What is an Arrhythmia?
A cardiac arrhythmia is the medical term for an irregular heart beat or abnormal heart rhythm.
There are essentially two main things that can go wrong with the heart: the plumbing and the electrics. Many of us are keenly aware of the heart’s plumbing problems, yet we remain largely unaware of the electrical faults which cause an arrhythmia. Arrhythmias can occur in the upper chambers of the heart, (atria), or in the lower chambers of the heart, (ventricles). Arrhythmias may occur at any age. Some are barely perceptible, whereas others can be more dramatic and can even lead to sudden cardiac death.
There are two basic types of arrhythmia, with variations of each:
Bradycardia – a heart rate that is too slow, usually less than 60 beats per minute.
Tachycardia – a heart rate that is too fast, usually more than 100 beats per minute.
Causes
- The heart’s natural pacemaker (the SA node) develops an abnormal rhythm.
- The normal conduction pathway is interrupted or blocked.
- Electrical impulses originate from another part of the heart.
Symptoms
Some symptoms are barely perceptible; while others are so dramatic that they can cause cardiovascular collapse and death.
- Premature beats, palpitations or skipped beats
- Dizziness
- Fatigue
- Light-headedness
- Fainting or near fainting
Diagnosis And Misdiagnosis
So why might misdiagnosis be so prevalent? Syncope (or fainting) in many patients is indicative of a potentially fatal heart rhythm irregularity. A lack of awareness of syncope in the medical community means that syncope often goes unrecognised or, worse, misdiagnosed as epilepsy.
Correct diagnosis is obtained in a number of ways. An Electrocardiogram (ECG or EKG) diagnoses arrhythmias by recording the timing of atrial and ventricular contractions. A Holter Monitor is a device that can record 24 hours of ECG signals and an event monitor can last up to about 30 days. For arrhythmias that occur less frequently, an Insertable Loop Recorder can be implanted under the skin of the chest to record heart activity for more than a year. A simple exercise test on a treadmill may be used in order to provoke an arrhythmia, whereas a tilt-table test might be used to induce fainting. An Electrophysiological study (EP study) can also be done to manually stimulate the heart to induce fast heart rhythms, which may be an indication that the patient is prone to dangerous arrhythmias.
Treatment
Bradycardic conditions can be treated with medications that help improve the transmission of impulses through the conduction system. A more common way is with a cardiac pacemaker; a tiny implantable device that is placed just beneath the skin in the upper chest. Small wires (leads) connect the device to the inside of the heart where it provides support if the heart beats too slowly on its own.
For the more dangerous tachycardias – such as ventricular tachycardia (150-250bpm) or the potentially lethal ventricular fibrillation (250+bpm) – anti-arrhythmic drugs and other medications are used, but recent clinical trials have shown that a small device called an Implantable Cardioverter-Defibrillator (ICD) is the most effective treatment for these arrhythmias. These are slightly larger than a pacemaker, but implanted in much the same way. An ICD monitors the heart and provides electrical pulses or shocks to slow down a heart that begins to race out of control.