Noninvasive estimation of pulmonary artery pressure

Utility of Pulmonary Artery Acceleration Time to Estimate Systolic Pulmonary Artery Pressure in Neonates and Young Infants

Transthoracic echocardiogram (TTE) is commonly used to screen for pulmonary hypertension (PHTN) in neonates and young infants. However, in the absence of sufficient tricuspid regurgitation (TR), a ventricular septal defect (VSD), or a patent ductus arteriosus (PDA), the estimation of systolic pulmonary artery pressure (SPAP) becomes challenging. Pulmonary artery acceleration time (PAAT) is an alternate parameter that is easy to obtain in almost all patients and does not require the presence of tricuspid valvar regurgitation or an anatomical cardiac defect. We sought to examine the correlation of PAAT with estimated SPAP by TTE and create an equation to estimate the SPAP using PAAT. We performed a retrospective review of TTEs performed on neonates and young infants (4 months of age or younger) at our institution between April 2017 and December 2018, along with the corresponding medical records. We included TTEs that provided estimation for SPAP and at least one PAAT measurement. During the study period, 138 TTEs performed on 82 patients met the inclusion criteria. Strong correlation was delineated between PAAT and SPAP estimated by the maximum velocity of tricuspid valve regurgitation Doppler, correlation coefficient (r) = - 0.83. Moderate correlation was detected between PAAT and SPAP estimated by PDA Doppler, r = - 0.66. Utilizing the following equation "SPAP = 82.6 - 0.58 × PAAT + RA mean pressure", PAAT can be used to estimate SPAP in neonates and young infants. PAAT can be used as an alternative to TR jet to assess SPAP when the latter is absent or insufficient. Further studies are needed to verify the accuracy of this equation.

Non-invasive estimation of pulmonary vascular resistance in patients of pulmonary hypertension in congenital heart disease with unobstructed pulmonary flow

Context:

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 accompanied by pulmonary arterial hypertension.

Aim:

The present study was planned to evaluate non-invasive echocardiographic parameters to assess pulmonary vascular resistance.

Settings and Design:

This prospective observational study included 44 patients admitted in the cardiology and pediatric cardiology ward of our institution for diagnostic or pre-operative catheter based evaluation of pulmonary arterial pressure and PVR.

Materials and Methods:

Detailed echocardiographic evaluation was carried out including tricuspid regurgitation velocity (TRV) and velocity time integral of the right-ventricular outflow tract (VTI_RVOT). These parameters were correlated with catheter-based measurements of PVR.

Results:

The TRV/VTI_RVOT ratio correlated well with PVR measured at catheterization (PVRcath) (r = 0.896, 95% confidence interval [CI] 0.816 to 0.9423, P < 0.001). Using the Bland-Altman analysis, PVR measurements derived from Doppler data showed satisfactory limits of agreement with catheterization estimated PVR. For a PVR of 6 Wood units (WU), a TRV/VTI_RVOT value of 0.14 provided a sensitivity of 96.67% and a specificity of 92.86% (area under the curve 0.963, 95% confidence interval 0.858 to 0.997) and for PVR of 8 WU a TRV/VTI_RVOT value of 0.17 provided a sensitivity of 79.17% and a specificity of 95% (area under the curve 0. 0.923, 95% confidence interval 0.801 to 0.982).

Conclusions:

Doppler-derived ratio of TRV/VTI_RVOT is a simple, non-invasive index, which can be used to estimate PVR.

CT scanning in the evaluation of pulmonary hypertension

BACKGROUND

Right-heart catheterization is currently the gold standard method for detecting pulmonary hypertension (PH) and grading its severity. Our study determined the utility of computerized tomography (CT) scans for detecting PH in patients with left-sided heart disease, thereby potentially avoiding the overuse of invasive right-heart catheterization.

