2. Ventricular arrhythmias, diagnosis and therapy

Definition

Ventricular arrhythmias are those which originate from the ventricles. They include the following:

  • Ventricular premature beats
  • Ventricular tachycardia
  • Ventricular fibrillation

Ventricular premature beats

Ventricular premature beats, also called ventricular extrasystoles (VES) are caused by ectopic foci in the ventricles. They are relatively common and rarely cause symptoms. On the ECG they’re characterised by wide QRS and the lack of a preceding P wave.

Asymptomatic persons don’t require treatment. Symptomatic persons and persons with many VES and underlying heart disease should receive antiarrhythmic treatment to prevent sudden cardiac death. Beta blockers and amiodarone can be used.

Ventricular tachycardia

Ventricular tachycardia (VT, or V-tach) is a serious condition which is most commonly a complication of ischaemic heart disease, but it can also occur due to electrolyte disturbances (most importantly hypokalaemia), myocarditis, and prolonged QT. It’s a wide QRS complex tachycardia that’s defined as 3 or more consecutive ventricular beats at a frequency of > 100/min.

We can distinguish two types according to the duration, two types according to the morphology, and two types according to the presence of pulse:

  • Classification by duration
    • Nonsustained ventricular tachycardia (NSVT) – VT lasting < 30 seconds and spontaneously terminating
    • Sustained ventricular tachycardia – VT lasting > 30 seconds
  • Classification by morphology
    • Monomorphic VT – a single arrhythmogenic focus causes all the beats to have the same morphology on ECG
    • Polymorphic VT – multiple arrhythmogenic foci cause all the beats to have different morphology on ECG
      • Torsade de pointes is a special form of polymorphic VT which occurs in patients with prolonged QT interval
  • Classification by presence of pulse
    • Pulseless VT – VT which does not produce a palpable pulse in the patient’s carotids
    • VT with pulse – VT which does produce a palpable pulse

Ventricular tachycardia can cause symptoms like hypotension, dizziness, palpitations, and syncope. Nonsustained VT is often asymptomatic.

Asymptomatic nonsustained VT rarely requires any specific treatment. In acute cases of wide QRS tachycardia, vagal manoeuvres should be tried. These manoeuvres do not treat VT, but they do treat SVTs with BBB, which can also cause wide QRS tachycardia.

Pulseless VT is an emergency which must be handled with advanced life support and defibrillation, as the patient has no cardiac output. Sustained VT causing haemodynamic instability should be defibrillated or synchronised electrically cardioverted. Sustained VT not causing instability can be managed with IV amiodarone or procainamide, with cardioversion as a second option.

In all cases of VT, once the patient has stabilised, they should be evaluated for an underlying cause. VT rarely occurs in healthy hearts, and if VT is the patient’s first cardiological presentation, it’s likely that investigations like echocardiography and angiography will reveal abnormalities.

Beta blockers are important in preventing sudden cardiac death in people who’ve had symptomatic VT. Patients who’ve had symptomatic VT should also be evaluated for an ICD.

Ventricular fibrillation

Ventricular fibrillation (VF or V-fib) is, like pulseless VT, an emergency which must be handled with advanced life support and defibrillation, as the patient has no cardiac output. Like VT, it most commonly occurs in diseases hearts. Sustained VT can quickly develop into ventricular fibrillation, as well. It invariably causes loss of consciousness and death if untreated.


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3. Blocks and conduction disorders, diagnosis and drug treatment

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