Variable effects of changes in flow rate through the aortic, pulmonary and mitral valves on valve area and flow velocity: impact on quantitative Doppler flow calculations

Model for screening adult congenital heart disease surgery eligibility with echocardiography parameters

OBJECTIVES

This study aimed to screen for the eligibility of correction in cases of adult congenital heart disease (CHD). Pulmonary to systemic flow ratios (Qp/Qs) > 1.5 and pulmonary to systemic vascular resistance ratios (Rp/Rs) < 1/3, acquired by right heart catheterization (RHC), are two essential parameters. Nonetheless, performing RHC at every follow-up is impractical and even harmful. Thus, it is important to establish a model to predict Qp/Qs and Rp/Rs status before a RHC confirmation, using echocardiography parameters.

METHODS

A total of 1,785 patients with adult CHD were enrolled and randomly assigned to the derivation or validation groups. Echocardiogram parameters of the 974 patients in the derivation group were considered candidate predictors for surgery eligibility (Qp/Qs > 1.5 and Rp/Rs < 1/3). Binary logistic regression analyses were performed to identify the independent predictors and establish a scoring system. The scoring system was further examined in the validation group using a receiver operating characteristic (ROC) analysis.

RESULTS

Estimated pulmonary artery systolic pressure, velocity through the pulmonary valve, and diameters of the left and right atria were identified as independent predictors. The area under the ROC curve of the predictive value in the validation group and its pre- and post-tricuspid valve malformation subgroups were 0.87 (95% confidence interval [CI]: 0.84-0.90, p < 0.01), 0.86 (95% CI: 0.82-0.91, p < 0.01), and 0.85 (95% CI: 0.79-0.90, p < 0.01), respectively.

CONCLUSIONS

This scoring system could augment flexibility and convenience for pre-screening CHD patients' eligibility for surgery, before RHC.

Prothymosin Alpha: A Novel Contributor to Estradiol Receptor Alpha-Mediated CD8+ T-Cell Pathogenic Responses and Recognition of Type 1 Collagen in Rheumatic Heart Valve Disease

BACKGROUND

Rheumatic heart valve disease (RHVD) is a leading cause of cardiovascular death in low- and middle-income countries and affects predominantly women. The underlying mechanisms of chronic valvular damage remain unexplored and regulators of sex predisposition are unknown.

METHODS

Proteomics analysis of human heart valves (nondiseased aortic valves, nondiseased mitral valves [NDMVs], valves from patients with rheumatic aortic valve disease, and valves from patients with rheumatic mitral valve disease; n=30) followed by system biology analysis identified ProTα (prothymosin alpha) as a protein associated with RHVD. Histology, multiparameter flow cytometry, and enzyme-linked immunosorbent assay confirmed the expression of ProTα. In vitro experiments using peripheral mononuclear cells and valvular interstitial cells were performed using multiparameter flow cytometry and quantitative polymerase chain reaction. In silico analysis of the RHVD and Streptococcuspyogenes proteomes were used to identify mimic epitopes.

RESULTS

A comparison of NDMV and nondiseased aortic valve proteomes established the baseline differences between nondiseased aortic and mitral valves. Thirteen unique proteins were enriched in NDMVs. Comparison of NDMVs versus valves from patients with rheumatic mitral valve disease and nondiseased aortic valves versus valves from patients with rheumatic aortic valve disease identified 213 proteins enriched in rheumatic valves. The expression of the 13 NDMV-enriched proteins was evaluated across the 213 proteins enriched in diseased valves, resulting in the discovery of ProTα common to valves from patients with rheumatic mitral valve disease and valves from patients with rheumatic aortic valve disease. ProTα plasma levels were significantly higher in patients with RHVD than in healthy individuals. Immunoreactive ProTα colocalized with CD8⁺ T cells in RHVD. Expression of ProTα and estrogen receptor alpha correlated strongly in circulating CD8⁺ T cells from patients with RHVD. Recombinant ProTα induced expression of the lytic proteins perforin and granzyme B by CD8⁺ T cells as well as higher estrogen receptor alpha expression. In addition, recombinant ProTα increased human leukocyte antigen class I levels in valvular interstitial cells. Treatment of CD8⁺ T cells with specific estrogen receptor alpha antagonist reduced the cytotoxic potential promoted by ProTα. In silico analysis of RHVD and Spyogenes proteomes revealed molecular mimicry between human type 1 collagen epitope and bacterial collagen-like protein, which induced CD8⁺ T-cell activation in vitro.

CONCLUSIONS

ProTα-dependent CD8⁺ T-cell cytotoxicity was associated with estrogen receptor alpha activity, implicating ProTα as a potential regulator of sex predisposition in RHVD. ProTα facilitated recognition of type 1 collagen mimic epitopes by CD8⁺ T cells, suggesting mechanisms provoking autoimmunity.

Evaluation of fetal foramen ovale blood flow by pulsed Doppler ultrasonography combined with spatiotemporal image correlation : To define the normal reference range of fetal foramen ovale blood volume for each gestational age: a cross-sectional study

Objective

The objective of this study was to determine fetal foramen ovale blood flow utilizing pulsed Doppler combined with spatiotemporal image correlation.

Methods

A cross-sectional study was performed in 440 normal fetuses between 20 and 40 weeks of gestation. In order to calculate foramen ovale blood flow, the foramen ovale flow velocity–time integral was obtained by pulsed Doppler ultrasonography, and the foramen ovale area was measured by using spatiotemporal image correlation rendering mode. Foramen ovale blood flow was calculated as the product of the foramen ovale area and the velocity–time integral.

Results

Gestational age-specific reference ranges are given for the absolute blood flow (ml/min) of foramen ovale, showing an exponential increase from 20 to 30 weeks of gestation, and a flat growth trend during the last trimester, while the weight-indexed flow (ml/min/kg) of foramen ovale decreased significantly. The median weight-indexed foramen ovale blood flow was 320.82 ml/min/kg (mean 319.1 ml/min/kg; SD 106.33 ml/min/kg).

Conclusions

The reference range for fetal foramen ovale blood flow was determined from 20 to 40 weeks of gestation. The present data show that the volume of foramen ovale blood flow might have a limited capacity to increase during the last trimester.

Cardiac output measured by transthoracic echocardiography and Swan-Ganz catheter. A comparative study in mechanically ventilated patients with high positive end-expiratory pressure

Objective

To compare cardiac output measurements by transthoracic echocardiography and a pulmonary artery catheter in mechanically ventilated patients with high positive end-expiratory pressure. To evaluate the effect of tricuspid regurgitation.

Methods

Sixteen mechanically ventilated patients were studied. Cardiac output was measured by pulmonary artery catheterization and transthoracic echocardiography. Measurements were performed at different levels of positive end-expiratory pressure (10cmH₂O, 15cmH₂O, and 20cmH₂O). The effect of tricuspid regurgitation on cardiac output measurement was evaluated. The intraclass correlation coefficient was studied; the mean error and limits of agreement were studied with the Bland-Altman plot. The error rate was calculated.

