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🎧 Episode Summary:
In this engaging episode of CardioCast, Scott, Caleb, Ray, and Dr. John Hill take a deep dive into the clinical nuances of narrow complex rhythms—including both tachycardias and bradycardias. More than a rhythm review, this episode emphasizes the critical thinking needed to understand underlying causes, interpret subtle EKG findings, and choose appropriate interventions—whether pharmacologic or electrical. From sinus tach to SVT, AFib with RVR, WPW, and bradycardia management, this is a must-listen for any EMS provider aiming to master rhythm interpretation and prehospital cardiology care.

🧭 Key Topics Covered:

1. Defining Narrow Complex Rhythms

• Narrow QRS defined as ≤ 0.12 seconds (120 ms)
  
  

• Importance of thinking in milliseconds (ms) over decimal seconds for accuracy
  
  

• EMS versus medical education perspectives on QRS measurement
  
  

2. EKG Interpretation Fundamentals

• Rate > 100 = tachycardia; < 60 = bradycardia
  
  

• Use of the computer’s timing data for accurate interval interpretation
  
  

• Visual assessment still crucial—trust, but verify
  
  

3. Sinus Tachycardia: Asking “Why?”

• Not all tachycardia is pathological—evaluate for cause (e.g., dehydration, fever, exertion)
  
  

• Always correlate rhythm with history, exam, and vitals
  
  

• Common mistake: ignoring compensatory tachycardia in conditions like sepsis
  
  

4. Atrial Fibrillation & RVR

• Controlled vs. uncontrolled AFib
  
  

• Clinical considerations before treating rate: Is the AFib the primary issue or compensatory?
  
  

• When to initiate treatment and when to observe
  
  

• Target rate ranges and ED discharge criteria
  
  

5. SVT, Flutter, and the “150” Myth

• Dangers of oversimplifying SVT as “HR > 150”
  
  

• Differentiating SVT from Flutter with 2:1 block (~150 bpm)
  
  

• Role of vagal maneuvers and adenosine—why diagnostic use is risky
  
  

• Emphasis on morphology and P-wave analysis
  
  

6. WPW (Wolff-Parkinson-White)

• Recognizing delta waves and shortened PR intervals
  
  

• Why adenosine may be dangerous in WPW
  
  

• Safe approach: defer to ED or cardiology when WPW is suspected
  
  

7. Clinical Approach to Bradycardia

• Most patients tolerate slow rates well if perfusion is intact
  
  

• First-line: Assess for parasympathetic stimulation (consider atropine if present)
  
  

• Push-dose epi for augmenting sympathetic tone—preferred in structural or medication-induced bradycardias
  
  

• Fluid bolus often underutilized and low-risk
  
  

8. Pacing Fundamentals

• Indications for transcutaneous pacing in unstable bradycardia
  
  

• Recommended initial settings (e.g., rate 60 bpm, start at 20 mA)
  
  

• Tips for verifying electrical AND mechanical capture
  
  

• Utilizing the "pause" feature to document underlying rhythm
  
  

9. Electrical vs. Chemical Management of Tachycardias

• Cardioversion is often safer than pharmacologic interventions
  
  

• Always reassess sync settings between shocks
  
  

• Don’t over-rely on adenosine—requires full preparedness for adverse effects
  
  

• Sedation optional for urgent cardioversion (atomidate preferred)
  
  

10. Medications Deep Dive

• Rate vs. Rhythm control: Beta blockers, calcium channel blockers, amiodarone, digoxin
  
  

• Red box protocols for beta blockers to avoid harm
  
  

• Push-dose epi: evolving dosing practice (10–50 mcg as needed)
  
  

• Amiodarone as a fourth-line agent in AFib with RVR
  
  

• Role of fluids as diagnostic and therapeutic tool across both tachy- and bradyarrhythmias
  
  

11. Operational Tips & Pitfalls

• Over-reliance on technology vs. touching the patient
  
  

• Misinterpretation of devices (e.g., pleth mismatch with monitor tracing)
  
  

• 4-lead vs. 12-lead utilization strategy
  
  

• Equipment training gaps (e.g., “Pause” button, shock dumping, monitor syncing)
  
  

💡 Clinical Pearls:

• Always ask why the heart rate is abnormal—tachycardia and bradycardia are symptoms, not diagnoses.
  
  

• Know your monitor inside and out—many don’t realize what half the buttons do.
  
  

• When in doubt, electricity is often safer than medication for rhythm correction.
  
  

• Fluid is a therapeutic trial—response can guide treatment.
  
  

• Touch the patient. Monitors lie. Patients don’t.

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