Chapter 35. Cardiac Arrhythmias

Patients with cardiac arrhythmias often present to the emergency department. The patient's clinical presentation determines the urgency with which the assessment and management should proceed. Patients with serious signs and symptoms (ie, shock, hypotension, congestive heart failure (CHF), severe shortness of breath, altered level of consciousness, ischemic chest pain, or acute myocardial infarction) require immediate treatment. With stable patients, more time is afforded for review of the 12-lead electrocardiogram (ECG) and rhythm strip to diagnose the cardiac arrhythmia. Review of available prior ECGs may also assist in arrhythmia diagnosis.

1. Obtain as much information as available. Always look at all 12 leads and be sure of name, date, age, correct lead placement, and standardization.

2. Know what each lead looks like normally (Figure 35–1); eg, lead I (and usually lead II and aVF) should look like the textbook PQRST except no Q wave. In lead I, the P, QRS, and T should all be upright, the intervals should be normal and the PR and ST baselines should be isoelectric.

3. A regular tachycardia with a rate close to 150 should prompt a search for atrial flutter.

4. Precise diagnosis of wide complex tachycardias (WCTs) can be difficult. If ventricular rate is irregular consider atrial fibrillation (AF) or atrial flutter with variable conduction and underlying bundle branch block (BBB).

5. Do not rely on computer readings. They may or may not be correct.

6. Single-lead rhythm strips may not have enough information. If time permits, always obtain a 12-lead ECG.

7. You cannot have too many ECGs. Serial ECGs are important. Sinus tachycardia rates tend to change over time.

8. Arrhythmias are common in acute ST elevation myocardial infarctions.

9. Tachyarrhythmias are divided into narrow or wide QRS width and then into regular or irregular.

10. Arrhythmia classifications and terminologies can be confusing and they change as new information becomes available.

11. If the heart rhythm is slow and the patient is hypotensive with signs of poor perfusion, assume transthoracic or transvenous pacing will be needed.

A Note on Cardioversion and Defibrillation

No consensus exists on correct pad positioning and current ACLS guidelines endorse both the conventional or sternal apical positioning (one pad on the superior–anterior right chest just below the level of the clavicle and one pad on the inferolateral left chest) and the anteroposterior (the anterior pad as in the conventional method and the posterior pad on the right or left upper back). However, some authors feel that anteroposterior placement with the anterior pad over the right atrium and the posterior pad at the tip of the left scapula optimizes cardioversion of atrial tachyarrhythmias while placement of the anterior pad over the ventricles and posterior pad again at the tip of the left scapula works well for ventricular arrhythmias.

All currently manufactured defibrillators use biphasic waveforms so unless you are using an older ...