Nurse Arcade
Cardiac + ECG
Trace the flow. Read the rhythm. Assess the patient.
Part 1 – Pump + flow
Follow one drop through the heart
Right heart to lungs; left heart to the body.
Body
Systemic tissues return deoxygenated blood.
Right heart
Venae cavae → RA → tricuspid → RV.
Lungs
Pulmonic valve → pulmonary arteries → gas exchange.
Left heart
Pulmonary veins → LA → mitral → LV.
Body again
Aortic valve → aorta → systemic circulation.
Part 1 – Conduction
Electrical activation coordinates the pump
Depolarization travels through a specialized pathway.
1 – SA node
Usual pacemaker; impulse spreads through atria and produces atrial depolarization.
2 – AV node
Brief conduction delay supports ventricular filling before ventricular activation.
3 – His + bundles
Impulse enters the bundle of His and right and left bundle branches.
4 – Purkinje
Rapid distribution through ventricular myocardium produces coordinated depolarization.
Part 2 – ECG language
Read the normal complex from left to right
At standard speed: small box = 0.04 sec; large box = 0.20 sec.
P wave
Atrial depolarization.
PR interval
Atrial activation through AV conduction; commonly 0.12–0.20 sec.
QRS
Ventricular depolarization; generally under 0.12 sec.
ST segment
Early ventricular repolarization; interpret with symptoms and a 12-lead.
T wave
Ventricular repolarization.
Part 2 – Repeatable rhythm method
Use RATE every time
A fixed sequence prevents pattern-guessing.
R – Rate
Estimate atrial and ventricular rates. For a regular rhythm, 300 divided by large boxes between R waves gives a quick estimate.
A – Arrangement
Is the rhythm regular, regularly irregular, or irregularly irregular? Compare P-P and R-R spacing.
T – Tracing parts
Find P waves, measure PR, inspect QRS width, and check whether each P relates consistently to a QRS.
E – Examine patient
Assess pulse, blood pressure, symptoms, perfusion, oxygenation, mental status, and change from baseline.
Part 3 – Sinus rhythms
Sinus rhythms share one organized pattern
One consistent P before each QRS; consistent PR; usually narrow QRS.
Sinus bradycardia
Below 60/min. May be physiologic or related to medications, ischemia, hypoxia, or conduction disease.
Normal sinus rhythm
60–100/min in adults. Establish baseline and connect rate to symptoms and perfusion.
Sinus tachycardia
Above 100/min. Often reflects pain, fever, hypovolemia, anxiety, hypoxia, anemia, or stress.
Part 3 – Atrial rhythms
Atrial rhythms change P waves and ventricular timing
Assess ventricular response and stability before naming the strip.
Atrial fibrillation
No consistent P waves; ventricular response is usually irregularly irregular. Concerns include rapid response and thromboembolic risk.
Atrial flutter
Organized atrial activity may appear sawtooth. AV conduction may be fixed or variable.
SVT
Rapid, usually regular narrow-complex tachycardia; P waves may be hidden. Assess stability and obtain a 12-lead when feasible.
Part 3 – Heart blocks
AV blocks are P-to-QRS relationship problems
Track every P wave and compare consecutive PR intervals.
First degree
Every P conducts, but PR is consistently longer than 0.20 sec. Think delayed, not dropped.
Mobitz I
PR progressively lengthens until a QRS drops, then the cycle resets.
Mobitz II
Conducted PR intervals stay constant, but some P waves are not followed by QRS complexes.
Third degree
P waves and QRS complexes occur independently. There is no consistent P-to-QRS relationship.
Part 4 – Ventricular rhythms
Wide and chaotic rhythms demand a pulse check
The first question in a wide tachycardia is: does the patient have a pulse?
PVCs
Early, wide, unusual QRS without a preceding normal P wave. Assess frequency, pattern, symptoms, oxygenation, ischemia, and contributors.
