AS an interventional cardiologist, I feel a responsibility to provide my patients with minimally invasive treatments and an overall sense of how their health is tracking.
When a patient presents to the catheterisation laboratory with stable chest pain symptoms (ie, angina), a coronary angiogram is the gold standard test to identify major artery blockages. Almost a a quarter of a million Australians experienced angina in 2017–2018.
Imagine you have anginal chest pain but your angiogram comes back clear. There is a one in two chance that you have a disorder of heart artery function which can be missed on a “normal” angiogram. Your chest pain may reflect a heart muscle deprived of oxygen due to either spasm of the arteries or a microvascular disorder.
Microvascular disorders are not visible with a standard angiogram. Although they are treatable, they can cause debilitating symptoms, such as shortness of breath, chest tightness, and fatigue, and have a negative impact on the patient’s quality of life and prognosis (insights into their longer term outlook). The smaller vessels are not playing their part in delivering enough blood to the heart. Testing for disorders of small vessel function approximates zero in most catheterisation laboratories worldwide.
An important part of recovery is having an understanding of what is happening. Not having a clear diagnosis for chest pain can be terrifying and can have an impact on a person’s physical and mental health. Patient understanding of illness is important and may be a crucial part of the treatment response. Patients may lose faith in the medical system and often in themselves if they are sent home with the same symptoms they presented with and no clear diagnosis.
Undiagnosed patients can place stress upon the health system, with frequent presentations to hospital, emergency departments and their GP. They may undergo non-cardiac tests when the answer was right there from the start.
In my experience, there is a large portion of patients who fit into life’s big grey zone, with indeterminate or non-diagnostic stress tests and symptoms that could be considered atypical (chest tightness lasting more than a few minutes or non-exertional features). These patients are most likely to remain undiagnosed and, hence, invasive testing using pressure wire technology can be very helpful in ruling angina in or out.
Although clinical practice has been lagging behind scientific developments over the past 20 years, there has been a recent explosion of interest in this field.
Pressure wires are four times the width of a strand of hair and are traditionally used to measure the significance of large artery blockages on blood supply to the heart. Interventional cardiologists can also be trained to measure the impact and resistance of the smaller vessels of the heart. The invasive procedure involves passing a catheter via the radial artery from the patient’s wrist to the heart. The pressure wire travels up to the heart and down into the distal part of the major coronary artery to capture intracoronary pressure and estimates of coronary flow and resistance. This typically takes only a few minutes and the procedure is all done under sedation; there is no need for a general anaesthetic. Subsequently, testing for spasm can be performed using an acetylcholine challenge whereby transient (near) complete occlusion of the vessel may reproduce the patient’s symptoms.
I am the first author of the CorMicA randomised controlled trial. The objective of the study was to determine whether this type of invasive testing, aligned with stratified treatment, can improve angina and patients’ health. The study was performed in two centres in the west of Scotland and recruited nearly 400 patients with angina undergoing clinically indicated angiography over 12 months. Almost half of these patients (n = 185) had no obstructive coronary disease and 151 were randomly allocated into one of two groups.
For the first arm (intervention arm), treating doctors received the pressure wire test results, which can help them make a diagnosis of either microvascular angina, vasospastic angina or non-cardiac chest pain. Each of these disorders is treated differently according to the current guidelines.
For the second arm (control group), the pressure wire testing was also performed but in a blinded fashion by a second interventional cardiologist; however, the results were not shared with treating doctors. This formed a more effective placebo control group and provided more information on disease prevalence. Doctors looking after patients were required to make a diagnosis with the information they already had and treat accordingly. The primary outcome was angina severity at 6 months. The results were significantly in favour of the intervention arm. Doctors could make an informed diagnosis from the invasive testing and were able to manage and treat patients more effectively, resulting in an improvement in angina and quality of life.
We presented outcomes at one year at the American Heart Association 2020 Scientific Sessions. It was interesting and exciting to see the benefits sustained at 12 months. Angina, quality of life and blood pressure were better in the intervention arm, even though body weight and physical activity levels were not significantly different between the groups.
Invasive testing using pressure wire technology to diagnose microvascular disease is now supported by the recent European Society of Cardiology guidelines, which is a great step forward. Now that the guidelines recommend these tests, I hope fellow cardiologists will feel more comfortable offering them to their patients. Knowing that we have support from best practice guidelines propels invasive testing for angina into the mainstream. We can actually give our patients a clear diagnosis.
I am the first to stress that we don’t have all the answers and that more research and treatments are needed. This is particularly true for microvascular angina. This study has taught me that invasive testing of coronary function is empowering doctors to make the diagnosis for our patients. It is important to listen, to try to understand what symptoms the patient is having and how they affect the patient. If someone has ongoing symptoms that have not responded well to treatment, physicians should consider that there may be undiagnosed treatable disorders of coronary function.
Moving forward, the remaining barriers are infrastructure, accessing the medical technology and software required to conduct these tests, and educating health care providers. Performing pressure wire tests in public and private settings is challenging, as this technology is not covered by health funds. There needs to be more understanding around the kind of savings that can accrue with timely microvascular interventions, and of course, the impact these can have on the patient’s prognosis and quality of life.
The current model, where patients are only tested for these problems by experts in specialised centres, will change. Patient-centred care means putting patients first. Every patient deserves a diagnosis, and invasive testing should be the standard of care for unexplained chest symptoms in the absence of blocked arteries. Having knowledge of someone’s microcirculation, as revealed by pressure wire technology, helps us offer our patients a diagnosis, treatment and prognosis.
Dr Tom Ford is an interventional cardiologist at Gosford Hospital in New South Wales. He has a subspecialist interest in angina with expertise in invasive physiological testing and complex percutaneous coronary interventions. He is a Senior Lecturer at the University of Newcastle, an honorary lecturer at the University of Glasgow, and the current National Young ambassador for Australia to the European Association of Percutaneous Coronary Interventions (EAPCI).
The statements or opinions expressed in this article reflect the views of the authors and do not represent the official policy of the AMA, the MJA or InSight+ unless so stated.