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Biomedical subjects

P Pibarot

Publications and source records attributed to P Pibarot.

At least 19 recordsLinked to original sources
PubMed2002

Estimation of pulmonary arterial pressure by a neural network analysis using features based on time-frequency representations of the second heart sound.

The objective of the study was to develop a non-invasive method for the estimation of pulmonary arterial pressure (PAP) using a neural network (NN) and features extracted from the second heart sound (S2). To obtain the information required to train and test the NN, an animal model of pulmonary hypertension (PHT) was developed, and nine pigs were investigated. During the experiments, the electrocardiogram, phonocardiogram and PAP were recorded. Subsequently, between 15 and 50 S2 heart sounds were isolated for each PAP stage and for each animal studied. A Coiflet wavelet decomposition and a pseudo smoothed Wigner-Ville distribution were used to extract features from the S2 sounds and train a one-hidden-layer NN using two-thirds of the data. The NN performance was tested on the remaining one-third of the data. NN estimates of the systolic and mean PAPs were obtained for each S2 and then ensemble averaged over the 15-50 S2 sounds selected for each PAP stage. The standard errors between the mean and systolic PAPs estimated by the NN and those measured with a catheter were 6.0 mmHg and 8.4 mmHg, respectively, and the correlation coefficients were 0.89 and 0.86, respectively. The classification accuracy, using 23 mmHg mean PAP and 30 mmHg systolic PAP thresholds between normal PAP and PHT, was 97% and 91%, respectively.

Animals↗
PubMed2002

A new, simple, and accurate method for non-invasive estimation of pulmonary arterial pressure.

OBJECTIVE: To develop and validate a new non-invasive method for the estimation of pulmonary arterial pressure (PAP) based on advanced signal processing of the second heart sound. DESIGN: Prospective comparative study. SETTING: Referral cardiology centre. PATIENTS: This method was first tested in 16 pigs with experimentally induced pulmonary hypertension and then in 23 patients undergoing pulmonary artery catheterisation. METHODS: The heart sounds were recorded at the surface of the thorax using a microphone connected to a personal computer. The splitting time interval between the aortic and the pulmonary components of the second heart sound was measured using a computer assisted spectral dechirping method and was normalised for heart rate. RESULTS: The systolic PAP varied between 14-73 mm Hg in pigs and between 20-70 mm Hg in patients. The normalised splitting interval was measurable in 97% of the recordings made in pigs and 91% of the recordings made in patients. There was a strong relation between the normalised splitting interval and the systolic PAP (pigs: r = 0.94, standard error of the estimate (SEE) = 5.3 mm Hg; patients: r = 0.84, SEE = 7.8 mm Hg) or the mean pulmonary pressure (pigs: r = 0.94, SEE = 4.1 mm Hg; patients: r = 0.85, SEE = 5.8 mm Hg). CONCLUSIONS: This study shows that this new non-invasive method based on advanced signal processing of the second heart sound provides an accurate estimation of the PAP.

Blood Pressure↗
PubMed2001

Comparison of valve resistance with effective orifice area regarding flow dependence.

Aortic valve resistance has been proposed to represent the severity of aortic stenosis because some studies observed that it was less affected by change in flow than the valve-effective orifice area, but this issue remains controversial. The objective of this study was to systematically analyze the theoretical and practical determinants of these parameters in relation to changes in flow. Valve area and resistance in different valves were studied in vitro in a pulse duplicator system at different flow rates and in vivo in 90 subjects referred to either exercise or dobutamine infusion. Theoretical analysis and experimental results both demonstrated a unique relation between resistance (RES), valve-effective orifice area (EOA), and flow rate (Q): RES = K x (Q/EOA(2)). Accordingly, in fixed stenoses or in mechanical valves, resistance increased markedly with flow rate both in vitro (+0.88 +/- 0.26%/% of flow increase) and in vivo (mechanical valves: +2.09 +/- 4.61, fixed stenotic valves: +0.59 +/- 0.32%/%), whereas valve area did not change significantly (<0.2%/%). In contrast, in valves with a flexible orifice (bioprostheses and some patients with aortic stenosis), resistance was less increased due to the increase in valve area. Thus, both from a theoretical and a practical standpoint, valve resistance is much more flow dependent than valve area, particularly in fixed stenoses. Situations in which resistance does not increase with flow rate are unpredictable and are found in flexible valves when there is a concomitant increase in valve area.

Adult↗
PubMed2001

Patient-prosthesis mismatch can be predicted at the time of operation.

