Role of Pulmonary Artery Acceleration Time in Detecting Pulmonary Hypertension and It’s Severity

Rafid Bashir Hashim Al-Taweel
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Keywords : pulmonary artery acceleration time, estimated pulmonary artery systolic pressure, pulmonary hypertension.
Medical Journal of Babylon  13:4 , 2017 doi:1812-156X-13-4
Published :16 July 2017

Abstract

Transthoracic echocardiography with Doppler study is recommended as the initial noninvasive test in the screening, evaluation & monitoring of pulmonary hypertension by estimating pulmonary artery systolic pressure by measuring PA acceleration time which can estimate pressure severity. The aim of this study is to estimate the validity of pulmonary artery acceleration time as an parameter for evaluation and measuring pulmonary artery systolic pressure . This study: A cross sectional study has been carried out from December 2015 to May 2016 in El-Imamein Al-Kadhimain teaching hospital at echocardiography 61 patients (both normal &abnormal pulmonary pressure). Patients at first were assessed for presence of TR to include in the study& both estimated systolic & mean pulmonary pressure were assessed by both TR derived Doppler assessment & then measuring PAAT & PAAT derived pulmonary pressure with comparison between them .It was shownIn this studythat61patients were involved regardless of pulmonary pressure,with mean age of 55.1±17.6 (range 18-85 yr), 18 were male (29.5%) & 43 were females (70.5%). The mean of estimated peak systolic pulmonary artery pressure(EPSPAP) & mean pulmonary arterial pressure (MPAP) derived from tricuspid regurgitation done was 44.9±20.2 mmHg& 32.1±14.2 respectively. The mean value of pulmonary artery acceleration time (PAAT)was 106.89± 27.5ms& mean of PAAT derived MPAP was 30.9 ± 12.35 mmHg .The correlation of pulmonary artery acceleration time (PAAT) to pulmonary systolic pressure shows a significant association (r= - 0.693)(p=0.001) & the correlation of PAAT derived MPAP to TR derived MPAP showed significant correlation P<0.001.The sensitivity and specificity of pulmonary acceleration time in detection of pulmonary hypertension (using the value of 100ms as a cut off value) found sensitivity of 100% and specificity of 63.1%. PAAT was more useful in detecting moderate & severe pulmonary hypertension P<0.001.conclusion:Pulmonary artery acceleration time is a noninvasive obtainable echocardiographic parameter well correlated with measures of pulmonary artery systolic &mean pressure derived by tricuspid regurgitation .

Introduction

Pulmonary hypertension (PH) is a hemodynamic and pathophysiologic state defined as a raised in mean pulmonary artery pressure(MPAP) of 25 mm Hg at rest as measured by right-heart catheterization (RHC)It can be found in many clinical conditions with distinct pathogenetic and clinical features, such as pulmonary arterial hypertension (PAH) and left-heart, lung, and thromboembolic diseases [1,2] Five categories of disorders that cause PH were seen: pulmonary arterial hypertension (Group 1); pulmonary hypertension due to left heart disease (Group 2); pulmonary hypertension due to chronic disease of the lungs and/or hypoxia (Group 3); chronic thromboembolic pulmonary hypertension (Group 4); and pulmonary hypertension due to unclear multifactorial causes (Group 5) as state in updated clinical classification of pulmonary hypertension in 2013[3]. Given the subtle symptoms and physical signs, particularly in the early stages, a high index of suspicion is mandatory to diagnose the disease before irreversible pathophysiologic changes happened. In this regard, cardiac echocardiography, by providing directand/or indirect evidences of elevated pulmonary artery pressure (PAP), is a very excellent noninvasive screening test for those patients with symptoms orrisk factors for PH, such as connective tissue disease, anorexigen drugs user, pulmonary embolism, heart failure, and heart diseases. It may alsovital key information on both the etiology and the prognosis of PH[4,6]. measurement of pulmonary artery pressure by using transthoracicechocardiography (TTE) are most commonly done by usingcontinuous-wave Doppler to record the maximum velocity of tricuspid regurgitation (TRVmax). This technique of pulmonary arterypressure quantification has been widely accepted for clinical and researchaims because it provides a non-invasive, direct measureof right ventricular (RV) systolic pressure (RVSP) that correlates closely with invasive hemodynamic estimation.[7].In the absence of significant RVout flow tract obstruction, this way providesA good means of obtaining estimatedEPSPAP. However, this method of pulmonary arterypressure assessment is not possible when TR is absent or non-significant.Alternative transthoracic echocardiographic methods for pulmonary artery pressure estimation also have been used. These includethe measurement of blood flow through an anatomic defect (ventricularseptal defect,[8,9] patent ductusarteriosus,[10] or aorto-pulmonaryshun [11], estimation of the peak systolic and end-diastolic pulmonicvalve regurgitant velocity[12] and measurement of the pulmonary arteryacceleration time (PAAT)by Pulsed-wave Doppler interrogation of the RVoutflow tract often which reveals an acceleration time of <100 msec, that reflects abnormal MPAP[13-16].

