This article appeared in the March 1988 issue of Jems Magazine.
Kate Dernocoeur has sometimes used the pseudonym Syd Canan
Paramedics were called to the home of an 80-year-old female who reportedly had fallen down a flight of stairs. On arrival, they found her barely conscious, with a large hematoma on her left parietal scalp and with an apparently fractured left hip. She was at the bottom of 15 heavily carpeted stairs.
Vital Signs: Pulse: 100 and regular, Blood Pressure: 140/100, Respirations: 10 and shallow
The paramedics immobilized the patient's spine on a scoop stretcher with a Philadelphia collar, sandbags and tape. She was nasotracheally intubated without difficulty and was hyperventilated with 100 percent oxygen. An intravenous line of normal saline was established and run TKO.
After transport to the ambulance, her EKG was taken. The paramedics could not identify atrial activity in Leads I, II, III, MCL1, or MCL6, so they placed the patient in an S5 lead, shown in Figure 1.
The patient was transported red lights qnd siren to the closest hospital (at a time predating trauma center designation). During transport, the paramedic driving interviewed the patient's husband, who was riding along in the front compartment. According to the husband, the patient had a medical history of hypertension and arthritis and took medication for both, but he could not remember what the medications were.
The paramedic asked the husband to describe in as much detail as possible what had happened and the husband related the following: "We were walking down the stairs; she was in front of me, and she just collapsed and fell down almost from the top, landing right on her head. She didn't trip, catch a heel, or slip on anything. It's almost as if she fainted."
At the emergency department, the history of the event was relayed in detail to the emergency department staff, along with the rest of the patient report. Based on the history and the patient's electrocardiogram, the emergency department physician placed a transvenous pacemaker prior to sending the patient to the operating room to have her subdural hematoma evacuated.
The next day, as the patient recovered in the neurotrauma intensive care unit, she progressed to complete heart block and the artificial pacemaker took over pacing her heart. She suffered no period of inadequate perfusion.
Case Discussion
The initial electrocardiogram taken by the paramedics (which has since been lost) revealed a choppy baseline that looked like atrial fibrillation. The paramedic realized, however, that atrial fibrillation also has an erratically irregular ventricular response, which was not the case here. The QRS complexes occurred regularly, thus motivating him to search for atrial activity by using the lead S5.
S5 is a lead to use when you are unable to find atrial activity in any other lead. To properly place this lead, the positive electrode is placed in the fifth intercostal space just to the right of the sternum; the negative electrode is placed over the manubrium, just beneath the suprasternal notch. One way to accomplish this is to:
leave the lead selector in the Lead Ill position,
put the left-leg lead wire on the electrode at the fifth intercostal space, and
put the left-arm lead wire on the electrode on the manubrium.
This places the electrodes on either side of the atria, and, short of putting an electrode directly on the heart's surface or in the esophagus this is most likely to show atrial activity if it's present.
There is one factor which could dissuade you from believing the waves seen in S5 are P waves. You may have thought those were T-waves and not P-waves. However, if you use Marriot's principle of "who's married to whom" or, for this era, ' 'who's living with whom," the dilemma is easily answered. T-waves should be a constant distance from the preceding QRS complex. If you try to make this happen in this EKG, you find variable Q-"T” intervals. On the other hand, if you measure them as P-waves, you find they are constantly related to 'married to") the subsequent QRS. This patient's electrocardiogram exhibits a sinus tachycardia with a prolonged P-R interval at 0.36 seconds.
Pertinent Points
1. The patient's primary problem on initial presentation to the paramedics was one of major trauma. Consequently, spinal immobilization, airway management, and transport took priority over EKG evaluation. These paramedics clearly had their priorities in order. It is not appropriate to take time on a trauma scene taking an EKG; this is something which can be done en route to the hospital when there's time.
2. Normally, a prolonged P-R interval by itself is not terribly worrisome. However, a history of syncopal episode in combination with any evidence of impaired A-V conduction (such as this woman's prolonged P-R interval) may be a predictor of development of complete heart block.
As always, history of the event played a pivotal role in her care. Can you imagine an 80-year-old post-neurosurgical patient in critical condition developing complete heart block and having a period of inadequate perfusion for lack of an artificial pacemaker? The results could have certainly been disastrous. As turned out, she was discharged home with a mild impairment from neurological deficit, and with a permanent pacemaker.
3. You will notice we have referred to the prolonged P-R interval as just that: "prolonged P-R interval." It has not been termed "first degree A-V block.' 'To quote Dr. Marriot: 'Degrees', as we use the term, do not necessarily represent grades of severity as they presumably should." While in other areas of medicine, degrees are useful in describing severity of disease, predicting progression of disease, and directing treatment, classification of A-V blocks into degrees has generated false assumptions about the severity of cardiac disease and its treatment. To describe this woman's EKG as "first degree block" hints at a minor problem, which hers was not! Better to describe exactly what you see than to code it with numbers.