From the Guidelines
To accurately diagnose ventricular tachycardia (VT) mimics out of hospital, prioritize assessing hemodynamic stability and examining the 12-lead ECG for specific features such as wide QRS complexes, AV dissociation, and fusion beats, and when in doubt, treat as VT due to the higher risk of misdiagnosing VT as SVT. When evaluating a patient with a wide QRS-complex tachycardia, consider the configurational characteristics of the QRS complex during tachycardia, as outlined in the acc/aha/esc guidelines 1. Leads V1 and V6 are particularly helpful in differentiating VT from supraventricular tachycardia (SVT). An RS interval longer than 100 ms in any precordial lead is highly suggestive of VT, and a QRS pattern with negative concordance in the precordial leads is diagnostic for VT. Some key points to consider when differentiating VT from SVT include:
- The presence of ventricular fusion beats, which indicates a ventricular origin of the tachycardia 1
- The width and morphological criteria of the QRS complex, although these can be less specific in patients taking certain antiarrhythmic agents or with hyperkalemia or severe heart failure 1
- Patient history, such as previous myocardial infarction, which can increase the likelihood of VT 1
- Response to vagal maneuvers, as SVT may respond while VT typically does not 1 Given the potential risks and consequences of misdiagnosis, it is crucial to err on the side of caution and treat as VT when uncertain, especially in patients with structural heart disease or previous cardiac events. The most effective and rapid means of terminating any hemodynamically unstable narrow or wide QRS-complex tachycardia is DC cardioversion, as recommended in the guidelines 1.
From the Research
VT Mimics
VT mimics are conditions that present with similar symptoms to ventricular tachycardia (VT) but have different underlying causes. Accurate diagnosis of VT is crucial to provide appropriate treatment and management.
- Supraventricular arrhythmias can mimic VT on electrocardiographic (ECG) data, making diagnosis challenging 2.
- Wide-complex tachycardia (WCT) on ECG can be helpful in diagnosing VT, but distinguishing between VT and supraventricular arrhythmias can be difficult 2.
Diagnosis of VT
The diagnosis of VT is usually made based on electrocardiographic data, most commonly 12-lead echocardiography (ECG), as well as supportive cardiac telemetric monitoring 2.
- ECG features of WCT can be helpful in diagnosing VT, but the diagnosis frequently needs to be made rapidly in the acute setting 2.
- Adenosine termination of VT is thought to be consistent with a diagnosis of triggered activity, and its specificity for identifying VT due to triggered activity is 100% (95% CI, 0.89-1.0) 3.
Management of VT
Intravenous procainamide and amiodarone are drugs of choice for well-tolerated ventricular tachycardia, but the choice between them is unclear 4, 5.
- Procainamide therapy was associated with less major cardiac adverse events and a higher proportion of tachycardia termination within 40 min compared to amiodarone 5.
- Adenosine can be used to diagnose and treat VT due to triggered activity, but it is not effective in terminating reentrant VT 3.
Out-of-Hospital Diagnosis and Management
Out-of-hospital diagnosis and management of VT can be challenging due to limited access to diagnostic tools and specialist services.
- Accurate diagnosis of VT is crucial to provide appropriate treatment and management, and ECG features of WCT can be helpful in diagnosing VT 2.
- Adenosine can be used to diagnose and treat VT due to triggered activity, but its use in out-of-hospital settings requires careful consideration of the patient's clinical presentation and ECG findings 3.