A pacemaker is a small device about the size of a matchbox that weighs 20-50g. It consists of a pulse generator – which has a battery and a tiny computer circuit – and one or more wires, known as pacing leads, which attach to your heart.

The pulse generator emits electrical impulses through the wires to your heart. The rate at which the electrical impulses are sent out is called the pacing rate.

Almost all modern pacemakers work on demand. This means they can be programmed to adjust the discharge rate in response to your body's needs.

If the pacemaker senses that your heart has missed a beat or is beating too slowly, it sends signals at a steady rate. If it senses that your heart is beating normally by itself, it doesn't send out any signals.

Most pacemakers have a special sensor that recognises body movement or your breathing rate. This allows them to speed up the discharge rate when you're active. Doctors describe this as rate responsive.

The heart is essentially a pump made of muscle, which is controlled by electrical signals.

These signals can become disrupted for several reasons, which can lead to a number of potentially dangerous heart conditions, such as:

• an abnormally slow heartbeat (bradycardia) or an abnormally fast heartbeat (tachycardia)
• heart block – where your heart beats irregularly because the electrical signals that control your heartbeat aren't transmitted properly
• cardiac arrest – when a problem with the heart's electrical signals cause the heart to stop beating altogether
  
  How is a pacemaker fitted?
  
  
• Having a pacemaker implanted is a relatively straightforward process. It's usually carried out under local anaesthetic, which means you'll be awake during the procedure.
• The generator is usually placed under the skin near the collarbone on the left side of the chest. The generator is attached to a wire that's guided through a blood vessel to the heart.
• The procedure usually takes about an hour, and most people are well enough to leave hospital the day after surgery.
  
  After pacemaker surgery
  
  

  You should be able to return to normal physical activities soon after surgery. As a precaution, it's usually recommended that strenuous activities are avoided for around four to six weeks after having a pacemaker fitted. After this, you should be able to do most activities and sports.

  You'll be able to feel the pacemaker, but you'll soon get used to it. It may seem a bit heavy at first, and may feel uncomfortable when you lie in certain positions.

  You'll need to attend regular check-ups to make sure your pacemaker is working properly. Most pacemakers store information about your natural heart rhythms.

  When you have follow-up appointments, your doctor can retrieve this information and use it to check how well your heart and the pacemaker are working.

  Most ordinary household electrical equipment is safe to use and won't interfere with your pacemaker. This includes microwaves, as long as they're in good working order.

  
  

A hole in the wall between the two upper collecting chambers (ASD) or between the two bottom pumping chambers (VSD) can cause problems. The severity of the symptoms depends on the size and the location of the defect and can range from no symptoms at all to severe heart failure. Heart failure in a baby results in poor feedings and poor weight gain. In older children, heart failure may cause decreased exercise tolerance and shortness of breath.

Depending on their size and location, septal defects may close by themselves. The cardiologist will likely wait a while before recommending surgical treatment to see if that happens naturally. In cases involving larger holes and severe symptoms, however, treatment with surgery or catheter closure with a device will be needed.

The surgical treatment for ASDs and VSDs is open-heart surgery. The heart is stopped and opened, and the hole is closed with a patch made of a synthetic material like Dacron or a patch of pericardium (the thick sac that surrounds the heart). Complications are minimal and the length of stay in the hospital is about three days.

Complications are the ones associated with any open-heart surgery. For VSDs, there is also a small risk of heart block by damage to the heart's conduction system (1% risk). This could require a pacemaker insertion.

Many ASDs can be closed without surgery. This is done by inserting an occluder device in the catheterization laboratory. This procedure does not require a surgical incision or leave a scar. It is often a day procedure, although sometimes your child stays overnight in hospital. Use of this device depends on the size or your child and the size and location of the hole.

An ICD is a battery-powered device placed under the skin that keeps track of your heart rate. Thin wires connect the ICD to your heart. If an abnormal heart rhythm is detected the device will deliver an electric shock to restore a normal heartbeat if your heart is beating chaotically and much too fast.

ICDs have been very useful in preventing sudden death in patients with known, sustained ventricular tachycardia or fibrillation. Studies have shown that they may have a role in preventing cardiac arrest in high-risk patients who haven't had, but are at risk for, life-threatening ventricular arrhythmias.

Why do I need an ICD?

Your doctor may recommend an ICD if you or your child is at risk of a life-threatening ventricular arrhythmia because of having:

• Had a ventricular arrhythmia
• Had a heart attack
• Survived a sudden cardiac arrest
• Long QT syndrome
• Brugada syndrome
• A congenital heart disease or other underlying conditions for sudden cardiac arrest

It knows when the heartbeat is not normal and tries to return the heartbeat to normal.

• If your ICD has a pacemaker feature when your heartbeat is too slow, it works as a pacemaker and sends tiny electric signals to your heart.
• When your heartbeat is too fast or chaotic, it gives defibrillation shocks to stop the abnormal rhythm.
• It works 24 hours a day.
  
