Restrictive Right Ventricular Physiology

Management of tetralogy of Fallot in the pediatric intensive care unit

Tetralogy of Fallot (ToF) is one of the most common congenital cyanotic heart lesions and can present to a variety of health care professionals, including teams working in pediatric intensive care. Pediatric intensive care teams may care for a child with ToF pre-operatively, peri-operatively, and post-operatively. Each stage of management presents its own unique challenges. In this paper we discuss the role of pediatric intensive care in each stage of management.

Impact of right ventricular stiffness on discordance between hemodynamic parameter and regurgitant volume in patients with pulmonary regurgitation

BACKGROUND

Accurate detection of significant pulmonary regurgitation (PR) is critical in management of patients after right ventricular (RV) outflow reconstruction in Tetralogy of Fallot (TOF) patients, because of its influence on adverse outcomes. Although pressure half time (PHT) of PR velocity is one of the widely used echocardiographic markers of the severity, shortened PHT is suggested to be seen in conditions with increased RV stiffness with mild PR. However, little has been reported about the exact characteristics of patients showing discrepancy between PHT and PR volume in this population.

METHODS

Echocardiography and cardiac magnetic resonance imaging (MRI) were performed in 74 TOF patients after right ventricular outflow tract (RVOT) reconstruction [32 ± 10 years old]. PHT was measured from the continuous Doppler PR flow velocity profile and PHT < 100 ms was used as a sign of significant PR. Presence of end-diastolic RVOT forward flow was defined as RV restrictive physiology. By using phase-contrast MRI, forward and regurgitant volumes through the RVOT were measured and regurgitation fraction was calculated. Significant PR was defined as regurgitant fraction ≥ 25%.

RESULTS

Significant PR was observed in 54 of 74 patients. While PHT < 100 ms well predicted significant PR with sensitivity of 96%, specificity of 52%, and c-index of 0.72, 10 patients showed shortened PHT despite regurgitant fraction < 25% (discordant group). Tricuspid annular plane systolic excursion and left ventricular (LV) ejection fraction were comparable between discordant group and patients showing PHT < 100 ms and regurgitant fraction ≥ 25% (concordant group). However, discordant group showed significantly smaller mid RV diameter (30.7 ± 4.5 vs. 39.2 ± 7.3 mm, P < 0.001) and higher prevalence of restrictive physiology (100% vs. 42%, P < 0.01) than concordant group. When mid RV diameter ≥ 32 mm and presence of restrictive physiology were added to PHT, the predictive value was significantly improved (sensitivity: 81%, specificity: 90%, and c-index: 0.89, P < 0.001 vs. PHT alone by multivariable logistic regression model).

CONCLUSION

Patients with increased RV stiffness and non-enlarged right ventricle showed short PHT despite mild PR. Although it has been expected, this was the first study to demonstrate the exact characteristics of patients showing discrepancy between PHT and PR volume in TOF patients after RVOT reconstruction.

Echocardiographic Assessment of Right Ventricular Function in Paediatric Heart Disease: A Practical Clinical Approach

As the right ventricle (RV) plays an integral role in different paediatric heart diseases, the accurate assessment of RV size and function is essential in the diagnosis, management, and prognostication of congenital and acquired cardiac lesions. Yet, echocardiographic evaluation of the RV is challenging because of its complex and variable morphology, its different physiology compared with the left ventricle, and its capability to adapt to different loading conditions associated with congenital and acquired heart diseases within certain ranges. Reliable echocardiographic detection of RV systolic and diastolic dysfunction remains challenging while important for patient management. This review provides an updated, practical approach to assessing RV function in structurally normal hearts and in children with common congenital heart defects and in those with pulmonary hypertension. We also review the impact of tricuspid valve function on RV functional parameters. There is no single functional RV parameter that uniquely describes RV function; instead a combination of different parameters is recommended in clinical practice. Qualitative and quantitative analysis of RV function will be reviewed including more recent techniques such as speckle tracking and 3D echocardiography.

Clinical implications of antegrade diastolic pulmonary artery flow in adults

BACKGROUND

End-diastolic opening of the pulmonary valve and subsequent antegrade diastolic pulmonary artery flow (ADPAF) reflect restrictive right ventricular (RV) physiology in children. However, this has attracted little attention in adults.

PURPOSE

To clarify the clinical implications of ADPAF in adults.

