Cardiac Arrhythmias: EKG Interpretation & Nursing Quiz

EKG interpretation requires distinguishing ischemic from non-ischemic ST elevation. Normal variants include early repolarization (concave ST elevation in V2-V3 with J-point notching) and benign patterns in young men. Bundle branch blocks complicate interpretation: LBBB causes always-inverted ST segments making acute MI diagnosis difficult, while RBBB allows meaningful ST analysis suggesting proximal LAD occlusion. The ST segment vector points toward injury—V2-V4 indicates anterior MI, I/aVL/V5-V6 indicates lateral MI, II/III/aVF indicates inferior MI. Reciprocal changes appear opposite the injury zone. AVR elevation with widespread depression suggests global ischemia (left main disease). For inferior MI, III > II suggests RCA involvement; RV infarction is suspected with V1 ST elevation and confirmed with right-sided leads.

This comprehensive module covers the complete 12-lead EKG interpretation process. The systematic three-step approach includes: (1) Analyzing rate and rhythm, (2) Checking for bundle branch blocks or mimics, and (3) Analyzing acute myocardial infarction location. The 12-lead system includes limb leads (1, 2, 3) and augmented voltage leads (aVR, aVL, aVF) as bipolar leads, plus precordial leads (V1-V6) as unipolar leads. The hexaxial reference system maps leads onto a 360-degree circle: lead 1 at 0°, lead 2 at 60°, lead 3 at 120°. Each lead provides a specific camera shot of the heart's electrical activity. Precordial lead placement is essential: V1-V2 view the septal area, V3-V4 view the anterior section, V5-V6 view the lateral side. Posterior leads (V7, V8, V9) visualize the posterior heart wall. Waveform interpretation: positive deflections above the isoelectric line indicate movement toward positive electrodes; negative deflections below indicate movement toward negative electrodes. The P-wave represents atrial depolarization; the Q-wave >0.04 seconds and 25% of R-wave height indicates old MI. The ST segment elevation (1mm+) indicates transmural MI, while depression (1mm+) indicates non-transmural MI or reciprocal changes. The T-wave represents ventricular repolarization; inverted T-waves suggest ischemia.

This final section covers advanced EKG pathology including heart blocks, pacemakers, bundle branch blocks, and myocardial conditions. Heart blocks represent disruptions in electrical signal transmission: First-degree block shows prolonged PR interval (>0.20 sec) without dropped beats. Second-degree Mobitz Type I (Wenckebach) shows progressively lengthening PR intervals until a beat is dropped. Second-degree Mobitz Type II shows fixed PR intervals with intermittent dropped beats. Third-degree (complete) block shows independent atrial and ventricular rhythms with no relationship between P-waves and QRS complexes. Pacemaker identification relies on characteristic vertical spikes: atrial pacing shows spikes before P-waves; ventricular pacing shows spikes before QRS complexes; dual-chamber pacing shows spikes before both. Bundle branch blocks cause one ventricle to contract later, producing wide QRS complexes. Right bundle branch block shows J-point elevation above isoelectric line; left bundle branch block shows J-point depression below isoelectric line. While bunny ear appearance is common, it is not always present. Myocardial ischemia refers to inadequate blood supply to heart muscle; injury indicates actual damage from ischemia; infarction means death of heart muscle tissue. EKG changes progress: ischemia shows ST-segment depression or T-wave inversions; injury shows ST-segment elevation ≥1 mm in two continuous leads; infarction shows persistent Q-waves after ST-segment resolution. Reciprocal changes occur when ST-elevation in one area causes corresponding ST-depression in the opposite area. Left ventricular hypertrophy occurs when the left ventricle becomes enlarged and thickened, typically from chronic pressure overload. Sokolow-Lyon voltage criteria suggest LVH if S-wave depth in lead I plus tallest R-wave in V5-V6 exceeds 35 mm (7 large squares).

A 12-lead EKG provides multiple views of the heart, functioning like 12 cameras at different positions. The 12 leads include three limb leads (I, II, III) which are bipolar, three augmented leads (aVR, aVL, aVF) which are unipolar, and six precordial chest leads (V1-V6). The ST segment, normally isoelectric between the S wave and T wave, when elevated more than one small box in two or more leads, indicates acute MI. Different lead groups view specific heart regions: anterior wall by V1-V4, lateral wall by I, aVL, V5-V6, and inferior wall by II, III, aVF. Hooper's Trick provides a visual method for MI localization by drawing shapes around specific lead groups to identify affected areas.

