Interventional Cardiology

Cardiac arrythmias

Faulty electrical signaling in the heart causes arrhythmias

What are cardiac arrythmias?

The heart has its own electrical system that controls the speed and the rhythm of every heartbeat. With each heartbeat, an electrical signal spreads from the top of the heart to the bottom. As it travels, the electrical signal causes the heart to contract in an organised manner and pump blood. 

Electrical signals normally begin in a group of cells called the sinus-atrial (SA) node. As these signals spread from the top to the bottom of the heart, they coordinate the timing of heart cell activity. First, the two upper chambers of the heart, called atria contract.

This contraction squeezes blood into the lower chambers of the heart, which are called ventricles. The ventricles then contract and send blood to the rest of the body. The combined contraction of the atria and ventricles is a heartbeat.

The heart and its blood flow An example showing heart block

The first image shows the heart and its blood flow. The second image shows an example showing heart block

Sometimes the heart beats too slowly (Bradycardia). During Bradycardia, enough blood is not supplied to the body, due to failure of the hearts chambers to contract properly.

This could happen due to SA node not functioning properly, or by a condition called heart block. In this condition, a problem exists with the electrical pathway between the atria and ventricles. Electrical signal sent out by the SA node may not reach the ventricles or is delayed.

Faulty electrical signaling in the heart causes arrhythmias. A pacemaker uses low-energy electrical pulses to correct faulty electrical signaling. Pacemakers can speed up a slow heartbeat, Pacemakers can also coordinate the electrical signaling between the upper and lower chambers of the heart. The device will make sure the ventricles contract normally if the atria are quivering instead of beating in a normal rhythm (a condition called atrial fibrillation).

How do you diagnose a heart rhythm problem?

An EP study enables the diagnosis of your heart rhythm problem.

Once the cause and location of the rhythm problem are identified, this short circuit is either destroyed or blocked via catheter ablation. This involves sending energy through a specialised catheter to destroy a small amount of tissue at the problem site. This energy may be either hot (radiofrequency ablation) or cold (cryoablation).

Atrial Fibrillation (AF), which is a particular type of abnormal heart rhythm, is treated via Pulmonary Vein Isolation (PVI).

What is cardiac electrophysiology?

Cardiac electrophysiology is the science of understanding, diagnosing and treating the electrical activities of the heart. At Mercy Angiography we offer a complete electrophysiology (EP) programme.

  1. An EP study enables the diagnosis of your heart rhythm problem.

  2. Once the cause and location of the rhythm problem are identified, this short circuit is either destroyed or blocked via catheter ablation. This involves sending energy through a specialised catheter to destroy a small amount of tissue at the problem site. This energy may be either hot (radiofrequency ablation) or cold (cryoablation).

  3. Atrial Fibrillation (AF), which is a particular type of abnormal heart rhythm, is treated via Pulmonary Vein Isolation (PVI).

What are the common abnormal heart rhythms?

An abnormal heart rhythm, or arrhythmia, is a change in either the speed or pattern of the heartbeat. During an arrhythmia, the heart may beat too slowly called bradycardia, too rapidly, or irregularly called tachycardia. Catheter Ablation is used for treating certain rapid heart rhythms / tachycardias. Here’s a brief description of several common tachycardias that may be treated with ablation.

Supraventricular Tachycardia (SVT)

SVT is a general term describing a series of very rapid heartbeats that begin in the upper chambers of the heart. Specific examples include:

AV nodal re-entrant tachycardia (AVNRT)
  • AVNRT is the most common form of SVT.

  • In this condition, two pathways exist in the AV node. If an electrical impulse enters only one of the pathways, it may double back through the unused second pathway and start travelling in a circular pattern. This may cause the heart to contract with each cycle, and may result in a very rapid, regular heartbeat.
Wolff-Parkinson-White Syndrome (WPW)
  • In WPW, an abnormal “bridge” of tissue connects the atria and the ventricles.
  • This extra pathway is called an accessory pathway and makes it possible for electrical impulses to travel from the atria to the ventricles without going through the AV node.
  • In people with WPW, an arrhythmia can get started when an impulse travels down the normal conduction pathway to the ventricles and then back up through the accessory pathway to the atria.
  • If the impulse continues to travel in a circular pattern, it may cause the heart to contract with each cycle, and may result in a very rapid heartbeat.
  • Some accessory pathways conduct impulses rapidly and thereby may allow very rapid and serious rhythms to occur.
Atrial Fibrillation (AF)
  • In AF, multiple circuits in the atria occur simultaneously, stimulating the heart in an uncoordinated fashion. As a result, the atria quiver quickly and ineffectively.
  • The loss of a coordinated beat may allow the blood to stagnate and form blood clots.
  • The AV node, which acts as a gate, allows only some of these impulses to travel down the electrical system to stimulate the ventricles.
  • As a result, the heart rhythm is irregular and usually, but not always rapid. Atrial fibrillation may recur periodically or it may be persistent.

Atrial Fibrillation is treated with Pulmonary Vein Isolation (also called Pulmonary Vein Ablation or AF Ablation).

Atrial Flutter (AF)
  • In atrial flutter there is a single, short circuit that conducts electrical impulses rapidly around the inlet valve of the right ventricle.
  • Usually every second beat is conducted from this abnormal circuit to the ventricles resulting in a heart rate of around 150 beats per minute.
  • This rhythm can often be difficult to treat with medication.
  • Similarly to atrial fibrillation, there can be a risk of blood clots forming in the atria.
  • If the heart rate cannot be controlled there can be a risk of weakened heart muscle pumping function.
Ventricular tachycardia (VT)
  • Ventricular tachycardias arise from the major pumping chambers at the bottom of the heart.
  • VT is a more serious rhythm problem because it often occurs in a setting of previous heart damage (e.g. a heart attack) and may be best managed with an implanted defibrillator.
  • Sometimes with VT, the heart is otherwise healthy and the abnormal rhythms arise from an irritable trigger point. This trigger can often be localised and successfully ablated.