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A 65-year-old woman presents to the emergency department (ED) with generalized fatigue and palpitations. She was started on an angiotensin-converting enzyme (ACE) inhibitor 2 months ago but has missed her follow-up appointments. What life-threatening metabolic abnormality could be responsible for the findings shown in her electrocardiograph (ECG) tracing?
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
The tracing shows a regular rhythm at 75 beats/min. A P wave is present in front of each QRS complex, indicating that the rhythm is sinus. A flattened P wave (black arrow), a prolonged PR interval (blue double-headed arrow), borderline widened QRS complexes (green double-headed arrow), and—more pathognomonic—pointed, narrow, and tented tall T waves (red arrow) are all features of hyperkalemia.[1] The patient's serum potassium concentration when the tracing was recorded was 7.2 mEq/L.
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
An 83-year-old man with known ischemic cardiomyopathy has an out-of-hospital cardiac arrest. He is rushed to the ED by paramedics. What life-threatening condition is shown in his ECG tracing, and what rhythm is he at risk of developing?
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
The tracing shows a sinus rhythm at 60 beats/min. The QT interval (black double-headed arrow) is prolonged to 680 msec (normal, 300-440 msec), with a QTc also of 680 msec (normal, <460 msec). The T-wave heights alternate (blue arrows), and such alternation is often a precursor to the more severe rhythm of torsades de pointes.[2,3]
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
A 74-year-old man with mild dementia presents to the ED with worsening confusion. His medications include omeprazole, aspirin, simvastatin, and digitalis. He lives alone at his home, and his daughter comes to visit once a week to lay out his weekly medications. What life-threatening condition could be responsible for the findings shown on his ECG tracing?
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
The tracing shows no P waves, with a baseline of irregular, fine undulations, reflecting atrial fibrillation. The QRS complex is narrow and occurs regularly sometimes (in the latter part of the middle strip) and in groups at other times. This tracing is an example of junctional tachycardia with variable conduction to the ventricle. Conducted and skipped QRS complexes are present in patterns of 2:1 (black asterisks), 3:2 (blue asterisks), or 4:3 (red asterisks). The tracing is highly suggestive of digitalis toxicity,[4] especially in this clinical context.
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
A 25-year-old man arrives at the ED with a heavy cough after getting caught outside in a snowstorm while hiking. A routine ECG is performed. The concerned intern takes one look at it and rushes over to show you what he believes to be a serious problem. Do you agree with the intern's assessment of a life-threatening condition seen on the tracing?
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
At first glance, this ECG suggests a run of ventricular tachycardia. However, sharp deflections occur regularly at the same rate as the sinus rhythm seen at the beginning and at the end of the tracing (black double-headed arrows). These deflections are undoubtedly QRS complexes of the sinus rhythm and provide an example of an artifact simulating ventricular tachycardia.[5]
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
A 32-year-old woman comes to the ED complaining of light-headedness and sweating. She is 5'6" tall and weighs less than 100 lb. An ECG is immediately obtained, which evolves while you are watching. What life-threatening condition is seen on the ECG tracing?
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
Sinus rhythm is present at the beginning (blue box), but the QT interval of the sinus beats is long (black double-headed arrows). This is followed by a wide QRS tachycardia at a rate of approximately 200 beats/min (red box). The QRS morphology and axis continuously change, indicating torsades de pointes, which is life-threatening.[6]
Image courtesy of K Wang, MD, University of Minnesota Medical School. Some images adapted from the ECG of the Month series by Dr K Wang.
There are marked biphasic T-waves with deep T-wave inversions seen in the precordial leads (namely, V3-V6) (red boxes). When these findings are encountered in a patient with recent chest pain, clinicians should maintain a high index of suspicion for a very proximal left anterior descending (LAD) lesion.[7]
This patient's laboratory findings were negative for cardiac enzyme changes. However, coronary angiography revealed a significant proximal LAD artery subtotal occlusion, which was then stented.
There is low voltage present throughout this ECG, especially in the limb leads. Electrical alternans is also seen, which can be best appreciated in the precordial leads (the beat-by-beat R-wave amplitude changes are thought to be caused by the heart swinging within a large pericardial effusion) (red and blue arrows). The finding of electrical alternans on ECG, in conjunction with the patient's vital signs, is an early clue that can alert clinicians to the presence of a possible pericardial effusion and a potential impending cardiac tamponade.[8]
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