Welcome to HeartNotes! Here, you'll find notes compiled from various conferences on cardiology. These notes have been prepared by researchers who attended the conferences. The purpose of HeartNotes is to promote the latest information on cardiology research in simple language. Feel free to review the notes, learn about heart disease and recommendations made by researchers.What is Atrial Fibrillation (AFib) and how to deal with it?
These notes on atrial fibrillation are based on presentations by Dr Paul Wang, Dr Henry Hsia, Dr Paul Zei and Dr Amin Al-Ahmad, researchers at the Stanford Medical Centre. Dr Wang argued that atrial fibrillation, or irregular heart beat is a condition associated with very fast heart rate. atrial fibrillation, centered around 60–80 years, is set on a trajectory of exponential growth with the rise in aging population. Atrial fibrillation increases stroke risk based on certain factors.
Controlling atrial fibrillation and managing stroke risks are independent tasks. Stroke risk factors (CHADS2) influence the decision for medical therapy. Persistent atrial fibrillation requires intervention such as medication or a shock, while paroxysmal atrial fibrillation terminates on its own. Strategies to deal with atrial fibrillation are to restore the sinus rhythm or control the ventricular rate. Dr Hsia argued that a common approach is to use drugs to control atrial fibrillation. A trial showed that the success rate of using drugs for controlling atrial fibrillation is approximately 50%, but each drug could have side effects. Catheter ablation, small plastic tubes inserted through arteries or veins into the heart, is another approach. Dr Zei argued that strategies to manage stroke risk are to use blood thinners such as Aspirin or Plavix, reduce the burden of atrial fibrillation or isolate the Left Atrial Appendage (LAA) from the rest of the heart. Studies have shown effectiveness of catheter-based LAA occlusion. Dr Al-Ahmad concluded that newer treatments such as anticoagulants and devices look promising.
These notes on the epidemiology and novel oral anticoagulants of atrial fibrillation are based on a presentation by Dr Samuel Goldhaber, Director of VTE Research Group, Cardiovascular Division, Brigham and Women’s Hospital. Atrial fibrillation could result in death, stroke, hospitalizations, reduce the quality of life and exercise capacity, or result in left ventricular dysfunction. Dr Goldhaber predicted that 12–16 million Americans will be affected by A-Fib by 2050. Prevalence of A-Fib is greater in men than women in all age groups. Congestive heart failure, hypertension, age, diabetes mellitus and stroke (CHADS2) are the risk factors for A-Fib. A score of two or more on CHADS2 indicates a moderate to high risk for stroke.
Aspirin and Warfarin are common drugs used as blood thinners. Studies have shown that Warfarin is more effective than Aspirin. Dr Goldhaber argued that the quality of anticoagulation control is of critical importance. Some common problems associated with Warfarin are delayed onset / offset, unpredictable dose response, narrow therapeutic index, drug-drug and drug-food interactions, problematic monitoring, high bleeding rate and slow reversibility.
Top novel oral anticoagulants include Dabigatran, Rivaroxaban, Apixaban and Edoxaban. Dr Goldhaber showed that studies have revealed that Dabigatran is approximately 30% more effective than Warfarin in reducing the stroke rate. It also reduces mortality by over 10%. Patients should know that the effectiveness of blood thinners has tradeoffs with bleeding complications. Novel anticoagulants will provide more choices even though more expensive, while Warfarin will continue to be one of the choices because of its low cost and long track record.
Dr Matthew Hutchinson, cardiologist, Penn Medicine, stated that understanding atrial fibrillation requires a frame of reference of the normal rhythm. A normal heart, for example, beats 60–70 times a minute. Each impulse from the pacemaker is transmitted to the heart, and each depolarization or each impulse causes a heartbeat. Dr Hutchinson said that patients develop tiny circuits that spin chaotically, causing the top chambers to beat continuously in atrial fibrillation. The heart rate is 100 beats or more per minute instead of the normal 60–70 beats per minute in a normal state of relaxation. The extra beats originate from the pulmonary veins, which connect the heart and lungs together. A highly irregular rhythm results from the bombarding of electrical impulses.
Dr Hutchinson demonstrated that the prevalence of atrial fibrillation becomes higher with age and 15% above the age of 70 suffer from it. Common symptoms in A-Fib patients are palpitations, shortness of breath, fatigue, lightheadedness and chest pain. ECG is used to determine atrial fibrillation. A cause of concern is that the majority of episodes with A-Fib don’t show any symptoms indicating that symptoms greatly underestimate the impact of the disease. Atrial fibrillation gets worse with age because the firing veins fire more frequently.
Atrial fibrillation, atrial flutter and supraventricular tachycardia (SVT) are heart rhythm problems causing the heart to beat too fast. Ventricular tachycardia and ventricular fibrillation occur in the ventricle, causing the heart to beat too fast. On the other hand, the sinus node may not work properly for various reasons causing the heart to go too slow. It is also known as sick sinus syndrome. Complete heart block is a block between the upper and lower chambers of the heart. Atrial fibrillation is a problem where the thinking and treatment has changed a lot recently. There may be several mechanisms that cause A-Fib. For example, the point of origin of fast and irregular impulses lies in a certain area in the upper chamber of the heart and the opening of the pulmonary veins into the left upper chamber of the heart is also an area that causes A-Fib. Symptoms and stroke risk influence treatment of A-Fib. Patients with atrial fibrillation have a five-fold higher chance of having a stroke because blood can pool in the upper chambers when the upper chambers are no longer contracting normally. Currently, Warfarin and Coumadin are good recommendations for blood thinners. Surgical scars are created in the upper chambers of the heart, in open-heart surgery, to make little compartments in the upper chambers so that atrial fibrillation can’t spread. A specific area is cauterized using radio frequency ablation techniques to electrically isolate the upper chambers in ablation techniques. There is the need for a device with complete pacemaker capabilities -- a complete defibrillator with biventricular pacing.