Results

Forty-four pairs of cardiac output measurements were obtained. An intraclass correlation coefficient of 0.908 was found (p < 0.001). The mean error was 0.44L/min for cardiac output values between 5 and 13L/min. The limits of agreement were 3.25L/min and -2.37L/min. With tricuspid insufficiency, the intraclass correlation coefficient was 0.791, and without tricuspid insufficiency, 0.935. Tricuspid insufficiency increased the error rate from 32% to 52%.

Conclusions

In patients with high positive end-expiratory pressure, cardiac output measurement by transthoracic echocardiography is comparable to that with a pulmonary artery catheter. Tricuspid regurgitation influences the intraclass correlation coefficient. In patients with high positive end-expiratory pressure, the use of transthoracic echocardiography to measure cardiac output is comparable to invasive measures.

Right Ventricular Function After Creation of an Atriovenous Fistula in Patients With End Stage Renal Disease

BACKGROUND

Right ventricular (RV) dysfunction is associated with increased risk of heart failure and mortality in end stage renal disease (ESRD) patients. Accumulating evidence suggests an association between atriovenous fistula (AVF) and RV dysfunction; however, there is no adequate data on the relation between AVF characteristics and risk of RV dysfunction after AVF creation.

METHODS

The study included 30 ESRD patients (median age: 44years, 17 male) who had their first autogenous mature AVF. Before and 6months after AVF creation the following were measured: myocardial performance index of RV (MPI-RV) using tissue Doppler imaging echocardiography and flow rate (Qa), feeding artery and receiving vein diameters using colour-flow Doppler ultrasound. Change (Δ) in MPI-RV was calculated by subtracting follow-up value from baseline value. Worsening RV function was defined as Δ MPI-RV>0.015 and high AVF flow as Qa≥950ml/min.

RESULTS

Compared to patients with lower AVF flow, patients with higher flow showed increased Δ in MPI-RV (0.12 vs. -0.03, p=0.04), basal RV diameter (0.3 vs. -0.02cm, p=0.014), left ventricular end diastolic volume index (9.9 vs. 0ml/m², p=0.004) and left atrial volume index (3 vs. 1ml/m², p=0.016). Among all clinical, echocardiographic and AVF-related parameters, univariate predictors of worsening of RV function were: high Qa, upper arm AVF, and large feeding artery diameter at baseline. Δ MPI-RV showed significant correlations with feeding artery diameter at baseline (r=0.46, p=0.01), and Qa (0.37, p=0.04) and no significant correlation with pulmonary artery pressures. Qa≥950ml/min, feeding artery diameter at baseline≥4mm and upper arm AVF can predict worsening of RV function with 73%, 73%, 75% sensitivity and 67%, 67%, 70% specificity, respectively.

CONCLUSIONS

In patients with ESRD, higher AVF flow adversely affects RV remodelling, manifested as increased size and worsening function. Predictors of worsening of RV function are: higher AVF flow rate, AVF in the upper arm, and large feeding artery diameter.

Depressed left and right ventricular cardiac output in fetuses of diabetic mothers

INTRODUCTION

We compared right and left ventricular cardiac output (RVCO and LVCO) in fetuses of diabetic mothers (FDM) to a large normal cohort.

METHODS

We prospectively enrolled 264 normal fetuses and 30 FDM. Fetal CO parameters: semilunar valve velocity time integrals (AVVTI, PVVTI), ventricular outflow diameters (LVOTD, RVOTD), stroke volumes (AVSV, PVSV) were measured, and LVCO and RVCO calculated.  These were normalized using nonlinear regression to estimated fetal weight (EFW) to provide means and standard deviations. Among FDMs, mean Z-scores and 95% confidence limits (CL) were calculated, and compared to zero.

RESULTS

LVCO, RVCO, and parameters they were calculated from, increased predictably and non-linearly with increasing EFW.  In FDM, LVCO was depressed (mean Z -1.679, 95% CL -2.404, -0.955, p<0.001), and AVVTI, LVOTD, AVSV significantly lower than normal.  Similarly, RVCO (mean Z = -1.119, CL -1.839, -0.400, p=0.003), RVOTD (mean -2.085, CL -3.077, -1.093, p<0.001), and PVSV (mean -1.184, CL -1.921, -0.446, p=0.003) were lower than normal, however, PVVTI was not different (mean Z 0.078, CL -0.552, +0.707, p=0.803).

CONCLUSION

Normal biventricular stroke volumes and outputs follow a nonlinear regression with EFW. FDM have significantly lower right and left heart stroke volumes and outputs for weight than do normal fetuses.

Estimated combined cardiac output and laser therapy for twin-twin transfusion syndrome

INTRODUCTION

Twin-twin transfusion syndrome (TTTS) is the major cause for fetal demise in monochorionic diamniotic pregnancies. Estimated combined cardiac output (CCO) has not been studied in this setting. The primary aims of this study were to compare CCO in twin donor and recipient fetuses and assess differences in CCO before and after laser coagulation therapy. A secondary aim was to evaluate the relationship of CCO with perinatal mortality, defined as intrauterine or neonatal mortality (≤30 days of age) in fetuses that underwent laser coagulation therapy.

METHODS

We performed a retrospective review of fetuses with TTTS who received echocardiograms prior to laser therapy. Prelaser echocardiograms were performed in 66 fetuses, of which 45 (21 donor and 24 recipient) survived to the postlaser echocardiogram.

RESULTS

Donor CCO increased from a mean of 487±137 mL/min/kg prelaser to 592±128 mL/min/kg postlaser (P=.025). There was no significant change in mean recipient CCO from prelaser 551±165 mL/min/kg to postlaser 575±112 mL/min/kg (P=.564). In recipient fetuses, higher prelaser CCO correlated with increasing Quintero stage (P=.010) and perinatal mortality (P=.003). Thirty-day postnatal outcome data were available for 38 fetuses, of whom 34 (89%) survived. Amongst survivors, 25 (74%) experienced an increase in CCO, while 9 (26%) experienced a decrease in CCO (P=.010). Donor fetuses had higher CCO after laser therapy.

CONCLUSIONS

Higher prelaser CCO in recipient fetuses may indicate more advanced disease. Fetuses who exhibit a decrease in CCO after therapy laser may be at higher risk for perinatal mortality.

Assessment of Right Ventricular Afterload in COPD

BACKGROUND

We aimed to study whether pulmonary hypertension (PH) and elevated pulmonary vascular resistance (PVR) could be predicted by conventional echo Doppler and novel tissue Doppler imaging (TDI) in a population of chronic obstructive pulmonary disease (COPD) free of LV disease and co-morbidities.

METHODS

Echocardiography and right heart catheterization was performed in 100 outpatients with COPD. By echocardiography the time-integral of the TDI index, right ventricular systolic velocity (RVSmVTI) and pulmonary acceleration-time (PAAcT) were measured and adjusted for heart rate. The COPD patients were randomly divided in a derivation (n = 50) and a validation cohort (n = 50).

RESULTS

PH (mean pulmonary artery pressure (mPAP) ≥ 25mmHg) and elevated PVR ≥ 2Wood unit (WU) were predicted by satisfactory area under the curve for RVSmVTI of 0.93 and 0.93 and for PAAcT of 0.96 and 0.96, respectively. Both echo indices were 100% feasible, contrasting 84% feasibility for parameters relying on contrast enhanced tricuspid-regurgitation. RVSmVTI and PAAcT showed best correlations to invasive measured mPAP, but less so to PVR. PAAcT was accurate in 90- and 78% and RVSmVTI in 90- and 84% in the calculation of mPAP and PVR, respectively.

