Structural And Functional Determinants Of Spatiotemporal Periodicity In Cardiac Impulse Propagation
Funder
National Health and Medical Research Council
Funding Amount
$211,320.00
Summary
Abnormal heart rhythms (cardiac arrhythmias) are responsible for much morbidity and excess mortality in Australia. Although many abnormalities leading to an abnormal heart rhythm may be successfully treated by medications or minimally invasive operative procedures there are several important ones which are not. These include the most common significant cause of an abnormal heart rhythm, atrial fibrillation, and the arrhythmias responsible for approximately half of sudden deaths, ventricular tach ....Abnormal heart rhythms (cardiac arrhythmias) are responsible for much morbidity and excess mortality in Australia. Although many abnormalities leading to an abnormal heart rhythm may be successfully treated by medications or minimally invasive operative procedures there are several important ones which are not. These include the most common significant cause of an abnormal heart rhythm, atrial fibrillation, and the arrhythmias responsible for approximately half of sudden deaths, ventricular tachycardia and ventricular fibrillation. Atrial fibrillation is a leading cause of stroke. Sudden death is associated with aging and is an increasing problem because of the rising mean age of the population. Recent negative attention on the side effects of medications used for the treatment of cardiac arrhythmias has appropriately increased interest in curative approaches requiring no onging medications. These procedures usually rely on mapping electrical activity in the heart and interrupting abnormal electrical pathways using radiofrequency electrical current. The procedures are unsuccessful when existing techniques fail to identify the underlying mechanism responsible for the abnormal heart rhythm or when the source of the abnormal beating cannot be localised within the heart. In this project we investigate the fundamental basis for a new approach to these problems. By examining the variability of the beat rate and the variability of the beat rate at different points within the heart we may be able to identify arrhythmia mechanisms and localise arrhythmia sources. In this project we will examine in groups of cells the structures and types of electrical circuits which give rise to certain types of beat-to-beat variability in the heart. This information will be essential for the interpretation of information obtained in later human studies and the subsequent development of new curative procedures for these problems.Read moreRead less
Microwave And Laser Energies For Percutaneous Cardiac Ablation For The Cure Of Arhythmias
Funder
National Health and Medical Research Council
Funding Amount
$331,527.00
Summary
The commonest beating disorder of the heart is atrial fibrillation (AF). Whilst it can occur at any age it is more common in the elderly with 12% Australians over 70 y.o having it. AF is the cause of a third of all strokes and increases the risk of dying from any heart disease. Ventricular tachycardia (VT) is the commonest cause of death in the year after a heart attack. Currently these beating disorders are in most cases incurable and respond poorly to medications. We have developed an operatio ....The commonest beating disorder of the heart is atrial fibrillation (AF). Whilst it can occur at any age it is more common in the elderly with 12% Australians over 70 y.o having it. AF is the cause of a third of all strokes and increases the risk of dying from any heart disease. Ventricular tachycardia (VT) is the commonest cause of death in the year after a heart attack. Currently these beating disorders are in most cases incurable and respond poorly to medications. We have developed an operation for AF which is done by open heart surgery. It has been successful at curing some patients who suffer from AF and uses radiofrequency energy. The difficulty of radiofrequency energy is that it is not suitable in a large number of cases for this operation. We are developing Laser and Microwave catheters as alternatives to RF so that the success of the operation can be improved. These new microwave and laser catheters are being designed and tested to be used primarily in a minimally invasive procedure. They would be inserted via the veins with the patient under sedation. This would allow patients to go home sooner and have a recovery period of only a few days. As well as their application in the top chamber of the heart (atrium) for AF, these new energies will be adapted for minimally invasive operations in the ventricle (lower chamber) of the heart for the treatment of ventricular tachycardia. By developing a technique such as this, cure of AFand VT will be available to many more people, helping reduce the strokes, heart failure and premature deaths from these two heart conditions.Read moreRead less
Atrial Electrical Remodeling Due To Chronic Stretch: Defining The Substrate For Atrial Fibrillation
