Measurement Of Pulmonary Artery Pressure Research Articles

Telemetric Catheter-Based Pressure Sensor for Hemodynamic Monitoring: Experimental Experience

The purpose of this study was to evaluate the technical and animal experimental feasibility of a percutaneously implantable pulmonary arterial implant for permanent hemodynamic monitoring. Two systems for measuring pulmonary artery pressure (PAP) as well as pulmonary artery occlusion pressure (PAOP) were developed by modifying a commercially available pulmonary artery catheter (PAC). First, a cable-bound catheter-based system was designed by implementation of a capacitive absolute-pressure sensor in the catheter tip. This system was developed further into a completely implantable telemetric system. The devices were tested in an acute setting in a total of 10 sheep. The implant was placed with its tip in the descending pulmonary artery via the right jugular approach. Results were compared with conventional PAC positioned in the contralateral pulmonary artery using Pearson's correlation coefficients and Bland-Altman plots. Implantation of the monitoring systems was uneventful in 10 animals. Data from two fully functional cable-bound and telemetric pressure monitoring systems were available, with a total of 18,506 measurements. There was an excellent correlation between reference data and the data obtained with the implants (r = 0.9944). Bland-Altman plots indicated a very good agreement between the techniques. We report the development and successful initial test of an implantable catheter-based device for long-term measurement of PAP and PAOP. Both devices may be applicable for hemodynamic monitoring. Further long-term studies for assessing reliability and durability of the device are warranted.

Systolic pulmonary artery pressure and echocardiographic measurements in patients with euthyroid Hashimoto’s thyroiditis

The aim of this study was to investigate systolic pulmonary artery pressure (SPAP) and echocardiographic findings in patients with euthyroid Hashimoto's thyroiditis (HT). Thirty (8 male, 22 female, mean age 47.4+/-10.5 yr) consecutive patients with euthyroid HT and 30 (9 male, 21 female, mean age 46.4+/-10.7 yr) healthy controls were included in the study. Transthoracic echocardiography was performed for all patients and levels of thyroid hormones, thyroid autoantibodies, glucose, insulin, urea, and creatinine were compared. There were no significant differences in sex, age, body mass index, serum free T4, serum TSH, lipid profiles between patients and controls. Mean SPAP in patients with euthyroid HT were significantly higher than in controls (31.6+/-5.0 vs 25.6+/-4.5 mmHg, p=0.005). Late diastolic transmitral velocity and isovolumic relaxation time were also significantly higher in patients in comparison to controls. In addition, euthyroid HT patients with tricuspid or mitral regurgitation had a higher grade. Correlation between SPAP and antithyroid antibodies and TSH, however, was not significant in this population. Pulmonary arterial pressure is higher in patients with euthyroid HT. There may be a relationship between elevated pulmonary arterial pressure and autoimmune thyroid disease independent from thyroid function status. However, further investigations are needed to determine the exact mechanism of association between autoimmune thyroid diseases and pulmonary hypertension.

Evidence-Based Practice Habits: Transforming Research Into Bedside Practice

Evidence-Based Practice Habits: Transforming Research Into Bedside Practice

Clinical value of noninvasive pulmonary artery systolic pressure estimates in our patients with pulmonary artery hypertension

Invasive and noninvasive measurements of pulmonary artery pressures are used to diagnose and control patients with pulmonary artery hypertension (PAH) [1-3]. In our hospital all patients with PAH are diagnosed and first treated in the ICU. Besides right heart catheterization (RHC), noninvasive estimate of pulmonary artery systolic pressure (PASP) with transthoracic echocardiography (TTE) is performed. As RHC is an invasive procedure it is not suitable to repeat it. We compared values of invasively and noninvasively measured PASP to examine correlation so we could use TTE for ambulatory control and estimation of treatment success in our patients.

