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By Ken Grauer, MD, Professor, Department of Community Health and Family Medicine, University of Florida. Dr. Grauer is the sole proprietor of KG-EKG Press, and publisher of an ECG pocket brain book.
Scenario: The ECG shown above was obtained from a dialysis patient with a long cardiac history, but no acute chest pain. Why did we select the title of "Competing Conditions" for this ECG Review?
Interpretation: The surface ECG shows the net result of electrical forces that are operative. This concept is important to remember when potential "competing conditions" are operative. The rhythm in this tracing is sinus. There is generalized low voltage in the limb leads. The PR interval is upper normal (0.21 second), the QRS is narrow, and the QT appears prolonged. There is left axis deviation (LAD), as suggested by the predominantly negative QRS complex in lead aVF. Prior inferior infarction is suggested by the small q wave in leads II and aVF, and a "forme fruste" Q in lead III. Interplay of electrical forces from probable left anterior hemiblock (LAHB) and presumed prior inferior infarction is the first set of competing conditions that appear to be present in this tracing.
Multichamber enlargement in the form of a notched and peaked P wave in the inferior leads and a deep negative component to the P in lead V1, with a small peaked positive P in leads V2,V3 suggest that combined left and right atrial enlargement is the second set of competing conditions. We suspect underlying cardiomyopathy given this patient's long cardiac history, left and right atrial enlargement, and a precordial lead pattern suggestive of left ventricular hypertrophy (LVH).
The final set of competing conditions most probably accounts for the unusual ST-T wave morphology in the precordial leads. The long QT with T wave peaking in leads V2,V3,V4 suggests hyperkalemia in this patient on dialysis. In contrast, the sagging ST segment in lead V5 suggests "strain" from probable LVH. Especially in view of terminally T wave peaking in lead V5, it is impossible to know how much ST-T depression there would be if opposing forces from hyperkalemia were no longer operative. Morale: Always repeat the ECG after correction of hyperkalemia.