Ventricular tachycardia
Fast wide-complex rhythm. With a pulse, assess stability and activate urgent response. Without a pulse, begin cardiac-arrest response.
Ventricular fibrillation
Chaotic activity with no organized QRS and no effective cardiac output. Begin CPR, activate response, and defibrillate per protocol.
Part 4 – Nursing priorities
Stability determines the pathway
Rhythm recognition is only the beginning of the decision.
1 – Assess
Responsiveness, airway, breathing, circulation, pulse, blood pressure, pain, dyspnea, mental status, skin, and perfusion.
2 – Verify
Check leads and artifact; compare monitor rate with the actual pulse; obtain a strip or 12-lead when appropriate.
3 – Support
Position, oxygen, IV access, monitoring, labs, and emergency equipment as ordered or protocol directs.
4 – Escalate
Activate rapid response or code pathway for instability, pulselessness, severe symptoms, or dangerous new rhythm.
5 – Search cause
Review ischemia, hypoxia, electrolytes, medications, volume, temperature, pain, and recent procedures.
6 – Reassess
Trend symptoms, vital signs, rhythm, treatment response, and change from baseline.
Acute coronary syndrome
Treat possible ACS as time-sensitive ischemia
A normal-looking patient or atypical symptom pattern does not exclude myocardial injury.
Presentation
Pressure, heaviness, tightness, dyspnea, diaphoresis, nausea, unusual fatigue, dizziness, or discomfort in the arm, back, neck, jaw, or upper abdomen may occur.
Risk context
Age, tobacco exposure, diabetes, hypertension, dyslipidemia, kidney disease, family history, and known vascular disease shape risk but do not diagnose ACS.
Nursing priorities
Assess ABCs and stability, obtain a focused symptom history and prompt 12-lead ECG, establish monitoring and access, draw ordered serial troponins, and activate the chest-pain pathway.
Escalate
New ischemic symptoms, instability, dangerous dysrhythmia, acute heart-failure signs, or dynamic ECG change require immediate escalation. Check orders and contraindications before medication.
Heart failure
Congestion and low output create different clues
Left/right and reduced/preserved ejection-fraction labels describe the syndrome; bedside priorities come from perfusion and congestion.
Pulmonary congestion
Dyspnea, orthopnea, crackles, hypoxemia, cough, reduced activity tolerance, or acute respiratory distress may reflect left-sided pressure.
Systemic congestion
Dependent edema, jugular venous distention, hepatomegaly, ascites, rapid weight gain, or abdominal symptoms may reflect right-sided pressure.
Low output
Fatigue, cool skin, confusion, oliguria, weak pulses, hypotension, or rising lactate can signal poor perfusion.
Nursing priorities
Trend respiratory status, oxygenation, hemodynamics, rhythm, daily weight, intake/output, edema, renal function, electrolytes, symptoms, medication response, and barriers.
Escalate
New severe dyspnea, pink frothy sputum, chest pain, syncope, rapidly worsening edema, oliguria, confusion, or hypotension requires urgent evaluation.
Apply
Practice the pattern, then name the priority
Answer before checking your course resources.
- Trace blood from the right atrium to the lungs.
- What electrical structure normally initiates atrial depolarization?
- How many seconds are in one large ECG box at standard speed?
- What four checks make up RATE?
- What distinguishes sinus tachycardia from SVT?
- Which rhythm is irregularly irregular without consistent P waves?
- Which block progressively lengthens PR before a dropped QRS?
- Which block has constant conducted PR intervals with dropped QRS complexes?
- What is the first question when ventricular tachycardia appears?
- What bedside finding turns organized electrical activity into a cardiac-arrest concern?
Reference notes
Sources + clinical boundaries
Use current course, facility, and emergency-response standards.
- OpenStax Anatomy and Physiology 2e
- American Heart Association – Arrhythmia
- American Heart Association CPR/ECC
- NIH MedlinePlus – Electrocardiogram
- NCBI Bookshelf – ECG Rhythm Evaluation