Basic Dysrhythmia Workshop Part II

Electrocardiogram (ECG) Principles and Monitoring

• Fundamentals of ECG Monitoring

  • An electrocardiogram (ECG/EKG) reflects the real-time cardiac electrical activity of the heart.

  • Cardiac telemetry monitors are primarily designed for rhythm identification and continuous rate/rhythm monitoring, not for clinical diagnostic interpretation such as diagnosing an acute myocardial infarction (MI).

  • Any suspected ischemic, injury, or rhythm changes observed on a telemetry monitor strip must be verified immediately with a standard $12$-lead ECG.

  • EKG rhythm interpretation is systematically based on recognizing normal versus abnormal waveforms, intervals, and segment deflections.

• Lead Views and Monitoring Configurations

  • A standard $12$-lead ECG provides $12$ distinct electrical views (leads) of the heart.

  • Waveforms dynamically change their morphology and direction of deflection depending on the lead viewed.

  • In Lead II, normal cardiac waveforms are positive (upright). Consequently, continuous bedside and telemetry monitoring is routinely performed in Lead II.

• Electrode Placement Protocols

  • 3-Wire Patient Cable Placement:

    • Right Arm (RA): White electrode.

    • Left Arm (LA): Black electrode.

    • Left Leg (LL): Red electrode.

  • 5-Lead Electrode Placement:

    • RA (White): Positioned near the right mid-clavicular line, directly beneath the clavicle.

    • LA (Black): Positioned near the left mid-clavicular line, directly beneath the clavicle.

    • V / Brown (Chest): Positioned to the right of the sternum at the $4\text{th}$ intercostal space.

    • RL (Green): Positioned between the $6\text{th}$ and $7\text{th}$ intercostal space along the right mid-clavicular line.

    • LL (Red): Positioned between the $6\text{th}$ and $7\text{th}$ intercostal space along the left mid-clavicular line.

  • 12-Lead Precordial (Chest) Lead Locations (V1–V6):

    • V1: $4\text{th}$ intercostal space at the right sternal border.

    • V2: $4\text{th}$ intercostal space at the left sternal border.

    • V3: Positioned directly midway between lead V2 and lead V4.

    • V4: $5\text{th}$ intercostal space along the left mid-clavicular line.

    • V5: $5\text{th}$ intercostal space along the left anterior axillary line.

    • V6: $5\th$ intercostal space along the left mid-axillary line.

• Criteria for Selecting the Monitoring Lead

  • Choose a lead where the EKG waveform is completely above or completely below the isoelectric baseline.

  • Ensure the selected lead waveform is clean and entirely free from electrical artifact.

  • Confirm that the waveform exhibits no baseline wander.

  • Select a lead where the QRS complex amplitude is $2\text{ to }3 \times$ the amplitude of the P wave and T wave (critical for accurate arrhythmia detection and rate counting).

  • Ensure tall, narrow QRS complexes for normal intrinsic beats, making ectopic beats clearly distinguishable.

  • If an artificial pacemaker is present, select a lead where pacemaker spikes reach at least $50\%$ of the R-wave amplitude.

ECG Graph Paper and Measurements

• Graph Calibration Units

  • ECG paper consists of calibrated grid lines for precise temporal and voltage measurements.

  • Time is measured horizontally across the strip; voltage/amplitude is measured vertically ($5\,\text{mm} = 0.5\,\text{mV}$).

  • Grid composition: Heavy-lined boxes contain $25$ smaller squares arranged in a $5 \times 5$ grid.

  • $1\,\text{small square}$ ($1\,\text{mm}$) horizontally = $0.04\,\text{seconds}$ wide.

  • $1\,\text{large box}$ ($5\,\text{small squares}$) horizontally = $0.20\,\text{seconds}$ wide.

  • A $3\,\text{second}$ interval spans $15\,\text{large boxes}$.

  • A standard rhythm strip is a $6\,\text{second}$ strip, spanning $30\,\text{large boxes}$.

