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R Lerch

Publications and source records attributed to R Lerch.

64 records · Page 4Linked to original sources
PubMed1977

[Myocardial function and metabolism during local coronary flow reduction].

In 6 open chest dogs, regional myocardial function und metabolic changes (ATP, creatine phosphate, lactate) were studied during coronary flow reduction in LAD by ultrasonic dimension gauges and transmural biopsies. After reduction of the perfusion pressure from 108 to 50 mm Hg the ischemic segment showed a marked dyskinesis: the enddiastolic segment length increased by 7%, and segment shortening and segment stroke work decreased by 22% and 63% respectively. Left ventricular (LV) enddiastolic pressure rose from 5 to 8 mm Hg (p less than 0.05). Heart rate, LV systolic pressure, LV max dP/dt and Vpm did not change significantly.

Adenosine Triphosphate↗
PubMed1976

[Effect of coronary flow reduction on the coronary flow distribution, the myocardial metabolism and left ventricular hemodynamics].

Myocardial blood flow, left ventricular performance, regional myocardial metabolites (ATP, CrP, lactate) and a-v differences of oxygen, lactate and pyruvate were determined in 6 open chest dogs with cannulated left coronary artery. A mean flow reduction from 92 to 43 ml/min/100 g heart weight resulted in marked heart failure accompanied by extensive flow reduction to the endocard with nearly 10 fold increase of lactate and a decrease of CrP content to 50% of control. In contrast, flow and metabolic parameters of the epicardial part changed only slightly. Furthermore, the DPTI/SPTI-ratio showed a good correlation with the subendocardial CrP content (r = 0.93, p less than 0.01).

Adenosine Triphosphate↗
PubMedDate not supplied

Oxidative substrate metabolism during postischemic reperfusion.

Myocardial reperfusion occurs in a number of clinical conditions which include unstable angina, thrombolytic therapy or percutaneous transluminal angioplasty during evolving myocardial infarction and cardioplegic arrest during cardiac surgery. The transition from the ischemic to the postischemic state of the myocyte is associated with a number of functional, morphological, ionic and metabolic alterations. This article reviews available information on metabolism of glucose and palmitate in postischemic myocardium. Overall oxidative metabolic rate recovers rapidly after the onset of reperfusion. In some studies myocardial oxygen consumption during early reperfusion has been disproportionately high compared to contractile function. Oxygen consumption may recover transiently even in myocardium that undergoes irreversible injury. There exists some evidence indicating that cytoplasmic calcium overload may lead to increased energy expenditure during reperfusion. The relative contribution of fatty acids and glucose to oxidative metabolism during the first hour of reperfusion has been found either to be unchanged or to exhibit a shift toward increased glucose oxidation. Several observations suggest that glucose utilization may be essential during reperfusion for the survival of the myocardium.

Animals↗
PubMedDate not supplied

Effect of magnesium administered during postischemic reperfusion on myocardial oxidative metabolism in isolated rat hearts.

To determine the effect of magnesium on myocardial function and oxidative metabolism after reperfusion, isolated rat hearts perfused retrogradely with erythrocyte-enriched medium (0.4 mM palmitate bound to 0.4 mM albumin, 11 mM glucose) were subjected to 60 minutes of no-flow ischemia followed by 60 minutes of reperfusion. Untreated postischemic hearts exhibited after 15 minutes of reperfusion recovery of myocardial oxygen consumption to 65% of the preischemic value despite persistent depression of left ventricular isovolumic pressure development to 21%. Magnesium (15 mM) administered during the initial 30 minutes of reperfusion reduced myocardial oxygen consumption of reperfuse myocardium by 35%. Oxidation of [1-14C]palmitate was slightly more reduced (-55%) than oxidation of [U-14C]glucose (-42%). Magnesium did not influence ultimate recovery of contractile function and cumulative myocardial release of creatine kinase. Thus, 15 mM magnesium administered during reperfusion elicited a reduction of oxidative metabolism. However, magnesium did not modify myocardial injury.

