Friday, April 20, 2007
AF cardiac death
Cardiac Arrhythmias
Currently, the two major areas of cardiac arrhythmias research in the Division of Cardiology are:
Atrial Fibrillation
Sudden Cardiac Death
Atrial fibrillation back to top
A normal, healthy heart typically beats rhythmically and at a predictable rate. However, in some individuals, often those who have underlying heart disease, the heart beats arrhythmically: either too quickly (a condition called tachycardia) or too slowly (called bradycardia). These heart rhythm abnormalities can occur in the upper chambers of the heart (the atria) or the lower chambers (the ventricles).
Atrial fibrillation is the most common sustained cardiac arrhythmia seen in the cardiologist's office. Affecting more than two million Americans, this condition may be associated with symptoms such as palpitations and shortness of breath as well as an increased risk of blood clots and stroke, as well as congestive heart failure in some patients.
Today, there are numerous options for the management of atrial fibrillation, including medications, implantable atrial defibrillators, the surgical maze procedure, or minimally invasive, catheter-based procedures such as radiofrequency ablation. Unfortunately, most do not offer a cure and all have significant limitations.
Research under way within the Division of Cardiology is focused on finding new, more effective, and safer non-pharmacological treatments for atrial fibrillation, including several novel catheter-based approaches. Through the Massachusetts General Hospital Cardiovascular Research Center, the division's research is also aimed at better understanding the possible role of genetics in atrial fibrillation with the long-term goal of developing preventive strategies and new, more targeted therapies.
One of the latest treatments for atrial fibrillation is pulmonary vein catheter ablation. This therapy aims to isolate the underlying triggers of the arrhythmia (the foci) within muscle of the pulmonary veins leading to the atria and ablate (destroy) their connections using radiofrequency (electrical) current delivered via a catheter. In properly selected patients, this therapy can sometimes eliminate or significantly reduce the frequency and duration of episodes of atrial fibrillation. Yet the procedure is complex and lengthy, and is not without some risks, such as narrowing (stenosis) of the pulmonary veinsand, rarely, stroke, even when performed by the most experienced clinicians.
Investigators within the Division of Cardiology are currently conducting research in experimental models aimed at further improving the outcomes for patients undergoing pulmonary vein catheter ablation for atrial fibrillation.
One new approach under investigation is cryothermal ablation, which uses cold energy rather than radiofrequency (electrical) energy to ablate the foci of atrial fibrillation. The results to date indicate that this approach is not only very effective, but may also be less apt to stimulate clot formation and potential stroke. Further research is necessary, but it is anticipated that clinical (human) trials evaluating cryothermal ablation for the treatment of atrial fibrillation willbegin within the near future.
Another potential new strategy for the treatment of atrial fibrillation currently under investigation in the Division of Cardiology uses another new energy source the diode laser. This low-powered laser, which is housed in a balloon and introduced into the pulmonary veins via a catheter, produces a radial (360 degree) lesion [click here for an image of the laser]. This new approach will soon be evaluated in multi-center clinical trials at Massachusetts General Hospital and the Mayo Clinic.
Investigators at MGH are also looking at the possibility of using intraoperative magnetic resonance imaging (MRI) for pulmonary vein catheter ablation. This sophisticated technology, which has revolutionized the treatment of patients with brain tumors, enables physicians to view the operative field in three dimensions, in real time, and with unprecedented detail while avoiding the use of X-rays.
In addition to investigating new treatment strategies, investigators in the Division of Cardiology are striving to determine whether there is a genetic component to lone, or isolated, atrial fibrillation. This form of atrial fibrillation, which affects about one-third of patients, occurs in individuals with no known heart disease.
By studying large populations and families with this disorder, the division's researchers are attempting to find the common gene or genes that cause or predispose someone to develop lone atrial fibrillation. If a genetic marker is found to play a key role in this condition, this information could be used to develop preventive strategies and/or highly targeted therapeutic agents. In collaboration with their colleagues in the Cardiovascular Research Center, researchers are also doing early work in experimental models using gene therapy for atrial fibrillation.
Sudden cardiac death back to top
Every year, sudden cardiac death (also called cardiac arrest) claims the lives of approximately 350,000 people in the United States, about one-third of whom have no prior history of heart disease or obvious symptoms. Sudden cardiac death is usually caused by the most serious forms of cardiac arrhythmia, called ventricular tachycardia or fibrillation, in which rapid electrical activity causes the ventricles to beat very rapidly and, in the case of ventricular fibrillation, to lose all coordinated contraction. Because the ventricles are unable to pump blood effectively at these high rates, the blood pressure falls and patients lose consciousness. Unless cardiopulmonary resuscitation is administered immediately, an individual with ventricular fibrillation will die from cardiac arrest.
