Asystole, Agonal Rhythms, and Paced Beats
Key facts for recognizing flatline states, dying rhythms, and pacemaker tracings on an EKG.
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Questions Covered in This Set
10 cards to master
What defines asystole on an EKG?
Complete absence of ventricular electrical activity — no QRS complexes anywhere on the strip, usually with a gently wandering baseline rather than a perfectly straight line.
What is ventricular standstill (P-wave asystole)?
Regular P waves marching along with no QRS following any of them — the atria fire but the ventricles are electrically silent. It is a dying rhythm, not third-degree block (which still has an escape QRS).
Why must you distinguish fine VF from asystole?
Fine VF can look flat at low gain, but VF is shockable and asystole is not — mistaking one for the other changes treatment immediately.
What is the mnemonic before calling a flatline?
"Check the patient, check the leads, check the gain" — and confirm asystole in two leads; a disconnected electrode produces a perfect flatline.
List the interpretation checklist for a suspected flatline.
1) Is the patient unresponsive and pulseless? 2) Are leads/cables intact? 3) Turn up the gain for fine fibrillation. 4) Check a second lead. 5) Look for P waves without QRSs.
How is asystole managed?
Non-shockable: high-quality CPR and epinephrine while searching for reversible causes (Hs and Ts). Defibrillation does nothing useful.
What are the features of an agonal rhythm?
Rate under ~20 bpm (often 4–10/min), very wide bizarre slurred QRSs (sometimes ≥0.30 s), no P waves, irregular spacing, progressively wider and slower — almost always pulseless (a form of PEA).
What does a pacer spike look like?
A narrow, sharp, near-vertical deflection often only 1–2 ms wide; bipolar leads make them small, and digital monitors may add an enhanced marker.
How do you recognize atrial pacing?
A spike immediately precedes a P wave, followed by a normal narrow QRS (intact conduction system).
How do you recognize ventricular pacing?
A spike immediately precedes a wide QRS (>0.12 s), typically with an LBBB-like pattern and discordant T waves — discordance is normal in paced beats.
