This time, we're speaking with Dr Haseeb Rahman. Haseeb started his King’s Health Partners Centre for Translational Medicine (CTM) postdoctoral Clinical Research Excellence Fellowship in autumn 2025. These fellowships provide funding to allow protected research time and training for health professionals working in translational medicine. Haseeb is an interventional cardiologist, and during his PhD he discovered a heart condition called functional coronary microvascular dysfunction. In this interview, he explains how his discovery has changed clinical practice, and discusses his plans to build on this work during the fellowship.

Can you talk us through your career so far?
I'm an interventional cardiologist and an NIHR-funded Clinical Senior Lecturer. I started my clinical registrar training over a decade ago, in West London. I then did my PhD here at King’s College London in Professor Divaka Perera's group, working on a little-known condition that I have termed functional coronary microvascular dysfunction (CMD). My three-year PhD was funded by a British Heart Foundation (BHF) Clinical Research Training Fellowship, so I was fortunate to have protected time to carry out research.

After my PhD, I did a couple of years of interventional fellowship training at the Hammersmith Hospital before returning to King’s as an NIHR Academic Clinical Lecturer in 2021. During this time, I was able to build upon some of my own PhD findings in parallel to my clinical interventional training. Now, thanks to the funding and support offered by a postdoctoral fellowship from King’s Health Partners Centre for Translational Medicine, I’m able to continue in a clinical academic post.

Can you tell us a bit more about your PhD work? 
My research area of interest is a type of heart disease called microvascular angina. Historically, we perceived coronary disease to be related to blockages in the large arteries. You can check for these blockages using an angiogram, a technique where you inject dye into an artery and then observe the artery on an X-ray machine. However, studies found that around half of patients with symptoms of angina (such as chest pain) who undergo an angiogram have unobstructed arteries.

In the past, these patients were told there was nothing wrong with them. But, over the past decade, we realised that they have problems in the small blood vessels that you can't see on an angiogram, and it tends to be women and patients from minoritised ethnic groups who are most affected by this.

Nowadays, we have more specialist tests available that allow us to measure small vessel function. For my PhD, I showed that patients with problems in the small vessels have tangible abnormalities in the way that their heart works during exercise. I was able to investigate this because we have quite a unique setup at King’s, where we can place measuring wires in the heart arteries and ask patients to exercise. Only a few centres offer this type of test worldwide. I also measured blood flow in these patients using specialist MRI scans; again, these tests revealed patterns that were unique to this patient group. Ultimately, I discovered a totally new group of microvascular angina, which I called functional CMD. This term has now entered international nomenclature.

This study, and the work of my successors who then built upon my work, have changed the guidelines for clinical practice. Now, if you find someone who's got symptoms of angina and you see unobstructed coronaries in the angiogram, you must go on and measure their small vessel function. Contributing to this change in international clinical practice has been incredibly rewarding. Just last week, I was a co-director of a two-day international meeting where we were where we explored the advances we've made in microvascular angina research. We also held a live demonstration to show how straightforward it is to perform measurements of small blood vessel function, and how information from these new tests can directly affect patient care and outcomes.

Why did you decide to pursue research alongside your clinical work?
During my undergraduate training at Cambridge University, I completed a BSc as part of my medical sciences degree. I specialised in neurosciences and completed a lab-based project. It was interesting, and I picked up a lot of skills, ranging from practical techniques to an understanding of basic scientific methodology. However, I realised that a fully basic science project didn’t suit my temperament, and I wanted thereafter to work on something that was a little bit more clinically oriented and perhaps more directly translational.

Pursuing a clinical academic career is certainly not the easy route, but it’s incredibly rewarding. Throughout clinical training, you learn that there are lots of questions that we don't know the answers to. You find yourself asking what the evidence base is for a particular treatment. One of the trials I was involved with in Professor Perera’s group showed me the impact that clinical research can have. The trial was a UK-wide study called REVIVED, and it was published three years ago in The New England Journal of Medicine. At the time, stents were being used worldwide to treat heart failure, but it wasn’t clear whether this treatment actually improved outcomes. The REVIVED trial showed that stents did not improve survival in patients with heart failure, and this resulted in clinical practice changing across the NHS in just a couple of weeks. It's exciting to see how, by starting with a question about clinical practice, you can deliver change within the space of 3 to 5 years.

Your work has clearly had an impact on clinical practice. How do you approach sharing your research with other health professionals to enact that change?
I think there is a spectrum of receptiveness in the interventional cardiology community. Some cardiologists are open to the new evidence that small vessel angina is not as benign a condition as we once thought. However, others are less open to new ideas and perhaps subscribe to the dogma that if you've got a normal coronary angiogram, you will not come to harm. They almost close their eyes to the new data.

So, changing the previous way of thinking has also been part of the research journey, but we've had good support from the British Cardiovascular Interventional Society, which has allowed us to spread the word at national meetings. One group we’re trying to reach is cardiologists who have some knowledge of how to perform the more advanced tests, but who might not be confident to adopt it into their day-to-day practice. We approach this conversation by explaining the evidence that supports taking this new approach, and by showing that the tests are not that difficult to do; if you're an interventional cardiologist capable of putting stents in and things like that, then these new tests for small vessel angina are not too far out from what you're doing already.

Why did you apply for the CTM fellowship?
The CTM fellowship offers a fantastic opportunity to build upon the translational research that I've been carrying out thus far. I think the protected academic time is the greatest asset of this fellowship, because it is hard to deliver meaningful research if you're in a full-time clinical role; you can carry on with some research in your free time, but it becomes harder to juggle that when you've got other commitments outside of work. Therefore, having two and a half days per week where I’m protected and able to supervise PhD students, develop new projects and design new techniques will be advantageous.

