ECG Rhythm Notes: PVCs, VT/VF, Geminal Patterns, and Pacemakers

Intrinsic ventricular rate and basic rhythm concepts

  • Intrinsic rate for the ventricles: 20-40\ \text{bpm}
    • We don’t talk about rates below 20\ \text{bpm} because it doesn’t function well.
    • If the rate is around 40, that is considered the intrinsic rate in some examples.
  • Ventricular rhythm characteristics
    • Ventricular rhythms are typically wide and “weird” on the ECG; there is no normal P-wave coupling to the QRS complexes.
    • The rhythm is often described as wide QRS complexes with no clear P waves, hence “ventricular rhythm.”
    • Historical note: the term IVR (Idioventricular Rhythm) was used, but the I was dropped; Idio means unknown why it happened—often we don’t care why it happened; we just recognize the pattern.
    • The device (ECG machine) reads the rapid, forceful depolarization of the ventricles, producing wide, abnormal QRS morphology.
    • If you see a slow rhythm with a single initiating site in the ventricles, the QRS morphology is relatively uniform because one focus drives the rhythm.

Focus and morphology: why it matters

  • There is typically one place in the ventricles that initiates the beat when it’s a ventricular rhythm.
    • One focus → all ventricular complexes look the same (unifocal).
    • If there are two or more foci driving the rhythm, morphologies will vary (multifocal);
      this is worse than a single focus.
  • Morphology as an index of severity
    • If all ventricular complexes look the same (same morphology), it likely indicates one focus and is somewhat more controlled than multiple foci.
    • If there are two or more different morphologies, there are multiple active foci and the situation is worse.
  • The focus concept helps determine how bad the rhythm is and guides urgency of response.

Underlying rhythms and focus terminology

  • Underlying rhythms and their focus
    • Sinus rhythm: focus in the sinus node; P waves present and upright, PRI normal, QRS narrow.
    • Ventricular rhythm: focus in the ventricles; QRS wide, no reliable P waves.
    • Junctional rhythm: focus near the AV junction; often missing or inverted P waves.
  • Morphology consistency as a clue to focus
    • If all QRS complexes are same shape, they likely originate from a single ventricular focus (unifocal).
    • If QRS morphologies differ, there are multiple foci (multifocal).

Rate basics and how to talk about rhythm

  • Rate concepts
    • Intrinsic ventricular rhythm is around 20-40\ \text{bpm}; anything above this can be described as accelerated if still not lethal, depending on context.
    • If the rhythm is faster than the intrinsic rate but not yet over the normal resting rate (~100 bpm), you may describe it as accelerated ventricular rhythm.
  • Regular vs irregular rhythm
    • Look for regularity in the rhythm to decide the counting method.
    • If irregular, determine whether the irregularities are premature beats or pattern-based, as this affects rate estimation.

Frequency vs infrequency and how to describe urgency

  • Frequent vs infrequent premature complexes
    • Infrequency: less than 6\ \text{per minute}
    • Frequent: more than 6\ \text{per minute}
  • Why it matters
    • The more frequent the premature events, the more clinically concerning the rhythm can be.
    • Example framing: If you’ve got 22 premature events per minute, that’s a high-risk scenario; if it’s 3 per minute, it may be less urgent.

Premature contractions: PACs, PJCs, PVCs

  • Premature contractions terminology
    • PAC: Premature Atrial Contraction
    • PJC: Premature Junctional Contraction
    • PVC: Premature Ventricular Contraction (the most common premature event discussed here)
  • Morphology and location cues
    • PVCs: wide and bizarre QRS complexes; not preceded by a P wave and not in the expected place.
    • PACs: premature P waves with a narrow QRS; the P wave morphology is different from sinus P waves and occurs early.
    • PJCs: premature QRS that is usually narrow; P waves may be absent or inverted or occur after the QRS.
  • What happens in the heart when oxygen is low
    • Premature ventricular contractions are often caused by myocardial hypoxia (the bottom of the heart is unhappy with oxygen and tries to pump blood to itself).
  • Naming and color-coded explanations used in teaching
    • PVCs are described as wide and weird; they are not in the normal place.
    • If a premature beat has an upright P wave and occurs in the wrong place, it might be a PAC; if it is not where it should be and lacks a P wave or has an inverted/alt P wave, it might be a PJC or PVC depending on the QRS width and timing.

Rate calculation methods and practical workflow

  • Two primary methods to calculate rate
    • Six-second strip rule: count the number of complexes in a 6-second strip and multiply by 10 to estimate bpm (works best for irregular rhythms for a quick sense).
    • Big-box method (regular rhythm): count the number of large boxes between two consecutive R waves and use the rule of 300 divided by that number. Example: 4 large boxes between R waves → 300/4 = 75\ \text{bpm}.
  • When to apply each method
    • Use the six-second method for irregular rhythms or when unsure about regularity.
    • If rhythm looks regular enough, the “300 rule” with large-box counting can give a quick accurate rate.
  • Premature complexes and rate counting
    • Premature complexes (PACs, PJCs, PVCs) do not count toward the rate calculation when using the regular-rule method; rate should be calculated based on the normal, regular complexes only.
  • Practical example notes from the lecture
    • A strip might show sinus bradycardia at 50 bpm with two PVCs in a 6-second strip; the overall 6-second strip method would consider the regular beats for the rate, while the PVCs are treated as separate events for morphology and risk assessment.
    • In another example, counting four large boxes between R waves gave 75 bpm, and the underlying rhythm was sinus bradycardia with two crackheads (PVCs) that were multifocal, making the rhythm frequent and multifocal.

