Monday, February 23, 2015

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? NOTE — Enlarge by clicking on Figures — Right-Click to open in a separate window.
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.
QUESTION: What is missing from this presentation?

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.
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).
- 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.