BACKGROUND: Patient-prosthesis mismatch is a frequent cause of high postoperative gradients in normally functioning prostheses. The objective of this study was to determine whether mismatch can be predicted at the time of operation. METHODS: Indices used to predict mismatch were valve size, indexed internal geometric area, and projected indexed effective orifice area (EOA) calculated at the time of operation, and results were compared with indexed EOA and mean gradients measured by Doppler echocardiography after operation in 396 patients. RESULTS: The sensitivity and specificity of these indices to detect mismatch, defined as a postoperative indexed EOA of 0.85 cm2/m2 or less, were respectively: 35% and 84% for valve size, 46% and 85% for indexed internal geometric area, and 73% and 80% for projected indexed EOA. Projected indexed EOA also correlated best with resting (r = 0.67) and exercise (r = 0.77) postoperative gradients. CONCLUSIONS: The projected indexed EOA calculated at the time of operation accurately predicts mismatch as well as resting and exercise postoperative gradients, whereas valve size and indexed internal geometric area cannot be used for this purpose.

Adult↗
PubMed2001

Extraction of the aortic and pulmonary components of the second heart sound using a nonlinear transient chirp signal model.

The objective of this paper is to adapt and validate a nonlinear transient chirp signal modeling approach for the analysis and synthesis of overlapping aortic (A2) and pulmonary (P2) components of the second heart sound (S2). The approach is based on the time-frequency representation of multicomponent signals for estimating and reconstructing the instantaneous phase and amplitude functions of each component. To evaluate the accuracy of the approach, a simulated S2 with A2 and P2 components having different overlapping intervals (5-30 ms) was synthesized. The simulation results show that the technique is very effective for extracting the two components, even in the presence of noise (-15 dB). The normalized root-mean-squared error between the original A2 and P2 components and their reconstructed versions varied between 1% and 6%, proportionally to the duration of the overlapping interval, and it increased by less than 2% in the presence of noise. The validated technique was then applied to S2 components recorded in pigs under normal or high pulmonary artery pressures. The results show that this approach can successfully isolate and extract overlapping A2 and P2 components from successive S2 recordings obtained from different heartbeats of the same animal as well from different animals.

Animals↗
PubMed2001

A single center experience with the freestyle bioprosthesis: midterm results at the Québec Heart Institute.

Stentless bioprostheses show excellent early hemodynamic performance. However, longevity still remains unknown. This study reports midterm follow-up in 419 patients in which a Freestyle bioprosthesis (Medtronic Heart Valves, Minneapolis, MN) was inserted between January 1993 and January 2000 at the Quebec Heart Institute (Ste-Foy, Québec, Canada). Mean age at implantation was 68.0 +/- 8.2 years. Implantation was subcoronary in 81.9% of the patients, as a root replacement in 16.5%, and as a root inclusion in 1.7%. Mortality at 30 days was 6.2% for the whole cohort (2.8% for isolated subcoronary aortic valve replacement). Female gender, root implantation, valve sizes 19 to 21 mm, previous surgery, a history of stroke and diabetes were identified as predictors of 30-day mortality. Actuarial freedom from all death causes was 81.5% at 7 years; freedom from valve-related deaths 97.0%, and freedom from cardiac deaths 92.7%. Freedom from thromboembolic events was 86.1% at 7 years (55.1% of events were < 30 days). Freedom from endocarditis and hemorrhagic complications were respectively 98.5% and 95.6% at 7 years. Six patients required reoperations for valve explantation: 2 for endocarditis, 2 for structural dysfunction, and 2 for nonstructural dysfunction. Incidence of moderate or severe valve insufficiency at annual echocardiographic follow-up was: discharge: 0.6%; year 1: 0.7%; year 2: 1.3%; year 3: 3.3%; year 4: 3.7%; year 5: 2.6%; year 6: 0%. At 6 years after implantation, mean transvalvular gradient and effective valve orifice area were comparable to the year 1 values. This single center experience with the Medtronic Freestyle prosthesis shows preserved hemodynamic performance and low valve-related complications at midterm.

Actuarial Analysis↗
PubMed2000

Midterm echocardiographic follow-up after Ross operation.

