Pieter M. Vandervoort

AN INDEX OF EARLY LEFT VENTRICULAR FILLING THAT COMBINED WITH PULSED DOPPLER PEAK E VELOCITY MAY ESTIMATE CAPILLARY WEDGE PRESSURE

OBJECTIVES This study sought to determine the applicability of the combined information obtained from transmitral Doppler flow and color M-mode Doppler flow propagation velocities for estimating pulmonary capillary wedge pressure. BACKGROUND Although Doppler-derived measurements of left ventricular (LV) filling have been applied to determine left atrial pressure, their accuracy has been limited by the variable effect of ventricular relaxation in these indexes. Recently, flow propagation velocity measured by color M-mode Doppler echocardiography has been suggested as an index of ventricular relaxation. METHODS We studied 45 patients admitted to the intensive care unit who underwent invasive hemodynamic monitoring. We measured peak early (E) and late (A) transmitral Doppler velocities, E/A ratio and flow propagation velocity (vp) and compared them by linear regression with pulmonary capillary wedge pressure (pw). RESULTS We found a modest positive correlation between pw and E (r = 0.62, p < 0.001) and the E/A ratio (r = 0.52, p < 0.001) and a negative correlation between pw and vp (r = -0.34, p = 0.02). By stepwise linear regression, only E and vp were statistically significant predictors of pw. However, the E/vp ratio provided the best estimate of pw (r = 0.80, p < 0.001; pw = 5.27 x [E/vp] + 4.6, SEE 3.1 mm Hg). CONCLUSIONS The ratio of component velocity (E) over the color M-mode propagation velocity during early LV filling, by correcting for the effect of LV relaxation, provides a better estimate of pw than standard measurements of transmitral Doppler flow.

Application of color Doppler flow mapping to calculate effective regurgitant orifice area. An in vitro study and initial clinical observations.

BACKGROUND Analogous to stenotic valve area in the assessment of valvular stenosis, regurgitant orifice area (ROA) represents a fundamental parameter to assess valvular insufficiency. However, this parameter has not been routinely available up to now. In this study, we introduce the concept and provide the methodology to calculate regurgitant orifice area noninvasively, based on the analysis of the proximal flow convergence zone. METHODS AND RESULTS In an in vitro study, we showed the feasibility and the accuracy of calculating effective ROA by the proximal flow convergence method throughout a range of driving pressures. The calculated and true ROA showed an excellent correlation with r = .992, delta ROA = -1.4 +/- 2.9 mm2. We then applied this concept clinically in 77 patients with mitral regurgitation and showed a very good correlation between effective ROA calculated by the proximal flow convergence method and calculated by the Doppler echocardiographic method: r = .95, delta ROA = -0.2 +/- 3.9 mm2. The ROA also correlated very well with Doppler echocardiographic-derived regurgitant stroke volume (r = .93) and regurgitant fraction (r = .82). In a subgroup of 20 patients who underwent invasive evaluation, the calculated effective ROA also correlated well with the angiographic grade of mitral regurgitation (rho = .81). CONCLUSIONS We conclude that effective ROA represents unique information on the severity of a regurgitant lesion and can easily be calculated by the proximal flow convergence method. This new parameter should enhance our understanding and improve the serial assessment of valvular regurgitation.

Valsartan Benefits Left Ventricular Structure and Function in Heart Failure: Val-HeFT Echocardiographic Study

