ARRHYTHMIA FAQ

1. What is an arrhythmia?

An arrhythmia is a change in the rhythm of the heart, eg. the heart may skip a beat, beat irregularly or very fast or very slowly.

2. Does having an arrhythmia imply heart disease?

Not necessarily so. Arrhythmias can occur in people with normal hearts.

3. What causes arrhythmias?

Heart disease may cause arrhythmias. Other possible causes include: stress, caffeine, tobacco, alcohol, diet pills, and cough and cold medicines.

Sometimes, there may be no recognizable cause

4. Are arrhythmias serious?

Fortunately most arrhythmias are not life-threatening. In some people, arrhythmias are associated with heart disease. In such cases, heart disease, not the arrhythmia, should be sought and treated. In a small group of patients, arrhythmias themselves are dangerous. These arrhythmias require urgent medical treatment. For example, a few people have a very fast heartbeat, causing them to feel lightheaded or faint. If left untreated, the heart may arrest and the patient could die.

5. How common are arrhythmias?

Arrhythmias tend to increase with increasing age.

6. What are the symptoms of an arrhythmia?

Most people have felt their heart beat very fast, experienced a fluttering in their chest, or noticed that their heart skipped a beat. Almost everyone has also felt dizzy, faint, or out of breath or had chest pains at one time or another. You should not panic if you experience a few flutters or your heart races occasionally. But if you have questions about your heart rhythm or symptoms, check with your doctor.

7. What happens in the heart during an arrhythmia?

Usually the whole heart contracts between 60 and 100 times per minute. Each contraction equals one heartbeat.

An arrhythmia may occur for one of several reasons:

• Instead of beginning in the sinus node (where the normal impulse begins), the heartbeat begins in another part of the heart.
• The sinus node develops an abnormal rate or rhythm.
• A patient has a heart block.

8. What is a heart block?

Heart block is a condition in which the electrical signal cannot travel normally down the conduction system to the ventricles. For example, the signal from the atria to the ventricle may be (1) conducted with some delay; (2) delayed with only some getting through; or (3) completely interrupted. If there is no conduction, the beat generally originates from the ventricles and is very slow.

9. What are the different types of arrhythmias?

There are many types of arrhythmias. Arrhythmias are identified by where they occur in the heart (atria or ventricles) and by what happens to the heart's rhythm when they occur. Arrhythmias arising in the atria are called atrial or supraventricular (above the ventricles) arrhythmias. Ventricular arrhythmias begin in the ventricles. In general, ventricular arrhythmias caused by heart disease are the most serious.

10. How does the doctor know that I have arrhythmia?

Sometimes an arrhythmia can be detected by listening to the heart with a stethoscope. However, the electrocardiogram is the most precise method for diagnosing the arrhythmia. An arrhythmia may not occur at the time of the exam even though symptoms are present at other times. In such cases, tests will be done if necessary to find out whether an arrhythmia is causing the symptoms.

11. What tests can be done?

First the doctor will take a medical history and do a thorough physical exam. Then one or more tests may be used to check for an arrhythmia and to decide whether it is caused by heart disease.

12. Tests for Detecting Arrhythmias

• Resting ECG
  The patient lies down for a few minutes while a record is made.
  
  
• Exercise ECG (stress test)
  The patient exercises either on a treadmill machine or bicycle while connected to the ECG machine. This test checks whether exercise causes arrhythmias or makes them worse or whether there is evidence of inadequate blood flow to the heart muscle ("ischemia").
  
  
• 24-hour ECG (Holter) monitoring.
  The patient goes about his or her usual daily activities while wearing a small, portable tape recorder that connects to the electrodes on the patient's chest.
  
  
• Transtelephonic monitoring
  The patient carries a recorder over a period of a few days to several weeks. When the patient feels an arrhythmia, he or she telephones a monitoring station where the record is made. If access to a telephone is not possible, the patient has the option of activating the monitor's memory function. Later, when a telephone is accessible, the patient can transmit the recorded information from the memory to the monitoring station. Transtelephonic monitoring can reveal arrhythmias that occur only once every few days or weeks.
  
  
• Electrophysiologic study (EPS)
  A test for arrhythmias that involves cardiac catheterization. Very thin, flexible tubes (catheters) are placed in a vein of an arm or leg and advanced to the right atrium and ventricle. This procedure allows doctors to find the site and type of arrhythmia and how it responds to treatment.

13. How are arrhythmias treated?

Many arrhythmias require no treatment whatsoever. Serious arrhythmias are treated in several ways depending on what is causing the arrhythmia. Sometimes the heart disease is treated to control the arrhythmia. If heart disease is not causing the arrhythmia, the doctor may suggest that you avoid what is causing it. For example, if caffeine or alcohol is the cause, the doctor may ask you not to drink coffee, tea, colas, or alcoholic beverages.

The arrhythmia itself may be treated using one or more of the following treatments.

• Drugs
  One or more drugs may be used. Drugs are carefully chosen because they can cause side effects. In some cases, they can cause arrhythmias or make arrhythmias worse. For this reason, the benefits of the drug are carefully weighed against any risks associated with taking it. It is important not to change the dose or type of your medication without checking with your doctor first.
  
  If you are taking drugs for an arrhythmia, one of the following tests will probably be used to assess the effect of treatment: a 24-hour electrocardiogram (ECG) while you are on drug therapy, an exercise ECG, or a special technique to see how easily the arrhythmia can be caused.
  
  
• Cardioversion
  To quickly restore a heart to its normal rhythm, the doctor may apply an electrical shock to the chest wall. Called cardioversion, this treatment is most often used in emergency situations. After cardioversion, drugs are usually prescribed to prevent the arrhythmia from recurring.
  
