Module 4: Cardiovascular Emergencies

Section 1: Anatomy and Physiology of the Cardiovascular System (Link)

1.1 Cardiac Anatomy

1.1.1 Heart Structure

• Layers of the Heart Wall

  • Endocardium: Inner lining of the heart chambers.

  • Myocardium: Muscular middle layer responsible for contraction.

  • Epicardium: Outer layer; part of the pericardium.

• Chambers of the Heart

  • Right Atrium

    • Receives deoxygenated blood from the superior and inferior vena cava.

  • Right Ventricle

    • Pumps deoxygenated blood to the lungs via the pulmonary artery.

  • Left Atrium

    • Receives oxygenated blood from the pulmonary veins.

  • Left Ventricle

    • Pumps oxygenated blood to the systemic circulation via the aorta.

• Heart Valves

  • Atrioventricular (AV) Valves

    • Tricuspid Valve: Between right atrium and right ventricle.

    • Mitral (Bicuspid) Valve: Between left atrium and left ventricle.

  • Semilunar Valves

    • Pulmonary Valve: Between right ventricle and pulmonary artery.

    • Aortic Valve: Between left ventricle and aorta.

1.1.2 Coronary Circulation

• Right Coronary Artery (RCA)

  • Supplies the right atrium, right ventricle, part of the left ventricle, and the conduction system (SA node in 60%, AV node in 90%).

• Left Coronary Artery (LCA)

  • Divides into:

    • Left Anterior Descending (LAD) Artery

      • Supplies anterior wall of left ventricle, anterior septum.

    • Circumflex Artery

      • Supplies lateral wall of left ventricle, left atrium, SA node in 40%, AV node in 10%.

1.2 Cardiac Electrophysiology

1.2.1 Electrical Conduction System

• Sinoatrial (SA) Node

  • Pacemaker of the heart; intrinsic rate of 60-100 bpm.

• Atrioventricular (AV) Node

  • Delays impulse; intrinsic rate of 40-60 bpm.

• Bundle of His

  • Conducts impulses from AV node to ventricles.

• Purkinje Fibers

  • Distribute impulse through ventricles; intrinsic rate of 20-40 bpm.

1.2.2 Action Potentials

• Phases of Cardiac Cell Action Potential

  • Phase 0: Rapid depolarization (influx of Na⁺).

  • Phase 1: Initial repolarization (K⁺ begins to exit).

  • Phase 2: Plateau phase (Ca²⁺ influx balances K⁺ efflux).

  • Phase 3: Rapid repolarization (K⁺ efflux continues).

  • Phase 4: Resting membrane potential.

• Refractory Periods

  • Absolute Refractory Period: No new impulse can be initiated.

  • Relative Refractory Period: Stronger-than-normal stimulus can initiate an impulse.

1.3 Hemodynamics

• Cardiac Output (CO)

  • Definition: Volume of blood pumped by the heart per minute.

  • Formula: CO = Heart Rate (HR) × Stroke Volume (SV).

• Stroke Volume Determinants

  • Preload: Volume of blood returning to the heart.

  • Afterload: Resistance the heart must overcome to eject blood.

  • Contractility: Strength of myocardial contraction.

• Blood Pressure Regulation

  • Influenced by cardiac output and systemic vascular resistance (SVR).

  • Baroreceptors and chemoreceptors modulate heart rate and vessel tone.

Section 2: Cardiovascular Assessment

2.1 History Taking

• Chief Complaint

  • Chest pain, dyspnea, palpitations, syncope.

• History of Present Illness

  • Onset, Provocation/Palliation, Quality, Radiation, Severity, Time (OPQRST).

• Past Medical History

  • Previous cardiac events, hypertension, diabetes, hyperlipidemia.

• Medications

  • Beta-blockers, anticoagulants, nitrates, ACE inhibitors.

• Family History

  • Cardiovascular diseases in immediate family members.

• Social History

  • Smoking, alcohol use, illicit drug use (e.g., cocaine).

2.2 Physical Examination

• General Appearance

  • Level of consciousness, distress, skin color.

• Vital Signs

  • Blood pressure, heart rate, respiratory rate, temperature, oxygen saturation.

• Inspection

  • Jugular venous distention (JVD), peripheral edema, cyanosis.

• Palpation

  • Pulses (radial, carotid, femoral), capillary refill, skin temperature.

