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

Pulmonary artery acceleration time in young children is determined by heart rate and transpulmonary gradient but not by pulmonary blood flow: A simultaneous echocardiography-cardiac catheterization study

INTRODUCTION

Pulmonary artery acceleration time (PAAT) is considered useful for the non-invasive evaluation of pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR). PAAT is dependent on PAP, PVR, pulmonary artery compliance, stroke volume, and heart rate. Its relative dependency on these determinants may differ between young and older children, raising uncertainty regarding its utility in young children. We aim to identify the primary determinants of the PAAT in children less than 36 months undergoing cardiac catheterization and its utility for the diagnosis of elevated PVR.

METHODS

We prospectively studied 42 children undergoing cardiac catheterization and simultaneous echocardiography. We determined the correlations of PAAT to the above-mentioned determinants and evaluated receiver operator characteristic (ROC) curves for diagnosis of PVR indexed to body surface area (PVRi) ≥3 Wu*m² .

RESULTS

Median age was 11.5 (IQR 5.2, 21.2) months. Moderate correlations were found between PAAT and mean PAP (R = -.66, p < .001), PVRi (R = -.54, p = .004), pulmonary artery compliance (R = .65, p < .001), transpulmonary gradient (R = -.67, p < .001), stroke volume (R = .61, p = .002), and heart rate (R = -.63, p < .001). In multivariate regression modeling, only transpulmonary gradient and heart rate were independent determinants of PAAT. PAAT ≤77 msec had acceptable utility for diagnosing PVRi ≥ 3 Wu*m² (AUC .8 [.64, .95], n = 36), low sensitivity (59%), and excellent specificity (94%).

CONCLUSION

Transpulmonary gradient and heart rate, but not pulmonary blood flow, are important determinants of PAAT in children <36 months undergoing cardiac catheterization. PAAT has low sensitivity for diagnosing elevated PVRi, therefore, should not be solely relied upon in screening for elevated PVRi in young children.

Pulmonary Artery Acceleration Time Provides a Reliable Estimate of Invasive Pulmonary Hemodynamics in Children

BACKGROUND

Pulmonary artery acceleration time (PAAT) is a noninvasive method to assess pulmonary hemodynamics, but it lacks validity in children. The aim of this study was to evaluate the accuracy of Doppler echocardiography-derived PAAT in predicting right heart catheterization (RHC)-derived pulmonary artery pressure (PAP), pulmonary vascular resistance (PVR), and compliance in children.

METHODS

Prospectively acquired and retrospectively measured Doppler echocardiography-derived PAAT and RHC-derived systolic PAP, mean PAP (mPAP), indexed PVR (PVRi), and compliance were compared using regression analysis in a derivation cohort of 75 children (median age, 5.3 years; interquartile range, 1.3-12.6 years) with wide ranges of pulmonary hemodynamics. To account for heart rate variability, PAAT was adjusted for right ventricular ejection time and corrected by the RR interval. Regression equations incorporating PAAT and PAAT/right ventricular ejection time from the derivation cohort were then evaluated for the accuracy of their predictive values for invasive pulmonary hemodynamics in a validation cohort of 50 age- and weight-matched children with elevated PAP and PVR.

RESULTS

There were significant inverse correlations between PAAT and RHC-derived mPAP (r = -0.82) and PVRi (r = -0.78) and a direct correlation (r = 0.78) between PAAT and pulmonary compliance in the derivation cohort. For detection of pulmonary hypertension (PRVi > 3 Wood units · m² and mPAP > 25 mm Hg), PAAT < 90 msec and PAAT/right ventricular ejection time < 0.31 resulted in sensitivity of 97% and specificity of 95%. In the derivation cohort, the regression equations relating PAAT with mPAP and PVRi were mPAP = 48 - 0.28 × PAAT and PVRi = 9 - 0.07 × PAAT. These PAAT-integrated equations predicted RHC-measured pulmonary hemodynamics in the validation cohort with good correlations (r = 0.88 and r = 0.83, respectively), small biases (<10%), and minimal coefficients of variation (<8%).

CONCLUSIONS

PAAT inversely correlates with RHC-measured pulmonary hemodynamics and directly correlates with pulmonary arterial compliance in children. The study established PAAT-based regression equations in children to accurately predict RHC-derived PAP and PVR.

