EVIDENCE-BASED ANSWER
The best evidence about the diagnostic evaluation of resting tachycardias in adults is currently outlined by practice guidelines.1 Initial evaluation includes clinical history, physical examination, and 12-lead electrocardiogram (ECG). If the initial evaluation suggests a sinus tachycardia with narrow QRS complexes and no identifiable secondary cause, a 24-hour Holter monitor is usually recommended (strength of recommendation: C, based on expert opinion).
CLINICAL COMMENTARY
Wide-complex tachycardias and irregular heartbeats should be urgently managed
Laurel Woods, MD
Group Health Family Medicine Residency Program, Seattle, Wash
This Clinical Inquiry organizes a rational approach to tachycardia, which is frequently an incidental and asymptomatic finding on patient intake. The recommendation of evaluating a 12-lead ECG for sinus vs non-sinus tachycardia, then further investigating underlying causes, helps frame the workup in an approachable manner. Particularly helpful is the pointer that the wide-complex tachycardias and irregular heartbeats should be urgently managed, whereas the rest can be assessed at a more relaxed pace. For nonurgent cases it is important to keep in mind the differential diagnosis and rationally evaluate the likely causes. In my patient population, I tend to see sinus tachycardias in young healthy patients in whom no secondary cause aside from anxiety is identified. Oftentimes I follow up after initiating treatment for anxiety or its underlying cause and find that the tachycardia has resolved. In these cases, I have been less aggressive about ordering a 24-hour Holter monitor.
Evidence Summary
Heart rate varies by age; however, tachycardia in adults is usually defined as a rate exceeding 100 beats/minute.1 Tachycardia at rest requires a diagnostic evaluation. However, our search found no systematic reviews, randomized trials, or prospective cohort studies relevant to this question. The highest level of evidence we located was an international practice guideline developed by the American College of Cardiology, the American Heart Association Task Force on Practice Guidelines, and the European Society of Cardiology Committee for Practice Guidelines.1
This joint guideline recommends that the diagnostic evaluation of a hemodynamically stable patient should begin with a clinical history, physical examination with relevant labs, and 12-lead ECG.1 Many patients with tachycardia are asymptomatic; however, common symptoms and complaints include palpitations, fatigue, lightheadedness, chest discomfort, dyspnea, presyncope, or syncope.1 If the patient has experienced symptoms, it is of crucial importance to obtain a clinical history describing the pattern in terms of the number of episodes, duration, frequency, mode of onset, and possible triggers.1
The main goals of the physical examination, labs, and the 12-lead ECG are to determine if the patient has a sinus or non-sinus tachycardia and to look for other findings that may suggest either a cause for the tachycardia or any complications resulting from the tachycardia.
First, determine if the patient’s heartbeat is regular or irregular. Atrial flutter and atrial fibrillation are common causes of an irregular heartbeat that can easily be diagnosed with a 12-lead ECG. Second, determine the width of the QRS interval: narrow QRS complex tachycardias are supraventricular (from the sinus node, the atria, and the atrioventricular junction) in origin, and wide QRS complex tachycardias are usually ventricular (from all sites below the AV junction).2,3 If an irregular heartbeat or wide-complex tachycardia is detected, appropriate management (including possible urgent referrals) should begin immediately.1 A stable patient with a regular rhythm and a narrow QRS complex can be further investigated at a more relaxed pace.
Refer to the TABLE for a listing of common secondary causes for sinus tachycardia, which should direct lab investigations. If no secondary cause is easily identifiable, a 24-hour monitor is recommended as the next step.
TABLE
Potential secondary causes of resting sinus tachycardia5-7
| Hyperthyroidism |
| Fever |
| Sepsis |
| Anxiety |
| Pheochromocytoma |
| Anemia |
| Hypotension and shock |
| Pulmonary embolism |
| Acute coronary ischemia and myocardial infarction |
| Heart failure |
| Chronic pulmonary disease |
| Hypoxia exposure to medications, stimulants, or illicit drugs |
| Malignancy |
| Pregnancy |