Pacemakers

Overview:

The heart is an organ that beats over 100,000 times a day, delivering the needed oxygen to the rest of the body. As a result, it is required that the heart maintain a steady and consistent beating pattern to supply the needed oxygen. This is achieved by the heart's natural pacemaker (also called the sinoatrial or SA node), which sends out small electrical impulses throughout the heart in a directed fashion along specialized conducting pathways. As these impulses reach different parts of the heart, they activate the muscle fibers and cause them to contract. [1] Through timed contractions, the heart beats and effectively pumps blood from within its chambers out into the blood vessels that lead to the rest of the body.

http://www.youtube.com/v/tWWZKGN9h74&hl=en

However, a small number of children have problems in the heart, either with the natural pacemaker or the conducting pathways. These problems may have been around since birth or have been caused by damage to the heart. For children with these problems, the electrical impulses from the natural pacemaker are usually not transmitted (or fully transmitted) throughout the heart, resulting in a much varied heart beat, which, in most cases, cannot pump an adequete amount of blood sufficient to maintain health in the child. Whether the heart beat is too fast or too slow (or even inconsistent), the effects as a result of this arrhythmia are often similar.

Luckily, this problem can be remedied through the use of an artificial pacemaker. This pacemaker is a small electrical device that is implanted within the body and can augment or even replace the function of the heart's defective pacemaker. It generates electrical impulses that reach the parts of the heart that are not receiving natural impulses, activating the muscles in that region and forcing them to contract in a timely manner in conjunction with the rest of the heart. [1]

Conditions Requiring a Pacemaker:

  • dizziness
  • lightheadedness
  • fatigue
  • fainting
  • weakness
  • palpitations (a feeling of pounding in the chest)
  • chest pain
  • shortness of breath

Premature Atrial Contraction (PAC) and Premature Ventricular Contraction (PVC):
These are considered to be minor arrhythmias, which may be felt as a fluttering or pounding in the chest. This feeling is the result of an extra beat that comes sooner than normal. The condition is common and considered normal, but in some cases may indicate an underlying problem.

Tachycardias:
Tachycardia is the term that indicates an abnormally fast heart rate. There are two major categories of tachycardia - supraventricular and ventricular.

  • Supraventricular Tachycardia (SVT). SVT is the most common arrhythmia. It is characterized by quick bursts of heart beats, resulting in an increased heart rate. The electrical impulses that drive this rate originate either in the right and left atria or the cells that carry eletrical impulses from atria to ventricles. Depending on conditions, SVT could last for a few seconds or even days. Frequent or long-lasting occurrences may require treatment.
  • Wolff-Parkinson-White (WPW) Syndrome. WPW syndrome is a type of SVT that is characterized by an extra electrical conduction pathway from the atria to the ventricles, causing the heart to experience greater electrical impulses that speed up the heart rate. This condition usually runs in families.
  • Ventricular Tachycardia. This category of tachycardia is uncommon, but is still a serious condition. The fast heart rate originates from the ventricles and is usually a sign of a serious, underlying heart problem.

Bradycardias
Bradycardia is the term that indiciates an abnormally slow heart rate. Common examples of bradycardia are sick sinus syndrome and heart block.

  • Sick Sinus Syndrome. Sick sinus syndrome occurs when either the heart's sinoatrial node or a part of the heart's electrical conduction system malfunctions. In children, a common cause of sick sinus syndrome is cardiac surgery. This is usually associated with abnormally slow heart beat, though it has also been associated with tachycardias as well.
  • Heart Block. This condition is often the result of a congenital heart defect, but also results from injury or disease. Heart block occurs when the electrical impulses from the atria are "blocked" from reaching the ventricles. Because of this, the presence of another node, the atrioventricular node, takes over as the heart's pacemaker. This node sends electrical impulses at a relatively slower rate than the sinoatrial node, resulting in a slower heart rate.
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  • Medications. There are many types of anti-arrhythmic medications available to treat arrhythmia, and a doctor will determine the best given several factors, such as type of arrhythmia, other concurrent medications being taken, and any possible other medical causes. There have been cases where medication has actually increased the symptoms and caused undesired side-effects, so their use and effectiveness needs to be closely monitored.
  • Pacemakers. A variety of arrhythmias can be controlled through an artificial pacemaker - a small, battery operated device placed inside the body that senses when the heart rate has dropped too low and sends electrical impulses to speed up the heart. Normally used to treat bradycardia, new technology has evolved that allow pacemakers to treat some types of tachycardia.
  • Defibrillators. Similar to pacemakers, these implantable cardioverter defibrillator (ICD) are also placed inside the body and senses the heart for fast or irregular rhythm, upon which, will deliver an electrical shock that will restore the normal heart beat. Newer ICDs also function as a pacemaker and can detect and treat bradycardia.
  • Catheter ablation. Through the use of a catheter that is guided through a vein in the arm or leg into the region of the heart causing the arrhythmia, waves of high-frequency radio waves are sent into the muscle cells, destroying them.
  • Surgery. Surgery usually remains the last option, as it is highly invasive and traumatic. The patient is placed under anesthesia and has his or her chest opened to reveal the heart. The muscle causing the arrhythmia is then removed.