Funder
National Health and Medical Research Council
Funding Amount
$428,250.00
Summary
Background: Cardiac failure is a common heart disorder in which the pumping function of the heart is significantly weakened. Mitral regurgitation is a common condition where there is a leakage of blood from the left ventricle (lower heart chamber) back into the left atrium (upper heart chamber) during normal cardiac contraction. This puts a strain on the heart and may cause heart failure. Atrial septal defect is a common form of congenital heart disease which may not be diagnosed until adulthood ....Background: Cardiac failure is a common heart disorder in which the pumping function of the heart is significantly weakened. Mitral regurgitation is a common condition where there is a leakage of blood from the left ventricle (lower heart chamber) back into the left atrium (upper heart chamber) during normal cardiac contraction. This puts a strain on the heart and may cause heart failure. Atrial septal defect is a common form of congenital heart disease which may not be diagnosed until adulthood. There are several forms but the basic problem is leakage of blood from the left atrium into the right atrium .This also puts a strain on the heart and can cause heart failure. All 3 conditions are associated with a significantly increased risk of atrial fibrillation (AF). This abnormal fast irregular cardiac rhythm makes the pumping of the heart inefficient. People with AF may feel short of breath, tired, or develop palpitations. AF is an important cause of stroke and premature death and is the most common heart rhythm disturbance occurring in upto 10% of the over 70 age group. Even after repair of the leaky valve or atrial septal defect there is still a high risk of developing this rhythm. Purpose of the study: This study will try to understand why patients with these conditions are at risk of developing atrial fibrillation, and why this risk might persist after surgical correction when this is possible (mitral regurgitation and atrial septal defect). The study will utilise sophisticated new mapping techniques to gain original insights into the mechanism of this very common and as yet poorly understood heart rhythm disturbance. The study has the potential to determine the cause of atrial fibrillation in these patient groups and as such represent a quantum advance in our understanding of he mechanism of atrial fibrillation. It would be expected to form a foundation on which development of curative and preventative approaches may be based.Read moreRead less
Analysis Of Atrial Electrical Remodelling In Patients With Paroxysmal And Persistent Atrial Fibrillation
Funder
National Health and Medical Research Council
Funding Amount
$127,516.00
Summary
I am a cardiologist undertaking further training in the management of electrical abnormalities of the heart. My research will focus on the mechanisms responsible for atrial fibrillation, the most common serious heart rhythm disorder. I intend to do this by examining the nature of the electrical activity in patients with atrial fibrillation and comparing this to electrical activity in patients without this disorder, who are undergoing treatment procedures for their electrical disorder.
Atrial fibrillation (AF) is the most common cause for an irregular heart beat. Catheter ablation is the only potential cure and involves passing wires via veins in the leg into the heart to deliver discrete small burns(ablation) around the pulmonary veins (PV), the major source for AF. Unfortunately 30-50% of patients have recurrent arrhythmia due to reestablishment of electrical connections. This multicentre internation trial examines whether more (maximal) ablation will improve the outcomes of ....Atrial fibrillation (AF) is the most common cause for an irregular heart beat. Catheter ablation is the only potential cure and involves passing wires via veins in the leg into the heart to deliver discrete small burns(ablation) around the pulmonary veins (PV), the major source for AF. Unfortunately 30-50% of patients have recurrent arrhythmia due to reestablishment of electrical connections. This multicentre internation trial examines whether more (maximal) ablation will improve the outcomes of the procedure.Read moreRead less
Characterisation Of CFAE Wavefront Propogation In Human Persistent AF
Funder
National Health and Medical Research Council
Funding Amount
$418,612.00
Summary
Atrial fibrillation can be eliminated by a relatively new treatment called catheter ablation, which involves modification of the electrical properties of the heart using thin wires (catheters) passed up from the leg. Targeting areas where catheters record abnormal electrical activity improves results of catheter ablation, although it is uncertain what these recordings represent. The aim of this study is to characterize these abnormal electrical signals in an attempt to improve ablation outcomes.
