When your heart loses its rhythm

Most people experience occasional, brief, usually harmless heartbeat problems, such as the feeling of a skipped, fluttering or racing heartbeat. However, to thousands of mainly older Filipinos, such heart rhythm problems (called arrhythmias) may cause bothersome – or sometimes dangerous – signs or symptoms. These may include shortness of breath, fainting or even sudden cardiac death – an unexpected loss of heart function, breathing, and consciousness that can lead to death within minutes without emergency medical intervention.

Recent advances in medical technology have added new treatment methods to the array of procedures that doctors may use to try to control or eliminate arrhythmias. In addition, since troublesome arrhythmias are often made worse – or caused – by a heart weakened or damaged by coronary artery disease (CAD), you may be able to reduce your arrhythmia risk by adopting a heart-healthy lifestyle.

The Heart Of The Matter

Your heart has four compartments. The upper two are the atria; the larger two below are the ventricles. The atria are the anterooms of the cardiac pump house, each capable of holding just a few ounces of blood at a time. The right atrium receives oxygen-depleted blood on its trip back to the heart from the rest of the body. The left one receives blood returning from the lungs after it has been freshly oxygenated and sends it to the powerful left ventricle. The left ventricle pumps blood out through the aorta to supply the whole body.

Normally, the atria and ventricles contract in a coordinated fashion at a nice steady clip of 60-80 times per minute. This rate is set by the sinoatrial (SA) node, a group of cells in the right atrium that serves as the heart’s natural pacemaker. The SA node generates a pulse of electrical activity that spreads across the muscular cells in the atria, causing them to contract. The electrical charge also travels to another cluster of cells in the middle of the heart called atrioventricular (AV) node that acts like a gatekeeper, causing a brief delay of about a tenth of a second. As a result, your heartbeat marches in a two-beat rhythm: First, the atria contract; then, the ventricles – over and over again.

What Goes Wrong?

Heart arrhythmias may occur when any phase in the heart’s electrical system malfunctions. Arrhythmias are classified by where they originate (atria or ventricles) and by the speed of heart rate they cause. Tachycardia refers to a resting heart rate over 100 beats a minute and bradycardia refers to a resting heart rate under 60 beats a minute. There are many types, but two are especially worth mentioning.

Atrial fibrillation, the fast and chaotic beating of the atrial chambers, is the most common arrhythmia. Your risk of developing atrial fibrillation increases past age 65 mainly due to the wear and tear that may affect your heart’s function as you age. Atrial fibrillation can be intermittent, lasting a few minutes to an hour or more before returning to a regular heart rhythm. It can also be chronic, causing an ongoing problem. Atrial fibrillation is seldom a life-threatening arrhythmia, but it can be the cause of more serious conditions such as a stroke.

On the other hand, about 90 percent of sudden cardiac deaths are caused by ventricular fibrillation. In this form of arrhythmia, rapid, chaotic electrical impulses cause your ventricles to quiver uselessly instead of pumping blood. Without an effective heartbeat, your blood pressure plummets, instantly cutting off blood supply to your vital organs – including your brain. Most people lose consciousness within seconds and require immediate medical assistance such as cardiopulmonary resuscitation (CPR). Your chances of survival may be prolonged if CPR is delivered promptly, with your heart shocked back into a normal rhythm with a device called a defibrillator. Without CPR or defibrillation, death results in minutes.

Most cases of ventricular fibrillation are linked to some form of heart disease. Ventricular fibrillation is frequently triggered by a heart attack. However, ventricular fibrillation may also be your first indication of heart problems.

How Can You Detect It?

To diagnose a heart arrhythmia, your doctor may ask about – or test for – conditions that may be triggering your arrhythmia, such as heart disease or a problem with your thyroid gland. Your doctor may also perform heart monitoring tests specific to arrhythmias. These tests either passively monitor your heart or try to actively induce an arrhythmia while closely monitoring your heart.

These tests include:

• Electrocardiogram (ECG). During an ECG, sensors (electrodes) that can detect the electrical activity of your heart are attached to your chest and limbs. An ECG measures the timing and duration of each electrical phase in your heartbeat.

• Holter monitor. This portable ECG device can be worn for a day or more to record your heart’s activity as you go about your routine.

• Echocardiogram. A hand-held device (transducer) placed on your chest uses sound waves to produce images of your heart’s size, structure, and motion.

• Stress test. Some arrhythmias are triggered or worsened by exercise. During a stress test, you may be asked to exercise on a treadmill or a stationary bicycle while your heart activity is monitored by an ECG. A drug may be used to stimulate your heart in a way that’s similar to exercise and can also be used to detect coronary artery disease.

If you’ve received a diagnosis of arrhythmia, treatment may or may not be necessary. Usually, it’s only required if the arrhythmia is causing significant symptoms or if it’s putting you at risk for a more serious arrhythmia or its complications.

If your symptom-producing bradycardias don’t have a cause that can be corrected – such as hypothyroidism or a drug side effect – they’re often treated with a pacemaker. A pacemaker is a small, battery-powered device that’s usually implanted near the collarbone. One or more electrode-tipped wires run from the pacemaker through your blood vessels to your inner heart. If your heart rate is too slow or if it stops, the pacemaker sends out electrical impulses that stimulate your heart to beat at a steady, proper rate. The newest pacemakers can monitor and pace your atria or ventricles – or both – in proper sequence to maximize the output of blood from your heart. In addition, your doctor can program your pacemaker to meet your pacing needs.

For tachycardias originating in the atria or ventricles, treatments may include one or more of the following:

• Medications. Many different antiarrhythmic drugs are used for emergency or long-term treatment of arrhythmias. Most of these medications work to slow your heart rate by either suppressing the activity of the pacemaking tissue or slowing the transmission of fast impulses inside the heart.

• Cardioversion. In some arrhythmias, drugs or an electric shock may be used to reset your heart to its regular rhythm. Cardioversion with drugs uses certain antiarrhythmics and is usually done in a hospital so that your heart can be monitored. If successful, the same or similar drugs may be used to help maintain rhythm.

In electrical cardioversion, a shock is delivered to your heart through paddles or patches on your chest. Done under light anesthesia, the shock stops your heart for a split second. When it beats again, it often resumes normal rhythm.

• Radiofrequency catheter ablation. In this procedure, one or more catheters are threaded through your blood vessels to your inner heart. They’re positioned along electrical pathways identified by your doctor as causing your arrhythmia. Electrodes at the catheter-tips are heated with radiofrequency energy. This destroys (ablates) a small spot of heart tissue and creates an electric block along the pathway that’s causing your arrhythmia. Usually, this stops your arrhythmia.

• Other procedures include the use of an implantable cardioverter defibrillator (if you’re at high risk of developing a dangerous ventricular tachycardia or ventricular fibrillation), and the maze procedure, which involves making a maze of incisions in the atria to interfere with excess electrical pathways and impulses.

Keeping Your Heart Healthy

It’s true that certain arrhythmias may lead to serious conditions, including sudden cardiac death. But even the most serious arrhythmias can often be managed or eliminated using modern technologies and treatment techniques, and by making lifestyle changes.