Blocked Pathways

A properly functioning heart has clear pathways along which uninterrupted electrical impulses travel from the sinus node to the ventricles. If there is a disruption along the pathways or a problem with the tissues that create the impulses, the heart may not beat correctly, which can cause an arrhythmia.

Conditions or situations that may block the pathways, interrupt electrical impulses, or otherwise cause a heart not to function properly include:

  • alcohol use or abuse
  • energy drinks loaded with caffeine
  • drug use or abuse, including use of some over-the-counter medicines
  • cocaine
  • methamphetamines
  • too much caffeine or nicotine intake
  • smoking
  • diabetes
  • heart disease
  • heart failure
  • high blood pressure (hypertension)
  • an overactive or underactive thyroid gland
  • rheumatic heart disease
  • mental or emotional stress, including anger or anxiety
  • muscular scarring of the heart, possibly from a heart attack
  • some herbal treatments or dietary supplements

Altered Heart Structure

An arrhythmia can also develop if the heart’s physiology has been altered. Conditions that may change the heart’s structure include the following.

Reduced Blood Supply

If the heart does not receive an adequate supply of blood, its cells and tissues may be starved for oxygen and unable to properly conduct the electrical impulses needed to make it beat.

Damaged or Destroyed Heart Tissue

If a heart’s tissues have been damaged or destroyed—either by a heart attack or from a heart disease such as coronary artery disease, cardiomyopathy, or a valvular heart disease—the electrical impulses may not be able to travel properly. The conditions may also affect the heart’s ventricles and valves, which can make the movement of blood to and from the heart more difficult. This may further complicate an existing arrhythmia.

Congenital Causes

In some cases, such as Wolff-Parkinson-White syndrome or Brugada syndrome, the cause of an arrhythmia is a congenital heart defect or a genetic defect—meaning it is present from birth. In other cases, a cause may not be found.