Evaluation

A 12-lead electrocardiogram must be performed on every patient complaining of palpitations. The presence of a short PR interval and a delta wave (Wolff-Parkinson-White syndrome) is an indication of the existence of ventricular pre-excitation. Significant left ventricular hypertrophy with deep septal Q waves in I, L, and V4 through V6 may indicate hypertrophic obstructive cardiomyopathy. The presence of Q waves may indicate a prior myocardial infarction as the etiology of the palpitations, and a prolonged QT interval may indicate the presence of the long QT syndrome.

Laboratory studies should be limited initially.  Complete blood count can assess for anemia and infection. Serum urea, creatinine and electrolytes to assess for electrolyte imbalances and renal dysfunction. Thyroid function tests may demonstrate a hyperthyroid state. 

Most patients have benign conditions as the etiology for their palpitations. The goal of further evaluation is to identify those patients who are at high risk for an arrhythmia. Recommended laboratory studies include an investigation for anemia, hyperthyroidism and electrolyte abnormalities. Echocardiograms are indicated for patients in whom structural heart disease is a concern.

Further diagnostic testing is recommended for three groups of patients. Those in whom the initial diagnostic evaluation (history, physical examination, and EKG) suggest an arrhythmia, those who are at high risk for an arrhythmia, and those who remain anxious to have a specific explanation of their symptoms. Patients who are considered to be at high risk for an arrhythmia include those with organic heart disease or any myocardial abnormality that may lead to serious arrhythmias. These conditions include a scar from myocardial infarction, idiopathic dilated cardiomyopathy, clinically significant valvular regurgitant, or stenotic lesions and hypertrophic cardiomyopathies.

An aggressive diagnostic approach is recommended for those high-risk patients and can include ambulatory monitoring or electrophysiologic studies.  There are three types of ambulatory EKG monitoring devices: Holter monitor, continuous-loop event recorder, and an implantable loop recorder. The Holter monitor is a 24-hour monitoring system that is worn by the patient and records and continuously saves data. Holter monitors are worn for a few days. The continuous-loop event recorders are also worn by the patient and continuously record data, but the data is saved only when the patient manually activates the monitor. The continuous-loop recorders can be long worn for longer periods of time than the Holter monitors and therefore have been proven to be more cost-effective and efficacious than Holter monitors. Also, because the patient triggers the device when they feel the symptoms, they are more likely to record data during palpitations. An implantable loop recorder is a device that is placed subcutaneously and continuously monitors for cardiac arrhythmias. These are most often used in patients with unexplained syncope and can be used for longer periods of time than the continuous loop event recorders. An implantable loop recorder is a device that is placed subcutaneously and continuously monitors for the detection of cardiac arrhythmias. These are most often used in patients with unexplained syncope and are a used for longer periods of time than the continuous loop event recorders. Electrophysiology testing enables a detailed analysis of the underlying mechanism of the cardiac arrhythmia as well as the site of origin. EPS studies are usually indicated in patients with a high pretest likelihood of a serious arrhythmia.[1][2][6]