Six Abnormal ECGs — Not All Are Cases of the Heart: Slideshow
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Case 1
A 65-year-old man presents to the emergency department (ED) with shortness of breath. He reports worsening dyspnea on exertion associated with chest tightness, wheeze, and cough. He recently recovered from a cold with nasal congestion, clear rhinorrhea, and nonproductive cough. He has smoked 2 packs per day for the past 30 years and has not been seen by a physician for 20 years. His vitals are: heart rate, 103 beats per minute (bpm); blood pressure, 140/85 mm Hg; respiratory rate, 28 breaths per minute, and oxygen saturation, 85% on room air. An electrocardiogram (ECG)is obtained and suggests what chronic condition?
Answer
The patient is suffering from a chronic obstructive pulmonary disease (COPD) exacerbation. Although COPD is not diagnosed based on ECG findings, it is often the first diagnostic test performed due to the overlap of cardiac and pulmonary diseases. This ECG demonstrates a constellation of findings that suggest COPD: sinus tachycardia, P pulmonale (a P wave amplitude > 2.5 mV in the inferior leads), rightward axis, right bundle branch block (RBBB), and low QRS voltage. In addition, the slight ST segment depressions in the inferior leads are suggestive of prominent atrial repolarization abnormalities.
A tachycardic rhythm is a compensatory mechanism for hypoxia or poor right ventricular function (in the setting of cor pulmonale), but other supraventricular arrhythmias, such as atrial tachycardia (unifocal or multifocal), atrial fibrillation, or atrial flutter, can also be present. P pulmonale is a relatively insensitive predictor of right atrial enlargement, but tends to be more prominent during acute exacerbations. Rightward axis, complete or incomplete RBBB, and right ventricular hypertrophy are signs of pulmonary hypertension and cor pulmonale. Low voltage in the limb leads is attributed to increased impedance through a hyperinflated chest.
Case 2
A 19-year-old man presents to an ED in Connecticut with an episode of shortness of breath and syncope. He was mowing his lawn when he began to feel short of breath and light-headed, causing him to go inside where he reportedly "passed out." He was unresponsive but did not exhibit any seizure-like activity and he quickly regained consciousness. He reports having palpitations, described as irregular, forceful beats, and fatigue for the past week, but the rest of his review of systems is grossly normal. His vitals are: temperature, 96.7°F (35.9°C); pulse rate between 40 and 120 bpm; respiratory rate, 16 breaths per minute, blood pressure, 102/46 mm Hg; and oxygen saturation of 96% on room air. His physical examination is notable for an irregular tachycardia and multiple, bilateral macular erythematous lesions with central pallor on his thighs. An ECG is obtained revealing atrioventricular dissociation most consistent with what etiology?
Answer
The patient is suffering from disseminated Lyme disease. The diagnosis is made based on his skin lesions, geographic location, and ECG findings. Approximately 8%-10% of patients with Lyme disease have cardiac involvement. The ECG demonstrates atrioventricular block with 2 independent rhythms: a junctional tachycardia at 130 bpm (black asterisks) and a sinus tachycardia at 100 bpm (red asterisks). Presenting symptoms may include light-headedness, palpitations, or syncope, and are typically caused by a conduction defect ranging from first-degree block to complete atrioventricular dissociation.
The rhythm strip of the same patient demonstrates an interval of nonconducted P-waves indicative of complete heart block. Fortunately, most conduction defects are reversible processes after treatment of the underlying infection. Other cardiac manifestations of disseminated Lyme disease include myopericarditis, ventricular dysfunction, cardiomegaly, and pericardial effusion with possible tamponade.
Case 3
A 60-year-old man with a history of diabetes mellitus and hypertension presents to the ED with a 1-day history of retrosternal chest pain. The pain began while he was resting and has gotten progressively worse. It is sharp, of moderate intensity, with radiation to his right shoulder and neck. It is worse when he lies down or takes deep breaths, but is relieved by leaning forward. He reports a recent respiratory infection and diagnosis of costochondritis. His vital signs are : temperature, 98.6°F (37.0°C); heart rate, 80 bpm; blood pressure, 130/80 mm Hg in right arm and 134/77 mm Hg in left arm; and respiratory rate, 16 breaths per minute. His physical examination is grossly normal. His initial troponin I and CK-MB are within normal limits. An ECG is performed and is indicative of what process?
Answer
The patient is suffering from acute pericarditis. His ECG shows ST-segment elevation in the inferior and anterior leads (black arrows), as well as PR-segment elevation in lead aVR (red arrow).
Acute pericarditis classically shows widespread, concave-upward ST-segment elevation with PR-segment depression and PR-segment elevation in lead aVR. The ECG abnormalities may evolve through 4 phases:
- Stage I: diffuse ST-segment elevation and PR-segment depression (60-80% of cases);
- Stage II: normalization of the ST and PR segments, with flattening of the T wave;
- Stage III: widespread T-wave inversions; and
- Stage IV: normalization of the T waves.
The prompt institution of therapy may prevent the appearance of all 4 stages.
Acute pericarditis may be differentiated from myocardial infarction by concave (vs convex) ST-segment elevations, absent Q-waves, normal R-wave voltage, PR-segment depressions, and absent atrioventricular blocks or ventricular arrhythmias. The most reliable distinguishing feature may be the ratio of ST-segment elevation (in mm) to T-wave amplitude (height in mm) in lead V6. When this ratio exceeds 0.24, acute pericarditis is almost always present.
