ECG Review
ECG Review
Peaked T Wave Abnormalities
By Ken Grauer, MD
Clinical Scenario: The ECG in the figure was obtained from a 50-year-old man who presented to the office for evaluation of atypical chest "tightness" over the preceding few months. In view of the fact that the serum potassium was normal at the time this ECG was recorded, how would you interpret this tracing?
Interpretation: The rhythm is sinus at a rate of about 65 beats/min. All intervals are normal. The mean QRS axis is approximately +45°. There is no evidence of chamber en-largement. The finding of note on this tracing relates to assessment of ST segments and T wave appearance. Specifically, ST segments are flattened in many leads and T waves are peaked. The point to emphasize is that this tracing should not be interpreted as a normal ECG. Admittedly, the abnormalities are subtle—yet they are definitely present.
Normally, ST segments in most leads manifest a slightly rounded and upward sloping concavity, blending almost imperceptibly into an upright T wave. This is not the case in the figure. Instead, there is straightening of ST segments—especially in leads II, III, aVF, V3, V4, and V5. This subtle finding may be a nonspecific indicator of underlying coronary disease. Unfortunately, many other entities also produce a similar ECG appearance (ergo designation of ST segment flattening as a "nonspecific" change).
T wave peaking is seen in virtually the same leads on this tracing that show ST segment flattening. The presence of T wave peaking should always suggest the possibility of hyperkalemia. However, serum potassium is normal in this case. T wave peaking is also commonly seen as a normal repolarization variant in otherwise healthy individuals. Distinction from the T wave of hyperkalemia is usually suggested by history (that the patient is healthy and asymptomatic) and the findings that with a repolarization variant the peak of the T wave tends to be rounded, the ascending and descending limbs of the T wave are not as symmetric, and the base of the T wave is wider. A serum potassium level should always be checked if the diagnosis is in doubt.
Not nearly as well appreciated is the fact that T wave peaking may sometimes reflect ischemia. None of the standard leads on a 12-lead tracing directly view the posterior wall of the left ventricle. Posterior wall involvement must, therefore, be viewed indirectly on the ECG—by assessing for changes that occur in anterior leads (i.e., leads V1, V2, and V3) that reflect a "mirror image" view of electrical events in the posterior wall. Instead of the usual manifestation of ischemia (i.e., deep symmetric T wave inversion), posterior ischemia may, therefore, produce symmetric T wave peaking.
Thus, in this patient with a history of chest discomfort, the finding of ST segment flattening in many leads in conjunction with T wave peaking should suggest the possibility of ischemia. The presence of coronary disease was confirmed with further testing.
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