Importance of Hydration and Exercise in the Diagnosis of Pulmonary Arterial Hypertension Secondary to Scleroderma

Background: Approval for pulmonary vasodilator therapy for pulmonary arterial hypertension (PAH) secondary to scleroderma requires the measurement of mean pulmonary artery pressure (mPAP) and pulmonary capillary wedge pressure (PCWP) via right heart catheterisation (RHC). The effect of fluid loading and exercise on these parameters in patients with scleroderma is poorly characterised.

Correlation of Echocardiographic and Hemodynamic Parameters in Pulmonary Hypertension Assessment Prior to Heart Transplantation

Introduction Invasive assessment of pulmonary artery pressure (PAP), via right heart catheterization, is part of the usual protocol prior to heart transplantation. Echocardiography is considered a valuable technique to evaluate PAP. We sought to determine the reliability of measurements of PAP via a noninvasive technique, echocardiography, in relation to the estimated PAP via right catheterization. We also determined its safety when invasive procedures are restricted to just patients with pulmonary hypertension (PHT) according to echocardiographic parameters. Materials and methods We performed a retrospective study of 67 right catheterizations performed in our hospital, within the heart transplant study protocol, from January 2000 to December 2006. PAP parameters were estimated by echocardiography and right catheterization. Results Hemodynamically, 57.1% of the patients had severe PHT (more than 45 mm Hg mean PAP); 13.2% moderate PHT (between 35 and 45 mm Hg mean PAP); 12.1% had mild PHT (between 25 and 35 mm Hg mean PAP); and 17.6% of patients showed no PHT. Pearson correlation index with systolic PAP (estimated via echocardiography) and mean PAP (calculated via invasive method) was 0.69 ( P < .001). PHT was considered significant when systolic PAP estimated via echocardiography reached more than 40 mm Hg and mean PAP estimated via right catheterization reached more than 35 mm Hg, the value from which the vasodilator test was carried out. According to these parameters, echocardiography showed a sensitivity of 89% to diagnose significant PHT and 46% specificity, with positive and negative predictive values of 70% and 76%, respectively.

The usefulness of contrast during exercise echocardiography for the assessment of systolic pulmonary pressure

BackgroundThe systolic pulmonary artery pressure (PAPs) can be accurately estimated, non-invasively, using continuous-wave Doppler (CWD) ultrasound measurement of the peak velocity of a tricuspid regurgitant (TR) jet.However, it is often difficult to obtain adequate tricuspid regurgitation signals for measurement of PAPs, what could lead to its underestimation. Therefore, utilization of air-blood-saline contrast has been implemented for the improvement of Doppler signal in several clinical contexts.It is now recommended in the evaluation of patients with pulmonary hypertension. Physical activity is severely restricted in patients with PAH, being exertional dypnea the most typical symptom. Exercise stress echo-Doppler imaging allows assessment of the response to exercise. It is an excellent screening test for patients with suspected PAH. Our purpose was to evaluate the value and accuracy of agitated saline with blood contrast echocardiography, in the improvement of the Doppler signal, to quantify PAPs during treadmill exercise-echocardiography.PurposeTo evaluate the value of contrast echocardiography, using agitated saline with blood, in the improvement of the Doppler signal used to quantify the pulmonary artery systolic pressure during exercise.MethodsFrom a total of 41 patients (pts), we studied 38 pts (93%), 35 women, aged 54 ± 12 years-old. 27 with the diagnosis of systemic sclerosis, 10 with history of pulmonary embolism and one patient with a suspected idiopathic PAH, who were referred to the Unity of Heart Failure and Pulmonary Hypertension for screening of PAH. According to the Unity protocol, a transthoracic echocardiogram was made, in left decubitus (LD), with evaluation of right ventricle-right atria gradient (RV/RAg). A peripheral venous access was obtained, with a 3-way stopcock and the patients were placed in orthostatism (O), with a new evaluation of RV/RAg. Exercise echocardiography (EE) was begun, with evaluation of RV/RAg at peak exercise (P) and afterwards agitated saline (8 cc with 1 cc of air and 1 cc of blood) was injected, followed by a new evaluation of RV/RAg (PC) and then the interruption of the EE. Pulmonary Hypertension was diagnosed when RV/RAg at the end of the exercise was superior to 40 mmHg.ResultsThe quality of Doppler signal was deteriorated in 5 pts, maintained in 6 pts and improved in 26 pts, with the use of contrast. In one patient, an interventricular septal defect was diagnosed. In 6 pts, a Doppler signal was only obtained with the use of contrast. In 15 pts, a RV/RAg superior to 40 mmHg was only obtained with the use of contrast. Of these, 9 have already been submitted to right heart cathetherism, that confirmed the diagnosis of pulmonary hypertension in 5 of them (56%). RV/RAg (P) was 44 ± 11 mmHg and RV/RAg (PC) was 54 ± 11 mmHg, p < 0,001.Conclusion1. The method is applicable in a large number of patients. 2. RV/RA gradients obtained at peak exercise are higher with the use of contrast, and the clinical meaning of this difference should be evaluated in a larger number of pts submitted to right heart cathetherism. The high number of false positives should lead to a higher diagnostic threshold. 3. This method seems to have relevant clinical value in the diagnosis of pulmonary arterial hypertension.