Accurate lead localization identifies the specific heart region affected by myocardial infarction. Left lateral wall problems appear in leads I, AVL, V5, and V6. Inferior wall problems appear in leads II, III, and aVF. Interventricular septal problems appear in leads V1 and V2. Anterior left ventricular problems appear in leads V3 and V4. Reciprocal changes create mirror-image electrical alterations in leads opposite the injury site—for example, elevation in inferior leads causes depression in leads I, AVL, V5, and V6. This reciprocal relationship helps localize infarction sites and distinguish true ischemia from other causes. Clinical interpretation combines localization with pathological Q wave presence to document MI extent, such as 'anterior lateral wall MI with septal extension.'

The four lethal cardiac arrhythmias requiring immediate intervention in ACLS protocols are Ventricular Fibrillation (irregular rhythm, 150-200 bpm, absent P waves, chaotic QRS complexes), Ventricular Tachycardia (regular rhythm, 200-250 bpm, absent P waves, wide QRS complexes), Pulseless Electrical Activity (organized rhythm without pulse), and Asystole (flatline with no electrical activity); healthcare providers must immediately assess pulse and initiate appropriate resuscitation measures when any of these rhythms are detected on cardiac monitors.

Ventricular fibrillation is the most dangerous cardiac arrhythmia requiring immediate intervention. Priority nursing care includes calling for help, initiating CPR with chest compressions, and preparing for defibrillation. Synchronized cardioversion is used for stable tachyarrhythmias with patient consent, while defibrillation is used for unstable patients without delay. Initial defibrillation energy is 120-200 joules for biphasic defibrillators. Tachyarrhythmias with pulse present are treated with antiarrhythmic medications: sodium channel blockers (flecainide, propafenone), beta blockers (metoprolol), and calcium channel blockers (verapamil).

The ACLS algorithm for defibrillatable arrhythmias (ventricular fibrillation and pulseless ventricular tachycardia) follows a systematic approach: 1) Initial assessment and airway management, 2) Establish IV access, 3) Deliver first defibrillation shock (250J), 4) Perform 2 minutes of CPR, 5) Reassess rhythm, 6) If still defibrillatable, deliver second shock (360J), 7) Continue CPR for 2 minutes, 8) Administer epinephrine (1mg) and amiodarone (300mg), 9) Continue cycle with 360J shocks and medication every 4 minutes until ROSC.

The 2025 BLS/ACLS guidelines introduce key changes: For BLS, women in cardiac arrest should be repositioned rather than having bras removed for defibrillator pad placement. For airway obstruction, use 5 back slaps followed by 5 abdominal thrusts until resolution or deterioration. Automatic compression devices are not recommended. For ACLS, synchronized cardioversion for unstable tachycardia now uses 200 joules for atrial fibrillation/flutter regardless of rhythm type. Double sequential defibrillation and alternative vector placements are no longer recommended. Ultrasound use during arrest is permitted only if it doesn't interrupt compressions and the operator is trained. Endotracheal drug administration is no longer recommended. The Chain of Survival consists of five critical links: early recognition and activation, early high-quality CPR, early defibrillation, early advanced life support, and early post-cardiac arrest care. The BLS algorithm begins with scene safety assessment, responsiveness check, and emergency activation. For breathing patients with pulse, provide rescue breathing (1 breath every 6 seconds). For non-breathing patients without pulse, initiate CPR with 30:2 ratio. The defibrillator should be applied immediately upon arrival regardless of compression cycle. Shockable rhythms (VF, pVT) require defibrillation; non-shockable rhythms (asystole, PEA) require continued CPR for 2 minutes before reanalysis. For non-shockable rhythms, continue CPR while administering epinephrine 1 mg IV every 3-5 minutes without limit. For shockable rhythms, prepare defibrillation while compressions continue. Administer maximum available energy (200 joules for biphasic, 360 for monophase). After first shock, resume CPR for 2 minutes while establishing IV/IO access. Reassess rhythm after 2 minutes. Epinephrine can be administered starting after the second defibrillation attempt. Amiodarone (300 mg initial, 150 mg second dose) or lidocaine can be administered starting after the third defibrillation attempt. High-quality CPR requires chest compressions of at least 5 cm depth at 100-120 compressions per minute, with minimal interruptions. Use capnography to monitor adequacy: PETCO2 should be 20-25 mmHg (ideal), with values below 10 mmHg indicating inadequate compressions. Return of Spontaneous Circulation (ROSC) is evidenced by pulse return and abrupt sustained PETCO2 increase. For refractory rhythms, systematically evaluate reversible causes using the 5 H's (Hypovolemia, Hypoxia, Hydrogen ions, Hypo/Hyperkalemia, Hypothermia) and 5 T's (Tension pneumothorax, Thromboembolism, Tamponade, Toxins, Thrombosis). Endotracheal intubation is optional during CPR and should only be performed by skilled operators who can intubate on first attempt in under 10 seconds. Confirm placement using capnography (most reliable), chest rise observation, colorimetric CO2 detector, or chest X-ray after ROSC. For opioid overdose, administer naloxone preferably intranasally. For pregnant patients in cardiac arrest, perform high-quality CPR while manually displacing the uterus to the left side. Stop magnesium sulfate infusion and administer calcium gluconate if indicated. Connect fetal monitoring. If no ROSC within 5 minutes, prepare for emergency cesarean delivery. For bradycardia (<50 bpm), assess hemodynamic instability using five criteria: hypotension, altered mental status, shock, cardiac ischemia, or acute heart failure. If unstable, administer oxygen, assist ventilation, and connect to monitor. First-line treatment is atropine 1 mg IV, repeatable every 3-5 minutes up to 3 mg total. If atropine fails, consider transcutaneous pacing, dopamine, or epinephrine. For complete heart block, transcutaneous pacing is first-line. For tachycardia (>150 bpm), assess instability first. If unstable, proceed to synchronized cardioversion. If stable, assess QRS width: wide-complex tachycardia receives adenosine (6 mg initial, 12 mg second dose) or alternatives; narrow-complex tachycardia receives vagal maneuvers and adenosine.

