Yesterday, a 71-year active male hypertensive reformed smoker approached seeking my opinion for management of atrial fibrillation using an appendage closure device. He is a retired IAS officer working as a Consultant with an active life style. He has been on Dabigatran for prevention of stroke and wanted a device to obviate the need for life long medicines. I had a detailed discussion on the pros and cons of the device vs drugs and finally suggested him to stay put on medicines.
Atrial fibrillation is a growing health care problem afflicting elderly patients. It is seen in 1-2% of population as a whole but in people more than 70 years age, this disease affects 6-8%.
What is atrial fibrillation?
Heart has four chambers – 2 upper chambers called atria and 2 lower chambers called ventricles. Blood is received from different organs of body to upper chambers (atria) and sent to lower chambers (ventricles) from where they are sent to lungs and all organs of the body.
Why is atrial fibrillation is a major problem now a days?
With increasing prevalence of elderly population, rising obesity rates, more people suffering from hypertension, diabetes, chronic lung problems; the walls of the ventricles get thickened and stiffened. When the lower chambers get stiffer, upper chambers need to exert more pressure to pump blood. Initially they can do this well but as they ventricles become much stiffer they are unable to take this additional load and start beating chaotically. This chaotic beating of the upper heart is termed “Atrial Fibrillation” in medical terms.
How does Atrial Fibrillation affect the heart and body?
Atrial Fibrillation (AF) leads to reduced pumping efficiency of heart (atria contribute to 1/5 of cardiac efficiency) and more importantly this reduced contraction of the upper chambers leads to pooling of blood leading to formation of clots in the heart.
Clots formed in the heart have the potential to be transported to various organs of the body most notably brain. Blood clots that get lodged in the brain lead to paralytic stroke.
Paralytic stroke and atrial fibrillation:
Paralytic stroke is a common problem amongst elderly people and most cases are due to atrial fibrillation. The risk of stroke in those with AF is increased by 3 times compared to those without AF.
Blood clot formation in the cardiac chambers is the main reason for stroke, hence blood thinners are used to prevent the thrombus formation. When used for long term they are an excellent strategy for preventing clot formation.
Is aspirin an effective blood thinner?
Blood thinners are mainly two types:
- Anti-Platelet agents – Aspirin, Clopidogrel, Ticagrelor
- Anti-thrombotics –
A.Vitamin K antagonists – Warfarin, Coumadin
B.Direct Acting Oral Anticoagulants – Apixaban, Rivoraxaban, Dabigatran
Antiplatelet agents are not effective for prevention of stroke in atrial fibrillation.
Anti-thrombotics and atrial fibrillation:
Anti-thrombotics are used to prevent stroke in patients with AF. Till 5 years ago, Warfarin and Coumadin are the main stay for prevention of stroke in AF. But these drugs though very effective have a higher risk of bleeding complications. Hence the prescription rates for these drugs were less than 50% for those deserving patients.
Of late, availability of Dabigatran, Apixaban and Rivoraxaban dramatically changed the prescription rates as they are much safer agents compared to the older agents like warfarin. In addition one need not get periodic monitoring of PT/INR for assessing the efficiency of these drugs.
Direct Oral Anticoagulant agents can be safely prescribed in the very elderly patients (more than 80 years). The main limitation in prescribing these agents is in those with previous valve replacement surgery, renal dysfunction and those with associated with moderate to severe valvular disease. Patients with these sub groups cannot be prescribed these new agents as they have not been studied in those groups.
Left Atrial Appendage Closure devices:
Left atrial appendage (an out pouch of the left upper chamber) is an important (but not only) source for development of thrombus in scenario of AF. Over the last decade, clinicians have started occluding the appendage using devices either from within the heart (Watchman, Amulet) or outside the heart (Lariat, Atriclip).
Once the atrial appendage is occluded it was believed that there is no need for blood thinners. When using Warfarin and Coumadin, risk of bleeding is high but not with newer agents. Hence with the advent of these new agents Clinicians are not aggressive in implanting appendage closure devices. In addition, these procedures are invasive and potentially risky. Also even after implantation of device Warfarin or Coumadin has to be administered for the initial 90 days as there is a foreign body in the heart. Finally, paralytic stroke is a systemic problem and not a local problem limited to left atrial appendage, hence patient continues to be exposed to the risk. On the contrary, new blood thinners, have effect over the entire body (systemic effect) and not on the atria alone.
Left atrial appendage occlusion is a treatment to reduce the risk of stroke in patients with atrial fibrillation. This is a treatment that is invasive in nature that involves the implantation of a foreign body to obviate the use of blood thinners. New blood thinners are much safer (low bleeding), effective and need no monitoring with PT/INR blood tests. So this treatment is limited to those groups of patients who are not suitable candidates for anti-coagulation.