ECGs, Dysrhythmias, and Pacing

What are the 5 steps for interpreting an ECG rhythm?

Rate → Regularity → P waves → PR interval → QRS duration.

What is the normal PR interval?

0.12–0.20 seconds.

What is the normal QRS duration?

Less than 0.12 seconds.

How much time does 1 small ECG box represent?

0.04 seconds.

How do you calculate heart rate using a 6-second ECG strip?

Count the number of R waves in 6 seconds and multiply by 10.

What are the first 2 questions to ask when assessing a dysrhythmia?

1. Does the patient have a pulse? 2. Is the patient stable or unstable?

What is the most important principle when assessing a dysrhythmia?

Treat the PATIENT, not just the monitor. Determine whether the rhythm is impairing perfusion.

What findings suggest impaired cerebral perfusion from a dysrhythmia?

Altered mental status, dizziness, confusion, and restlessness.

What cardiovascular findings suggest poor perfusion?

Hypotension, chest pain, and weak/thready pulses.

What renal finding suggests inadequate perfusion?

Urine output <30 mL/hr or <0.5 mL/kg/hr.

What skin findings suggest poor perfusion?

Cool, pale, clammy or mottled skin and delayed capillary refill.

Does every abnormal heart rate require immediate treatment?

No. The patient's symptoms, stability, and perfusion determine the urgency.

What electrolyte abnormality produces flattened T waves, ST depression, and U waves?

Hypokalemia.

Why is hypokalemia especially concerning in a patient taking digoxin?

Hypokalemia increases the risk of digoxin toxicity.

What ECG changes can occur with hyperkalemia?

Tall peaked T waves, prolonged PR interval, and widening QRS.

What can hypomagnesemia cause on the ECG?

Prolonged QT and increased risk for torsades de pointes.

What QT change is associated with hypocalcemia?

Prolonged QT interval.

What QT change is associated with hypercalcemia?

Shortened QT interval.

What is the key ECG feature of first-degree AV block?

Every P wave conducts, but the PR interval is >0.20 seconds.

What is the classic pattern of second-degree AV block Mobitz I (Wenckebach)?

The PR interval gets longer, longer, longer, then a QRS is dropped.

What is the classic pattern of second-degree AV block Mobitz II?

The PR interval stays constant, but QRS complexes are unexpectedly dropped.

Which is more concerning: Mobitz I or Mobitz II?

Mobitz II. It occurs below the AV node and can progress to complete heart block.

What treatment should the nurse anticipate for unstable Mobitz II?

Prepare for transcutaneous pacing (TCP); atropine may be ineffective.

What is the hallmark of third-degree (complete) heart block?

P waves and QRS complexes occur independently of one another; the atria and ventricles are "divorced."

What treatment may be required for unstable third-degree heart block?

Transcutaneous pacing, followed by transvenous pacing as needed and possibly a permanent pacemaker.

What is electrical capture during transcutaneous pacing?

A pacing spike is followed by the expected P wave and/or QRS complex.

What is mechanical capture during transcutaneous pacing?

The paced electrical activity actually produces cardiac contraction, confirmed by a palpable pulse.

After seeing electrical capture during transcutaneous pacing, what must the nurse do next?

Confirm MECHANICAL capture by checking for a palpable pulse and assessing perfusion.

What is pacemaker failure to capture?

A pacing spike occurs but is NOT followed by the expected P wave or QRS complex.

What is pacemaker failure to sense?

The pacemaker fails to recognize intrinsic cardiac activity and fires when it should not.

What findings can indicate pacemaker failure to sense?

Pacing spikes occurring despite intrinsic beats, such as within a QRS, near a T wave, or immediately after an intrinsic beat.

What should a patient with a permanent pacemaker know about their pulse?

Know the prescribed/set rate and take their pulse for 1 full minute daily.

What symptoms should a patient with a pacemaker report?

Dizziness, syncope, palpitations, chest pain, and shortness of breath.

What is the hallmark ECG finding of STEMI?

ST-segment elevation compared with the isoelectric baseline.

What does ST elevation in a STEMI indicate?

Acute coronary artery occlusion causing myocardial injury.

What symptoms can occur with STEMI?

Chest pressure, dyspnea, diaphoresis, nausea, and pain radiation.

What is the difference between synchronized cardioversion and defibrillation?

Cardioversion synchronizes the shock with the cardiac rhythm; defibrillation delivers an unsynchronized shock.

Which rhythms are the major shockable cardiac-arrest rhythms?

Ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT).

A patient is in ventricular tachycardia. What should the nurse determine FIRST?

Whether the patient has a pulse.

A patient has unstable VT WITH a pulse. What electrical treatment should be anticipated?

Synchronized cardioversion.

A patient has pulseless VT. What treatment should be anticipated?

High-quality CPR and defibrillation.

A patient is in ventricular fibrillation. What treatment should be anticipated?

High-quality CPR and defibrillation.

Should asystole be defibrillated?

No. Asystole is a non-shockable rhythm.

Should PEA be defibrillated?

No. PEA is a non-shockable rhythm.

What is PEA?

Organized electrical activity on the monitor without an effective pulse/cardiac output.

What are the 2 shockable cardiac-arrest rhythms?

VF and pulseless VT.

What are the 2 major non-shockable cardiac-arrest rhythms?

Asystole and PEA.

What is the recommended rate for high-quality CPR according to the course slides?

100–120 compressions/minute.

What is the recommended adult compression depth according to the course slides?

At least 2 inches.

How long should interruptions in chest compressions be?

Less than 10 seconds.

What is the epinephrine dose during cardiac arrest in the course material?

1 mg every 3–5 minutes.

What is the first amiodarone dose listed for cardiac arrest?

300 mg IV bolus.

What is the second amiodarone dose listed for cardiac arrest?

150 mg.

What are the H's reversible causes of cardiac arrest listed in the slides?

Hypovolemia, hypoxia, hydrogen ions/acidosis, hypo-/hyperkalemia, and hypothermia.

What are the T's reversible causes of cardiac arrest listed in the slides?

Tension pneumothorax, cardiac tamponade, toxins, thrombosis-PE, and thrombosis-MI.

A patient's monitor shows a very abnormal rhythm, but the patient is awake, talking, and has a strong pulse. What should the nurse remember?

Assess the patient and perfusion rather than treating the monitor alone.

A patient develops a dysrhythmia with hypotension, confusion, and cool clammy skin. What do these findings suggest?

The dysrhythmia is causing impaired cardiac output and tissue perfusion, making the situation more urgent.

A pacing spike appears on the monitor followed by a QRS, but the patient has no palpable pulse. Has successful pacing been established?

No. Electrical capture is present, but mechanical capture has NOT been confirmed.

A patient with Mobitz II becomes hypotensive and confused. What should the nurse anticipate?

The patient is unstable; prepare for transcutaneous pacing.

A patient has third-degree heart block with severe bradycardia and signs of poor perfusion. What treatment should the nurse anticipate?

Pacing because the atria and ventricles are functioning independently and cardiac output may be inadequate.