Accuracy of Doppler-derived indices in predicting pulmonary vascular resistance in children with pulmonary hypertension secondary to congenital heart disease with left-to-right shunting

This study aimed to evaluate the accuracy of Doppler echocardiography-derived indices in children with pulmonary hypertension secondary to congenital heart disease with left-to-right shunting. Doppler-derived indices including the acceleration time corrected (AcTc), deceleration time corrected, deceleration index, peak velocity, heart-rate-corrected inflection time (InTc), and a new index (the acceleration slope [Acc = peak flow velocity/AcTc]) were measured from the pulmonary artery (PA) systolic flow curve before and after 100 % oxygen administration in the main, left, and right PAs of 33 children. The acquired data were compared between low and high pulmonary vascular resistance (PVR) groups and between responders and nonresponders to the vasoreactivity test. The AcTc values differed significantly between the low and high PVR groups before and after oxygen administration in the main (P = 0.032 and <0.001, respectively), right (P = 0.011 and <0.001, respectively), and left (P < 0.001 and <0.001, respectively) PAs. The AcTc cutoff point in the main PA was 3.44 before oxygen administration (81% sensitivity and 91% specificity). The InTc in the main PA and its changes differed significantly between the low and high PVR groups before and after oxygen administration and between the responders and nonresponders (P = 0.016, 0.046, and 0.021, respectively). The velocity changes of the PA in the main PA differed significantly between the responders and nonresponders to oxygen administration (P < 0.001). The Acc and its changes differed significantly between the low and high PVR groups after oxygen administration and between the responders and nonresponders to oxygen administration (P = 0.044 and 0.006, respectively). Doppler echocardiographic examination using PA systolic flow indices in addition to PA reactivity testing is a promising technique for assessing PVR in children with congenital heart disease.

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.

Quantitative evaluation of right ventricle function by transthoracic echocardiography in childhood congenital heart disease patients with pulmonary hypertension

INTRODUCTION AND OBJECTIVE

The present study aims to quantitatively evaluate the right ventricle (RV) function by means of transthoracic echocardiography in normal children and childhood congenital heart disease patients with pulmonary hypertension.

PATIENTS AND METHODS

This study was conducted in a cohort including 40 healthy children and 30 pediatric patients with pulmonary hypertension who were diagnosed under close surveillance at the study center between October 2009 and November 2010.

RESULTS

Statistically significant differences were found between the patient and control groups for the right ventricle myocardial performance index (RVMPI), the left ventricle myocardial performance index (LVMPI), the tricuspid valve systolic flow velocity (Ts), the ratio of systolic pulmonary artery pressure to the right ventricle outflow tract systolic flow velocity time integral (sPAP/RVOT VTI), and the ratio of systolic pulmonary artery pressure to right ventricle outflow tract systolic flow velocity time integral × heart rate (sPAP/[RVOT VTI×HR]). When the children were divided into three groups based on their pulmonary vascular resistance significant differences emerged that predicted an increasing severity of RV dysfunction. Significant differences were also observed for the RVMPI, the LVMPI, and the Ts as well as for echocardiographic pulmonary flow (Qp) and systemic flow (Qs).

DISCUSSION

The present study demonstrates that echocardiographic parameters can be used for the quantitative detection of RV dysfunction in childhood congenital heart disease patients with high pulmonary artery pressure (systolic, diastolic, and mean) or pulmonary vascular resistance.

Quantitative assessment of pulmonary vascular resistance and reactivity in children with pulmonary hypertension due to congenital heart disease using a noninvasive method: new Doppler-derived indexes

We assessed the usefulness of transthoracic Doppler-derived indexes obtained in the proximal pulmonary artery (PA) branch for estimating pulmonary vascular resistance (PVR) in 45 children with congenital heart disease (CHD) and 23 normal control subjects. The acceleration time, inflection time (InT), deceleration index, and peak velocity, which were measured from the systolic PA flow velocity curve obtained at the sites of the main PA, and right and left PA, were compared with the PVR in patients with CHD. In addition, changes in either Doppler-derived indexes or PVR during 100% oxygen administration were compared in 22 patients showing a baseline PVR >or=4.6 U/m(2) (high PVR). The heart-rate-corrected InT (InTc) values obtained in the left PA in the high PVR group were significantly lower than those in the main PA (4.7 +/- 1.5 vs. 7.5 +/- 3.0; p < 0.001). The InTc obtained from the left PA separated patients with high and low PVR (4.7 +/- 1.4 vs. 9.9 +/- 2.4; p < 0.001) and no significant differences in InTc were found between the low PVR and the control groups. An increase in InTc to >6 during 100% oxygen administration for the high PVR group indicated good PA reactivity with a sensitivity of 93%, specificity of 100%, and agreement of 95% (kappa = 0.83). Moreover, this InTc index correlated inversely with PVR (r = -0.80). In conclusion, our method can noninvasively separate high and low PVR and assess the PA reactivity for high PVR in children with CHD.

