Biomedical subjects

Emmeran Gams

Publications and source records attributed to Emmeran Gams.

4 recordsLinked to original sources

PubMed2003

Effects of direct mechanical ventricular assistance on regional myocardial function in an animal model of acute heart failure.

Direct mechanical ventricular assistance (DMVA) improves hemodynamics in failing hearts without complications associated with a blood/device interface. Epicardial Doppler displacement transducers provide exact measurements of tissue displacement and regional myocardial function (RMF). An in vivo porcine model of acute heart failure was used to examine the effects of DMVA on RMF, which have not been reported before. In 8 anesthetized pigs cardiac output (CO), left ventricular pressure (LVP), aortic blood pressure (BP), systolic contractility (dp/dt max), and systolic wall thickening fraction (WT%) were measured. A multichamber pump system (IMPS) surrounding the left ventricle was implanted and the measurements were repeated. Then acute heart failure was induced by beta-blockade, resulting in a decline of all measured parameters to more than 30% compared to baseline values. In the further course of the experiment, repeated measurements were taken at several intervals with and without DMVA by the implanted device. The IMPS implantation caused no significant hemodynamic changes. Under conditions of acute heart failure DMVA improved LVP (46 +/- 7 to 81 +/- 9 mm Hg), dp/dt max (532 +/- 207 to 744 +/- 361 mm Hg/s), CO (1.5 +/- 0.1 to 1.9 +/- 0.5 L/min) and WT% (19 +/- 7% to 32 +/- 8%). Left ventricular myocardium not directly assisted by external pressure application showed improved regional myocardial function during DMVA. We conclude that DMVA is capable of improving hemodynamics due to extrinsic compression. It also enhances the remaining myocardial function of the failing heart, which might lead to myocardial recovery. These synergistic effects are considered responsible for the high efficiency shown by the IMPS in previous investigations.

Acute Disease↗

PubMed2002

[The isolated rabbit heart: comparison between five different modifications].

BACKGROUND: The isolated heart as an experimental model has been firmly established for more than 100 years. MATERIAL AND METHODS: In this study, five modifications are compared: 1. modified Langendorff apparatus (LA) with modified Krebs-Henseleit (KH) solution a) not containing bovine serum albumin (BSA; n = 13) and b) containing BSA (n = 16), 2. LA with KH solution containing BSH and bovine erythrocytes (n = 14), 3. LA with support rabbit (n = 6), and 4. "working heart" preparation with KH solution, BSA and bovine erythrocytes (n = 16). In the latter modification, no balloon was inserted into the left ventricular cavity, i. e., systemic and coronary circuits were not separated from each other. After completion of the preparation and 20-min stabilization, hemodynamic and metabolic data were assessed while the hearts were contracting in the ejecting mode. Thereafter, protocols for different studies were performed that are not presented here. However, the stability of the modifications within their individual protocols is reported. RESULTS: The results suggest that hearts perfused with KH solution are well suited for short protocols. In spite of the additional costs and time, blood perfusion is required for long-lasting protocols or if changes in coronary flow are to be investigated. CONCLUSIONS: The working heart exhibits both the best function and stability at a relatively low experimental expenditure. Yet, it is not suited for studies where perfusion pressure needs to be changed independent of arterial pressure.

Animals↗

PubMed2002

Preconditioning: myocardial function and energetics during coronary hypoperfusion and reperfusion.

BACKGROUND: Ischemic preconditioning (IP) is gaining more acceptance as a protective method in beating heart surgery. Yet it remains controversial whether preconditioning can attenuate myocardial dysfunction during reperfusion after severe coronary hypoperfusion. We examined this issue and also the issue of whether this protection is mediated by adenosine A1 receptors. METHODS: In isolated, blood-perfused rabbit hearts, the effects of IP (3 minutes of no flow ischemia and 8 minutes of reperfusion) during 30 minutes of coronary hypoperfusion and 60 minutes of reperfusion were investigated. In two groups (n = 8 each) with and without (control group) preconditioning, ventricular function was assessed by load-insensitive measures: slope of the end-systolic pressure-volume relation (Emax), slope of the stroke work/end-diastolic volume relation (Mw), and end-diastolic pressure-volume relation. External efficiency was calculated, and contractile efficiency was assessed using the reciprocal of the myocardial oxygen consumption-pressure-volume area relationship. To investigate the possible role of adenosine, the adenosine A1 receptor antagonist DPCPX (2.5 micromol/L) was administered before preconditioning in a third group (n = 7). RESULTS: The effects of hypoperfusion on systolic function, diastolic function (dP/dtmin, end-diastolic pressure-volume relation), external efficiency, and contractile efficiency were similar in both the IP and control groups. Lactate efflux was significantly reduced after preconditioning (p = 0.02). During reperfusion, recovery of systolic function and coronary flow were significantly improved in the IP group compared with controls: aortic flow, 85% versus 63% (p = 0.01); dP/dtmax, 91% versus 67% (p = 0.001); pressure-volume area, 97% versus 68% (p = 0.01); Emax, 74% versus 62% (p = 0.03); and Mw, 94% versus 84% (p = 0.04). Release of creatine kinase was reduced in the IP group, 9.6 +/- 1.3 U x 5 min(-1) x 100 g(-1) wet weight, versus controls, 12.7 +/- 2.7 U x 5 min(-1) x 100 g(-1) wet weight (p = 0.04). During reperfusion, contractile efficiency (p = 0.03) and external efficiency (p = 0.02) recovered better in preconditioned than in untreated hearts. Recovery was less pronounced in the DPCPX group compared with the IP group (p, not significant). CONCLUSIONS: The results, derived from load-insensitive measures, confirm that IP provides protection after episodes of severe hypoperfusion by attenuating systolic dysfunction without improving diastolic dysfunction and reduces the severity of anaerobic metabolism as well as ischemic injury. Contractile efficiency and external efficiency both indicate improved energetics after IP (oxygen utilization by the contractile apparatus). The protective effect, at least in part, is mediated by adenosine A1 receptors.

Animals↗

PubMed2002

Flow cytometry analysis of platelet cyclooxygenase-2 expression: induction of platelet cyclooxygenase-2 in patients undergoing coronary artery bypass grafting.

There are conflicting reports about the expression of cyclooxygenase (COX)-2 in human platelets. The present study describes a flow cytometric method for the measurement of platelet COX. Both COX-1 and COX-2 were shown to be expressed in platelets from patients undergoing a coronary artery bypass graft. There was a significant increase in COX-2 expression at day 5 as compared with pre-surgery values (mean fluorescence 12.31 +/- 0.88 versus 9.15 +/- 0.88; means +/- SEM, n = 7, P < 0.05), whereas COX-1 levels did not change (13.45 +/- 1.11 versus 12.38 +/- 1.41; n = 7, P > 0.05).

Aspirin↗