  
• Automatic implantable defibrillators
  These devices are used to correct serious ventricular arrhythmias that can lead to sudden death. The defibrillator is surgically placed inside the patient's chest. There, it monitors the heart's rhythm and quickly identifies serious arrhythmias. With an electrical shock, it immediately disrupts a deadly arrhythmia.
  
  
• Artificial pacemaker
  An artificial pacemaker can take charge of sending electrical signals to make the heart beat if the heart's natural pacemaker is not working properly or its electrical pathway is blocked. During a simple operation, this electrical device is placed under the skin. A lead extends from the device to the right side of the heart, where it is permanently anchored.
  
  
• Surgery
  When an arrhythmia cannot be controlled by other treatments, doctors may perform surgery. After locating the heart tissue that is causing the arrhythmia, the tissue is altered or removed so that it will not produce the arrhythmia.

SUDDEN CARDIAC DEATH EXPLAINED

Sudden cardiac death (SCD) results from sudden cardiac arrest in a person who is usually in a state of normal health. In other words, the person may not exhibit any warning symptoms or signs prior to the attack. In about 1 in every 20 cases of sudden cardiac death, no definite cause of death can be found, even after the heart has been examined by an expert cardiac pathologist. This is then called Sudden Arrhythmic Death Syndrome (SADS) (Table 1).

SCD risk varies according to age, underlying health, physical activity and conditioning of the individual. It is estimated that the annual risk of SCD in adults is about 1:15,000 in those who participate in casual jogging, vs 1:50,000 in marathon runners. The risk for younger athletes who participate in school and college competitive sports is estimated at 1:200,000 to 1:300,000 per school year. SCD risk is a particular concern for older people since the prevalence of coronary artery disease (CAD) is higher in this age group and aerobic cardiovascular function naturally declines with age.

The Singapore National Heart Centre reported 261 cases of sudden cardiac death among the Singapore male population aged 18 to 45 over a three year period 2001 to 2003, i.e. an average of 87 cases per year.  In the SAF, over the period from 1996 to 2005, there were 19 cases of sudden cardiac deaths, i.e. about 2.1 cases a year. Of these, five had collapsed during training; the others were not during training.

SGH A&E Department, reported in a January 2005 paper that there was a 4.1% survival rate in 968 non-trauma cardiac arrest cases in a five year period, from 1994 to 1999. In a cardiac arrest and resuscitation epidemiology study in 2003, it was reported that from a total of 548 out-of-hospital cardiac arrests in Singapore, only 2.0% survived to discharge. Even among patients who suffered cardiac arrest in tertiary hospitals, that is while they were already in hospital where the best care is available, the survival rate to discharge ranged from 18 to 32%, according to studies from various countries. Unfortunately, death as a consequence of cardiac arrest is the most common outcome even with optimal management.

When sudden cardiac death strikes, the best hope for survival lies in the use of defibrillators. There are two types: semi-automated defibrillators used by medical doctors and automated external defibrillators (AEDs) which can be operated by trained personnel. Defibrillators work by delivering electrical shocks to the heart in order to convert abnormal heart rhythms back to normal rhythms. However, not all abnormal heart rhythms can be effectively treated by electric shock, and an AED would interpret the heart rhythm of a person who has gone into sudden cardio-respiratory arrest and advise the operator whether or not an electric shock is indicated. Studies indicate that if there is early defibrillation when there is a shockable rhythm, 20-50% of victims may survive.

Sudden cardiac death can be prevented by cardiovascular screening. During history taking, the patient is fully assessed to determine the presence of pre-existing medical conditions. Individuals with a history of sudden death in the immediate family before 40 years of age are also deemed at significant risk. Basic medical assessment includes a physical examination, a resting electro-cardiogram (or ECG), an echocardiography and an exercise treadmill test. There are many other tests that can be used to risk-stratify for SCD, but their use will depend on the preliminary test outcome and the doctor’s index of suspicion.

Management depends on the findings of the investigation outcome. In general, there are 4 modalities of treatment:

1. Revascularization
2. Medication
3. ICD implant
4. Radiofrequency ablation.

Considering that ischaemic heart disease is the single largest reason for sudden cardiac death, patients should be investigated for this condition and receive revascularization (angioplasty/stenting or heart bypass surgery) where appropriate.

Medication is directed mainly toward treating the underlying cardiac condition. Drugs such as aspirin, angiotensin converting enzyme inhibitors, beta-blockers and statins have been shown to improve survival in patients with underlying ischaemic heart disease. Paradoxically the use of anti-arrhythmic agents have led to worsened survival, due to both treatment failure and harmful side-effects (proarrhythmia). The incomplete success of drug therapy has led researchers to search for better alternative treatments.

Patients identified as being at high risk may receive an implantable cardioverter defibrillator (ICD) (Fig.1). The major benefit is that the device is implanted and therefore provides continuous monitoring of the heart. If and when ventricular fibrillation occurs, the ICD delivers electrical energy to shock the heart muscle back to normal sinus rhythm. It’s like having a paramedic to follow the patient at all times. Recent trials have demonstrated the superiority of ICD over drug therapy in preserving lives.

Radiofrequency ablation can be considered only for very specific subsets of patients, such as Wolff-Parkinson-White (WPW) Syndrome (Fig. 2) or idiopathic ventricular tachycardia (VT). In some instances like arrhythmogenic right ventricular dysplasia (ARVD), they are at best palliative and hence cannot be applicable as a complete therapy either.