Clinical utility of echocardiography for the diagnosis and management of pulmonary vascular disease in young children with chronic lung disease

OBJECTIVE

The goal was to determine the clinical utility of Doppler echocardiography in predicting the presence and severity of pulmonary hypertension in patients with chronic lung disease who subsequently underwent cardiac catheterization.

METHODS

A retrospective review of data for all patients < 2 years of age with a diagnosis of bronchopulmonary dysplasia, congenital diaphragmatic hernia, or lung hypoplasia who underwent echocardiography and subsequently underwent cardiac catheterization for evaluation of pulmonary hypertension was performed. The accuracy of echocardiography in diagnosing pulmonary hypertension, on the basis of estimated systolic pulmonary artery pressure, was compared with the detection of pulmonary hypertension with the standard method of cardiac catheterization.

RESULTS

Thirty-one linked measurements for 25 children were analyzed. Systolic pulmonary artery pressure could be estimated in 61% of studies, but there was poor correlation between echocardiography and cardiac catheterization measures of systolic pulmonary artery pressure in these infants. Compared with cardiac catheterization measurements, echocardiographic estimates of systolic pulmonary artery pressure diagnosed correctly the presence or absence of pulmonary hypertension in 79% of the studies in which systolic pulmonary artery pressure was estimated but determined the severity of pulmonary hypertension (severe pulmonary hypertension was defined as pulmonary/systemic pressure ratio of > or = 0.67) correctly in only 47% of those studies. Seven (58%) of 12 children without estimated systolic pulmonary artery pressure demonstrated pulmonary hypertension during subsequent cardiac catheterization. In the absence of estimated systolic pulmonary artery pressure, qualitative echocardiographic findings, either alone or in combination, had worse predictive value for the diagnosis of pulmonary hypertension.

CONCLUSION

As used in clinical practice, echocardiography often identifies pulmonary hypertension in young children with chronic lung disease; however, estimates of systolic pulmonary artery pressure were not obtained consistently and were not reliable for determining the severity of pulmonary hypertension.

Noninvasive Assessment of Pulmonary Arterial Capacitance by Echocardiography

BACKGROUND

Pulmonary arterial capacitance (PAC) has been associated with right ventricular (RV) workload and mortality in pulmonary hypertension, but is not routinely evaluated in children. We investigated whether PAC can be estimated noninvasively by echocardiography.

METHODS

We retrospectively determined PAC in 31 children with pulmonary hypertension, using echocardiography, and compared the results with those obtained at cardiac catheterization.

RESULTS

PAC derived from echocardiography was similar to that derived from catheterization (mean +/- SD 1.16 +/- 1.0 vs 1.10 +/- 0.95 mL(3) x mm Hg(-1), P = not significant) and the two correlated well (r = 0.74, P < .0001). There was a highly significant polynomial relationship between PAC and RV anterior wall thickness indexed to body surface area (R(2) = 0.54, P < .0001), but not between pulmonary vascular resistance and RV wall thickness. Pulmonary vascular resistance and PAC did not correlate.

CONCLUSIONS

Echocardiography can reliably estimate PAC, which strongly correlates with RV hypertrophy, a surrogate for RV work.

Screening, early detection, and diagnosis of pulmonary arterial hypertension: ACCP evidence-based clinical practice guidelines

Pulmonary arterial hypertension (PAH) occurs as an idiopathic process or as a component of a variety of disease processes, including chronic thromboembolic disease, connective tissue diseases, congenital heart disease, and exposure to exogenous factors including appetite suppressants or infectious agents such as HIV. This article reviews evidence for screening in susceptible patient groups and the approach to diagnosing PAH when it is suspected, and provides specific recommendations for applying this evidence to clinical practice.

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

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

Clinical importance of AaDO2 and pulmonary artery pressure as predicted by pulsed Doppler echocardiography at bedside in diagnosing pulmonary embolism

The authors evaluated clinical importance of alveolar-arterial PO2 difference (AaDO2) and pulmonary artery pressure (PAP) estimated by pulsed Doppler echocardiography in 31 patients with pulmonary embolism (PE). Echocardiographic estimates from flow velocity patterns in the right ventricular outflow tract showed significant correlation with actual measurements obtained by right cardiac catheterization. Furthermore, PAP as obtained by pulsed echocardiography was significantly higher in acute massive and recurrent multiple groups in comparison with the acute submassive group. AaDO2 was greatest in the acute massive group, followed by the recurrent multiple group, and then by the acute submassive group. These results suggest that analyses of AaDO2 and the echocardiographic estimation of PAP at bedside are successful in the diagnosis and classification of PE.