PHYSIOLOGIC MANAGEMENT OF HEMODYNAMICS IN THE OPERATING ROOM USING ARTERIAL PRESSURE-BASED STROKE VOLUME AND STROKE VOLUME VARIATION

PURPOSE: Traditional measures including pulmonary artery or central venous pressure measurements to guide fluid management are unreliable. Physiologic management utilizing arterial pressure-based stroke volume (SV) and stroke volume variation (SVV) will facilitate fluid management in the operating room.

Acute necrotising pulmonary vasculitis and pulmonary hypertension in a juvenile dog

A five-month-old female Jack Russell terrier was presented for investigation of acute lethargy, anorexia, coughing, respiratory distress and weakness. Examination findings included cyanosis, a grade 3 of 6 systolic heart murmur and prolonged capillary refill time. Radiography and echocardiography revealed severe pulmonary hypertension, cor pulmonale and right-sided heart failure. Indirect measurement of the systolic pulmonary artery pressure estimated pressures over 100 mmHg. Despite treatment the patient died. Post-mortem examination did not identify a congenital cardiovascular anomaly. Histopathology confirmed acute necrotising pulmonary arteritis and immunohistochemistry failed to identify any immune complex or complement deposition.

Magnetic Resonance–Derived 3-Dimensional Blood Flow Patterns in the Main Pulmonary Artery as a Marker of Pulmonary Hypertension and a Measure of Elevated Mean Pulmonary Arterial Pressure

Pulmonary hypertension is a disease characterized by an elevation in pulmonary arterial pressure that is diagnosed invasively via right heart catheterization. Such pathological altered pressures in the pulmonary vascular system should lead to changes in blood flow patterns in the main pulmonary artery. Forty-eight subjects (22 with manifest pulmonary hypertension, 13 with latent pulmonary hypertension, and 13 normal control subjects) underwent time-resolved 3D magnetic resonance phase-contrast imaging of the main pulmonary artery. Velocity fields that resulted from measurements were calculated, visualized, and analyzed with dedicated software. Main findings were as follows: (1) Manifest pulmonary hypertension coincides with the appearance of a vortex of blood flow in the main pulmonary artery (sensitivity and specificity of 1.00, 95% confidence intervals of 0.84 to 1.00 and 0.87 to 1.00, respectively), and (2) the relative period of existence of the vortex correlates significantly with mean pulmonary arterial pressure at rest (correlation coefficient of 0.94). To test the diagnostic performance of the vortex criterion, we furthermore investigated 55 patients in a blinded prospective study (22 with manifest pulmonary hypertension, 32 with latent pulmonary hypertension, and 1 healthy subject), which resulted in a sensitivity of 1.00 and specificity of 0.91 (95% confidence intervals of 0.84 to 1.00 and 0.76 to 0.98, respectively). Comparison of catheter-derived mean pulmonary artery pressure measurements and calculated mean pulmonary artery pressure values resulted in a standard deviation of differences of 3.6 mm Hg. Vortices of blood flow in the main pulmonary artery enable the identification of manifest pulmonary hypertension. Elevated mean pulmonary arterial pressures can be measured from the period of vortex existence.

