Biomedical subjects

Michel Ovize

Publications and source records attributed to Michel Ovize.

4 recordsLinked to original sources

PubMed2003

Longitudinal strain quantitates regional right ventricular contractile function.

The assessment of contractile function of the right ventricle (RV) is an important clinical issue, but this remains difficult because of its complex anatomy and structure. We thought to investigate whether new Doppler-derived myocardial deformation indexes may quantify regional contractile RV function during varying loading conditions. In nine pigs, ultrasonic crystals were inserted longitudinally in the RV inflow and outflow tracts to assess regional contractile function. The same RV segments and the interventricular septum were imaged using apical echocardiographic views. Regional function was assessed using two parameters: 1) systolic strain (SS), representing the relative magnitude of segmental systolic shortening; and 2) its temporal derivative, peak systolic strain rate (SR), i.e., the maximal velocity of segmental shortening. Data were acquired at baseline and during partial pulmonary artery constriction (PAC) and inferior vena cava occlusion (IVCO). SS decreased significantly after PAC and IVCO in both the inflow and outflow tracts but only during IVCO in the septum. SR was less sensitive to loading variations in all segments. A significant correlation was found between SS values derived from sonomicrometry and myocardial Doppler in RV segments (r = 0.84, P < 0.001). Thus regional strain and SR provide complementary information on the heterogeneous RV contractile function and can be accurately and noninvasively quantified using Doppler myocardial imaging.

Animals↗

PubMed2003

Ginkgo biloba extract EGb 761 attenuates myocardial stunning in the pig heart.

Myocardial stunning, a transient contractile dysfunction that appears following a brief period of ischemia, is at least partly due to the production of oxygen-derived free radicals. The objective of the present study was to determine whether the Ginkgo biloba extract EGb761, which has antioxidant properties in vitro, can attenuate myocardial stunning in vivo. Forty-seven anesthetized open-chest farm pigs underwent 10 min of occlusion of the left anterior descending coronary artery (LAD), followed by 3 hours of reperfusion. They were pretreated with either physiological saline, 100 mg or 300 mg of EGb 761 (Protocol I) or 3 mg or 9 mg of ginkgolide B (GkB) (Protocol II). Contractile function was assessed by sonomicrometry. Both doses of EGb 761 significantly improved recovery of contractile function in the reperfused myocardium with segment shortening averaging 23 +/- 5 % of baseline values at 3 hours post-reflow in controls versus 81 +/- 10 % and 57 +/- 12 % in the EGb100 and EGb300 groups, respectively (p < 0.05 vs control in both cases). In contrast, neither dose of GkB improved functional recovery during reperfusion. ESR experiments revealed that EGb761 resulted in a 59 % decrease in myocardial spin-adduct release during reperfusion (p < 0.05 versus control and GkB groups). A significant 28 % decrease (p < 0.05 vs control group) was also obtained in GkB-treated animals. These results indicate that EGb 761 can attenuate myocardial stunning following a brief ischemic insult in the in situ pig heart by an effect that involves a decrease in the formation of free radicals. As the effect of EGb 761 on functional recovery cannot be explained by the presence of GkB, the beneficial action of the extract on myocardial stunning likely involves complementary effects of both its non-ginkgolide and ginkgolide constituents.

Animals↗

PubMed2002

An optimal experimental design for the development of preservative heart solutions.

BACKGROUND: The aim of this study was to determine the optimal composition of a new medium for long-term hypothermic heart preservation. METHODS: The independent effects of 19 compounds were evaluated using an in vitro porcine model. Tissue viability was assessed by measuring the reduction of methyltetrazolium salt, oxygen consumption and energetic compound levels on myocardial biopsies after 24-, 48- or 72-hour incubation periods. Screening of several compounds at two concentrations was performed to greatly reduce the number of experiments. RESULTS: Pyruvate, aspartic acid, chlorpromazine and polyethylene glycol displayed protective properties, whereas calcium (2 mmol/liter), nifedipine, mannitol, magnesium (16 mmol/liter) and reduced glutathione showed deleterious effects. On the basis of these data, the composition of a new preservation solution (Group 1, n = 6) was compared with St Thomas solution (Group II, n = 6) in an isolated, 24-hour pig heart preservation model. During reperfusion, left ventricular developed pressure and coronary blood flow were significantly higher (p <.01) in Group I, suggesting better preservation. CONCLUSIONS: Our technique allows for rapid and efficient screening of many compounds currently used in the composition of preservation solutions for cardiac surgery.

Animals↗

PubMed2002

Preservation of ischemia and isoflurane-induced preconditioning after brain death in rabbit hearts.

We sought to determine whether brain death-induced catecholamine release preconditions the heart, and if not, whether it precludes further protection by repetitive ischemia or isoflurane. Anesthetized rabbits underwent 30 min of coronary occlusion and 4 h of reperfusion. The effect on infarct size of either no intervention (controls), ischemic preconditioning (IPC), or isoflurane inhalation (Iso) was evaluated with or without previous brain death (BD) induced by subdural balloon inflation. Plasma catecholamine levels were measured at several time points. Although it dramatically increase plasma catecholamine levels, BD failed to reduce infarct size that averaged 0.49 +/- 0.34 without BD versus 0.45 +/- 0.27 g with BD. IPC and Iso, alone as well as after BD, significantly reduced infarct size that averaged 0.11 +/- 0.04, 0.21 +/- 0.15, 0.10 +/- 0.09, and 0.22 +/- 0.10 g in IPC, Iso, BD + IPC, and BD + Iso groups, respectively (means +/- SD, P < 0.05 vs. controls). BD-induced catecholamines "storm" does not precondition the rabbit heart that however retains the ability to be protected by repetition of brief ischemia or isoflurane inhalation.

Anesthetics, Inhalation↗