The echocardiographic assessment of pulmonary artery pressure and pulmonary vascular resistance

A prediction model of echocardiographic variables to screen for potentially correctable shunts in adult atrial septal defect-pulmonary hypertension patients

BACKGROUND

Atrial septal defect (ASD) is a prevalent congenital heart condition in adults that leads to pulmonary hypertension (PAH) and right heart failure if left untreated. During a routine follow-up of adult ASD-PAH patients, the suitability of shunt closure depends on the invasive right heart catheterization (RHC). Nevertheless, performing RHC at every follow-up is impractical and may be harmful. The present retrospective cross-sectional study was designed to investigate which echocardiographic variables were associated with pulmonary vascular resistance (PVR) in adult ASD-PAH patients and propose a model using these variables to screen for patients with a correctable shunt.

METHODS

A total of 530 adult ASD-PAH patients with pulmonary arterial systolic pressure (PASP) of ≥60 mmHg measured using transthoracic echocardiogram (TTE) were included in the study. All RHCs were performed within 3 months after TTE. The correctable shunt was defined as PVR ≤3 Wood units (WU). Multivariable regressions were performed utilizing echocardiographic variables. A scoring system was constructed based on the predictors of PVR ≤3 WU using multivariable logistic regression analysis. The scoring system was then examined using a receiver operating characteristic (ROC) analysis. In addition, clinical utility of the model was determined based on decision curve analysis, and a calibration curve was used to evaluate model conformity.

RESULTS

Estimated PASP, velocity through the pulmonary valve, tricuspid annulus early diastolic velocity, and maximum defect dimension were identified as independent predictors. The area under the ROC curve of the predictive value in the model was 0.905 (95% CI, 0.878-0.931, sensitivity: 84.3%, specificity: 83.6%). The net benefit of the model was notable in terms of a wide-range probability threshold in decision curve analysis, indicating that the prediction model had good clinical applicability. The model's calibration curve was close to an ideal diagonal line, showing good predictive accuracy between the actual and predictive probabilities.

CONCLUSION

The study provided a valuable model in predicting adult ASD-PAH patients with a correctable shunt, which may help clinicians to make appropriate treatment decision for follow-up patients.

Evaluation of cardiac function in pediatric patients with mild to moderate bronchial asthma in the era of cardiac strain imaging

OBJECTIVE

Bronchial asthma is a common chronic inflammatory airway disease, which may be associated with pulmonary hypertension and cardiac dysfunction. The aim of this study was to evaluate the ability of 2D-speckle tracking echocardiography (2D-STE) and tissue doppler imaging (TDI) to detect subtle cardiac dysfunction in pediatric patients with mild to moderate bronchial asthma.

METHODOLOGY

The study included 30 children with mild to moderate bronchial asthma and 27 age-matched healthy controls. Both groups underwent pulmonary function tests, TDI and 2D-STE. Myocardial performance index (MPI), S', E', A' velocities, global strain of left ventricle (LV), right ventricle (RV), and right atrium (RA) were measured.

RESULTS

RV diastolic function was impaired in the patient group, as the tricuspid E' velocity was significantly lower in the patients when compared with the controls (16 [14-17] vs 16 [17-19] cm/s, P = .044), while the RV-MPI was significantly higher in patients when compared to controls (0.30 [0.27-0.36] vs 0.30 [0.30-0.30], P = .001). The global RV longitudinal strain, RA strain, and LV strain did not show significant differences between the test and the control groups. RV systolic parameters and LV systolic and diastolic parameters did not differ significantly between the two groups.

CONCLUSION

Pediatric patients with mild to moderate bronchial asthma may have early RV diastolic dysfunction with preserved other cardiac functions.

Doppler evaluation of the fetal pulmonary artery pressure

Background The Doppler effect has allowed the characterization of several vessels in maternal-fetal circulation that have been used for practical purposes. Our review of the literature showed a paucity of information about fetal pulmonary artery pressure (FMPAP) and its behavior in regard to gestational age (GA). The objectives of the study were to evaluate a formula to calculate the main FMPAP and its correlation with GA. Methods A total of 337 fetuses without obvious pathology were studied prospectively using Doppler evaluation of the FMPAP. Using the fetal main pulmonary artery Doppler acceleration time (FMPAT), we obtained the FMPAP using the following formula: FMPAP=90 - (0.62×FMPAT). Regression analyses, Pearson's bivariate correlation and paired sample t-test were used when appropriate. Results FMPAT increases while FMPAP decreases with GA. Pearson's correlation coefficient for FMPAP and GA was -0.544 (P-value<0.001) and for FMPAT and GA was 0.556 (P-value<0.001). FMPAP and FMPAT were highly correlated (R=-0.972; P<0.001). Conclusion Pulmonary artery pressure in the fetus decreases with GA.

Analysis of Biphasic Right Ventricular Outflow Doppler Waveform in Patients with Pulmonary Hypertension

Pulmonary hypertension (PH) with pulmonary vascular disease (PVD) is a progressive and debilitating disease associated with increased pulmonary vascular resistance (PVR). Biphasic right ventricular outflow tract (RVOT) Doppler flow is frequently seen in severe PH patients with PVD. In association with hemodynamics, the precise analysis of biphasic RVOT Doppler flow (RVDF) has not been fully elucidated. Therefore, the purpose of the present study is to analyze the relation between the hemodynamics and indices of biphasic RVDF in PH patients with PVD.Seventy PH patients with biphasic RVDF were analyzed. All patients underwent transthoracic echocardiography and right heart catheterization. For the analysis of biphasic RVDF, the early waveform was determined as P₁ while the late waveform was determined as P₂. For each P₁ and P₂, the duration (D, seconds) and peak flow velocity (PFV, in m/second) were measured.P₁D and P₂PFV were significantly correlated with PVR (P₁D: r = -0.542, P < 0.0001, P₂PFV: r = -0.513, P < 0.0001). Therefore, we propose a novel RVDF formula for estimation of PVR, as follows. PVR = 26 - 77 × P₁D - 14 × P₂PFV. The PVR could be estimated by this proposed formula (r = 0.649, P < 0.0001), which is derived from one Doppler image only unlike previously used PVR prediction formula.P₁D and P₂PFV were associated with PVR. Moreover, this simple RVDF formula proposed herein can estimate PVR in PH patients with PVD.

Noninvasive Echocardiographic Measures of Pulmonary Vascular Resistance in Children and Young Adults with Cardiomyopathy

BACKGROUND

Patients with cardiomyopathy (CM) are at increased risk for pulmonary hypertension (PH). Data are lacking on the use of noninvasive PH measures by echocardiography in patients with CM. The aim of this study was to evaluate the correlation between Doppler-derived echocardiographic indices and catheterization-based measurement of pulmonary vascular resistance (PVR) in children and young adults with CM.

METHODS

Imaging studies were retrospectively reviewed from pediatric patients with CM who underwent both echocardiography and cardiac catheterization within a 72-hour period. The ratio of peak tricuspid regurgitation velocity to right ventricular outflow tract velocity-time integral, the S/D ratio, and right ventricular myocardial performance index were correlated with invasive PVR. Receiver operating characteristic curves were developed to determine cutoffs for detecting PVR ≥ 6 indexed Wood units, a value associated with higher heart transplantation risk.