Materials and methods

A61 patients were enrolled in this cross-sectional study, all  patientswere involved  had a sinus rhythm with in 50 and 100 beats/min regardless  of   absolute  level  of   pulmonary artery pressure but with  measurable  tricuspid  regurgitation  flow  to estimate pulmonary meanand peaked  systolic  pressure.Study conducted   in  the  period   between October 2015 –March 2016 in Al-Imamin Al-Kadhumain teaching  hospital at the echocardiography  specialized  unit.The patients were evaluated by single operator using echocardiography machine GE ,Vivid E9  for measurement of tricuspid regurgitation maximum velocity from  which  peak  systolic pulmonary pressures  were  obtained using the modified Bernoulli equation: 4×TRVmax2 + (5 – 15  mm Hg) (to account for right atrial pressure) and mean  pulmonary  pressures  were  also  obtained  by automatic measurement of the mean  doppler gradient  of the TR signal as  in figure -1-, then measuring  pulmonary artery acceleration time (from which mean  pulmonary  artery  was  obtained  by  this  formula: MPAP =73 -(0.42 - PAAT).[16], in addition to general assessment of left and right sides of the heart structures and functions. Measurement done for three cardiac cycles.
 Demographic data obtained including age, sex, cause of pulmonary  hypertension  ,heart  rate ,  presence  of  atrial   fibrillation
Pulmonary  hypertension was defined as PASP >35 mm Hg. Patients were categorized according to the following categories: normal PSPAP (PSPAP ? 35 mm Hg), mild (PSPAP 36–45 mm Hg), moderate (PSPAP: 46–60 mm Hg) and severe PH (PSPAP>60 mm Hg)[17].
Exclusion    criteria
 were  Patients with pulmonary valve stenosis (defined by a continuous-wave peak jet velocity ?2 m/sec across the pulmonic valve)& other   congenital  heart  diseases, patients with no adequate imaging , patients with no measurable TR &  patients  with  atrial  fibrillation  were excluded from assessment.


Statistical Analysis
The analysis done by the Statistical package for social sciences (SPSS)version 21. Numerical data described as mean and standard deviation. Categorical data described as count and percentage. Chi-square test used to evaluate the association between tested parameters. Pearson correlation test used to assess the significance of correlation between parameters. Sensitivity, specificity, positive and negative predictive values with confidence interval were calculated.
Ethical  consideration 
informed  consent was  obtained from all  patients enrolled  in  this  study.




Results

In this study, 61 patients were involved regardless of magnitude of pulmonary pressure,with mean age of 55.1±17.6 (range 18-85 yr), 18 were male (29.5%) & 43 were females (70.5%) in general as shown in figure -2-.

