Conclusions
This interesting study demonstrates that the use of fixed dose, unmonitored, subcutaneous unfractionated heparin in twice daily dosing is non-inferior to treatment with different kinds of LMW heparin. The authors have also analyzed the cost difference, which, at existing U.S. pricing, would be in the vicinity of $675 for the six-day treatment of an 80-kg patient. Though more data is needed on patients with special considerations such as renal failure, the results, which support non-inferiority and cite a major cost advantage, merit further studies to validate these conclusions and to further evaluate this approach in patient populations with special considerations.
Non-Invasive Testing Prior to Vascular Surgery
Poldermans D, Bax JJ, Schouten O, et al. Should major vascular surgery be delayed because of preoperative cardiac testing in intermediate-risk patients receiving beta-blocker therapy with tight heart rate control? J Am Coll Cardiol. 2006 Sep 5;48(5):964-969.
Background
Current guidelines from the AHA and the American College of Cardiology (ACC) recommend non-invasive testing for patients scheduled for major vascular surgery as part of the pre-operative work-up if they have clinical factors suggestive of increased cardiac risk. The study was performed to show that no testing combined with aggressive beta blockade is not inferior in comparison to non-invasive testing for patients in the intermediate risk group who are preparing to undergo major vascular surgery. Testing often results in delays that can result in poor outcomes; additionally, invasive intervention based upon non-invasive test results has not been clearly shown to add any benefit to the eventual outcome of the patient.
Methods
The study was conducted at five clinical centers in Europe and Brazil, where 1,476 patients undergoing elective open abdominal aortic or infrainguinal arterial reconstruction were enrolled. The design was a randomized, controlled, non-inferiority trial with the outcome assessors blinded. Inclusion criteria consisted of age older than 70, angina pectoris, prior myocardial infarction (MI), compensated or history of congestive heart failure, diabetes mellitus, renal dysfunction and prior stroke, or transient ischemic attack. Patients with one or two risk factors were labeled intermediate risk and were randomized to receive either just beta-blocker therapy or non-invasive testing with dobutamine echocardiography or dobutamine or dipyridamole perfusion scintigraphy.
Patients with limited or no ischemia were referred for surgery with beta-blocker therapy. In patients with extensive ischemia—five ischemic segments or more—coronary angiography and revascularization were performed if the main surgery could be delayed. Beta-blocker therapy was instituted in all patients, with a goal heart rate of 60-65. The beta-blocker therapy was continued postoperatively. IV metoprolol was used in the ICU if a patient could not take drugs orally. Primary endpoints were a combination of cardiac death and nonfatal MI at 30 days and two years.
Results
Of the 770 patients classified as intermediate risk, 386 received cardiac testing and 384 patients were not tested. There were no significant differences in the presence of ischemic heart disease in the two subsets. The time gap between screening to vascular surgery was 34 days (seven to 88 days) in the no testing group, compared with 53 days (1,321 days) in the testing group (P<0.001). There was no difference in the composite endpoints—either at 30 days or at two years—for the two groups.
Conclusions
This excellent study shows that the approach of no screening in patients with intermediate cardiac risk factors before vascular surgery is non-inferior. An interesting point elucidated by the authors in their discussion details why studies designed to achieve a goal heart rate, rather than those based on fixed dose beta-blockers, are ideal to show the benefits of beta blockade in this population subset. The benefit of coronary revascularization for intermediate risk patients with extensive ischemia could not be defined, however; the number was too small to show any significance.