CONCLUSIONS

Heart rate adjusted-PAAcT and RVSmVTI are simple and reproducible methods that correlate well with pulmonary artery pressure and PVR and showed high accuracy in detecting PH and increased PVR in patients with COPD. Taken into account the high feasibility of these two echo indices, they should be considered in the echocardiographic assessment of COPD patients.

Correlation between Pulmonary Artery Pressure Measured by Echocardiography and Right Heart Catheterization in Patients with Rheumatic Mitral Valve Stenosis (A Prospective Study)

INTRODUCTION

Right heart catheterization (RHC) remains the gold standard for hemodynamic assessment of the right heart and pulmonary artery. However, this is an invasive tool, and noninvasive alternatives such as transthoracic echocardiography (TTE) are preferable. Nonetheless, the correlation between measurements by TTE and RHC are debated. In this study, we prospectively examined the correlation between systolic and mean pulmonary artery pressures (sPAP and mPAP) measured by RHC and TTE in patients with hemodynamically significant rheumatic mitral stenosis (MS).

MATERIAL AND METHODS

Three hundred patients with hemodynamically significant MS undergoing TTE who were scheduled to undergo RHC within 24 hours were analyzed. PAP measurements were taken for all patients by RHC (sPAP(RHC), mPAP(RHC)). Maximum velocity of tricuspid regurgitation (TR) jet obtained by continuous-wave Doppler with adding right atrial (RA) pressure was used for measuring sPAP by TTE (sPAP(TRVmax)). Mean PAP was measured using either pulmonary artery acceleration time (mPAP(PAAT)) method or by adding RA pressure to velocity-time integral of TR jet (mPAP(TRVTI)).

RESULTS

A good correlation between sPAP(RHC) and sPAP(TRVmax) (r = 0.89, P < 0.001), between mPAP(RHC) and mPAP(PAAT) (r = 0.9, P < 0.001), and between mPAP(RHC) and mPAP(TRVTI) (r = 0.92, P < 0.001) was found. Sensitivity and specificity of sPAP(TRV) max in detecting pulmonary hypertension (PH) were 92.8% and 86.6% and of mPAP(PAAT) were 94.1% and 73.3%, respectively.

CONCLUSION

The noninvasive assessment of sPAP and mPAP by TTE correlates well with invasive measurements and has an acceptable specificity and sensitivity in detecting PH in patients with hemodynamically significant MS.

Right and left heart dysfunction predict mortality in pulmonary hypertension

In pulmonary hypertension (PH), the right heart dysfunction is a strong predictor of adverse clinical outcome, while the role of the left heart is not fully determined. The aim of this study was to identify predictors of mortality in precapillary PH including measures of both right and left heart function. We studied 34 patients (mean age 64 ± 13, range 31-82 years, 24 females) with precapillary PH, all of whom underwent detailed Doppler echocardiographic examination of the right and left heart function using conventional and speckle-tracking echocardiography. Patients were followed up for up to 8 years (mean 4·2 ± 1·9 years). At follow-up, 16 patients survived. Left ventricular (LV) filling time (P = 0·007), pulmonary artery acceleration time (P = 0·009), right atrial pressure (RAP) (P<0·001) and tricuspid regurgitation (TR) severity (P = 0·007) were worse in the deceased group. RV global longitudinal strain (GLS) (P = 0·001), RAP (P≤0·001), LV filling time (P<0·001) and TR severity (P<0·001) were the most accurate predictors, having the largest AUC (>0·65) and carried the highest risk for mortality (P<0·001 for all). The strongest predictors of mortality in precapillary PH indirectly reflect both left and right heart dysfunction including atrial structure and function disturbances. While an interaction pattern is observed, it needs to be confirmed in a larger cohort.

Doppler flow patterns in the right ventricle-to-pulmonary artery shunt and neo-aorta in infants with single right ventricle anomalies: impact on outcome after initial staged palliations

BACKGROUND

A Pediatric Heart Network trial compared outcomes in infants with single right ventricle anomalies undergoing Norwood procedures randomized to modified Blalock-Taussig shunt (MBTS) or right ventricle-to-pulmonary artery shunt (RVPAS). Doppler patterns in the neo-aorta and RVPAS may characterize physiologic changes after staged palliations that affect outcomes and right ventricular (RV) function.

METHODS

Neo-aortic cardiac index (CI), retrograde fraction (RF) in the descending aorta and RVPAS conduit, RVPAS/neo-aortic systolic ejection time ratio, and systolic/diastolic (S/D) ratio were measured early after Norwood, before stage II palliation, and at 14 months. These parameters were compared with transplantation-free survival, length of hospital stay, and RV functional indices.

RESULTS

In 529 subjects (mean follow-up period, 3.0 ± 2.1 years), neo-aortic CI and descending aortic RF were significantly higher in the MBTS cohort after Norwood. The RVPAS RF averaged <25% at both interstage intervals. Higher pre-stage II descending aortic RF was correlated with lower RV ejection fraction (R = -0.24; P = .032) at 14 months for the MBTS cohort. Higher post-Norwood CI (5.6 vs 4.4 L/min/m(2), P = .04) and lower S/D ratio (1.40 vs 1.68, P = .01) were correlated with better interstage transplantation-free survival for the RVPAS cohort. No other Doppler flow patterns were correlated with outcomes.

CONCLUSIONS

After the Norwood procedure, infants tolerated significant descending aortic RF (MBTS) and conduit RF (RVPAS), with little correlation with clinical outcomes or RV function. Neo-aortic CI, ejection time, and S/D ratios also had limited correlations with outcomes or RV function, but higher post-Norwood neo-aortic CI and lower S/D ratio were correlated with better interstage survival in those with RVPAS.

Echocardiography based estimation of pulmonary vascular resistance in patients with pulmonary hypertension: a simultaneous Doppler echocardiography and cardiac catheterization study

AIMS

Pulmonary vascular resistance (PVR) is an important measurement for the diagnosis of patients with pulmonary hypertension (PH) but needs accurate determination of mean pulmonary artery pressure (PAMP). We aimed to test the accuracy of a Doppler-derived measurement of PVR, using the conventional invasive equation in patients with PH.

METHODS AND RESULTS

We investigated 30 patients undergoing right heart catheterization (RHC), mean age 62 ± 13 years, 21 females, with different diseases; idiopathic pulmonary arterial hypertension (PAH) (n = 5), associated PAH (n = 16), chronic thromboembolic PH (n = 6), interstitial lung disease (n = 2), and after closure of an atrial septal defect (n = 1). Patients with impaired left ventricular systolic function (EF < 50%) or elevated pulmonary capillary wedge pressure (PCWP >15 mmHg on RHC) were excluded. We used the formula: PAMP = PASP(echo) × 0.61 + 2 mmHg, where PASP(echo) is the peak tricuspid regurgitation pressure drop + 10 or 7 mmHg. Pulmonary vascular resistance was then calculated as PAMP(echo)- PCWP/cardiac output. Pulmonary capillary wedge pressure was estimated at 10 mmHg in all cases. The Doppler-derived estimation of PVR(echo) was achievable in 90% of patients, in whom accurate calculation of PAMP was obtainable. Pulmonary vascular resistance echo individual values strongly correlated with those from RHC (r = 0.85, P < 0.001 and r = 0.87, P < 0.001 for the two estimated values for right atrial pressure, respectively). The regression equation using this formula was PVR(rhc) = 0.95 × PVR(echo)- 0.29, and the regression line was close to identity. The Bland-Altman plot showed a good agreement between PVR(echo) and PVR(rhc) values, with a mean difference of -0.66 ± 2.1 Wood unit.

