Changing Heartbeat And Palpitations

Palpitations may occur with changes in the:

• Heart rate, which is the speed at which the heart beats

• Heart rhythm, which is the pattern of the heart beats

• Force of ventricular contraction, which reflects how vigorously the heart is pumping

Arrhythmia is the term used to describe irregularities or abnormal patterns of the heart's pumping cycle.

Arrhythmias (irregular heartbeats):

• May be present for just a few beats at a time - this creates palpitations experienced as an extra or skipped heartbeat

• May last for longer periods in the form of a fast heart rate (tachycardia)

• May involve slow heart rate (bradycardia).

Palpitations Associated With Extra Heartbeats

Premature heartbeats (contractions) are beats that occur earlier than expected, briefly interrupting the normal heart rhythm. They are the most common abnormality of the heart rhythm and are often experienced as a "thump" in the chest or a missed beat.

This sensation does not reflect the premature beats themselves, but rather the forceful beat that follows the pause after the premature beat. The heart has more time to fill with blood during this pause, making the next beat more forceful.

Extra heartbeats occur frequently in healthy individuals as well as in those with underlying heart disease. Many people report extra beats when they are exhausted or after having too much alcohol or caffeine. In most cases, premature contractions are not serious and do not require treatment. However, if PVCs are frequent or occur in certain patterns, they may be a sign of a more serious problem.

Palpitations Associated With A Fast Heart Rate

A fast heart rate of greater than 100 beats per minute is known as tachycardia (from the Greek adjective for swift).

Tachycardias can be an appropriate response to exercise or other causes (such as fever, blood loss, or low blood pressure). Other tachycardias may reflect underlying heart disease, problems with the electrical system of the heart, or a response to a certain disease state.

Fast heartbeats that originate above the ventricles - in the atria, AV node, or both - are referred to as supraventricular tachycardias (SVT).

Types of SVTs are:

• Sinus tachycardia (fast heartbeat but with normal rhythm)

• Atrial tachycardia (fast heartbeat originating in the upper chamber of the heart)

• Atrial fibrillation

• Atrial flutter

• Some types of fast heart rates that involve the AV node

These relatively common rhythms are not usually serious - but they can cause considerable discomfort. Individuals often describe a feeling of a racing or pounding heart. Others experience light-headedness, shortness of breath, or weakness.

The rhythm usually starts and stops suddenly, however, and it only requires treatment if symptoms occur often, last a long time, or are very bothersome.

Two supraventricular tachyarrhythmias that frequently occur at the same time and that sometimes require treatment are:

• Atrial fibrillation

• Atrial flutter

Individuals with atrial fibrillation have an irregular heartbeat that is typically too fast. Impulses are generated from multiple places in the atria instead of just from the sinus node. This chaotic signaling causes the atria to quiver (fibrillate) rather than contract normally.

In contrast, individuals with atrial flutter have a regular, but very fast, heart rate of between 250 and 350 beats per minute.

Conditions often associated with these two types of arrhythmia include:

• Coronary artery disease

• Hypertension

• Mitral valve prolapse

• Congestive heart failure

• Rheumatic heart disease

• Cardiomyopathy

• Congenital atrial malformations

• Recent heart surgery

• Alcohol and drug use, especially withdrawal

• Chronic obstructive pulmonary disease

• Hyperthyroidism

Fast heartbeats that originate in the ventricles are called ventricular tachyarrhythmias. Individuals with this condition may experience:

• Palpitations

• Shortness of breath

• Light-headedness

Individuals with fast heart rates (faster than 180 beats per minute) and underlying heart disease are more susceptible to loss of consciousness (syncope) due to reduced blood pressure, and even sudden death.

Most individuals with ventricular tachycardias have underlying heart disease (such as coronary artery disease or valve disease). But certain drugs and electrolyte (salts in the blood) disturbances also contribute to ventricular tachyarrhythmias.

Palpitations Associated With A Slow Heart Rate

A slow heart rate of less than 60 beats per minute is known as bradycardia (from the Greek word for slow). The two mechanisms that lead to slow heart rates are:

• Failure of the sinus node to generate impulses (sinus bradycardia)

• Failure of the impulses to be to conducted normally to the ventricles (AV block)

Bradycardia can be found in well-trained athletes as well as other individuals in excellent health. Normally, these individuals do not experience symptoms, and the slow heart rate is no reason for concern. Bradycardia also can be caused by vomiting, an underactive thyroid gland, or certain medications.

In some people, however, a slow heart rate may mean that there is a problem with the heart's electrical system. The problem could be:

• Sick sinus syndrome, in which the number of functional cells in the sinus node is decreased due to disease or advanced age. This is the most common cause of bradyarrhythmias.

• A variant of sick sinus syndrome, known as bradycardia-tachycardia syndrome, which involves alternating bouts of a slow and fast heart rate.

• Heart block (AV block), in which impulses from the atria are delayed (first-degree block), intermittently blocked (second-degree block) or completely blocked (third-degree block) from reaching the ventricles.

The need for treatment is based on the site of the AV block as well as the degree of symptoms. Whereas young people and those in good cardiovascular health may tolerate slow heart rates, older people and those with even mild heart disease may experience symptoms of inadequate blood flow including:

• Dizziness

• Weakness

• Fainting

• Fatigue

• Shortness of breath.

Syncope (loss of consciousness) and death also may occur. A pacemaker may be appropriate for people with symptoms and serious AV blocks. Individuals with pacemakers can live for decades.