Case 4
A 17-year-old man is brought by emergency medical services (EMS) to the ED after being found in cardiac arrest following a blow to the chest. The patient was accidentally elbowed in the chest by a teammate and became immediately unresponsive. Cardiopulmonary resuscitation was initiated after no pulses were palpated and EMS arrived in 5 minutes. A rhythm strip (shown above) showed ventricular fibrillation and one 200-joule shock was administered, which converted the patient to normal sinus rhythm and allowed him to regain consciousness. In the ED, he reports only minor anterior chest wall pain and the rest of his history is grossly normal. His vital signs are : heart rate, 106 bpm; blood pressure, 130/71 mm Hg; respiratory rate, 28-30 breaths per minute; oxygen saturation, 83% on room air, corrected to 98% on nonrebreather, then 99% on 2 L of nasal cannula. His examination is notable only for some bruising over his sternum. A chest x-ray shows mild underaerated lungs, laboratory results including cardiac enzyme levels are grossly normal, a chest computed tomography scan shows mild pulmonary and periportal edema, and an echocardiogram was grossly normal. A repeat ECG is obtained (shown below). What is the most likely etiology of the patient's cardiac arrest?
Answer
The patient suffered from commotio cordis, or concussion of the heart. His ECG was notable only for sinus tachycardia, with a rate of approximately 110 bpm. Commotio cordis is defined as an instantaneous cardiac arrest produced by a witnessed, nonpenetrating blow to the chest, in the absence of preexisting heart disease or identifiable morphologic injury to the sternum, ribs, chest wall, or heart. It is a diagnosis of exclusion after other causes such as substance abuse, myocardial infarction, electrolyte abnormality, prolonged QT syndrome, and hypertrophic obstructive cardiomyopathy have been ruled out.
Not all impacts to the anterior chest will lead to the ventricular fibrillation observed in commotio cordis. The impact must be delivered 10-30 milliseconds before the peak of the T wave in the cardiac cycle to induce ventricular fibrillation. Induction is likely secondary to the activation of potassium-carrying ion channels via mechanoelectric coupling. The activation of these ion channels generates an inward current, thus locally augmenting repolarization and resulting in premature ventricular depolarization and the initiation of unstable ventricular arrhythmias. If impact occurs during other portions of the cardiac cycle, different conduction disturbances, such as heart block, bundle branch block, or transient ST segment elevation, may be induced. Early CPR and use of an automatic external defibrillator dramatically improve survival rates.
Case 5
A 19-year-old man is brought to the ED after ingestion of a bottle of pills. The man was found confused and agitated with an empty bill bottle after an apparent suicide attempt. The name of the pills is unknown, but they were prescribed to the patient's grandmother for chronic neuropathic leg pain. In the ED, he is agitated, disoriented, confused, and unable to answer questions appropriately. His vital signs are: temperature 101.4°F (38.6°C), heart rate 140 bpm, and blood pressure 82/45 mm Hg. On examination, the patient is sweaty and warm to the touch, without cardiac, pulmonary, or focal neurologic findings. His blood glucose was 114 mg/dL. An ECG is performed and a generalized tonic-clonic seizure subsequently develops. What is the most likely class of medications the patient ingested?
Answer
The patient overdosed on tricyclic antidepressant (TCA) ingestion. The diagnosis is made given the clinical presentation, ECG findings, and historical clues. The ECG shows a number of findings consistent with TCA overdose: sinus tachycardia, prolonged QRS interval, rightward axis, tall R wave in lead aVR, and abnormal repolarization.
TCAs block fast sodium channels in myocytes during phase 0 of the action potential, similar to class IA antiarrhythmics (eg, quinidine and procainamide). This lengthens the myocyte action potential duration and prolongs the QRS complex. The cardiac manifestations of tricyclic antidepressant overdose are sinus tachycardia (most common), right axis deviation, RBBB with a tall R wave in lead aVR (presumably because of increased sensitivity of the right bundle branch to tricyclic antidepressant poisoning), bradyarrhythmias, advanced conduction system disease, and an altered pattern of repolarization similar to the Brugada pattern (RBBB with ST-segment elevation in the anterior precordial leads). An elevated R wave in lead aVR, a wide QRS interval, and right axis deviation are all predictors of worse outcomes.
Case 6
A 38-year-old man is brought to the ED with altered mental status. He was found on the ground in front of an apartment building unresponsive by neighborhood residents. His vitals signs are: rectal temperature, 85.4°F (29.7°C); heart rate, 38 bpm; blood pressure, 88/40 mm Hg; and respiratory rate, 24 breaths per minute. Finger pulse oximetry measurements were not successful. Physical examination is notable for limited response to vocal commands, rhonchi and dullness to percussion in the right lower lung field, delayed capillary refill, and blue fingers and toes. There are no focal neurologic deficits and no obvious signs of trauma. Routine blood work is within normal limits and a chest x-ray reveals consolidation in the right lower lobe consistent with pneumonia. An ECG is performed and is consistent with what principal diagnosis?
Answer
The patient is suffering from severe hypothermia. The patient's ECG demonstrates classic abnormalities associated with hypothermia: sinus bradycardia and Osborn waves (or J waves). Osborn waves are seen at the QRS complex-ST segment junction in all leads. They are thought to represent an alteration in the initial phase of ventricular repolarization. Although Osborn waves are thought to not affect the ST segment, the ECG must be interpreted in the appropriate clinical context and the apparent ST segment elevations should not be misinterpreted as evidence of myocardial injury.
Other possible ECG findings in hypothermia are atrial and ventricular dysrhythmias, and prolongation of PR, QRS, and QT intervals. Rewarming is typically sufficient to return cardiac function to normal, but in some cases of ventricular arrhythmias, amiodarone or external pacing is used.
