ECG of a patient with hyperfunction of thyroid gland showed heart hurry. It is indicated by depression of the following ECG element:

Answer options

1. P — T interval
2. P — Q segment
3. R — R interval
4. P — Q interval
5. QRS complex

Explanation

Thyroid hormone increases the sensitivity of beta-adrenergic receptors for catecholamines. These exert their effect on the heart by binding to beta1-adrenoreceptors, which in turn increases the heart rate. An increase in heart rate shows a decrease in R-R interval on the ECG. This can lead to systemic hypertension and high output heart failure.