Does hydralazine affect heart rate?

From the Guidelines

Hydralazine typically increases heart rate due to its direct vasodilator effects, which can lead to reflex tachycardia as the body attempts to maintain cardiac output and blood pressure. This medication relaxes smooth muscle in blood vessel walls, causing blood vessels to dilate and blood pressure to decrease 1. When blood pressure drops, the body compensates through a reflex tachycardia (increased heart rate) mediated by the baroreceptor reflex. The heart rate increase is often dose-dependent, with higher doses of hydralazine potentially causing more significant increases in heart rate.

Some key points to consider when using hydralazine include:

• The typical dose range for hydralazine is 10-50 mg four times daily for hypertension, with careful titration to minimize side effects including the reflex tachycardia 1.
• Hydralazine is frequently prescribed alongside beta-blockers or other medications that can counteract this reflex tachycardia 1.
• Patients taking hydralazine should be monitored for excessive heart rate increases, especially those with pre-existing cardiovascular conditions 1.
• The addition of hydralazine to the regimen of diuretic, ACE inhibitor or ARB, and β-blocker may be considered in certain patients, such as black patients with NYHA class III or IV heart failure 1.

Overall, hydralazine's effect on heart rate should be carefully monitored and managed, particularly in patients with pre-existing cardiovascular conditions.

From the FDA Drug Label

The peripheral vasodilating effect of hydrALAZINE results in decreased arterial blood pressure (diastolic more than systolic); decreased peripheral vascular resistance; and an increased heart rate, stroke volume, and cardiac output.

• Hydralazine affects heart rate by increasing it, as a result of its peripheral vasodilating effect.
• This increase in heart rate is a direct consequence of the drug's mechanism of action, which includes the relaxation of vascular smooth muscle and the resulting decrease in peripheral vascular resistance.
• The increase in heart rate is also associated with an increase in stroke volume and cardiac output 2.

From the Research

Hydralazine's Effect on Heart Rate

• Hydralazine is a direct-acting vasodilator that has been used to treat hypertension since the 1950s 3.
• One of the adverse effects of hydralazine is reflex tachycardia, which is an increase in heart rate in response to the drug's vasodilatory effects 3.
• A study published in 1980 explored the correlation between hydralazine-induced tachycardia and overall cardiovascular reactivity to sympathetic stimulation in normal subjects 4.
• The study found that hydralazine increased heart rate, mainly in the standing position, and that the magnitude of this response was related to individual baroreceptor sensitivity 4.
• The results suggest that hydralazine tachycardia is reflexly induced and can be predicted by suitable tests of sympathetic responsiveness 4.

Comparison with Other Antihypertensive Agents

• Beta-blockers and ACE inhibitors are commonly used to treat hypertension and are recommended by various guidelines 5, 6.
• These agents have complementary actions on the sympathetic nervous system and renin-angiotensin-aldosterone system, which influence cardiovascular risk and disease outcomes 6.
• Hydralazine, on the other hand, is a direct-acting vasodilator that reduces blood pressure by relaxing blood vessels, but its effect on clinical outcomes remains uncertain 3.
• The choice of antihypertensive agent depends on individual patient characteristics, such as the presence of coronary artery disease or heart failure, and the need to optimize treatment based on the patient's hypertension subclass and cardiovascular risk profile 5, 6.