• Auscultation

  • Heart sounds (S1, S2), murmurs, gallops (S3, S4), lung sounds (crackles, wheezes).

• Additional Assessments

  • Peripheral vascular assessment: Checking for signs of deep vein thrombosis (DVT).

  • Neurological status: To detect any signs of stroke due to cardiac emboli.

2.3 ECG Acquisition

• Lead Placement

  • Limb Leads: RA, LA, RL, LL.

  • Precordial Leads: V1-V6.

• Patient Preparation

  • Explain procedure, position supine, shave hair if necessary.

• Common Errors to Avoid

  • Misplaced leads leading to misinterpretation.

  • Poor skin contact causing artifacts.

Section 3: ECG Interpretation

3.1 Basics of ECG Interpretation

• Rate Calculation

  • Regular Rhythm: 300 divided by the number of large squares between R waves.

  • Irregular Rhythm: Number of QRS complexes in 6 seconds (30 large squares) multiplied by 10.

• Rhythm Analysis

  • P wave presence and morphology.

  • PR interval duration (normal: 0.12-0.20 seconds).

  • QRS complex duration (normal: ≤0.12 seconds).

  • QT interval.

• Axis Determination

  • Normal axis vs. left/right axis deviation.

3.2 Identification of Arrhythmias

3.2.1 Sinus Rhythms

• Normal Sinus Rhythm

  • Rate: 60-100 bpm.

  • Regular rhythm, P wave preceding each QRS.

• Sinus Bradycardia

  • Rate: <60 bpm.

• Sinus Tachycardia

  • Rate: >100 bpm.

• Sinus Arrhythmia

  • Slight irregularity with respirations.

3.2.2 Atrial Arrhythmias

• Premature Atrial Contractions (PAC)

  • Early P waves with abnormal morphology.

• Atrial Fibrillation

  • Irregularly irregular rhythm, no discernible P waves, wavy baseline.

• Atrial Flutter

  • Sawtooth flutter waves, atrial rate ~250-350 bpm.

• Supraventricular Tachycardia (SVT)

  • Rapid rate >150 bpm, narrow QRS complexes.

3.2.3 Ventricular Arrhythmias

• Premature Ventricular Contractions (PVC)

  • Early, wide QRS complexes without preceding P wave.

• Ventricular Tachycardia (VT)

  • Rate >100 bpm, wide QRS complexes.

  • Monomorphic VT: Uniform QRS morphology.

  • Polymorphic VT: Varying QRS morphology (e.g., Torsades de Pointes).

• Ventricular Fibrillation (VF)

  • Chaotic, irregular rhythm, no discernible waves.

3.2.4 Heart Blocks

• First-Degree AV Block

  • Prolonged PR interval (>0.20 seconds), constant.

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

  • Progressive PR interval prolongation until a QRS is dropped.

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

  • Constant PR intervals with dropped QRS complexes.

• Third-Degree AV Block (Complete Heart Block)

  • No association between P waves and QRS complexes.

3.3 Ischemia and Infarction Patterns

• Ischemia

  • ST Depression: Horizontal or downsloping depression >0.5 mm.

  • T Wave Inversion: Symmetrical inversion in leads facing the affected area.

• Injury

  • ST Elevation: ≥1 mm in limb leads, ≥2 mm in precordial leads in two contiguous leads.

• Infarction

  • Pathological Q Waves: >0.04 seconds wide and >25% the height of the R wave.

3.4 Localization of Myocardial Infarctions

• Anterior Wall MI

  • Leads V1-V4 (LAD occlusion).

• Lateral Wall MI

  • Leads I, aVL, V5, V6 (Circumflex artery occlusion).

• Inferior Wall MI

  • Leads II, III, aVF (RCA occlusion).

• Posterior Wall MI

  • ST depression in V1-V3, tall R waves (Consider reciprocal changes).

• Right Ventricular MI

  • ST elevation in V4R (Right-sided ECG needed).

Section 4: Acute Coronary Syndromes (ACS)

4.1 Pathophysiology

• Types of ACS

  • Unstable Angina

    • Chest pain at rest or with minimal exertion.

    • No biomarkers of myocardial injury.

  • Non-ST Elevation Myocardial Infarction (NSTEMI)

    • Symptoms of ischemia.

    • Elevated cardiac biomarkers.

