Tachycardia, Ventricular (VT)

Key Features

Essentials of Diagnosis

• Fast, wide QRS complex on ECG

• Associated with ischemic heart disease, particularly in older patients

• In the absence of reversible cause, implantable cardioverter defibrillator (ICD) is recommended if meaningful life expectancy is longer than 1 year

General Considerations

• Defined as three or more consecutive ventricular premature beats and classified as either

  • Nonsustained: lasting < 30 seconds and terminating spontaneously or

  • Sustained: a heart rate > 100 beats/min

• VT is a frequent complication of acute myocardial infarction and dilated cardiomyopathy

  • May occur in chronic coronary disease, hypertrophic cardiomyopathy, myocarditis, and in most other forms of myocardial disease

  • Can also be a consequence of atypical forms of cardiomyopathies, such as arrhythmogenic right ventricular cardiomyopathy

  • However, idiopathic VT can also occur in patients with structurally normal hearts

• Accelerated idioventricular rhythm

  • A regular wide complex rhythm with a rate of 60–120 beats/min, usually with a gradual onset

  • Occurs commonly in acute infarction and following reperfusion with thrombolytic medications

• Torsades de pointes

  • A form of VT in which QRS morphology twists around the baseline

  • May occur in the setting of severe hypokalemia, hypomagnesemia, or after administration of a medication that prolongs the QT interval

Clinical Findings

• Palpitations

• Dyspnea

• Lightheadedness

• May be asymptomatic on rare occasion

• Patients with underlying cardiac disease or other severe comorbidities can present with syncope or cardiac arrest

• Episodes may be triggered by exercise or emotional stress

Diagnosis

Laboratory Findings

• Comprehensive blood laboratory work should be performed as VT can occur in the setting of hypokalemia and hypomagnesemia

• Cardiac markers may be elevated when VT presents in the setting of acute myocardial infarction or as a consequence of underlying coronary artery disease and demand ischemia

Diagnostic Studies

• In patients with sustained, hemodynamically tolerated VT, a 12-lead ECG during tachycardia should be obtained

• Cardiac evaluation with echocardiography or cardiac MRI, ambulatory ECG monitoring and exercise testing may be warranted depending on the clinical situation

• In survivors of cardiac arrest or those with life-threatening ventricular arrhythmia, invasive coronary angiography is recommended to establish or exclude the presence of significant coronary artery disease

• Invasive electrophysiology (EP) study

  • No general role in patients with sustained VT who otherwise meet criteria for implantable cardioverter defibrillator (ICD)

  • May provide important information in

    • Patients with structural heart disease and syncope of unknown cause

    • Situations in which the mechanism of wide complex tachycardia is uncertain

Differentiation of Aberrantly Conducted Supraventricular Beats From Ventricular Beats

• Distinguishing VT from SVT with aberrant conduction on 12-lead ECG is important because of the differing prognostic and therapeutic implications of each type

• Ventricular origin

  • AV dissociation

  • QRS duration exceeding 0.14 second

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