• Heart Rate Calculation Formulas

*   **Method 1: Small Box Method ($1500$ Rule)**
    *   Formula: Divide $1500$ by the exact number of small boxes between two consecutive R waves.
    *   Characteristics: Most precise and accurate method; takes time to count; strictly applicable **only to regular rhythms**.
*   **Method 2: Large Box Method ($300$ Rule / Sequence Method)**
    *   Formula: Divide $300$ by the number of large boxes between two consecutive R waves.
    *   Sequence values:
        *   $1\,\text{large square} = 300\,\text{bpm}$
        *   $2\,\text{large squares} = 150\,\text{bpm}$
        *   $3\,\text{large squares} = 100\,\text{bpm}$
        *   $4\,\text{large squares} = 75\,\text{bpm}$
        *   $5\,\text{large squares} = 60\,\text{bpm}$
        *   $6\,\text{large squares} = 50\,\text{bpm}$
    *   Characteristics: Quick visual estimate; moderately accurate; strictly applicable **only to regular rhythms**.
*   **Method 3: 6-Second Strip Method ($10$ Multiplier Rule)**
    *   Formula: Count the total number of R waves contained within a $6\,\text{second}$ strip ($30\,\text{large boxes}$) and multiply by $10$.
    *   Characteristics: Rapid calculation; less precise; **mandatory method for irregular rhythms**.

The Isoelectric Line and Cardiac Cycle Waveforms

• Isoelectric Line

  • The flat baseline on an ECG representing absence of electrical activity or equal electrical forces.

  • Electrical waves deflect upward (positive) or downward (negative) from the isoelectric baseline.

• P Wave

  • The first wave of the cardiac cycle.

  • Represents atrial depolarization.

  • Morphology variations:

    • Tall, pointed P wave ($P\text{-pulmonale}$): Indicates Right Atrial Hypertrophy (RAH).

    • Biphasic or notched/M-shaped P wave ($P\text{-mitrale}$): Associated with Mitral Valve Prolapse (MVP), mitral stenosis, or Hypertension (HTN).

• PR Interval

  • Measured from the beginning of the P wave to the beginning of the QRS complex.

  • Represents the time required for atrial depolarization plus the impulse delay through the AV node.

  • Normal duration: $0.12\text{ to }0.20\,\text{seconds}$.

• QRS Complex

  • Represents ventricular depolarization.

  • Consists of three individual potential deflections:

    • Q Wave: First negative (downward) deflection preceding an R wave.

    • R Wave: First positive (upward) deflection.

    • S Wave: Negative deflection following an R wave, or the second negative deflection.

  • QRS Interval (Duration): Measured from the start of the QRS complex to the end of the QRS complex (J point). Normal duration is $\le 0.10\,\text{seconds}$.

• ST Segment

  • Measured from the end of the QRS complex (J point) to the beginning of the T wave.

  • Represents early ventricular repolarization.

  • Ischemic variations:

    • ST Segment Depression (or Inversion): Indicates non-transmural (subendocardial) ischemia.

    • ST Segment Elevation: Indicates transmural (epicardial / full-thickness myocardial) injury/ischemia.

• T Wave and Cardiac Refractory Periods

  • The T wave represents ventricular repolarization and follows the QRS complex.

*   **Refractory Periods**:
    *   Absolute Refractory Period (ARP): Extends from the QRS complex through the peak of the T wave. Cardiac cells cannot be depolarized by any stimulus, regardless of intensity.
    *   Relative Refractory Period (RRP): Corresponds to the downslope/vulnerable period of the T wave. A strong ectopic electrical stimulus during this vulnerable period can trigger depolarization.
    *   Normal Refractory Period / Non-Refractory Period (NRP): Cardiac cells are fully repolarized and capable of responding normally to standard stimuli.
*   **R-on-T Phenomenon**: Occurs when a Premature Ventricular Contraction (PVC) lands directly on the vulnerable T wave during the Relative Refractory Period. This dangerous interaction frequently precipitates lethal ventricular arrhythmias, specifically Ventricular Tachycardia (VT) or Ventricular Fibrillation (VF).

• QT Interval and Corrected QT (QTc)

  • Measured from the beginning of the Q wave to the end of the T wave.

  • Represents total duration of ventricular depolarization and repolarization.

  • Normal duration: $0.34\text{ to }0.43\,\text{seconds}$.

  • Varies based on age, gender, and underlying heart rate.

  • Prolongation or shortening of the QT interval increases susceptibility to lethal ventricular dysrhythmias (e.g., Torsades de Pointes).

