Atrial Fibrillation (AF) is a type of arrhythmia. AF is characterized by very fast, irregular beating of the heart's upper chambers (the atria). AF increases the risk of stroke by fivefold1, and can lead to the progression of heart disease. It is characterized by an irregular and fast heartbeat that is induced by abnormal electrical impulses. These impulses affect the atria causing erratic signals which prevent the atria from producing full contractions. In turn, the ventricles have less time to fill with blood, which reduces blood flow and oxygen to the rest of the body’s organs.
AF is the most common type of cardiac arrhythmia found in adults today, affecting over 5.6 million patients in the United States and is expected to affect 15.9 million patients by 2050.2 AF is a growing problem, not only in the United States, but all over the world. The incidence of AF continues to increase as the population ages. These statistics indicate that, a large unmet medical need exists to treat AF, eliminate dependence on anti-arrhythmic drugs (AADs), and improve the quality of life for these AF patients.
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Focal AF: The source of the irregular pathways in the heart muscle is associated with electrical activity that can originate from a single location in the heart, such as one of the pulmonary veins. Focal AF is present in about 15% of the AF population.
Wavelet AF: The source of wavelet AF is commonly associated with macro-reentrant circuits causing erratic electrical signals throughout both the atria, and is present in about 85% of the AF population.
Atrial Fibrillation Classification3
1. Paroxysmal AF
(Predominantly focal) Recurring AF episodes that end on their own within seven days. No medical treatment is necessary to stop the AF episodes
2. Persistent AF
(Predominately wavelet) AF that is sustained beyond seven days, or lasting less than seven days but necessitating pharmacologic or electrical cardioversion
3. Longstanding Persistent AF
(Predominantly wavelet) Continuous AF of greater than one-year duration
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Some Common Causes of AF
Common Symptoms of AF
The symptoms of AF vary greatly from person to person. Symptoms of AF can include4:
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Current AF therapies are limited and primarily focused on treating focal AF / paroxysmal AF. The current treatment options offered for AF are:
Medications:
AF is typically first treated with drug therapy, with an approximately equal split between rate and rhythm control drugs as first line of treatment. Treatment of AF with medications has been associated with high failure rates and side effects.
- Rate control drugs attempt to reduce the symptoms of AF by lowering the ventricular rate to less than 100 beats per minute.
- Rhythm control drugs or antiarrhythmics (AADs), work to stabilize heart rhythm and maintain a normal sinus rhythm.
Neither rate nor rhythm drugs are cures for AF and may require lifelong dependence to reduce symptoms.
Regardless of a rate or rhythm control approach, continuous anticoagulation therapy is important for stroke prevention. Anticoagulants, or blood thinners, do nothing to address the abnormal heart beat, but instead are used to prevent the formation of blood clots. Coumadin® (warfarin) is the most widely prescribed anticoagulant, however, it has potential risks and side effects. Recent studies have also shown that some individuals have a genetic intolerance to Coumadin.®5
Cardioversion:
Cardioversion is a procedure performed as an attempt to reset the heart into normal rhythm by applying electrical energy through the chest for a very short period of time. This is a hospital procedure requiring anesthesia and may stop AF only temporarily.
Catheter Ablation:
Catheter ablation has been used for the treatment of AF since the mid-1990s. Catheters are used to ablate the heart wall to form a non-conductive barrier that interrupt erratic signals primarily located in the pulmonary veins. While catheter ablation methods have been modified over time, success rates have been limited6. Often, multiple procedures are required before a successful outcome occurs. However, catheter ablations are less effective for the treatment of patients who have been in AF for more than one year, have enlarged atria, or have underlying structural heart disease.
Catheter ablation has not proven to be effective for the persistent and longstanding persistent (wavelet AF) population. To treat this more challenging and larger percent of AF population a comprehensive biatrial lesion pattern needs to be created to interrupt the macro re-entrant circuits that cause these two types of AF.
Surgical Procedures:
Surgical treatment of AF is usually considered when a patient is already scheduled for another heart procedure. The Cut and Sew Maze procedures require stopping the heart and then surgically cutting and re-sewing the atria to create a complex pattern of lesions. The Cox-Maze procedure has been the standard of care in surgical treatment of wavelet AF. However, the complexity has made it a less attractive treatment option.
To reduce complexity, ablation replaced incisions using instruments such as bipolar clamps or pens to interrupt abnormal electrical signals in the heart. These devices use various energy sources such as radiofrequency (RF) to coagulate cardiac tissue. However, these techniques are limited to open heart procedures, which require using the heart-lung machine, chest incisions, and lung deflation. These approaches have largely been relegated to isolating the pulmonary veins, which may be effective for focal AF patients who have paroxysmal AF with no structural heart disease. However, wavelet AF requires a comprehensive biatrial lesion pattern to block all reentrant circuits, and therefore sole isolation of the pulmonary veins is not an effective treatment.
For the nContact concomitant surgical approach, using its Numeris®-AF Tethered investigational ablation device, a comprehensive bi-atrial lesion pattern can be applied to the heart while the heart is beating and thus eliminate time on the heart-lung machine. nContact is currently undergoing clinical trials to pursue an indication to treat AF in this open chest procedure.
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nContact is initiating US clinical trials to evaluate the efficacy of a comprehensive bi-atrial lesion pattern that can be created during a combined procedure using its Numeris®-AF Guided investigational ablation device epicardially and a commercially available endocardial catheter. The scientific premise behind the procedure is to combine the best techniques of Electrophysiologists and Cardiovascular Surgeons to develop what is hoped to be a total solution for all AF patients. The first step of the procedure is surgical and the goal is to create a comphrehensive bi-atrial lesion pattern on the outside of a beating heart without creating chest incisions. The second step involves an Electrophysiologist who uses an interventional ablation catheter to complete the lesion pattern. In addition, Electrophysiologists will utilize diagnostic catheters to ensure that reentrant circuits have in fact been interrupted and to determine if there are other circuits outside the pattern that need to be interrupted. It is hoped that the combination of interdiscipinary techniques will provide AF patients with a truly minimally-invasive treatment alternative.
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