1. Is the patient symptomatic or unstable? If so, follow ACLS protocols (see ACLS: Tachycardia), and get a crash cart into the room ASAP.
2. Does this merit investigation, i.e. has the patient been tachycardic all week and has this been noted in the regular team's progress notes?
3. Obtain an ECG and go to examine the patient.
4. It is almost always prudent to slow down a stable narrow-complex supraventricular tachycardia (including suspected rapid a-fib or a-flutter) to make a definitive diagnosis of the rhythm.
- Prior to slowing the rhythm down, obtain continuous telemetry or ECG.
- Consider a vagal maneuver such as carotid massage (press for > 15-30 seconds).
- Deliver adenosine 6 mg rapid IV push repeat with 6 mg, then 12 mg if no response. Be sure to warn the patient of flushing and chest pain associated with adenosine. Theoretic danger of bronchospasm but rarely seen.
Tachycardias are classified according to whether they have a regular rate and whether the QRS on ECG is wide or narrow. They are listed below with diagnostic clues and treatments. When in doubt, call for back up (e.g. cardiology, medicine, or ICU consult).
Narrow QRS, regular rate:
- Sinus tachycardia
- Multiple causes (pain, anxiety, hypoxia, hypovolemia, myocardial dysfunction, fever, anemia, meds, pericarditis, hyperthyroidism, PE, alcohol withdrawal).
- Compare ECG with priors, if available. Maximum HR = 220 age.
- Treat the underlying cause.
- AV nodal reentrant tachycardia (AVNRT) more common than AVRT or AT (see below)
- Caused by existence of dual AV pathways with differing refractory periods, with circuit rhythm set off by a premature atrial contraction (PAC).
- Diagnosis: look for isolated R, pseudo S, or inverted P on ECG. HR typically 180/20.
- Treat with AV nodal block (carotid sinus massage, adenosine, blockers, calcium channel blockers, or digoxin).
- AV reentrant tachycardia (AVRT)
- Caused by presence of accessory pathway causing large circuit rhythm.
- Diagnosis: short RP interval (i.e. RP < PR interval), retrograde P wave.
- Treat with AV nodal blocking (see above).
- Atrial tachycardia (AT)
- Caused by enhanced automaticity of atrial tissue or ectopic atrial pacemaker(s).
- Diagnosis: long RP interval (i.e. RP > PR). HR typically <250.
- Treat with calcium channel blocker.
Narrow QRS, regular rate (continued):
- Atrial flutter with regular block
- Similar to atrial fibrillation. Usually some heart disease present.
- Diagnosis: flutter waves in inferior leads, ventricular rate some multiple of 300 5. When the HR is about 150, always consider atrial flutter.
- Treat with cardioversion, AV nodal blocking.
Narrow QRS, irregular rate
- Atrial fibrillation See also Cardiology: Atrial Fibrillation.
- Causes: see Cardiology: Atrial Fibrillation.
- Diagnosis: relatively straightforward. Look for absence of P waves and flutter waves in all leads. Atrial fibrillation is the most common cause of an irregularly irregular rhythm.
- Treatment: see Cardiology: Atrial Fibrillation.
- Atrial flutter with variable block
- Often difficult to distinguish from atrial fibrillation.
- Look in inferior leads for flutter waves at approximately 300 per minute. May increase AV block transiently with adenosine or carotid sinus massage to reveal flutter waves.
- Treat with AV nodal blocking, cardioversion.
- Multifocal atrial tachycardia (MAT)
- Caused by multiple ectopic atrial pacemakers. Usually associated with pulmonary disease. Also seen in hypomagnesemia, hypokalemia.
- Look for three distinct P wave morphologies in the same lead and three separate PR intervals.
- Treat underlying dysfunction?verapamil may be useful.
- Frequent PACs.
Wide QRS, regular rate
- Ventricular tachycardia (VT) versus supraventricular tachycardia (SVT) with aberrancy. Aberrancy refers to either dysfunction of the His-Purkinje system or presence of an accessory pathway (WPW).
- Given the seriousness of VT, in any patient with heart disease with a wide QRS tachycardia you must assume VT until proven otherwise. See ACLS: Stable Ventricular Tachycardia.
- The Brugada criteria (see Cardiology: Diagnosis of wide-complex tachycardia) are a useful tool to distinguish VT from SVT with aberrancy.
Wide QRS, irregular rate
- VT versus atrial fibrillation with aberrancy. Actually, any condition causing an irregular rate in the presence of aberrancy will cause this.
- Generally treated with cardioversion, either electrical or with procainamide.
Ganz LI, Friedman PL. Supraventricular tachycardia. N Engl J Med 1995; 332:162-73.
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