Invasive | Flecainide Challenge
What is Brugada syndrome?
Brugada syndrome is a relatively recently discovered inherited condition that makes the sufferer more prone to heart rhythm problems. It is caused by an abnormality of the sodium ion channels of the cardiac cell walls. These channels adjust the chemical content of the cells and as a result adjust the electrical charge and behaviour of the cells. Because the cardiac cell contraction is controlled by electrical activity then abnormalities of the electrical properties of the cell results in disturbance of the heart rhythm.
What problems does Brugada cause?
Because of electrical abnormalities of the electrical cells patients that have Brugada syndrome are vulnerable to developing fast heart rhythms without any warning. The fast heart rhythms that they get are VENTRICULAR TACHYCARDIA or VENTRICULAR FIBRILLATION. These cause the heart cells to contract so quickly and/or chaotically that the heart no longer pumps blood. This results in a drop in blood flow to the brain and loos of consciousness. If this does not correct itself within a few minutes or is not corrected by treatment then the sufferer will die. This situation is called SUDDEN CARDIAC DEATH and is a rare but tragic event which often occurs in younger patients.
How common is it?
Brugada is a rare condition and it is estimated that it has a prevelance of 1-5/10000 in the West and probably more common in Asia.
How do I know if I have Brugada?
One of the problems with Brugada syndrome is that patients feel perfectly well until they have their first clinical event which can be sudden death. It is important that is a close family member dies young or is diagnosed with the condition to be screened for Brugada (see below). Occasionally the problem is picked up on a routine ECG performed for health medicals. The ECG has a characteristic appearance of partial right bundle branch block and ST segment elevation in the anterior chest leads. This appearance can vary in its severity which can make the diagnosis difficult and it is possible for patients who have Brugada to occasionally have a normal looking ECG. In patients whom we suspect Brugada (i.e. patients with c lose family members or symptoms of blackout and a suspicious ECG) it is possible to confirm or refute the diagnosis by performing a Flecainide infusion test.
Abnormal genes have been identified for Brugada syndrome but the list of genes identified is not exhaustive and it is therefore not possible to be sure that a patient has not got Brugada if the screening is negative. In addition genetic screening takes some time to perform (as much as 6 months for some patients) and therefore is of research interest but not a great help in deciding how to manage patients at present.
What problems does it cause?
As mentioned above Brugada cause cardiac rhythm problems which result in sudden death or blackout. It most commonly manifests itself in the third and fourth decade of life but can present earlier in certain ethnic groups. However the majority of patients who have Brugada do not have rhythm problems. The event rate for patients who have not experienced symptoms is very low ranging from 0 to 8% over 3 years follow up.
How is it treated?
Although Brugada syndrome has the potential to cause dire consequences these consequences can be prevented by the use of and implantable defibrillator (ICD). This does not prevent the cardiac rhythm problems caused by Brugada but can prevent patients dying from them. One of the problems with Brugada is that many patients may have have no cardiac rhythm problems and may never use an ICD even if they have one implanted. In addition ICD’s carry risks both as a result of the implant procedure and the subsequent changes in leads and generators that may be necessary in the future in these young patients. Therefore it is unwise to implant defibrillators without good reason and evidence of potential benefit. To try and determine which patients are likely to have problems and therefore need an ICD a number of studies have examined whether high risk patients can be identified. In essence the patients who have had symptoms as a result of cardiac arrhythmia are at high risk. Patients that have abnormal rhythms (ventricular tachycardia or ventricular fibrillation) bought on artificially at electrophysiological study are at slightly increased risk and probably also should have an ICD. As can be gathered from this article the decision as to whether to implant an ICD is not straight forward and the decision has to be made after detailed discussion with the doctor and patient as to the risks and benefits for that individual. Ultimately the recommendations of the doctor are a best guess of what might happen in the future based on the statistics from previous studies of many patients. Unfortunately doctors are still not able to predict the future however.
Flecainide infusion challenge
What is a Flecainide infusion challenge?
As discussed above, the abnormality of Brugada is in the sodium channel of the cardiac cell walls. In addition the ECG is not always abnormal in all patients so it may be possible to miss the diagnosis. Therefore in patients in whom there is a high level of suspicion that they may have Brugada i.e. patients with close family relatives with Brugada, patients with syncope of unknown cause, or patients with an equivocal ECG it is possible to bring the ECG abnormalities out by using Flecainide. This is a sodium channel blocker that is used as a heart rhythm controlling drug (antiarrhythmic). Partially blocking some of the sodium channels with Flecainide has little or no effect on the ECG in patients who have normal cardiac cells but in patients with the Brugada abnormality the ECG becomes obviously abnormal.
How is it performed?
The patient has a drip put into a vein in the hand or arm and is connected to a 12 lead ECG machine. After a baseline ECG is performed the flecainide is slowly infused over 10 to 15 minutes. A 12 lead ECG is performed every minute and examined for any changes. If the ECG changes significantly then the infusion is stopped and the patient kept in hospital for about 12 hours until the Flecainide effects have worn off. If the ECG does not change then the patient can go home after recovering for an hour, knowing that they do not have Brugada syndrome.
Is it dangerous?
Complications from a correctly performed Flecainide challenge are so rare that few have ever been reported in medical literature. It is important that it is performed by an experienced physician who is able to interpre t the ECG correctly and stop infusions if the ECG changes. It is also important that full resuscitation facilities including a defibrillator are available. For this reason these tests are often performed in an exercise testing lab or in a catheter lab. The London Arrhythmia centre has the largest and most experienced group of electrophysiologists in the UK and Europe and none of its doctors have ever seen a complication from this test as of May 2006.
A typical Brugada type ECG
- Flecainide Challenge
- Electrophysiologic Study
- Implantable Loop Recorder
- 24 Hour ECG
- 24 Hour BP Test
- Excercise ECG Test
- Cardiomemo / Event Monitor