Is there a difference between clinical angina and experimentally inducible angina? A placebo-controlled experiment in stable coronary artery disease

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Context:Patients often experience chest pain when the heart is short of blood flow due to a narrowing in an artery. We call this symptom 'angina'. We can treat angina with tablets; but sometimes this is not enough, and so doctors open up the narrowing with a metal stent (angioplasty). Unfortunately, some patients still have pains even after this. Perhaps the pain was not caused by the narrowing after all? Cardiologists can test whether a narrowing is restricting blood flow and therefore should have angioplasty. However, there is currently no test to say that a patient's pain is actually caused by the narrowing rather than something else. As a result, cardiologists cannot tell whether angioplasty will alleviate the pain or not. This is an important problem because angioplasty cannot genuinely relieve pain that was not caused by the narrowing, yet such angioplasties still carry risks and cost the NHS tens of millions of pounds per year.Objectives:The principal aim is to test whether we can identify which patients have chest pain that is truly caused by a narrowed artery. In 65 patients who have been referred for angioplasty I will:1. Describe the pattern of chest pain before and after angioplasty.Patients will record the site, nature and severity of each episode of chest pain they experience for 1 month before and 1 month after angioplasty. They will record these episodes on a smartphone application. In this way, we will know how effective the procedure was and which pains were relieved with angioplasty.2. Test whether the pain is actually caused by a narrowed artery.During a normal angioplasty, a miniature balloon is inflated to expand the metal stent. This balloon inflation temporarily blocks blood flow and often causes pain. We will conduct several such balloon inflations to intentionally restrict blood flow and ask the patient to describe their pain in real time. Presumably, if the patient's angina was really caused by the narrowed artery, then blocking the artery should recreate the pain. However, if the narrowed artery was not the cause of their pain, any pain they feel during the experiment would be different in nature. A unique feature of my experiment is that it will be blinded, which means sometimes we really will block the artery and other times it will only be pretend (placebo). The pain should come with the real episodes and not the pretend ones.3. Test whether patients with closely matching symptoms have a better response to angioplasty.If this test, of intentionally blocking the artery, shows a pain closely resembling the patient's usual angina, I speculate that these patients will get a great relief of pain from the angioplasty procedure. In contrast, if this test produces a very different type of pain, I speculate that these patients will not get so much relief from the angioplasty. Applications and benefits:More than 500,000 angioplasty procedures are performed each year for the treatment of angina. This is a major cost to our NHS. Angioplasty is technically excellent at opening the artery. But if a patient's symptoms were not in fact caused by the narrowed artery, even brilliant angioplasty cannot relieve their symptoms. We have not studied enough how the nature of symptoms relates to the narrowed artery. This has been a blind spot in cardiology for many years. My research seeks to resolve this by taking a fresh, personalized, symptom-based approach to angina and angioplasty. If successful, this research could pioneer a new diagnostic test. Such a test could tell us which patients have real angina caused by a narrowed artery, and which patients have chest pain from another source. With this diagnostic ability, cardiologists could better tailor their treatments; identifying the patients in whom stents could most help symptoms, whilst preventing the unnecessary cost and risk associated with angioplasty in those whose symptoms were caused by something else.