BACKGROUND: The pulmonary autograft (Ross) operation is an attractive treatment for aortic valve disease, but hemodynamic follow-up is not well defined. METHODS AND RESULTS: One hundred thirty-two consecutive patients (62% male, mean age 40+/-11 years) were followed up to 5 years after the Ross operation. Echocardiography was performed early (within 30 days), 3 to 6 months, and yearly after surgery. The valve effective orifice area (EOA) and mean transvalvular gradient of both aortic and pulmonary valves were measured, and transvalvular regurgitation was assessed by using color Doppler echocardiography. EOA was indexed for body surface area. The hemodynamic performance was excellent for both the aortic and pulmonary valves early after surgery (gradient, 3+/-4 and 3+/-4 mm Hg, respectively). It remained stable thereafter for the aortic valve, whereas there was a significant deterioration of the EOA (-0. 74+/-0.82 cm(2)) and gradient (+6+/-8 mm Hg) for the pulmonary valve, which occurred mostly during the first 6 months after surgery. This hemodynamic deterioration resulted in suboptimal (defined as an EOA index <0.85 cm(2)/m(2)) hemodynamics in 19.3% of the patients, to the extent that 3 (2%) of the 132 patients eventually had to be subjected to further surgery for severe pulmonary valve stenosis. CONCLUSIONS: The pulmonary autograft provides continued excellent hemodynamics in the aortic position, whereas moderately high gradients can be found across the pulmonary homograft in some patients. Further studies are necessary to identify the factors responsible for the deterioration of the hemodynamic performance of the homograft in the pulmonary position and to determine its impact on right ventricular function and clinical status.

Adult↗
PubMed2000

Hemodynamic performance during maximum exercise in adult patients with the ross operation and comparison with normal controls and patients with aortic bioprostheses.

This study examines the resting and exercise hemodynamic performance of the pulmonary autografts in the aortic position as well as of the homografts used for right ventricular outflow reconstruction in patients undergoing the Ross operation. Previous studies have reported excellent resting hemodynamics in patients who underwent aortic valve replacement with a pulmonary autograft. However, there are very few studies of their hemodynamic performance during exercise. Twenty adult subjects who underwent the Ross operation and 12 normal control subjects were submitted to maximum romp bicycle exercise. The valve effective orifice areas and transvalvular gradients of both aortic (autograft) and pulmonary (homograft) valves were measured at rest and at peak of maximum exercise using Doppler echocardiography. Valve areas were indexed for body surface area. The hemodynamics of the aortic valve were very similar in Ross subjects and in control subjects at rest and during exercise. However, the indexed valve area of the pulmonary valve at rest was significantly (p < 0.001) lower in the Ross subjects (1.10 +/- 0.46 cm2/ m2) than in the control subjects (1.95 +/- 0.41 cm2/m2), resulting in higher (p = 0.004) mean gradients at rest (Ross: 9 +/- 7 mm Hg vs control: 2 +/- 1 mm Hg) and at peak exercise (Ross: 21 +/- 14 mm Hg vs control: 7 +/- 2 mm Hg). The pulmonary autograft provided excellent hemodynamics in the aortic position either at rest or during maximum exercise, whereas moderately high gradients were found during exercise across the homograft implanted in the pulmonary valve position. Future improvement of the Ross procedure should be oriented toward the search of new methods to prevent the deterioration of the homografts.

Adult↗
PubMed2000

Assessment of aortic valve stenosis severity: A new index based on the energy loss concept.

BACKGROUND: Fluid energy loss across stenotic aortic valves is influenced by factors other than the valve effective orifice area (EOA). We propose a new index that will provide a more accurate estimate of this energy loss. METHODS AND RESULTS: An experimental model was designed to measure EOA and energy loss in 2 fixed stenoses and 7 bioprosthetic valves for different flow rates and 2 different aortic sizes (25 and 38 mm). The results showed that the relationship between EOA and energy loss is influenced by both flow rate and aortic cross-sectional area (A(A)) and that the energy loss is systematically higher (15+/-2%) in the large aorta. The coefficient (EOAxA(A))/(A(A)-EOA) accurately predicted the energy loss in all situations (r(2)=0.98). This coefficient is more closely related to the increase in left ventricular workload than EOA. To account for varying flow rates, the coefficient was indexed for body surface area in a retrospective study of 138 patients with moderate or severe aortic stenosis. The energy loss index measured by Doppler echocardiography was superior to the EOA in predicting the end points, which were defined as death or aortic valve replacement. An energy loss index </=0.52 cm(2)/m(2) was the best predictor of adverse outcomes (positive predictive value of 67%). CONCLUSIONS: This new energy loss index has the potential to reflect the severity of aortic stenosis better than EOA. Further prospective studies are necessary to establish the relevance of this index in terms of clinical outcomes.

Adult↗
PubMed2000

Transvenous coil embolization of an extrahepatic portosystemic shunt in a dog: a naturally occurring model of portosystemic malformations in humans.