CONCLUSION

The proposed Doppler-derived formula for estimating PVR based on the conventionally used invasive equation strongly correlates with invasive gold standard measures.

Pulmonary artery acceleration time provides an accurate estimate of systolic pulmonary arterial pressure during transthoracic echocardiography

BACKGROUND

Transthoracic echocardiographic estimates of peak systolic pulmonary artery pressure are conventionally calculated from the maximal velocity of the tricuspid regurgitation (TR) jet. Unfortunately, there is insufficient TR to determine estimated peak systolic pulmonary artery pressure (EPSPAP) in a significant number of patients. To date, in the absence of TR, no noninvasive method of deriving EPSPAP has been developed.

METHODS

Five hundred clinically indicated transthoracic echocardiograms were reviewed over a period of 6 months. Patients with pulmonic stenosis were excluded. Pulsed-wave Doppler was used to measure pulmonary artery acceleration time (PAAT) and right ventricular ejection time. Continuous-wave Doppler was used to measure the peak velocity of TR (TR(Vmax)), and EPSPAP was calculated as 4 × TR(Vmax)(2) + 10 mm Hg (to account for right atrial pressure). The relationship between PAAT and EPSPAP was then assessed.

RESULTS

Adequate imaging to measure PAAT was available in 99.6% of patients (498 of 500), but 25.3% (126 of 498) had insufficient TR to determine EPSPAP, and 1 patient had significant pulmonic stenosis. Therefore, 371 were included in the final analysis. Interobserver variability for PAAT was 0.97. There were strong inverse correlations between PAAT and TR(Vmax) (r = -0.96), the right atrial/right ventricular pressure gradient (r = -0.95), and EPSPAP (r = -0.95). The regression equation describing the relationship between PAAT and EPSPAP was log(10)(EPSPAP) = -0.004 (PAAT) + 2.1 (P < .001).

CONCLUSIONS

PAAT is routinely obtainable and correlates strongly with both TR(Vmax) and EPSPAP in a large population of randomly selected patients undergoing transthoracic echocardiography. Characterization of the relationship between PAAT and EPSPAP permits PAAT to be used to estimate peak systolic pulmonary artery pressure independent of TR, thereby increasing the percentage of patients in whom transthoracic echocardiography can be used to quantify pulmonary artery pressure.

Validation of noninvasive measurements of cardiac output in mice using echocardiography

BACKGROUND

Although multiple echocardiographic methods exist to calculate cardiac output (CO), they have not been validated in mice using a reference method.

METHODS

Echocardiographic and flow probe measurements of CO were obtained in mice before and after albumin infusion and inferior vena cava occlusions. Echocardiography was also performed before and after endotoxin injection. Cardiac output was calculated using left ventricular volumes obtained from an M-mode or a two-dimensional view, left ventricular stroke volume calculated using the pulmonary flow, or estimated by the measurement of pulmonary velocity time integral (VTI).

RESULTS

Close correlations were demonstrated between flow probe-measured CO and all echocardiographic measurements of CO. All echocardiographic-derived CO overestimated the flow probe-measured CO. Two-dimensional image-derived CO was associated with the smallest overestimation of CO. Interobserver variability was lowest for pulmonary VTI-derived CO.

CONCLUSION

In mice, CO calculated from two-dimensional parasternal long-axis images is most accurate when compared with flow probe measurements; however, pulmonary VTI-derived CO is subject to less variability.

Fetal cardiac output and its distribution to the placenta at 11-20 weeks of gestation

OBJECTIVES

To measure serial changes in cardiac output (CO) and its fraction distributed to the placenta at 11-20 weeks of gestation.

METHODS

Blood flow velocities, and diameters of the aorta, pulmonary artery and umbilical vein, were measured longitudinally in 143 fetuses using pulsed-wave Doppler and two-dimensional ultrasound examination.

RESULTS

Volume blood flow of the aorta (left ventricular CO) and the pulmonary artery (right ventricular CO) increased in a similar manner with advancing gestational age. The combined cardiac output (CCO) increased from 9 mL/min to 121 mL/min, and the placental volume blood flow (Q(uv)) increased from 1.2 mL/min to 25.3 mL/min during 11-20 weeks of gestation. The fraction of CCO diverted to the placenta increased from 14% at 11 weeks to 21% at 20 weeks.

CONCLUSIONS

We have established longitudinal reference ranges for fetal CO and Q(uv) at 11-20 weeks of gestation. The fraction of CCO distributed to the placenta increased significantly during this period, reflecting rapid placental growth and establishment of a low-resistance circulation.

Fetal cardiac output in monochorionic twins

OBJECTIVES

To compare fetal cardiac output (CO) in donor and recipient twins of twin-twin transfusion syndrome (TTTS) pregnancies after laser therapy with that of monochorionic twins without TTTS and normal singletons.

METHODS

In a longitudinal, prospective study, we sonographically assessed fetal CO in donors (n = 10) and recipients (n = 10) with TTTS after fetoscopic laser therapy, in monochorionic twins without TTTS (n = 20) and in normal singleton pregnancies (n = 20). The fetal CO of TTTS twins was determined 1 day and 1 week after laser treatment, and from then on every 2-4 weeks until birth. Twins without TTTS were examined biweekly until birth. Singletons were examined twice, with an 8-week interval, at different gestational ages between 17 and 35 weeks.

RESULTS

Absolute CO increased exponentially with advancing gestational age (P < 0.0001), and was significantly related to fetal weight in all groups (P < 0.0001). The median CO/kg in donors after laser therapy, recipients after laser therapy and non-TTTS monochorionic twins was significantly higher than that in singletons (all P < 0.001). Median CO/kg in donors after laser therapy, recipients after laser therapy, and non-TTTS monochorionic twins was not significantly different between groups.

CONCLUSIONS

Monochorionic twins with TTTS have higher CO after laser therapy than normal singletons.

A practical approach to the quantification of valvular regurgitation

This article reviews the methods of determining the severity of mitral and aortic regurgitation, primarily the quantitation using Doppler echocardiography. The Doppler methods, including spatial mapping, proximal flow convergence, vena contracta, continuous-wave Doppler density, and upstream or downstream effects are explained. Various practical pitfalls and performance issues that impact the reliability of these techniques are discussed.

Echocardiographic automated cardiac output measurement of pulmonary output and quantification of intracardiac shunt

BACKGROUND

The quantification of intracardiac shunt (ICS) with echocardiographic pulsed-wave Doppler (PWD) method using pulmonary-to-systemic flow ratio (QP/QS ratio) remains difficult and may induce false quantification of pulmonary output. We sought to validate the recent echocardiographic automated cardiac output measurement (ACM) for the calculation of pulmonary output and the quantification of ICS in adults.