OBJECTIVES The objective of the study was to evaluate the effect of an angiotensin receptor blocker on left ventricular (LV) structure and function when added to prescribed heart failure therapy. BACKGROUND The clinical benefit derived from heart failure therapy is attributed to the regression of LV remodeling. METHODS At 302 multinational sites, 5,010 patients in New York Heart Association (NYHA) classification II to IV heart failure taking angiotensin-converting enzyme inhibitor (ACEI) and/or beta-blocker (BB) were randomized into valsartan and placebo groups and followed for a mean of 22.4 months. Serial echocardiographic measurements of left ventricular internal diastolic diameter (LVIDd) and ejection fraction (EF) were recorded. Total study reproducibility calculated to 90% power at 5% significance defined detectable differences of 0.09 cm for LVIDd and 0.86% for EF. RESULTS Baseline LVIDd and EF for valsartan and placebo groups were similar: 3.6 +/- 0.5 versus 3.7 +/- 0.5 (cm/m(2)) and 26.6 +/- 7.3 versus 26.9 +/- 7.0 (%). Mean group changes from baseline over time were compared. Significant decrease in LVIDd and increase in EF began by four months, reached plateau by one year, and persisted to two years in valsartan compared with placebo patients, irrespective of age, gender, race, etiology, NYHA classification, and co-treatment therapy. Changes at 18 months were -0.12 +/- 0.4 versus -0.05 +/- 0.4 (cm/m(2)), p < 0.00001 for LVIDd, and +4.5 +/- 8.9 versus +3.2 +/- 8.6 (%), p < 0.00001 for EF. The exception occurred in patients taking both ACEI and BB as co-treatment, in whom the decrease in LVIDd and increase in EF were no different between valsartan and placebo groups. CONCLUSIONS The Val-HeFT echocardiographic substudy of 5,010 patients with moderate heart failure demonstrated that valsartan therapy taken with either ACEI or BB reversed LV remodeling.

Proximal Jet Size by Doppler Color Flow Mapping Predicts Severityof Mitral Regurgitation: Clinical Studies

Background Recent studies have shown that many instrument and physiological factors limit the ability of color Doppler total jet area within the receiving chamber to predict the severity of valvular regurgitation. In contrast, the proximal or initial dimensions of the jet as it emerges from the orifice have been shown to increase directly with orifice size and to correlate well with the severity of aortic insufficiency. Only limited data, however, are available regarding the value of proximal jet size in mitral regurgitation, and it has not been examined in short-axis or transthoracic views. The purpose of the present study, therefore, was to evaluate the relation between proximal jet size and other measures of the severity of mitral regurgitation. Methods and Results In 49 patients, the anteroposterior height of the proximal jet as it emerges from the mitral valve was measured in the parasternal long-axis view; proximal jet width and area were measured in the short-axis view at the same level. Results we...

Quantification of Mitral Regurgitation by the Proximal Convergence Method Using Transesophageal Echocardiography Clinical Validation of a Geometric Correction for Proximal Flow Constraint

BACKGROUND Proximal flow convergence is a promising method to quantify mitral regurgitation but may overestimate flow when the flow field is constrained. This has not been investigated clinically, nor has a correction factor been validated. METHODS AND RESULTS Eighty-five patients were studied intraoperatively with transesophageal echocardiography and divided into two groups: central convergence (no constraining wall) and eccentric convergence (at least one constraining wall). Regurgitant stroke volume (RSV) and orifice area (ROA) were calculated by ROA = 2 pi r2 Va/Vp and RSV = ROA x VTIcw, where r and va are the radius and velocity of the aliasing contour and vp and VTIcw are the peak and integral of regurgitant velocity. In eccentric convergence patients, convergence angle (alpha) was measured from two-dimensional Doppler color flow maps, and ROA and RSV were corrected by multiplying by alpha/180. For reference, RSV was the difference between thermodilution and pulsed Doppler stroke volumes. In central convergence patients (n = 45), RSV (r = .95, delta = 2.5 +/- 10.8 mL) and ROA (r = .96, delta = 0.02 +/- 0.08 cm2) were accurately calculated, but significant overestimation was noted in the eccentric convergence patients (n = 40, delta RSV = 63.9 +/- 38.0 mL, delta ROA = 0.54 +/- 0.31 cm2), 68% of whom had leaflet prolapse or flail. delta RSV was correlated with alpha (r = -.69, P < .001). After correction by alpha/180, overestimation was largely eliminated (delta RSV = 15.5 +/- 19.3 mL and delta ROA = 0.14 +/- 0.14 cm2) with excellent correlation for the whole group (RSV, r = .91; ROA, r = .95). CONCLUSIONS A simple geometric correction factor largely eliminates overestimation caused by flow constraint with the proximal convergence method and should extend the clinical utility of this technique.

