Noninvasive assessment of pulmonary artery pressures: moving beyond tricuspid regurgitation velocities

Pulmonary hypertension subjects exhibit right ventricular transient exertional dilation during supine exercise stress echocardiography

Pulmonary hypertension is a condition with high morbidity and mortality. Resting transthoracic echocardiography is a pivotal diagnostic and screening test for pulmonary hypertension. The role of exercise stress echocardiography in the diagnosis of pulmonary hypertension is not well-established. We studied right ventricular size changes during exercise using exercise stress echocardiography to assess differences between normal and pulmonary hypertension patients and evaluate test safety, feasibility, and reproducibility. Healthy control and pulmonary hypertension patients performed recumbent exercise using a bicycle ergometer. Experienced echocardiography sonographers recorded the following resting and peak exercise right ventricular parameters using the apical four chamber view: end-diastolic area; end-systolic area; mid-diameter; basal diameter; and longitudinal diameter. Two cardiologists masked to clinical information subsequently analyzed the recordings. Parameters with acceptable inter-rater reliability were analyzed for statistical differences between the normal and pulmonary hypertension patient groups and their association with pulmonary hypertension. We enrolled 38 healthy controls and 40 pulmonary hypertension patients. Exercise stress echocardiography testing was found to be safe and feasible. Right ventricular size parameters were all readily obtainable and all had acceptable inter-observer reliability except for right ventricular longitudinal diameter. During exercise, healthy controls demonstrated a decrease in right ventricular end-systolic area, end-diastolic area, mid-diameter, and basal diameter (P < 0.05). Conversely, pulmonary hypertension patients demonstrated an increase in right ventricular end-systolic area, end-diastolic area, and mid-diameter (P < 0.05). These changes were unaffected by multivariate corrections. The sensitivity for pulmonary hypertension of an increase in right ventricular size was 97.2% with a negative predictive value of 95.2%. The ROC C-statistic for increase in right ventricular size was 0.93. This transient exertional dilation (TED) of the right ventricle is observed in pulmonary hypertension patients but not in healthy controls. Recumbent right ventricular exercise stress echocardiography is a feasible and safe diagnostic test for pulmonary hypertension which warrants additional study.

Pulmonary Hypertension in Hemodialysis Patients Following Repeated Endovascular Thrombectomy

BACKGROUND

The prevalence of pulmonary hypertension is unusually high in Taiwanese patients with end-stage renal disease. Thrombosis of hemodialysis grafts is common and pulmonary embolism has been reported after endovascular thrombectomy. The aim of this study was to evaluate the relationship between pulmonary hypertension and endovascular thrombectomy of hemodialysis grafts.

METHODS

One hundred and ten patients on hemodialysis via arteriovenous grafts were enrolled in our study. The mean pulmonary artery pressure (PAP) was measured by right heart catheterization. Clinical information was collected by review of medical records. Comorbid cardiopulmonary disease was evaluated by echocardiography and chest X-ray. The history of patient vascular access thrombosis was reviewed from database, hemodialysis records, and interviews with staff at hemodialysis centers.

RESULTS

Fifty-two participants (47%) had pulmonary hypertension diagnosed by right heart catheterization. There was no difference in the number of thrombectomy procedures between patients with and without pulmonary hypertension. Based on multivariate analysis, the number of prior endovascular thrombectomy procedures did not correlate with mean PAP (F-value = 1.10, p = 0.30) nor was it associated with pulmonary hypertension (odds ratio = 0.92, p = 0.17).

CONCLUSIONS

Prior endovascular arteriovenous graft thrombectomies were not associated with pulmonary hypertension or increased mean PAP in end-stage renal disease patients on maintenance hemodialysis.

The frequency of pulmonary hypertension in patients with juvenile scleroderma

Juvenile scleroderma (JS) represents a rarely seen group of connective tissue diseases with multiple organ involvement. Cardiac involvement in JSS is well known and, although rare in children, it may be an important cause of mortality and morbidity. Therefore, an early determination of cardio-vascular and pulmonary involvement is of the most relevance to reduce the mortality in patients with juvenile scleroderma. The aim of the study was to explore the non-invasive methods (Doppler echocardiography, pulmonary function tests), Forced vital capacity (FVC) and Carbon monoxide diffusion capacity (DLCO) in the assessment of the cardiopulmonary involvement in patients with JS. The assessment of pulmonary arterial pressure (PAP) and risk factors for pulmonary arterial hypertension (PAH) were made by the measurement of maximum tricuspid insufficiency (TI), end-diastolic pulmonary insufficiency (PI), ratio of acceleration time (AT) to ejection time (ET) (AT/ET), right atrial pressure (RAP) and contraction of vena cava inferior during inspiration. Thirty-five patients with confirmed JS were included in the study. The mean age of onset of the disease was 9.57 years (median 10 years, range 2-18 years). The mean disease duration and follow-up time was 2 years (median 1 year, range 0.5-8 years) and 3.57 years (median 2 years, range 0.5-14.5 years), respectively.The values of all the analyzed parameters including TI, PI, AT/ET, PAP, FVC and DLCO were found to be within normal ranges in all the patients tested, confirming an uncommonness of cardiopulmonary involvement in patients with juvenile scleroderma.

Single intraperitoneal injection of monocrotaline as a novel large animal model of chronic pulmonary hypertension in Tibet minipigs

Objective

The purpose of this study was to establish an animal model of chronic pulmonary hypertension with a single-dose intraperitoneal injection of monocrotaline (MCT) in young Tibet minipigs, so as to enable both invasive and noninvasive measurements and hence facilitate future studies.

Methods

Twenty-four minipigs (8-week-old) were randomized to receive single-dose injection of 12.0 mg/kg MCT (MCT group, n = 12) or placebo (control group, n = 12 each). On day 42, all animals were evaluated for pulmonary hypertension with conventional transthoracic echocardiography, right heart catheterization (RHC), and pathological changes. Findings of these studies were compared between the two groups.

Results

At echocardiography, the MCT group showed significantly higher pulmonary arterial mean pressure (PAMP) compared with the controls (P<0.001). The pulmonary valve curve showed v-shaped signals with reduction of a-waves in minipigs treated with MCT. In addition, the MCT group had longer pulmonary artery pre-ejection phases, and shorter acceleration time and ejection time. RHC revealed higher mean pulmonary arterial pressure (mPAP) in the MCT group than in the control group (P<0.01). A significant and positive correlation between the mPAP values and the PAMP values (R = 0.974, P<0.0001), and a negative correlation between the mPAP and ejection time (R = 0.680, P<0.0001) was noted. Pathology demonstrated evidence of pulmonary vascular remodeling and higer index of right ventricular hypertrophy in MCT-treated minipigs.

Conclusion

A chronic pulmonary hypertension model can be successfully established in young minipigs at six weeks after MCT injection. These minipig models exhibited features of pulmonary arterial hypertension that can be evaluated by both invasive (RHC) and noninvasive (echocardiography) measurements, and may be used as an easy and stable tool for future studies on pulmonary hypertension.

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.