Increased plasma norepinephrine accompanies persistent tachycardia after hydralazine

Area of Science:

• Pharmacology
• Cardiovascular Physiology
• Neuropharmacology

Background:

• The antihypertensive drug hydralazine can cause persistent tachycardia.
• The role of the peripheral sympathetic nervous system in this side effect is not fully understood.

Purpose of the Study:

• To investigate the involvement of the peripheral sympathetic nervous system in hydralazine-induced persistent tachycardia.
• To examine the relationship between heart rate, plasma norepinephrine, and blood pressure changes after hydralazine administration.

Main Methods:

• Intravenous administration of various hydralazine doses to five hypertensive patients.
• Measurement of heart rate, plasma norepinephrine concentration, and blood pressure over time.
• Analysis of temporal correlations between these physiological parameters.

Main Results:

• Significant correlations were observed between increased heart rate, plasma norepinephrine, and reduced blood pressure at 15 and 30 minutes post-injection.
• At 240 minutes, heart rate and norepinephrine levels remained elevated and disproportionate to blood pressure reduction.
• A consistent correlation between heart rate and plasma norepinephrine was found at 15, 30, and 240 minutes.

Conclusions:

• Continued activation of the peripheral sympathetic nervous system contributes to hydralazine-induced persistent tachycardia.
• Temporal discordance between sympathetic activation and blood pressure suggests a specific mechanism.
• Findings highlight the importance of the sympathetic nervous system in mediating hydralazine's cardiovascular effects.