Retrograde catheterization of the right heart in patients with occluded femoral veins

Occlusion of the femoral veins is a frequent complication of cardiac catheterization in small children. If the venous femoral approach is not available, a jugular approach is generally used for catheterization of the right heart. To describe and evaluate an alternative retrograde approach for catheterization of the right heart in small children with a ventricular septal defect or single ventricle. Between January 2004 and January 2007 we attempted retrograde catheterization of the right heart via the femoral artery using a 4 French sheath in eight children with occluded femoral veins. The procedure was planned under awake sedation. Median age was five months (range 4-60) and median weight was 5 kg (range 4-10). Diagnoses were as follows: single ventricle (n = 6); pulmonary atresia and ventricular septal defect (n = 1); complex transposition of the great arteries (n = 1). The procedure was successful in six patients, enabling measurement of pulmonary arterial pressure and pulmonary angiography. The procedure was abandoned in two patients because of ventricular arrhythmias. One patient had concomitant dilatation of aortic recoarctation and one had embolization of aortopulmonary collaterals. With the exception of transient ventricular arrhythmias, no acute or late complications occurred. In particular, transient or permanent atrioventricular block, occurrence of new aortic insufficiency, and acute or late thrombosis of the femoral artery were not observed. Retrograde catheterization of the right heart in small children is feasible and relatively safe. This technique can be performed without general anaesthesia and avoids a jugular approach.

Comparison of a Radiofrequency-Based Wireless Pressure Sensor to Swan-Ganz Catheter and Echocardiography for Ambulatory Assessment of Pulmonary Artery Pressure in Heart Failure

The goal of this work was to evaluate the accuracy of a new heart failure (HF) sensor (HFS) (Heart Failure Sensor, CardioMEMS Inc., Atlanta, Georgia) pulmonary artery pressure (PAP) monitoring compared with Swan-Ganz (SG) (Hospira, Inc., Lake Forest, Illinois) catheterization and echocardiography (ECHO) in ambulatory HF patients. There is an increasing interest in the development of ambulatory monitoring devices aiming to adjust therapy and prevent hospitalizations in HF patients. Twelve patients with HF and New York Heart Association functional class II to IV were included in this study. The HFS was deployed into the pulmonary artery under angiography, allowing wireless PAP measurement. Two independent blind operators performed 3 HFS measurements at each visit, with simultaneous ECHO at 2, 14, 30, 60, and 90 days. Swan-Ganz catheterization was performed at 0 and 60 days. Linear regression was used as a measure of agreement. Variability between methods and interobserver variability were evaluated by Bland-Altman analysis. Mean age was 63 +/- 14.6 years. Systolic PAP was 64 +/- 22 mm Hg and 58 +/- 22 mm Hg for HFS and SG, respectively (p < 0.01). Both methods showed a significant correlation (r2 = 0.96 baseline, r2 = 0.90 follow-up, p < 0.01), with a mean difference of 6.2 +/- 4.5 mm Hg. Diastolic PAP was 23 +/- 14 mm Hg and 28 +/- 16 mm Hg for HFS and SG, respectively (r2 = 0.88 baseline, r2 = 0.48 follow-up, p < 0.01), with a mean difference of -1.6 +/- 6.8 mm Hg. Systolic PAP was 60 +/- 20 mm Hg and 62 +/- 12 mm Hg for HFS and ECHO, respectively (r2 = 0.75, p < 0.01), with a mean difference of -2.6 +/- 11 mm Hg. There was no significant interobserver difference. The HFS provides an accurate method for PAP assessment in the intermediate follow-up of HF patients.