METHODS

One hundred and twenty consecutive patients were divided in 1) 40 patients who underwent echocardiographic and invasive explorations (group I) with groups IA (quantification of ICS using ACM, PWD and invasive oximetric methods in 20 patients) and IB (calculation of pulmonary output with ACM, PWD and thermodilution methods in 20 patients); 2) 80 patients underwent calculation of aortic and pulmonary outputs using echocardiographic ACM and PWD methods (group II).

RESULTS

The feasibility of ACM and conventional PWD methods for the calculation of pulmonary output was respectively 93.3% and 90%. Correlations between ACM and invasive pulmonary output were strong (r2=0.92 vs. r2=0.80 for PWD). The best correlation and agreement between invasive and echocardiographic QP/QS ratio were observed with ACM (r=0.96 vs. r=0.82 for PWD). Intracardiac shunts were best-classified with ACM, as compared to PWD (respectively 94% and 72%); sensitivities and specificities for evaluation of significant ICS were 92.3% and 100% with ACM (85% and 40% with PWD).

CONCLUSIONS

This study shows that ACM is a reliable and accurate echocardiographic method for calculating pulmonary output and quantifying ICS in adults and may be routinely performed in clinical practice.

Doppler Tissue Imaging Evaluation of Right Ventricular Function at Rest and During Dobutamine Infusion in Patients After Repair of Tetralogy of Fallot

BACKGROUND

Reliable, non-invasive evaluation of right ventricular function, especially in congenital heart disease, is challenging.

OBJECTIVES

The aim of this study was to evaluate Doppler tissue imaging (DTI) parameters of lateral tricuspid annular motion, mean rate of pressure rise during RV contraction (mean dP/dt) and indexed right ventricular (RV) stroke volume (RVSVi) as RV function indices in repaired tetralogy of Fallot (TOF).

METHODS

DTI evaluation was performed in 25 repaired-TOF patients, aged 11+/-6, at rest and during dobutamine infusion and 20 controls at rest.

RESULTS

TOF patients had lower (P<0.05) peak systolic velocity (Sa) (11.4+/-4 vs. 13.7+/-3.1 cm/s), early diastolic velocity (Ea) (11+/-3.1 vs. 16.3+/-3.5 cm/s) and Sa/time from onset of QRS to Sa (Sa/Q-Sa) (68.8+/-26.4 vs. 92.3+/-29.4 cm/s2) versus controls. Dobutamine increased (P<0.01) Sa (11.4+/-2.8-17.7+/-4.7 cm/s), Ea (11+/-3.1-15.6+/-3.9 cm/s), late diastolic velocity (Aa) (8.4+/-2-14.8+/-5 cm/s), Sa/Q-Sa (68.8+/-26.4-17 6.8+/-84.5 cm/s2), mean dP/dt (180+/-74-537+/-37 2 mmHg/s), and RVSVi (7.8+/-3.9-11.9+/-5.6 L/min/m2). RVSVi increase correlated (P<0.01) with that in Sa (r=0.6), Ea (r=0.5), Sa/Q-Sa (r=0.71), and mean dP/dt (r=0.57) while mean dP/dt increase correlated strongly with Sa/Q-Sa increase (r=0.88).

CONCLUSION

DTI evaluation of tricuspid annular motion during dobutamine infusion in repaired TOF correlates with dP/dt and RV stroke volume and may help in assessing RV function and reserve.

Flow-Dependent Changes in Doppler-Derived Aortic Valve Effective Orifice Area Are Real and Not Due to Artifact

OBJECTIVES

We sought to determine whether the flow-dependent changes in Doppler-derived valve effective orifice area (EOA) are real or due to artifact.

BACKGROUND

It has frequently been reported that the EOA may vary with transvalvular flow in patients with aortic stenosis. However, the explanation of the flow dependence of EOA remains controversial and some studies have suggested that the EOA estimated by Doppler-echocardiography (EOA(Dop)) may underestimate the actual EOA at low flow rates.

METHODS

One bioprosthetic valve and three rigid orifices were tested in a mock flow circulation model over a wide range of flow rates. The EOA(Dop) was compared with reference values obtained using particle image velocimetry (EOA(PIV)).

RESULTS

There was excellent agreement between EOA(Dop) and EOA(PIV) (r2 = 0.94). For rigid orifices of 0.5 and 1.0 cm2, no significant change in the EOA was observed with increasing flow rate. However, substantial increases of both EOA(Dop) and EOA(PIV) were observed when stroke volume increased from 20 to 70 ml both in the 1.5 cm2 rigid orifice (+52% for EOA(Dop) and +54% for EOA(PIV)) and the bioprosthetic valve (+62% for EOA(Dop) and +63% for EOA(PIV)); such changes are explained either by the presence of unsteady effects at low flow rates and/or by an increase in valve leaflet opening.

CONCLUSIONS

The flow-dependent changes in EOA(Dop) are not artifacts but represent real changes in EOA attributable either to unsteady effects at low flow rates and/or to changes in valve leaflet opening. Such changes in EOA(Dop) can be relied on for clinical judgment making.

Stroke volume and systolic time intervals: beat-to-beat comparison between echocardiography and ambulatory impedance cardiography in supine and tilted positions

The aim of the study was to compare stroke volume (SV), ejection time (ET) and pre-ejection period (PEP) measurements obtained using a central haemodynamics ambulatory monitoring device based on impedance cardiography (ICG), in supine and tilted positions (60 degrees), with pulsed Doppler echocardiography as a non-invasive reference method. The Holter-type ICG device was used for off-line, beat-to-beat, automatic determination of SV, ET and PEP. ICG data were compared with those obtained simultaneously using pulsed Doppler echocardiography in the ascending aorta from a suprasternal projection, 1 min before and 10 min after tilting. The tests were performed in 13 young, healthy subjects (six men and seven women, aged 23-33 years). Linear regression between the measured values obtained for all subjects was described by the following formulas: SVicg= 13.9 + 0.813 x SVecho (r = 0.857, SEE = 9.03, n = 496), ETicg = 16.8 + 0.987 x ETecho (r = 0.841, SEE=21.3, n = 496), PEPicg= 22.8 + 0.890 x PEPecho (r = 0.727, SEE = 14.6, n = 496). The data showed that ambulatory impedance cardiography gives useful absolute values of SV and systolic time intervals measured in supine and tilted positions.

Transoesophageal echocardiography is unreliable for cardiac output assessment after cardiac surgery compared with thermodilution*

This randomised, single-blind, double-control study compared and established prospectively the best transoesophageal echocardiography methods for determining cardiac output in patients after cardiac surgery. Thirty patients undergoing coronary artery bypass grafting were included. Measurements were taken postoperatively, after stabilisation in the intensive care unit. Cardiac output was determined by transoesophageal echocardiography in randomised order through the aortic, mitral, and pulmonary valves, right and left ventricular outflow tracts, transgastric surface areas of the left ventricle and left ventricle two-dimensional volumes (Simpson's rules). 'Eyeball guessing' was done off-line. The best results were transaortic measurements using the triangular shape assumption of valve opening, but some values deviated considerably, and none of these approaches reached the limit of agreement set at 30% when compared to thermodilution. Eyeball guessing was comparable to the best transoesophageal echocardiography measurements. We conclude that transoesophageal echocardiography is an unreliable tool for determination of cardiac output in intensive care after cardiac surgery.