RESULTS

Twenty-three patients with CM (median age, 11.7 years; range, 0.5-21 years) met the criteria for analysis, the majority (n = 17 [74%]) of whom had dilated CM. Linear regression showed significant correlations between echocardiography-based ratio of peak tricuspid regurgitation velocity to right ventricular outflow tract velocity-time integral, S/D ratio, and right ventricular myocardial performance index versus invasive PVR (r = 0.84, r = 0.72, and r = 0.72, respectively, P < .001). All echocardiographic measures showed high sensitivity, specificity, and predictive values to detect PVR ≥ 6 indexed Wood units, with ratio of peak tricuspid regurgitation velocity to right ventricular outflow tract velocity-time integral demonstrating the highest area under the curve (0.958; 95% CI, 0.866-1).

CONCLUSIONS

Right-sided Doppler-derived echocardiographic indices correlate with PVR measured by cardiac catheterization in children and young adults with CM. These parameters may serve as useful adjuncts in serial assessment of right ventricular hemodynamics in this population.

Non-Invasive Assessment of Pulmonary Vascular Resistance in Pulmonary Hypertension: Current Knowledge and Future Direction

Pulmonary Hypertension (PHT) is relatively common, dangerous and under-recognised. Pulmonary hypertension is not a diagnosis in itself; it is caused by a number of differing diseases each with different treatments and prognoses. Therefore, timely and accurate recognition of the underlying cause for PHT is essential for appropriate management. This is especially true for patients with Pulmonary Arterial Hypertension (PAH) in the current era of disease-specific drug therapy. Measurement of Pulmonary Vascular Resistance (PVR) helps separate pre-capillary from post-capillary PHT, and is measured with right heart catheterisation (RHC). Echocardiography has been used to derive a number of non-invasive surrogates for PVR, with varying accuracy. Ultimately, the goal of non-invasive assessment of PVR is to separate PHT due to left heart disease from PHT due to increased PVR, to help streamline investigation and subsequent treatment. In this review, we summarise the physiology and pathophysiology of pulmonary blood flow, the various causes of pulmonary hypertension, and non-invasive surrogates for PVR.

Evaluation of the left and right ventricular systolic and diastolic function in asthmatic children

Background

Asthma is the most common cause of respiratory disorders among children. We aimed to investigate left (LV) and right (RV) ventricular function in asthmatic children as detected by conventional and tissue Doppler echocardiography.

Methods

Fifty pediatric patients with asthma and forty healthy children were studied. Pulmonary function tests, electrocardiography and echocardiographic examinations were performed on all children.

Results

Rate-corrected velocity of circumferential fiber shortening (VCFc) (p = 0.044), the ratio between heights of early and late diastolic flow velocity peaks (E/A) (p = 0.019) and LV end-systolic wall stress (ESWSm) was lower (p = 0.003), RV stroke volume (SV) (p = 0.002), LV SV (p = 0.001), tricuspid annular plane systolic excursion (TAPSE) (p = 0.034), tricuspid annular peak velocity during systole (S’) (p = 0.022), tricuspid and mitral early diastolic velocities (E’) (p = 0.012, p = 0.003 respectively) were lower in asthmatic children than controls. The mitral valve ejection time (ET) was high in asthmatic group (p = 0.027).

FEV1 was positively correlated with isovolumetric relaxation time (IVRT) (p = 0.018) (r = 0.382) and mitral ET (p = 0.018) (r = 0.381). PEF was negatively correlated with the RV work index (p = 0.032) (r = -0.348) and LV work index (p = 0.005) (r = -0.457).

Conclusion

Although cardiac systolic function was found to be impaired in asthmatic patients, contrary to the literature, diastolic dysfunction was not observed in these patients, even by tissue Doppler imaging, and this finding may be attributed to using inhaled corticosteroid

Echocardiography in pediatric pulmonary hypertension

Pulmonary hypertension (PH) can be a rapidly progressive and fatal disease. Although right heart catheterization remains the gold standard in evaluation of PH, echocardiography remains an important tool in screening, diagnosing, evaluating, and following these patients. In this article, we will review the important echocardiographic parameters of the right heart in evaluating its anatomy, hemodynamic assessment, systolic, and diastolic function in children with PH.

A simple echocardiographic method to estimate pulmonary vascular resistance

Pulmonary hypertension includes heterogeneous diagnoses with distinct hemodynamic pathophysiologic features. Identifying elevated pulmonary vascular resistance (PVR) is critical for appropriate treatment. We reviewed data from patients seen at referral pulmonary hypertension clinics who had undergone echocardiography and right-side cardiac catheterization within 1 year. We derived equations to estimate PVR using the ratio of estimated pulmonary artery (PA) systolic pressure (PASPDoppler) to right ventricular outflow tract velocity time integral (VTI). We validated these equations in a separate sample and compared them with a published model based on the ratio of the transtricuspid flow velocity to right ventricular outflow tract VTI (model 1, Abbas et al 2003). The derived models were as follows: PVR = 1.2 × (PASP/right ventricular outflow tract VTI) (model 2) and PVR = (PASP/right ventricular outflow tract VTI) + 3 if notch present (model 3). The cohort included 217 patients with mean PA pressure of 45.3 ± 11.9 mm Hg, PVR of 7.3 ± 5.0 WU, and PA wedge pressure of 14.8 ± 8.1 mm Hg. Just >1/3 had a PA wedge pressure >15 mm Hg (35.5%) and 82.0% had PVR >3 WU. Model 1 systematically underestimated catheterization estimated PVR, especially for those with high PVR. The derived models demonstrated no systematic bias. Model 3 correlated best with PVR (r = 0.80 vs r = 0.73 and r = 0.77 for models 1 and 2, respectively). Model 3 had superior discriminatory power for PVR >3 WU (area under the curve 0.946) and PVR >5 WU (area under the curve 0.924), although all models discriminated well. Model 3-estimated PVR >3 was 98.3% sensitive and 61.1% specific for PVR >3 WU (positive predictive value 93%; negative predictive value 88%). In conclusion, we present an equation to estimate the PVR, using the ratio of PASPDoppler to right ventricular outflow tract VTI and a constant designating presence of right ventricular outflow tract VTI midsystolic notching, which provides superior agreement with catheterization estimates of PVR across a wide range of values.

Assessment of pulmonary arterial hypertension and vascular resistance by measurements of the pulmonary arterial flow velocity curve in the absence of a measurable tricuspid regurgitant velocity in childhood congenital heart disease

This study aimed to determine mean pulmonary arterial pressure (PAPmean) and pulmonary vascular resistance (PVR) using transthoracic echocardiography (TTE) measurements of the pulmonary artery flow velocity curve in children with pulmonary arterial hypertension (PAH) and congenital heart disease when the tricuspid regurgitant velocity (TRV) is not sufficient. This study enrolled 29 congenital heart disease cases with pulmonary arterial hypertension and 40 healthy subjects followed at our center. The mean age was 66.9 ± 77.9 months in the patient group and 76.3 ± 62.1 months in the control group. A positive correlation was found between TRV and systolic pulmonary arterial pressure (r = 0.394, p = 0.035, 95% confidence interval [CI] = 0.032-0.665), whereas a negative correlation was found between corrected acceleration time (AcTc) and PAPmean (r = -0.559, p = 0.002, 95% CI = -0.768 to -0.242). Furthermore, a negative correlation was found between parameters TRV and AcTc (r = -0.383, p = 0.001, 95% CI = -0.657 to -0.019). Based on the cutoff criterion of 124 ms for AcTc, sensitivity was found to be 79.3% and specificity to be 77.5% in distinguishing between the PAH patients and the healthy control patients (receiver operating characteristic [ROC] area under the curve [AUC] = 0.804, 95% CI = 0.691-0.890, p < 0.0001). The sensitivity and specificity of the concomitant use of AcTc and/or TRV were found to be 90 and 73%, respectively, in distinguishing between the PAH patients and the the healthy control patients. The data obtained by TTE also can be appropriate for measuring PAPmean, PVR, and the vasoreactivity test and for determining the priority of implementing cardiac catheterization even if there is no measurable TRV value.

