■ 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 OFRESULTS
■ Appropriate pacing and CXR indicate proper placement. If the catheter is
within the right ventricle, a left bundle-branch pattern with left axis devia-
tion should be evident in paced beats (see Figure 19.4).While you’re placing a subclavian line your patient becomes agitated,
hypoxic, tachycardic, and hypotensive. CXR shows Westermark sign (focal
oligemia). What’s the diagnosis? Treatment?
Air embolism. Clamp the central line. Reposition the tip of the line 2 cm
below SVC-RA junction and aspirate. Place the patient in left lateral decubitus
position and Trendelenburg. Consider hyperbaric therapy.PROCEDURES AND SKILLS
FIGURE 19.4. Pacing with intermittent capture. “P” indicates paced beats; “A” indicates
pacer artifact without capture.(Reproduced, with permission, from Tintinalli JE, Kelen GD, Stapczynski JS. Tintinalli’s Emer-
gency Medicine: A Comprehensive Study Guide, 6th ed. New York: McGraw-Hill, 2004:136.)