Hemodynamic and Prognostic Implications of Net Atrioventricular Compliance in Patients with Mitral Stenosis

On the basis of the close association of left atrial compliance with pulmonary hypertension in patients with mitral stenosis, we hypothesized that: (1) Doppler-derived net atrioventricular compliance (C(n)) can be used for predicting the occurrence of mitral valve (MV) replacement or percutaneous mitral commissurotomy (PMC); and (2) determinants of exercise capacity are variable depending on C(n). We consecutively enrolled 26 patients (22 women; mean age, 47.0 +/- 6.1 years; range, 35-59 years) with pure moderate or severe mitral stenosis, in whom comprehensive echocardiography was performed at rest. C(n) was derived from the equation that has been previously validated (ie, C(n) = 1270 x [MV area by 2-dimensional planimetry/mitral E-wave downslope]. Measurements of stroke volume and systolic pulmonary artery pressure were repeated immediately after symptom-limited treadmill exercise test within 60 seconds. On the basis of earlier reports, C(n) less than 4 mL/mm Hg was selected to define abnormally small C(n). During a mean duration of 24-month follow-up, C(n) of less than 4 mL/mm Hg could reliably predict the occurrence of either MV replacement or PMC, which was confirmed by multivariate logistic regression analysis. In patients with C(n) less than 4 mL/mm Hg, exercise duration was found to be closely correlated primarily with resting systolic pulmonary artery pressure (r = -0.73, P = .03), whereas in patients with C(n) greater than or equal to 4 mL/mm Hg, postexercise stroke volume was the only determinant of exercise capacity (r = 0.49, P = .04). When combining C(n) less than 4 mL/mm Hg with MV area less than 1.0 cm(2) as a cut-off value for predicting MV replacement or PMC, the sensitivity improved from 63.6% to 81.8% (P = .05). Left atrial compliance estimated by C(n) with Doppler echocardiography allows us to effectively predict the future occurrence of MV replacement or PMC, with a special usefulness in patients with moderate mitral stenosis. In addition, determinants of exercise capacity were variable depending on the degree of C(n).

UTILITY OF CT SCAN FOR DETECTION AND GRADING THE SEVERITY OF PULMONARY HYPERTENSION IN PATIENTS WITH PARENCHYMAL LUNG DISEASE

PURPOSE: Pulmonary Hypertension (PH) is defined as Pulmonary Artery Pressure (PAP) >25 mm Hg. Although right heart catherization is the gold standard, 2D Echo is commonly used to detect PH and to grade its severity. 2D Echo detects PH based on the presence of tricuspid regurgitation and measurement of the regurgitant jet using the modified Bernoulli's equation (4 × velocity squared). PAP measurements between 21 and 40 mm Hg and > 40 mm Hg are consistent with Mild-moderate and severe pulmonary hypertension respectively.

Absence of T Cells Confers Increased Pulmonary Arterial Hypertension and Vascular Remodeling

Severe pulmonary arterial hypertension (SPH) is a frequently lethal condition characterized by pulmonary vascular remodeling and right heart strain or failure. SPH is also often associated with autoimmune and collagen vascular disorders. To study the effects of T cells on the development of experimental SPH. Athymic nude rats lacking T cells were treated with a single subcutaneous injection of vascular endothelial growth factor (VEGF) receptor blocker SU5416 (20 mg/kg) to induce pulmonary vascular endothelial cell apoptosis. Immunohistochemical analysis and IL-4 levels of the lung tissue were performed. Cell death and proliferation were assessed by Western blot and immunohistochemistry. In contrast to SU5416-treated euthymic rats that develop SPH only in combination with chronic hypoxia, athymic nude rats developed SPH and vascular remodeling (similar to clinical SPH) at normoxic conditions as demonstrated by measurements of pulmonary artery pressure and right ventricle hypertrophy. Pulmonary arterioles became occluded with proliferating endothelial cells and were surrounded by mast cells, B cells, and macrophages. IL-4, proliferating cell nuclear antigen, and collagen type I levels were markedly increased in SU5416-treated athymic rat lungs. Antibody deposition was noted along the vascular endothelium in rats with SPH. Finally, protection from SPH was conferred by immune challenge with spleen cells from euthymic nude rats. These studies demonstrate the importance of a complete, intact immune system in protecting against pulmonary angioproliferation in this new model of SPH as well as the importance of intact VEGF receptor signaling for lung endothelial cell homeostasis.

