What does an EKG tracing show in an adult patient with underlying heart disease presenting with ventricular tachycardia (VT)?

EKG Tracing Features in Ventricular Tachycardia with Underlying Heart Disease

Primary Diagnostic Features

In an adult patient with underlying heart disease presenting with ventricular tachycardia, the EKG tracing characteristically shows a wide QRS complex (>120 ms), AV dissociation with independent P waves, and specific morphological patterns that distinguish VT from supraventricular rhythms. 1, 2

Wide QRS Complex Characteristics

• QRS duration exceeds 120 ms in adults with VT, representing abnormal ventricular depolarization originating below the AV node 1, 2, 3
• QRS morphology differs from the patient's baseline sinus rhythm, a critical distinguishing feature when prior EKGs are available 1, 2
• QRS width typically measures around 140 ms in sustained VT presentations 4
• R-S interval (onset of R wave to nadir of S wave) >100 ms in any precordial lead strongly suggests VT 1, 2

AV Dissociation and Fusion Phenomena

• AV dissociation with ventricular rate faster than atrial rate is pathognomonic of VT, representing the single most specific diagnostic finding 1, 2
• Independent P waves continue unrelated to QRS complexes during the tachycardia, visible as "marching through" the rhythm 1, 2
• Fusion beats (combination of supraventricular and ventricular complexes) strongly indicate VT when present 1, 2
• Capture beats may occasionally appear when a supraventricular impulse transiently captures the ventricles 1

Lead-Specific Morphological Criteria

Precordial Lead Analysis (V1-V6)

• Absence of any R-S complexes in leads V1-V6 implies VT (Brugada criteria) 1
• Positive or negative concordance (all QRS complexes pointing in the same direction across precordial leads) strongly suggests VT 1, 2
• QR complexes indicating myocardial scar are present in approximately 40% of patients with post-MI VT 2

Lead aVR Findings (Vereckei Algorithm)

• Presence of initial R wave in aVR suggests VT 1, 2
• Initial R or Q wave >40 ms in aVR implies VT 1, 2
• Notch on the descending limb at the onset of a predominantly negative QRS in aVR indicates VT 1

Lead II Assessment

• R-wave peak time ≥50 ms in lead II suggests VT 1, 2

Rate and Rhythm Characteristics

• Heart rate typically exceeds 120 beats per minute in sustained VT 3
• Median tachycardia cycle length around 320 ms in emergency presentations 4
• Regular rhythm with minimal R-R interval variation distinguishes monomorphic VT from atrial fibrillation 5
• Polymorphic VT shows continually changing QRS morphology with cycle lengths between 180-600 ms 1

Context-Specific Features in Structural Heart Disease

Ischemic Heart Disease Patterns

• Patients with prior myocardial infarction developing wide QRS tachycardia are highly likely to have VT rather than SVT with aberrancy 1, 2
• Ischemic heart disease is the underlying disorder in 76% of VT presentations in the emergency setting 4
• Acute myocardial infarction is present in 21% of stable VT patients and 65% of unstable VT patients 4

Cardiomyopathy-Related Features

• Bundle-branch reentrant tachycardia typically shows LBBB morphology in patients with cardiomyopathy 1
• Scar-related VT demonstrates specific substrate patterns on electroanatomical mapping 1

Critical Diagnostic Pitfalls to Avoid

• Pre-existing bundle branch block can confound diagnosis—compare the tachycardia QRS morphology to baseline sinus rhythm QRS 1, 2
• Antiarrhythmic medications can widen QRS complexes and create diagnostic confusion 1, 2
• Electrolyte abnormalities or metabolic disorders can mimic VT with wide QRS complexes 1, 2
• Hemodynamic stability does not rule out VT—stable vital signs cannot distinguish SVT from VT 5
• When diagnosis is uncertain with wide QRS tachycardia, always treat as VT given the higher mortality risk 2, 5

Additional EKG Patterns

Monomorphic vs Polymorphic Distinction

• Monomorphic VT shows consistent QRS morphology beat-to-beat with regular cycle length 1
• Polymorphic VT demonstrates continually changing QRS morphology, often associated with acute ischemia or channelopathies 1
• Five of seven patients with polymorphic VT pattern were hemodynamically unstable in emergency presentations 4

Specialized VT Patterns

• Bidirectional VT shows beat-to-beat alternans in QRS frontal plane axis, often associated with digitalis toxicity 1
• Ventricular flutter appears as regular rhythm approximately 300 bpm with no isoelectric interval between QRS complexes 1
• RVOT VT typically shows LBBB morphology with inferior axis in patients without structural heart disease 6

Diagnostic Workflow Integration

• A 12-lead EKG during tachycardia is the first diagnostic test that should be obtained in any stable wide QRS complex tachycardia 1
• A 12-lead EKG in sinus rhythm should be obtained to look for evidence of heart disease and compare QRS morphology 1, 2
• Similar morphology between PVCs during sinus rhythm and the tachyarrhythmia strongly suggests VT 2