Estimation of pulmonary vascular resistance: correlation between echocardiography and catheterization data in patients with congenital heart disease

BACKGROUND

The ratio of peak tricuspid regurgitation velocity (TRV) and right ventricular outflow time-velocity integral (TVI RVOT) has been described as a good correlate of pulmonary vascular resistance (PVR). However, this method has not been well studied in congenital heart disease.

METHOD

Twenty patients with post-tricuspid shunt lesions who were planned to undergo cardiac catheterization were enrolled for the study. The ratio of TRV/TVI(RVOT) was measured via transthoracic echocardiography and correlated with invasively derived PVR (PVR(CATH)). PVR(CATH) was measured by cardiac catheterization. Fick's principle was used to calculate the pulmonary blood flow and oxygen consumption was assumed. Linear regression analysis was done to find the correlation between TRV/TVI(RVOT) and PVR(CATH).

RESULTS

There was a significant correlation between the two variables, r = 0.635(P = 0.003). Subgroup analysis revealed that this correlation was better at lower values of PVR(CATH) (r = 0.817 for PVR < 6 Wood units (WU)) than higher values (r = 0.659 for PVR > 6 WU). TRV/TVI(RVOT) ratio of greater than 0.145 predicted with 80% sensitivity and specificity a PVR > 6 WU.

CONCLUSIONS

There is modest correlation between TRV/TVI(RVOT) ratio and invasively derived PVR in congenital shunt lesions, especially in PVR < 6 WU. TRV/TVI(RVOT) ratio could be useful in identifying patients with congenital shunts whose PVR is likely to be <6 WU, and hence, do not need cardiac catheterization.

Accuracy of Doppler-derived estimation of pulmonary vascular resistance in congenital heart disease: an index of operability

Pulmonary vascular resistance (PVR) is a critical and essential parameter during the assessment and selection of modality of treatment in patients with congenital heart disease (CHD) accompanied by pulmonary arterial hypertension (PAH). Cardiac catheterization is the "gold standard" but is an invasive method for PVR measurement. A noninvasive and reliable method for estimation of PVR in children has been a major challenge and most desirable during past decades, especially for those who need repeated measurements. In a prospective study and among consecutive patients who were referred for cardiac catheterizations, PVR was calculated as the ratio of the transpulmonary pressure gradient (∆P) to the amount of the pulmonary flow (QP) accordingly for 20 patients with CHD and high PAH. Subsequently and noninvasively, PVR was assessed for these patients by a Doppler echocardiography-derived index defined as the ratio of the tricuspid regurgitation velocity (TRV(m/s)) to the velocity time integral (VTI(cm)) of the right-ventricular outflow tract (RVOT). There was a good correlation between PVR measured at catheterization (PVR(cath)) and TRV/VTI(m) ratio; the mean of three measurements of VTI (VTI(m)) with R (2) = 0.53 (p = 0.008). In addition, a TRV/VTI(m) value of 0.2 provided a sensitivity of 71.4% and a specificity of 100% for PVR >6 Woods units (WU) as well as sensitivity of 90% and specificity of 90% for a PVR equal to 8 WU. PVR value between 6 and 8 WU by catheterization has been considered as a cut-off point for intervention in children with left-to-right shunts and PAH. In conclusion, Doppler-derived TRV/VTI(m) ratio is a reliable index that may be helpful as a supplementary diagnostic tool for the selection of modality of treatment and follow-up of patients with PAH and increased PVR.

Estimation of Pulmonary Vascular Resistance with Doppler Diastolic Gradients

This study was undertaken to determine the diastolic Doppler echocardiographic correlates of pulmonary vascular resistance calculated on cardiac catheterization in patients with secondary pulmonary arterial hypertension. Thirty-eight consecutive patients with congenital heart disease, pulmonary artery hypertension and pulmonary regurgitation were studied. Continuous-wave Doppler-derived pulmonary artery diastolic gradients were measured at 3 points on the pulmonary regurgitant diastolic velocity slope: peak diastolic, end-diastolic (at the R wave on the electrocardiogram), and mid-diastolic (midway between the peak and end-diastolic points). Catheterization data included oximetry, measurements of pressure in the cardiac chambers and great arteries, and calculation of pulmonary vascular resistance index. Doppler-derived peak, mid, and end-diastolic pulmonary regurgitation gradients correlated best with catheterization-measured pulmonary artery systolic, mean and diastolic pressures, respectively. The best Doppler correlate of pulmonary vascular resistance index was the pulmonary artery end-diastolic gradient. Clinically useful information can be obtained from Doppler pulmonary artery diastolic gradients measured on the pulmonary regurgitant diastolic velocity slope, which can estimate the pulmonary arterial pressure as well as pulmonary vascular resistance obtained on cardiac catheterization.

Echocardiographic and right heart catheterization techniques in patients with pulmonary arterial hypertension

BACKGROUND

The cardiovascular assessment of patients with suspected pulmonary arterial hypertension (PAH) involves Doppler echocardiography and often subsequent confirmation by right heart catheterization (RHC). However, there appears to be limited consensus on the appropriate technique(s) for assessing PAH, and thus no clear, comprehensive guidelines exist for assessment of PAH. The aim of this paper is to review the Doppler echocardiographic and RHC techniques for the diagnosis and/or assessment of PAH.

METHOD

We searched Medline (1966 to August 2006) and EMBASE (1980 to August 2006) bibliographic databases to allow identification of all potentially relevant studies and review articles. In addition, the reference lists of included articles were scanned to identify relevant references and unpublished reports missed by the search strategy.

RESULTS

Our findings show that recommendations for the echocardiographic assessment of PAH at rest or with exercise are heterogeneous. Clinical practice guidelines provide limited details. Although more specific information regarding echocardiographic techniques can be obtained from individual research articles, the techniques employed and the methods used to calculate specific hemodynamic variables do not appear to be consistent throughout the literature. RHC techniques for the confirmation of PAH are more consistent, albeit less frequently reported. The literature search identified several articles where indications and considerations for the catheterization of patients with PAH are discussed, together with safety considerations and principles for the accurate assessment of hemodynamic variables.

CONCLUSION

Although clinical practice guidelines and numerous research studies provide details of echocardiographic measures in patients with PAH, greater consensus and standardisation of measurement techniques is required. A minimum dataset for the evaluation of PAH by these techniques is suggested.