METHODS AND RESULTS

The study population consisted of 23,049 consecutive adult patients who underwent echocardiography in our hospital between 2008 and 2015. ADPAF was found in 17 patients (0.07%). The simultaneous recording of RV and pulmonary artery pressures revealed marked elevation of RV diastolic pressure, which exceeded pulmonary artery pressure at the time of atrial contraction. These results suggested that ADPAF implies RV restriction. Based on the level of tricuspid annular plane systolic excursion (TAPSE), we classified these patients into two groups: reduced RV function (R-RVF) group (12 patients with TAPSE <17 mm) and preserved RV function (P-RVF) group (5 patients with TAPSE ≥17 mm). In the R-RVF group, four patients died, one patient underwent left ventricular assist device implantation, and two patients underwent unplanned hospitalization for heart failure during follow-up. The R-RVF group had poorer prognosis and higher mortality rate compared with the P-RVF group.

CONCLUSIONS

ADPAF reflects RV restriction in adults. ADPAF suggests a less favorable prognosis in patients with R-RVF.

Evolution of echocardiography in adult congenital heart disease: from pulsed-wave Doppler to fusion imaging

The number of patients with adult congenital heart disease (ACHD) has been dramatically increasing and adults with congenital heart disease now outnumber children with congenital heart disease. However, patients with ACHD are still at increased risk of morbidity and mortality due to residua and sequelae. Although echocardiography is an indispensable imaging modality in the comprehensive assessment of ACHD, accurate echocardiographic assessment of ACHD is challenging especially for physicians or sonographers who are not familiar with ACHD because of its complex morphology, physiology, and hemodynamics. A recently developed fusion imaging technology can provide synchronized display of real-time echocardiographic images and multiplanar reconstruction images of computed tomography or magnetic resonance imaging corresponding to the image plane of real-time echocardiography. We have reported the clinical utility of this fusion imaging technology for the precise evaluation of complex ACHD. On the other hand, conventional echocardiographic technology also plays an important role in assessing unique ACHD pathophysiology. For example, restrictive right ventricular physiology is a common finding after tetralogy of Fallot or pulmonary stenosis repair and can be evaluated by conventional pulsed-wave Doppler. In this review, we discuss the clinical usefulness of modern and conventional echocardiographic technologies for the evaluation of ACHD by presenting a case series.

Value of pulmonary annulus index in predicting transannular patch in tetralogy of Fallot repair

OBJECTIVE

It is very important to accurately assess the transannular patch (TAP) in the surgical treatment of tetralogy of Fallot (TOF). The pulmonary annulus index (PAI; the actual pulmonary annulus diameter divided by the expected pulmonary annulus diameter), GA ratio (the ratio of pulmonary annulus and aortic annulus), PAAI (the ratio of pulmonary annulus cross-section and aortic annulus cross-section), and pulmonary annulus Z score (PA Z score) were compared. This study aimed to analyze and explore the application value of PAI in predicting the need for TAP in children undergoing TOF repair.

METHODS

In total, 130 patients who were diagnosed with TOF and underwent TOF repair in Beijing Anzhen Hospital affiliated to Capital Medical University from December 2018 to December 2019 were retrospectively studied. In total, 112 cases were included in this study and 18 cases were excluded, of which 16 cases were aged above 18 years and 2 cases suffered from Down syndrome. They were divided into TAP group and no TAP group; the values of the pulmonary annulus and aortic annulus were measured. GA ratio, PAI, PAAI, the pulmonary annulus Z score, and main pulmonary artery (MPA) Z score were calculated to perform statistical analysis.

RESULTS

A total of 112 patients were included in the study, aged 4-177 months, with an average of 22.87 ± 30.21 months; 66 males and 46 females; weighing 5.3-29 kg, with an average of 9.94 ± 4.08 kg; three cases died, one case died of sepsis caused by pulmonary infection, one case died of low cardiac output syndrome, and one case died of multiple organ failure. In total, 62 cases (55.8%) did not undergo TAP and 50 cases (44.2%) underwent TAP. The pulmonary annulus Z score, main pulmonary artery Z score, and PAI in the TAP group were smaller than those in the no TAP group (p < .05). Receiver operating curve (ROC) analysis showed that when the cut-off value of pulmonary annulus was -1.98, the area under the curve (AUC) was 0.88, the sensitivity was 80%, and the specificity was 71%; when the cut-off value of PAI was 0.53, AUC was 0.85, the sensitivity was 75%, and the specificity was 80%; when the cut-off value of GA ratio was 0.55, AUC was 0.85, the sensitivity was 76%, and the specificity was 80%. The area under the PAAI curve was 0.85, the sensitivity was 76%, and the specificity was 79%. When the pulmonary valve Z score, PAI, GA ratio, PAAI, and MPA Z score were all greater than the dividing value, TAP was avoided in more than 90% of children with TOF. When the pulmonary valve Z score, PAI, GA ratio, PAAI, and the main pulmonary artery Z score were all below the dividing value, more than 90% of children with TOF needed TAP.

