Option 2: Stable tachycardia

The patient does not appear to have any signs of unstable tachycardia. The monitor shows a heart rate of 135 beats/minute, but the patient appears comfortable and says she does not have any symptoms. Her blood pressure is 125/82 mm Hg, and oxygen saturation is 98% on room air. You perform a focused history and physical examination, being careful to assess for signs of heart failure; none are present.

Question: What is the best next step?

Make your choice, then click on the explanation bubble to reveal the answer.

• Obtain basic laboratory studies (e.g., troponin, electrolytes, CBC).
• Order a chest x-ray.
• Consult cardiology.
• Determine if the tachycardia is a wide-complex tachycardia (WCT) or a narrow-complex tachycardia (NCT).

You examine the patient's ECG to determine if they have a WCT or NCT and if the rhythm is regular or irregular. You also check the patient's chart for any old ECGs for comparison.

As you interpret the patient's ECG, you start thinking about the differential diagnoses for the tachycardia.

Question: What are three types of tachycardia to consider for each of the following?

Think of your three, then click on the explanation bubble to see some examples.

• Regular NCT
• Irregular NCT
• Regular WCT
• Irregular WCT

See “Differential diagnosis of tachycardia” for an expanded list. Also, see the flowchart below for more information on how to narrow your differential.

Accurate identification of the underlying rhythm and any conduction abnormalities is key, as findings determine management (e.g., adenosine is contraindicated in the presence of an accessory pathway; calcium channel blockers are contraindicated in ventricular tachycardia).

The patient's ECG shows an irregular narrow-complex tachycardia with no discernible P waves. The patient has a history of atrial fibrillation. You diagnose atrial fibrillation with rapid ventricular response (Afib with RVR). Now it's time to initiate management.

Question: What is the preferred way to manage this patient's Afib with RVR?

Make your choice, then click on the explanation bubble to reveal the answer.

• Rate control
• Rhythm control

For more information on managing Afib with RVR (and managing Afib in general), check out “Atrial fibrillation.”

Evaluate for features of acute decompensated heart failure. Avoid beta blockers and nondihydropyridine calcium channel blockers in patients with LV dysfunction and decompensated heart failure, as these can compromise hemodynamic function.

ECG interpretation is the most important diagnostic step in stable tachycardia. Fortunately, stable tachycardia allows some time to interpret the ECG and determine the rhythm. Once you know the rhythm, you can tailor management accordingly.

ECG interpretation

Take some time to freshen up your ECG interpretation skills with the examples below.

If you haven't explored the other scenario yet, jump over to “Option 1: Unstable tachycardia.” You can also return to the main module; see “Heart in overdrive wrap-up.”