Saturday, May 30, 2009

Prescribing exercises for the upper limb- Be aware of unequal BP in arms

A rare cause of upper limb exercise intolerance- Atherosclerosis !!!
Atherosclerotic occlusive disease of the subclavian artery is seen and occasionally will cause pain in the upper extremities. This pain is typically brought on by exercise and especially with repetitive movements of the upper extremity such as brushing one's hair. It is relatively rare for atherosclerosis to affect the upper extremities and cause symptoms. For reasons that again are unclear, it is more common for the atherosclerotic plaque to accumulate on the left side than it is on the right side.

Other associated features may be:
1. Difference in the quality of the pulse between the left wrist and the right wrist. The pulse on the left side may appear weaker.
2. Arm to arm blood pressure differences in upper extremities.

There have been reports of surprising variation in arm-to-arm blood pressure differences. But these variations were no more than 10- 15% and were in the elderly. The hypertension expert of MAYO clinic refers 10 mm Hg in diastolic & 20 mm Hg in systolic BP are within limits of variation of arm BPs. How ever the differential diagnosis in this arm-to-arm blood pressure differences in BP are as follows:

1. Congenital conditions: aortic coarctation and thinning of one of the subclavian, axillary, or brachial arteries.
2. Acquired arterial conditions include aortic dissection, atheroma, thrombus, embolus, and extrinsic compression (as might be seen in association with a mass in the upper chest).

The investigations of choice in this condition are:
1. Contrast-enhanced CT of the chest (to effectively define among the possibilities mentioned above).
2. Vascular ultrasound (transthoracic echocardiography or transesophageal echocardiography).
3. Angiography

The sub-clavian steal syndrome presenting as unequal arm-to-arm blood pressure.
"subclavian steal syndrome": In certain instances repetitive exercise of the left upper extremity can cause not only pain in the left arm but also dizziness and, in fact, patients have been known to actually faint. This condition is called "subclavian steal syndrome".

Cause of "subclavian steal syndrome": Usually there is an atherosclerotic plaque in the subclavian artery on the left side with decreased flow to the left arm. With exercise, the left upper extremity can actually "steal" blood from the brain through the vertebral artery by causing a reversal of blood flow from the brain and down into the left arm. This can result in "syncope" (fainting).

Confirmation of the diagnosis: The diagnosis is suspected by the history and confirmed by the finding of a markedly decreased blood pressure in the left upper extremity compared to the right side and further confirmed by noninvasive testing and ultimately by angiography.

References: 1. 2. Own contribution

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