What physiological change is often observed in patients with severe hypertension due to pheochromocytoma?

In patients with severe hypertension due to pheochromocytoma, an increased heart rate is a physiological change that is commonly observed. Pheochromocytoma is a tumor that secretes catecholamines (such as epinephrine and norepinephrine) from the adrenal medulla, which can lead to significant cardiovascular effects. The excessive amounts of these hormones stimulate the adrenergic receptors throughout the body, resulting in not only increased blood pressure but also tachycardia, or an elevated heart rate.

The stimulation of beta-adrenergic receptors specifically causes an increase in heart contractility and rate. Patients often present with symptoms such as palpitations or a racing heart due to this heightened adrenergic activity. Therefore, the physiological change of an increased heart rate directly links to the systemic effects of catecholamine release seen in pheochromocytoma, making it the most appropriate choice in this scenario.