Animals↗
PubMedDate not supplied

Epinephrine-stimulated contractile and metabolic reserve in postischemic rat myocardium.

Recovery of contractile function and of fatty acid oxidation may be delayed in viable postischemic myocardium. To determine whether a metabolic reserve is preserved after reperfusion of reversibly injured myocardium, we studied the effect of epinephrine on myocardial fatty acid oxidation in isolated rat hearts perfused retrogradely with erythrocyte enriched buffer containing albumin 0.4 mM, palmitate 0.4 mM, and glucose 11 mM. Hearts were subjected to 60 min of low-flow ischemia (5% of control flow) followed by 60 min of reperfusion. Five minutes following the onset of reperfusion, developed left ventricular pressure (DLVP) and oxidation of palmitate were reduced to 53% (p less than 0.01) and 46% (p less than 0.01), respectively, of values measured in nonischemic control hearts. Subsequently, DLVP and oxidation of palmitate gradually recovered to 78% (NS) and 91% (NS) by 60 min of reperfusion. Epinephrine 5.10(-1) M elicited an immediate stimulation of both contractile function and palmitate oxidation. Early after reperfusion stimulated DLVP and palmitate oxidation were still lower compared to values measured in control hearts exposed to the same concentration of epinephrine. Later than 15 min after the onset of reperfusion the response of DLVP and of palmitate oxidation to epinephrine no longer differed between control and reperfused hearts. These results indicate that viable postischemic myocardium exhibits a remarkable oxidative metabolic reserve. The observation provides further evidence for the view that impairment of myocardial energy production is not responsible for contractile dysfunction early after reperfusion.

Animals↗
PubMedDate not supplied

Detection and quantification of valvular heart disease with dynamic cardiac MR imaging.

Magnetic resonance (MR) imaging is rapidly gaining acceptance as an accurate, reproducible, noninvasive method for optimal assessment of structural and functional parameters in patients with valvular heart disease. The severity of valvular regurgitation can be evaluated with cine gradient-echo MR imaging, which allows measurement of the area of the signal void corresponding to the abnormal flow jet. Alternatively, this modality can be used to obtain ventricular volumetric measurements and calculate the regurgitant fraction, or velocity-encoded cine (VEC) MR imaging can be used to quantify regurgitant blood flow. The severity of valvular stenosis can be determined by evaluating the flow jet and associated findings with either modality or by using VEC MR imaging to calculate the transvalvular pressure gradient and valve area. Dynamic MR imaging allows accurate assessment of ventricular function and comprehensive evaluation of pathophysiologic changes. In addition, good interstudy reproducibility suggests a role for VEC MR imaging in assessing the effects of therapeutic intervention and monitoring regurgitant fraction, thereby helping in surgical planning and the prevention of ventricular dysfunction. With greater cost-effectiveness and the increasing availability of new hardware and more advanced techniques, MR imaging will become a routine procedure in valvular heart disease.

Blood Flow Velocity↗
PubMedDate not supplied

Hemodynamic comparison of Medtronic intact bioprostheses and bileaflet mechanical prostheses in aortic position.

Hemodynamic properties of both bioprostheses and mechanical valves have improved over the years, however, direct comparison between second-generation porcine and bileaflet valves is rare. Therefore, by the mean of Doppler echocardiography, we determined hemodynamic performances in 45 patients with Medtronic Intact bioprostheses in the aortic position and in 67 patients with bileaflet mechanical valves. Differences in pressure gradients between the two groups were essentially attributable to differences in annulus size. Indeed when the transvalvular gradient was stratified according to annulus size, mean values were no longer significantly different between Medtronic Intact porcine valves and bileaflet mechanical valves for each annulus size. In conclusion, Medtronic Intact bioprostheses in the aortic position exhibit similar hemodynamic characteristics compared to bileaflet mechanical valves.

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