Page 36 - Journal of Special Operations Medicine - Spring 2017

A Soldier With an Exertional Heat Injury,
Ischemic-Appearing Electrocardiogram, and Elevated Troponins

A Clinical Case Report

Steven G. Schauer, DO; James A. Pfaff, MD

ABSTRACT

Heat injuries are a common occurrence in the military (103.5°F) on initial field evaluation after he reported
training setting due to both the physically demanding for weakness and vomiting while performing duties in
nature of the training and the environments in which we a hot, humid environment. Standard cooling measures
train. Testing is often done after the diagnosis of a heat were implemented, including ice sheets and intravenous
injury to screen for abnormalities. We present the case fluids; a repeated rectal temperature of 37.8°C (100.0°F)
of a 20-year-old male Soldier with an abnormal electro- was recorded. Per base policy, he was then transferred to
cardiogram (ECG) with a possible injury pattern and the ED for evaluation.
an elevated troponin level. He underwent a diagnostic
cardiac angiogram, which demonstrated no abnormal Upon arrival in the ED, the patient was feeling almost
findings. He was returned to duty upon recovery from back to baseline, with resolving heat-exhaustion symp-
the catheterization. Ischemic-appearing ECG and tropo- toms. His initial vital signs were as follows: blood pres-
nin findings may be noted after heat injury. In this case, sure, 131/82mmHg; heart rate, 66/min; respiratory rate,
it was not associated with any cardiac lesions. 12/min; oxygen saturation, 100%; rectal temperature,
36.6°C (97.9°F); and the patient reported no pain or dis-
Keywords: injury, heat; heat-associated injuries; electrocar- comfort at that time. Screening laboratory studies were
diogram; cardiac ordered and the patient was provided with a meal tray.

Urine analysis demonstrated 2+ blood on the urine dip
stick with 92 red blood cells per high-powered field on
Introduction
microscopic analysis. The creatine kinase concentration
Heat injuries are a common occurrence in the mili- was 229U/L (reference range, 30–170U/L). The compre-
tary due to the physically demanding nature of mili- hensive metabolic panel demonstrated a low potassium
tary training and the environments in which we often level at 2.7mmol/L (reference range, 3.5–5.3mmol/L),
train. Case reports have documented that findings of with a normal creatinine level and normal estimated glo-
1,2
electrocardiogram (ECG) studies can be abnormal, as merular filtration rate. Per laboratory practices, this low
can troponin studies. A large case series evaluating the potassium value was reported to the ED by the labora-
3–5
use of troponins as prognostic markers during a heat tory technician. Because of the low potassium level, an
wave demonstrated worse prognosis when troponin lev- electrocardiogram (ECG) was ordered (Figure 1). The
els were elevated in cases of nonexertional heat stroke. machine interpretation read “Normal sinus rhythm. ST
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Another case report of a military trainee documented elevation consider early repolarization, pericarditis or
abnormal cardiac function on echocardiography after a injury.” Because of the ST-segment changes, measure-
heat injury. To the best of our knowledge, the current ment of troponin concentration was added to the lab-
7
article is the first case report of a Soldier with an exer- oratory workup. The troponin level was abnormal at
tional heat injury with an ECG demonstrating a possible 0.173ng/mL (reference range, 0.00–0.039ng/mL).
injury pattern along with an abnormal troponin level.
The decision was made to transfer the patient to a ter-
tiary care center to be evaluated by a cardiologist for
Case Presentation
possible heat-related cardiac injury. The patient was
A 20-year-old man was brought into the emergency seen by a cardiologist at the receiving center upon ar-
department (ED) by air evacuation because of a heat- rival and the decision was made to have the patient
related injury in the field during training operations. undergo a diagnostic cardiac catheterization. The cath-
He was reported to have a rectal temperature of 39.7°C eterization results were normal and the patient was

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