When heart rhythm becomes chaotic, as it does for many people as they age, a balancing of treatment options and risks is required, writes Sarah Conroy.
Atrial fibrillation is a common disorder of the heart rhythm that affects more than 60,000 people in Ireland. It is caused by chaotic electrical activity in the upper chamber of the heart (the atrium), see graph. This results in a fast and irregular pulse from the lower chamber (the ventricle).
The development of atrial fibrillation (AF) in some patients gives rise to fatigue, heart palpitations, light-headedness, shortness of breath and a reduction in exercise tolerance.
In other patients, AF may cause minimal symptoms and it may not be detected until their next routine medical examination. If left untreated, there is a risk of progressive heart muscle disease.
There are two different types of AF. "There is the type which has a persistent pattern that comes on and does not stop until treated and there is the paroxysmal type which is intermittent, coming on and going away spontaneously," according to Dr David Keane cardiologist and electrophysiologist at St James's Hospital and the Blackrock Clinic in Dublin.
The first treatment is to slow down the heart rate with a drug called a beta-blocker. In some patients with AF, prevention of stroke with anti-clotting drugs such as warfarin will also be considered. Patients on warfarin require regular blood tests to have their clotting time checked.
"Although the risk of stroke is relatively low, it is of particular concern in people who are elderly - over 75; those who have had a previous stroke; or those with high blood pressure, diabetes or heart failure," Dr Keane says. Unfortunately, warfarin exposes the patient to a risk of bleeding, but in patients who also have the above conditions, the benefit (protection from stroke) outweighs the risk.
In a small minority of patients, avoidance of excess alcohol or treatment of an underlying condition such as an over-active thyroid gland may prevent further recurrences of AF. In the majority of patients, however, atrial fibrillation tends to be a recurrent condition and over time episodes may become more frequent and prolonged.
For active people under 65 years old who are symptomatic, preventive treatment for recurrence of AF is usually required.
In the past decade, anti-arrhythmic drug therapy was the principal preventative treatment for such patients.
As the risk of serious complications from anti-arrhythmic drug therapy became more widely recognised in the 1990s, the development of a curative procedure was undertaken.
A relatively new procedure, catheter ablation - pulmonary vein isolation, is now available for highly symptomatic patients.
Dr Keane has been involved in the evolution of catheter ablation techniques for AF in Boston for the past 10 years, and has continued since returning to Ireland last year.
Pulmonary veins are isolated because most of the chaotic electrical signals (98 per cent) come from that area.
"Under conscious sedation and local anesthesia, catheters are introduced into the heart through the blood vessels in the leg. The catheters are used to record the electrical signals from the heart and deliver current to cauterize part of the heart muscle, so the heart muscle which is involved in generating or maintaining the arrhythmia, atrial fibrillation, is cauterized," Dr Keane explains.
"The success rate of this two to three-hour procedure is now 60-80 per cent with approximate 20 per cent requirement for a repeat procedure," Dr Keane adds.
Patients who do best with this procedure are those with the intermittent "paroxysmal" pattern of AF and those without advanced heart disease.
Like anti-arrhythmic drug therapy and anti-clotting drug therapy, catheter ablation also carries risks. The upfront risks of the procedure have to be balanced against the long-term accumulative risks of drug therapy.
Some patients who suffer with AF and who need to undergo open heart surgery for another heart condition such as a valve repair or coronary artery bypass grafting may have their heart arrhythmia treated simultaneously.
Mr Michael Tolan, consultant cardiothoracic surgeon at St James's Hospital, St Vincent's University Hospital and Blackrock Clinic, Dublin, has been carrying out what is known as the Maze procedure to manage AF. This procedure has been available to patients for the past two years.
Some patients with AF alone who have particularly distressing symptoms and in whom drug treatments have been ineffective choose to have the Maze operation done. It involves the surgeon making ablation lines in different regions at both atria with radiofrequency or microwave probes. This prevents the chaotic transmission of electrical signals through the heart.
"This involves the use of radiofrequency probes to make incisions which block conduction of abnormal chaotic electrical impulses going from the pulmonary veins to the left atrium," Mr Tolan explains.
Although the patient spends a longer time on the operating table, the Maze procedure itself takes only 20 minutes.
According to Mr Tolan, about 20-30 per cent of patients undergoing bypass will need the Maze procedure. The success rate of this operation is positive, as it is "82 per cent successful in the long term" with "very few risks or complications" involved and the patient requires no further medication.
For those who have the option of taking long-term drug therapy or undergoing a procedure, Dr Keane stresses, "You must weigh up the risks and relative merits and limits of each therapeutic option. You need to compare the long-term risk of drug therapy as opposed to the upfront risk of a procedure, and consider the impact of a curative procedure on quality of life."