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🌱 來自: Huppert’s Notes
Wide QRS Complex Tachycardia🚧 施工中
Wide QRS Complex Tachycardia
Ventricular tachycardia (VT)
• Etiology: VT can be due to active ischemia, chronic ischemic heart disease (e.g., scar forms reentrant circuit), cardiomyopathy (e.g., congestive, hypertrophic, arrhythmogenic RV), inherited syndromes, congenital heart disease (e.g., tetralogy of Fallot), idiopathic
• Common artifact: It is common for telemetry artifact to look like VT. Get 12-lead ECG to evaluate.
• Diagnosis of VT:
- Stable or unstable?
• UNSTABLE: If the patient is hypotensive, non-responsive, or has chest pain, assume that it is VT and proceed with DCCV or ACLS
• STABLE: If the patient is stable, you have more time to proceed to the next steps and try to differentiiate VT vs. SVT with aberrancy.
- Does the patient have any risk factors for VT? (e.g., prior MI, prior cardiac surgery, known scars)? If so, it is safest to assume that it is VT.
- Does the patient have a prior ECG with an old LBBB or RBBB? If the patient is stable AND has an old bundle branch block, it is more likely to be SVT with aberrancy, especially if the QRS morphology of their tachycardia looks like their baseline BBB.
- Check for capture or fusion beats: If either of these is present, high positive predictive value for VT.
- Check for A-V dissociation: Clear A-V dissociation confirms VT.
- Check for concordance: Concordant QRS morphology in leads V1–V6 (i.e., all negative or all positive) suggests VT.
- R wave in aVR? NW axis (aka up in aVR) is highly suggestive of VT.
- Check the Brugada criteria. If any of the Brugada criteria are satisfied, it is likely VT. If none are satisfied, it is likely SVT. BUT no perfect criteria, which is why there are so many (e.g., Kindwall, Wellens, Brugada, Miller).
• Types of VT:
- Monomorphic
• ECG: Single QRS morphology
• Etiology: Chronic ischemic heart disease (scar forms reentrant circuit), cardiomyopathy (e.g., congestive, hypertrophic, arrhythmogenic RV), inherited syndromes, congenital heart disease (e.g., tetralogy of Fallot), idiopathic
- Polymorphic
• ECG: QRS morphology varies from beat to beat
• Etiology: Active ischemia (most common cause), long QT (torsades), catecholaminergic
• Torsades de pointes: VT with varying QRS amplitude which occurs in the setting of long QTc (usually >500 ms) especially when bradycardic. Can be congenital or due to acquired causes (e.g., medications, hypokalemia, hypomagnesemia, bradycardia). Treatment: Magnesium 4 g IV, replete K to 4.5 mmol/L, keep HR >100 bpm (e.g., isoproterenol, epi, or pacing), lidocaine, stop QT-prolonging medications, defibrillation if unstable
• Treatment of VT:
- Nonsustained (<30 seconds) or PVCs: Check electrolytes, evaluate for underlying heart disease; use beta blocker if symptomatic.
- Sustained (>30 seconds): IV amiodarone (especially for monomorphic VT), lidocaine (especially for VT due to ischemia). Prepare for synchronized cardioversion. Look for underlying causes such as active ischemia, hypotension, hypo/hyperK, hypoMg.
- Long-term management: ICD for secondary prevention after unstable VT or VT/VF arrest; pacemaker WITH antitachycardic pacing (PM senses VT then paces patient quickly to override the rhythm), antiarrhythmics (Class III e.g., sotalol; amiodarone), ablation.
SVT with aberrancy
• Description: A supraventricular tachycardia (Afib, Aflutter, Atach, orthodromic AVRT, AVNRT), which conducts through the AV node and down a slow conduction system (e.g., baseline RBBB or LBBB) causing the QRS to appear wide.
• Treatment: Adenosine, SVT treatment
Antidromic AVRT
• Description: AVRT that conducts down an accessory pathway and then up through the AV node causing the QRS to appear wide.
• Treatment: Adenosine
SVT with bystander accessory pathway
• Description: An SVT (other than AVRT or AVNRT) occurring in a patient with WPW syndrome, recognized by changing QRS morphologies.
• Treatment: Procainamide, amiodarone
Ventricular fibrillation (Vfib)
• Definition: Multiple foci in the ventricles fire rapidly, which can occur due to ischemia, drugs, rapid Afib with a bystander pathway, short-QT syndrome, Brugada syndrome (which is a Na+ channelopathy; look for pseudo-RBBB with ST elevations in V1–V3 on resting ECG).
• ECG: Irregular, wide QRS (Figure 1.14)
• Treatment: Nonsynchronized defibrillation followed by amiodarone. If not associated with an MI, recurrence rate is 30% so ICD placement is indicated.