This is Part 2 of the conclusion to 15 year old male CC: fall from vehicle. Be sure to read Part 1 of the conclusion to 15 year old male CC: fall from vehicle to catch yourself up!
Before we find out the answer, let's recap the specifics:
- 15 year old male thrown from the bed of a pickup truck potentially at 45 mph
- Unremarkable findings aside from bruising to lower extremities
- No apparent chest trauma
- Asymptomatic patient
- More P-waves than QRS complexes on the 3-lead and 12-lead
- Unremarkable history
As many of our readers pointed out, there exists some high degree AV block, whether it is a 2:1 AVB or a 3rd Degree AVB there was some disagreement.
The paramedics involved in this case had a similar disagreement and the ED staff did as well. Ultimately, a diagnosis of AV dissociation with an AVB of at least 2nd Degree was made and the patient was referred to a pediatric cardiologist.
Going back to the strips, some degree of AV dissociation is clear, and I've provided the following highlighting to one of the 3-leads:
The question then remains, what was the cause of the AV nodal disturbances? Many readers pointed out some very good possibilities, which I'll list below:
- Traumatic etiology, likely myocardial contusion
- Lyme disease from a recent tick bite
- Congenital AV nodal abnormality
Exploring a traumatic etiology we have to reconcile our patient assessment with the mechanism of injury. Our findings are not suggestive of a traumatic cause. A pediatric patient with a new onset heart block secondary to trauma is not likely to be asymptomatic.
A review of the literature reveals multiple case studies of traumatic causes of heart block, however, every single patient had physical exam findings suggestive of myocardial contusion. I believe we can confidently place a traumatic etiology low on the list of probable causes.
A few readers pointed out Lyme disease, which is a common cause of AV nodal disturbances in otherwise healthy individuals. The carriers of this are Deer Ticks infected with the bacteria Borrelia burgdorferi with an overall incidence of 6 in 100,000 in the US. Findings include a bullseye rash, known as erythema migrans, arthritis, AV nodal disturbances, and a multitude of neurologic findings.
Given no rash upon physical examination and without clear evidence of a tick bite, it seems unlikely to be the cause. It may be prudent, however, to perform blood tests for B. burgdorferi if no other likely diagnosis exists.
Finally, we come to a congenital abnormality of the AV node, manifested as a high degree AV block with a junctional escape rhythm. Literature reports approximately 1 of every 20,000 to 25,000 live births are associated with some degree of congenital complete AV block (CCAVB).
Interestingly enough, patients have been known to survive beyond 60 years without intervention. In CCAVB, the body compensates for the decrease in heart rate with an increase in stroke volume. Therefore, given a functioning junctional escape rhythm, a patient may have no symptoms associated with their cardiac rhythm.
However, these patients often experience syncope or Stokes-Adams attacks usually due to uncompensated bradycardia. If left undiagnosed, their abnormality may only be found on autopsy after a sudden cardiac arrest. Follow-up with monitoring of patients diagnosed with CCAVB is important to identify the need for permanent pacemaker implantation. Any incidence of CHF, persistant bradycardia, or syncope indicates the need for definitive management.
So what was our patient's diagnosis?
The paramedics involved in this case relayed that a diagnosis of congenital complete heard block was made and the patient was scheduled for monitoring for possible pacemaker implantation.
- Athreya BH, Rose CD. Lyme Disease. Cur Prob in Ped 1996; 26:189-207.
- Dedeoglu F, Sundel RP. Emergency Department Management of Lyme Disease. Clin Ped Emerg Med 2004; 5:54-62.
- Surawicz B, Kilans T (eds.). (2008) Chou's Electrocardiography in Clinical Practice: Adult and Pediatric (6th ed.). Saunders, Elsevier Health Scences.
- Michaelsson, M. Congenital complete atrioventricular block. Prog in Ped Cardio 1995; 4:1-10.