George, who has always suffered from high blood pressure, has recently encountered a perplexing problem. George has been taking those little pills at regular intervals every day in the hope of calming down the ‘pressure storm’ in his body. However, with the arrival of a new blood pressure monitor at his home, everything seems to be a little less certain.
Every day, when George rolled up his sleeves with hope and looked forward to a stable number, the reading on the sphygmomanometer was like a mischievous child, sometimes climbing to the peak of more than 130, and sometimes slipping to the bottom of more than 90, which made him feel uneasy in his heart. Moreover, George's blood pressure was different in his left and right arms, with the left arm consistently much lower than the right. George went to his family doctor and asked, ‘What's going on? Is it a sphygmomanometer problem or is this high blood pressure medicine I'm on not right?’ Faced with George's doubts, the doctor did not give a direct answer, but like a careful detective, began to ask for more clues: ‘George, besides this unanswered question about blood pressure, what other signals is your body sending you?’
George thought back carefully to the occasional dizziness that had struck him a few months ago, and he hadn't looked deeply into it. However, in this recent week, the dizziness had come on like a tidal wave, causing him to face the discomfort head-on. Listening to George's account, the doctor's eyes became more grave. It was as if he had drawn a complex medical map in his mind, and then slowly made a suggestion: ‘’George, perhaps we need to explore a little deeper to see if it is the blood vessels that are harbouring the mystery inside. A CT angiogram, which is like a high-definition X-ray of the blood vessels, helps us to unveil the true nature of blood pressure fluctuations, and in particular to troubleshoot whether there is a ‘behind-the-scenes’ problem like stenosis.’
In the body's vascular network, each artery is like a river; it carries blood. However, when there is an obstacle in one of these rivers, such as a narrowing, blockage or abnormal branching, the original balance can be upset, resulting in an imbalance in the pair of ‘scales’ of blood pressure on both sides. A narrowing of the subclavian artery, an important channel connecting the heart to the upper extremities, is like a river crossing a ravine and encountering a boulder that blocks the flow, slowing it down or even creating a small eddy in some places. As a result, the arm that flows through this ‘canyon’ will receive less blood nourishment, and naturally, the blood pressure there will be much lower than on the other side, as if it were a small, neglected corner of the body, quietly telling of its difficulties.
Aortic coarctation, on the other hand, tears a hole in the main aortic artery, and blood rushes into this newly formed ‘secret space’ - the false lumen. This not only puts enormous pressure on the aorta itself but also diverts the blood that should be flowing to the arm, resulting in a lack of blood supply to the affected arm and a drop in blood pressure. As for peripheral arterial disease, if the roots of a tree on one side are pressed down by a rock or infested by vermin, then the branches on that side struggle to get enough nutrients and appear to wilt. Similarly, when one of the peripheral arteries in the upper limb is narrowed or occluded, the blood pressure in that arm is lowered by poor blood flow, in stark contrast to the other side.
And if the arena of stenosis switches to the segment of the vertebral artery originating away from the heart, the story there is slightly different. While there is the same plague of upper extremity ischaemia, there is more of a direct lack of blood supply. The subclavian artery, at this point, is more like a weary traveller, encountering treacherous obstacles far from the starting point, and struggling to deliver adequate supplies to its destination. In summary, subclavian artery stenosis is a ‘naughty visitor’ that reminds us to keep an eye on the health of this important river to ensure that it brings a constant flow of vitality and nourishment to our bodies.
