From Heartwire — a professional news service of WebMD

July 1, 2008 — New recommendations on antithrombotic and thrombolytic therapy from the American College of Chest Physicians (ACCP) have been published as a supplement to the June issue of Chest [1]. Guidelines panel chair Dr Jack Hirsh (Henderson Research Centre, Hamilton, ON) told heartwire that the 900-page document contains the most comprehensive advice to date on the prevention, treatment, and long-term management of thrombotic disorders.

"We've markedly increased the number of non-North American participants, so the recommendations are more international. The process of evaluation has improved dramatically — it's much more rigorous, with panelists for each chapter developing questions sent out to an evidenced-based center, which then performed a literature search. Tables of all the clinical trials that have been done for every single clinical condition are included. The review process has changed too, with each chapter and the manuscript as a whole reviewed by two independent people," he explained.

Hirsh said it is impossible to cover all the subjects discussed in the new guidelines, which consist of 22 chapters, but a good starting point is the almost 40-page-long executive summary. For heartwire , he tried to pick out some of the most significant changes from previous guidelines that are of relevance to cardiologists.

First-ever chapter on perioperative management

For the first time, the guidelines dedicate a full chapter (chapter 10) to the perioperative management of patients on long-term antithrombotic therapy who require surgery or other invasive procedures, Hirsh said.

Unfortunately, he explained, the previous recommendations for the most appropriate approach to the pre- and perioperative management of such patients was "based on one randomized trial." People might be taking warfarin, aspirin, or clopidogrel, and doctors need guidance on whether or not to stop such therapies before surgery.

The recommendations offer a couple of options for warfarin: lowering the dose for simple procedures, such as cataract surgery; or stopping therapy altogether around 5 days before surgery and instead using low-molecular-weight heparins (LMWHs), or heparin, for coverage, Hirsh said. In certain circumstances, warfarin can be continued until 48 hours before surgery, when patients should be given a low dose of vitamin K. For aspirin, the recommendation is normally to continue therapy, he said. For clopidogrel, it is usually stopped 5 to 7 days before surgery.

Rather than going into too much detail, Hirsh said he wanted to stress that the guidelines provide physicians with a rationale based on the likelihood of a thromboembolic event in any individual person weighed against the risk of bleeding when antithrombotic therapy is stopped before surgery.

HIT: Heparin can still be used for bypass surgery

Another chapter of relevance to cardiologists is the one on the treatment and prevention of heparin-induced thrombocytopenia (HIT), Hirsh noted. "If someone has had an issue with HIT and requires bypass surgery, what do you use as anticoagulation during bypass?"

He explained that any anticoagulant, apart from heparin, can be problematic for conventional on-pump bypass surgery because the risk of bleeding is greater, experience is limited, and the procedure is much riskier.

Hirsh said that in someone who has had HIT but who now has a negative HIT antibody level, "it's safe to use heparin for bypass surgery because it is only used short-term and is cleared very quickly. Physicians are uncomfortable with this because of medico-legal implications, but it is perfectly rational."

Another important issue for physicians to understand is that the enzyme-linked immunosorbent assay (ELIZA) test normally used to diagnose HIT "is commonly falsely positive after surgery," Hirsh explained. It is important for doctors to remember that falling platelet counts continue to occur four to five days after heparin, he noted "and if you did this ELIZA test on all patients after bypass surgery, 20% to 30% would be positive. It creates almost as much harm as good."

An alternative is to use another test — a serotonin-release test — "which is much more specific but not always available," he said.

Prevention of venous thromboembolism; not much new in AF

Hirsh said that research has revealed that certain high-risk medical patients and nonorthopedic surgical patients are not getting venous thromboembolism (VTE) prophylaxis, "when there is good evidence that it works. Often it's not been given because people just don't think about it."

Thus, the guidelines recommend that hospitals adopt an opt-out policy when it comes to VTE prevention, in which all relevant patients are routinely given it unless doctors remove it because they think it is not warranted.

The recommendations also add more about the surgical management of VTE, he noted, and advice on the duration of anticoagulant therapy following VTE.

For atrial fibrillation (AF), there is "not a lot that is new," Hirsh said. The guidelines make treatment recommendations on the basis of low-, moderate-, and-high risk AF. Hirsh said that one of the problems with AF is that, despite "an enormous amount of evidence" indicating the benefits of warfarin, it is "grossly underutilized" for those at moderate or high risk, particularly by family practitioners.

On a related note, he said that there are "more and more randomized clinical trials that have been published that demonstrate the benefits of computer-assisted INR [international normalized ratio] monitoring for warfarin therapy, showing it is superior to physician monitoring, with various nomograms for dose adjustment being more effective than decisions made 'off-the-cuff'."

Other chapters of relevance

Other chapters in the guidelines of relevance to cardiologists include antithrombotic therapy for non-ST-segment elevation acute coronary syndrome, acute ST-segment elevation myocardial infarction, primary and secondary prevention of coronary artery disease, and valvular and structural heart disease.

There are also chapters on antithrombotic therapy for peripheral artery occlusive disease, on antithrombotic and thrombolytic therapy for ischemic stroke, and on pregnancy. The information on the use of antithrombotics in children and neonates has been expanded.

"Care for children with major cardiac problems has improved dramatically," Hirsh said. "But thrombosis remains a major cause of secondary complications for these children, so effective antithrombotic therapy is critical."

Source

1. Hirsh J, Guyatt G, Albers GW, et al. American College of Chest Physicians evidence-based clinical practice guidelines (8th edition). Chest 2008;133(6 suppl):110S-968S. Available at: http://www.chestnet.org/education/hsp/guidelinesAT8.php.

The complete contents of Heartwire , a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.

Clinical Context

Pearls for Practice

• Pregnant women should ideally stop taking VKAs before 6 weeks of fetal gestation, but some pregnant women with certain types of mechanical heart valves should continue VKAs because alternative anticoagulants may be less effective to prevent stroke and valve thrombosis. For other pregnant women, LMWH or UFH should be substituted for VKAs. Until the underlying causes are determined, children with AIS should initially receive antithrombotic treatment, followed by maintenance therapy to prevent long-term recurrence.
• To minimize surgical bleeding, most patients must temporarily discontinue antithrombotic treatment immediately before and during surgery. Because discontinuing antithrombotic treatment can increase the risk for a thromboembolic event, however, this risk must be weighed against the risk for bleeding when deciding whether to interrupt antithrombotic therapy just before surgery. Routine use of thromboprophylaxis is recommended for patients undergoing major general, gynecologic, or orthopaedic surgery as well as bariatric and coronary artery bypass surgery.

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