How to treat complete heart block with transcutaneous pacing
Patient with a 3rd degree AV block needs rapid assessment and treatment to prevent deterioration in her clinical status
Article updated August 3, 2017
You are dispatched to the home of a 74-year-old female, who has impaired mobility, to aid in her transfer to your regional hospital. The patient explains that she visited her cardiologist three days ago for a routine check of her hypertension. Stemming from this visit, the cardiologist ordered a Holter monitor test, although the patient did not recall any recent episodes of palpitations, dizziness or chest pain. She dutifully carried out the doctor's orders and returned the Holter machine the next day.
About 45 minutes ago, the cardiologist called her and asked her about the previous 24-hour period and, specifically, the Holter test. Your patient says that she felt the test went fine and that it would prove to be non-diagnostic. The patient says that the cardiologist calmly explained to her that he wanted to carry out some further tests on her as soon as possible.
These are the learning objectives for this EKG Club case:
- Basic: Recognize third-degree AV block
- Intermediate: Determine the difference between stable and unstable presentation
- Advanced: Identify the appropriate treatment(s) for this patient
Patient treatment and transport
Based on the given set of vital signs and level of consciousness, you decide to keep the pacer ready by using combination
(monitor/defibrillator/pacing/cardioversion) pads to monitor the patient. You establish IV access as you provide transport to the patient's medical facility.
No change in the patient's status occurred during transport and the patient is received by the emergency department's team. Shortly after arriving, the emergency physician decides to place an intravenous pacemaker and calls cardiology to continue the admission of this patient for the placement of a permanent, implantable pacemaker.
Treatment of complete heart block
This patient's 12-lead EKG demonstrates a third-degree AV block, also known as complete heart block (CHB) with ventricular escape complexes at the rate of 31 beats per minute.
Rate and rhythm at this level places the patient at risk for a clinically significant diminished cardiac output and decompensation. Definitive treatment for this condition is relatively simple for those equipped with an external pacemaker to increase the ventricular pulse rate.
External pacing to increase ventricular pulse rate
There are three types of pacemakers:
- Implantable (permanent)
The road to a permanent, implanted pacemaker begins with a temporary pacemaker (transcutaneous or transvenous). Transvenous pacemakers require central venous catheter insertion, which involves additional skills and carries additional risks, so it is not taught to prehospital providers.
A transcutaneous pacemaker, on the other hand, is easily attached by placing combo pads, now considered common, on the patient's chest on either an anterior-posterior position or on each hemithorax, similar to defibrillation pads.
The pacing frequency is typically set between 70 and 80 beats per minute and the energy, measured in milliamperes, is gradually increased from zero mA until ventricular capture is achieved.
Transcutaneous pacemakers are known to result in capture threshold tolerance. This can be noted when the TCP is no longer capturing the ventricles and requires the user to increase the energy level in order to maintain capture.
A transcutaneous pacemaker will produce an electrical stimulus to the patient’s skeletal muscles that may be painful for the patient and requires analgesia and sedation. Therefore, when possible before beginning TCP, it is advised to inform the patient about what is occurring and to titrate the analgesic and sedative appropriately. Once TCP is required for a patient, they must be evaluated for a potential transvenous pacemaker insertion or the use of a permanent pacemaker by the physicians.
The oddity of this case is that the patient was clinically stable despite evidence of a low heart rate and a disturbing EKG. The prudent health care provider should assume that deterioration may ensue at any moment and should take that into account when planning interventions and transport decisions.
Based on the clinical history of this patient, it may have been possible to theorize that this patient's arrhythmia did not begin at the time of EMS presentation and, in fact, may have occurred over a long period of time. The EMS crew in this case had a TCP ready, to be applied if necessary. The combination pads were used to monitor, but not to pace.