Symptoms such as severe tachycardia, fever, dehydration, heart failure, and coma are consistent with what thyroid-associated health condition?

Thyroid Storm

Explanation:

Based on the information provided within the question it can be said that all of the symptoms mentioned are associated with Thyroid Storm. This is a very dangerous and life-threatening condition, which usually occurs within individuals who have hyperthyroidism and have not been treated. All of the symptoms mentioned (severe tachycardia, fever, dehydration, and heart failure) occur during Thyroid Storm and without immediate attention it is usually fata.