Research initiatives under way in the Division of Cardiology are investigating ventricular arrhythmias (both ventricular fibrillation and ventricular tachycardias) from a number of different angles, from prevention to new treatments.
One investigator is conducting long-term epidemiological (population-based) research involving thousands of patients to determine which factors including diet, exercise, and other lifestyle choices increase the risk of sudden cardiac death. The results of this research will ultimately elucidate some of the major risk factors for this common cause of death, making it possible for people to make healthy lifestyle decisions that may reduce their risk of sudden cardiac death.
In a related project, an investigator is evaluating the potential protective effects of omega-3 fatty acids, which are found in fish oil, among patients with a history of life-threatening cardiac arrhythmias who have an implantable defibrillator. Earlier research in experimental models has demonstrated that fish oil is protective against ventricular tachycardia and ventricular fibrillation. The results of this multi-center trial, which will continue for several more years, will help shed more light on the potential role of omega-3 fatty acids in the prevention of a leading cause of death in the developed world.
Researchers in the Division of Cardiology are also evaluating new approaches to the treatment of ventricular tachycardia. In one investigation, which is being conducted in collaboration with researchers in Prague, investigators are employing sophisticated new non-contact, non-fluoroscopic (non X-ray) three dimensional mapping systems in an effort to more accurately isolate cardiac scar tissue that may contribute to ventricular tachycardia. The goal of this substrate-based approach is to be able to more accurately isolate and ablate the border zones of scar tissue from which these abnormal rhythms originate in order to reduce the recurrence rates seen with conventional ablation techniques. In addition, researchers are also beginning to evaluate the use of alternative energy sources, such as cryothermal and diode laser energy, for the treatment of ventricular tachycardia, much as they are doing in the treatment of atrial fibrillation.
Yet another avenue of research is epicardial ablation for the treatment of some ventricular tachycardias and, perhaps in the future, atrial fibrillation as well. In this approach, which is currently being tested in experimental models, catheters are introduced into the heart's pericardial (outer surface) space via a catheter, rather than into the heart through major veins or arteries. It is anticipated that this approach, while currently technically more challenging to perform than existing treatments, may pose a lower risk of clots and stroke.
The preceding is an overview of research of arrhythmias under way in the Division of Cardiology. It is not intended as a complete listing of all current research initiatives in these areas.
Currently, the two major areas of cardiac arrhythmias research in the Division of Cardiology are:
Atrial Fibrillation
Sudden Cardiac Death
Atrial fibrillation back to top
A normal, healthy heart typically beats rhythmically and at a predictable rate. However, in some individuals, often those who have underlying heart disease, the heart beats arrhythmically: either too quickly (a condition called tachycardia) or too slowly (called bradycardia). These heart rhythm abnormalities can occur in the upper chambers of the heart (the atria) or the lower chambers (the ventricles).
Atrial fibrillation is the most common sustained cardiac arrhythmia seen in the cardiologist's office. Affecting more than two million Americans, this condition may be associated with symptoms such as palpitations and shortness of breath as well as an increased risk of blood clots and stroke, as well as congestive heart failure in some patients.
Today, there are numerous options for the management of atrial fibrillation, including medications, implantable atrial defibrillators, the surgical maze procedure, or minimally invasive, catheter-based procedures such as radiofrequency ablation. Unfortunately, most do not offer a cure and all have significant limitations.
Research under way within the Division of Cardiology is focused on finding new, more effective, and safer non-pharmacological treatments for atrial fibrillation, including several novel catheter-based approaches. Through the Massachusetts General Hospital Cardiovascular Research Center, the division's research is also aimed at better understanding the possible role of genetics in atrial fibrillation with the long-term goal of developing preventive strategies and new, more targeted therapies.
One of the latest treatments for atrial fibrillation is pulmonary vein catheter ablation. This therapy aims to isolate the underlying triggers of the arrhythmia (the foci) within muscle of the pulmonary veins leading to the atria and ablate (destroy) their connections using radiofrequency (electrical) current delivered via a catheter. In properly selected patients, this therapy can sometimes eliminate or significantly reduce the frequency and duration of episodes of atrial fibrillation. Yet the procedure is complex and lengthy, and is not without some risks, such as narrowing (stenosis) of the pulmonary veinsand, rarely, stroke, even when performed by the most experienced clinicians.
Investigators within the Division of Cardiology are currently conducting research in experimental models aimed at further improving the outcomes for patients undergoing pulmonary vein catheter ablation for atrial fibrillation.
