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Capital & Coast DHB Cardiology Service

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Cardiac Arrhythmias

Your heart rate is controlled by a complex electrical system within the heart muscle which drives it to go faster when you exert yourself and slower when you rest.  A number of conditions can affect the heart rate or rhythm.  Heart rate simply refers to how fast your heart is beating.  Heart rhythm refers to the electrical source that is driving the heart rate and whether or not it is regular or irregular.

 As some types of arrhythmias can cause you to faint without warning, your doctor may restrict your driving until the condition is controlled.
 
Some common terms
  • Sinus rhythm is the normal rhythm
  • Arrhythmia means abnormal rhythm
  • Fibrillation means irregular rhythm or quivering of one part of the heart
  • Bradycardia means slow heart rate
  • Tachycardia means fast heart rate
  • Paroxysmal means the arrhythmia comes and goes
Tachycardia
The most common form of this is atrial fibrillation.  This is where your heart rhythm is irregular and often too fast.  Symptoms include fatigue, palpitations (where you are aware of your heart racing or pounding), dizziness and breathlessness.
 
Other tachycardias include supraventricular tachycardia  (SVT)  or ventricular tachycardia (VT).  These have similar symptoms as atrial fibrillation but can also cause you to loose consciousness (faint).
 
Bradycardia
The most common form of this is called heart block.  This is because messages from the electrical generator of the heart don't get through efficiently to the rest of the heart and hence it goes very slowly or can pause.  Symptoms of the heart going too slow include feeling tired, breathless or fainting.
 
Tests
Tests to diagnose what sort of arrhythmia you have include
  • an electrocardiogram (ECG).  This trace of the heart's electrical activity gives the diagnosis of the source of the arrhythmia. This is often normal at rest and more extensive testing is needed to try and catch the arrhythmia especially if it is intermittent.
  • an Ambulatory ECG. This can be performed with a Holter monitor which monitors your heart for rhythm abnormalities during normal activity for an uninterrupted 24-hour period. During the test, electrodes attached to your chest are connected to a portable recorder - about the size of a paperback book - that's attached to your belt or hung from a shoulder strap. Another form of ambulatory ECG test is an Event recorder which covers 1-2 weeks.  You wear a monitor (much smaller than a Holter monitor) and if you have any symptoms, such as dizziness, you press a button on a recording device which saves the recording of your heart rhythm made in the minutes leading up to and during your symptoms.  Because you can wear this for a longer period of time it has a higher rate of catching your abnormal rhythm.
  • An implantable event monitor can be used to diagnose arrhyhmias which are less frequent or for fainting episodes without a clear cause. These tiny devices (size of a small flash drive) are implanted under the skin with a minimally invasive surgery (under 10 minutes) and can help diagnose potential rhythm disorders. 
  • an Electrophysiologic study is a procedure where different arrhythymia mechanisms can be identified and treated with radio-frequency ablation. Most of these procedures are curative and allow for discontinuation of medications.
 
Treatment
 
  • Most treatments for tachycardias consist of medication to stop the abnormal rhythm or make it slower if and when it occurs. 
  • Ablation procedures can be performed in a safe and effective way to eliminate most common arrhythmia disorders. 
  • For some arrhythmias such as atrial fibrillation, which can increase your risk of stroke, blood-thinning medications are often used as well.
  • Arrhythmias such as Ventricular tachycardias and Ventricular fibrillation increase the risk of sudden cardiac death, and in most patients suffering such conditions an implantable cardioverter-defibrillator (also known as ICD) is recommended, and you may be referred to the arrhythmia specialists for such procedure.
  • If you have bradycardia you may be referred to the arrhythmia specialist for a pacemaker. Also, some patients with heart failure may benefit from a specific type of pacemaker or ICD, known as CRT (cardiac resinchronisation therapy) to imporve heart contractility and symptoms such as fatigue and shortness of breath.
  • Implantation of pacemakers and ICD's are small operations where a battery powered device is placed under the skin with wires that lead to your heart and provide it with electrical stimulation to prevent it from going too slowly, or aborting fast heart rhythm.  Most procedures are done with a combination of local anesthesic and IV sedation (medications to make you comfortable) but sometimes the assistance of an anesthesia specialist is required for additional comfort.

This page was last updated at 1:41PM on December 24, 2018.