METHODS

A retrospective review was conducted on 40 patients with left-sided cardiac pathology who had undergone both right-heart catheterization and CT scanning of the chest. Mean pulmonary artery diameters (MPADs) were measured on CT scans and compared with pulmonary artery pressures measured by right-heart catheterization.

RESULTS

Patients with mild-to-moderate PH had significantly greater CT-measured MPADs (34.89 ± 1.01) than patients without PH (controls) (27.36 ± 0.83, p < 0.001). Patients with severe PH had significantly greater MPADs (38.31 ± 0.88) than both mild-to-moderate PH patients (p < 0.01) and controls (p < 0.001). Receiver operating characteristic curve analysis showed that CT scanning predicted PH with an area under the curve of 0.95 (p < 0.0001). A cutoff MPAD of >33.3 mm had 100% specificity and 100% positive predictive value (N = 40, p < 0.0001), and a cutoff MPAD of <27.3 mm had 100% sensitivity with 100% negative predictive value (N = 40, p < 0.001).

CONCLUSIONS

CT scanning correctly identified all patients with PH with MPADs >34 mm and excluded all patients without PH when MPADs were <27 mm. We advocate that the measurement of MPAD by CT scanning can be quickly and easily performed by the clinician to screen for the presence of PH.

Helical computer assisted tomography in pulmonary hypertension complicating left-to-right shunts--correlation with pulmonary hemodynamics

The present study analyzed the helical computer-assisted tomography (CAT) findings in 30 patients with pulmonary hypertension (PH) associated with left-to-right shunts; specifically, ventricular septal defect, 23; atrioventricular septal defect, 6; patent ductus arteriosus, 1. Eight patients had 21 trisomy. Age ranged from 1 to 18 (mean, 4.1) months, and body weight ranged from 2.6 to 10.7 (mean, 4.9) kg. In all patients, the chest CAT revealed patchy areas of high and low attenuation (mosaic pattern) and regional atelectasis in the lung fields. The volume of low attenuated lesions and of atelectasis, and the total lung volume were derived from integration of areas measured on the CAT image. The ratios of low attenuated lesion/total lung volume (Lo), volume of atelectasis/ total lung volume (Ate) and low attenuated lesion and volume of atelectasis/total lung volume (Lo&Ate) were compared with hemodynamic parameters measured at cardiac catheterization. The pulmonary to systemic resistance ratio correlated with Lo (r=0.61, p<0.01) and Lo&Ate (r=0.69, p<0.01), whereas the pulmonary vascular resistance correlated with Ate (r=0.53, p<0.01). Lo, Ate and Lo&Ate in the chest CAT are reliable parameters that can be used to estimate pulmonary vascular resistance in patients with PH associated with left-to-right shunts.

Changes in pulmonary arterial pressure in preterm infants with chronic lung disease

BACKGROUND

Pulmonary arterial pressure (PAP) is raised in preterm infants with respiratory distress syndrome who subsequently develop chronic lung disease. The natural history of pulmonary hypertension in infants with chronic lung disease is unknown.

OBJECTIVES

To investigate changes in PAP, assessed non-invasively using Doppler echocardiography, in infants with chronic lung disease during the 1st year of life.

METHODS

Serial examinations were performed in infants with chronic lung disease and healthy preterm infants. The Doppler derived acceleration time to right ventricular ejection time ratio (AT/RVET) was calculated from measurements made from the pulmonary artery velocity waveform.

RESULTS

A total of 248 examinations were performed in 54 infants with chronic lung disease and 44 healthy preterm infants. The median AT/RVET was significantly lower in infants with chronic lung disease than in healthy preterm infants (0.31 v 0.37). AT/RVET significantly correlated with age corrected for prematurity in both infants with chronic lung disease (r = 0.67) and healthy infants (r = 0.55). There was no significant difference between the rate of change in AT/RVET between the two groups. In infants with chronic lung disease, multivariate analysis showed that AT/RVET was significantly independently associated with age and inversely with duration of supplemental oxygen treatment. Median AT/RVET was significantly lower in infants with chronic lung disease until 40-52 weeks of age corrected for prematurity.

