Blessed are the pacemakers and other heart devices

As the population has aged and people have begun living longer after being diagnosed with heart disease, the use of heart devices has grown. Recent advances in technology have expanded the number and sophistication of these devices. Here’s more about how pacemakers, implantable cardioverter-defibrillators (ICDs), and other devices are helping to treat some forms of heart disease and ensure the steady, rhythmic beat of life. 

Pacemakers: Regulating the heartbeat

A pacemaker helps your heart beat in a regular rhythm when your body’s natural pacemaker, the sinoatrial (SA) or sinus node, falters (see figure). This small mass of specialized cells in the upper right heart chamber (right atrium) produces the electrical signals that cause your heart to beat. The sinus node acts like a spark plug, generating a steady stream of electrical impulses that travel along a precise pathway of specialized muscle fibers from the top of the heart to the bottom.

As the electrical signal moves from the two upper chambers (atria) to the two lower chambers (ventricles), they contract and pump blood. For your heart to work properly, the upper and lower chambers must work in a coordinated way, and the heart must beat at an appropriate rate  about 60 to 100 beats a minute for most healthy, resting adults.

Reasons for getting a pacemaker

The most common reason for having a pacemaker implanted is a heart rate that’s slower than normal, a condition called bradycardia. Bradycardia, a heart rate less than 50 beats a minute, can result from:

• Sinus node disease. Damage to your SA node  from aging, a heart attack or heart disease, certain medications, infections or other diseases  can disrupt the node’s ability to set the correct pace for your heartbeat. As a result, your heart rate may slow down and become irregular, causing signs and symptoms such as fainting, dizziness or lightheadedness and fatigue.

• Heart block. If the electrical impulses are slowed down or blocked as they move through the heart, the heart may beat too slowly or in an irregular rhythm. Possible causes of heart block include aging, damage from a heart attack, and certain medications, infections, and nerve and muscle disorders.

Your doctor might also recommend a pacemaker if:

• Your heart rate alternates between too slow and too fast, a condition called sick sinus syndrome.

• You’ve had problems treating atrial fibrillation  a rapid, irregular heartbeat that starts in the heart’s upper chambers.

• You have certain genetic conditions that cause heart rhythm problems.

How it works

The main unit of a pacemaker, called a generator, consists of a battery, electronic circuitry and a small computer (microprocessor) in a small metal case (see figure on Page D-1). This unit is surgically implanted under your skin, usually near your collarbone. This device is connected to your heart by one or two thin wires, called pacing leads, which end at an electrode placed next to the heart wall.

The pacemaker continually monitors your heart’s natural rhythm. If your heart slows below a certain level (or becomes too fast or irregular), the pacemaker fires electrical impulses to the heart. The stimulation helps your heart beat at a proper rate or “pace.” You don’t feel the electrical signals generated by a pacemaker.

Many pacemakers include sensors that monitor your activity level and adjust your heart rate in response to exercise.

ICDs: Preventing life-threatening rhythm problems

You’ve probably seen medical shows where an emergency room staff uses chest paddles or a computerized device to “shock someone back to life.” That shock is known as defibrillation, and it’s the only way to stop certain life-threatening heart rhythm problems and restore normal beating.

An implantable cardioverter-defibrillator, or ICD, provides internal defibrillation if needed. Similar to a pacemaker, an ICD is surgically implanted under the skin and has wires with electrodes on the ends that connect to the right ventricle and possibly the right atrium. The device can detect dangerous heart rhythms originating in the ventricles  a too-fast, recurrent heartbeat (ventricular tachycardia) or a rapid chaotic heartbeat (ventricular fibrillation). In ventricular fibrillation, the heart quivers (fibrillates) instead of contracts, so it can’t effectively pump blood. Without an electric shock to restore normal rhythm, death can occur within minutes. This condition is called cardiac arrest or sudden cardiac death.

An ICD may be recommended if you face a high risk of ventricular arrhythmias because you:

• Survived a previous cardiac arrest.

• Have a history of severe heart damage from a heart attack or severe heart failure.

• Have an inherited disorder that may increase the risk.

ICDs can prevent sudden death in people who have recurrent tachycardia or ventricular fibrillation. If an ICD detects ventricular fibrillation, it delivers a lifesaving shock  which feels like a sudden kick in the chest. Most ICDs can also function as pacemakers to slow down a fast heart rate or speed up a slow heart rate.

Pacemakers and ICDs over the long term

After you get a pacemaker or an ICD, your doctor will check the device every three or six months. Modern heart devices can capture and store a wealth of information that helps your doctor manage your treatment and adjust it as needed. You may have your device checked at your doctor’s office or even remotely through a telephone call or a wireless connection to the Internet.

Your doctor will keep track of your device’s battery status. Most pacemaker and ICD batteries last an average of five to seven years. When the battery starts to run down, you’ll need minor surgery to replace the generator and battery. This will happen before you notice any changes in how your pacemaker works.

Cardiac resyncrhonization therapy

Also known as biventricular pacing, cardiac resynchronization therapy (CRT) is a treatment option for people whose cardiac electrical systems have been damaged due to congestive heart failure. This type of pacemaker sends electrical pulses between the atrium and both ventricles. The pacing helps coordinate or synchronize the ventricles’ contractions so they can pump blood more effectively. Some CRT devices also incorporate an ICD  these are called CRT-Ds.

LVAD: An artificial heart

Also known as artificial heart, the left ventricular assist device (LVAD) is a battery-operated, mechanical pump-type device that helps maintain the pumping ability of a heart that can’t work effectively by itself. Traditionally used as a “bridge” to a heart transplant, LVADs are becoming an alternative to transplantation for some people who have advanced heart failure.

Unlike other implanted heart devices, getting an LVAD inserted requires open-heart surgery, and people with this device face more limitations in their lifestyle. But for people who are very ill, LVADs can be lifesaving.

A normal rhythm of life

People who have heart rhythm devices can generally lead active lifestyles that include exercise and most sports. If you need a heart device, your health care team will let you know what precautions or activity restrictions you’ll need to follow. You should be able to use a cell phone, microwave oven, and other household appliances. You can also walk through an airport security gate, although you should tell the security personnel that you have an implanted heart device. While pacemakers and other devices can’t cure heart disease, they can help you live a longer, fuller life.