Unifocal vs multifocal: what the ECG looks like

  • Unifocal: all abnormal beats look the same; originate from one focus.
  • Multifocal: abnormal beats look different from each other; originate from multiple foci.
  • How to decide from the strip
    • If two premature complexes look identical (same morphology), they are unifocal (one focus).
    • If premature complexes differ in morphology, they are multifocal (multiple foci).
  • Practical labeling terminology
    • Single focus: unifocal
    • More than one focus: multifocal
  • The presentation also covers the idea that a pattern may emerge (geminin or Gemini) where alternating normal and abnormal beats form a recognizable pattern (see next section).

Gemini (Geminal) patterns and related terminology

  • Gemini (Geminal strip) concept
    • A rhythm pattern where a good (normal) complex is followed by a weird (premature/altered) complex, then a good one, and so on, creating a repeating good–bad–good–bad pattern.
    • When this pattern is identified, you “marry” the good and the bad to describe the rhythm as Gemini or Geminal.
    • Example language: “Gemini strip: good complex, weird complex, good complex, weird complex …”
  • How to describe Gemini rhythms
    • Start with the underlying rhythm (e.g., sinus rhythm with bradycardia).
    • Then identify the pattern: good–weird, good–weird, etc., and state whether it’s unifocal (same morphology) or multifocal (different morphologies).
    • If the pattern repeats with alternating morphologies, call it Gemini (two-beat pattern) or try/quad for larger groupings (see next section).
  • Extending the concept
    • If you see four-beat repeating patterns (good, weird, good, weird), you’ll end up with a label like quad (quadrigeminy) or higher order patterns as the sequence grows.
  • Throuple and higher-order patterns
    • When three or more morphologies are involved, terms like trigeminy (three-beat pattern) or quadri- (quad, four-beat) are used.
    • A rhythm can become more complex: good–weird–good–weird–good–weird may be trigeminy or quad depending on how many elements are alternated.
  • Run and count concepts within Gemini patterns
    • A rhythm with more than four in a row of premature beats is a run; generally, you only need to label singles, couples, and triples for clinical communication in some teaching contexts.
    • Couples: two premature beats stuck together; if the two look the same and come from the same focus, it’s a unifocal couplet; if they look different, it’s a multifocal couplet.
    • Triplets: three premature beats in a row; stuttering patterns with three consecutive premature beats; if they all look the same it’s unifocal triplet; if not, multifocal triplet (fraternal triplet).
  • Practical takeaway
    • Gemini, trigeminy, quad, triplet, couplet, and run terminology helps communicate the pattern quickly to colleagues and in clinical notes.

Practical approach to describing rhythms (a step-by-step workflow)

  • Step-by-step approach for every rhythm analysis
    • Step 1: Determine the underlying rhythm
    • Identify if sinus (upright P waves, regular PR interval) or ventricular/junctional rhythm (QRS width, P waves absent or abnormal).
    • Step 2: Determine the rate and regularity
    • If all complexes look regular and normal, multiply by 10 from six-second strip or use large-box method (e.g., 4 large boxes between R waves → 75\ \text{bpm}).
    • If irregular, rate calculation should consider the regular complexes only, or use a more robust method (e.g., count in several six-second strips).
    • Step 3: Evaluate P waves and PRI
    • Check for upright P waves with normal PRI in sinus rhythm; check for absent/altered P waves in ventricular or junctional rhythms; altered P waves can occur with PACs or PJCs.
    • Step 4: Assess QRS morphology and width
    • Narrow QRS (< 0.12 s) typically indicates supraventricular origin; wide QRS (> 0.12 s) suggests ventricular origin.
    • Step 5: Evaluate ventricular rhythm morphology
    • If the QRS complexes are wide, compare morphologies across beats to assess uniformity (unifocal vs multifocal).
    • Step 6: Classify premature complexes
    • Identify PACs, PJCs, PVCs based on morphology and timing relative to the normal beats.
    • Note whether premature complexes are unifocal or multifocal, and whether they occur in runs, couplings, trips, or other patterns.
    • Step 7: Look for patterns and higher-order patterns
    • Recognize Gemini (good–weird) patterns; trigeminy (three-beat pattern); quad (four-beat pattern), etc.
    • Step 8: Assess clinical urgency
    • Frequent premature beats or multifocal patterns are more concerning than infrequent, solitary premature beats.
    • Identify dangerous rhythms: Ventricular Tachycardia (VT) and Ventricular Fibrillation (VF) as lethal rhythms; plan immediate response accordingly.
    • Step 9: Consider device-related rhythms
    • Pacemaker rhythms: expect pacer spikes; the rhythm may look chaotic, but the spikes indicate pacing activity.
  • Communication tips for reporting
    • Start with the underlying rhythm, then state whether the premature complexes are frequent or infrequent, followed by morphology (unifocal vs multifocal), then pattern (Gemini, trigeminy, triplets, quads), and finally rate using the appropriate method.
    • In practice, the presenter emphasizes leading with the “oh my god” part (the urgent part) when describing acute findings to prompt timely action.