Wireless Acoustic Communication With a Miniature Pressure Sensor in the Pulmonary Artery for Disease Surveillance and Therapy of Patients With Congestive Heart Failure

The purpose of this study was to examine the feasibility of repeated pulmonary artery (PA) pressure determinations using a newly developed acoustic wireless implanted communication system. Congestive heart failure management strategies based on monitored intracardiac hemodynamics in patients receiving the best-available therapy may improve outcome. Although electromagnetic communication requires a large antenna for sufficient energy transfer, acoustic energy readily penetrates deep into the body, uses little energy, and uses small internal transducers for bidirectional operation. A miniature device was developed and implanted using right heart catheterization. The ability to obtain PA pressure from the implant using wireless acoustic communication was examined in 8 pigs and 10 patients with congestive heart failure. Macroscopic and histopathologic examinations were performed at 6 months after implantation. The accuracy of PA pressure measurement was determined by comparison with simultaneous pressures from a Millar catheter. The device was successfully implanted in the PA using right heart catheterization. There were no implantation or later device-related complications. Pulmonary artery pressure tracings were repeatedly obtained from all implants. Normal reactions to intravascular implant were observed macroscopically and in histologic sections. Standard deviations of the difference between implant and Millar PA diastolic pressure were 1.45 and 1.2 mm Hg (animals and humans, respectively). Data were useful for patient management. This pilot study demonstrates, for the first time, that acoustic wireless communication with a miniature implanted sensor is feasible and provides repeated PA pressure measurement. This feat makes possible multiple novel applications for monitoring and therapeutic interventions based on measurements from deeply implanted devices.

Noninvasive, Indirect Measurement of Pulmonary Artery Pressure

The gold standard for measuring pulmonary artery pressure (PAP) is right heart catheterization. However, the usefulness of this technique is limited in patients with lung disease because of a poor acoustic window. The aim of this study was to assess PAP in a group of healthy persons using a noninvasive, indirect measurement procedure derived from the venous return flow velocity wave.Twenty-three healthy volunteers with a mean (SD) age of 34 (9) years were evaluated. Measurements were made with a Hitachi EUB 5000 ultrasound device (3.5 MHz wave). The subject was placed in supine decubitus with neck hyperextended and head turned to one side. B-mode images were used to locate the point in the internal jugular vein 1 cm higher than its union with the subclavian vein. A color flow image was obtained of the vessel and a pulsed wave was then used to measure velocities. After 5 identical cycles, an estimate of PAP was derived from the ratio of maximum diastolic and systolic flow rates.On the right side, the mean (SD) ratio between flow rates was 0.50 (0.08), corresponding to a mean PAP of 15 (2.4) mm Hg. On the left side, the ratio was 0.55 (0.09), corresponding to a mean PAP of 16 (2.8) mm Hg. The nonsignificant difference between mean PAP values on the right and left was 1.3 (3.1) mm Hg, and higher values were on the left.Mean PAP values obtained with the described procedure are within the normal range for a healthy population. Transcutaneous venous Doppler ultrasound is useful for estimating PAP in healthy individuals.

Implantation of Cryopreserved Mitral Allograft into the Tricuspid Position in an Experimental Study in Sheep: Technical Aspects of Implantation and Immediate Results Evaluated by Epicardial Echocardiography

