Defibrillator Pacemakers

What is tachycardia?

Tachycardia is a condition where the heart beats too fast.  A healthy heart beats 60 to 100 times per minute, pumping about 300 litres of blood every hour. Exercise, stress or fear can cause the heat to beat faster, but this is a normal response. With tachycardia, the heart beats at more than 100 beats per minute and can beat as fast as 400 beats per minute for no specific reason. At this rate the heart is not able to pump blood effectively to the body and brain.

There are different types of fast heart rhythms that can occur in either the upper chambers (atria) or lower chambers (ventricles) of the heart.

  • Atrial flutter and atrial fibrillation start in the upper chambers of the heart.
  • Ventricular tachycardia and ventricular fibrillation start in the lower chambers of the heart.

What is sudden cardiac arrest?

Sudden Cardiac Arrest (SCA) is an electrical problem with the heart that triggers a dangerously fast heart rhythm (ventricular fibrillation). The rapid, irregular heart rhythm causes the heart to quiver rather than contract or pump. When the heart stops pumping blood, oxygen cannot reach the body or brain. If not treated immediately, SCA can be fatal.

Sudden Cardiac Arrest is leading cause of death in Australia claiming approximately 30,000 lives each year. That’s about one every 20 seconds and also 24 times greater than the amount of people who die in motor vehicle accidents.

Heart attack and SCA: What are the differences?

Sudden cardiac arrest is not the same as a heart attack, although the two are often confused.

Heart Attack – A circulation or plumbing problem

Cause – Blockage in a vessel that supplied blood to the heart muscle, which may permanently damage part of the heart.

Risk Factors – High cholesterol, high blood pressure, obesity, smoking, family history of a heart attack, diabetes.

Symptoms – May be accompanied by pressure in the chest, pain radiating to the arm, shortness of breath, sweating, nausea.

Sudden Cardiac Arrest (SCA) – An electrical problem

Cause – Electrical malfunction of the heart that results in no blood flow to the body and brain.

Risk Factors – Previous heart attack, heart failure, abnormal heart rhythm, low ejection fraction, family history of SCA

Symptoms – Generally no symptoms, may experience racing heartbeat, lightheadedness, dizziness, fainting.

Who is at risk of sudden cardiac arrest?

Generally, sudden cardiac arrest strikes without warning. People who are at a higher risk for SCA include:

  • Those who have had a heart attack
  • Heart failure patients
  • Survivors of a previous SCA or those who have a family member who has had an SCA event
  • People with low ejection fraction

EF number: a number you should know

EF stands for “ejection fraction.” It is the percentage of blood that is pumped out of the heart with each heartbeat. Your doctor determines how well your heart is pumping based on your EF number.

Your EF number can change over time. It is important for you and your doctor to check your EF regularly.

How is EF measured? The most common way to measure EF is with an echocardiogram. This test is usually performed in a doctor’s office or hospital diagnostic area.

Typical EF ranges:

50-75%Heart's pumping ability is normal
36-49%Heart's pumping ability is below normal
35% & below       Heart's pumping ability is low

Treating SCA through defibrillation

The most effective way to treat SCA is through defibrillation. Defibrillation involves delivering an electrical shock to your heart to restore a normal heartbeat. To survive an SCA event you must receive defibrillation within 10 mintues. Only about 5% of people survive SCA, because defibrillation was not delivered within this critical time frame.

There are two primary forms of defibrillation:

  • An automated external defibrillator or AED, is a portable device that measures the heart’s electrical activity. It is used by emergency response teams or the general public to shock the heart.
  • An implantable defibrillator , or ICD, is a device that is implanted under the skin. The implantable defibrillator delivers therapies to treat fast, irregular rhythms.

How does an implantable defibrillator work?

An implantable defibrillator is designed to monitor your heart rhythm 24 hours a day. If your heart is beating too fast or irregularly, the device will first send small painless electrical signals to correct your heart rate. If the fast heart rate continues, the defibrillator will deliver a shock to restore your heart to a normal rate. The implantable defibrillator can also treat slow heart rhythms by sending electrical pulses to the heart to correct it.

Getting a defibrillator implanted

The procedure to implant a defibrillator does not require open heart surgery, and most people go home within 24 hours. Before the surgery, medication may be given to make you sleepy and comfortable. Generally, the procedure is performed under local anesthesia.

The general steps of an implant procedure include:

  • A small incision, approx five to ten centimeters long, will be made in your upper chest area, just below your collarbone.
  • One or two leads will be guided through a vein into your heart and the leads will be connected to the implantable defibrillator.
  • The defibrillator settings will be programmed, and the device will be tested to ensure it is working properly to meet your medical needs.
  • The defibrillator will be inserted beneath your skin, and the incision in your chest will be closed.

Follow-up care and monitoring

Follow-up appointments enable the defibrillator to be thoroughly checked. During these check-ups your doctor can:

  • Monitor the battery status of the defibrillator.
  • Check the leads to determine how they are working with the defibrillator and your heart.
  • Review your defibrillator settings to ensure they are programmed appropriately to your medical needs.
  • Make programming adjustments to your implantable defibrillator.
  • In addition to these check-ups with your doctor, your clinic or practice may choose to have your implantable defibrillator checked through remote monitoring.
  • This remote monitoring can replace some visits, but not all. Your doctor may still need to perform a physical examination to adjust your defibrillator settings or medications.

Frequently asked questions

Can I use a mobile phone? - Yes. When talking on a mobile phone keep the phones antenna fifteen centimeters away from your implantable defibrillator, and use the phone on the ear opposite your implantable defibrillator. We also recommend you avoid placing the mobile phone in a pocket near your implantable defibrillator.

Are household appliances safe to use? - Yes. Most household appliances are safe to use as long as they are properly maintained and in good working order. This includes microwaves, ovens, major appliances, electric blankets, and heating pads.

Will magnets affect my device? - Items that contain magnets, such as magnetic therapy products, stereo speakers, and hand held massagers can temporarily affect the operation of your implantable defibrillator. Therefore, it is recommended you keep items containing magnets at least fifteen centimeters away from your implantable defibrillator. We do not recommend the use of magnetic mattress pads and pillows because it is difficult to maintain a fifteen centimeter distance when using these items.

Will I be able to travel? - Given the short duration of security screening, it is unlikely that your medtronic implantable defibrillator will be affected by metal detectors or full body imaging scanners such as those found in airports, courthouses and jails.

To minimise the temporary interference with your implantable defibrillator while going through the security screening process, avoid touching metal surfaces around any screening equipment. Do not stop or linger in a walk-through archway; simply walk through the archway at a normal pace. If a hand-held wand is used, ask the security operator not to hold it over your implantable defibrillator and not to wave it back and forth over your defibrillator. You may also request a hand search as an alternative.