Dr. Flaker is also a member of the American College of Cardiology’s (ACC’s) Anticoagulation Initiative Work Group – a multidisciplinary quality effort to address gaps in knowledge and improve the quality of anticoagulation care, particularly given an increasing number of new anticoagulant treatment options entering the market. Dr. Flaker presents the cardiologist’s perspective on managing this condition.
How would hematologists and cardiologists work together to manage atrial fibrillation? As a cardiologist, when would you consult a hematologist?
As I’m sure hematologists know, anticoagulation options have expanded a great deal recently. Cardiologists and primary-care physicians now often prescribe newer oral anticoagulants, such as direct thrombin inhibitors and factor Xa inhibitors, to prevent clotting disorders. While we don’t necessarily consult our hematology colleagues before we administer these medications, we definitely consult them after giving these medications – particularly if bleeding problems or complications with the anticoagulation occur.
How do you manage those types of bleeding events?
First of all, hematologists are certainly aware of these newer agents, and many institutions have probably contacted their hematologists for advice on how we correct bleeding problems with these agents. Hematologists have very good relationships with the blood bank, so cardiologists really rely on hematologists to ensure that reversal agents are readily available through the blood bank – and also to advise on their appropriate use.
In the past, warfarin was the most commonly prescribed anticoagulant, and its reversal agents (vitamin K and fresh frozen plasma) have been fairly well established. Now, with the newer anticoagulants, more complex agents are needed for their reversal, such as prothrombin complex concentrate or factor VII replacement. These can be very expensive and may not be readily available in some blood banks – that is where we need the hematologists to help us out.
It should be stated, too, that some of the newer agents do not yet have a reversal agent, and there is no antidote to quickly stop bleeding. So, we also ask hematologists to stay abreast of this developing area to ensure that we will have access to the appropriate tools when they become available.
How has the role of laboratory monitoring changed with these newer anticoagulants?
With warfarin and other “old-fashioned” anticoagulants that have narrow therapeutic windows, we have become accustomed to the need for regular monitoring. Every four weeks or so, a patient would have a blood test to check if they were within their target international normalized ratio (INR) range. Out of range, a patient could be susceptible to stroke, so regular monitoring reassures us that they are within a healthy range.
Newer agents now hold the promise of a wider therapeutic window, meaning we have a little more wiggle room. Patients do not need to be monitored regularly; however, I think the field is moving towards periodic measurement. There are some circumstances where knowing the amount of anticoagulant effect would be clinically helpful, including a bleeding patient, a patient scheduled for a surgical procedure, or when we have concerns about a patient’s compliance.
A number of assays are being developed that will give the clinician that capability. Some are available in hospitals on a research basis, but overall, they are hard to obtain, take a long time to produce results, and are expensive. Different assays are required for different anticoagulants, so the process has yet to be standardized, as well.
When does a patient with AF need to be admitted to the hospital?
The usual indication for a hospitalization is when a patient with AF is experiencing a rapid heartbeat, symptoms of chest pain or shortness of breath, or evidence of cardiac decompensation.
How do a patient’s embolic and hemorrhagic risk factors impact the type of therapy you choose?
That’s a highly individualized decision for each patient. A number of factors come into play to predict a patient at risk for bleeding. Many of these factors also predict thromboembolic stroke risk. We might balance those risk factors – those for stroke on one hand and those for bleeding on the other. If we add the scores up and they are unbalanced, we might not prescribe anticoagulation therapy.
Generally, though, most U.S. physicians do not use the bleeding risk score to rule out anticoagulation. We are certainly aware of it, but we do not use it to preclude a patient from receiving anticoagulation therapy.
The bottom line is that, as our population gets older, AF becomes more common, and so does their risk for bleeding events and thrombosis. Our task is to provide them with safe and effective anticoagulation to prevent clotting disorders, in a way that we can minimize damage if bleeding or complication occurs.