Sympathetic Nervous System Modulation in Hypertension

Sympathetic Nervous System Modulation in Hypertension by Beta-adrenergic Blockade

This is a study of patients with high blood pressure who are already treated with an angiotensin converting enzyme inhibitor or receptor blocker and have achieved good or fair blood pressure control. The hypothesis is that addition of the beta-adrenergic receptor blocker, sustained-release metoprolol, will provide additional blockade of the sympathetic nervous system, thereby further improving left ventricular filling and blood pressure control.

Patients were to receive sympathetic cardiac innervation testing with I-123 MIBG at baseline and again after receiving a titrate dose of beta-blocker. Data were to be assesses by repeated measures testing.

Inclusion Criteria:

• Essential hypertension with blood pressure less than 140/90 on either an ACE inhibitor or angiotensin receptor blocker

Exclusion Criteria:

• Known valvular heart disease of more than mild severity
• Known coronary artery disease defined by an angiographic coronary artery stenosis greater than or equal to 50% luminal diameter narrowing, acute or previous myocardial infarction, or previous coronary revascularization
• Known non-ischemic cardiomyopathy with left ventricular ejection fraction less than 50%
• Atrial fibrillation
• Current treatment with a β-adrenergic blocking drug or a calcium channel blocker
• Current treatment with a psychoactive or other drug known to alter 123I-MIBG uptake
• Participation in another research study within the prior 30 days
• A life-limiting disease process that is likely to preclude completion of study participation
• Pregnancy or breast feeding
• Inability or unwillingness to provide informed consent
• Baseline resting heart rate less than 65 beats per minute
• Diabetes
• Iodine allergy
• Unwilling to sign informed consent.