Research




	NEW DEVELOPMENTS Over the past several years the US Food and Drug Administration (FDA) has approved a number of new treatments as well as the use of established treatments for other diseases. Among these developments are: radiofrequency ablation for atrial fibrillation , use of biventricular pacemakers or biventricular defibrillators for patients with congestive heart failure and the finding of a new group of patients who stand to benefit from a defibrillator (New ICD Indication). Radiofrequency Ablation of Atrial Fibrillation Recent studies have shown that in many patients with paroxysmal atrial fibrillation (meaning, spells occur intermittently or on & off) their arrhythmias are triggered or originate from small muscle fibers in structures called the pulmonary veins. The pulmonary veins, of which there are usually 4, are the blood vessels that carry blood from the lungs and bring it to the heart. By selectively performing radiofrequency ablation on the small muscle fibers in these pulmonary veins, episodes of atrial fibrillation can be significantly reduced, better controlled or even cured (which has never been thought possible).




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		Schematic and x-ray appearance of mapping and ablation of pulmonary veins.

	While this development is new, exciting and proven to be effective, it is still in the process of developed further, and is thus reserved for those with atrial fibrillation that can not be controlled by multiple medications. If you have troublesome paroxysmal atrial fibrillation and think you might be a candidate for this procedure, ask your physician. Biventricular Pacemakers and Defibrillators (Resynchronization Therapy) When a pacemaker or defibrillator (or ICD) is placed, either one or two leads (or wires) are threaded through the arm vein to the heart. These wires both monitor and send electrical signals to the upper chamber (atrium), lower chamber (right ventricle) or both (please see schematic for pacemaker, ICD). Recently, large clinical trials in over a thousand patients with heart failure and enlarged hearts have shown improved symptoms (of breathing, need for less medications and exercise capacity) with the placement of a 3^rd wire for the left ventricle. This is what is called resynchronization therapy.

Schematic and example of a biventricular pacemaker.

Normally, the left ventricle (the heart's main pumping chamber) contracts in a very coordinated or synchronized manner. This occurs because heart muscle is healthy, the electrical system is healthy and electrical conduction through the heart is swift. In very many patients with heart failure and enlarged hearts, there are problems with heart muscle, the electrical system or both. As a result, the left ventricle contracts in a very uncoordinated or unsynchronized manner, wasting a lot of energy and efficiency in the process. When this happens, the heart's ability to pump blood and oxygen to meet the body's needs is severely reduced, and one feels tired, easily fatigued, short of breath and accumulates fluid.

By placing a 3^rd wire, electrical signals can be sent to stimulate the right side (via the right ventricle) and the left side (via the coronary sinus, a large vein in the heart) simultaneously, resulting in a more coordinated, synchronized and vigorous contraction of the heart. .


	X-ray appearance of a biventricular pacing system. Note the 3 wires.


	Some patients who need a biventricular pacemaker also need a defibrillator or ICD. In this case, a 3^rd wire is also placed in addition to the 1 or 2 standardly placed for a regular defibrillator. In some patients who already have a pacemaker or a defibrillator but who continue to be limited by their symptoms, an upgrade to a biventricular system may be appropriate.


	If you have heart failure, an enlarged heart and continue to have poor energy, easy fatigue and get short of breath easily, or if you have an existing device and continue to have these symptoms, ask your physician if you might be a candidate for resynchronization therapy or an upgrade to a biventricular system.

New ICD Indication

Recent results from a large clinical trial involving over a thousand patients show that anyone with a previous heart attack and poor pump function are at an increased risk of life-threatening arrhythmias and stand to benefit from placement of a defibrillator or ICD. This is an important development because a lot of people meet these criteria and one does not have to be screened with an EP study to determine if you are prone to these arrhythmias. If you have previously suffered a heart attack that may have compromised your heart's pumping function, ask your physician if you might benefit from an ICD. For more information on ICDs, please click on the highlighted tab: defibrillators.


	Schematic for a biventricular ICD system

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