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 wedge angiography for prediction of pulmonary vascular disease in Down syndrome

We performed high resolution pulmonary wedge angiography (PWA) and conventional hemodynamics to predict the reversibility of structural pulmonary vascular disease. Sixty-one pulmonary wedge angiograms were performed on 41 patients with intracardiac shunts and Down syndrome (median age 8 months). Balloon occlusion wedge angiograms were analyzed for (1) monopedial branches from the distal 10 mm of muscular arteries, (2) capillary blush, (3) tapering indices, and (4) tortuosity. Twenty-five patients had open lung biopsy, graded by the Health Edwards classification, and analyzed morphometrically. Pulmonary vascular resistance of > or = 6 units was 100% sensitive and 94% specific for Heath Edwards Grade III-IV. A monopedial count < 3 vessels was 83% sensitive and 100% specific for Heath Edwards Grade III-IV. Abnormal capillary blush was 83% sensitive and 69% specific for Heath Edwards Grade III-IV. Tapering indices and tortuosity showed no significant correlation with lung biopsy. A combination of pulmonary vascular resistance < 6 units, monopedial count > or = 3, and normal capillary blush was 100% sensitive and specific for Heath Edwards Grade 0-II, and a combination of pulmonary vascular resistance > or = 6 units, monopedial count < 3, and abnormal capillary blush was 100% sensitive and specific for Heath Edwards Grade III-IV. Using the 3 criteria, Heath Edwards Grade was accurately predicted in 17 patients. In 4 patients, only 2 criteria were available. Morphometric analysis showed an inverse relationship between the lowest monopedial count and the number of occlusive vessels per cm of tissue, r = -0.74 p < 0.001. Arteries showing intimal and/or medial thickening causing > 90% luminal narrowing were scored as "occlusive." These results show that when the hemodynamic and pulmonary wedge angiography data are concordant, the structural changes of pulmonary vascular disease can be accurately predicted and lung biopsy may be avoided.

The neonatal transitional circulation: a combined noninvasive assessment

Dramatic changes occur in the circulation of the newborn during the transition from fetal to neonatal life. Closure of the foramen ovale and ductus arteriosus, decrease in pulmonary vascular resistance, and improvement in right ventricular compliance are among these changes. These physiological-anatomical events were characterized by means of two-dimensional, Doppler and color flow echocardiography. Forty-five full-term infants (22 male, 23 female) were studied at a mean age of 4.2 hours (T1), 25.5 hours (T2), 49.8 hours (T3), and 73.8 hours (T4) by two-dimensional, Doppler and color flow echocardiography. At T1, T2, T3, and T4, the ductus arteriosus was patent by color flow echocardiography in 100%, 34%, 22%, and 11%, respectively. Conversely, patency of the ductus by Doppler alone was detected in 100% (T1), 13% (T2, T3), and 11% (T4). Reversal of flow in the descending aorta, reflective of diastolic ductal filling, was not sensitive in detecting ductal patency (T1 50%, T2 3%, T3 and T4 0%). The patency of the foramen ovale was noted to decrease over the course of the study. Right ventricular compliance was quantitatively assessed by pulsed-Doppler diastolic properties (E-to-A ratio). This changed significantly from T1 to T4 (0.90 to 0.97) reflecting improving compliance of the right ventricle. The ratio of acceleration to ejection time, a Doppler estimation measure of pulmonary vascular resistance, increased from 0.28 to 0.33 (T1 to T4) reflecting a decrease in pulmonary vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Responsiveness of raised pulmonary vascular resistance to oxygen assessed by pulsed Doppler echocardiography

OBJECTIVE

To assess whether changes in Doppler echocardiographic indices in the pulmonary artery correlated with changes in pulmonary vascular resistance.

DESIGN

Acceleration time, ejection time, maximal flow velocity, and velocity time integrals were measured at the same time as pressure and oxygen saturation measurements in room air and during 10 minutes of oxygen breathing in the catheterisation laboratory. Pulmonary vascular resistance and pulmonary blood flow (Qp) were calculated from catheterisation data by use of the Fick principle.

PATIENTS

14 consecutive patients with a congenital heart defect and a left to right shunt associated with raised pulmonary artery pressure who underwent routine diagnostic cardiac catheterisation to assess their pulmonary vascular resistance.