Understanding The Mechanisms Of Atrial Fibrillation: High Density Intra-operative Mapping
Funder
National Health and Medical Research Council
Funding Amount
$94,025.00
Summary
We hypothesize that: During atrial fibrillation, regions acting as short cycle length drivers will demonstrate characteristic sinus rhythm electrophysiology including conduction slowing and abbreviated refractoriness. We aim to correlate the nature of electrical activity in atrial fibrillation with that in sinus rhythm. We will focus on particular anatomic locations that have been shown to be regions of anisotropy and sites where short cycle length rotors have been observed. The anatomic locat ....We hypothesize that: During atrial fibrillation, regions acting as short cycle length drivers will demonstrate characteristic sinus rhythm electrophysiology including conduction slowing and abbreviated refractoriness. We aim to correlate the nature of electrical activity in atrial fibrillation with that in sinus rhythm. We will focus on particular anatomic locations that have been shown to be regions of anisotropy and sites where short cycle length rotors have been observed. The anatomic location and electrophysiologic (EP) characteristics of these regions will vary according to the underlying atrial substrate. We aim to characterise the differences in atrial electrophysiology in AF and sinus rhythm between different pathophysiologic substrates. With high density mapping targeted to critical anatomic sites it will be possible to determine the EP mechanism of short cycle length rotors. We aim to characterise the EP mechanism of these short cycle length regions by analysis of recordings from high density mapping plaques.Read moreRead less
Stretch Induced Pulmonary Vein Remodelling: Implications For The Initiation And Maintenance Of Atrial Fibrillation
Funder
National Health and Medical Research Council
Funding Amount
$569,823.00
Summary
Atrial fibrillation (AF) is the most common heart rhythm disorder to affect humans, occurring in 2% of adults. It is a chaotic rhythm disorder of the top chambers of the heart that results in frequent hospitalization for falls, chest pain, palpitations, heart failure and stroke. In addition, it is associated with an increased mortality. Evidence suggests an important role of the pulmonary veins (PV; veins draining blood from the lungs back to the heart) in the initiation and maintenance of AF. H ....Atrial fibrillation (AF) is the most common heart rhythm disorder to affect humans, occurring in 2% of adults. It is a chaotic rhythm disorder of the top chambers of the heart that results in frequent hospitalization for falls, chest pain, palpitations, heart failure and stroke. In addition, it is associated with an increased mortality. Evidence suggests an important role of the pulmonary veins (PV; veins draining blood from the lungs back to the heart) in the initiation and maintenance of AF. However, why these structures promote AF remains unknown. Several conditions predisposing to the development of AF are associated with atrial stretch (such as heart failure). These conditions have documented abnormalities within the atria but the changes that occur within the PVs are unknown. It has even been suggested that pulsatile stretch, as caused by blood flow, in the appropriately predisposed patient, may be enough to trigger AF. As such there has been an intensive search to identify the abnormalities that occur within the PVs. In patients with AF, the PVs demonstrate distinctive electrophysiological properties compared to those without AF. However, the effect of stretch, a common predisposing factor, on the electrophysiological properties of the PV is not known. Preventing electrical activity from the PVs interacting with the heart by ablation has provided a glimpse at our ability to cure AF. However, further improvements in our procedural technique, the ability to prevent the occurrence of this rhythm disorder, and the development of noninvasive strategies to cure AF, hinges on the better understanding of the mechanisms initiating and maintaining this condition. In particular, the electrophysiological changes within the PVs that predispose patients to the development of AF need to be investigated. This series of studies will evaluate the effect of acute and chronic stretch on the PVs in humans to determine why these structures promote AF.Read moreRead less