Quantification of mitral regurgitation with the proximal flow convergence method: A clinical study

Accurate quantitation of valvular incompetence remains an important goal in clinical cardiology. It has been shown previously that when color flow Doppler mapping is used, simple measurements of apparent jet size do not correlate closely with regurgitant flow rate and regurgitant fraction. Recently the proximal flow convergence method has been proposed to quantify valvular regurgitation by analysis of the converging flow field proximal to a regurgitant lesion. Flow rate Q can be calculated as Q = 2 pi r2v(a), where v(a) is the aliasing velocity at a distance r from the orifice. In 54 patients (43 with sinus rhythm and 11 with atrial fibrillation) who had at least mild mitral regurgitation according to semiquantitative assessment, regurgitant stroke volume, regurgitant flow rate, and regurgitant fraction were calculated with the proximal flow convergence method and compared with values that were obtained by the Doppler two-dimensional echocardiographic method. Regurgitant stroke volumes (Vr) as calculated by the proximal flow convergence method correlated very closely with values that were obtained by the Doppler two-dimensional method, with r = 0.93 (y = 0.95x + 0.55) and delta Vr = -0.3 +/- 4.0 cm3. Regurgitant flow rates (Q) as calculated by both methods showed a similar correlation: r = 0.93 (y = 0.95x + 54) and delta Q = -34 +/- 284 cm3/min. The correlation for regurgitant fraction (RF) as calculated by both techniques showed r = 0.89 (y = 0.98x + 0.006) and delta RF = -0.005 +/- 0.06. All correlations were slightly better for the group of patients with sinus rhythm than for the study group of patients with atrial fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Pressure Recovery in Bileaflet Heart Valve Prostheses: Localized High Velocities and Gradients in Central and Side Orifices With Implications for Doppler-Catheter Gradient Relation in Aortic and Mitral Position

BACKGROUND We investigate pressure recovery in central and side orifices of St Jude valves and the effect of mitral versus aortic position on the relation between Doppler- and catheter-derived pressure gradients. METHODS AND RESULTS Maximum, transvalvular, and net pressure gradients are calculated and compared with Doppler-derived gradients in an in vitro model. Pressure recovery and pressure loss coefficients are calculated. Simultaneous Doppler and catheter gradients are obtained intraoperatively in five patients undergoing mitral valve replacement. Centerline Doppler gradients correspond closely with maximum catheter gradients but are higher than transvalvular and net pressure gradients. Thirty-six percent of the initial pressure drop is recovered between the valve leaflets and is independent of valve size or configuration. A variable amount of postvalvular pressure recovery is observed depending on aortic or mitral configuration. Side orifice velocities are 85 +/- 4% of the centerline velocities. Incorporation of the pressure loss coefficient in the simplified Bernoulli equation shows close agreement between centerline Doppler gradients and transvalvular gradients (r = .99, y = 1.11x-0.19). CONCLUSIONS Gradients across the St Jude valve measured by Doppler ultrasound are higher than transvalvular or net catheter gradients due to downstream pressure recovery. This is more marked for Doppler gradients based on centerline velocities than side orifice velocities and is more pronounced for valves in an aortic than a mitral configuration. Therefore, to be comparable with invasive transvalvular catheter gradients, either Doppler gradients should be calculated based on side orifice velocity measurements or the Doppler gradient calculation should include the pressure loss coefficient when based on central orifice velocities.

Automated flow rate calculation based on digital analysis of flow convergence proximal to regurgitant orifice

OBJECTIVES The purpose of the study was to develop and validate an automated method for calculating regurgitant flow rate using color Doppler echocardiography. BACKGROUND The proximal flow convergence method is a promising approach to quantitate valvular regurgitation noninvasively because it allows one to calculate regurgitant flow rate and regurgitant orifice area; however, defining the location of the regurgitant orifice is often difficult and can lead to significant error in the calculated flow rates. To overcome this problem we developed an automated algorithm to locate the orifice and calculate flow rate based on the digital Doppler velocity map. METHODS This algorithm compares the observed velocities with the anticipated relative velocities, cos psi/2 pi r2. The orifice is localized as the point with maximal correlation between predicted and observed velocity, whereas flow rate is specified as the slope of the regression line. We validated this algorithm in an in vitro model for flow through circular orifices with planar surroundings and a porcine bioprosthesis. RESULTS For flow through circular orifices, flow rates calculated on individual Doppler maps and on an average of eight velocity maps showed excellent agreement with true flow, with r = 0.977 and delta Q = -3.7 +/- 15.8 cm3/s and r = 0.991 and delta Q = -4.3 +/- 8.5 cm3/s, respectively. Calculated flow rates through the bioprosthesis correlated well but underestimated true flow, with r = 0.97, delta Q = -10.9 +/- 12.5 cm3/s, suggesting flow convergence over an angle > 2 pi. This systematic underestimation was corrected by assuming an effective convergence angle of 212 degrees. CONCLUSIONS This algorithm accurately locates the regurgitant orifice and calculates regurgitant flow rate for circular orifices with planar surroundings. Automated analysis of the proximal flow field is also applicable to more physiologic surfaces surrounding the regurgitant orifice; however, the convergence angle should be adjusted. This automated algorithm should make quantification of regurgitant flow rate and regurgitant orifice area more reproducible and readily available in clinical cardiology practice.