  • Etiologies of Prolonged QT:

    • Acquired Prolongation: Pharmacological agents such as Levaquin, Pronestyl (procainamide), Quinidine, Dofetilide, Monostat; or electrolyte imbalances (hypokalemia, hypomagnesemia, hypocalcemia).

    • Inherited Long QT Syndrome (LQTS): Genetic mutations causing defective cardiac sodium ($\text{Na}^+$) or potassium ($\text{K}^+$) ion channels.

  • Bazett\'s Formula for Corrected QT (QTc):         $\text{QTc} = \frac{\text{QT}}{\sqrt{\text{RR}}}$

    • Example Calculation: Given an $\text{RR interval} = 24.5\,\text{small boxes} \times 0.04\,\text{s} = 0.98\,\text{seconds}$ and a $\text{QT interval} = 13\,\text{small boxes} \times 0.04\,\text{s} = 0.52\,\text{seconds}$:         $\text{QTc} = \frac{0.52}{\sqrt{0.98}} = \frac{0.52}{0.9899} = 0.525\,\text{seconds} \quad (\text{or } 0.53\,\text{s})$

• U Wave

  • A rare, small deflection appearing immediately after the T wave.

  • Most commonly indicates severe Hypokalemia.

Systematic Interpretation of Cardiac Rhythms

• Six-Step Systematic Rhythm Interpretation Process

  1. Analyze the P wave and evaluate its specific relationship to the QRS complex.

  2. Determine overall rhythm regularity (compare P–P and R–R spacing).

  3. Calculate the Heart Rate.

  4. Measure interval durations: PR Interval.

  5. Measure the QRS complex duration.

  6. Measure the QT Interval.

• Evaluating Regularity

  • A rhythm is categorized as regular when normal waveforms are spaced equal distances apart across the strip.

  • Assess both R–R interval regularity (ventricular rate) and P–P interval regularity (atrial rate).

• Classification Basis of Dysrhythmias

  • Disturbances in Impulse Formation:

    • Tachycardias, Bradycardias, Premature (ectopic) beats, Escape beats, Flutter, Fibrillation.

  • Disturbances in Impulse Conduction:

    • Sinoatrial (SA) blocks, Atrioventricular (AV) blocks, Intraventricular conduction delays/blocks.

  • Clinical Severity Hierarchy: Classified as Minor, Major, or Lethal based on whether the dysrhythmia compromises hemodynamics or causes sudden cardiac arrest.

Normal Sinus Rhythm (NSR)

• Diagnostic Rules for Normal Sinus Rhythm

  • Rhythm: Strictly Regular.

  • Heart Rate: $60\text{ to }100\,\text{bpm}$.

  • P Waves: Uniform, rounded, upright in Lead II; present prior to every QRS complex.

  • PR Interval: $0.12\text{ to }0.20\,\text{seconds}$.

  • QRS Duration: $< 0.10\,\text{seconds}$.

Sinoatrial Node Dysrhythmias

• Sinus Bradycardia

  • Rules:

    • Rhythm: Regular.

    • Heart Rate: $< 60\,\text{bpm}$.

    • P Waves: Rounded, upright, one preceding each QRS complex.

    • PR Interval: $0.12\text{ to }0.20\,\text{seconds}$.

    • QRS Duration: $< 0.10\,\text{seconds}$.

  • Signs & Symptoms: May be asymptomatic, or present with weakness, fatigue, dizziness, lightheadedness, syncope/fainting.

  • Etiologies: Well-conditioned endurance athletes, heightened vagal tone, myocardial ischemia, or drug effects (beta-blockers, calcium channel blockers, digoxin).

  • Therapeutic Interventions:

    • No treatment required if completely asymptomatic.

    • If symptomatic: Supplemental Oxygen, Atropine IV, Dopamine infusion, Epinephrine infusion, or Transcutaneous/Transvenous Pacemaker.

• Sinus Tachycardia

  • Rules:

    • Rhythm: Regular.

    • Heart Rate: $101\text{ to }180\,\text{bpm}$ (Maximum age-predicted HR formula: $220 - \text{age in years}$).

    • P Waves: Rounded, upright, preceding each QRS complex.