Automated volumetric flow quantification using angle-corrected color Doppler image

We have developed a fully automated method for measuring volumetric blood flow with angle-corrected blood velocity from a color Doppler image. By computing the blood flow vector through a conduit, the angle of incidence between the direction of ultrasound beam and the direction of blood flow can be measured to correct the underestimated blood velocity. This correction immediately contributes to the improvement of measurement accuracy. The developed method also enhances the conduit identification procedure that is one of the most important factors affecting the accuracy of volumetric measurement. To evaluate the validity of the developed algorithm, experimental studies had been applied to 21 healthy subjects and 10 patients. Volumetric flows were measured from a color Doppler image of the left ventricular outflow track, which were compared with blood volumes that were measured by traditional pulsed-wave (PW)-Doppler technique. The mean stroke volume difference between two methods was -0.45 +/- 11.7 (mean +/- SD). The proposed algorithm is a viable method for determining blood flow volume in an automated fashion.

Noninvasive assessment of fetal pulmonary blood flow in experimental pulmonary hypertension in the fetal lamb

The aim of this study was to assess pulmonary arterial blood flow changes induced by the creation of a systemic arteriovenous fistula (120 d gestation) in the fetal lamb using Doppler technique. Doppler echocardiographic assessment of the pulmonary artery blood flow performed 1, 6, and 14 d after surgery showed that mean pulmonary arterial blood flow in the left or right pulmonary artery was 224 +/- 58 mL/min at day 1 in the fistula group, significantly higher than in the control group (113 +/- 22 mL/min; p < 0.01, ANOVA test) whether no difference was found at days 6 and 14. The mean inner diameter of the left pulmonary artery measured on postmortem lung arteriograms compared favorably to the one measured on day 14 at the same level on ultrasound. The mean left pulmonary arterial blood flow, measured at birth on day 14 after surgery, using ultrasonic flow transducer, was not statistically different from the one measured by Doppler on day 14. Our data demonstrate that echocardiography allows accurate assessment of pulmonary arterial blood flow in utero, providing evidence suggesting transient high pulmonary blood flow that did not last >6 d after the creation of a systemic fistula.

Doppler echocardiography for the estimation of cardiac output with exercise

Insights into both normal and pathological cardiac responses to exercise have been hampered by lack of a safe, accurate, feasible means of estimating cardiac output (Q) during high-intensity and maximal exercise. Doppler ultrasound noninvasively measures blood velocity as it exits the heart and can be performed during exhaustive exercise without interference of the subject or need for steady state. From the product of aortic blood velocity and cross-sectional area of the aorta, stroke volume (SV) can be calculated. Despite these advantages of the Doppler technique, a number of potential sources of error have raised concern regarding the accuracy of this method. These include transducer angulation, change in aortic cross-sectional area during exercise, turbulence and alteration of a flat velocity profile in the aorta with increased Q, and uncertainties regarding the proper location for measurement of aortic outflow area. The magnitude of the influence of these potentially confounding variables on the accuracy of SV measurements determined by the Doppler technique is unknown. Estimates of both construct and concurrent validity suggest that the overall error may be small. Test-retest studies have indicated a high level of reliability with this technique.

Agenesis of the ductus venosus that is associated with extrahepatic umbilical vein drainage: prenatal features and clinical outcome

OBJECTIVE

We sought to study the clinical and ultrasonographic findings and outcomes of fetuses with ductus venosus agenesis as the result of extrahepatic umbilical vein drainage.

STUDY DESIGN

This was an observational study of 12 fetuses who were diagnosed with these anomalies between 1995 and 2001.

RESULTS

The umbilical vein drained either directly into the right atrium (n = 7 fetuses), the inferior vena cava (n = 3 fetuses), or the iliac vein (n = 2 fetuses). Combined cardiac output (n = 8 fetuses) was nearly 2-fold increased to 891 +/- 210 mL/kg per minute. Other relevant findings were (1) considerable umbilical vein enlargement (12/12 cases; range, 8-13 mm) with an accelerated (peak, 0.53 +/- 0.1 m/s), (2) pulsatile Doppler flow pattern within its intra-abdominal course, (3) cardiomegaly (12/12 fetuses), (4) secundum atrial septal defects (5/12 fetuses), (5) extracardiac anomalies (5/12 fetuses), (6) polyhydramnios (4/12 fetuses), and (7) progressive heart failure (3/12 fetuses). Two fetuses died: 1 death was unexplained at 29 weeks of gestation; the other death from hydrops occurred after delivery at 32 weeks of gestation. So far, none of the survivors have had other long-term sequelae that were related to ductus venosus agenesis.

CONCLUSION

Careful assessment of the umbilical venous return and the ductus venosus should be part of the routine evaluation of every fetus with heart failure and polyhydramnios.

A validation study of aortic stroke volume using dynamic 4-dimensional color Doppler: an in vivo study

OBJECTIVE

To explore the feasibility of directly quantifying transaortic stroke volume with a newly developed dynamic 3-dimensional (3D) color Doppler flow measurement technique, an in vivo experimental study was performed.

BACKGROUND

Traditional methods for flow quantification require geometric assumptions about flow area and flow profiles. Accurate quantification of flow across the aortic valve is clinically important as a means of estimating cardiac output.

METHODS

Eight open-chest sheep were scanned with apical epicardial placement of a 7 to 4 MHz multiplane transesophageal probe scanning parallel to aortic flow and running on an ATL HDI 5000 system. An electromagnetic flow meter implanted on the ascending aorta was used as reference. Thirty different hemodynamic conditions were studied after steady states were obtained in the animals by administration of blood, angiotensin, and sodium nitroprusside. Electrocardiogram-gated digital color 3D velocity data were acquired for each of the 30 steady states. The aortic stroke volumes were computed by temporal and spatial integration of flow areas and actual velocities across a projected surface perpendicular to the direction of flow, at a level just below the aortic valve.

RESULTS

There was close correlation between the 3D color Doppler calculated aortic stroke volumes and the electromagnetic data (r = 0.91, y = 0.96x + 1.01, standard error of the estimate = 2.6 mL/beat).

CONCLUSION

Our results showed that dynamic 3D color Doppler measurements obtained in an open-chest animals provide the basis for accurate, geometry-independent quantitative evaluation of the aortic flow. Therefore, 3D digital color Doppler flow computation could potentially represent an important method for noninvasively determining cardiac output in patients.

A new dynamic three-dimensional digital color doppler method for quantification of pulmonary regurgitation: validation study in an animal model

OBJECTIVES

The purpose of the present study was to validate a newly developed three-dimensional (3D) digital color Doppler method for quantifying pulmonary regurgitation (PR), using an animal model of chronic PR.

BACKGROUND

Spectral Doppler methods cannot reliably be used to assess pulmonary regurgitation.

METHODS

In eight sheep with surgically created PR, 27 different hemodynamic states were studied. Pulmonary and aortic electromagnetic (EM) probes and meters were used to provide reference right ventricular (RV) forward and pulmonary regurgitant stroke volumes. A multiplane transesophageal probe was placed directly on the RV and aimed at the RV outflow tract. Electrocardiogram-gated and rotational 3D scans were performed for acquiring dynamic 3D digital velocity data. After 3D digital Doppler data were transferred to a computer workstation, the RV forward and pulmonary regurgitant flow volumes were obtained by a program that computes the velocity vectors over a spherical surface perpendicular to the direction of scanning.