Echocardiographic Assessment of Right Heart Hemodynamic Parameters

Echocardiography is currently the primary clinical method for the noninvasive measurement of right heart hemodynamic parameters and is an indispensable tool for the initial assessment, diagnosis, longitudinal follow-up, and prognostication of patients with abnormal right heart function. This review will discuss the echocardiographic methods used to estimate right heart hemodynamic parameters.

Use of myocardial performance index in pediatric patients with idiopathic pulmonary arterial hypertension

BACKGROUND

The myocardial performance index (MPI) correlates with clinical status in adults with idiopathic pulmonary arterial (PA) hypertension (IPAH). This pediatric study used MPI to assess response to bosentan therapy.

METHODS

The study included 12 children with IPAH and 12 healthy control subjects. MPI was correlated with catheterization data at initiation of bosentan and at a median follow-up of 9 months. Therapy responders were defined by a greater than 20% decrease in mean PA pressure.

RESULTS

Right ventricular MPI for patients with IPAH was 0.64 +/- 0.30 versus 0.28 +/- 0.03 in control subjects (P < .01). It had a strong correlation with mean PA pressure (R = 0.94; P < .001). Right ventricular MPI decreased significantly in responders (range 20%-44%, mean 25%) with a 5% increase in nonresponders.

CONCLUSIONS

Right ventricular MPI in pediatric IPAH correlates with mean PA pressure and response to therapy. This study suggests that this noninvasive Doppler index may be useful to follow up children with IPAH, particularly when tricuspid regurgitation data are insufficient.

Doppler tissue imaging in assessment of pulmonary hypertension-induced right ventricle dysfunction

We aimed to assess the accuracy of Doppler tissue imaging (DTI) in detecting right ventricle (RV) dysfunction and electromechanical coupling alteration following pulmonary hypertension (PHT) in rat. PHT was induced by chronic hypoxia exposure (hypoxic PHT) or monocrotaline treatment (monocrotaline PHT). In both PHT models, we observed transparietal RV pressure increase and remodeling, including hypertrophy and dilation. Conventional echocardiography provided evidence for pulmonary outflow impairment with midsystolic notch and acceleration time decrease in PHT groups (21.7 +/- 1.6 and 13.2 +/- 2.9 ms in hypoxic and monocrotaline PHT groups vs. 28.1 +/- 1.0 ms in control). RV shortening fraction was decreased in the monocrotaline PHT group compared with the hypoxic PHT and control groups. Combining conventional Doppler and DTI was more helpful to detect RV diastolic dysfunction in the monocrotaline PHT group (E/Ea ratio = 17.0 +/- 1.4) compared with the hypoxic PHT and control groups (11.5 +/- 0.7 and 10.2 +/- 0.4, respectively). Tei index measured using DTI highlighted global RV dysfunction in the monocrotaline PHT group (1.36 +/- 0.24 vs. 0.92 +/- 0.05 and 0.86 +/- 0.05 in the hypoxic PHT and control groups, respectively). Q-Sm time measured from the onset of Q wave to the onset of DTI Sm wave was increased in both PHT groups. PHT-induced electromechanical coupling alteration was confirmed by in vitro activation-contraction delay measurements on isolated RV papillary muscle, and both Q-Sm time and activation-contraction delay were correlated with PHT severity. We demonstrated that Q-Sm time measured in DTI was an easily and convenient index to detect early RV electromechanical coupling alteration in both moderate and severe PHT.

Echocardiography in pulmonary vascular disease

The assessment of pulmonary artery pressure, right ventricular function, right ventricular filling pressure, and tricuspid regurgitation provides invaluable information in the care of patients with pulmonary vascular disease. Echocardiography provides a rapid, noninvasive, portable, and accurate method to evaluate these parameters and also provides information on left ventricular and valvular function. Echocardiography has therefore become one of the most commonly performed diagnostic studies in patients with pulmonary vascular disease, and the technique's applications in this area are likely to grow. This article presents an overview of the current uses of echocardiography in pulmonary vascular disease and pulmonary hypertension.

A simple method for noninvasive estimation of pulmonary vascular resistance

OBJECTIVES

We sought to test whether the ratio of peak tricuspid regurgitant velocity (TRV, ms) to the right ventricular outflow tract time-velocity integral (TVI(RVOT), cm) obtained by Doppler echocardiography (TRV/TVI(RVOT)) provides a clinically reliable method to determine pulmonary vascular resistance (PVR).

BACKGROUND

Pulmonary vascular resistance is an important hemodynamic variable used in the management of patients with cardiovascular and pulmonary disease. Right-heart catheterization, with its associated disadvantages, is required to determine PVR. However, a reliable noninvasive method is unavailable.

METHODS

Simultaneous Doppler echocardiographic examination and right-heart catheterization were performed in 44 patients. The ratio of TRV/TVI(RVOT) was then correlated with invasive PVR measurements using regression analysis. An equation was modeled to calculate PVR in Wood units (WU) using echocardiography, and the results were compared with invasive PVR measurements using the Bland-Altman analysis. Using receiver-operating characteristics curve analysis, a cutoff value for the Doppler equation was generated to determine PVR >2WU.

RESULTS

As calculated by Doppler echocardiography, TRV/TVI(RVOT) correlated well (r = 0.929, 95% confidence interval 0.87 to 0.96) with invasive PVR measurements. The Bland-Altman analysis between PVR obtained invasively and that by echocardiography, using the equation: PVR = TRV/TVI(RVOT) x 10 + 0.16, showed satisfactory limits of agreement (mean 0 +/- 0.41). A TRV/TVI(RVOT) cutoff value of 0.175 had a sensitivity of 77% and a specificity of 81% to determine PVR >2WU.

CONCLUSIONS

Doppler echocardiography may provide a reliable, noninvasive method to determine PVR.

Serial noninvasive assessment of progressive pulmonary hypertension in a rat model

Current methods used to investigate pulmonary hypertension in rat models of the disease allow for only one to two measurements of pulmonary artery (PA) pressure in the life of a rat. We investigated whether transthoracic echocardiography can be used to assess the progression of pulmonary hypertension in rats at multiple time points. Serial echocardiographic measurements were performed over a 6-wk period on rats injected with monocrotaline (MCT) or placebo. Development of a midsystolic notch in the PA waveform, a decrease in the PA flow acceleration time (PAAT), an increase in right ventricular (RV) free-wall thickness, and the development of tricuspid regurgitation (TR) were observed as pulmonary hypertension developed. Changes in the PA waveform and PAAT began in week 3 of disease development as the PA systolic pressure (PASP) reached 25-30 mmHg according to right heart catheterization. The RV free-wall thickness increased significantly by week 5 (PASPs 40-50 mmHg). Development of quantifiable TR occurred in week 6 or at PASPs > 65 mmHg. A linear correlation was found between the PAAT and PASP in the range of 30-65 mmHg and between the RV-right atrial pressure gradient (derived from TR velocity) and PASP at pressures >65 mmHg, which enabled a noninvasive estimate of the PASP over a wide range of pressures based on these parameters. These data indicate that transthoracic echocardiography can be used for monitoring the progress of pulmonary hypertension in a rat model.

Ventriculo-vascular interaction in the normal development of the fetal circulation

OBJECTIVES

To examine cardiovascular physiology in the healthy fetus during normal development.

