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A 72-year-old man with a history of advanced dementia is brought from home by paramedics for approximately one week of cough followed by two days of worsening shortness of breath and now a syncopal episode. An albuterol treatment was given en route for wheezing. Learn more in this case report.
A 72-year-old man with a history of advanced dementia is brought from home by paramedics for approximately one week of cough followed by two days of worsening shortness of breath and now a syncopal episode. All history is obtained from family and medics as the patient is unable to provide any history. An albuterol treatment was given en route for wheezing.
Exam: Vital signs are normal except for a pulse of 198. The patient is somewhat lethargic and does not answer questions. His lungs have bilateral ronchi without rales or wheezing. There is mild symmetric pitting leg edema, which the family says is chronic and at baseline.
Initial differential diagnosis:
EKG read (see image on the right):
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EKG Analysis: The computer read is correct, but does not mention that the rhythm is SVT with 98% certainty as there is a classic RBBB to explain the wide QRS. It is too slow for atrial flutter with 1:1 conduction and too fast for 2:1 conduction
Case Conclusion: Patient converted with electricity, which was chosen in case the rhythm was V-Tach. This is usually the safest way to go with a wide complex tachycardia, unless you are certain or the rhythm. Adenosine could have been used as it is safe, though rarely effective, in V-Tach. It would not have been wise to use any other AV nodal blocker. He was seen by cardiology who diagnosed SVT with aberrancy (the RBBB).
Wide complex tachycardia can have a variety of causes. If the rhythm is irregular it is most likely atrial fibrillation with associated bundle branch block, but it can rarely be something more serious like polymorphic ventricular tachycardia (PVT) or Wolff-Parkinson-White (WPW) with antidromic conduction. Patients with either of these two rare but more serious dysrhythmias are usually unstable.
When the rhythm is wide and regular, ventricular tachycardia (V-Tach or VT) is the a priori most likely cause of wide complex tachycardia but atrial flutter or paroxysmal supra-ventricular tachycardia (PSVT or SVT) or with aberrancy are also possibilities as is accelerated idioventricular rhythm. Because the treatment is very different, hyperkalemia should always be considered with a new wide QRS, even though the rate will typically be slow or normal rather than fast. Also, sometimes antidromic WPW with a-fib can be so fast that if looks regular when it isn’t. See sample page on next slide for more information on each of these wide complex rhythms.
This patient had a wide regular tachycardia at a rate of about 200 and a right bundle branch block. Initial treatment for this could be either electrical cardioversion, a Valsalva maneuver or a trial of adenosine. If the rhythm is SVT a modified Valsalva has about a 40% chance of working and adenosine has about a 90% chance of working. If the rhythm is V-Tach, adenosine still has about a 15% chance of working, but is at least unlikely to do any harm. Calcium or beta blockers should not be tried even when there is a 2% chance that the rhythm is V-tach because they could be fatal. If the patient converts with adenosine they should still be admitted or at the very least have a formal cardiology consult since this does not prove the rhythm is SVT as opposed to VT.
Peer Review: Dr. Stephen W. Smith of Dr. Smith’s ECG Blog