RESULTS

Pulmonary regurgitant volumes and RV forward stroke volumes computed by the 3D method correlated well with those by the EM method (r = 0.95, mean difference = 0.51 +/- 1.89 ml/beat for the pulmonary regurgitant volume; and r = 0.91, mean difference = -0.22 +/- 3.44 ml/beat for the RV stroke volume). As a result of these measurements, the regurgitant fractions derived by the 3D method agreed well with the reference data (r = 0.94, mean difference = 2.06 +/- 6.11%).

CONCLUSIONS

The 3D digital color Doppler technique is a promising method for determining pulmonary regurgitant volumes and regurgitant fractions. It should have an important application in clinical settings.

Acute effects of cardiac resynchronization therapy on left ventricular Doppler indices in patients with congestive heart failure

BACKGROUND

Patients with heart failure frequently exhibit intraventricular conduction delays, which contribute to asynchronous contraction patterns and impaired hemodynamic performance. Cardiac resynchronization therapy (CRT) with biventricular (BV) and left ventricular (LV) pacing has been shown to improve both hemodynamic and clinical performance. This study investigated the effects of CRT on LV Doppler indices in these patients.

METHODS AND RESULTS

Thirty-two patients with advanced heart failure (New York Heart Association class > or =III, QRS >120 milliseconds, PR interval >150 milliseconds) were studied 4 weeks after implantation of a CRT system. Doppler echocardiography was conducted in 3 separate CRT modes, right ventricular, LV, and BV stimulation at 3 different atrioventricular delays. CRT resulted in significant improvement of Doppler parameters such as filling time (FT, 313 +/- 111 milliseconds at baseline --> 363 +/- 154 milliseconds [BV], P <.05), aortic velocity time integral (AO(VTI) 23.2 +/- 7.4 cm at baseline --> 26.8 +/- 8.8 cm [LV], P <.05), and the myocardial performance index (MPI, 1.21 +/- 0.51 at baseline --> 0.85 +/- 0.34 [BV], P <.05). The most improvement was observed with LV and BV stimulation at short and intermediate atrioventricular delays (80-120 milliseconds), independent of ischemic or idiopathic origin.

CONCLUSIONS

CRT improves hemodynamic performance in patients with heart failure with intraventricular conduction delays. Doppler echocardiography allows noninvasive evaluation of acute CRT effects in patients with heart failure. In particular, FT, AO(VTI), and MPI are useful parameters for noninvasive follow-up and optimization of pacing parameters.

Dobutamine echocardiography in patients with aortic stenosis and left ventricular dysfunction: predicting outcome as a function of management strategy

STUDY OBJECTIVE

To prospectively address the question whether the assessment of valvular hemodynamics and myocardial function during low-dose dobutamine infusion can guide decision making in patients with aortic stenosis and left ventricular (LV) dysfunction.

PATIENTS AND MEASUREMENTS

Twenty-four patients with aortic stenosis and LV dysfunction (mean ejection fraction, 28%; New York Heart Association class, II to IV) were studied by dobutamine echocardiography assessing mean pressure gradient, aortic valve area, and aortic valve resistance. Patients were prospectively divided into severe and nonsevere aortic stenosis groups according to the response of the valve area to the augmentation of systolic flow. The clinical decision was considered to be concordant with the results of dobutamine echocardiography, when patients with severe aortic stenosis and preserved contractile function were referred by a specialist for aortic valve replacement and when patients with nonsevere aortic stenosis were not. Patients were observed for up to 3 years.

RESULTS

All eight patients with severe aortic stenosis who were referred for surgery survived and had good cardiovascular outcomes, and six of eight patients who were not initially referred for surgery had poor outcomes, including heart failure and sudden cardiac death. The eight patients with nonsevere aortic stenosis did comparatively well without valve replacement. Cardiac death or pulmonary edema occurred in 4 of 16 patients (25%) when the clinical decision was concordant with the results of the dobutamine echocardiogram and occurred in 6 of 8 patients (75%) when the clinical decision was discordant (p = 0.019 [chi(2) test]).

CONCLUSION

Patients with aortic stenosis, LV dysfunction, and relatively low gradients have better outcomes when management decisions are based on the results of dobutamine echocardiograms. Those patients identified as having severe aortic stenosis and preserved contractile reserve by dobutamine echocardiography should undergo surgery, while patients identified as having nonsevere aortic stenosis can be managed conservatively.

Assessment of ventricular filling volumes with an automated color Doppler method: validation in a pulsatile flow model

OBJECTIVE

Determination of ventricular filling volumes with the use of Doppler echocardiographic measurements critically depends on the presence of a circular-shaped flow area and a flat velocity profile across it because evaluation of flow volume is usually based on echocardiographic measurements of its diameter and pulsed Doppler recordings within the center of this area. The approach may be limited at the mitral and tricuspid ring levels as a result of their noncircular shape and because nonflat velocity profiles are present. The purpose of this study was to examine in a pulsatile flow model simulating ventricular inflow conditions the accuracy of an automated method based on the analysis of color Doppler flow velocities for evaluation of flow volumes.

MATERIALS AND METHODS

A recently-developed automated Doppler method that takes into account the velocity distribution across a region of interest was examined in a pulsatile flow model by using flows with waveforms characteristic for ventricular inflow through tubes with elliptically-shaped cross-sectional areas. Color Doppler imaging was performed against flow direction along the major and minor axes of the tubes with major diameters ranging between 3 and 5 cm and major-to-minor diameter ratios of 1.5 and 2.0.

RESULTS

A close correlation was found between flow volumes measured by the Doppler technique for registrations along the minor or major axis of the ellipses and actual values (r = 0.99, standard error of the estimate = 0.44 to 1.98 mL), with a systematic underestimation or overestimation, respectively, depending on the diameter ratio. Averaging of the data derived from 2 orthogonal measurements by using the geometric mean value yielded an excellent agreement between Doppler data and actual flow volumes.

CONCLUSION

This automated color Doppler method enables reliable determination of flow volumes in a pulsatile flow model simulating ventricular inflow conditions with the use of 2 orthogonal imaging views. The data indicate that the method may improve the noninvasive evaluation of ventricular filling volumes.

Fetal cardiac performance in uncomplicated and well-controlled maternal type I diabetes

OBJECTIVE

To study the impact of well-controlled, uncomplicated maternal diabetes on fetal cardiac development and performance.

METHODS

The following variables were studied in 45 fetuses of type I diabetic women by means of mid- and late-trimester echocardiography: interventricular septal thickness; aortic and pulmonary valve diameters; peak and time-to-peak flow velocity of the great arteries; the ratio between peak velocities during early (E) and late (A) ventricular filling at the level of the atrioventricular values; ventricular fractional shortenings; and output. The findings were compared to age-matched control groups of normal fetuses.

RESULTS

A significant augmentation of interventricular septal thickness was demonstrated for mid-trimester fetuses of diabetic women, which progressed further towards the end of pregnancy. However, the indices of diastolic and systolic function remained comparable between the gestational age-matched groups.