    • PR Interval: $0.12\text{ to }0.20\,\text{seconds}$.

    • QRS Duration: $< 0.10\,\text{seconds}$.

  • Signs & Symptoms: Asymptomatic, or chest pain (angina) and shortness of breath (dyspnea). Elderly patients demonstrate heightened sensitivity to rapid rates.

  • Etiologies: Physical exertion, fever, acute pain, anxiety, hypovolemia, hypoxia, caffeine, cocaine, energy drinks, heart failure, anemia, terbutaline administration, hyperthyroidism.

  • Therapeutic Interventions:

    • Identify and treat underlying etiology.

    • Pharmacological management: Digoxin, Calcium Channel Blockers, Beta-Blockers.

• Sinus Arrhythmia

  • Characterized by irregular SA node discharge synchronized with the respiratory cycle: heart rate increases during inspiration and decreases during expiration.

  • Frequently observed in individuals $< 30\,\text{years}$ old, post-operative patients, or secondary to normal respiratory variations.

• Sinus Exit Block and Sinus Arrest

  • Sinus Exit Block occurs when the SA node fires, but the impulse is blocked from leaving the sinus node to depolarize the atria, causing a dropped P-QRS-T complex.

  • Sinus Arrest occurs when the SA node completely fails to generate an impulse, producing a pause of variable duration.

Atrial Dysrhythmias

• Wandering Atrial Pacemaker (WAP) and Multifocal Atrial Tachycardia (MAT)

  • Characterized by changing site of impulse initiation across the atria or AV junction.

  • Requires clear presence of at least 3 distinct P wave morphologies within the same lead.

  • Wandering Atrial Pacemaker (WAP): Heart rate is $\le 100\,\text{bpm}$.

  • Multifocal Atrial Tachycardia (MAT): Pathological condition where heart rate exceeds $100\,\text{bpm}$.

*   **Causes of MAT**:
    *   Chronic lung disease (COPD, severe emphysema).
    *   Metabolic disturbances.
    *   Hypoxemia.
    *   Hypokalemia.
    *   Critically ill Medical Intensive Care Unit (MICU) patients.

• Premature Atrial Contractions (PAC)

  • Rules:

    • Rhythm: PAC interrupts the underlying baseline rhythm (premature beat).

    • Heart Rate: Depends on underlying rhythm.

    • P Waves: Early (premature) beat; P wave morphology differs from normal sinus P wave (flattened, notched, inverted, or hidden in preceding T wave).

    • PR Interval: Usually normal ($0.12\text{ to }0.20\,\text{seconds}$).

    • QRS Duration: $< 0.10\,\text{seconds}$.

  • Noncompensatory Pause: The pause following a PAC is noncompensatory (the interval containing the PAC is shorter than two normal PP cycles).

*   **Signs & Symptoms**: Typically asymptomatic.
*   **Therapeutic Interventions**:
    *   None required if infrequent.
    *   Treat underlying cause: emotional stress, cardiac trauma, alcohol consumption (ETOH), hypoxia, fatigue, excess caffeine, electrolyte imbalances, COPD.
    *   Pharmacological management: Beta-Blockers.

• Supraventricular Tachycardia (SVT) / Atrial & Junctional Tachycardia

  • Characteristics:

    • Heart Rate: $150\text{ to }250\,\text{bpm}$.

    • Origin: $10\text{ to }15\%$ atrial origin; $85\text{ to }90\%$ junctional re-entry mechanism.

    • Paroxysmal onset and offset; narrow QRS complex rhythm without visible P waves.

  • Therapeutic Interventions:

    • Vagotonic maneuvers (carotid sinus massage, Valsalva maneuver).

    • Adenosine Protocol: Administer $6\,\text{mg}$ rapid IV push; if unresolved within $1\text{ to }2\,\text{minutes}$, administer $12\,\text{mg}$ rapid IV push.

    • Central Venous Catheter (CVC) Dosing: Reduce initial dose to $3\,\text{mg}$ if injecting into a central line.

    • Dose Adjustments & Interactions:

      • Increase dose in patients with heavy caffeine consumption or theophylline therapy.

      • Decrease dose or use extreme caution in patients taking Tegretol (carbamazepine).