Congenital patent ductus venosus (PDV) occurs far more commonly in dogs than in people; consequently, the natural course of the disease in dogs was studied as a model to understand the pathophysiology behind the vascular anomaly and its response to therapy better. In this report, the authors describe the results of percutaneous coil embolization as a single procedure in a dog with a single congenital extrahepatic portocaval shunt and compare portosystemic vascular anomalies (PSVA) seen in dogs with those seen in children.

Angiography↗
PubMed2000

Hemodynamic and clinical impact of prosthesis-patient mismatch in the aortic valve position and its prevention.

Prosthesis-patient mismatch is present when the effective orifice area of the inserted prosthetic valve is less than that of a normal human valve. This is a frequent problem in patients undergoing aortic valve replacement, and its main hemodynamic consequence is the generation of high transvalvular gradients through normally functioning prosthetic valves. The purposes of this report are to present an update on the concept of aortic prosthesis-patient mismatch and to review the present knowledge with regard to its impact on hemodynamic status, functional capacity, morbidity and mortality. Also, we propose a simple approach for the prevention and clinical management of this phenomenon because it can be largely avoided if certain simple factors are taken into consideration before the operation.

Aortic Valve Stenosis↗
PubMed2000

Nonlinear transient chirp signal modeling of the aortic and pulmonary components of the second heart sound.

This paper describes a new approach based on the time-frequency representation of transient nonlinear chirp signals for modeling the aortic (A2) and the pulmonary (P2) components of the second heart sound (S2). It is demonstrated that each component is a narrow-band signal with decreasing instantaneous frequency defined by its instantaneous amplitude and its instantaneous phase. Each component is also a polynomial phase signal, the instantaneous phase of which can be accurately represented by a polynomial having an order of thirty. A dechirping approach is used to obtain the instantaneous amplitude of each component while reducing the effect of the background noise. The analysis-synthesis procedure is applied to 32 isolated A2 and 32 isolated P2 components recorded in four pigs with pulmonary hypertension. The mean +/- standard deviation of the normalized root-mean-squared error (NRMSE) and the correlation coefficient (rho) between the original and the synthesized signal components were: NRMSE = 2.1 +/- 0.3% and rho = 0.97 +/- 0.02 for A2 and NRMSE = 2.52 +/- 0.5% and rho = 0.96 +/- 0.02 for P2. These results confirm that each component can be modeled as mono-component nonlinear chirp signals of short duration with energy distributions concentrated along its decreasing instantaneous frequency.

Animals↗
PubMed1999

Hemodynamic and physical performance during maximal exercise in patients with an aortic bioprosthetic valve: comparison of stentless versus stented bioprostheses.

OBJECTIVES: The objective of this study was to compare stentless bioprostheses with stented bioprostheses with regard to their hemodynamic behavior during exercise. BACKGROUND: Stentless aortic bioprostheses have better hemodynamic performances at rest than stented bioprostheses, but very few comparisons were performed during exercise. METHODS: Thirty-eight patients with normally functioning stentless (n = 19) or stented (n = 19) bioprostheses were submitted to a maximal ramp upright bicycle exercise test. Valve effective orifice area and mean transvalvular pressure gradient at rest and during peak exercise were successfully measured using Doppler echocardiography in 30 of the 38 patients. RESULTS: At peak exercise, the mean gradient increased significantly less in stentless than in stented bioprostheses (+5 +/- 3 vs. +12 +/- 8 mm Hg; p = 0.002) despite similar increases in mean flow rates (+137 +/- 58 vs. +125 +/- 65 ml/s; p = 0.58); valve area also increased but with no significant difference between groups. Despite this hemodynamic difference, exercise capacity was not significantly different, but left ventricular (LV) mass and function were closer to normal in stentless bioprostheses. Overall, there was a strong inverse relation between the mean gradient during peak exercise and the indexed valve area at rest (r = 0.90). CONCLUSIONS: Hemodynamics during exercise are better in stentless than stented bioprostheses due to the larger resting indexed valve area of stentless bioprostheses. This is associated with beneficial effects with regard to LV mass and function. The relation found between the resting indexed valve area and the gradient during exercise can be used to project the hemodynamic behavior of these bioprostheses at the time of operation. It should thus be useful to select the optimal prosthesis given the patient's body surface area and level of physical activity.

Bioprosthesis↗
PubMed1999

Comparison of ketoprofen and carprofen administered prior to orthopedic surgery for control of postoperative pain in dogs.

