EKG Rhythm Lab

• P before every QRS: think sinus rhythm; then judge speed.
• Fast + regular + narrow: sinus tachycardia if visible sinus P waves, SVT when P is hidden/obscured and the rate is often very fast.
• Irregularly irregular + no P: think atrial fibrillation; sawtooth activity suggests flutter.
• Wide, fast, organized: treat as ventricular tachycardia until proven otherwise; ask whether there's a pulse.
• No pulse: start CPR; defibrillate VF/pulseless VT, not PEA or asystole.

At 25 mm/sec: 1 small box = 0.04 sec and 1 big box = 0.20 sec. Normal sinus P waves are upright before each narrow QRS with a PR interval of 0.12–0.20 sec. The P wave represents atrial depolarization, QRS ventricular depolarization, and T ventricular repolarization. In PACs, the premature P may have a different shape. In AV blocks, clearly visible P waves help show the conduction failure. In AFib, discrete P waves are absent; in flutter, repeated flutter waves replace normal sinus P waves.

• Failure to pace (output failure): The device should fire, but no spike appears during a pause or slow rhythm. Oversensing can sometimes inhibit appropriate pacing.
• Failure to capture: You can see a pacing spike, but the expected paced P wave or QRS does not follow. A pacer spike alone does not prove effective cardiac output.
• Failure to sense (undersensing): The pacemaker doesn't recognize the patient's own beats, so spikes appear at inappropriate times, sometimes near native QRS complexes or T waves.
• First nursing response: Assess the patient and pulse, monitor perfusion, report suspected malfunction, and arrange device evaluation. Unstable bradycardia may require temporary backup pacing according to emergency protocols.

An organized ECG alone cannot confirm cardiac output: PEA requires an actual pulse check. VT with a pulse can need synchronized cardioversion when unstable; pulseless VT requires CPR and defibrillation. Unstable polymorphic VT should receive an unsynchronized high-energy shock because synchronized shock timing may be unreliable. SVT and AFib/flutter require assessment for serious signs and symptoms before choosing medications or cardioversion.

• Symptomatic adult bradycardia: atropine 1 mg IV, q3–5 minutes as needed, max 3 mg; pacing/vasopressor infusion if ineffective. High-grade AV block may need pacing immediately.
• Appropriate stable regular SVT: vagal maneuvers first, then adenosine 6 mg rapid IV push plus flush; 12 mg if necessary.
• Stable AFib/flutter with RVR: select a beta blocker or nondihydropyridine calcium channel blocker if appropriate. Do not reflexively give both, and check for hypotension, decompensated heart failure or preexcitation.
• Stable monomorphic VT: expert consultation and options such as amiodarone 150 mg IV over 10 minutes, followed by infusion as ordered.
• Cardiac arrest: epinephrine 1 mg IV/IO every 3–5 minutes. Consider amiodarone 300 mg then 150 mg for refractory VF/pulseless VT. Both are adjuncts to CPR and defibrillation, not substitutes.
• STEMI / suspected OMI: urgent 12-lead and cardiology/reperfusion evaluation; antiplatelet/antithrombotic therapy when indicated. NSTEMI is not synonymous with NOMI.

• Normal sinus rhythm: no rhythm-specific treatment. Stable PACs/PVCs or first-degree block: observe and investigate triggers only if clinically indicated.
• Symptomatic bradycardia: atropine; prepare pacing if ineffective.
• Sinus tachycardia: treat fever, pain, dehydration, sepsis, or the underlying driver.
• Stable, regular SVT: vagal maneuvers then adenosine when appropriate.
• Stable AFib/flutter with RVR: diltiazem or beta blocker when not contraindicated, plus stroke-risk assessment.
• Unstable tachycardia with pulse: synchronized cardioversion if rhythm permits; unstable polymorphic VT is an exception requiring an unsynchronized shock.
• Pulseless VT or VF: CPR + defibrillation. PEA or asystole: CPR + epinephrine, no shock.