Posts Tagged ‘atrial fibrillation’
New Tools for Atrial Fibrillation
I have blogged about atrial fibrillation many times as it is a constant feature in the practice of cardiology. An estimated 2.2 million patients in the United States alone have this problem. It has been difficult to prove in some patients and very difficult to follow. The facts are extraordinary.
If you have atrial fibrillation and go out of it by any means, the likelihood is that at one point in time, you will be back in it. If a physician places you on a drug, there is only a 50% chance that it will keep you in normal rhythm. If you have a procedure to terminate it, the range of one year success is variable from 50%-70%. We do not even have a way to figure out what your rhythm or rate control success is on a long term basis.
Until now — Medtronic, a major device company–has released a novel device. A study associated with the device has been published in Circ Arrhythm Electrophysiol. 2010; 3:141-147. This study documents the usefulness of this unique device.
The device records and stores data obtained from the heart without the need for leads into the heart such as a pacemaker would have. It is implanted in a simple procedure under your skin near your heart and is able to sense the electrical activity of your heart without wires into your heart. The procedure takes roughly ten minutes to place the device, and about the same amount of time to remove it. This can be done in an outpatient setting. The device will last up to three years so it provides a long term view of a patient’s atrial fibrillation and whether drug or ablation therapy is working for the patient.
This device also allows the diagnosis of patients who have intermittent symptoms that are virtually impossible to figure out using 24 hour holter monitors. The sensitivity of the device for atrial fibrillation was 96% and it was correct in identifying the problem 85% of the time. This device will also “download” its information wirelessly from a remote location so patients can send reports without going to the doctor’s office and patients can send reports if they sense something that troubles them.
Devices such as this will lead to a new paradigm of treatment for atrial fibrillation, as we can now have long term data which was unable to be obtained previously. This will lead to better treatments and to a better understanding of the disease process. If you cannot study it you can’t make progress, and we now have a tool to help.
A win for a new drug
It’s not often that drug studies are stopped early because of success. Usually they are stopped early because of either a structural problem in the protocol or for reasons of safety. Lately, studies stop because the companies have gone bankrupt.
Apixaban is a drug that we are studying and our study continues in follow-up. A sister study done was stopped because the drug proved significantly more beneficial and it was no longer ethical to proceed.
This drug is one of several in development of a new class of drugs. These compounds are known as factor xa inhibitors. They block the clotting cascade at a different point than Coumadin and are going “head to head” against Coumadin in many studies. One is close to approval in the US and is being presented to the FDA for final approval next month.
The use of these drugs will be felt most in the treatment of atrial fibrillation. As I have blogged about many times, atrial fibrillation is increasing in prevalence as our population grows older and about 10% of people over the age of 80 are affected by it. The big problem with atrial fibrillation is the strokes that occur. If no anticoagulation is given, the risk of stroke is 5% a year. If patients take Coumadin the risk is cut to 1%. It is not perfect. Coumadin however becomes more and more difficult to take as patients get older and comes with many restrictions. These new drugs do not as yet have important drug interactions (I can assure you there will be some) and have no dietary interactions like Coumadin does. The one drawback of the drug is that it must be taken twice a day.
The study reported concerned those patients that can’t or won’t take Coumadin. 5,600 patients received either 5 mg of apixaban or aspirin in varying doses. The study was stopped because, again, aspirin proved not effective in preventing strokes. I should mention that Plavix and the combination of Plavix and aspirin have never been found to be effective either.
So, it will likely be that this drug will be an option for patients who will receive the benefit and sustain fewer side effects than taking Coumadin. This is real progress and this drug is eagerly being awaited by both physicians and patients. It will be a “blockbuster” drug for the company who gets approval first. By the way, a “blockbuster drug” is one that brings in over a billion dollars a year.
High Levels of a Substance Found in Ventricular Myocardium May Lead to Atrial Fibrillation
I have blogged about atrial fibrillation before and now a study arrives, which sheds new light on perhaps a marker of who might develop atrial fibrillation in the future. This study reviewed the data of 5,445 patients followed from 10 to 15 years. The authors used a marker know as BNP.