CONCLUSIONS

Although PAP falls with increasing age in both infants with chronic lung disease and healthy preterm infants, it remains persistently raised in infants with chronic lung disease until the end of the 1st year of life.

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.

Utility of CT scan evaluation for predicting pulmonary hypertension in patients with parenchymal lung disease. Medical College of Wisconsin Lung Transplant Group

OBJECTIVE

To determine the utility of CT-determined main pulmonary artery diameter (MPAD) for predicting pulmonary hypertension (PH) in patients with parenchymal lung disease.

DESIGN

Retrospective review of right-heart hemodynamic data and chest CT scans in 45 patients.

SETTING

Tertiary-referral teaching hospital and VA hospital.

PATIENTS

Between October 1990 and December 1995, 36 patients referred for evaluation of parenchymal lung disease or possible pulmonary vascular disease were found to have PH, as defined by mean pulmonary artery pressure (mPAP) > or =20 mm Hg. Nine control patients (mPAP <20 mm Hg) were also identified (4 from hospital records search, 5 after evaluation for possible PH).

RESULTS

CT-determined MPAD was 35+/-6 mm in patients with PH and 27+/-2 mm in control subjects. In our group of patients, MPAD > or =29 mm had a sensitivity of 87%, specificity of 89%, positive predictive value (PPV) of 0.97, and positive likelihood ratio (LR) of 7.91 for predicting PH; in the subgroup of patients with parenchymal lung disease (n=28, PH and control subjects), MPAD > or =29 mm had a sensitivity of 84%, specificity of 75%, PPV of 0.95, and positive LR of 3.36 for predicting PH. The most specific findings for the presence of PH were both MPAD > or =29 mm and segmental artery-to-bronchus ratio > 1:1 in three or four lobes (specificity, 100%). There was no linear correlation between the degree of PH and MPAD (r=0.124).

CONCLUSIONS

CT-determined MPAD has excellent diagnostic value for detection of PH in patients with advanced lung disease. Therefore, standard chest CT scans can be used to screen for PH as a cause of exertional limitation in patients with parenchymal lung disease. Because CT is commonly used to evaluate parenchymal lung disease, this information is readily available.

Changes in oxygenation and pulmonary haemodynamics in preterm infants treated with inhaled nitric oxide

AIM

To investigate changes in various cardiorespiratory variables with inhaled nitric oxide (NO), as part of a randomised controlled trial.

METHODS

Infants were treated with inhaled NO for 72 hours. Changes in oxygenation were assessed using the oxygenation index (OI). Serial changes in pulmonary artery pressure (PAP) were assessed using the Doppler derived acceleration time to right ventricular ejection time ratio (AT:RVET). Doppler measurements of right ventricular output, pulmonary blood flow, and systolic PAP was performed in a subset of infants.

RESULTS

Twenty infants received inhaled NO and 22 acted as controls. Infants were treated at a median dose of 5 (range 5 to 20) ppm. There was a fall in median OI by 17% in treated infants within 30 minutes of treatment. The fall in OI in treated infants was significantly different from the response in controls until 96 hours. Infants treated with inhaled NO showed a rapid response with a median rise in AT:RVET of 0.04 (range -0.06 to 0.12) within 30 minutes. The change in AT:RVET was significantly different from controls until 4 hours. Median systolic PAP also fell in treated infants by 6.1 (range -14.4 to -4.4) mm Hg within 1 hour. Changes in OI were significantly associated with changes in PBF (r = 0.44), but not with changes in AT:RVET.

CONCLUSION

Treatment with inhaled NO rapidly improves oxygenation and lowers PAP in preterm infants. However, these effects are transient and treatment does not influence long term outcome.