RESULTS

Though pulmonary vascular resistance and systolic pulmonary artery pressure fell significantly during oxygen administration, there was no significant change in the acceleration time or ejection time. Peak velocity increased significantly during oxygen administration. During oxygen breathing Doppler derived measurements of pulmonary flow showed a significant increase in Qp similar to the increase in Qp measured by the Fick principle. There was no significant correlation between the fall in pulmonary vascular resistance and the increase in acceleration time or ejection time, increase in peak velocity, increase in pulmonary artery diameter, or increase in Doppler derived pulmonary blood flow.

CONCLUSIONS

Measurements of acceleration and ejection time by Doppler echocardiography did not predict the response of pulmonary artery pressure and resistance to oxygen. Though changes in maximal flow velocity across the pulmonary artery and in Doppler derived pulmonary blood flow measurements became significant during oxygen breathing, the correlation of these changes with fall in pulmonary vascular resistance was poor.

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.

Echo/Doppler and hemodynamic correlates of vasodilator responsiveness in primary pulmonary hypertension

To determine correlates of acute vasodilator responsiveness in primary pulmonary hypertension, we retrospectively studied 25 patients, comparing 41 resting echo/Doppler and nine resting catheterization variables with the maximal reduction in pulmonary vascular resistance achieved during vasodilator trials. Twelve vasodilators were tested (mean, 5.6 drugs per patient; range, three to eight). Eight patients were vasodilator responsive, as defined by a reduction in pulmonary vascular resistance greater than or equal to 30 percent in response to at least one agent. Univariate and multivariate analyses revealed only Doppler pulmonic peak flow velocity to be an independent correlate of responsiveness (p less than 0.05). Responders differed from nonresponders in having a higher Doppler pulmonic peak flow velocity (PV) (SD 81 +/- 24 vs 64 +/- 15 cm/s; p = 0.05), lower mean right atrial pressure (RAP) (6 +/- 4 vs 13 +/- 7 mm Hg; p = 0.04), and longer median survival (37 vs 5 months; p = 0.03). Seven of eight responders had RAP less than or equal to 10 mm Hg, and all responders had PV greater than 60 cm/s. Seven of ten patients with both RAP less than or equal to 10 and PV greater than 60 and one of the 15 remaining patients were vasodilator responsive (p less than 0.001). Thus, echo/Doppler and invasive hemodynamic parameters correlate with acute vasodilator responsiveness in primary pulmonary hypertension. Patients with low PV and high RAP values were almost never vasodilator responsive. Doppler pulmonic peak velocity and mean RAP may be useful in identifying patients most likely to respond to acute vasodilator trials and those in whom testing is unlikely to yield positive results.

Doppler estimation of changes in pulmonary artery pressure during hypoxic breathing

To assess the use of Doppler echocardiographic screening for abnormal pulmonary vasoreactivity, we measured pulmonary artery pressure in 10 adult patients and 11 normal subjects while recording Doppler right ventricular outflow acceleration time, pre-ejection period, and ejection time. In the normal subjects we also measured the changes in each parameter after 10 minutes of hypoxic breathing (FIO2 = 0.12). Mean pulmonary artery pressure increased by 39% during hypoxia (13 +/- 4.3 to 18 +/- 5.4 mm Hg). In the patients and normal subjects at rest, mean pulmonary artery-pressure correlated well with acceleration time (r = -0.84; standard error of the estimate, 6.6 mm Hg; p = 0.0001). Over the narrow range of mean pulmonary artery pressure in normal subjects at rest, mean pulmonary artery pressure did not correlate well with acceleration time, acceleration time/pre-ejection period, or acceleration time/right ventricular ejection time. However, changes in mean pulmonary artery pressure induced by hypoxic breathing did correlate with changes in acceleration time/right ventricular ejection time (r = 0.73; standard error of the estimate, 2.3 mm Hg; p = 0.01). Doppler ultrasound may offer a noninvasive means for detecting abnormal pulmonary vasoreactivity in asymptomatic individuals at risk for developing pulmonary hypertension.

Imaging congenital heart disease

When defined in a broad sense, imaging is the most important aspect of modern pediatric cardiovascular medicine. Definition of anatomic defects is now accurately and easily obtained with physical inspection, x-ray technology (including roentgenology, fluoroscopy, and cineangiography), and echocardiography. Echocardiography, with the addition of Doppler and color flow Doppler, is the most important development in clinical cardiac imaging in the past decade. The exciting new areas of "imaging" are in cardiac functional analysis and metabolic evaluation. Viewing the heart at the cellular or biochemical level is the challenge of the future. The new technology offered by computed tomography, positron emission tomography, and nuclear magnetic resonance imaging begins to provide the ability to image the domain of cellular and biochemical function.