      • Absolute Contraindication: Do NOT administer in patients taking Persantine (dipyridamole) as Adenosine degradation is blocked, causing extreme potency and prolonged heart block.

      • Use with extreme caution in asthmatic patients (can induce severe bronchospasm).

• Atrial Flutter

  • Rules:

    • Rhythm: Atrial rhythm is strictly regular; ventricular rhythm may be regular or irregular depending on AV conduction ratio.

    • Heart Rate: Atrial rate $250\text{ to }350\,\text{bpm}$; ventricular rate varies.

    • P Waves: Classic sawtooth or flutter waves (F waves).

    • PR Interval: None measurable.

    • QRS Duration: $< 0.10\,\text{seconds}$.

*   **Signs & Symptoms**:
    *   Normal ventricular rate: Asymptomatic.
    *   Rapid Ventricular Rate (RVR): Palpitations, angina, dyspnea, hypotension.
*   **Therapeutic Interventions**:
    *   Synchronized Cardioversion.
    *   Calcium Channel Blockers (Diltiazem / Cardizem dosing protocol: $0.25\,\text{mg/kg}$ IV bolus over $2\,\text{minutes}$; followed by $0.35\,\text{mg/kg}$ IV bolus if needed; continuous maintenance infusion at $10\,\text{mg/hr}$, titrate as needed for up to $24\,\text{hours}$).
    *   Beta-Blockers, Digoxin.

• Atrial Fibrillation

  • Rules:

    • Rhythm: Irregularly Irregular.

    • Heart Rate: Atrial rate unmeasurable ($700\text{ to }1000\,\text{bpm}$ fibrillatory waves); Ventricular rate:

      • Controlled Response: Ventricular rate $< 100\,\text{bpm}$.

      • Rapid Ventricular Response (RVR): Ventricular rate $> 100\,\text{bpm}$.

    • P Waves: No identifiable P waves; chaotic fibrillatory baseline (f waves).

    • PR Interval: None measurable.

    • QRS Duration: $< 0.10\,\text{seconds}$.

*   **Signs & Symptoms**: Palpitations, faint radial pulse, fatigue, dyspnea, heightened risk for systemic thromboembolism and stroke.
*   **Therapeutic Interventions**:
    *   Synchronized Cardioversion.
    *   Pharmacological agents: Beta-Blockers, Calcium Channel Blockers, Digoxin, Anticoagulants (warfarin, NOACs).
    *   Advanced therapies: Radiofrequency Ablation, Biatrial Pacing, Implantable Atrial Defibrillators, Surgical Maze Procedure.

Junctional (Nodal) Rhythms

• Characteristics of AV Junctional Impulse Formation

  • Impulse originates within the AV junction when the SA node fails or slows.

  • P wave variations (due to retrograde atrial conduction):

    • Inverted P wave preceding QRS complex (PR interval $< 0.12\,\text{seconds}$).

    • P wave buried/hidden completely inside QRS complex.

    • Inverted P wave following the QRS complex.

  • Junctional Classification by Rate:

    • Junctional Escape Rhythm: Rate $40\text{ to }60\,\text{bpm}$.

    • Accelerated Junctional Rhythm: Rate $60\text{ to }100\,\text{bpm}$.

    • Junctional Tachycardia: Rate $> 100\,\text{bpm}$.

  • Premature Junctional Contraction (PJC): An ectopic premature beat originating in the AV node featuring an inverted/absent P wave and a narrow QRS complex.

Atrioventricular (AV) Blocks

• First-Degree AV Block

  • Characterized by delayed conduction through the AV node.

  • PR Interval is prolonged ($> 0.20\,\text{seconds}$) and remains strictly constant for every beat. Every P wave is followed by a QRS complex.

• Second-Degree AV Block Type I (Mobitz I / Wenckebach)

  • Progressive lengthening of the PR interval on consecutive beats until a P wave completely fails to conduct and a QRS complex is dropped.

  • Cycle repeats itself regularly or irregularly.

• Second-Degree AV Block Type II (Mobitz II)

  • Intermittent non-conducted P waves resulting in dropped QRS complexes without prior PR interval prolongation (PR interval of conducted beats remains constant).

  • High risk of progressing to Complete Heart Block.

