Protection against ischemia during prolonged balloon inflation by distal coronary perfusion with use of an autoperfusion catheter or Fluosol

Retroinfusion-supported stenting in high-risk patients for percutaneous intervention and bypass surgery: Results of the prospective randomized myoprotect I study

The objective of this study was to assess event-free survival and total treatment costs of retroinfusion-supported stenting in high-risk patients compared to bypass surgery. An increasing number of patients with main-stem and main-stem-equivalent stenosis are treated by stent implantation, which appears to be safe in the short-term follow-up. However, there is a lack of randomized studies comparing conventional bypass surgery with stent implantation, particularly in patients with high risk for both treatments. We here report on the 1-year results of a prospective randomized single-center study in patients with symptomatic main-stem and main-stem-equivalent lesions with substantially increased risk for bypass surgery. Patients where randomized to undergo either percutaneous transluminal coronary angioplasty/stent procedure (n = 23) or bypass surgery (n = 21). Patients randomized to stent implantation were supported by selective pressure-regulated retroinfusion of the anterior cardiac vein during ischemia. Patients of the stent group and the bypass group did not differ in baseline characteristics, including Parsonnet score and quality-of-life score. Twenty-eight-day mortality and 1-year mortality rate as well as quality-of-life scores were similar in both groups. Event-free survival after 1 year was higher in the bypass group (71.4% vs. 52.3%; P = 0.02) due to a lower target lesion revascularization rate. With regard to total treatment costs, however, the stent group compared favorably to the bypass group (9,346 +/- 807 vs. 26,874 +/- 3,985 euro), predominantly as a result of a shorter intensive care and hospital stay. In this first randomized study in high-risk patients for stent implantation and bypass surgery, patients with retroinfusion-supported stent implantation had a similar 1-year outcome and quality of life compared to patients with bypass surgery. Though in the stent group event-free survival was lower and target lesion revascularization rate was higher, retroinfusion-supported stent implantation was associated with substantially lower costs and might be considered as an alternative treatment option in this selected group of high-risk patients.

Oxygen therapeutics (blood substitutes) in cardiac surgery

PURPOSE OF REVIEW

Discuss and summarize recent published literature related to the use of 'blood substitutes' in cardiac surgery patients.

RECENT FINDINGS

Concerns about safety, inventory and the cost of allogenic blood transfusion have led to the continued interest to find an ideal oxygen carrier 'blood substitute' for cardiac surgery patients. Two classes of oxygen therapeutics 'blood substitutes' are being investigated: (1) perfluorocarbons are synthetic fluorinated hydrocarbons which increase dissolved oxygen in the fluid phase and (2) hemoglobin-based oxygen carriers, modified to improve oxygen dissociation properties and side effects profiles of free hemoglobin. Hemoglobin-based oxygen carriers from bovine and human sources are being tested in phase III trials in cardiac surgery patients as well as a variety of other surgical and nonsurgical settings. Recombinant human hemoglobin and encapsulated hemoglobins of any source are emerging. Safety and cost effectiveness are being evaluated for their use as an alternative to blood transfusion or along with other strategies of blood conservation in cardiac surgery.

SUMMARY

One hemoglobin-based oxygen carrier (Hemopure) has been approved for use in humans in South Africa as well as another hemoglobin-based oxygen carrier (Gelenpol) and a perfluorocarbon (Perfluoron) in Russia. Phase III trials in Europe and North America will be concluded very soon. We anticipate seeing one or two products approved in North America and Europe by the year 2003/2004.

Perfusion therapy to reduce myocardial ischemia en route to emergency coronary artery bypass grafting for failed percutaneous transluminal coronary angioplasty

Despite improvements in operator technique, catheter technology, and the development of new devices, emergency coronary artery bypass grafting (CABG) is still required in 1%-4% of attempted catheter based revascularization procedures. Patients who require such emergency CABG after failed percutaneous transluminal coronary angioplasty (PTCA) have worse acute outcomes than those undergoing elective CABG, with a higher incidence of Q wave myocardial infarction (MI) and a higher operative mortality. In patients with otherwise refractory abrupt closure, maintenance of antegrade coronary blood flow using perfusion catheters lessens the incidence of Q wave MI and lowers peak creatinine phosphokinase. Direct maintenance of coronary flow thus appears to provide more definitive control of myocardial ischemia than purely adjunctive measures, such as intra-aortic balloon pumping, cardiopulmonary support, or coronary sinus retroperfusion. Although the recent introduction of coronary stents holds great promise for definitive percutaneous reversal of abrupt closure and a dramatic decrease in the incidence of emergency CABG for failed PTCA, maintenance of antegrade flow via perfusion technology remains the cornerstone of management in reducing the perioperative mortality and morbidity of patients who still require emergency bypass surgery after failed PTCA.

Fluorocarbon emulsions

Perfluorocarbon emulsions have been the topic of intense investigation for many years and presently there are still no absolute indications for their use in clinical practice. The relatively disappointing results of the early clinical studies, as a consequence of using low concentrations of a relatively underdeveloped emulsion, have been responsible for a largely negative impression and it is now essential that the newer second generation emulsions should be judged individually with regard to their efficacy and toxicity under different circumstances. Technological advancement in the fields of chemistry and detergent/emulsifier research will continue and new formulations are being developed which which will require to be tested in models in the laboratory. In the future, this class of drugs will continue to be the topic of intense investigation and their mechanisms of action, which are undoubtedly more complex than the simple carriage of dissolved gases in solution, will be clarified. However, whether fluorocarbon emulsions will ever be used as a 'blood substitute' as was originally anticipated is doubtful.