Syncope: Clinical

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Syncope: Clinical

USMLE® Step 2 questions

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USMLE® Step 2 style questions USMLE

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A 76-year-old man comes to the office because of a brief loss of consciousness 2 hours ago. He was having dinner with two friends when he looked "pale" and slumped in his chair. He regained consciousness after about two minutes. He has a history of  hypertension and coronary artery disease, which has been treated with two stents. His temperature is 36.8°C (98°F), pulse is 145/min, respirations are 18/min, and blood pressure is 90/68 mm Hg. Cardiac auscultation shows no murmurs. An ECG is obtained and the rhythm strip is shown below. Which of the following is the most likely diagnosis?


Syncope, or fainting, is when a person loses consciousness and muscle strength. It usually comes on quickly, doesn’t last long, and there’s usually a spontaneous recovery requiring no resuscitation.

It’s caused by a decrease in blood flow to the brain, usually due to low blood pressure.

There’s also presyncope, which is near loss of consciousness with lightheadedness, muscular weakness, blurred vision, and feeling faint without actually fainting.

Presyncope can lead to syncope, so you can think of it as a spectrum of the disease.

Recognizing symptoms of presyncope may allow to act fast and prevent evolution of the episode into a full faint.

The immediate treatment of an individuals with syncope or presyncope starts with laying the individual supine, with legs elevated if possible to help venous return to the heart and restore adequate brain perfusion.

Then, you should assess vital signs, namely a pulse and evidence of respiration, to distinguish cardiac arrest from syncope, and call for additional help if needed.

Finally, you should attempt to arouse the individual without trying to raise them up until they’re ready.

Ok so once the individual has regained consciousness, the next step is to identify the cause.

Neurocardiogenic, vasovagal, and reflex syncope are the most common causes of syncope, and this is a benign condition triggered by parasympathetic activation resulting in vagus nerve discharge.

This discharge may in turn be triggered by urination, defecation, coughing, prolonged standing, or a stressful event like seeing blood and needles.

Carotid sinus hypersensitivity is a variant of neurocardiogenic syncope.



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