• Third-Degree AV Block (Complete Heart Block)

  • Complete AV dissociation: Atrial impulses do not conduct to the ventricles.

  • P waves occur at a regular intrinsic sinus rate; QRS complexes occur independently at an intrinsic junctional ($40\text{ to }60\,\text{bpm}$) or ventricular escape rate ($20\text{ to }40\,\text{bpm}$).

  • Associated with Adams-Stokes disease when originating in the AV node or Bundle of His.

• The Heart Block Poem Memory Guide

  • If the R is far from P, then you have a FIRST DEGREE.

  • Longer, longer, longer, drop! Then you have a WENKEBACH.

  • If some Ps don\'t get through, then you have MOBITZ II.

  • If Ps and Qs don\'t agree, then you have a THIRD DEGREE.

Ventricular Dysrhythmias

• Premature Ventricular Contraction (PVC)

  • Rules:

    • Rhythm: PVC interrupts the baseline underlying rhythm.

    • Heart Rate: Depends on underlying rhythm.

    • P Waves: Absent prior to the PVC.

    • PR Interval: None for the PVC.

    • QRS Duration: PVC QRS is wide and bizarre, lasting $> 0.10\,\text{seconds}$.

  • PVC Presentation Patterns:

    • Bigeminal PVC (Bigeminy): Every second beat is a PVC.

    *   Trigeminal PVC (Trigeminy): Every third beat is a PVC.

    *   Couplet: Two consecutive PVCs.

    *   Triplet / Salvo: Three consecutive PVCs (classified as a short burst of Ventricular Tachycardia).

*   **Signs & Symptoms**: Palpitations, fatigue, dizziness; frequent PVCs precipitate severe hemodynamically compromising dysrhythmias.
*   **Therapeutic Interventions**:
    *   None if asymptomatic.
    *   Antidysrhythmic medications: Amiodarone (Cordarone, Pacerone), Beta-Blockers.

• Ventricular Tachycardia (VT)

  • Rules:

    • Rhythm: Usually regular.

    • Heart Rate: Ventricular rate $150\text{ to }250\,\text{bpm}$ (Slow VT is defined as $< 150\,\text{bpm}$).

    • P Waves: Absent.

    • PR Interval: None.

    • QRS Duration: Wide and bizarre, $> 0.10\,\text{seconds}$.

  • Morphological Variants:

    • Monomorphic VT: Uniform QRS complex appearance.

    • Polymorphic VT / Torsades de Pointes: QRS complexes continuously twist around the isoelectric line (resembles a party streamer pattern); directly linked to prolonged QT interval.

*   **Signs & Symptoms**: Dyspnea, palpitations, light-headedness, angina, collapse, cardiac arrest.
*   **Therapeutic Interventions**:
    *   **Pulseless VT**: High-quality CPR, Immediate Unsynchronized Defibrillation, Vasopressors (Epinephrine), Anti-arrhythmics (Amiodarone).
    *   **Stable VT with Pulse**: Amiodarone IV infusion; consider IV Magnesium Sulfate (especially for Torsades de Pointes).

• Ventricular Fibrillation (VF)

  • Rules:

    • Rhythm: Chaotic, extremely irregular.

    • Heart Rate: Not measurable.

    • P Waves: None.

    • PR Interval: None.

    • QRS Duration: None (no recognizable waves or complexes).

*   **Signs & Symptoms**: Complete unconsciousness, absent heart sounds, undetectable peripheral pulses, unmeasurable blood pressure, respiratory arrest, cyanosis, pupil dilation.
*   **Therapeutic Interventions (ACLS Protocols)**:
    *   Immediate Defibrillation.
    *   High-quality CPR.
    *   Epinephrine, Vasopressin, Amiodarone ($300\,\text{mg}$ IV push initial bolus), Magnesium Sulfate.
    *   Endotracheal Intubation.

• Idioventricular Rhythm

  • Ventricular escape rhythm occurring at an intrinsic rate of $20\text{ to }40\,\text{bpm}$, wide QRS complexes, absent P waves.

• Asystole

  • Rules: Total absence of electrical and mechanical activity; flatline.

  • Therapeutic Interventions:

    • BLS and ACLS Protocols.

    • Immediate high-quality CPR, Endotracheal Intubation, Epinephrine, Vasopressin.

