ECG Blog #106 (Sinus Tachycardia - Hyperkalemia - DeWinter T Waves - Heart Rate)

Interpret the ECG shown in Figure 1 — obtained from a middle-aged adult.

• Are there DeWinter T waves in the chest leads of Figure-1? Is this patient about to occlude his proximal LAD (Left Anterior Descending) coronary artery?
• OR — Does this patient have hyperkalemia?
• HINT: What is missing (that should never be missing)?

Figure 1: ECG obtained from a middle-aged adult. Are these DeWinter T waves? Does the patient have hyperkalemia? 

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Systematic Interpretation of Figure 1: There is some baseline movement with slight artifact. The overall rhythm is regular — with upright P waves in lead II, so that the rhythm is Sinus Tachycardia. The rate is ~160/minute (the R-R interval is just under 2 large boxes in duration).

• The PR interval is normal — and the QRS complex is narrow. The QT interval is probably normal given the exceedingly rapid heart rate.
• The axis is indeterminate (QRS complexes are nearly isoelectric in virtually all limb leads).
• There is no chamber enlargement.

Regarding Q-R-S-T Changes:

• There appears to be a Q wave in lead aVL.
• Transition is slightly delayed to between V4-to-V5 (as the point where the R wave becomes taller than the S wave is deep).
• The most remarkable finding on this tracing are the rather tall and peaked T waves, especially in leads V2-thru-V4. In a patient with chest pain — this appearance resembles that of the DeWinter T waves that herald proximal LAD occlusion. There is even suggestion of some J-point ST depression in leads V3,V4 and V5 prior to the steep rise in T wave ascent. In a patient predisposed to hyperkalemia — the T wave peaking seen here should also prompt consideration of this electrolyte disorder.

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QUESTION: What is missing from this presentation?

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ANSWER: No history was given ...

• It turns out that this 12-lead ECG was recorded as part of an exercise stress test on an otherwise healthy and asymptomatic middle-aged man. The purpose of this test was to assess exercise capacity. There was no chest pain — and no history of renal disease or other medical problems.

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The LESSON to Be Learned: ECGs cannot be intelligently interpreted in a vacuum. If told that this patient was having new-onset worrisome chest pain — We would wonder why he is so tachycardic, and we would clearly be concerned that the prominent T wave peaking might be ischemic or a DeWinter T wave equivalent. We would check serum K+ values as part of our evaluation, especially if the patient had any factors potentially predisposing to hyperkalemia.

• T wave peaking as seen here commonly occurs in healthy adults during exercise. This T wave change is transient — and resolves after termination of exercise.
• Rapid-upsloping ST segment depression as seen here in several chest leads is a normal response to exercise.
• This patient had excellent exercise capacity for his age. His exercise test was entirely normal — and he was cleared to perform vigorous aerobic activity. No laboratory testing was done (as none was necessary).

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- For more information — GO TO:

• For review of the Systematic Approach to ECG Interpretation — Check out our ECG Blog #93. 
• For review on DeWinter T Waves — Check out our ECG Blog #53.
• For review on Hyperkalemia — Check out our ECG Blog #10.

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