Does vasopressin (antidiuretic hormone) increase heart rate?

Effect of Vasopressin on Heart Rate

Vasopressin does not increase heart rate; it typically causes a decrease in heart rate through its direct cardiodepressant action that is independent of cardiac vagal or sympathetic activity. 1

Mechanism of Action and Cardiovascular Effects

Vasopressin is a potent nonapeptide vasopressor hormone that exerts its effects through several receptor subtypes:

• V1a receptors: Mediates vasoconstriction in vascular smooth muscle 2
• V1b receptors: Stimulates ACTH release
• V2 receptors: Produces antidiuretic effects
• Oxytocin receptors: Can cause vasodilation
• Purinergic receptors: Limited relevance in septic shock 2

Vasopressin's cardiovascular effects include:

1. Blood Pressure: Increases systemic vascular resistance and mean arterial pressure 3
2. Heart Rate: Tends to decrease heart rate 2, 3
3. Cardiac Output: Tends to decrease cardiac output 2, 3

According to the FDA label, "vasopressin tends to decrease heart rate and cardiac output. The pressor effect is proportional to the infusion rate of exogenous vasopressin." 3

Physiological Explanation

The heart rate-lowering effect of vasopressin occurs through several mechanisms:

1. Direct Cardiodepressant Action: Vasopressin has a direct cardiodepressant effect that is not dependent on cardiac vagal or sympathetic activity 1

2. Baroreceptor Reflex Enhancement: Vasopressin increases the maximum bradycardia that can be elicited through baroreceptor reflexes, though it does not alter the slope relating change in heart rate to change in blood pressure 1

3. Catecholamine-Independent Mechanism: V1a-receptor activation of vascular smooth muscle induced vasoconstriction is catecholamine-independent, which explains why vasopressin complements norepinephrine in septic shock 2

Clinical Implications

The heart rate-lowering effect of vasopressin has important clinical implications:

• Septic Shock: Vasopressin is often used as an adjunct to norepinephrine in septic shock, where it can increase blood pressure while potentially decreasing norepinephrine requirements 2

• Cardiac Function: The tendency to decrease heart rate and cardiac output should be considered when using vasopressin, especially in patients with compromised cardiac function 2

• Acidemia: The clinical effectiveness of vasopressin appears to be impaired in the setting of acidemia, similar to other vasopressors 4

• Autonomic Dysfunction: Vasopressin plays an important role in preventing or minimizing orthostatic hypotension in patients with autonomic insufficiency 5

Comparison with Other Vasopressors

Unlike β-adrenergic agonists such as epinephrine and dobutamine that increase heart rate, vasopressin tends to decrease heart rate:

• Epinephrine: Increases heart rate through β-stimulation 2
• Norepinephrine: Can increase heart rate, though less than epinephrine 2
• Vasopressin: Tends to decrease heart rate 2, 3, 1

Dosing Considerations

When using vasopressin in clinical practice:

• Septic Shock: Low-dose vasopressin (0.01-0.04 units/min) can be used as an adjunct to norepinephrine 2
• Variceal Hemorrhage: Terlipressin (a synthetic analogue of vasopressin) is administered at an initial dose of 2 mg IV every 4 hours 2

In conclusion, unlike many other vasopressors, vasopressin does not increase heart rate but rather tends to decrease it through direct cardiodepressant effects and enhanced baroreceptor reflexes.