Everybody has natural rhythm. Call it your inner drummer—the heartbeat keeps time for the rest of the body. But what happens if your beat's too fast or slow? In medical terms, that's called cardiac arrhythmia. Sometimes it's just a minor variation, but some arrhythmias can stop the music altogether.

Arrhythmias, sometimes called "palpitations," are irregularities to the rhythmic beating of the heart. According to The American Heart Association (AHA), "Almost everyone has felt their heart beat very fast, felt a 'fluttering' in their chest or thought their heart was skipping a beat." Arrhythmias are common and don't always signal a problem. Certain types, however, can be dangerous.

I was 20 when I noticed the weird sensation in my chest; like my heart stopped for a second, followed by an extra-strong thump-flop beat. I wasn't dizzy, scared or weak—just startled. Occasionally, my heart sped up for no apparent reason. When I realized it was happening more frequently, I talked to my doctor. After a thorough workup, he said I had a benign (as in "no big deal") arrhythmia, but he also advised me to decrease caffeine and increase regular exercise.

Plumbing and wiring: how the heart works

The heart is a muscular, fist-sized organ that pumps gallons of blood continuously through the body. Think of it like a house with four rooms, or chambers. The right and left atria are on the top floor and the right and left ventricles are on the bottom. Four valves act as one-way doors, letting blood into each chamber and keeping it moving in the right direction. There's only one correct traffic-pattern for blood to flow in this organized system of muscular contractions: right atrium to right ventricle to left ventricle to left atrium and then out to the rest of the body. It's all orchestrated by the heart's electrical system.

A heartbeat starts when an electrical impulse from a nerve bundle called the sinoatrial node sets the pace. That impulse then moves in a specific sequence that tells the chambers to pump and valves to open and close. If the exact circuit is followed, the heart pumps about 60 to 100 times per minute. Normal heart rate variations occur during exercise, sleep, heat and stress. When the circuit is interrupted, however, the result is arrhythmia.

Circuit breakers: types of arrhythmias

Arrhythmias that alter the heart rate significantly usually cause one of four cardiac changes:

1. Bradycardia: The heart beats too slowly, potentially causing insufficient circulation to the brain and body. Symptoms include:

  • Fatigue
  • Dizziness
  • Lightheadedness
  • Fainting or near-fainting
  • In extreme cases, cardiac arrest

2. Tachycardia: The heart beats too fast at a regular or irregular pace. Symptoms include:

  • Palpitations
  • Heart pounding or racing
  • Dizziness
  • Lightheadedness
  • Fainting or near-fainting

3. Premature contraction: This is an early beat that feels like you're skipping a beat followed by an extra strong beat. Usually benign, premature contractions can start in an atrium or ventricle and are common in people with healthy hearts.

4. Fibrillation: The heart doesn't have coordinated pumping action and "quivers" instead of beats. There are two kinds of fibrillation:

  • Atrial fibrillation (AF): Approximately 2.2 million Americans live with AF, the most common "serious" heart rhythm. AF is most common in smokers and in people over 65 or with hypertension or heart disease. AF can be medically managed, but increases risks for heart attack and stroke if not controlled. Symptoms include:
    • Racing, uncomfortable, irregular heartbeat
    • Flopping, fluttering or thumping feeling in your chest
    • Heart palpitations
    • Dizziness
    • Sweating
    • Chest pain or pressure
    • Difficulty catching your breath
    • Overall weakness
    • Fainting
    • Fatigue during exercise
  • Ventricular fibrillation (v-fib): Ventricular fibrillation is a medical emergency. The lower chambers quiver, the heart can't pump and the strain causes sudden cardiac arrest. V-fib can sometimes be stopped with an automated external defibrillator (AED). If you see someone experiencing signs of cardiac arrest:
    • Call 9-1-1
    • Get an AED (if available) and follow its instructions.
    • Begin CPR

Jeanne Poole, M.D., cardiologist and electrophysiologist at the University of Washington Medical Center in Seattle, Wash., says it's important to keep tabs on irregular heartbeats. "It's good to have any new, noticeable heartbeat irregularities evaluated. Occasional skipped beats with no other symptoms probably don't require immediate care. But, get emergency care for anyone who passes out or almost passes out, feels fluttering or a racing heartbeat, especially if there's a history of heart disease. Chest discomfort, tightness, pain or breathing difficulty are all bad signs."

According to Dr. Poole, "Arrhythmias aren't just for old people. Athletes and young people with family history of sudden cardiac arrest, whose heart races during exercise, has difficulty breathing or passes out needs emergency care."

My irregular heartbeat (premature ventricular contractions) comes and goes, especially when I'm tired, stressed, not getting enough exercise or drinking too much coffee. It's a good reminder about the rules for "healthy living." I've always walked to the beat of a different drummer, but apparently I'm not unique—arrhythmias are a fact of life for millions. And it's good to know what your beat is about.