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2025 PACUPrep BCCCP Preparatory Course Ventricular Arrhythmias and Sudden Cardiac Death Prevention ECG Patterns and Stability Assessment in Ventricular Tachycardia

Lesson 14, Topic 2

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ECG Patterns and Stability Assessment in Ventricular Tachycardia

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Ventricular Tachycardia: Diagnostic Evaluation and Risk Stratification

Learning Objective

Apply diagnostic and classification criteria to evaluate and risk-stratify patients with ventricular arrhythmias and sudden cardiac death (SCD) risk.

1. Introduction and Scope

Ventricular tachycardia (VT) is a wide-complex tachycardia originating below the His-Purkinje system. Early, accurate differentiation of VT subtypes and stability status drives both emergent interventions and long-term SCD prevention.

VT classification: monomorphic vs. polymorphic (includes Torsades de Pointes)
Hemodynamic stability guides urgency: stable vs. unstable VT
Pharmacist role: verify ECG measurements, interpret risk tools, coordinate multidisciplinary care

Key Pearl

Structured risk stratification bridges acute management and chronic SCD prevention.

2. Clinical Manifestations and Hemodynamic Assessment

Presentation ranges from benign palpitations to cardiac arrest. Assess symptoms and perfusion markers rapidly to distinguish stable from unstable VT.

A. Signs and Symptoms

Palpitations, chest discomfort, dyspnea—suggest preserved perfusion
Presyncope/syncope—transient cerebral hypoperfusion (often SBP <90 mm Hg)
Cardiac arrest—pulseless VT/VF

B. Hemodynamic Parameters

Blood pressure: systolic <90 mm Hg indicates hypotension
Mental status: agitation, confusion, or unresponsiveness
Skin perfusion: cool, mottled extremities
Urine output: <0.5 mL/kg/hr signals end-organ hypoperfusion
Laboratory adjuncts: lactate elevation, troponin rise

C. Stability Classification

Unstable VT: hypotension, altered mental status, shock, ongoing ischemia, or cardiac arrest—requires immediate cardioversion/defibrillation
Stable VT: preserved perfusion, minimal symptoms—allows time for diagnostic evaluation and pharmacotherapy

Clinical Pearl

Reassess stability every 2–5 minutes; sedated or ventilated patients may mask decompensation.

3. ECG Interpretation in Ventricular Tachycardia

ECG criteria distinguish VT from supraventricular tachycardia with aberrancy and subtype of VT, guiding treatment choices.

ECG Characteristics of Ventricular Tachycardia Subtypes
Feature	Monomorphic VT	Polymorphic VT	Torsades de Pointes (TdP)
Rhythm	Regular	Irregular	Irregular, cyclic QRS axis change
QRS Duration	>120 ms (typically >140-160 ms)	>120 ms, variable	>120 ms, variable
QRS Morphology	Uniform, consistent beat-to-beat	Beat-to-beat variability in shape/axis	“Twisting of the points” around baseline
AV Relationship	AV dissociation common; fusion/capture beats	AV dissociation usually present	AV dissociation usually present
Ventricular Rate	Usually 100-250 bpm	Often >200 bpm, can be very rapid	Typically 150-250 bpm
QT Interval (Baseline)	Variable, may be normal or prolonged	Often normal; prolonged in specific channelopathies	Markedly prolonged (QTc >500 ms)
Common Triggers/Etiologies	Structural heart disease (scar, ischemia), channelopathies	Acute ischemia, electrolyte imbalance (K+, Mg++), channelopathies (e.g., Brugada, CPVT)	Drug-induced QT prolongation, hypokalemia, hypomagnesemia, congenital Long QT Syndromes

A. Monomorphic VT

Regular rhythm; QRS duration >120 ms
Uniform QRS morphology
AV dissociation, fusion beats, capture beats

B. Polymorphic VT

Irregular rhythm; beat-to-beat variability in QRS morphology and axis
Ventricular rate often >200 bpm
Common triggers: acute ischemia, electrolyte disturbances, channelopathies

C. Torsades de Pointes (TdP)

Subtype of polymorphic VT with cyclic “twisting” of QRS axis around the baseline
Predisposed by QTc >500 ms
Etiologies: drug-induced QT prolongation, hypokalemia, hypomagnesemia, congenital long QT syndromes

D. QTc Measurement Techniques

Bazett formula (QT/√RR) – overcorrects at high heart rates
Fridericia formula (QT/RR^1/3) – preferred in tachycardia
Manual measurement: use lead II or V5–V6; average 3–5 beats

Key Pearl

Always confirm automated QTc manually when QRS >120 ms or baseline abnormalities exist.

4. Risk Stratification Tools for SCD Prevention

Beyond acute classification, integrate imaging and electrophysiology to predict long-term risk and guide ICD decisions.

A. Left Ventricular Ejection Fraction (LVEF)

Echocardiography: widely available, rapid
Cardiac MRI: superior spatial resolution, scar characterization
Guideline threshold: LVEF ≤35% for primary prevention ICD

B. Electrophysiology Study (EPS)

Programmed stimulation to assess inducibility of sustained VT/VF
Positive inducibility correlates with higher SCD risk
Best predictive value in ischemic cardiomyopathy

C. Cardiac MRI Scar Quantification

Late gadolinium enhancement (LGE) identifies myocardial fibrosis
Scar burden and distribution predict arrhythmic events independent of LVEF

D. Integrative Risk Models

MADIT and MUSTT scores combine LVEF, EPS results, scar metrics
Emerging multimodal algorithms refine risk beyond single parameters

Clinical Pearl

In patients with borderline LVEF (36–40%), MRI scar assessment can tip the balance toward ICD implantation.

