Personne :
Honos, George

En cours de chargement...
Photo de profil
Adresse électronique
Date de naissance
Projets de recherche
Structures organisationnelles
Nom de famille
Institut universitaire de cardiologie et de pneumologie, Université Laval
Identifiant Canadiana

Résultats de recherche

Voici les éléments 1 - 5 sur 5
  • Publication
    Hemodynamic and physical performance during maximal exercise in patients with an aortic bioprosthetic valve : comparison of stentless versus stented bioprostheses
    (Elsevier, 1999-11-01) Honos, George; Jobin, Jean; Cartier, Paul C.; Pibarot, Philippe; Dumesnil, Jean G.; Durand, Louis-Gilles
    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.
  • Publication
    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
    (Elsevier, 1999-02-15) Honos, George; Jobin, Jean; Lemieux, Michel; Pibarot, Philippe; Dumesnil, Jean G.; Durand, Louis-Gilles
    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. Previous studies have shown that many patients with an aortic bioprosthesis can have a relatively high transprosthetic pressure gradient despite a normally functioning valve.1, 2, 3 and 4 This is most often due to prosthesis–patient mismatch, which is defined as a disproportion between the size of the prosthesis and the patient’s body surface area. Despite this adverse hemodynamic condition, these patients do relatively well clinically, and there are only small differences in the medium-term prognosis of these patients when compared with patients without evidence of mismatch.2, 3 and 5 To explain this apparent discrepancy, we hypothesized that the behavior of the bioprosthesis during exercise might be different from that predicted from theoretical models1 and 4 and in particular, that the increase in gradient occurring in bioprostheses during exercise might be less than expected. To investigate this hypothesis, we performed Doppler echocardiographic studies of patients with a stented bioprosthesis in the aortic position at rest and during exercise.
  • Publication
    Substitution of left ventricular outflow tract diameter with prosthesis size is inadequate for calculation of the aortic prosthetic valve area by the continuity equation.
    (C.V. Mosby, 1995-01-01) Honos, George; Pibarot, Philippe; Durand, Louis-Gilles; Dumesnil, Jean G.
    It remains uncertain whether prosthetic ring size should be used interchangeably with measured left ventricular outflow tract (LVOT) diameter in the continuity equation to estimate the aortic prosthetic valve area by transthoracic Doppler echocardiography. To determine the difference in area caused by this substitution, the area of the prosthetic valve was calculated in 143 patients with aortic bioprostheses by use of the standard continuity equation with the measured LVOT diameter (LVOT method) and then with the bioprosthetic size (size method). Compared with known in vitro prosthetic valve areas, the LVOT method (r = 0.86; standard error of the estimate 9 0.16 cm2; p < 0.001) was more accurate than the size method (r = 0.74; standard error of the estimate _ 0.40 cm2; p < 0.001). The prosthetic valve area estimated by the size method overestimated the area estimated by the LVOT method by an average of 15% -4"- 23% (p < 0.001). This difference in area between the two methods has increased with the interval since implantation of the bioprosthesis (p = 0.01). It is concluded that prosthetic size should not be used instead of LVOT diameter during calculation of aortic prosthetic valve area. This restriction is partioalarly important in patients with older bioprostheses
  • Publication
    Estimation of pulmonary artery pressure by spectral analysis of the second heart sound
    (Elsevier, 1996-10-01) Chen, Danmin; Honos, George; Pibarot, Philippe; Durand, Louis-Gilles
    The objective of the present work was to test and validate a noninvasive method based on spectral analysis of the second heart sound (S2) to estimate the pulmonary artery (PA) systolic pressure in 89 patients with a bioprosthetic heart valve. The technique was compared with continuous-wave Doppler estimation of PA systolic pressure in these patients. The heart sounds recorded at the pulmonary area on the chest wall were digitized by computer. The spectra of 52 and those of the aortic (A2) and the pulmonary (P2) components of S2 were computed with a fast-Fourier transform. Seven features were extracted from these spectra. The statistical analysis performed with the Pearson linear correlation coefficient showed that the best estimation of PA systolic pressure obtained by spectral phonocardiography (r = 0.84, SEE ± 5.6 mm Hg, p < 0.0001) was provided by the following equation: PA systolic pressure = 47 + 0.68 Fp - 4.4 Qp - 17 FpFa - 0.15 Fs, where Fs and Fp are dominant frequencies associated with the maximal amplitude of the power spectra of S2 and P2, respectively, Qp is the quality of resonance of P2, and FpFa is the ratio of the dominant frequencies of P2 and A2, respectively.
  • Publication
    The effect of prosthesis-patient mismatch on aortic bioprosthetic valve hemodynamic performance and patient clinical status.
    (Elsevier, 2016-04-04) Honos, George; Pibarot, Philippe; Durand, Louis-Gilles; Dumesnil, Jean G.
    BACKGROUND: High pressure gradients occurring through normally functioning prosthetic valves appear to be related to a mismatch between the effective orifice area of the prosthesis and the patient's body surface area. OBJECTIVE: To determine whether prosthesis-patient mismatch affects clinical and hemodynamic status, a group of patients with a bioprosthetic heart valve in the aortic position was prospectively evaluated at 6.2+/-4.4 years after implantation by transthoracic Doppler echocardiography. METHODS: Manufacturer-derived in vitro valve areas were available in 61 patients allowing classification into two subgroups, with or without mismatch, based on a valve area at implantation indexed for body surface area 0.85 cm2/m2 or less, or greater than 0.85 cm2/m2. Clinical and hemodynamic parameters evaluated at follow-up included New York Heart Association (NYHA) class distribution, mean transprosthetic gradient, prosthetic valve area and cardiac index. RESULTS: Prosthesis-patient mismatch was present in 32 of 61 patients (52%). Although NYHA class of the patients was similar in both groups, hemo-dynamic performance of the aortic bioprostheses was worse in patients with mismatch than in patients with no mismatch, as indicated by a higher mean gradient (22+/-9 versus 15+/-8 mm Hg, P=0.002) and a lower cardiac index (3.0+/-0.7 versus 3.4+/-0.7 L/min/m2, P=0.04). The prevalence and severity of intrinsic prosthetic dysfunction were similar in both groups. Despite similar NYHA functional class distribution in both groups, the occurrence of syncope, acute pulmonary edema and angina pectoris was significantly higher in patients with mismatch (50% versus 21%, P=0.017). CONCLUSIONS: Prosthesis-patient mismatch is associated with worse hemodynamic performance and higher prevalence of adverse clinical events. However, mismatch did not promote accelerated hemodynamic or structural deterioration of the bioprosthesis.