DESIGN

Twenty normal fetuses were studied longitudinally from 20 weeks to term. Serial echocardiography was performed, and arterial and venous diameter pulse wave characteristics and aortic pulse wave propagation velocity (PWV) were examined in the thoracic descending aorta (AoD) and inferior caval vein (IVC) using an ultrasonic phase-locked echo-tracking system. Statistical analyses included ANOVA, paired t-test and logistic regression where appropriate.

RESULTS

Aortic PWV, maximum incremental and late decremental velocities increased with gestation while the relative pulse amplitude decreased, reflecting falling distal impedance. There was a linear increase in cardiac preload and relative pulse amplitude in the IVC with gestation that correlated significantly with the presence of end-diastolic flow in the pulmonary artery and improvement in right ventricular diastolic function.

CONCLUSIONS

Non-invasive concurrent assessment of preload, ventricular function and impedance are possible in the fetus and may prove useful in the longitudinal study of fetal adaptation to pathophysiological changes.

Pulmonary arterial pressure can be estimated by transesophageal pulsed doppler echocardiography

We examined whether pulmonary arterial pressure can be estimated on the basis of pulmonary arterial flow velocity determined via intraoperative pulsed Doppler transesophageal echocardiography (TEE) in 20 patients undergoing cardiac surgery. Standard pulmonary artery measurements were taken as well. Measurements were taken before sternotomy, after pericardiotomy, after cardiopulmonary bypass, and after sternum closure. The variables obtained by TEE included preejection period (PEP), acceleration time (AT), right ventricular ejection time (RVET), and R-R interval (RR). Five ratios were calculated as indices of pulmonary arterial pressure--PEP/AT, PEP/RVET, AT/RVET, PEP/ square root of RR, and AT/ square root of RR--and were compared with pulmonary artery catheterization findings, i.e., systolic pulmonary arterial pressure (sPAP), log sPAP, mean PAP (mPAP), and log mPAP. Before sternotomy, PEP/AT, PEP/ square root of RR, and AT/ square root of RR showed significant correlation with all pulmonary artery catheterization values. AT/RVET showed correlation with all pulmonary artery values except log mPAP. PEP/AT showed the closest correlation with sPAP (r = 0.771) and log sPAP (r = 0.789). PEP/AT also showed close correlation with mPAP (r = 0.764) and log mPAP (r = 0.777). Significant agreement between sPAP and mPAP values calculated from a regression equation and values measured via pulmonary artery catheter was observed by plotting the differences against the mean values of the two measurements. We therefore conclude that noninvasive estimation of pulmonary arterial pressure is feasible via intraoperative TEE when sternotomy is not involved.

Neonatal pulmonary hypertension during extracorporeal membrane oxygenation

OBJECTIVES

This prospective study was designed to monitor severe pulmonary hypertension during extra corporeal membrane oxygenation using echo Doppler variables.

BACKGROUND

All neonates treated with extracorporeal membrane oxygenation also have severe pulmonary hypertension. A study which monitors the reaction of the pre-existing pulmonary hypertension during extracorporeal oxygenation by frequent sampling of those variables related to pulmonary pressure is still lacking. Such a study is necessary to analyze the complex haemodynamic changes in patients undergoing extracorporeal membrane oxygenation.

METHOD

In 29 neonates, we estimated pulmonary arterial pressure using peakflow velocity of regurgitation across the tricuspid- and pulmonary valve, peakflow velocity of shunting across persistent arterial ductus, and systolic time intervals of the right ventricle. Correlation between the several estimations of pulmonary arterial pressure were analysed with the Spearman correlation coefficient.

RESULTS

Systolic pulmonary arterial pressure measured by the velocity of tricuspid regurgitation illustrated severe pulmonary hypertension prior to extra corporeal membrane oxygenation (mean 63 mmHg, sd 20). Similar levels for the systolic pulmonary arterial pressure could be derived (mean 73 mmHg, sd 17) from ductal shunting. A fair correlation of 0.76 (p< 0.002) could be demonstrated. Pulmonary hypertension responded well and quickly to treatment by extra corporeal membrane oxygenation, with reductions within 24 hours to mean systolic levels of 35 mmHg, sd 23. This very early reaction has not previously been demonstrated and could be of importance in defining parameters for weaning from cardiopulmonary bypass. Diastolic pulmonary arterial pressure was investigated because of its relation to vascular resistance. It proved more difficult to measure because of the low incidence of pulmonary regurgitation. Derived diastolic pressures did not show any good correlations.

CONCLUSION

Pulmonary hypertension is well documented prior to extra corporeal membrane oxygenation and response very quickly to the institution of treatment. Ultra sound techniques are indicated at the bedside, and prove useful in monitoring pulmonary blood pressure during the procedure.

Haemodynamic effects of altering arterial oxygen saturation in preterm infants with respiratory failure

AIMS

To examine the haemodynamic effects of brief alteration in arterial oxygenation in preterm infants with respiratory failure.

METHODS

Eighteen preterm infants with respiratory failure, aged 9-76 hours, underwent detailed Doppler echocardiographic assessment at 86%, 96%, and 100% SaO2, achieved by altering the FIO2. Sixteen were receiving intermittent positive pressure ventilation, median FIO2 0.45 (0.20-0.65), median mean airway pressure 12 cm H2O (0-20). SaO2 was stable for 15 minutes at each stage. Four parameters of pulmonary arterial pressure were measured: peak velocity of tricuspid regurgitation and peak velocity of left to right ductal flow, TPV:RVET ratio and PEP:RVET ratio, measured at the pulmonary valve, along with flow velocity integrals at the aortic and pulmonary valves, and systemic arterial pressure. Ductal size was graded into closed, small, moderate, large with imaging, pulsed and continuous wave Doppler.

RESULTS

Between 86% and 96% SaO2, there were no consistent changes, but in three of the 12 with a patent ductus arteriosus (PDA) there was ductal constriction, with complete closure in one. Between 96% and 100% SaO2, peak ductal flow velocity rose significantly in four of eight with a PDA. Ductal constriction occurred in four infants; in three this was associated with a significant fall in aortic flow integral and a rise in aortic pressure (4-6 mm Hg). Overall, 11 infants went from 86% to 100% SaO2 and pulmonary arterial pressure fell significantly in seven.

CONCLUSION

A brief rise in SaO2 within the range maintained by most neonatal units can cause significant ductal constriction. The fall in pulmonary arterial pressure with 100% SaO2 seen in most infants was associated with a fall in pulmonary blood flow (or no change), rather than a rise, indicating that the dominant haemodynamic effect was ductal constriction rather than pulmonary vasodilation.

Echocardiographic Features of Right Heart Failure in Infancy and Childhood

In infants and children, right heart failure is most frequently a consequence of increased afterload (pulmonary hypertension). However, it is also observed as a sequela of congenital cardiovascular surgery. The purpose of this report is to present the causes of right heart dysfunction in children and to define the echo-Doppler methods used in the evaluation of right heart failure.

Delayed postnatal adaptation of pulmonary hemodynamics in infants of diabetic mothers

OBJECTIVE

To test the hypothesis with Doppler ultrasound method that the postnatal adaptation of the pulmonary and ductal hemodynamics in infants of diabetic mothers is disturbed.