CONCLUSION

The predictive effect of PAI as a simple and effective predictor of TAP in TOF radical operation is the same as that of pulmonary annulus Z score, and combining it with the main pulmonary artery Z score was the most accurate method of prediction.

Etiology of right ventricular restrictive physiology early after repair of tetralogy of Fallot in pediatric patients

BACKGROUND

Right ventricular restrictive physiology (RVRP) is a common finding after repair of Tetralogy of Fallot (TOF). The characteristic feature of RVRP is the presence of a direct end-diastolic flow (EDFF) during atrial contraction in the main pulmonary artery. This end-diastolic forward flow is caused by increased right ventricular end-diastolic pressure due to right ventricular myocardial stiffness and decreased right ventricular compliance.

OBJECTIVE

Our main objective is to found out the etiology of RVRP in pediatrics patients who underwent for complete repair of Tetralogy of Fallot (TOF).

METHODS

A total of 50 TOF patients have registered for this study in our hospital from January 2017 to September 2018. The patients were divided in two groups, group A with restrictive physiology and group B without restrictive physiology. The patients selected for this study includes TOF patients, TOF patients with atrial septal defect (ASD), and TOF patients with patent ductus arteriosus (PDA). Ventricular hypertrophy and right heart enlargement were evaluated by electrocardiogram and echocardiography. The other parameters we used to compare between these two groups were sex, age, weight, cardio pulmonary bypass (CPB) time, aortic cross clamping time, transannular patch, SP0₂, RV/LV pressure, ventricular hypertrophy, right heart (RH) enlargement, tricuspid annular plane systolic excursion (TAPSE), pulmonary artery systolic pressure (PASP), TAPSE/PASP ratio, pulmonary annular diameter, intubation time, PICU stay and hematocrit (HCT).

RESULTS

RVRP was identified in 28 patients (58%). Lower SP0₂ (mean: 84.3 ± 7.9%) with p-value 0.015, transannular patch repair (n = 22, 78.5%) with p-value< 0.001, longer cardiopulmonary bypass (CPB) time (mean: 117.6 ± 23 min) with p-value< 0.001, longer aortic cross clamping time (mean: 91.4 ± 20.26 min) with p-value< 0.001, lower TAPSE, lower PASP,lower TAPSE/PASP ratio and presence of hypertrophy (p-value < 0.001) were identified as etiology for restrictive physiology. It was also found that 77% TOF patients with ASD have a higher risk of RVRP in our study.

CONCLUSIONS

In TOF patient's etiology for right ventricular restrictive physiology are associated with lower SP0_2, transannular patch repair, longer CPB and longer aortic cross clamping time, hypertrophy, lower TAPSE, lower PASP and lower TAPSE/PASP ratio.

Differences in Right Ventricular Physiologic Response to Chronic Volume Load in Patients with Repaired Pulmonary Atresia Intact Ventricular Septum/Critical Pulmonary Stenosis Versus Tetralogy of Fallot

BACKGROUND

Patients with pulmonary atresia with intact ventricular septum and critical pulmonary stenosis (PAIVS/CPS) have wide variation in right ventricle (RV) size, systolic function, and diastolic function at birth. Establishment of antegrade pulmonary blood flow creates the potential for RV dilation from chronic pulmonary insufficiency. Future surgical decisions are based on RV size and function, largely supported by longitudinal studies of patients with Tetralogy of Fallot (TOF). Given potential differences in RV physiology and lack of similar data in PAIVS/CPS, the objective of this study was to determine differences in RV size, systolic function, and diastolic function between patients with PAIVS/CPS versus TOF.

METHODS

We retrospectively collected cardiovascular magnetic resonance (CMR) data in 27 patients with PAIVS/CPS (ages 13.3 ± 8.8 years) and 78 with TOF (11.4 ± 5.4 years). RV volumes, ejection fraction (EF), regurgitant fraction, end-diastolic forward flow across the pulmonary valve, and right atrial cross-sectional area were calculated.

