Navigation/Menü: Links auf weitere Seiten dieser Website
|Aspekte der Myocardprotektion und Cardioplegie im klinischen Vergleich|
|Main title||Aspekte der Myocardprotektion und Cardioplegie im klinischen Vergleich|
|Title variations||Aspects of Myocardial Protection and Cardioplegia in Clinical Comparison|
Place of birth: Aachen
|1. Referee||Prof. Dr.med. Hermann Reichenspurner|
|Further Referee(s)||Prof. Dr.med. Hans-Hinrich Sievers|
|Keywords||Myocardial Protection, Cardioplegia, Bloodcardioplegia, Cardiac Surgery|
|Classification (DDC)||610 Medical sciences; Medicine|
|Summary||Concepts for thoracic organ preservation involve a number of physical and chemical entities which act individually and in combination on the heart and lungs. This professorial dissertation presents evaluations of different cardioplegic concepts and examines the influence of temperature, hematocrit, calcium and the addition of L-arginin, as well as the direction and route of delivery of the preservation solution, on the protection of the lungs when organs are harvested for transplantation. It also considers the geometry of the left ventricle and its influence on the contractility of the heart and presents a clinical study comparing two cardioplegic concepts applied in patients suffering from cardiac ischemia with emergency indication for rapid coronary bypass revascularization.
A good cardioplegic concept is characterized by precise control of cardiac arrest, reliable re-instigation of the heartbeat and effective cardioprotection of the myocytes and endothelial cells from ischemia and the consequences of reperfusion and reoxygenation subsequent to hypoxemia.
Normothermia without ischemia or hypoxemia allows the continuation of cellular metabolism and facilitates metabolic repair mechanisms. Hypothermia reduces the metabolism, decreases the oxygen requirement of cells and can protect the heart against the consequences of ischemia. In an experimental study we were able to demonstrate that continuous coronary perfusion with cold blood results in ongoing cardioplegic arrest and achieves good cardiac protection.
The hematocrit is mainly defined by the amount of hemoglobin (except when the blood is altered by oncologically malignant composition). Hemoglobin transports the largest proportion of oxygen in the blood stream and is one of the pillars of the puffer capacity of the blood. On extracorporeal circulation as little hemodilution as possible is important, with the aim of not decreasing the hematocrit. In our experimental study we demonstrated that a low hematocrit of 20–25 % during continuous artificial coronary perfusion nourishes the myocardium and is advantageous for cardioplegic arrest, in opposition to a high hematocrit of 40–45 %, which impairs cardiac function and promotes the development of cardiac edema.
The cytoplasmatic content of calcium in combination with the other electrolytes enables the undulating contraction and relaxation of the cardiomyocytes. Cytoplasmatic overloading with calcium is the result in the etiology of cellular injury of many causes such as ischemia/reperfusion and reoxygenation after hypoxemia. This can lead to temporary hypercontraction, the development of stunning, or the formation of a stone heart. We demonstrated experimentally that hypocalcemia during reoxygenation following hypoxemia is advantageous in curbing damage to the heart and lungs, resulting in improved cardiac function and reduction of increased vascular resistance in the pulmonary vascular bed.
The addition of amino acids to a blood cardioplegic solution augments its protective power. In particular glutamate and aspartate as contents of a blood cardioplegic solution support the metabolic and functional recovery of cardiomyocytes from ischemia/reperfusion. In an experimental study concerning cardiac ischemia, reperfusion and protection by blood cardioplegia we identified a gap in the protection for the endothelium. The addition of L-arginin to blood or to blood cardioplegia during the phase of reperfusion subsequent to ischemia protects cardiomyocytes and endothelial cells and improves their metabolic and functional recovery.
Measures for organ preservation mainly determine the success of lung transplantation with regard to initial gas exchange, healing of the bronchus anastomoses and inhibition of the development of bronchiolitis obliterans. In order to achieve good organ preservation, complete perfusion of the lung parenchyma and bronchial tissue with the preservation solution is important. As vascular bed the pulmonary arteries, the pulmonary veins and the bronchial arteries are available. In an experimental study with different routes of delivery we demonstrated that the retrograde route of perfusion via the pulmonary veins leads to better perfusion of the lung and bronchial tissue than the antegrade route via the pulmonary arteries, and that atelectasis impairs perfusion of the lung parenchyma.
The geometry of the left ventricle influences its pumping function. Enlargement of the left ventricle due to dilatation or the development of an aneurysm leads to spherical distension. In a further experimental study we demonstrated that spherical distension reduces the elasticity and contractility of the left ventricle, and that the subsequent reversal of the spherical distension and the restoration of an elliptical shape, with physiological diameter of the ventricle, improves the left ventricular elasticity and contractility.
In a comparative clinical study the protective power of two different cardioplegic concepts was investigated. Patients with the indication for emergency coronary revascularization due to ischemic jeopardization of the heart were randomly divided into two groups in which different cardioplegic concepts were applied. One group of patients was operated on using crystalloid cardioplegia with Kirsch/HAES solution and the second group with blood cardioplegia following Buckberg’s concept. Both cardioplegic concepts were efficient in making the hearts stop beating and relax. Patients who received Buckberg’s blood cardioplegia performed better postoperatively than those with Kirsch/HAES solution in terms of regional contractility, expression of cardiac enzymes and signals for ischemia on the electrocardiogram. This difference was larger for patients in cardiogenic shock. The choice of cardioplegia did not show a sharp difference in clinical outcome between the two groups of patients: mortality, duration of intensive care unit stay and the number of days on mechanical ventilation were without significant differences between the two groups, but with a tendency towards faster recovery in the group operated on using Buckberg’s blood cardioplegia. Patients of the Buckberg’s blood cardioplegia group without signs of cardiac shock required significantly less hemodynamic support with catecholamines and intraaortic balloon counterpulsation. Also, significantly fewer blood transfusions were administered after Buckberg’s blood cardioplegia.
PDF-Datei von FUDISS_thesis_000000021539
|FU Department||Department of Medicine - Charité - University Medicine Berlin|
|Year of publication||2011|
|Document type||Habilitation treatise|
|Date of defense||2011-01-24|
|Created at||2011-03-03 : 11:11:04|
|Last changed||2011-03-03 : 11:14:16|