Makindo Medical Notes

Related Subjects: |ECG-QT interval |Brugada Syndrome |Long QT syndrome (LQTS) Acquired |Long QT syndrome (LQTS) Congenital |Torsades de Pointes |Wolff-Parkinson White syndrome (WPW) |Supraventricular Tachycardia (SVT) |Atrial Flutter |Atrial Fibrillation |Ventricular Tachycardia |Ventricular Fibrillation |Resuscitation - Adult Tachycardia Algorithm |Resuscitation - Advanced Life Support

Ventricular fibrillation is a shockable rhythm seen n cardiac arrest and requires electrical countershock within three minutes to change this life-threatening rhythm to normal heartbeats <

About

• Causes Cardiac Arrest and Death if untreated
• Seen in 75% of cardiac arrests
• First described in Ebers Papyrus

Aetiology

• Increased automaticity and re-entrant pathways
• Loss of ventricular systole
• Cardiac output drops and death ensues
• May follow VT

Causes

• IHD/Acute coronary syndrome
• Electrocution, Drug toxicity e.g. TCA overdose
• Electrolyte abnormalities
• Long QT syndromes
• Brugada syndrome
• Valvular heart disease e.g severe aortic stenosis
• Idiopathic ventricular tachycardia
• Cardiomyopathy
  • Dilated, hypertrophic
  • Arrhythmogenic right ventricular dysplasia [ARVD]
• Post cardiac surgery
• Wolff Parkinson White syndrome
• Severe electrolyte disturbance

Clinical

• Sudden loss of responsiveness
• Absence of normal breathing
• Absence of a palpable pulse

Differentials

• Asystole - Get ECG monitoring
• Coma - pulse and breathing should be present
• Agonal rhythm
• Bradycardia/Complete heart block - pace !

Investigations

• FBC, U&E, ABG, Troponin
• Echocardiogram
• Coronary angiography +/- PCI
• 12 lead and ECG monitoring
• Cardiac MRI

Management

• CPR: to support circulation - see ACLS
• Defibrillation: quicker the better. See ACLS
• Antiarrhythmics: See ACLS
• Treat cause e.g. electrolytes, drug toxicity, STEMI (PCI/Thrombolysis)

Prevention

• Acute Management: Resuscitation - Advanced Life Support
• Treat potential underlying causes. VF in the first 24 hrs of MI is usually a good prognosis depending on LV function. Late VF has a worse prognosis and needs consideration for ICD.
• Implantable defibrillator (ICD) in subgroup with high risk of recurrence.
• Indications for ICD
  • Patients with left ventricular dysfunction due to prior myocardial infarction who are at least 40 days post-MI with LVEF <30-40%, are NYHA class II or III and are receiving chronic optimal medical therapy and with life expectancy > 1 year. IA[1] LV dysfunction due to prior MI, presenting with haemodynamically unstable sustained VT.
  • Patients with non-ischaemic dilated cardiomyopathy (NI DCM) with LV dysfunction who have sustained VT or VF.
  • INI DCM LVEF<30-35%. NYHA II-III. Chronic medical therapy. Life expectancy > 1 year.
  • Hypertrophic cardiomyopathy with sustained VT or VF.
  • Arrhythmogenic right ventricular cardiomyopathy with documented sustained VT or VF. OMT, LE>1y.
  • Sustained VT, haemodynamically unstable VT, VT with syncope, or VF. LVEF< 40%.
  • LQTS with previous cardiac arrest
  • Brugada syndrome with previous cardiac arrest.
  • CPVT with previous cardiac arrest.
  • An ICD is recommended in a patient with heart failure with a ventricular arrhythmia causing haemodynamic instability. LE>1y.

References

Images online

• Images available online