Mechanisms of hemolysis with mitral prosthetic regurgitation study using transesophageal echocardiography and fluid dynamic simulation

OBJECTIVES The aims of this study were to define the hydrodynamic mechanisms involved in the occurrence of hemolysis in prosthetic mitral valve regurgitation and to reproduce them in a numeric simulation model in order to estimate peak shear stress. BACKGROUND Although in vitro studies have demonstrated that shear stresses > 3,000 dynes/cm2 are associated with significant erythrocyte destruction, it is not known whether these values can occur in vivo in conditions of abnormal prosthetic regurgitant flow. METHODS We studied 27 patients undergoing reoperation for significant mitral prosthetic regurgitation, 16 with and 11 without hemolysis. We classified the origin and geometry of the regurgitant jets by using transesophageal echocardiography. By using the physical and morphologic characteristics defined, several hydrodynamic patterns were simulated numerically to determine shear rates. RESULTS Eight (50%) of the 16 patients with hemolysis had paravalvular leaks and the other 8 had a jet with central origin, in contrast to 2 (18%) and 9 (82%), respectively, of the 11 patients without hemolysis (p = 0.12, power 0.38). Patients with hemolysis had patterns of flow fragmentation (n = 2), collision (n = 11) or rapid acceleration (n = 3), whereas those without hemolysis had either free jets (n = 7) or slow deceleration (n = 4) (p < 0.001, power 0.99). Numeric simulation demonstrated peak shear rates of 6,000, 4,500, 4,500, 925 and 950 dynes/cm2 in these five models, respectively. CONCLUSIONS The distinct patterns of regurgitant flow seen in these patients with mitral prosthetic hemolysis were associated with rapid acceleration and deceleration or high peak shear rates, or both. The nature of the flow disturbance produced by the prosthetic regurgitant lesion and the resultant increase in shear stress are more important than the site of origin of the flow disturbance in producing clinical hemolysis.

Which physical factors determine tricuspid regurgitation jet area in the clinical setting

The visual assessment of jet area has become the most common method used in daily clinic practice to evaluate valvular regurgitation. Despite the high prevalence of tricuspid regurgitation, however, few studies have systematically compared TR jet areas with a quantitative standard. To evaluate this, 40 patients in sinus rhythm with tricuspid regurgitation were analyzed: 16 with centrally directed free jets and 24 with impinging wall jets. The size of the maximal planimetered color jet area (cm2) was compared with parameters derived using the pulsed Doppler 2-dimensional echocardiographic method: regurgitant fraction and the flow convergence method (peak flow rate, effective regurgitant orifice area and momentum). Mean tricuspid regurgitant fraction averaged 33 +/- 15%, peak flow rate 76 +/- 54 cm3/s, effective regurgitant orifice area 27 +/- 21 mm2 and momentum 21,717 +/- 15,014 cm4/s2. An average of 4-chamber, and long- and short-axis areas in free jets correlated well with regurgitant fraction (r = 0.81, p < 0.001), better with peak flow rate (r = 0.94, p < 0.001), effective regurgitant orifice (r = 0.92, p < 0.001) and momentum (r = 0.94, p < 0.001). The correlation was worse, but still significant, in wall jets. For the same peak flow rate, wall jets were 75% of the size of a corresponding free jet. Jet area measurement is a good semiquantitative tool to measure tricuspid regurgitation in free jets, which correlates well with regurgitant fraction and better with new parameters available from analysis of the proximal acceleration field. In patients with eccentrically directed wall jets the correlation with planimetered jet area was worse, but still significant.