1. Atrial Fibrillation Slideshow Pictures
2. Atrial Fibrillation (A-Fib) Quiz: Test Your Medical IQ
3. Heart Symptoms Never to Ignore Slideshow

Medical Author:

Benjamin Wedro, MD, FACEP, FAAEM

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

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Medical Editor:

Daniel Lee Kulick, MD, FACC, FSCAI

Daniel Lee Kulick, MD, FACC, FSCAI

Dr. Kulick received his undergraduate and medical degrees from the University of Southern California, School of Medicine. He performed his residency in internal medicine at the Harbor-University of California Los Angeles Medical Center and a fellowship in the section of cardiology at the Los Angeles County-University of Southern California Medical Center. He is board certified in Internal Medicine and Cardiology.

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Medical Editor:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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In this Article

• How does the heart work?
• Premature atrial contractions (PACs) and premature ventricular contractions (PVCs)
• Sinus tachycardia
• Sinus bradycardia
• Abnormal heart rhythms
• Tachycardia
• Ventricular fibrillation
• Ventricular flutter
• Paroxysmal supraventricular tachycardia (PSVT)
• Wolf-Parkinson-White Syndrome
• Atrial fibrillation
• Atrial Flutter
• Bradycardia
• Heart blocks
• When should I seek medical care?
• How are heart rhythm disorders diagnosed?
• What is the treatment for heart rhythm disorders?
• Can heart rhythm disorders be prevented?
• Atrial Fibrillation Slideshow Pictures
• Take the Atrial Fibrillation Quiz
• Heart Symptoms Never to Ignore Slideshow
• Patient Comments: Abnormal Heart Rhythms - Treatments
• Patient Comments: Heart Rhythm Disorders - Type of Disorder
• Find a local Cardiologist in your town
• Heart Rhythm Disorders Index

The heart, its cells and its electricity may come under the many outside influences causing it to beat more slowly. Sinus bradycardia (brady=slow + cardia=heart) by definition, is a heart beat generated by the SA node at a rate slower than 60 beats per minute. This may be normal in people who are active and athletic or in patients taking medications designed to slow the heart like beta blockers or calcium channel blockers.

Vasovagal syncope is an episode of profound sinus bradycardia associated with a noxious stimulus that causes the vagal system of the body to kick in and slow the heart rate. While the sympathetic system of the body is mediated by adrenaline, the parasympathetic system is mediated by the vagus nerve and the chemical acetylcholine, which promotes the exact opposite body reaction than adrenaline. In some people, exposure to pain or a difficult emotional situation can stimulate the vagus nerve, slow the heart, and dilate blood vessels (veins), causing cardiac output to decrease and making a person feel lightheaded or faint. The vagus nerve also can be stimulated to slow the heart when one bears down to urinate (micturition syncope) or have a bowel movement.

Rhythm disturbances are classified according to whether they arise from the atrium or ventricle, are fast or slow, or regular or irregular.

Rapid heart rates can originate from either the atrium or the ventricle, but rhythms from the ventricle are more often considered life threatening. The initial approach to rapid heart rates is to quickly identify the rhythm, and if blood pressure is maintained and there is no evidence of a failing heart, then treatment is directed to rate control with the eventual return of the heart back to normal sinus rhythm. If, however, there is evidence that the heart is failing because of the rapid rate, then emergency measures, including using electricity to shock the heart back into a regular rhythm, may be necessary.