Biomedical subjects

Theo J C Faes

Publications and source records attributed to Theo J C Faes.

3 recordsLinked to original sources

PubMed2006

Quantification of right ventricular afterload in patients with and without pulmonary hypertension.

Right ventricular (RV) afterload is commonly defined as pulmonary vascular resistance, but this does not reflect the afterload to pulsatile flow. The purpose of this study was to quantify RV afterload more completely in patients with and without pulmonary hypertension (PH) using a three-element windkessel model. The model consists of peripheral resistance (R), pulmonary arterial compliance (C), and characteristic impedance (Z). Using pulmonary artery pressure from right-heart catheterization and pulmonary artery flow from MRI velocity quantification, we estimated the windkessel parameters in patients with chronic thromboembolic PH (CTEPH; n = 10) and idiopathic pulmonary arterial hypertension (IPAH; n = 9). Patients suspected of PH but in whom PH was not found served as controls (NONPH; n = 10). R and Z were significantly lower and C significantly higher in the NONPH group than in both the CTEPH and IPAH groups (P < 0.001). R and Z were significantly lower in the CTEPH group than in the IPAH group (P < 0.05). The parameters R and C of all patients obeyed the relationship C = 0.75/R (R(2) = 0.77), equivalent to a similar RC time in all patients. Mean pulmonary artery pressure P and C fitted well to C = 69.7/P (i.e., similar pressure dependence in all patients). Our results show that differences in RV afterload among groups with different forms of PH can be quantified with a windkessel model. Furthermore, the data suggest that the RC time and the elastic properties of the large pulmonary arteries remain unchanged in PH.

Adult↗

PubMed2005

Interventricular septal configuration at mr imaging and pulmonary arterial pressure in pulmonary hypertension.

PURPOSE: To investigate whether a relationship exists between septum shape and systolic pulmonary arterial pressure (PAP) in patients with pulmonary hypertension. MATERIALS AND METHODS: Study protocol was approved by institutional ethics review committee; all patients gave informed consent. Right-sided heart catheterization with vasodilator testing was performed in 39 adult subjects suspected of having pulmonary hypertension. There were 11 men and 28 women, aged 21-75 years (mean, 46 years). Only two patients showed favorable response to vasodilators, defined by a decrease in PAP of more than 20%. Synchronous right- and left-ventricular pressure measurements and four-chamber magnetic resonance (MR) imaging were used to identify timing of maximal leftward ventricular septal bowing within cardiac cycle. Septal bowing was evaluated with MR, measured on short-axis cine heart images, and expressed as curvature (reciprocal of radius). Curvature was quantified on one image (the one that showed the most severe distortion of normal septal shape). The relationship between systolic PAP and septal curvature was tested with linear regression analysis. P <.05 was considered to indicate a statistically significant difference. RESULTS: Of 39 subjects, 37 had pulmonary hypertension. Maximal distortion of normal septal shape was found during right ventricular relaxation phase. Systolic PAP was proportional to septal curvature: r=0.77 (P < .001), slope=-114.7, and intercept=67.2. In the two vasodilator responsive subjects, a significant reduction of leftward ventricular septal bowing was observed in response to reduction of right ventricular pressure. CONCLUSION: In 37 patients with pulmonary hypertension, systolic PAP higher than 67 mm Hg may be expected when leftward curvature is observed.

Adult↗

PubMed2005

Correction of phase offset errors in main pulmonary artery flow quantification.

PURPOSE: To investigate whether an existing method for correction of phase offset errors in phase-contrast velocity quantification is applicable for assessment of main pulmonary artery flow with an MR scanner equipped with a high-power gradient system. MATERIALS AND METHODS: The correction method consists of fitting a surface through the time average of stationary pixels of velocity-encoded phase images, and subtracting this surface from the velocity images. Pixels are regarded as stationary if their time standard deviation falls into the lowest percentile. Flow was measured in the main pulmonary artery of 15 subjects. Each measurement was repeated on a stationary phantom. The phase offset error in the phantom was used as a reference. Correction was applied with varying polynomial surface orders (0-5) and stationarity percentiles (5-50%). The optimal surface order and stationarity percentile were determined by comparing the fitted surface with the phantom. RESULTS: Using a first-order surface and a (noncritical) 25% percentile, the correction method significantly reduced the phase offset error from 1.1 to 0.35 cm/second (RMS), which is equivalent to a reduction from 11% to 3.3% of mean volume flow. Phase error correction strongly affected stroke volume (range -11 to 26%). CONCLUSION: The method significantly reduces phase offset errors in pulmonary artery flow.

Adult↗