RESULTS

There was no difference between the groups in RV end-diastolic volume (RVEDVi), RVEF, or pulmonary regurgitation. RVEF tended to decrease in TOF when RVEDVi exceeded 164 ml/m². In PAIVS/CPS, RVEDVi less frequently reached 164 ml/m² and was not associated with RVEF. There was worse RV diastolic dysfunction in PAIVS/CPS, with 1.5 times larger right atrial area and two times higher pulmonary end-diastolic forward flow (p < 0.0001).

CONCLUSIONS

Patients with PAIVS/CPS have similar RV size, systolic function, and pulmonary regurgitation as TOF. However, impaired RV diastolic function may limit extremes of RV dilatation and impact long-term management of PAIVS/CPS.

Accuracy of a New Echocardiographic Index to Predict Need for Trans-annular Patch in Tetralogy of Fallot

The long-term outcome after repair of tetralogy of Fallot (TOF) is critically dependent pulmonary valve competence that is compromised by trans-annular patch (TAP). We compared a new echocardiographic index [pulmonary annulus index (PAI)] to conventional methods of predicting need for TAP in infants undergoing TOF repair. Consecutive infants undergoing TOF repair were prospectively studied. Pre-operative aortic and pulmonary annuli and main pulmonary artery (MPA) diameters were measured and z scores determined. PAI was a ratio of observed to expected pulmonary annulus (PA) diameter. TAP was based on intra-operative sizing by surgeons blinded to PAI values. Receiver operator curves (ROC) were generated for all PAI, MPA z scores and pulmonary annulus z scores. Of 84 infants (8.6 ± 2.6 months; 7.5 ± 1.3 kg), 36 needed TAP (43%). All the three indices viz. PAI, Pulmonary annulus and MPA z scores performed similarly in predicting need for TAP (ROC curves ~ 80%). Combining cut-offs of MPA z scores (> - 3.83) with either PAI (> 0.73) or PA z score (> - 1.83) predicted avoidance of TAP with ~ 90% accuracy. When both PAI and MPA z scores were below the cut-offs there was an 80% likelihood of TAP. Failure to predict TAP was associated with unicommisural pulmonary valves. PAI was equal to PA z scores in predicting need for TAP during repair of TOF. Combining either with MPA z scores was the most accurate method of prediction. Failure of prediction was mainly due to presence of a unicommissural pulmonary valve.

Usefulness of Pulmonary Arterial End-Diastolic Forward Flow Late After Tetralogy of Fallot Repair to Predict a "Restrictive" Right Ventricle

The functional significance of pulmonary arterial end-diastolic forward flow (EDFF) in patients with repaired tetralogy of Fallot (rTOF) is not fully understood, with conflicting reports regarding its associations with pulmonary regurgitation (PR), right ventricular (RV) size and function, and so-called restrictive RV physiology. To examine these associations, we retrospectively analyzed 399 patients with rTOF who had contemporaneous echocardiography (Echo) and cardiovascular magnetic resonance (CMR) studies. The median age at TOF repair was 0.7 years (0.21, 2.66), age at CMR was 19.8 years (13.0, 29.4), and interval between Echo and CMR was 48 days (0, 182). Doppler identified EDFF in 122 (31%) patients and CMR in 113 patients (28%). Compared with those without EDFF, patients with EDFF were younger, had greater PR, and higher RV end-diastolic volume, stroke volume, and ejection fraction. Markers of RV restriction such as right atrial size did not differ between groups. On multivariable regression, EDFF was associated with higher RV stroke volume and lower left ventricular end-diastolic volume. The association between Echo and CMR measurements of EDFF was modest (area under the receiver operating characteristic curve = 0.684, r = 0.374, p < 0.001). In conclusion, EDFF was common in this large cohort of patients with rTOF, but its presence and extent varied between Echo and CMR. EDFF was associated with greater PR and larger RV size, but not with markers of poor RV compliance such as right atrial enlargement. Mechanisms beyond RV noncompliance may contribute to the presence of EDFF.

Exertional dyspnoea in a 28-year-old woman

CLINICAL INTRODUCTION

A 28-year-old woman with a history of critical pulmonic stenosis, status postsurgical valvotomy and subsequent pulmonary valve replacement, presented to the cardiology clinic with 1 year of progressive exertional dyspnoea. She has a heart rate of 75 bpm and blood pressure of 110/55 mm Hg. Cardiac auscultation reveals a 1/6 systolic ejection murmur along the left sternum and an early 3/6 diastolic decrescendo murmur. A transthoracic echocardiogram is obtained (figure 1).