This video provides comprehensive training on Basic Life Support (BLS) and Advanced Cardiac Life Support (ACLS) protocols for cardiac arrest management. The BLS algorithm emphasizes scene safety, checking responsiveness, breathing, and pulse within 10 seconds, followed by high-quality CPR (30 compressions to 2 ventilations at 100-120 bpm) and AED use. The ACLS algorithm distinguishes between shockable rhythms (VFib, pulseless VT) requiring immediate defibrillation and non-shockable rhythms (asystole, PEA) requiring epinephrine administration. Key quality indicators include EtCO2 monitoring (target >10 mmHg) and arterial pressure monitoring. Special considerations include opioid overdose management with naloxone, pregnant patient positioning at 30 degrees, and therapeutic hypothermia (32-36°C) for post-arrest neurological protection.

Hemodynamic instability in tachycardia means the patient has become symptomatic (hypotension, confusion, drowsiness, palpitations) due to the rhythm. The tachycardia must be the cause of the instability, not just a coincidental finding. If the patient was already unstable before the rhythm change, the tachycardia may not be the primary cause.

Hemodynamic instability in arrhythmias is assessed using five criteria: (1) altered mental status (agitation or decreased consciousness), (2) chest pain with anginal characteristics (tightness, burning, radiation, sweating, nausea), (3) respiratory pattern changes, (4) hypotension, and (5) signs of shock (prolonged capillary refill >3 seconds, cold skin, weak pulse). An arrhythmia is unstable if any one criterion is present, requiring immediate intervention. This assessment determines whether emergency treatment is necessary.

Nurses must recognize clinical signs of hemodynamic instability. Hypotension with cold, clammy skin and delayed capillary refill indicates shock requiring urgent intervention. Hypertension with facial flushing and sweating represents the opposite extreme. Differentiating cardiovascular fever from infectious fever is crucial—cardiovascular changes affect temperature through metabolic work, while infections trigger immune responses. Nursing interventions include providing warmth for hypothermia and cooling measures for hyperthermia. Understanding these relationships enables better patient assessment and care planning.

Hemodynamic instability refers to abnormal vital parameters preventing normal body function. Ventricular tachycardia is unstable because it causes hemodynamic compromise. ECG assessment includes: regularity, rate (60-100 normal), P-wave presence, QRS width (<0.12s), PR interval (<0.20s), ST segment, and T-wave amplitude. These parameters guide treatment decisions for stable versus unstable rhythms.

When observing rhythm alterations, avoid focusing solely on the type of arrhythmia. Ask three key questions: Is the rhythm regular or irregular? Is the patient hemodynamically stable or unstable? Does this arrhythmia explain the clinical deterioration? Different arrhythmias have different implications: atrial fibrillation compromises ventricular filling; ventricular tachycardia directly affects perfusion; bradycardias can produce hypotension or consciousness alterations. The same rhythm can have different repercussions depending on the patient (e.g., 140 bpm may be tolerated in a young patient but cause collapse in severe heart failure). Avoid the error of focusing solely on values or taking them as isolated data points. What matters are trends: how heart rate is changing, whether urine output is progressively decreasing, whether blood pressure is falling progressively.