CONCLUSION

Progressive myocardial thickening occurs commonly in mid- and late-trimester fetuses of uncomplicated and well-controlled diabetic pregnancies. The observed degree of hypertrophy is generally mild and does not affect age-related changes in fetal cardiac function.

A semiautomated objective technique for applying the proximal isovelocity surface area method to quantitate mitral regurgitation: Clinical studies with the digital flow map

BACKGROUND

Clinical application of the color Doppler proximal isovelocity surface area (PISA) method to quantify mitral regurgitation (MR) has been limited by the often inaccurate assumption that isovelocity surfaces are hemispheric. This study applied an objective method for selecting the region where the hemispheric geometry holds best on the basis of mathematic analysis of results at different distances from the orifice. We aimed to demonstrate this approach can be applied accurately in the clinical setting and can be semiautomated to promote routine use by extracting velocities from the digital Doppler output and then performing all the calculations automatically.

METHODS

In 75 patients with isolated MR, centerline velocities (V(r)) at each distance (r) from the orifice in the proximal flow field were extracted digitally. The automated analysis calculated peak MR flow rates as 2pir(2)V(r) and plotted these against their respective velocities. The optimal value for peak flow rate was obtained mathematically at the site where the slope of this curve was minimal (least inaccuracy). This value was combined with continuous wave Doppler data to provide regurgitant stroke volume (RSV) and orifice area (ROA), which were compared with quantitative Doppler in 75 patients and angiography in 42.

RESULTS

RSV and ROA by this optimized, semiautomated PISA method correlated and agreed well with values from quantitative Doppler (y = 0.9x + 1.9, r = 0.90, standard error of the estimate [SEE] = 8.1 mL, mean difference = -0.7 +/- 8.5 mL for RSV; y = 0.9x + 0.02, r = 0.90, SEE = 0.048 cm(2), mean difference = -0.005 +/- 0.1 cm(2) for ROA) and correlated well with angiography (rho = 0.90 for both RSV and ROA).

CONCLUSIONS

This objective PISA method for quantifying MR is accurate in the clinical setting and has been semiautomated by use of analysis of digital velocity data to provide a rapid and practical technique suitable to facilitate more extensive application in routine practice.

Accuracy and cost- and time-effectiveness of digital clip versus videotape interpretation of echocardiograms in patients with valvular disease

BACKGROUND

Although digital and videotaped images are known to be comparable for the evaluation of left ventricular function, their relative accuracy for assessment of more complex anatomy is unclear. We sought to compare reading time, storage costs, and concordance of video and digital interpretations across multiple observers and sites.

METHODS

One hundred one patients with valvular (90 mitral, 48 aortic, 80 tricuspid) disease were selected prospectively, and studies were stored according to video and standardized digital protocols. The same reviewer interpreted video and digital images independently and at different times with the use of a standard report form to evaluate 40 items (e.g., severity of stenosis or regurgitation, leaflet thickening, and calcification) as normal or mildly, moderately, or severely abnormal. Concordance between modalities was expressed at kappa. Major discordance (difference of >1 level of severity) was ascribed to the modality that gave the lesser severity. CD-ROM was used to store digital data (20:1 lossy compression), and super-VHS videotape was used to store video data. The reading time and storage costs for each modality were compared.

RESULTS

Measured parameters were highly concordant (ejection fraction was 52% +/- 13% by both). Major discordance was rare, and lesser values were reported with digital rather than video interpretation in the categories of aortic and mitral valve thickening (1% to 2%) and severity of mitral regurgitation (2%). Digital reading time was 6.8 +/- 2.4 minutes, 38% shorter than with video (11.0 +/- 3.0, range 8 to 22 minutes, P <.001). Compressed digital studies had an average size of 60 +/- 14 megabytes (range 26 to 96 megabytes). Storage cost for video was A$0.62 per patient (18 studies per tape, total cost A$11.20), compared with A$0.31 per patient for digital storage (8 studies per CD-ROM, total cost A$2.50).

CONCLUSION

Digital and video interpretation were highly concordant; in the few cases of major discordance, the digital scores were lower, perhaps reflecting undersampling. Use of additional views and longer clips may be indicated to minimize discordance with video in patients with complex problems. Digital interpretation offers a significant reduction in reading times and the cost of archiving.

Cardiac output and central distribution of blood flow in the human fetus

BACKGROUND

The objectives of this study were to establish reference ranges for left and right cardiac output and to investigate blood flow distribution through the foramen ovale, ductus arteriosus, and pulmonary bed in human fetuses.

METHODS AND RESULTS

A prospective study was performed in 222 normal fetuses from 13 to 41 weeks of gestation with high-resolution color Doppler ultrasound. Cardiac output and ductal flow were calculated by use of vessel diameter and the time-velocity integral. Pulmonary blood flow was expressed as the difference between right cardiac output and ductal flow. Foramen ovale flow was estimated as the difference between pulmonary flow and left cardiac output. Gestational age-specific reference ranges are given for left, right, and biventricular output and volume of ductal blood flow, showing an exponential increase with gestational age. Median ratio of right to left cardiac output was 1.42 and was not associated with gestational age. Right cardiac output was 59% and left cardiac output was 41% of biventricular cardiac output. Median biventricular cardiac output was estimated to be 425 mL. min(-1). kg(-1) fetal weight. Ductal blood flow was 46%, estimated pulmonary flow was 11%, and estimated foramen ovale flow was 33% of biventricular output.

CONCLUSIONS

The study establishes reference ranges for fetal cardiac output and offers insights into the central blood flow distribution in human fetuses from 13 weeks to term. There is a clear right heart dominance. The estimated ratio of pulmonary blood flow to cardiac output is higher than in fetal lamb studies.

Hemodynamic-induced changes in aortic valve area: implications for Doppler cardiac output determinations

Monitoring cardiac output (CO) by transesophageal echocardiography involves measurements of ascending aortic flow and an initial measurement of aortic valve area (AVA). Hemodynamic-induced changes in AVA are a potential source of error for this simplified method. Our goal was to quantify these changes in AVA and their effects on CO calculations. In 17 anesthetized patients, a dobutamine infusion was titrated to achieve a 50% increase in ascending aortic flow velocity (V(max)). Hemodynamic and echocardiographic variables, including V(max) and planimetry of AVA, were determined at baseline and at maximal dobutamine dose. Dobutamine produced a 3.0 +/- 1.4 L/min increase in CO, a 54.5% +/- 19.6% increase in V(max), and a 50.6% +/- 34.2% increase in systolic blood pressure. AVA increased by 4.3% +/- 2.6% during dobutamine infusion (P < 0.001). The simplified CO method, which does not account for increases in AVA, produced a 0.32 +/- 0.24 L/min underestimation of CO. This investigation demonstrates hemodynamic-induced changes in AVA. The use of a single AVA measurement for all subsequent CO calculations introduces a clinically acceptable degree of error, supporting a simplified CO protocol requiring less probe manipulation and reduced procedural time.

IMPLICATIONS

An intraoperative dobutamine infusion was used to increase aortic blood flow and demonstrate hemodynamic-induced changes in aortic valve area. These valve-area changes affect the accuracy of Doppler cardiac output determinations.