Rhythms-recurrences of patterns, actions, sounds, or situations at fairly regular intervals of time or space-are parts of everyday life that we often ignore. We seldom consider the firing of the individual cylinders in the engine of our automobiles that result in its ability to move forward, or the rhythmic rising and setting of the sun each day. When music is played well, we appreciate its beauty and the ease with which it seems to flow. Likewise, unless we are made aware that our hearts beat according to a cyclical scheme, we ignore the pumping and just feel good. But when one of these rhythms is disturbed, we immediately notice that something has changed. Arrhythmia is the term applied to irregularities or abnormal patterns of the heart's pumping cycle. In the sections that follow, we will discuss the heart's normal rhythm and its production as well as specific abnormalities in the rhythm and approaches to treating these abnormalities.
The ECG is the basis for all arrhythmia diagnosis. The ECG tracing is a series of waves that represent the electrical events of the various chambers and conduction pathways within the heart. The small initial wave, called the P wave, represents the electrical activation of the atria. Next comes the QRS complex, the tallest wave on the ECG, representing the stimulation of the ventricles. Finally, the T wave represents the period when the ventricles recover their electrical forces so they may be stimulated again.
The normal rhythm of the heart is a regular pattern with a rate of between 60 to 100 beats per minute. This rhythm is called normal sinus rhythm because a collection of heart cells called the sinus node controls the rate and rhythm. During an arrhythmia, the heart may beat too rapidly, a situation called tachycardia; too slowly, a situation called bradycardia; or it may beat irregularly. An arrhythmia may result in a skipping or fluttering sensation in the chest (palpitations), light-headedness, a fainting spell (syncope), chest pain, or shortness of breath. Although arrhythmias may go unnoticed, they can be serious. In general, arrhythmias are more common in people with heart disease (especially coronary heart disease, defective heart valves, or a weakened heart). The heart may beat too slowly or too rapidly to pump blood effectively and the blood pressure may drop to a level that is life-threatening. However, having an arrhythmia does not necessarily mean that a person has heart disease. In fact, arrhythmias may occur in people with an otherwise normal heart.
Factors that can bring on arrhythmias in otherwise healthy patients include caffeine, smoking, drugs, alcohol, and stress. People with arrhythmias should be properly evaluated to determine if their problem poses significant risk to their health (or their life), especially since effective treatment or even cure is possible in most cases.