Specific dangerous rhythms and management concepts

  • Ventricular Tachycardia (VT)
    • VT is a lethal dysrhythmia. It can occur with or without a pulse.
    • With pulse: sometimes perfusing blood but patient is symptomatic (sweating, chest pain, difficulty breathing).
    • Without pulse: immediate danger; defibrillation or synchronized cardioversion depending on presence of pulse and hemodynamic stability.
    • The rhythm is sometimes described as a “tombstone” pattern on the ECG, particularly when the QRS complexes are tall and upright in appearance.
    • Two main types described: “with a pulse” vs “without a pulse.” The non-pulsatile VT is more urgent.
  • Ventricular Fibrillation (VF or V-fib)
    • VF is the disorganized, chaotic rhythm with no effective cardiac output.
    • Coarse VF: large, irregular deflections; fine VF: smaller deflections as tissue dies.
    • Immediate treatment is defibrillation to disrupt the disorganized electrical activity in hopes that a normal rhythm can resume.
    • The teaching emphasizes disorganized electrical activity; the heart quivers and does not pump blood.
  • Asystole
    • Absence of a heartbeat on the tracing.
    • Not shockable in typical initial management (although there are rare exceptions in certain reversible causes).
    • Management focuses on CPR and addressing reversible causes.
  • Defibrillation and resuscitation concepts
    • Defibrillation is described as delivering a large amount of electricity to reset the heart’s electrical activity; the goal is to achieve a return to organized rhythm where a normal rhythm can take over (SA node or another pacemaker focus).
    • The speaker emphasizes that you are disrupting the disorganized electrical activity and not “starting the heart” with the shock itself.
  • Pacemakers
    • Two basic types: demand pacemakers (which respond to the heart’s own rhythm) and external or implanted devices.
    • Paced rhythms may show pacer spikes; even if the ECG tracing looks chaotic, the presence of pacer spikes helps identify pacing activity.
    • If a tracing looks like pacemaker rhythm, the spikes are the key cue; you can still interpret the rhythm by following the pacing activity.

Real-world clinical perspective and exam readiness

  • On-the-job expectations for EKG techs
    • EKG techs are generally expected to interpret a basic EKG, especially lead II readings, and to identify underlying rhythm, rate, regularity, P waves, and QRS morphology.
    • 12-lead EKG interpretation is more advanced; techs should be able to describe lead II findings and the underlying rhythm.
    • The emphasis is on a methodical, rule-based approach rather than purely sight-reading.
  • Practical communication and decision-making
    • In a clinical setting, you should be able to decide when a rhythm requires urgent attention (e.g., frequent multifocal PVCs, VT, VF) vs when it is a stable rhythm that can be monitored.
    • The approach described prioritizes the urgent findings first and then describes the rhythm in a structured way.
  • Final takeaways
    • Start with underlying rhythm, then rate and regularity, then P waves and PRI, then QRS morphology, then premature beats and their pattern (unifocal vs multifocal, Gemini, triplets, quads), and finally the clinical urgency.
    • Recognize common prematures (PACs, PJCs, PVCs) and how to describe them; understand how to describe runs, couples, triplets, quads, and geminal patterns.
    • For lethal rhythms (VT with/without pulse, VF, asystole), know the urgency and the basic treatment principles (defibrillation for VT/VF, CPR and reversible causes for asystole).

Quick reference terms and mnemonics from the lecture

  • Key terms
    • Sinus rhythm: upright P waves, regular rhythm, narrow QRS
    • Ventricular rhythm: wide QRS, no P waves, origin in ventricles
    • Unifocal: all abnormal beats look the same; single focus
    • Multifocal: abnormal beats look different; multiple foci
    • Premature contractions: PAC, PJC, PVC
    • Geminal (Gemini): a repeating pattern of good and weird beats
    • Trigeminy: pattern of three beats (good–weird–good or equivalent)
    • Couplet: two premature beats in a row
    • Triplet: three premature beats in a row
    • Quad: four premature beats in a row
    • Run: more than four premature beats in a row
  • Formulas and thresholds (LaTeX-annotated)
    • Intrinsic ventricular rate: 20-40\ \text{bpm}
    • Frequent vs infrequent premature beats:
    • Rate estimation methods:
    • Six-second strip: (\text{Rate} \approx 10 \times \text{(number of complexes in 6 s)})
    • Large-box method: (\text{Rate} = \dfrac{300}{n}), where (n) is the number of large boxes between two consecutive R waves
  • Real-world application reminders
    • PVCs are wide and irregular; morphology helps determine single vs multiple foci
    • VT and VF require urgent attention; defibrillation is a key treatment for VT/VF in appropriate contexts
    • Pacemaker spikes indicate pacing activity; not all chaotic-looking rhythms are pacemaker-locked