QUESTIONS

Which of the following would be most likely found during right heart catheterisation?Ratio of pulmonary to systemic blood flow (Qp:Qs) >1.5Pulmonary vascular resistance >3 Wood unitsRight atrial pressure >10mm HgPulmonary artery systolic pressure >45mm Hg E. Pulmonary artery diastolic pressure <10mm Hg.

Dual-Source Computed Tomography Evaluation of Children with Congenital Pulmonary Valve Stenosis

BACKGROUND

Despite dual-source computed tomography (DSCT) technology has been performed well on adults or infants with heart disease, specific knowledge about children with congenital pulmonary valve stenosis (PS) remained to be established.

OBJECTIVES

This original research aimed to establish a professional approach of DSCT performing technology on children and to assess the image quality performed by DSCT to establish a diagnostic evaluation for children with PS.

PATIENTS AND METHODS

Ninety-eight children with congenital PS referred to affiliated hospital of Jining medical college were recruited from October 2013 to March 2015. Participants were divided into four groups according to different ages (0 - 1, 1 - 3, 3 - 7, 7 - 14), or three groups according to different heart rates (< 90, 90 - 110, > 110). Image quality of pulmonary valves was assessed based on a four-point grading scale (1 - 4 points). Those cases achieving a score of ≥ 3 points were selected for further investigation, which played a critical role in our analysis. Correlation analysis was used to identify the effects of age and heart rate on image quality. Additionally, the results evaluated by DSCT were compared with those evaluated from the operation, further confirming the accuracy of DSCT.

RESULTS

Seventy-two cases (73.4%) achieved a score of ≥ 3 points based on pulmonary valve imaging, which were available for further diagnosis. There was a statistically significant difference (P < 0.05) between the four groups except 0 - 1 group and 1 - 3 group, 3 - 7 group and 7 - 14 group, and the image quality of elder group was higher than younger group. Image score was gradually decreased with increased heart rate (F = 19.05, P < 0.01). Heart rate was negatively correlated with pulmonary valve scores (r = -0.391, P < 0.001), while there was no correlation between age and scores (r = 0.185, P = 0.070). The number, shape, commissure, and opening status of pulmonary valves evaluated by DSCT were the same as the results of operation.

CONCLUSION

Heart rate serves a pivotal role in imaging quality of DSCT. DSCT provides a functional evaluation of children with congenital PS and consequently contributes to a theoretical basis for corresponding treatment protocols.

Restrictive right ventricular performance assessed by cardiac magnetic resonance after balloon valvuloplasty of critical pulmonary valve stenosis

BACKGROUND

Little data are published about right ventricular diastolic performance in patients with critical pulmonary valve stenosis after balloon pulmonary valvuloplasty thus far.

METHODS

A total of 44 patients with isolated critical pulmonary valve stenosis who had undergone balloon valvuloplasty with haemodynamic recordings were enrolled to the study; 33 patients who came for follow-up underwent further imaging by echocardiography after 6 months and their right ventricular functional parameters were compared with 33 control patients of the same age and sex. Out of 33 patients, 21 underwent cardiac MRI with late gadolinium enhancement to assess the presence of right ventricular fibrosis.

RESULTS

The right ventricular systolic pressure (p<0.0001) and right ventricular outflow tract gradient (p<0.0001) decreased acutely (p<0.0001) after balloon valvuloplasty. During follow-up, M-mode left ventricular end diastolic dimension (p<0.001) and end systolic dimension increased (p<0.001), whereas right ventricular end diastolic dimension decreased (p<0.001). Compared with controls, patients (n=33) had significantly reduced tricuspid annular Ea and higher E/Ea (p<0.001). Right ventricular systolic dysfunction was also suggested by reduced tricuspid annular systolic velocity (p<0.001). Late gadolinium enhancement was demonstrated in 13 out of 21 patients with restrictive physiology, which involves the anterior right ventricular outflow tract, anterior wall, and inferior wall. The right ventricular late gadolinium enhancement score correlated positively with age (r=0.7, p<0.001) and right ventricular mass index (r=0.52, p<0.001).

CONCLUSION

The persistence of right ventricular diastolic dysfunction after relief of chronic pressure overload of critical pulmonary valve stenosis suggests that a factor - other than increase in afterload - is involved in this physiology. Fibrosis is the most likely factor responsible for persistence of restrictive physiology as documented by late gadolinium enhancement.