Acute right heart failure due to adenotonsillar hypertrophy

A case is presented in which a child with underlying chronic lung disease, developed cor pulmonale and severe pulmonary hypertension as a result of adenotonsillar hypertrophy. His cardiac function acutely decompensated with an upper respiratory infection which exacerbated his obstructive sleep symptoms. Pre and postoperative documentation of cardiopulmonary function was critical in the peri-operative management of this patient. His severe pulmonary hypertension was stabilized using a nasopharyngeal airway and medications pre-operatively, in order to minimize his risk of anesthesia. He continued to require careful monitoring and manipulation of his medications after adenotonsillectomy and bronchoscopy. Serial echocardiograms documented the effects of the various interventions implemented in this patient. Severe acute right heart failure is an unusual complication of obstructive sleep apnea. However, this may become more common as more children survive prematurity and its associated chronic lung disease. These children may have subclinical lung disease and/or chronic pulmonary hypertension even after they no longer require supplemental oxygen and bronchodilators. Because these children are often tenuous, with regard to their cardiopulmonary function, they may be at increased risk to develop significant complications related to obstructive sleep apnea. It is important that a physician familiar with the management of pulmonary hypertension be involved in the care of these patients.

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.

Lung mechanics in infants with left-to-right shunt congenital heart disease

To clarify which hemodynamic measurement correlates best with lung mechanics in infants with congenital heart disease and left-to-right shunts, dynamic pulmonary function tests and echocardiography were performed in 26 infants with such disease (study infants) and in 37 normal, healthy infants (control infants). The tidal volume and pulmonary compliance (CL) were lower and airway resistance higher in infants with congenital heart disease than in control infants. A significant correlation was demonstrated between CL, expiratory resistance (Re), and the right pulmonary artery-to-aortic size ratio (RPA/DAO). CL and Re also correlated well with the corrected acceleration time square root of RR ratio (ACT/square root of RR: ACT, acceleration time and RR: length of the cardiac cycle) of pulmonary flow velocity. Stepwise multiple regression analysis revealed that RPA/DAO correlated best with both CL and Re. It is concluded that infants with congenital heart disease and left-to-right shunts have lower lung compliance and higher expiratory airway resistance than normal children, and that RPA/DAO is the echocardiographic parameter that correlates best with the changes in lung mechanics.

Doppler echocardiographic assessment of pulmonary circulation in severe respiratory failure of the neonate: an aid for extracorporeal lung support indications

Extracorporeal lung support (ECLS) for newborns with acute respiratory failure has achieved increased popularity over the last decade. However, precise criteria for its implementation remain controversial. The aim of this study was to assess the value of Doppler echocardiography (DE) in 31 neonates with PaO2 of < or = 50 mmHg, FIO2 of 1, and optimal ventilation. Treatment included mechanical ventilation, paralysis, volume loading, vasopressors, and tolazoline. Markers indicative of ECLS (failure of maximal medical therapy, assessed by AaDO2 of more than 610 mm Hg beyond 8 hours and/or an oxygenation index (OI = mean airway pressure x FIO2%/postductal PaO2) of more than 40 beyond 4 to 6 hours) were present in 23 (group 1) and absent in eight (group 2). Shunt direction and systolic pulmonary arterial pressure (sPAP) calculated from tricuspid insufficiency velocity were assessed using DE. At the time of admission, sPAP was significantly higher in group 1 (62.1 v 43.7 mm Hg). On day 1, group 1 differed from group 2 in maximum sPAP value (73.2 v 44.4 mm Hg), PaCO2 (56.1 v 40 mm Hg), right-to-left shunting (85% v 25% of the patients), and pulmonary-to-systemic-pressure systolic ratio (sPAP:sSAP) (1.29 v 0.75). Patients with an sPAP:sSAP ratio of more than 1 and patients with high sPAP associated with high PaCO2 on day 1, all later (average, 10 hours later) fulfilled ECLS criteria; this suggests that DE assessment of pulmonary circulation may yield early and predictive markers of impending ECLS indication. Further confirmation of these results would help avoid unnecessary delays in ECLS implementation in newborns with severe respiratory failure.