Discussions

The most commonly accepted transthoracic echocardiography method for the estimation of pulmonary artery pressures relies on the measurement of TRVmax. However, TR is frequently not enough to perform this measurement, as demonstrated by the fact that 25% of patients in one randomly selected clinical cohort had insufficient TR for pulmonary artery systolic pressure determination.[18], so short acceleration time may be the only evidence of pulmonary hypertension and may lead to further evaluation of pulmonary artery pressure. Pulmonary hypertension was found more in females in our study (more than two thirds of those with pulmonary hypertension). Previous literature is divided on this point, as some studies have found differences and others have not [19-23]. Regarding the causes of pulmonary hypertension, group 2 due to left heart diseases according to Dana point classification [3]including (systolic & diastolic left ventricle dysfunctions, hypertension—etc)was more common in our study than other causes and this and this coincides with other literatures[24,25]. In our study, we found that PAAT had a statistically significant association with PSPAP measured by TRVmax, r=- 0.69 and p=0.001, that is consistent with other studies, as inYared et al[26], which observed a strong, inverse correlation between PAAT and PSPAP among patients with a wide range of PSPAP values (r= -0.95). Quantification of this relationship by linear regression led to the derivation of an equation by which PAAT can be used to provide PSPAP values comparable with those obtained using TRVmax, That present a fact, TR-independent approach to the quantitative assessment of SPAP that appears to perform well across a wide range of pulmonary artery pressures. The inverse relation between PAAT and PSPAP measured by TTE is apparent with the fact that patients with PHT have PAAT less than 100ms showed significant association between this value and PSPAP (TR-derived) p< 0.001, which can be used as cut off value for noninvasive assessment of PHT in patient with difficulty to measure TRV max with a sensitivity of 100% and specificity of 63.1%, with a negative predictive value of 100%and positive predictive value of 62.16 % A 100 msec was chosen as a cut off value in our study as It has been shown that measurement of the pulmonaryartery acceleration time (PAAT) through Pulsed-wave Doppler interrogation of the RV outflow tract usually which reveals an acceleration time of <100 msec, that reflects abnormal MPAP[13-16]. In Granstam et al[27],which used the cut-off for PAAT of 100 ms to detect PSPAP of 38 mmHg (for suspecting PH) resulted in a sensitivity of 89% and specificity of 84%. In our study we studied the sensitivity and specificity PAAT of 100 msin relation to PSPAP(TR-derived) and found that all patients in the with PAAT less than 100 ms had PSPAP more than 36mmHg, with sensitivity of 100%, but only around 62 % of those with PAAT more than 100 ms had SPAP less than 36 mmHg which means that a group of patients with PAAT more than 100 ms had PSPAP more than 36 mmHg and in our study we found that those with mild PHT i.e. PASP = 36-45 mmHg72% of them had PAAT more than 100 ms& 28% with PAAT less than 100 ms as in TABLE -2- while those with moderate& severe PHT,14/15&5/5 had PAAT less than 100ms respectively as shown in TABLE -2-, P<0.001. This finding means that PAAT less than 100 s is more appropriate for detectionof moderate & severe PHT than mild PHT.other explanation of the low specificity is the small volume sample. Regarding The relation of PAAT derived MPAP to TR derived MPAP in our study,itshowed significant correlation as shown in figure-5-P<0.001 (r = 0.714). Kitabatake et al[28] which state that PAAT correlates well with MPAP and Its logarithm (r=0.82 and0.88, respectively)as determined by cardiac catheterization and alternatively PAAT derived MPAP showed significant correlation with TR derived MPAP in our study &this agrees with Dabestani et al.[29], which described that same relationship after converting PAAT into MPAP by the following equation: MPAP =73 - (0.42- PAAT). Bossone et al[30] and Lopez-Candales et al[31] who reported that recording PAAT has good correlation withDoppler estimated pressures as a short acceleration time usually reflects PHT.

Conclusions

PAAT is easily obtainable and is strongly correlated with TRVmax, PSAPand MPAP. PAAT more useful for detection of moderate and severe PHT.

References

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