"It feels like my heart is doing flip-flops, turning over in my chest,” the middle-aged real estate broker told me.

She was trying to explain to me what the heart palpitations she’d been experiencing for several days felt like. A fast or slow heart rate, extra or skipped heartbeats, or forceful, irregular, or pounding heartbeats are all palpitations. And even if you consider them to be trivial, they should be brought to the attention of your doctor.

When Heart Palpitations Are Benign

Most of those deviations, which are also known as arrhythmias, aren't life-threatening and resolve on their own. The most benign and most common occur when the heart contracts prematurely. This causes a slight delay in the next heartbeat, which is felt as a "flip-flop" or skipped beat. That so-called premature atrial contraction (PAC) usually starts in the heart's upper right chamber, or atrium.

More on Heart Health

Less common but also benign is the premature ventricular contraction (PVC), which originates in one of the heart’s lower chambers. Both conditions can be triggered by alcohol, anxiety, exercise, medications, stress—or nothing that can be pinpointed.

PACs that cluster lead to a rapid heartbeat (180 to 240 beats per minute, compared with the normal 60 to 100). Called supraventricular tachycardia or SVT, it can last minutes to hours, but in the absence of heart disease usually causes no other symptoms.

But if you experience a very fast heartbeat, go to the nearest medical facility; SVT should be diagnosed with an electrocardiogram (an EKG, or a picture of your heart’s electrical activity).

When Heart Palpitations May Be Serious

More significant arrhythmias are usually accompanied by such symptoms as sweating, light-headedness, fainting, or chest or lower jaw pain, and can be due to heart disease. For example, atrial fibrillation (A-fib), in which the heart's upper chambers quiver instead of beat, often causes shortness of breath and sometimes fainting. Blood clots can form in the atria and cause strokes if they travel to the brain, hence the need for strong blood thinners if A-fib is diagnosed.

A rare but much more potentially devastating arrhythmia, called ventricular tachycardia, can arise when PVCs occur one after another. If the problem is detected on a monitor, corrective drugs can be lifesaving. Otherwise, it can be fatal.

Catch Heart Palpitations in the Act

The key to diagnosing palpitations properly is to catch them red-handed on an EKG. That’s unlikely in the brief time you’re hooked up to an EKG machine at a doctor’s office.

Palpitations that occur one to several times daily can often be detected by a Holter monitor, a strap-on device worn for 24 to 48 hours that continuously records your heartbeat.

For less frequent palpitations, a cost-effective way to detect them is to wear a cardio-event recorder, which can transmit graphic recordings of episodes—if and when they occur—over a more prolonged period.

To detect underlying heart disease, an EKG before and immediately after exercise, or a nuclear stress test, in which injected material is used to detect coronary artery obstructions, may be necessary.

A last resort is the invasive electrophysiology study, in which a catheter is threaded from your groin to your heart, and drugs are used to provoke the arrhythmia and pinpoint its origin. Once identified, the source of the abnormal rhythm can be eliminated by high-frequency sound waves. A defibrillator-pacemaker can be implanted if needed.

When trying to find the cause of palpitations, it’s important to consider the setting. In a study of 190 people with them, less than half had heart disease. One-third of the remaining cases were due to psychological causes, such as anxiety. No cause was found in 16 percent. The rest of the cases were triggered by thyroid overactivity, anemia, and drug ingestion, including caffeine.

A Patient's Happy Ending

My patient didn’t need an extensive investigation. The description of her palpitations was on target, and a few PACs showed up on an office electrocardiogram. Treatment consisted of advising her that she would be better off not taking the pseudoephedrine she was using as a decongestant for a cold. She called a few days later to say she was no longer having heart flip-flops. It was reassuring to both of us.