study interactions with both systolic and diastolic left ventricular function. Twelve adult patients with dilated cardiomyopathy were studied (6 ischemic in origin and 6 idiopathic), 7 of whom were being considered for cardiac transplantation. Cardiac index increased without significant change in heart rate or blood pressure. Longitudinal mitral ring motion, which had been uniformly reduced, increased markedly after intravenous milrinone. Left ventricular cavity size decreased, and shortening fraction, posterior wall thickness, and rates of posterior wall thickening and thinning increased markedly. Left atrial pressure decreased, and isovolumic relaxation time increased. However, the peak velocity and duration of the transmitral E wave increased, with no change in the A wave. Improved longitudinal (subendocardial) function was reflected by improved posterior wall dynamics, and early filling, possibly by augmentation of restoring forces. Thus, severely reduced subendocardial function in dilated cardiomyopathy is potentially reversible, with marked effects on systolic and diastolic function. These previously unrecognized actions of milrinone provide further evidence to justify its short-term use in supporting the severely depressed myocardium.

Effects of abnormal activation on the time course of the left ventricular pressure pulse in dilated cardiomyopathy

OBJECTIVE

To investigate the effects of QRS duration on characteristics of the left ventricular pressure pulse derived from the time course of functional mitral regurgitation by continuous wave Doppler.

DESIGN

Retrospective and prospective study of 50 patients with dilated cardiomyopathy, by electrocardiography, echocardiography, and Doppler cardiography.

SETTING

Tertiary cardiac referral centre.

PATIENTS

50 patients (mean age (SD) 58 (16)) with dilated cardiomyopathy, all with functional mitral regurgitation.

RESULTS

The values of QRS duration ranged widely, from 70 to 190 ms with a mean value of 110 ms, and were unimodally distributed. The overall duration of mitral regurgitation correlated positively with QRS time (r = 0.65) over the entire range of values. When the duration of mitral regurgitation was divided into contraction, aortic ejection, and relaxation times, increased QRS duration prolonged contraction (r = 0.51) and relaxation (r = 0.52) times. Aortic ejection time was affected by RR interval (r = 0.74). Duration of QRS correlated negatively with peak rate of rise in left ventricular pressure (+dP/dt) (r = -0.48), and positively with the time intervals from Q to peak pressure (r = 0.49) and to peak +dP/dt (r = 0.72), and also with those from the start of mitral regurgitation to peak pressure (r = 0.49) and to peak +dP/dt (r = 0.76). Duration of QRS did not directly affect the peak rate of left ventricular pressure fall (-dP/dt), or the isovolumic relaxation period.

CONCLUSIONS

Values of QRS duration are unimodally distributed in patients with dilated cardiomyopathy, without evidence of a discrete group of patients with left bundle branch block. Prolonged QRS duration reduces peak +dP/dt, prolongs overall duration of the pressure pulse, the time to peak +dP/dt, and relaxation time. Duration of QRS must therefore be taken into account in assessing standard measurements of myocardial function in patients with dilated cardiomyopathy.