Assessment of inter-atrial, inter-ventricular, and atrio-ventricular interactions in tetralogy of Fallot patients after surgical correction. Insights from two-dimensional speckle tracking and three-dimensional echocardiography

BACKGROUND

We aimed to assess biatrial size and function, interactions on atrial and ventricular levels, and atrio-ventricular coupling in patients after tetralogy of Fallot repair.

METHODS

A total of 34 patients with a mean age of 20.9±9 years, and 35 healthy controls, underwent two-dimensional speckle tracking echocardiography for ventricular and atrial strain measurements and real-time three-dimensional echocardiography to assess ventricular and atrial volumes.

RESULTS

When compared with controls, tetralogy of Fallot patients had significantly reduced right atrial peak atrial longitudinal strain (p<0.01), right atrial peak atrial contraction strain (p<0.01), right atrial ejection fraction (p<0.01), left atrial peak atrial longitudinal strain (p<0.01), left atrial peak atrial contraction strain (p<0.05), and left atrial ejection fraction (p<0.01). In the tetralogy of Fallot group, left ventricular ejection fraction was negatively related to the right ventricular end-systolic volume normalised to body surface area (r=-0.62, p<0.01). An association was found in patients between the right atrial peak longitudinal strain and mean right ventricular strain (r=0.64, p<0.01). In patients, the left atrial peak longitudinal strain correlated negatively with right atrial end-diastolic volume normalised to body surface area (r=-0.67, p<0.01), whereas the left atrial ejection fraction correlated weakly with left ventricular ejection fraction (r=0.41, p<0.05).

CONCLUSIONS

In asymptomatic tetralogy of Fallot patients, biatrial dysfunction exists and can be quantified via two-dimensional speckle tracking echocardiography as well as real-time three-dimensional echocardiography. Different forms of interactions on atrial and ventricular levels are evident among such cohorts.

Normal reference values of tissue Doppler imaging parameters for right ventricular function in young adults: a population based study

Background:

Tissue Doppler imaging is used routinely to quantify both left and right ventricular function. However, normal reference values of echocardiography parameters of the right ventricle in Iranian population are still unknown.

Objectives:

Accordingly, we conducted a study to determine the normal values of echocardiography parameters of right ventricular function in a healthy Iranian population.

Patients and Methods:

One hundred and eighty seven healthy volunteer subjects enrolled. Normal subjects were chosen by taking into account history, physical examination, ECG and echocardiography.

Results:

Reference ranges (5th and 95th percentile values) for tricuspid E velocity, A velocity, E/A ratio, deceleration time, annular Sa velocity, Ea velocity, and E/Ea ratio were derived for the whole individuals and for each of the three age groups (< 30, 30–39, 40-49). The deceleration time, E/ Ea ratio and acceleration time of the iso-volumetric contraction time (IVA) were greater in male than in female. All measured parameters were bigger but not statistically significant in the 40-49 year-old group in comparison with the < 30 year-old group. Comparison of data between different groups showed no significant differences between the majority of data when they have been adjusted to body surface area, age and sex.

Conclusions:

The reference ranges presented for the echocardiography parameters of right ventricular function, albeit not conducted in a sizable sample of normal cases, will help to standardize the assessment of RV functions, particularly by tissue Doppler imaging.

Obstruction-induced pulmonary vascular remodeling

Pulmonary obstruction occurs in many common forms of congenital heart disease. In this study, pulmonary artery (PA) banding is used as a model for pulmonary stenosis. Significant remodeling of the vascular bed occurs as a result of a prolonged narrowing of the PAs, and here we quantify the biophysical and molecular changes proximal and distal to the obstruction. Main and branch PAs are harvested from banded and sham rabbits and their mechanical properties are assessed using a biaxial tensile tester. Measurements defined as initial and stiff slopes are taken, assuming a linear region at the start and end of the J-shaped stress-strain curves, along with a transitional knee point. Collagen, elastin assays, Movat's pentachrome staining, and Doppler protocols are used to quantify biochemical, structural, and physiological differences. The banded main PAs have significantly greater initial slopes while banded branch PAs have lower initial slopes; however, this change in mechanical behavior cannot be explained by the assay results as the elastin content in both main and branch PAs is not significantly different. The stiff slopes of the banded main PAs are higher, which is attributed to the significantly greater amounts of insoluble collagen. Shifting of the knee points reveals a decreased toe region in the main PAs but an opposite trend in the branch PAs. The histology results show a loss of integrity of the media, increase in ground substance, and dispersion of collagen in the banded tissue samples. This indicates other structural changes could have led to the mechanical differences in banded and normal tissue.