STUDY DESIGN

Infants of diabetic mothers are prone to respiratory distress caused by characteristic fetal metabolic abnormalities such as hyperglycemia and hyperinsulinemia with subsequent excess fetal growth. However, the postnatal course of the pulmonary and ductal hemodynamics is poorly known in these neonates. The presence of ductal shunting and the mean aortopulmonary pressure difference across the ductus arteriosus reflecting pulmonary artery pressure, as well as the left ventricular output, were serially evaluated with Doppler ultrasound method at 2, 12, 24, 48, and 72 hours of age in 47 infants of diabetic mothers and 37 control neonates of nondiabetic mothers.

RESULTS

The infants of diabetic mothers had a higher incidence of patent ductus arteriosus at 12 (p = 0.03) and 48 hours (p = 0.006) of life than control infants, but none of the infants of diabetic mothers needed ductal closure. Bidirectional ductal shunting was found more frequently in infants of diabetic mothers than control infants during the first day of life. The mean ductal aortopulmonary pressure difference was significantly higher in the control infants than in infants of diabetic mothers during the first 24 hours of life (p = 0.002). The mean systemic pressure values were higher in the infants of diabetic mothers than control infants (p = 0.002), but no significant differences in the left ventricular output were seen between the study groups during the first 3 days of life.

CONCLUSIONS

The closure of the ductus arteriosus and postnatal decrease in pulmonary artery pressure are delayed in infants of diabetic mothers when compared with control infants during the first days of life. Left ventricular output values in infants of diabetic mothers do not differ from those of the control infants.

Doppler echocardiographic evaluation of pulmonary vascular resistance in children with congenital heart disease

Noninvasive assessment of pulmonary vascular resistance has not been well defined. Cardiac catheterization findings in 33 patients with congenital heart disease (mean age 1.4 years) were compared with Doppler echocardiographic parameters. The right ventricular pre-ejection period (RVPEP), ejection time (RVET), and the ration RVPEP/RVET correlated better with pulmonary vascular resistance than with pulmonary artery pressure. A highly significant correlation with a small standard error of estimate (SEE) was demonstrated between pulmonary vascular resistance and a newly derived parameter RVPEP/velocity time integral (VTI) [r = 0.87, p < 0.0001, SEE = 2]. An RVPEP/VTI value of < 0.4 seconds/meter (M) was able to select patients with pulmonary vascular resistance < 3 Wood Unit.M2, even in the presence of pulmonary artery hypertension caused by increased pulmonary blood flow, with 97% accuracy (100% sensitivity, and 92% specificity). An RVPEP/VTI value of 0.4 to 0.6 seconds/M identified patients with pulmonary vascular resistance between 3 to 7.5 Wood Unit.M2 with 91% accuracy, and a value of > or = 0.6 seconds/ M selected patients with total pulmonary vascular resistance > or = 7.5 Wood Unit.M2 with 94% accuracy.

Pulmonary vascular resistance during lipid infusion in neonates

Using two-dimensional echocardiography, pulmonary vascular resistance was estimated from right ventricular pre-ejection period to ejection time (RVPEP/ET) in 11 preterm infants with respiratory distress, to test the effect of different doses of continuous lipid infusion. Echocardiography was performed at baseline with no lipid infusing 2 and 24 hours after 1.5 and 3 g/kg/day of intravenous lipid, 24 hours after discontinuing intravenous lipid emulsion, and 2 hours after restarting intravenous lipid. After 24 hours of intravenous lipid at 1.5 g/kg/day the RVPEP/ET rose to mean (SD) 0.287 (0.03) from a baseline value of 0.225 (0.02) and to 0.326 (0.05) after 24 hours of intravenous lipid at 3 g/kg/day. Pulmonary arterial pressure returned to baseline 24 hours after the intravenous lipid had been discontinued. Continuous 24 hour infusion of lipid caused significant dose and time-dependent increases in pulmonary vascular resistance. Intravenous lipid may aggravate pulmonary hypertension.

The heart in sickle cell anemia. The Cooperative Study of Sickle Cell Disease (CSSCD)

The objective of this study was to obtain representative echocardiographic measurements of cardiac size and function in stable patients with sickle cell disease. This prospective, multicenter study utilized central reading of echocardiograms by an investigator blinded to other patient data. Stable outpatients from a balance of inner city and rural settings with SS phenotype and a broad age range were selected, because conflicting results from earlier studies were believed to be due to these patient selection criteria. Right and left ventricular dimensions and wall thickness, left atrial and aortic root dimensions, and systolic time intervals were measured. Body surface area indexed chamber dimensions and septal thickness were significantly increased from normal. Except for the right ventricle, chamber dimensions and wall thickness were inversely correlated with hemoglobin. The relationship between left ventricular dimension and hemoglobin was significantly dependent on age. Systolic time interval ratios were normal though left ventricular ejection time was prolonged. Shortening fraction was normal but velocity of circumferential fiber shortening was abnormally low. Stable patients with sickle cell disease have dilated chambers, septal hypertrophy, and normal contractility. Though left ventricular dilatation was inversely related to hemoglobin, age (duration of illness) was an important factor in that relationship. No specific cardiomyopathy was associated with sickle cell anemia.

Increased muscularization of small pulmonary arteries in preterm infants of diabetic mothers: a morphometric study in noninflated, noninjected, routinely fixed lungs

We attempted to identify a structural correlate of the pulmonary hypertension observed in newborn infants of diabetic mothers (IDM) by performing a morphometric analysis of pulmonary arteries at the transition of terminal to respiratory bronchiolus (TRB) in postmortem lungs of 20 IDM and 14 control infants. Although there was no readily apparent microscopic difference between the lungs of newborn IDM and controls, the degree of muscularization, as measured by mean medial area (MMA) of 10 TRB arteries, was significantly greater in preterm IDM (gestational age < or = 37 weeks) than in age-matched controls (502 versus 341 microns 2; P = .0038). Among infants of gestational age > 37 weeks, there was no significant difference between MMA in IDM (508 microns 2) and MMA in controls (598 microns 2). These findings point at an accelerated muscularization of the TRB arteries in IDM, apparent early in the third trimester. The pathogenesis of this hypermuscularization is not understood, but smooth muscle growth promoters such as insulin may play a role. The abnormal timing of TRB artery muscularization could be a manifestation of the basic disturbance in development that contributes to the pulmonary hypertension observed in newborn IDM and to the respiratory difficulties commonly experienced by these infants.

