ECG rhythms: recognize and act

ECG items ask whether you can name the danger and move. Pulse check, CPR, defibrillation, or a calmer rate-control path. MI reperfusion urgency lives in Acute coronary syndromes. Electrolyte-driven peaked T waves live in Electrolytes. This chapter owns common rhythm recognition and the first nurse actions.

How to read a strip under time pressure

Start with the client: responsive? Breathing? Pulse? A perfect label on a dead monitor cable helps no one. Then rate, regularity, P waves, QRS width. Narrow complex usually means the ventricles are being activated over the normal pathway; wide complex raises ventricular origin or aberrancy. And with no pulse, you stop debating labels and run the pulseless algorithm.

Rhythms you must not confuse

Why AF matters beyond the squiggle: the atria quiver instead of kick, clots can form, and stroke risk drives anticoagulation conversations. Why VF/pulseless VT matter: cardiac output is effectively zero. Electricity (defibrillation) plus CPR is the chance to restart an organized rhythm. Why asystole is different: there is no fibrillating myocardium to reset with a shock; perfusion comes from compressions and drugs while you reverse causes.

The distractor that looks advanced is synchronizing a shock into VF, shocking asystole, or walking away from AF because ‘the rate looks okay’ while the client is hypotensive and diaphoretic. Edge case: artifact and loose leads mimic VF or asystole. Glance at the client and the electrodes before you announce a code on a brushing-teeth strip.

Defibrillation vs synchronized cardioversion

Defibrillation is an unsynchronized shock for pulseless VF or pulseless VT. You are not aiming at a QRS because there is no meaningful QRS to synchronize to. Synchronized cardioversion times the shock to the QRS for selected unstable tachycardias with a pulse (shock, severe hypotension, acute pulmonary edema, ongoing ischemia) so you do not hit the T wave and create VF. Same machine family, different mode and different clinical gate.

• No pulse + VF/VT → defibrillation + CPR.
• Pulse + unstable tachyarrhythmia → synchronized cardioversion as ordered.
• Stable with pulse → ABCs, oxygen as needed, expert consultation / ordered meds. Not random shocking.

Antidysrhythmic drug details (amiodarone, adenosine timing, digoxin hold parameters) appear on stems inside ordered pathways. Know the rhythm lane first so you do not give a rate-control answer to a pulseless client.

Bradycardia, SVT, and heart block

Adult bradycardia under about 50 with poor perfusion (hypotension, altered mentation, shock, ischemic pain) is a treat-the-cause and atropine-as-ordered pathway while you prepare pacing if the client stays unstable. Asymptomatic sinus brady in an athlete is not the same stem. Premature ventricular complexes that are frequent, multifocal, or landing on the T wave raise ischemia and electrolyte questions. Fix hypoxia and potassium before you celebrate a clean strip.

Adenosine briefly resets the AV node. Warn the client about a transient flush or pause feeling, keep the crash cart mindset, and use a rapid flush technique as taught so the short-acting drug reaches the heart. Heart block that drops output is an electrical delivery problem: atropine may help some nodal blocks, but complete heart block with instability belongs on a pacing path. The distractor shocks asystole, gives adenosine to a pulseless wide-complex client, or walks away from symptomatic bradycardia because “the strip looks organized.”

Pacemakers: spikes, capture, and the generator

A pacemaker writes a spike on the strip, then the chamber it is supposed to depolarize. Atrial pacing: spike then P. Ventricular pacing: spike then a wide QRS. Dual-chamber devices can do both. Capture means the spike actually produces that beat. Sensing means the device sees the client’s own beats and holds fire. Failure to capture is spikes with no QRS (or no P) while the client is still slow and poorly perfused: check connections, atropine and transcutaneous pacing as ordered, notify. Failure to sense paces regardless of native beats and can land a spike on a T wave (R-on-T, VF risk). Do not place defibrillator or cardioversion pads directly on top of the generator can; use an alternate pad map so current does not arc through the device.

Client teaching after implant: keep the incision dry as taught, report fever or drainage, avoid heavy ipsilateral arm motion for the prescribed window, and carry identification. MRI compatibility is device-specific; do not send every pacemaker client through MRI on habit. Transcutaneous pacing on an unstable complete block is a now intervention, not a wait-for-the-EP-lab courtesy. The distractor that looks technical is chasing millivolt settings while the client has no pulse, or shocking asystole because you saw pacing spikes on a dead battery strip.

Priority map