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Case #101

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A 68-year-old male presents with several days of fatigue and palpitations.

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What abnormalities are present on this ECG?

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This tracing demonstrates a tachycardia with narrow QRS complexes. In this case, the ventricular rate is quite rapid, with the mean rate approximately 180 beats/min. Close inspection reveals that the R–R interval is "irregularly irregular," meaning that the distance between QRS complexes, the R–R interval, is variable without pattern. The differential diagnosis for irregular narrow complex tachycardias includes atrial flutter with variable block, atrial fibrillation (AF), and multifocal atrial tachycardia (MAT). When MAT is present, one can visualize at least 3 distinct, identifiable P-wave morphologies. When AF is present, there is no clear atrial activity on the surface ECG, or there may be small, irregular atrial deflections at a rate of 400 to 600/min. When atrial flutter is present, clear flutter waves are seen with a "sawtooth" morphology. This tracing reveals an irregularly irregular rhythm with no clear atrial activity; therefore, AF is the diagnosis. The remainder of the tracing reveals normal axis, normal intervals, and Q waves in leads V1 and V2.

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What are the main clinical consequences of this arrhythmia?

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Atrial fibrillation itself can cause symptoms in some patients including breathlessness, palpitations, and chest pain. In other patients, the arrhythmia can be completely asymptomatic. Sustained rapid heart rates over long periods of time can lead to heart failure and tachycardia-induced cardiomyopathy. When atrial fibrillation is present, atrial contraction is absent, causing atrial stasis and risking left atrial thrombus formation and systemic embolization including stroke.

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Case #102

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This 46-year-old patient has night sweats, a cough, and an abnormal cardiac contour on chest radiograph.

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Image not available.

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What abnormalities are present on this ECG?

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This tracing demonstrates sinus tachycardia at 100 beats/min. The axis is physiologic and intervals are normal. The tracing meets criteria for low precordial lead voltage (QRS amplitude <10 mV) and barely misses criteria for low limb lead voltage (QRS amplitude <5 mV). There is beat-to-beat alteration of QRS amplitude, most notable in the rhythm strip and inferior leads. This is called electrical alternans and can be due to abnormalities of conduction or due to the heart swinging to and fro within a large pericardial effusion. Given this patient's history, the likely explanation is the latter. Of note, electrical alternans due to pericardial effusion can occur with every other beat or over several sequential beats depending on the size of the effusion, cardiac size and mass, and heart rate, all of which interact to create a unique period of motion.

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What further investigation is indicated?

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An echocardiogram would be indicated to establish the diagnosis of pericardial effusion. Pericardial effusion in general may be due to trauma, aortic dissection, autoimmune disorders, infections including viral, mycobacterial, and bacterial causes, malignancy, medications, radiation therapy, postinfarction or postsurgical, and endocrine or metabolic disorders such as hypothyroidism or uremia. In this patient with night sweats and a cough, tuberculous effusion should be considered. Pericardiocentesis of a tuberculous effusion yields a lymphocytic fluid. Pericardial or pleural biopsy may be required to make the diagnosis.

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Case #103

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A 74-year-old woman presents with dizziness.

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