Vern, suffering from cardiac arrhythmias, is brought into the emergency room of a hospital. He begins to exhibit tachycardia and as a result loses consciousness. His anxious wife asks you why he has lost consciousness. What would you tell her?
What will be an ideal response?
During tachycardia, the heart beats at an abnormally fast rate. The faster the heart beats, the less time there is between contractions for it to fill with blood again. As a result, over a period of time the heart fills with less and less blood and thus pumps less blood out. The stroke volume decreases, as does the cardiac output. When the cardiac output decreases to the point where not enough blood reaches the central nervous system, loss of consciousness occurs.
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