5. Clinical Decision-Making Algorithms

A stepwise pathway streamlines from presentation to risk-based intervention.

Patient Presentation

Patient with Ventricular Arrhythmia

Step 1: Hemodynamic Assessment

Assess hemodynamic status (stable vs. unstable)

Unstable VT Pathway

Requires immediate intervention.

Step 3: Immediate Synchronized Cardioversion / Defibrillation

Stable VT Pathway

Allows time for diagnostic evaluation.

Step 2: ECG Interpretation

Obtain 12-Lead ECG; Differentiate VT Subtype (Monomorphic/Polymorphic/TdP)

Step 4: Stable VT Management

Correct Reversible Causes, Obtain Imaging (Echo/MRI), Consider Electrophysiology Study (EPS)

Step 5: Long-Term Risk Stratification

Integrate LVEF, Scar Burden, EPS into Risk Model for ICD/Ablation Decisions

Step 6: Multidisciplinary Review

Coordinate Pharmacist Review: Drug Interactions, QTc, Electrolytes, Device Programming Adjuncts

Figure 1: Clinical Decision-Making Algorithm for Ventricular Tachycardia. This pathway highlights initial stability assessment, ECG-based subtyping, and subsequent steps for acute management and long-term risk stratification.

Assess hemodynamic status (stable vs. unstable)
Obtain 12-lead ECG; differentiate VT subtype (mono vs. polymorphic vs. TdP)
For unstable VT: synchronized cardioversion or unsynchronized defibrillation
For stable VT: correct reversible causes, obtain imaging (echo/MRI) and consider EPS
Integrate LVEF, scar burden, and EPS into risk model to guide ICD and ablation decisions
Coordinate pharmacist review: drug-induced QT prolongation, electrolyte repletion, device programming

Key Pearl

Algorithmic pathways must be individualized to patient comorbidities and evolving evidence.

6. Pitfalls, Pearls, and Controversies

Common errors include misclassifying wide-complex tachycardias and overreliance on LVEF alone.

Mimics

SVT with aberrancy vs. VT – use AV dissociation, specific QRS morphology criteria (e.g., Brugada, Vereckei), and capture/fusion beats to distinguish. When in doubt, treat as VT, especially in patients with structural heart disease.

LVEF Cutoff Debates

Nonischemic cardiomyopathy patients may benefit from ICDs at higher LVEF thresholds (e.g., >35%) if other risk factors like significant myocardial scar on CMR or inducible VT on EPS are present. Current guidelines are evolving in this area.

QTc Variability

The choice of QTc correction formula (Bazett, Fridericia, Hodges, etc.) remains controversial, especially in extremes of heart rate or in the presence of wide QRS complexes. Fridericia is generally preferred for tachycardia, but manual verification and clinical context are key.

Clinical Pearl

A significant proportion of SCD occurs in patients with preserved LVEF—novel risk markers (e.g., CMR scar, genetic testing, autonomic markers) are needed and are areas of active research.

References

Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death. J Am Coll Cardiol. 2018;72(14):e91-e220.
Zeppenfeld K, Tfelt-Hansen J, de Riva M, et al. 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Eur Heart J. 2022;43(40):3997-4126.
Brugada P, Brugada J, Mont L, Smeets J, Andries EW. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation. 1991;83(5):1649-1659.
Vereckei A, Duray G, Szénási G, Altemose GT, Miller JM. Application of a new algorithm in the differential diagnosis of wide QRS complex tachycardia. Eur Heart J. 2007;28(5):589-600.
Drew BJ, Ackerman MJ, Funk M, et al. Prevention of Torsade de Pointes in Hospital Settings: A Scientific Statement From the American Heart Association and the American College of Cardiology Foundation. Circulation. 2010;121(8):1047-1060.
Di Marco A, Brownstein JS, Cadrin-Tourigny J, et al. Left Ventricular Ejection Fraction and Long-Term Outcomes in Patients With Nonischemic Cardiomyopathy. J Am Coll Cardiol. 2020;75(3):267-278.

2025 PACUPrep BCCCP Preparatory Course

Pulmonary

Participants 432

ECG Patterns and Stability Assessment in Ventricular Tachycardia

Ventricular Tachycardia: Diagnostic Evaluation and Risk Stratification

Learning Objective

1. Introduction and Scope

2. Clinical Manifestations and Hemodynamic Assessment

A. Signs and Symptoms

B. Hemodynamic Parameters

C. Stability Classification

3. ECG Interpretation in Ventricular Tachycardia

A. Monomorphic VT

B. Polymorphic VT

C. Torsades de Pointes (TdP)

D. QTc Measurement Techniques

4. Risk Stratification Tools for SCD Prevention

A. Left Ventricular Ejection Fraction (LVEF)

B. Electrophysiology Study (EPS)

C. Cardiac MRI Scar Quantification

D. Integrative Risk Models

5. Clinical Decision-Making Algorithms

Clinical Decision-Making Algorithm for Ventricular Tachycardia

Patient Presentation

Step 1: Hemodynamic Assessment

Unstable VT Pathway

Stable VT Pathway

Step 6: Multidisciplinary Review

6. Pitfalls, Pearls, and Controversies

Mimics

References