TransVenous Cardiac Pacing


 INDICATIONS 
■ Bradycardias: Sick sinus syndrome, second- and third-degree heart block, atrial fibrillation with symptomatic slow ventricular response, pacemaker malfunction
■ Tachycardias: Supraventricular dysrhythmias, ventricular dysrhythmias
 
 CONTRAINDICATIONS 
■ Bradycardic, hypothermic patients should be rewarmed first, then paced if condition does not improve.
 
  TECHNIQUE
  • Pacemakers can be placed through brachial, subclavian, femoral, or internal jugular veins.
  • Patient should be connected to an ECG machine and pacemaker to record chest V lead. The distal terminal of pacing catheter (negative or "-" lead) must be connected to the V lead of the ECG machine to be used as an intracardiac exploring electrode
  • Introducer sheath is passed over the guidewire, then pacing wire is inserted about 10-12 cm into selected vein. If a balloon-tipped catheter is used, the balloon is inflated after the catheter enters the SVC.
  • Lidocaine may be needed to desensitize the myocardium from catheter induced ectopy.
  • The ECG recorded from the electrode tip localizes the position of the tip of the pacing electrode. The ECG complex varies depending on which chamber is entered, with negative forces seen when the catheter tip is above the atrium and diminished amplitude seen if the catheter tip enters the IVC or the pulmonary artery.
  • Once ventricular endocardial contact is made, the catheter is disconnected from the ECG machine and connected to the pacing generator. Set to a rate of 80 bpm, or 10 bpm faster than underlying ventricular rhythm. If capture does not occur, the pacer must be repositioned.
  • Testing threshold (the minimum current necessary to obtain capture) is ideally < 1.0 mA and usually between 0.3 and 0.7 mA. Set to 5 mA and reduce until capture is lost; this threshold amperage is increased by 2.5 times to ensure consistent capture (usually between 2 and 3 mA).
  • Introducer sheath is then removed and catheter secured to the skin. CXR and ECG are obtained for evaluation of placement/capture.
 
 COMPLICATIONS 
■ Inconsistent pacing, infection, pneumothorax, arterial puncture, arrhythmias, perforations, pulmonary embolism, bleeding, DVT
■ In general, transvenous pacemakers fire automatically at a controllable rate. They do not have an atrial lead and do not have a sensing component, so they do not suffer from the problems of oversensing or undersensing.
 
 INTERPRETATION OF RESULTS 
■ Appropriate pacing and CXR indicate proper placement. If the catheter is within the right ventricle, a left bundle-branch pattern with left axis deviation should be evident in paced beats.