Haemodynamic changes in children with portal hypertension during the postoperative period

The cardiovascular changes following portosystemic shunt surgery (PSSS) in 33 children with extrahepatic portal hypertension (EPH) were studied to determine if portosystemic shunt surgery had any influence on the cardiovascular state. Haemodynamic data were obtained using two-dimensional and M-mode echocardiography, pulsed-wave Doppler and direct invasive techniques. Postoperatively all patients developed a hyperdynamic state, associated with an increase in cardiac index (CI), heart rate (HR) and a decrease in systemic vascular resistance index (SVRI). In 16 patients (group I), who preoperatively exhibited a hyperdynamic state accompanied by pulmonary hypertension, postoperative studies found an increase in acceleration time to ejection time ratio (AT/ET) in the pulmonary artery from 0.32 +/- 0.05 (mean +/- SEM) to 0.43 +/- 0.01; P < 0.01. Nine patients (group II) who were normodynamic preoperatively developed pulmonary hypertension and right ventricular (RV) dysfunction postoperatively: decrease in AT/ET from 0.42 +/- 0.02 (mean +/- SEM) to 0.32 +/- 0.01; P < 0.01 and an increase in maximal peak pulmonary artery velocity to acceleration time ratio (Vmax/AT) from 702.56 +/- 69.10 (mean +/- SEM) to 1127 +/- 105.30 cm.sec-2; P < 0.01. In eight patients (group III) who were normodynamic preoperatively and were treated with dobutamine infusions at a rate of 5 micrograms.kg-1.min-1 postoperatively, the CI was found to increase from 5.28 +/- 1.1 (mean +/- SEM) to 7.97 +/- 1.64 L.min-1.m-2; P < 0.01, left ventricular ejection fraction (LVEF) from 69.0 +/- 4.1 (mean +/- SEM) to 81.0 +/- 2.9%; P < 0.01 and AT/ET from 0.37 +/- 0.04 (mean +/- SEM) to 0.44 +/- 0.03; P < 0.01.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler evaluation of right ventricular outflow impedance during positive-pressure ventilation

Positive-pressure ventilation has often been advocated to increase oxygen delivery. This ventilation mode itself, however, can impair right ventricular ejection and, thus, diminish cardiac output. In this study, alterations of right ventricular outflow impedance were evaluated after stepwise increases of positive end-expiratory pressure (PEEP). Different pulmonary artery flow characteristics were evaluated with transesophageal echocardiography in mechanically ventilated postoperative coronary artery bypass surgery patients without pulmonary hypertension. A progressive decrease of pulmonary artery flow velocity and time velocity integrals was found with increasing PEEP levels. No changes in acceleration time or pre-ejection period were observed. In order to decrease the influence of heart rate, the ratios of the different pulmonary artery flow characteristics were calculated. At end-inspiration, both the ratio of acceleration time to right ventricular ejection period and the ratio of pre-ejection period to right ventricular ejection period showed progressive increases above 10 cmH2O positive end-expiratory pressure (13.3% at the level of 15 cmH2O and 8.5% at the level of 20 cmH2O). In this study, acceleration time appears not to be of importance in ventilated patients. These data strongly support the hypothesis that intermittent squeezing of the pulmonary arterial tree during inspiration, rather than positive end-expiratory pressure, creates an increase of right ventricular outflow impedance.

Right heart pressure determination by Doppler in infants with tricuspid regurgitation

Doppler and direct measurements of right ventricle to right atrial pressure drop were made during cardiac catheterisation on 28 occasions in 26 infants with congenital heart disease. Age was 10 days to 12 months (median 4.5 months), and weight was 3.1 to 9.0 kg (median 4.7 kg). We measured peak velocity of tricuspid regurgitation by continuous wave Doppler, and the pressure drop was calculated using the modified Bernoulli equation (delta p = 4v2). There was a high correlation (r = 0.95) between direct and Doppler measurements. Doppler values tended to underestimate the right ventricle to right atrial pressure drop, but this was not of clinical significance (mean 2 mm Hg). The 95% confidence interval for the Doppler velocity was -0.41 to +0.26 m/sec, and was consistent across the range of pressures studied. Variability between observers was tested, by two observers performing sequential paired examinations on 16 newborn babies with tricuspid regurgitation. The coefficient of repeatability was 6.3 mm Hg (95% confidence interval 4.7 to 9.5 mm Hg) or 0.26 m/sec (0.18 to 0.50 m/sec). This method of right ventricular pressure estimation, validated previously only in older children and adults, is a reproducible and accurate technique in infants with tricuspid regurgitation.

Analysis of left ventricular regional wall motion in normal neonates

OBJECTIVE

To investigate neonatal circulatory change by quantitative analysis of left ventricular regional wall motion.

DESIGN

Random prospective study.

SETTING

Department of paediatrics in a teaching hospital.

PARTICIPANTS

66 neonates born after a normal pregnancy, labour, and delivery.

INTERVENTIONS

Quantitative analysis of left ventricular regional wall motion was performed on cross sectional echocardiograms. M mode, cross sectional, and Doppler echocardiograms were obtained simultaneously.

MAIN OUTCOME MEASURES

Manually traced endocardial contours at end diastole and at end systole were realigned by superimposing the centre of the ventricular mass and the axis. The contours were divided into 24 segments with 24 radii of equal arc from the centre. Then the ratio of the change in area between the outline of the contour and the two hemiaxes was calculated automatically.

RESULTS

There was hyperkinesis of the interventricular septum in the first 24 hours after birth which continued until the end of the first week. Simultaneous echocardiographic examination showed evidence of pulmonary hypertension, as indicated by an increase in the ratio of the right pre-ejection period to the right ventricular ejection time (RPEP/RVET) and of the diameter ratio of the pulmonary artery to the aorta and a shortening of the acceleration time of pulmonary arterial blood flow. These features disappeared within a week.

CONCLUSIONS

Hyperkinesis of the interventricular septum may reflect circulatory changes that are characteristic of the early neonatal period.

New approaches to noninvasive assessment of pulmonary artery pressure

Direct measurement of pulmonary artery pressure (PAP) was performed in 36 patients; right ventricular (RV) isovolumic relaxation time (IRT) and RV systolic output acceleration time (AcT) values were assessed by pulsed Doppler and 2-M echocardiography. There was a fairly good correlation between RV IRT and systolic PAP (r = 0.898; SEE = 7.8 mmHg) and a somewhat weaker one between RV AcT and systolic PAP (r = -0.880; SEE = 8.37 mmHg). Correlation coefficients were the highest between systolic PAP and the [formula: see text] (r = 0.972; SEE = 4.14), and also between mean PAP and the 10-RV AcT/100 predictor: y = 158x + 6.7 (r = 0.951; SEE = 3.48 mmHg). With +/- 5 mmHg deviations, systolic PAP measurements were accurate in 78% and those of mean PAP in 98% of the patients. The double-blind assessment of the reproducibility of the suggested noninvasive PAP measurement was performed in 18 subsequent patients; the interstudy variability of the measurement was 0.88 +/- 0.94 mmHg and 1.22 +/- 1.23 mmHg (p > 0.05), whereas interobserver variability was 1.90 +/- 1.70 mmHg and 1.67 +/- 1.63 mmHg, respectively (p > 0.05). Thus, a combined use of the most informative intervals of RV cycle--IRT and AcT--contributes to the accuracy of noninvasive PAP measurement.

The role of Doppler echocardiography in the diagnosis, follow-up, and management of ventricular septal defects

The defects of the ventricular septum have received special attention from investigators working in echocardiography. The method showed an incomparable capability to identify all the morphological features of the defects. The increasing improvement in definition of transducers associated with conventional and color Doppler contributed significantly to the reliability to detect most of the defects. The great majority of associated lesions can be easily identified and serial examinations allow prediction of which defect may become smaller or even close spontaneously as well as which have acquired deleterious changes in the heart. Several authors have shown very good statistical correlations between echocardiographic indices and hemodynamic parameters in patients with this type of defect. Doppler echocardiography has become an invaluable tool in the diagnosis and follow-up of ventricular septal defect reducing the need for cardiac catheterization and helping management of these patients.