    • No ST elevation on ECG.

  • ST Elevation Myocardial Infarction (STEMI)

    • Complete occlusion of a coronary artery.

    • ST elevation on ECG.

    • Elevated biomarkers.

4.2 Management of ACS

4.2.1 Immediate Actions

• MONA Protocol

  • Morphine: For pain unrelieved by nitrates (2-5 mg IV).

  • Oxygen: To maintain SpO₂ ≥94%.

  • Nitroglycerin: 0.4 mg SL every 5 minutes, max 3 doses.

  • Aspirin: 324 mg chewable PO unless contraindicated.

4.2.2 ECG Acquisition and Interpretation

• Perform a 12-lead ECG within 10 minutes of patient contact.

• Identify STEMI criteria and infarct localization.

4.2.3 Pharmacological Interventions

• Antiplatelet Agents

  • Aspirin: As above.

  • Clopidogrel: If directed by medical control.

• Anticoagulants

  • Heparin: As per protocol.

• Beta-Blockers

  • Metoprolol: 5 mg IV every 5 minutes up to 15 mg, cautious use.

• Fibrinolytics

  • Evaluate contraindications if considering pre-hospital administration.

4.2.4 Pre-hospital Thrombolysis

• Inclusion Criteria

  • Chest pain suggestive of MI within 12 hours.

  • ST elevation ≥1 mm in two or more contiguous leads.

• Absolute Contraindications

  • Active bleeding, known bleeding disorders, recent surgery, history of hemorrhagic stroke.

4.2.5 Transport Considerations

• STEMI Centers

  • Expedite transport to facilities capable of percutaneous coronary intervention (PCI).

• Alert Receiving Facility

  • Early notification for activation of cath lab.

Section 5: Cardiac Arrhythmia Management

5.1 Advanced Cardiac Life Support (ACLS) Algorithms

5.1.1 Cardiac Arrest Algorithm

• Ventricular Fibrillation/Pulseless Ventricular Tachycardia

  • Initiate CPR

    • High-quality chest compressions with minimal interruptions.

    • Ratio 30:2 if not intubated; continuous compressions if advanced airway in place.

  • Defibrillation

    • Deliver shock at 200 J biphasic (or manufacturer recommendation).

    • Resume CPR immediately after shock.

  • Medications

    • Epinephrine: 1 mg IV/IO every 3-5 minutes.

    • Amiodarone: First dose 300 mg IV/IO, second dose 150 mg if refractory.

• Asystole/Pulseless Electrical Activity (PEA)

  • CPR

  • Epinephrine: As above.

  • Consider Reversible Causes (Hs and Ts):

    • Hs: Hypovolemia, hypoxia, hydrogen ion (acidosis), hypothermia, hypo-/hyperkalemia.

    • Ts: Tension pneumothorax, tamponade (cardiac), toxins, thrombosis (pulmonary or coronary).

5.1.2 Tachycardia with Pulse Algorithm

• Stable vs. Unstable Assessment

  • Unstable Signs: Hypotension, altered mental status, signs of shock, ischemic chest discomfort, acute heart failure.

• Unstable Tachycardia

  • Immediate Synchronized Cardioversion

    • Narrow Regular: 50-100 J.

    • Narrow Irregular: 120-200 J biphasic.

• Stable Tachycardia

  • Wide QRS (>0.12 seconds)

    • Amiodarone: 150 mg IV over 10 minutes.

    • Procainamide: 20-50 mg/min until arrhythmia suppressed.

  • Narrow QRS

    • Vagal Maneuvers: Valsalva, carotid sinus massage (with caution).

    • Adenosine: 6 mg rapid IV push followed by 20 mL flush; second dose of 12 mg if needed.

5.1.3 Bradycardia Algorithm

• Identify and Treat Underlying Cause

  • Unstable Signs: Hypotension, altered mental status, signs of shock, ischemic chest discomfort, acute heart failure.

• Atropine

  • 0.5 mg IV every 3-5 minutes, maximum of 3 mg.

• Transcutaneous Pacing

  • Set rate to 60-80 bpm; increase mA until capture is achieved.

• Dopamine Infusion

  • 2-20 mcg/kg/min if pacing unavailable or ineffective.

• Epinephrine Infusion

  • 2-10 mcg/min.