    • Note: Asystole is not a shockable rhythm; do not defibrillate.

• Pulseless Electrical Activity (PEA) and Reversible Causes

  • Presence of an organized electrical rhythm on the ECG monitor without detected mechanical ventricular contraction or pulse.

  • The 6 T\'s and 6 H\'s of PEA:

    • The 6 T\'s:

      • Tamponade (cardiac)

      • Tension pneumothorax

      • Thrombus (MI)

      • Thrombus (Pulmonary Embolism)

      • Toxins

      • Trauma

    • The 6 H\'s:

      • Hypoxia

      • Hypovolemia

      • Hyperkalemia / Hypokalemia

      • Hydrogen ions (Acidosis)

      • Hypothermia

      • Hypoglycemia

Advanced Pharmacological and Device Protocols

• Amiodarone Continuous Intravenous Drip Protocol

*   Preparation: $450\,\text{mg}$ in $250\,\text{mL } D_5W$ (must be prepared in glass or special polyolefin plastic non-PVC containers).
*   Loading Infusion: $1\,\text{mg/min}$ for $6\,\text{hours}$ (rate: $33.3\,\text{mL/hr}$, delivering $360\,\text{mg}$).
*   Maintenance Infusion: $0.5\,\text{mg/min}$ for $18\,\text{hours}$ (rate: $16.6\,\text{mL/hr}$, delivering $540\,\text{mg}$).
*   Maximum cumulative dose: $2.2\,\text{grams}$ per $24\,\text{hours}$.
*   Pharmacokinetics: Half-life ($t_{1/2}$) is approximately $40\,\text{days}$.

• Cardiac Pacemakers

  • Types: External (transcutaneous/temporary) and Internal (transvenous/permanent).

  • Functions: Impulse generation for severe bradycardias, or overdrive pacing to suppress tachycardias.

  • Placement sites: Atrium, Ventricle, or Dual-chamber.

*   **Pacemaker Malfunction Types**:
    *   Failure to Sense: Pacemaker fails to detect intrinsic cardiac electrical activity, delivering spikes inappropriately.
    *   Failure to Pace: Pacemaker fails to generate an electrical output spike when indicated.
    *   Failure to Capture: Pacemaker fires an electrical spike, but the myocardium fails to depolarize (no P wave or QRS complex following spike).
*   **Nursing Care**: Continuous ECG monitoring, bed rest for several hours post-implantation, monitor apical pulse and clinical symptoms.
*   **Patient Education**: Surgical incision care, report symptoms immediately, carry Pacemaker ID card at all times, avoid strong electromagnetic fields, alert airport security (triggers metal detectors), maintain schedule for periodic pacemaker evaluations.

• Defibrillation

  • Unsynchronized electrical shock delivered to depolarize myocardium and allow SA node to reset.

  • Indications: Pulseless Ventricular Tachycardia, Ventricular Fibrillation.

  • Technique: Use conductive jelly or adhesive pads. Apply firm paddle pressure against chest wall.

*   Paddle/Pad Placement:
    *   $2\text{nd}$ intercostal space, right sternal border.
    *   $5\text{th}$ intercostal space, left anterior axillary line.
*   Announce "CLEAR" loudly prior to discharge.
*   Biphasic non-escalating energy setting: $150\text{ to }200\,\text{Joules}$.

• Synchronized Cardioversion

  • Electrical shock synchronized specifically with the R wave to prevent accidental delivery during the vulnerable T wave (avoiding R-on-T phenomenon).

  • Indications: Ventricular Tachycardia with pulse, Atrial Fibrillation, Atrial Flutter, Supraventricular Tachycardia.

  • Requires conscious sedation prior to procedure if patient is stable.

  • Energy setting: $25\text{ to }50\,\text{Joules}$.

• Automated External Defibrillator (AED)

  • External portable device that automatically analyzes underlying cardiac rhythms and prompts or delivers an electrical shock for shockable rhythms (VF / pulseless VT).

• Implantable Cardioverter-Defibrillator (ICD)

  • Subcutaneously implanted device that continuously monitors heart rhythm, automatically delivering defibrillation upon detecting VF or cardioversion/overdrive pacing upon detecting VT.