OBJECTIVE: To compare analgesic and adverse effects of ketoprofen and carprofen when used to control pain associated with elective orthopedic surgeries in dogs. DESIGN: Prospective randomized clinical trial. ANIMALS: 93 client-owned dogs: 46 undergoing reconstruction of the cranial cruciate ligament, 47 undergoing femoral head and neck excision, and 15 control dogs anesthetized for radiographic procedures. PROCEDURE: Dogs undergoing surgery were randomly given ketoprofen, carprofen, or saline (0.9% NaCl) solution, SC, prior to surgery. Pain score and serum cortisol concentration were recorded for 12 hours after surgery for all dogs. When pain score was > or = 7, oxymorphone was administered i.m. Bleeding time was measured prior to and during surgery. RESULTS: The proportion of dogs that required oxymorphone was significantly higher for the carprofen and placebo groups than for the ketoprofen group. Pain score for the placebo group was significantly higher than for the ketoprofen and carprofen groups, 2, 8, and 9 hours after surgery. Cortisol concentration was significantly higher for the placebo group than for the carprofen group at 4 and 6 hours after surgery. Significant differences were not detected between ketoprofen and carprofen groups with respect to pain score and cortisol concentration. Bleeding time was significantly longer for the ketoprofen group than for the other groups during surgery. One dog treated with ketoprofen developed a hematoma at the surgical site. CONCLUSIONS AND CLINICAL RELEVANCE: Ketoprofen and carprofen given prior to surgery were effective for postoperative pain relief in dogs. However, ketoprofen should not be used when noncompressible bleeding may be a problem.

Animals↗
PubMed1999

Usefulness of the indexed effective orifice area at rest in predicting an increase in gradient during maximum exercise in patients with a bioprosthesis in the aortic valve position.

This study examines the hemodynamic behavior of aortic bioprosthetic valves during maximum exercise. Nineteen patients with a normally functioning stented bioprosthetic valve and preserved left ventricular function were submitted to maximum ramp bicycle exercise. In 14 of the 19 patients, valve effective orifice area and mean gradient were measured at rest and during exercise using Doppler echocardiography. At peak exercise (mean maximal workload 118 +/- 53 W), the cardiac index increased by 122 +/- 34% (+3.18 +/- 0.71 L/min/ m2, p <0.001), whereas mean gradient increased by 94 +/- 49% (+12 +/- 8 mm Hg, p <0.001), and effective orifice area by 9 +/- 13% (+0.15 +/- 0.22 cm2, p = 0.02). A strong correlation was found between the increase in mean gradient during maximum exercise and the valve area at rest indexed for body surface area (r = 0.84, p <0.0001). Due to the increase in valve area, the increase in gradient was less (-9 +/- 7 mm Hg, -41 +/- 33%, p = 0.0006) than theoretically predicted assuming a fixed valve area. These results suggest that the effective orifice area of the bioprostheses has the capacity to increase during exercise; therefore, limiting the increase in gradient. The relation found between the indexed effective orifice area at rest and the increase in gradient during exercise should be useful in predicting the hemodynamic behavior of a stented bioprosthesis during exercise.

Aged↗
PubMed1999

Changes in left ventricular mass and function after aortic valve replacement: a comparison between stentless and stented bioprosthetic valves.

The objective of this study was to compare stentless bioprostheses with stented bioprostheses with regard to the postoperative changes in left ventricular (LV) mass and function. Forty patients with aortic stenosis undergoing valve replacement with a stentless (20 patients) or a stented (20 patients) bioprosthesis were evaluated early (baseline), 1 year, and 2 years after operation. Left ventricular mass index was calculated with the corrected American Society of Echocardiography formula. The relative changes between end-diastole and end-systole in LV mid-wall radius, length, and volume (ejection fraction) were determined with a previously validated model for dynamic geometry of the left ventricle. Overall, a significant decrease was found in LV mass index (from 155 +/- 30 to 112 +/- 23 g/m(2); P <.001) and a significant increase in longitudinal shortening (from 0.12 +/- 0.11 to 0.22 +/- 0.08; P <. 001), and ejection fractions (from 0.67 +/- 0.11 to 0.71 +/- 0.10; P =.017). No significant change was found in the mid-wall radius shortening fraction. Two years after surgery, the extent of LV mass regression was greater in stentless bioprostheses (-51 +/- 18 vs -35 +/- 17 g/m(2); P =.01), though the average mass index was similar in both groups (114 +/- 26 vs 110 +/- 20 g/m(2)). Also at 2 years, the longitudinal shortening fraction was greater in patients with a stentless bioprosthesis (0.25 +/- 0.07 vs 0.18 +/- 0.08; P =.03). In conclusion, this study suggests that the superior hemodynamic performance of stentless bioprostheses may have some benefits with regard to LV mass regression and function after aortic valve replacement. The significance of these benefits in terms of prognosis remains to be determined.

Aged↗