Although there are arrhythmias that don't pose a significant threat to a person's health, there are some that can be very dangerous and would indicate a serious problem. It is imperative that you contact your doctor should symptoms arise. [2,3]

http://www.usatoday.com/news/health/2007-01-23-mass-heart_x.htm

Procedure:
The pacemaker implantation process is generally a straightforward procedure. In young children, most pacemakers are placed under the muscles and skin of the abdomen, while in older children, the pacemakers are placed within the chest. Given the size and anatomy of younger children, the implantation is done with an epicardial approach (placing the leads on the outside of the heart muscle) while for older children and adults, the implantation is done with an endocardial approach (placing the leads within the heart).[1,4,5,6]


http://www.thechildrenshospital.org/pdf/Pacemakers-eng.pdf

Post-Op:

Once the procedure is complete, the child will be taken to the recovery room where he or she will undergo several hours of recuperation. Upon your child waking up, you will be allowed to join him in the room. The use of minimally invasive techniques have allowed for shorter hospital stays and quicker recovery times, often allowing the patient to return home the following day. During this time, the pacemaker will be checked for functionality, and the child's heart rhythm will be monitored. There will also be a transtelephonic transmitter and instructions on its use will be given, which will enable the doctor to check the pacemaker through the telephone. Upon leaving, your child will be given a temporary ID card that has information about the pacemaker, date of implant, and physician who performed the implant. A permanent ID card will be sent within three months. [6,7]

There are many precautions and restrictions associated with having a pacemaker, of which are mentioned below:

Precautions:
Importantly, the wound site must be protected from injury until it is healed, which normally requires about a month. The child must be supervised until the wound is fully healed.

Once the wound is healed,there are several other precautions that your child must take [4,8,9]:

  • Avoid being around magnets and anything with a magnetic field.
  • Avoid using heat in physical therapy.
  • Stay away from chain saws.
  • Avoid high-voltage or radar machinery and spaces near radio or television transmitting towers and antennas.
  • Inform the surgeon or dentist if your child is having a surgical procedure performed so that a electrocautery device will not be used.
  • Cellular phones should be used on the side opposite where the pacemaker is, and never placed directly against the chest nor on the same side as the pacemaker.
  • Most domestic appliances should cause no interference, so they can be safely used. This also includes iPods and other similar devices that children often use.

Restrictions:
In addition to taking the necessary precautions, there are several restrictions that must be enforced on the child, which include:

  • Do not lift objects that weigh more than 10 pounds.
  • Do not keep your child's arms above shoulder level for a long period of time.
  • Avoid strenuous activities, such as pushing or pulling heavy objects or mowing the lawn.
  • Make sure the child does not over-exert him or herself.
  • For the first six weeks after surgery, avoid golfing, tennis, or swimming.
  • For exercise, try to maintain a steady schedule of walking.
  • If you're unsure of when the child can resume strenuous activities, contact your child's physician.

Generally, children with pacemakers should be able to resume the same activities that they are used to. However, a word of caution remains: when involved in physical activities, avoid receiving a blow to the area containing the pacemaker, as this may affect its functioning. As a result, contact sports are not recommended. If you are unsure of which activites your child can participate in, contact your child's doctor. [1,7]

Requirements:
Though pacemakers are built to last 5-10 years, their actual time of use depends on how often they are used and/or affected by other conditions. It is imperative that the pacemaker be regularly checked to ensure that it is working properly. To check the accuracy of the pacemaker, consider the following:

  • Take the child's pulse regularly to make sure it matches the target rate set by the pacemaker.
  • Have periodic telephonic check-ups with the pacemaker. The physician will provide instructions on this process.
  • Bring the child to regular physician check-ups .
  • Should unusual or pre-implantation symptoms arise, contact your child's physician immediately.
  • If you ever have any questions, consult your child's physician.