One new approach under investigation is cryothermal ablation, which uses cold energy rather than radiofrequency (electrical) energy to ablate the foci of atrial fibrillation. The results to date indicate that this approach is not only very effective, but may also be less apt to stimulate clot formation and potential stroke. Further research is necessary, but it is anticipated that clinical (human) trials evaluating cryothermal ablation for the treatment of atrial fibrillation willbegin within the near future.
Another potential new strategy for the treatment of atrial fibrillation currently under investigation in the Division of Cardiology uses another new energy source the diode laser. This low-powered laser, which is housed in a balloon and introduced into the pulmonary veins via a catheter, produces a radial (360 degree) lesion [click here for an image of the laser]. This new approach will soon be evaluated in multi-center clinical trials at Massachusetts General Hospital and the Mayo Clinic.
Investigators at MGH are also looking at the possibility of using intraoperative magnetic resonance imaging (MRI) for pulmonary vein catheter ablation. This sophisticated technology, which has revolutionized the treatment of patients with brain tumors, enables physicians to view the operative field in three dimensions, in real time, and with unprecedented detail while avoiding the use of X-rays.
In addition to investigating new treatment strategies, investigators in the Division of Cardiology are striving to determine whether there is a genetic component to lone, or isolated, atrial fibrillation. This form of atrial fibrillation, which affects about one-third of patients, occurs in individuals with no known heart disease.
By studying large populations and families with this disorder, the division's researchers are attempting to find the common gene or genes that cause or predispose someone to develop lone atrial fibrillation. If a genetic marker is found to play a key role in this condition, this information could be used to develop preventive strategies and/or highly targeted therapeutic agents. In collaboration with their colleagues in the Cardiovascular Research Center, researchers are also doing early work in experimental models using gene therapy for atrial fibrillation.
Sudden cardiac death back to top
Every year, sudden cardiac death (also called cardiac arrest) claims the lives of approximately 350,000 people in the United States, about one-third of whom have no prior history of heart disease or obvious symptoms. Sudden cardiac death is usually caused by the most serious forms of cardiac arrhythmia, called ventricular tachycardia or fibrillation, in which rapid electrical activity causes the ventricles to beat very rapidly and, in the case of ventricular fibrillation, to lose all coordinated contraction. Because the ventricles are unable to pump blood effectively at these high rates, the blood pressure falls and patients lose consciousness. Unless cardiopulmonary resuscitation is administered immediately, an individual with ventricular fibrillation will die from cardiac arrest.
Research initiatives under way in the Division of Cardiology are investigating ventricular arrhythmias (both ventricular fibrillation and ventricular tachycardias) from a number of different angles, from prevention to new treatments.
One investigator is conducting long-term epidemiological (population-based) research involving thousands of patients to determine which factors including diet, exercise, and other lifestyle choices increase the risk of sudden cardiac death. The results of this research will ultimately elucidate some of the major risk factors for this common cause of death, making it possible for people to make healthy lifestyle decisions that may reduce their risk of sudden cardiac death.
In a related project, an investigator is evaluating the potential protective effects of omega-3 fatty acids, which are found in fish oil, among patients with a history of life-threatening cardiac arrhythmias who have an implantable defibrillator. Earlier research in experimental models has demonstrated that fish oil is protective against ventricular tachycardia and ventricular fibrillation. The results of this multi-center trial, which will continue for several more years, will help shed more light on the potential role of omega-3 fatty acids in the prevention of a leading cause of death in the developed world.
Researchers in the Division of Cardiology are also evaluating new approaches to the treatment of ventricular tachycardia. In one investigation, which is being conducted in collaboration with researchers in Prague, investigators are employing sophisticated new non-contact, non-fluoroscopic (non X-ray) three dimensional mapping systems in an effort to more accurately isolate cardiac scar tissue that may contribute to ventricular tachycardia. The goal of this substrate-based approach is to be able to more accurately isolate and ablate the border zones of scar tissue from which these abnormal rhythms originate in order to reduce the recurrence rates seen with conventional ablation techniques. In addition, researchers are also beginning to evaluate the use of alternative energy sources, such as cryothermal and diode laser energy, for the treatment of ventricular tachycardia, much as they are doing in the treatment of atrial fibrillation.
Yet another avenue of research is epicardial ablation for the treatment of some ventricular tachycardias and, perhaps in the future, atrial fibrillation as well. In this approach, which is currently being tested in experimental models, catheters are introduced into the heart's pericardial (outer surface) space via a catheter, rather than into the heart through major veins or arteries. It is anticipated that this approach, while currently technically more challenging to perform than existing treatments, may pose a lower risk of clots and stroke.
The preceding is an overview of research of arrhythmias under way in the Division of Cardiology. It is not intended as a complete listing of all current research initiatives in these areas.
# posted by roodbont @ 2:06 AM 
