c_pvc

premature ventricular contractions (PVCs) and bigeminy

introduction

  • a premature ventricular contraction or ventricular ectopic beat is a cardiac contraction that is generally premature or occurs before the expected sinus QRS complex and arises out of the ventricular tissue.
  • when a PVC follows every atrial beat, it is called bigeminy
  • when a PVC occurs every 3rd beat, it is called trigeminy
  • when 2 PVCs occur in a row, they are called a couplet, when 3 or more occur in a row, then it is called a salvo
  • PVCs and bigeminy may be a sign that all is not well with the heart and the patient is at risk of a ventricular fibrillation (VF) when they occur in the setting of acute myocardial ischaemia, hypoxia, prolonged QTc, drug overdoses or metabolic disturbances such as hypokalaemia
    • when the PVCs occur near the peak of the T wave of the preceding beat,these beats predispose the patient to ventricular tachycardia or fibrillation. This R-on-T pattern is often seen in patients with acute myocardial infarction or long Q-T intervals. In the latter case, the triggered arrhythmia would be torsade.
    • couplets, salvos or multifocal PVCs also suggest a higher risk
  • on the other hand, in patients with no evidence of the above, PVCs and bigeminy are usually regarded as benign and not treated other than to advise avoidance of stimulants, manage any underlying hypertension, and if symptomatic consider a beta adrenergic blockers
    • recently however, evidence suggests that some patients with frequent ventricular ectopy may be at risk of developing dilated cardiomyopathy and that ablation of the ectopic focus appears to reverse this cardiomyopathy1)

ECG criteria

  • the QRS complex is wide and often premature with increased amplitude and of a bizarre shape.
  • the QRS width is 0.12 second or wider.
  • the T wave is of opposite polarity to QRS complex.
  • there is no related P wave (unless there is retrograde conduction back through the AV node, which causes the P wave to occur in or after the QRS complex).
  • usually the PVC is followed by a fully compensated pause.
  • they may be unifocal (all look the same) or multifocal

Lown grading system

grade feature
grade 0 no PVCs
grade 1 occasional PVCs (<30/hr)
grade 2 frequent PVCs (>30/hr) eg. bigeminy
grade 3 multiform
grade 4 repetitive (couplets, salvos)
grade 5 R on T PVCs

Mx of frequent PVCs or bigeminy

  • search for a treatable underlying cause:
  • Ensure appropriate or accessible intravenous cannula or drug line.
  • In general, the treatment is to treat the cause and anti-arrhythmic agents should be avoided although in the setting of acute coronary syndrome or if they become symptomatic, beta adrenergic blockers may be considered if haemodynamically stable.
  • lignocaine has fallen out of favour but may be considered if either:
    • symptomatic, complex ectopy in a patient having an MI
    • symptomatic ectopy in patient with prolonged QTc as most other agents such as amiodarone tend to further lengthen the QTc.
  • amiodarone may be considered if ectopy is high risk and the patient is haemodynamically compromised and there is normal QTc.
  • patients with low grade ectopy (including bigeminy) with no underlying cardiac, drug or metabolic cause on non-invasive investigations can usually be managed with reassurance 2) and outpatient follow up by local doctor or perhaps cardiology if it is persistent and frequent as catheter ablation therapy may be indicated in some patients.
  • in patients with chronic underlying cardiac disease, left ventricular dysfunction has a stronger association with increased mortality rate than do PVCs. Many now believe that PVCs reflect the severity of heart disease rather than contribute to arrhythmogenesis 3)

Beware of premature ventricular contractions in slow rhythms; they may be an escape focus. Do NOT give lignocaine in this scenario.

c_pvc.txt · Last modified: 2011/12/16 01:09 by gary