Got Rhythm? An Update on the Treatment of Cardiac Arrhythmia

Posted By SHL Librarian

Presented by Paul J. Wang, MD
Professor of Medicine and Bioengineering (by courtesy)
March 23, 2017

Having a good sense of rhythm helps to play music or to dance. But rhythm is even more essential to our lives. It rules our heartbeat.

If that heart rhythm gets out of whack, it can be uncomfortable, Dr. Paul Wang told the audience recently at the Stanford Health Library. Some people may feel only mild passing symptoms, like their heart is racing.

Others may feel short of breath, dizzy, or have chest pain daily. Mild or not, seeing a doctor is important, Dr. Wang said. Routine tests can show whether a person has an abnormal heart rhythm—called an arrhythmia—and whether it needs to be fixed.

“Do all of these rhythms need treatment? Indeed, not all do,” said Dr. Wang, a professor of medicine and director of the cardiac arrhythmia service at Stanford. For those that do need treatment, the options range from prescription medicines to medical procedures that correct the irregular rhythm.

Anyone uncomfortable from symptoms of a racing or irregular heartbeat should see a physician, Dr. Wang said. The first step is often to get an ECG—an electrocardiogram. “To record the rhythm is very important,” Dr. Wang said. “We need to be able to get a clear picture of what it looks like.”

ECGs measure the heart’s electrical signals that pass from the upper portions of the heart to the bottom. Those signals cause the heart muscle to contract repeatedly in a regular rhythm or heartbeat. That enables the heart to pump blood to the body.

The upper heart chambers—called the atria—are where the electrical signals start. The signals travel to the lower heart chambers—called the ventricles. These lower chambers produce the heart’s main pumping action.  A person’s pulse—the heart rate—is a measure of the pumping rate in the ventricles, Dr. Wang said.

An ECG can examine the electrical activity in these chambers to see if the abnormal heart rhythm is caused by a rapid heart rate, called tachycardia.

“For some rhythms, they’re not by nature life-threatening,” Dr. Wang said. “It turns out many of these rhythms are self-terminating—meaning that they stop on their own.” One arrhythmia called supraventricular tachycardia—a racing heartbeat that starts from signals above the ventricles–often doesn’t pose much risk and only sometimes needs treatment.

“Sometimes they continue on and require medical attention to stop the rhythm,” Dr. Wang said.

Sometimes a racing heart beat can be stopped by a method called “bearing down.” Also called the Valsalva maneuver, this is a technique that patients can learn to do themselves.  The patient holds their breath and bears down as though they are straining to have a bowel movement. Then they relax and exhale. This can restore the normal heart rhythm without having to take drugs.

Some people need drugs, however. Digoxin, beta-blockers (metoprolol, atenolol, propranolol) or calcium-channel blockers (diltiazem, verapamil) are often prescribed. “These medicines make up the vast majority of treatments of supraventricular tachycardia,” Dr. Wang said.

Some arrhythmias are caused by a different electrical pattern in the heart. In some fast heart rhythms in the upper heart, the electrical signals move in small circles “like a car going around on a racetrack,” Dr. Wang said. But in some people, he said, the electrical signals instead move in a more disorderly manner, “like a sandstorm or a windstorm, blowing very rapidly. It doesn’t have the same organization as that car on a racetrack.”

That can lead to a quivering or irregular heartbeat called atrial fibrillation. That’s a common arrhythmia that affects more than 2.2 million U.S. people. Atrial fibrillation increases the risk for blood clots and stroke.

Symptoms include heart palpitations that “feel like a jumping inside the chest,” Dr. Wang said. It can also feel like a racing heart or cause chest pain, difficult breathing, dizziness or fatigue.

Common triggers of atrial fibrillation might be “quite surprising,” Dr. Wang said. They include exhaustion, dehydration, stimulants like caffeine or alcohol, sleep problems, emotional or physical stress, or even a medical procedure like a colonoscopy. Atrial fibrillation can also be caused by an overactive thyroid, intense exercise or a change in elevation.

Aging also increases the risk for atrial fibrillation. Most people develop it at age 60 to 85, Dr. Wang said.

Some atrial fibrillation may not requirement treatment to stop it. When it’s called “paroxysmal,” atrial fibrillation often comes and goes on its own.

When atrial fibrillation is persistent, however, it may require drugs or an electrical shock to the heart to reset the rhythm.

The initial treatment of atrial fibrillation usually targets an area of the heart that sits between the upper and lower chambers, called the “A-V node” for atrioventricular node. “The A-V node acts as a staircase that connects the top floor of the building—or the heart—and the bottom floor, the ventricles,” Dr. Wang said.

This node conducts electrical signals. “It serves as a conduit or a controlling device to control the rhythms that go from the top to the bottom,” Dr. Wang said.

Atrial fibrillation can be treated by some of the same drugs used for tachycardia. Doctors often see a remarkable improvement by simply “making sure the heart rate is not nearly as fast as it was previously,” Dr. Wang said.

But if the usual drugs don’t work, there are other anti-arrhythmic drugs that may help. Still another drug, warfarin, can lower risk by three-quarters or more.

Deciding whether to get treatment to reduce the risk of stroke in atrial fibrillation has become easier with new guidelines based on a scoring system. The score counts an individual’s risk factors including age, blood pressure, diabetes, and other heart conditions. “The more points, the higher risk of having a stroke from atrial fibrillation,” Dr. Wang said. “We can assess that risk and therefore advise people.”

When drugs don’t help, patients have another option: a procedure called catheter ablation. A catheter is a small plastic tube inserted into the body that goes through a vein to the heart. Ablation delivers heat, cold or radio waves to kill or scar the cells in a target area. That can restore a regular rhythm.

The first FDA studies of catheter ablation found it can stop atrial fibrillation from recurring in 60 percent of people (getting radio ablation) or even 69 percent of those getting cryocatheter (cooling) ablation. It’s gotten better since then.

“Gradually the techniques have been better, the tools are better, and the success has gone up,” Dr. Wang said.

Catheter ablation does have risks. About 2-3 percent of those getting the procedure have a serious complication, Dr. Wang said.

Doctors are continuing to develop newer techniques that may prove more successful and safer. One of them is a hybrid procedure that combines catheter ablation with surgery that treats the heart rhythm problem by treating the outside surface of the heart.

This hybrid procedure is being used for people with long-standing, persistent atrial fibrillation, Dr. Wang said. Stanford doctors plan to be part of a national study testing this procedure, which will be submitted to the FDA for approval.

Dr. Wang also called attention to another arrhythmia, ventricular fibrillation, that can cause sudden cardiac arrest. That’s when the heart stops beating suddenly. Survival from sudden cardiac arrest is only about 10 percent. He called it “one of the most important causes of death in our society.”

The chance for survival declines about 10 percent for every minute after the cardiac arrest, Dr. Wang said. “Time is of the essence.”

Emergency treatment can be given by nonmedical bystanders using the devices called AEDs for automatic external defibrillators. AEDs deliver a shock the heart to make it restart. They are commonly available at airports, fitness clubs, casinos, sports arenas and many other public places.

AEDs come in a kit that contains visual and voice commands to tell people how to use them step by step. AEDs are so easy to use that one study found 13-year-olds without any training used it “perfectly,” Dr. Wang said.

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Stanford Cardiac Arrhythmia Service