BNP is a substance found in the ventricular myocardium and since the weight of the left ventricle is so much greater than the right ventricle, it is used as a marker of left ventricular failure. When patients present to the hospital or office with signs of congestive heart failure, such as shortness of breath on exertion or fluid retention one can measure the level of BNP in their blood. The higher the level of BNP the more likely the diagnosis of heart failure is.
This substance is also present in acute coronary syndrome, which is a prelude to myocardial infarctions and is also present in myocardial infarctions. Physicians can measure it and get a sense of how important the attack is based on how high the BNP is. In practice, BNP is measured as NT-proBNP.
Past studies have used the Framingham Heart Study, which I have blogged about in the past and would actually be the subject of a long book. Elevated levels of BNP were found to be predictive but only 68 subjects were found. This study, the Cardiovascular Health Study Circ 2009; 120:1768-1774 utilized 5,445 patients. There were 1,126 cases of atrial fibrillation. Among those with the highest levels of BNP, there was a fourfold increase in the risk of atrial fibrillation compared to the lowest levels.
This study found that BNP was the strongest predictor of atrial fibrillation in comparison to other historic variables such as age, sex, medication use, blood pressure, echocardiographic variables, diabetes and heart failure.
Having a marker that may predict atrial fibrillation would allow us to aggressively treat those patients in an attempt to alter the disease course. I am sure that these studies are in progress or being planned given the expected explosion of these cases as the population continues to age.
The War Against Atrial Fibrillation
The care of patients with atrial fibrillation is complicated by the use of warfarin. Although it has no side effects, it needs to be stopped for procedures, it is hard to manage, and there are significant drug/drug and drug/food interactions. Life-threatening bleeding can occur if the levels are high and stroke can occur if the levels are too low.
Even though warfarin prevents 64% of the strokes in those with atrial fibrillation, it is prescribed to only two-thirds of the appropriate candidates. In real world doctor management in the dosing of warfarin, the correct dose is achieved in only 35% of patients. This causes many to be overdosed or under dosed.
The antithrombins are a class of drug which targets just the thrombin part of the effect that warfarin has on the clotting cascade. They are single-dose drugs, meaning everyone takes the same dose and they do not need to be monitored as they are with warfarin. So, patients do not have to undergo a monthly or more frequent blood test to regulate the dose.
If the drug needs to be stopped, it is gone in 24 hours and the onset of action is rapid, unlike with warfarin, which can take seven to ten days. Patients who are hospitalized often spend several extra days in the hospital as they are started on warfarin because insurance companies do not routinely pay for the transition medication as an outpatient. This adds considerably to the overall cost of health care.
Clearly, if the drug is not inferior to warfarin it would be widely accepted even at an increased cost. What if the drug is superior? That is the case with dabigatran.
The RE-LY study enrolled 18,113 patients in 951 clinical centers in 44 different countries. Two doses of dabigatran were studied 110mg twice a day or 150mg twice a day vs. warfarin. These centers were able to manage the dosing of warfarin better than in general, obtaining adequate levels around 64% of the time. The study found that the 110 mg dose of dabigatran was equal to warfarin in preventing stroke with less bleeding and that the 150mg dose of dabigatran was superior to warfarin in preventing stroke but had the same bleeding effects that warfarin did.
This is a major step forward. The most common side effects were gastrointestinal about 11% at both doses of dabigatran. If approved, everyone involved would benefit by easier management of the ever increasing problem of atrial fibrillation in our aging population. This drug is not yet studied in those patients who take warfarin for valvular heart disease. It is, at this time, just for nonvalvular atrial fibrillation. In Europe, this drug is already being used for the prevention of venous blood clots after knee or hip surgery and is known as Pradaxa. In Canada it is known as Pradax. Hopefully it will soon be available here.
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