The Effect of Parkinson Disease on the Nerves of the Heart

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The summary below is from the full report titled "Cardiac Sympathetic Denervation in Parkinson Disease." It is in the 5 September 2000 issue of Annals of Internal Medicine (volume 133, pages 338-347). The authors are DS Goldstein, C Holmes, S-T Li, S Bruce, L Verhagen Metman, and RO Cannon III.

What is the problem and what is known about it so far?

Parkinson disease is a disorder of the nervous system that results in tremor (uncontrolled shaking) of the hands, slow body movements, and rigid limbs. Blood pressure can fall when patients with Parkinson disease stand up (orthostatic hypotension) because the nerves that regulate the heart and blood vessels (cardiac sympathetic nerves) are lost. It is unclear whether this damage is due to Parkinson disease itself or to the drug (levodopa) most commonly used to treat the disease.

Why did the researchers do this particular study?

To determine the frequency of cardiac sympathetic nerve loss in Parkinson disease; whether that loss is related to the duration, severity, and treatment of Parkinson disease; and whether the same damage is found in similar medical conditions.

Who was studied?

The study included 29 patients with Parkinson disease (9 of whom also had orthostatic hypotension), 24 patients with multiple-system atrophy (a different neurologic disease that can mimic Parkinson disease and affects sympathetic nerve function), 7 patients with pure autonomic failure (damage only to the sympathetic nerves), 33 patients with suspected sympathetic nerve problems, and 19 healthy persons.

How was the study done?

First, blood pressure was measured while study participants blew into a tube (the Valsalva maneuver). In this test, blood pressure falls if the sympathetic nervous function malfunctions. Second, all participants had images of the chest obtained after receiving special radioactive material that locates cardiac sympathetic nerves (neuroimaging). Third, the blood levels of substances produced by the sympathetic nerves to the heart were measured.

What did the researchers find?

Patients with orthostatic hypotension because of Parkinson disease and patients who had orthostatic hypotension for other reasons had similar results with the Valsalva maneuver. In contrast, results of the neuroimaging tests in patients with Parkinson disease were clearly different from those in most other study groups. All 9 patients with Parkinson disease and orthostatic hypotension had abnormal neuroimaging studies, as did 11 of the 20 patients with Parkinson disease who did not have orthostatic hypotension. Patients with Parkinson disease also had low blood levels of substances from cardiac sympathetic nerves; this was also different from the findings in most other patients and indicated loss of cardiac sympathetic nerve terminals. Damage to cardiac sympathetic nerves was not related to how long patients had Parkinson disease, to disease severity, or to treatment with levodopa.

What were the limitations of the study?

The results of this small study may not reflect what would be found in the general population of patients with Parkinson disease.

What are the implications of the study?

Most people with Parkinson disease have loss of the sympathetic nerves of the heart that does not appear related to the duration, severity, or treatment of the disease. Neuroimaging tests of the sympathetic nerves to the heart may help distinguish Parkinson disease from other similar conditions in which blood pressure decreases on standing.