Doppler echocardiographic evaluation of pulmonary artery pressure in pneumonia of infants and children

Previously, there was insufficient evidence to confirm that pneumonia in infants and children might lead to the development of pulmonary hypertension. Recently, it has been shown that acceleration time corrected for heart rate (ATc) and the ratios of right ventricular preejection period to right ventricular ejection time (RPEP/RVET) and of right ventricular preejection period to acceleration time (RPEP/AT) derived from Doppler echocardiography correlated well with pulmonary artery pressure (PAP). To approach PAP in patients with infantile pneumonia, we measured RPEP/RVET, RPEP/AT, and ATc in 105 infants and children with pneumonia and in 17 controls, using a commercially available 2-dimensional echocardiograph (Toshiba SSH-40A) with SDS-21B Doppler unit. An increase of varying degrees in both ratios and ATc was noted during acute illness and significant differences in ratios RPEP/RVET and RPEP/AT were found among patients with mild, moderate, and severe disease. This suggested that PAP increased to different extents in the acute stage of illness and that the degree of increase was related to the severity of disease.

Doppler assessment of pulmonary artery pressure and extrapulmonary shunting in the acute phase of hyaline membrane disease

The natural history of pulmonary artery pressure and extrapulmonary shunting in acute hyaline membrane disease was studied by serial Doppler echocardiography in 57 preterm infants, 38 with, and 19 without, hyaline membrane disease. Pulmonary artery pressure was assessed non-invasively by its inverse relationship with the ratio of pulmonary artery Doppler time to peak velocity: right ventricular ejection time. The mean ratio was significantly lower in the infants with hyaline membrane disease. The mean ratio for each infant with hyaline membrane disease varied widely and did not correlate with criteria of maturity or severity of disease. Individual ratios correlated with arterial pH. Between 60-80 hours after birth, 14 of 18 infants with hyaline membrane disease (78%) and one of 19 without (5%) had patent ductus arteriosus. Left to right and bidirectional shunting at ductal and atrial level were common; pure right to left shunting was uncommon. The mean ratio seen with bidirectional shunting was significantly lower than that seen with left to right shunting. Ratios and patterns of extra pulmonary shunting were similar when the fractional inspired oxygen (FIO2) was greater than 0.9 compared with when it was less than 0.9. Pulmonary artery pressure is high during the acute phase of hyaline membrane disease but varies widely among infants. A few infants have extrapulmonary right to left shunting, and these infants are difficult to detect clinically.

Pulsed Doppler echocardiography in the diagnosis of pulmonary hypertension in COPD

We used pulsed Doppler echocardiography to examine the systolic ejection flow from the right ventricle in 66 patients with chronic obstructive pulmonary disease. Adequate recordings were obtained in 60 patients, in conjunction with right heart catheterization. Patients without pulmonary artery hypertension at rest (mean pulmonary artery pressure less than 20 mm Hg) underwent an exercise test which identified a group with PAH during exercise (MPAP greater than 30 mm Hg). The patients were divided into four groups: group 1, or control group: 17 healthy nonsmokers without normal respiratory function data; group 2: COPD without PAH (n = 12); group 3: PAH during exercise (n = 26); group 4: PAH at rest (n = 22). Analysis of Doppler data included time to peak velocity, right ventricular pre-ejection period, and ejection period. Pulsed Doppler echocardiography was a simple and reliable method of detecting PAH. Latent PAH, revealed by the exercise test, was accompanied by significant changes in Doppler findings, confirming the sensitivity of the method.

Comparison of several noninvasive methods for estimation of pulmonary artery pressure

Noninvasive estimation of pulmonary artery pressure is an important component of cardiac ultrasound studies. A number of methods are available for estimation of pulmonary pressure, each with varying degrees of reported accuracy. To assess feasibility and accuracy, noninvasive pulmonary artery pressure estimates were performed in infants and children at the time of catheterization. Patients were examined prospectively until there were 50 patients, in whom each of six methods for estimation of pulmonary pressure had been accomplished. All patients had tricuspid and pulmonary regurgitation of less than severe degree and no structural, flow, or electrocardiographic abnormality known to compromise the six methods. Systolic pressure was estimated by the Burstin method and also from peak tricuspid regurgitation velocity. Mean pressure was estimated by acceleration time divided by ejection time from waveforms obtained from the right ventricular outflow tract and main pulmonary artery. Diastolic pressure was estimated by systolic time intervals and from end-diastolic pulmonary regurgitation velocity. Noninvasive estimates were compared with simultaneous or nearly simultaneous catheterization measurements. For systolic pressure Burstin estimates were accomplished in 89% with high accuracy (r = 0.97). Tricuspid regurgitation velocities were recorded in 82%, also with high accuracy (r = 0.96). Waveforms for mean pressure estimation were recorded in 98% to 100% of patients. Those from the right ventricular outflow tract corresponded well with catheterization pressures (r = 0.94), whereas those recorded from the main pulmonary artery offered poor prediction of pulmonary pressure (r = 0.63). Systolic time interval measurements were accomplished in only 65% and did not correlate highly with catheterization (r = 0.84). Diastolic pressure estimates based on pulmonary regurgitation velocity were recorded in 98% of subjects with high accuracy (r = 0.96). Each method had advantages and disadvantages. The Burstin method was accurate but technically demanding and is reported to be limited by heart rate and significant right-sided regurgitation. Peak tricuspid velocities proved unexpectedly difficult to record in some patients but when successful, provided excellent prediction of pressure. Recording of waveforms for ratios of acceleration time to ejection time proved easy, but accuracy was high only for outflow tract waveforms. Peculiarities of main pulmonary artery flow may have led to poor accuracy for ratios measured from that site. For diastolic pressure estimation, systolic time interval records were the most difficult to obtain and did not provide useful accuracy. In contrast, pulmonary regurgitation velocities were easily obtained and provided high accuracy results. This is a selected pediatric series, evaluating methods in nearly ideal circumstances.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluation of the responsiveness of elevated pulmonary vascular resistance in children by Doppler echocardiography

Changes in the Doppler indexes, acceleration time (AcT), right ventricular ejection time (RVET), AcT/RVET ratio and pulmonary artery peak velocity were measured as were changes in pulmonary artery pressure and pulmonary vascular resistance in 21 children with pulmonary hypertension due to a large interventricular communication. In 11 children pulmonary vascular resistance was greater than 4.6 U/m2 (mean 8.6 +/- 1.6), whereas in 10 it was less than 4.5 U/m2 (mean 3.4 +/- 0.2). Although both groups demonstrated acceleration time and AcT/RVET values above normal, there were no significant differences in these values between the groups with high and low pulmonary vascular resistance. With administration of a pulmonary vasodilator pulmonary vascular resistance decreased in 11 responders by greater than 50% of baseline values (from 5.3 +/- 0.7 to 1.6 +/- 0.3 U/m2), whereas in the 10 nonresponders mean pulmonary vascular resistance decreased from 7.0 +/- 1.9 to 4.9 +/- 1.1 U/m2. There was no significant change in the Doppler indexes except for an increase in pulmonary artery peak velocity in the responders from 1.34 +/- 0.07 to 1.66 +/- 0.06 m/s (p less than 0.001). The results indicate that Doppler echocardiography cannot predict either the level of increased pulmonary vascular resistance or the degree of responsiveness sufficiently to obviate the need for cardiac catheterization in patients with interventricular communication and pulmonary hypertension.