It is also critical that a complete pacemaker check be done six weeks after implantation. During this appointment, adjustments will be made to the pacemaker that will prolong its life. Once this initial check up is complete, subsequent telephone check-ups should be done every 3 months to evaluate the battery function. [8]

Case Study:

Eight years ago, as a senior in high school, Michaela Gagne was crazy about sports. She lived for sports and was a three-sport athlete, and she had high hopes of competing in Division 1 athletics. However, with one fateful test, she was faced with the prospect of never playing sports again. At 17 years of age, Gagne was diagnosed with Long QT syndrome, a heart disorder characterized by irregular, fast heart beats. This disorder frequently goes undetected and its first symptom in most cases is sudden death.

While initially devastated by this horrible news, Gagne realized that instead of concentrating on what she can't do, she should concentrate on what she can do. At first, no one had mentioned anything about an ICD, and she was placed on beta blockers, which she had a hard time adjusting to and life became very frustrating. In an attempt to keep her spirit alive, her high school guidance counselor suggested she enter the Miss Fall River pageant, which she won along with many other local contests after.

Over time, she researched long QT syndrome and learned about the benefits of an ICD. An ICD is a slender device that is implanted in the patient's shoulder and chest area with electric leads running into the heart. When an abnormal rhythm is detected, a shock is administered to correct it.

 
http://www.heartscreenamerica.com/michaela.html

She was fitted with an ICD in her freshmen year at the University of Massachusetts at Amherst, which allowed her to play competitive soccer again in intramurals. However, she continued competing in pageants as well and became a spokesperson for the American Heart Association. It was with this work that she spoke of at the Miss Massachusetts pageant and won.

While she ultimately did not win the Miss American contest, Gagne considers the opportunity to talk about cardiac issues a reward in itself. For her, the scar from the surgery serves as a physical reminder of what she went through. Despite not being able to participate heavily in sports, she remains as a national spokesperson for the American Heart Association, of which she takes great pride in being a part of.

Though she hasn't actually had an arrhythmic episode, it could arise from intense emotion or physical exertion. As a result, she has to constantly monitor the status of the ICD, to ensure that it has enough battery life, which often lasts five to seven years and can be easily replaced.

Gagne now has two devices, one of which is implanted in her chest- the original is engraved with her name and is carried around in her purse as a personal good luck charm. [10,11,12,13]

Future Alternatives:

Despite the benefits of artifical pacemakers, the downsides of it are that children quickly outgrow the device and the pacemaker requires repeat operations ever 5-10 years, which in children would amount to at least 5 to 6 operations in their lifetime.

According to new findings from Children's Hospital Boston, scientists have developed a method of growing skeletal muscle cells that transmit heart electrical signals when implanted within rat hearts. If applicable to humans, this would serve wonders as it offers innate advantages over artifical pacemakers. One of the benefits of this biological alternative is that it would grow with the child, which would eliminate the need for repeat operations and would enable the child greater freedom in life, eliminating most of the restrictions that come with implanting an artificial pacemaker.

At the moment, this therapy method is still far from finished. The heart is complex muscle and its operation is even more complex. Before this method can progress further, it must first mimic the normaly time delay of the AV node, an important aspect of normal heart function. In addition, this therapy must be applied to larger animals, especially those who resemble humans, since it is humans that will ultimately benefit from this.

Nevertheless, the field of preserving heart function has advanced greatly over the years. From medications to pacemakers to ICDs to biological therapies, much has been achieved that has allowed us to further extend the lives of many children and adults. Ultimately, a biological approach to heart pacing would be superior to an artificial approach, but until that time comes, pacemakers and ICDs offer children a sufficient, and often satisfying, quality of life. [14]

 

 

References:
1. http://www.childrensheartunit.org/adult/heart_pace.html
2. http://www.thechildrenshospital.org/wellness/info/teens/48932.aspx
3. http://www.americanheart.org/presenter.jhtml?identifier=26
4. http://www.stjosephsatlanta.org/HealthLibrary/content.aspx?pageid=P06429
5. http://www.webmd.com/heart-disease/abnormal-rhythyms-pacemaker?page=2
6. http://www.med.umich.edu/1libr/chheart/inv03.htm
7. http://www.webmd.com/heart-disease/abnormal-rhythyms-pacemaker?page=4
8. http://www.chop.edu/consumer/your_child/condition_section_index.jsp?id=-9350
9. http://www.eurekalert.org/pub_releases/2008-03/chb-ias032808.php
10. http://www.usatoday.com/news/health/2007-01-23-mass-heart_x.htm
11. http://www.boston.com/yourlife/articles/2007/03/19/without_skipping_a_beat
12. http://www.metrowestdailynews.com/homepage/x2033926355
13. http://www.thebostonchannel.com/health/9859762/detail.html
14. http://www.technologyreview.com/printer_friendly_article.aspx?id=17005