The pericardium and pericardial adhesions in relation to reoperative cardiac surgery

The presence of pericardial adhesions prolongs the operation time and increases the risk of serious damage to the heart and other major vascular structures during restemotomy. The reported incidence of such damage is 2-6%. Pericardial mesothehal cells have regenerative potential and exhibit fibrinolytic activity. The pericardial mésothélium therefore has the capacity to recover following cell loss or damage and has an actual or potential role in the break down of the fibrinous adhesions that serve as the initial scaffolding for the firm collagenous adhesions seen at reoperative surgery. These features of the pericardium may have been underestimated in much of the previous research into pericardial substitution. The studies in this thesis have demonstrated: • That during cardiac surgery there is a significant reduction in the pericardial fibrinolytic activity in comparison to initial activity. The recovery in fibrinolytic activity that occurs towards the end of the surgical procedure and afterwards never reaches the preoperative magnitude. • That during cardiac surgery, simultaneous with the changes in the fibrinolytic activity, increasing pericardial inflammation occurs with a concomitant increase in mesothelial damage. Permanent residual damage is apparent in the reoperative pericardium. • That during the reduction in pericardial fibrinolytic activity the simultaneous plasma tPA activity rises to a peak suggesting that the fall in pericardial fibrinolytic activity is independent of the plasma tPA and haemodilution. • That the cellular content of pericardial fluid is mainly mesothehal which may therefore contribute to mesothehal regeneration and recovery. The pericardial fluid, by virtue of its enzyme content, has the potential to take part in fibrinolytic activity. • That the polyhydroxybutyrate pericardial patch does not confer any obvious short­ term reoperative advantage in calves exposed to CPB surgery. List of Content LIST OF CONTENT Guide to Thesis.2 A bstrac t. 4 List of Content.5 List of Figures.12 List of Tables. 17 Acknowledgements. 18 C h a p te r 1 . 19 Introduction. 20 Pericardial Adhesions In Relation to the Evolution of Cardiac Surgery. 20 An Overview of the Evolution of Cardiac Surgery.21 Early Operative Developments. 21 The Introduction of Cardiopuhnonary Bypass.23 Myocardial Revascularisation.24 The Advent of Coronary Angiography. 25 M yocardial Preservation.26 The Increasing Reoperative Workload. 27 Reasons for Reoperation. 28 Difficulty of Primary closure of the Pericardium.28 Consequence of not closing the Pericardium. 28 List of Content 6 Other untoward affects of Pericardial Adhesions.29 Assessment and Precautions Prior to Restemotomy. 29 Pericardial Morphology.30 Normal Pericardium Macroscopically.30 Parietal Pericardium Microscopically. 31 Visceral Pericardium Microscopically.33 Importance of Mesothelial Cells. 33 Pericardial Fluid. 33 Functions of the Pericardium. 34 Limiting Mobility of the Heart. 34 Limiting Cardiac Dimensions and Preventing Acute Distension 34 Role of the Pericardium In Right Heart Failure In Left Ventricular Disease.35 Role of the Pericardium In Haemodynamic interaction between the left and Right Ventricles. 35 The Fibrinolytic System and The Pericardium. 36 Fibrinolysis.36 Historical N ote. 36 Individual Components of the Fibrinolytic System.39 Plasminogen.39 Plasmin. 39 List o f Content 1 Plasminogen Activators and Plasminogen Activator Inhibitors. 41 Streptokinase. 42 Alpha-2-antiplasmin.42 Alpha-2-M acroglobulin.42 C h a p te r 2 . 44 Review of Previous Work On Adhesions. 45 Adhesions in General.45 Methods Used to Overcome the Problem of Pericardial Adhesions. 47 Pericardial Substitutes. 47 Biologically Derived Materials. 48 Bovine Pericardium. 48 Equine Pericardium. 49 Porcine Pericardium.49 Human Amniotic Membrane. 50 Nondegradable Synthetic Materials.50 T eflon . 50 Hydrogel Composite Pericardial Patch.52 Biodegradable Materials. 52 Modified Pericardial Closure. 54 Pericardial Meshing. 54 List o f Content 8 Trapezoidal F lap. 54 Combined Mediastinal Fat Pad and Anterior Pericardium.55 Other Methods.55 Dextran 7 0 . 55 Pharmacological M anipulation.55 Left Thoracotomy.56 The Influence of Cardiopulmonary Bypass on Adhesion Formation. 56 Factors that Embarrass Pericardial Mésothélium. 56 The Importance of Using CPB as part of the Evaluation of a Pericardial Substitute. 57 C h a p te r 3 : Aim & Thesis D esign . 59 Aim of Study. 60 Thesis D esign.61 Phase One: Clinical Study.61 Phase Two: Chnical study.61 Phase Three: Animal Studies.61 C h a p te r 4: Patients, M aterials & M ethods. 62 Patients.