Cryopreserved mitral allograft valve (MAV) offers theoretical advantages over conventional mechanical or biological prostheses in tricuspid position, especially in infectious endocarditis patients. MAV processing and tricuspid valve (TV) replacement in a sheep model is described. In 20 adult sheep, MAV were harvested, processed and cryopreserved. One month later, recipient's TV were excised and the MAVs were transplanted into the tricuspid position in 13 sheep, under general anaesthesia, via a right thoracotomy, with an extracorporeal circulation (ECC) and cardioplegic heart arrest. Both MAV papillary muscles were anchored into the right ventricular wall by transmural stitches and the MAV anulus was sewn into the recipient's tricuspid anulus. After weaning from ECC, the anatomy and function of the MAV in the tricuspid position was assessed by epicardial echocardiography. The average duration of the ECC was 58 minutes (42-88), the cardioplegic heart arrest was 36 minutes (28-45). Weaning from EEC was always uneventful. Right atrial & pulmonary artery pressure measurements and epicardial echocardiography documented good function of all MAVs. MAV remained mechanically strong enough for implantation into the tricuspid position. Reproducible technique of MAV transplantation into the tricuspid position with excellent early postoperative haemodynamic performance was developed.

Quantitative 3D pulmonary MR-perfusion in patients with pulmonary arterial hypertension: Correlation with invasive pressure measurements

Purpose Pathological changes of the peripheral pulmonary arteries induce pulmonary arterial hypertension (PAH). Aim of this study was to quantitatively assess the effect of PAH on pulmonary perfusion by 3D-MR-perfusion techniques and to compare findings to healthy controls. Furthermore, quantitative perfusion data were correlated with invasive pressure measurements. Material and methods Five volunteers and 20 PAH patients (WHO class II or III) were examined using a 1.5 T MR scanner. Measurement of pulmonary perfusion was done in an inspiratory breathhold (FLASH3D; 3.5 mm × 1.9 mm × 4 mm; TA per 3D dataset 1.5 s). Injection of contrast media (0.1 mmol Gd-DTPA/kg BW) and image acquisition were started simultaneously. Evaluation of 3D perfusion was done using singular value decomposition. Lung borders were outlined manually. Each lung volume was divided into three regions (anterior, middle, posterior), and the following parameters were assessed: Time-to-Peak (TTP), blood flow (PBF), blood volume (PBV), and mean transit time (MTT). In 10 patients invasive pulmonary artery pressure measurements were available and correlated to the perfusion measurements. Results In both, controls and patients, an anterior-to-posterior gradient with higher PBF and PBV posterior was observed. In the posterior lung region, a significant difference ( p < 0.05) was found for TTP (12 s versus 16 s) and MTT (4 s versus 6 s) between volunteers and patients. PBF and PBV were lower in patients than in volunteers (i.e. dorsal regions: 124 versus 180 ml/100 ml/min and 10 versus 12 ml/100 ml), but the difference failed to be significant. The ratio of PBF and PBV between the posterior and the middle or ventral regions showed no difference between both groups. A moderate linear correlation between mean pulmonary arterial pressure (mPAP) and PBV ( r = 0.51) and MTT ( r = 0.56) was found. Conclusion The only measurable effect of PAH on pulmonary perfusion is a prolonging of the MTT. There is only a moderate linear correlation of invasive mPAP with PBV and MTT.

Endothelial Nitric Oxide Synthase Polymorphisms Do Not Influence Pulmonary Artery Systolic Pressure at Altitude

Previous genetic association studies in high-risk subjects have suggested that polymorphisms in the gene encoding endothelial nitric oxide synthase (eNOS) may be associated with susceptibility to high altitude pulmonary edema (HAPE). We aimed to determine whether eNOS polymorphisms influence systolic pulmonary artery pressure measurements (PASP) in healthy trekkers ascending to high altitude. We examined two polymorphisms of the eNOS gene in Caucasian volunteers: Glu298Asp variant and 27-base pair (bp) variable number of tandem repeats polymorphism (27-bp VNTR). In 33 subjects, the relationships between polymorphisms and absolute pulmonary artery systolic pressure measurements (PASP), determined by echocardiography, were assessed at sea level and 1, 3, and 7 days after acute ascent by vehicle transport to 5200 m. As expected, there was a significant rise in pulmonary artery pressure on ascent to high altitude. By contrast, at sea level and at each time point at high altitude, no difference was found in mean PASP according to eNOS polymorphism. We found no association of Glu298Asp and 27-bp VNTR polymorphisms in the eNOS gene with PASP in a population of healthy trekkers at low or high altitude.