  New devices also provide “overdrive” pacing to electrically convert a sustained ventricular tachycardia (fast heart rhythm) and "backup" pacing if bradycardia (slow heart rhythm) occurs. They also offer a host of other sophisticated functions such as storage of detected arrhythmic events and the ability to perform electrophysiologic testing. Stored information can help your doctor optimize the ICD for your needs.

If you suffer from angina, check in with your doctor as soon as possible to schedule a coronary angiography. This test involves injecting your arteries with x-ray dye and watching the path of the colored substance as it makes its way through your blood vessels. The narrowed and blocked pathways are discovered, and you and your doctor know how severe your problem is and what kind of treatment is best.

If your arteries are partially or fully blocked, you have a couple of options. The first is called angioplasty and it's preferred by about one-third of all CAD patients. Angioplasty is a nonsurgical procedure where a tiny deflated balloon is inserted into the problem spot of the artery on the end of a catheter tube. When it reaches the scene of the crime, the balloon is gently inflated for a few minutes, then deflated and removed. This compresses the plaque and opens the passageway for better blood flow. Sometimes, a tiny metallic cage called a stent is put in place to keep the artery open.

The other option is a surgical procedure called coronary artery bypass grafting (CABG). A vein from the leg or chest is sewn to the artery, before and after the blockage, serving as a side street for the blood to flow around the plaque. For years, a patient needed to have his or her chest opened and heart stopped to perform the surgery. Although that method is still used, other minimally invasive techniques have been perfected using robotic arms to perform the procedure. The robot is operated by the surgeon, and the arms are inserted into the chest area through small holes, allowing the heart to continue beating.

Angioplasty or Coronary Bypass Procedures: Which is right for you?

If you opt for an angioplasty procedure, you'll undergo a nonsurgical procedure that will have you up and on your feet sooner. An angioplasty only takes a couple of hours to perform and you'll remain under local anesthesia for the duration, which is appealing to many patients. You'll probably just need to stay in the hospital one night for observation, and then you're back home and in your normal routine within the week.

Coronary bypass surgery usually requires about week in the hospital and up to three months to fully recover. Minimally invasive micro-surgery procedures cut your recovery time down to a few weeks, with only three to four days in the hospital. You could be a candidate for this kind of operation if:

• you have blockage in only one or two coronary arteries
• your blocked arteries are on the front side of the heart
• you're healthy aside from your artery blockage
  
  

There are also some restrictions for angioplasties. You probably aren't a good candidate if:

• your blocked artery is too small for the balloon
• your artery is completely blocked
• your blockage occurs in the left main coronary artery
• you have diabetes or have already suffered heart failure
• your blockage is where two arteries meet

This study was designed to explore the immediate and medium-term results of balloon mitral valvuloplasty in patients with severe but pliable mitral stenosis. Balloon mitral valvuloplasty was performed with either the Trefoil/Bifoil balloon technique or the Inoue balloon technique. The overall success rate of the procedure in 150 consecutive patients was found to be 97%. There were 4 procedure related failures but there was no procedure related mortality. Cardiac tamponade occurred in 2% of patients and left ventricular perforation in 1.3%. Following valvuloplasty there was a significant improvement in mitral valve area and cardiac output and significant fall in mitral diastolic gradient and left atrial pressure. Overall there was a beneficial effect on pulmonary hypertension but this was variable depending on the development of significant mitral regurgitation and or atrial septal defects >1.3:1. Six pregnant patients successfully underwent the procedure with no complications. No difference in immediate haemodynamic outcome was found between the Trefoil/Bifoil and Inoue balloon catheter techniques. However, the cost of the Inoue balloon technique was almost twice that of the Trefoil/Bifoil technique.

Mild mitral regurgitation was found to be common after the procedure with 45% of patients developing an increase in mitral regurgitation by one grade. Significant mitral regurgitation occurred in only 3.7% of patients. No clinical or morphologic factors were found to be predictive of significant mitral regurgitation.

Atrial septal defects with shunt ratios varying from 1.05:1 to 1.6:1 were found in 30% of patients. By and large they were of no clinical significance. Almost 90% were found to be closed in a subgroup of patients restudied at 15 month follow-up. Atrial septal defects with shunt ratios > 1.3:1 were more likely to be associated with an increase in pulmonary artery hypertension after valvuloplasty. Moreover, it was found that atrial septal defects affected the Gorlin mitral valve area calculation, causing a discrepancy in the mitral valve area calculated by the Gorlin formula and that by Doppler pressure half-time. Closure of the atrial septal defect by a balloon catheter resulted in closer agreement between the two methods.

Left ventricular ejection fraction was found to be depressed in 45% of patients. Following balloon valvuloplasty the ejection fraction improved by 21%. However, the improvement in ejection fraction could not be related to an increased preload.

A 3% incidence of restenosis was found in 64 patients followed-up for a mean period of 24 or 15 months. A smaller balloon dilating area was found to be the only predictor of restenosis. The majority (90%) of patients maintained their improved functional status at follow-up.