5.2 Transcutaneous Pacing

• Indications

  • Symptomatic bradycardia unresponsive to atropine.

  • Second-degree type II and third-degree AV blocks.

• Procedure

  • Apply Pads

    • Anterior-posterior or sternal-apex positions.

  • Set Rate

    • Typically 70 bpm.

  • Adjust Output

    • Increase milliamps (mA) until electrical capture is achieved.

  • Assess for Mechanical Capture

    • Check for palpable pulses corresponding with paced rhythm.

  • Patient Comfort

    • Consider sedation and analgesia if time permits.

5.3 Defibrillation

5.3.1 Manual Defibrillation

• Indications

  • Ventricular fibrillation.

  • Pulseless ventricular tachycardia.

• Procedure

  • Apply Pads

    • Ensure proper placement and skin contact.

  • Select Energy Level

    • Follow manufacturer guidelines (e.g., 200 J biphasic).

  • Charge Defibrillator

  • Ensure Safety

    • Verify no one is in contact with the patient or equipment.

  • Deliver Shock

    • Press shock button; resume CPR immediately.

5.3.2 Synchronized Cardioversion

• Indications

  • Unstable tachyarrhythmias (SVT, atrial fibrillation/flutter, VT with pulse).

• Procedure

  • Activate Sync Mode

    • Ensure device is synchronized with R wave.

  • Select Appropriate Energy Level

  • Sedate Patient

    • If time and condition allow.

  • Charge and Deliver Shock

    • Ensure synchronization indicator is active before delivery.

5.3.3 Automated External Defibrillator (AED) Usage

• Use AED in Cardiac Arrest

  • Follow prompts.

  • Attach pads; do not delay defibrillation.

Section 6: Heart Failure and Shock

6.1 Heart Failure

6.1.1 Pathophysiology

• Left-Sided Heart Failure

  • Failure of left ventricle causes pulmonary congestion.

  • Symptoms: Dyspnea, orthopnea, crackles, cough.

• Right-Sided Heart Failure

  • Failure of right ventricle causes systemic congestion.

  • Symptoms: JVD, peripheral edema, hepatomegaly.

6.1.2 Management

• Positioning

  • Sitting position to reduce preload.

• Oxygen Therapy

  • CPAP/BiPAP if indicated.

• Nitroglycerin

  • Reduces preload and afterload.

• Diuretics

  • Furosemide: 20-80 mg IV (as per protocol).

• Morphine

  • For anxiety and dyspnea relief.

6.2 Cardiogenic Shock

6.2.1 Recognition

• Signs and Symptoms

  • Hypotension (SBP <90 mmHg).

  • Tachycardia.

  • Cool, clammy skin.

  • Altered mental status.

  • Oliguria.

6.2.2 Management

• Airway and Breathing

  • Ensure oxygenation and ventilation.

• Circulation

  • Initiate IV access.

  • Careful Fluid Challenge

    • 250 mL bolus if lungs are clear, reassess frequently.

• Inotropic Support

  • Dopamine Infusion: 5-20 mcg/kg/min to maintain perfusion.

• Transport

  • Rapid transport to appropriate facility.

Section 7: Critical Thinking in Cardiovascular Emergencies

7.1 Differential Diagnosis

• Non-Cardiac Causes of Chest Pain

  • Pulmonary embolism.

  • Aortic dissection.

  • Pneumothorax.

  • Gastroesophageal reflux.

• Adjusting Treatment Plans

  • Based on evolving patient condition and response to interventions.

7.2 Special Populations

• Elderly Patients

  • Atypical presentations

  • Comorbid conditions complicating assessment

• Women

  • Less typical chest pain

  • Higher incidence of misdiagnosis

• Diabetic Patients

  • May have silent MIs

7.3 Ethical Considerations

• Do Not Resuscitate (DNR) Orders

  • Verify documentation.

  • Respect patient autonomy.

• End-of-Life Care

  • Provide comfort measures.

  • Communicate with family members.

Conclusion

Mastery of cardiovascular emergency management is crucial for paramedics, as timely and effective interventions can significantly improve patient outcomes. This module has provided a comprehensive overview of cardiac anatomy and physiology, assessment techniques, ECG interpretation, and advanced management strategies for various cardiac emergencies. Continual practice and staying current with guidelines are essential to maintaining proficiency in this dynamic aspect of emergency medical care.