What will you be working on during the CTM Fellowship?
I will continue working on functional CMD, the condition that I discovered during my PhD. My previous research has shown that patients with functional CMD dysfunction have an abnormally high resting blood flow. I want to understand why this is – is it due to a problem with the blood vessels, or is it due to the heart working inefficiently? To address the latter possibility, my project will explore the energetics of the heart.

The heart has two main sources of fuel: around 70% of its energy comes from fatty acids, and the remaining 20-30% is from glucose. In other disease states, such as heart failure, we sometimes see the heart changing its energy source. Targeting cardiac metabolic processes with therapies is an exciting frontier; GLP1 agonists and SGLT2 inhibitors have been in the news because of their weight loss benefits, and they’re also proving to be blockbuster wonder drugs in lots of cardiac conditions. However, they haven't been used in the context of microvascular angina.

We previously showed that a drug called ranolazine is an effective treatment for functional CMD, but we don't fully understand why. Ranolazine switches cells from fatty acid to a glucose-dependent metabolism, which uses fewer molecules of oxygen to release the same amount of energy. We plan to explore this idea further by performing metabolic substrate switching during an angiogram and observing how this affects resting blood flow. Our hypothesis is that switching to glucose will correct the resting flow in functional CMD, whereas switching to a fatty acid energy source will exacerbate and worsen the condition.

Overall, my CTM fellowship will use advanced imaging and blood vessel organoid technologies to investigate whether functional CMD is caused by a metabolic abnormality. By exploring this question, I will ultimately build pilot data that will support a new programme of research and hopefully allow me to apply for more substantive funding from the BHF, Wellcome or the MRC. The two-year period on this fellowship will allow me to build pilot data, supervise PhD fellows and demonstrate the skills needed to transition to an independent researcher.

You mentioned that you’ll also be working on organoids. How do they support your research plan?
Organoids are tiny three-dimensional (3D) models of human organs, which we can make in the lab. We can take a blood sample from a patient and use it to generate stem cells, which can be induced to become a range of different cell types. In our case, we use them to make heart cells, so we get a 3D vascular structure, or organoid, that has the same genetic code as the patient. We can then test whether changing the metabolism in these organoids has positive or negative effects on their function. Since the organoids match the patient’s genetic makeup, they could be used to predict what sort of therapy might be effective for the patient. However, making an organoid for each patient is quite labour intensive, so we’re also using them to search for genetic or biomarkers that might predict whether a patient will respond well to a particular treatment. You could then screen for this marker in your patient and use the result to inform their treatment plan.

Organoids haven’t really been used to explore this disease before, so the CTM fellowship will allow us to refine this technique and collect pilot data to indicate whether this could form an effective treatment approach.

What is the most rewarding thing about being a research active health professional?
You can see the immediate impact of your change. The research we’ve carried out over the past decade has improved outcomes for patients with microvascular angina, so that's been really rewarding. I also enjoy the process of designing studies that can address clinical problems; I’m fortunate because I’m part of Dr Perera’s research group so we have the capacity to investigate a range of clinical questions as a team. We have a broad area of interest, so we work on projects that touch on different types of heart conditions, but all of it is underpinned by the desire to develop mechanistic understanding of these diseases.

What advice would you give to a health professional who's looking to get started in research?
I would say that it boils down to identifying the unanswered questions that arise in your daily clinical practice. You need to consider if there’s a study that you could carry out to deliver this answer and then reach out to a research group who's interested in answering similar questions. For example, if you’re interested in coronary artery disease or heart failure, you can reach out to our group. There’s so much expertise available across King’s Health Partners, so I would say just get in touch with someone whose interests overlap with yours and ask to meet with them.

Is there any support that you’ve found particularly helpful while you've been navigating your clinical academic career?
The environment at King’s has been great. I work in the School of Cardiovascular and Metabolic Medicine & Sciences, where there’s a great collaborative atmosphere and opportunities for interaction between basic scientists and clinical researchers. We also have fantastic infrastructure here. For example, I’m now looking at a different imaging modality called magnetic resonance spectroscopy (MRS) to non-invasively measure cardiac energetics. Currently, the only way to do this is by putting a catheter into a patient’s vein and measuring lactate and oxygen levels. King’s already has a 7 Tesla magnet, and I’ve recently got a grant to build the extra equipment we’ll need to measure cardiac energetics in house, collaborating with MRS experts at Cambridge University. So I think the collaborative environment, and the fact that we have specialist technology and expertise available in-house facilitates these ambitious cross-specialty research projects that ultimately provide mechanistic answers to important disease processes and a translational output.

The support and mentorship for clinical academics at King’s is also important, including the resources offered by King’s Clinical Academic Training Office (KCATO). I would like to give a special mention here to my academic mentor, Professor Perera. I've known him now for nearly a decade, and he got me interested in research. He's got a passion for forming research questions that address cases where there might not be much evidence behind a particular treatment. That desire to influence practice and improve the way in which we work is key. I’ve found his inquisitive mindset very inspiring, and it has influenced my own academic research journey.

Finally, what do you enjoy doing in your spare time?
I've got a good answer for this in that I've got a 2-year-old, so that takes up a lot of a lot of my spare time! I think this also highlights why the CTM fellowship has been so useful. Previously, I could juggle a full-time clinical role and doing research in my spare time, but when you've got a demanding 2-year-old, and you’re balancing drop-offs and pick-ups with a busy clinical schedule, having the 50% protected academic time really does afford you to make decent headway and deliver meaningful research. But yes, spare time is relatively limited at the moment!