diseases and genetic disorders can lead to the most serious and potentially life-threatening and disabling conditions.
Arrhythmias may manifest in a variety of ways, and some patients with arrhythmias are asymptomatic. Others may experience palpitations (pounding sensations in the chest), chest discomfort, dyspnea, syncope, or near syncope (Libby et al., 2008). Syncope, sometimes called “fainting,” is defined as a sudden loss of consciousness and postural tone with spontaneous recovery. Near syncope is a period of altered consciousness. Since syncope is complete loss of consciousness, it is not merely a feeling of light-headedness, momentary weakness, or dizziness. Cardiac syncope is due to inadequate blood flow to the brain from any cardiac cause, such as obstruction of flow or disturbance in rhythm or conduction resulting in inadequate cardiac output (Grubb and Olshansky, 1998). Determining the cause of syncope can be difficult, as there are several cardiac and noncardiac disturbances that may lead to loss of consciousness (Grubb and Olshansky, 1998).
Cardiac syncope may be caused by bradycardia, tachycardia, valve disease, or myocardial disease leading to hypotension. Cardiac syncope may also be due to nonarrhythmic causes, such as vasovagal syncope (mediated by discharge of the vagus nerve) that is purely vasodepressor (hypotensive) with no cardioinhibitory (bradycardic) component, an extremely rare condition. Noncardiac causes of loss of consciousness include epilepsy and pseudoseizures from psychiatric disease (Grubb and Olshansky, 1998). Since syncope is a symptom and not a disease, it is important to identify accurately its underlying cause. Due to the multiple causes of syncope, it is important to recognize that only syncope in association with arrhythmias is discussed here.
Bradycardia is defined as a heart rate of less than 60 beats per minute and requires treatment if accompanied by symptoms, which may include fatigue, lethargy, nausea, shortness of breath, mental confusion, dizziness, and near syncope or syncope (Grubb and Olshansky, 1998). A diagnosis of bradycardia in the absence of symptoms is rarely an indication for treatment, for example, the implantation of a pacemaker. Symptoms drive the need for intervention.
Tachycardias, sometimes called tachyarrhythmias, may be supraventricular or ventricular in origin. Supraventricular arrhythmias may be often highly symptomatic but are rarely life threatening (Wood et al., 2010). Examples include atrioventricular nodal reentrant tachycardia (AVNRT), atrioventricular reentrant tachycardia (AVRT) in association with the Wolff-Parkinson-White syndrome, atrial flutter, and atrial fibrillation. The latter