Climate Cardiology: If Not Now, When?

Climate change will inevitably affect cardiovascular health in countless ways, from temperature swings and air pollution to disruptions in care, and it’s already begun to do so. Cardiologists are now urging their colleagues to take heed and prepare for what’s ahead.

Thanks to the COVID-19 pandemic, there’s growing awareness that cardiology doesn’t exist in a vacuum. Before SARS-CoV-2 was on anyone’s radar, TCTMD spoke with several physicians sounding the alarm about climate change and how it would impact the heart—since then the urgency has continued to build.

“Just as we are passionate about controlling lipids and blood pressure, we should feel passionately about controlling climate-related risk. We’ve got to get past that denial that it’s abstract and in the future, because it really is here now,” said Dhruv Kazi, MD, MSc (Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA), a cardiologist and health economist.

“Many people in the community are realizing that this isn’t 40 years ago, unfortunately, when maybe there was a chance to [stop] the onslaught of climate change,” said Rajesh Vedanthan, MD, MPH (NYU Langone Health, New York, NY), whose work lies in global cardiovascular health. “In a way, this is the reality we live in now and that we’re going to be living in in the future. It’s almost too late to try and steer that ship, but what we can do is try to mitigate the impacts of it.”

The need for focused attention on this topic is so great that some have proposed a dedicated subspecialty: climate cardiology. This term—combining what had been disparate concepts into one—in fact serves as the title of a new commentary, published recently in BMJ Global Health, that summarizes what’s known about the hazards and offers ways to address them.

Just as we are passionate about controlling lipids and blood pressure, we should feel passionately about controlling climate-related risk. Dhruv Kazi

So why now? Vedanthan, a co-author of the review, told TCTMD that the real question might be: “Why not much earlier? Obviously, I think the world and the global health community and the cardiovascular health community have needed to be paying attention to this for many years.” Putting a name to the concept “helps to galvanize the community,” he said, not just in cardiology but also in climate research, public health, and beyond.

Speaking with TCTMD, Michael B. Hadley, MD, MScPH (Icahn School of Medicine at Mount Sinai, New York, NY), the paper’s first author, said that “climate change is probably the key challenge of the 21st century for the world.” Their goal in writing it was to “map out” the intricate ways the climate crisis might affect cardiovascular health, in order to better understand how best to explore them.

This field of study is “still quite early, but it’s increasingly becoming something that people are talking about,” said Vedanthan. “A tide is rising, for sure.”

Just last week, the American Heart Association (AHA) alerted the public that amid record-high heat this summer in the United States people need “to take extra steps to protect their heart.” The New York Times took note, featuring a lengthy article on the health risks posed by extreme heat.

Recognizing the ‘Existential Crisis’

Climate change and its implications have inspired various institutions, such as Columbia University, New York University, and the University of California, San Francisco, to start new programs, Vedanthan pointed out. The National Institutes of Health also is funding and encouraging research studies on the topic; among them is the PURI-HF trial, led by Vedanthan, which is set to test whether indoor air purifiers can improve functional capacity for heart failure patients with reduced ejection fraction in India.

For over a decade, cardiologist Thomas Münzel, MD (University Medical Center Mainz, Johannes Gutenberg University, Germany), has done research focusing on environmental risk factors for CVD, particularly noise and air pollution. “It’s a great idea” to conceive a new specialty in cardiology, he told TCTMD. “Most of the diseases occurring in response to climate or environmental threats are cardiovascular diseases.”

In short, “cardiologists need to be more informed about the problems,” he said. From his perspective, the culprit is more than just climate, though. He suggested a taking a broader view, with a better term perhaps being “the environment and cardiovascular disease.”

Kazi agreed that when it comes to climate change’s health implications “cardiovascular disease has been in people’s blind spots as they’ve focused on other health conditions.”

But he also cautioned against thinking of climate cardiology as a new, stand-alone subspecialty.  “Climate change is such an existential crisis that it should be woven into the curriculum for all trainees and all practitioners, wherever they go,” Kazi stressed, adding, “We need to start having these conversations, not just at research conferences but in our everyday discussions, so that it doesn’t feel like climate change is something climatologists worry about but something very much in our wheelhouse.”

Cardiologists, who are influential in both their patients’ lives and in their communities, can make a difference, Kazi stressed.

How Climate Disrupts the Heart

As noted in an interactive infographic published in the New England Journal of Medicine back in 2019, the health risks of climate change intersect across numerous disease states and medical specialties.

Perhaps the “most-mature” area of study, and one that can be used as a model for how to address other environmental risk factors going forward, is air pollution, Hadley suggested. Back in 2004, the AHA issued a statement on how polluted air can affect the heart, and as reported by TCTMD, study after study has documented that link.

There are more than 8 million excess deaths due to air pollution every year, Münzel pointed out, but the topic garners less than half a page in the 2021 European prevention guidelines. The document also contains a more-general, but similarly brief, section devoted to environment, air pollution, and climate change. In the 2019 US prevention guidelines, there’s no mention of these topics.

Münzel highlighted people living in cities as particularly vulnerable. By 2050, three-quarters of the world’s population is expected to reside in urban areas, which consume 60% to 80% of global energy and produce 70% of greenhouse gas emissions, he and his colleagues note in a European Heart Journal editorial published last year. They propose strategies for promoting “heart-healthy cities” that limit exposure to “noise, air pollution, temperature, and outdoor light.”

Most of the diseases occurring in response to climate or environmental threats are cardiovascular diseases. Thomas Münzel

In their paper, Hadley and colleagues outline the manifold links between climate change and CV health. Things like “frequent extreme weather events, air pollution exposures, ecosystem collapse, and declines in global food production and the nutritional quality of major cereal crops” can have direct effects, with indirect effects related to “structural and social determinants of health (eg, poverty, inequality, housing quality), underlying susceptibilities (eg, aging), disruption of social services, and the capacity of health systems to manage climate hazards,” they write.

Kazi pointed out yet another factor that undermines CV health: “There is the mental health aspect of it, and I think we’re underestimating the effect of climate change anxiety or the stress related to acute severe weather events and its relationship to cardiovascular disease.”

Basic science research into how exactly the climate crisis impacts the heart is in its early stages. What’s hardest to capture, said Münzel, is the additive effect of different environmental factors. “We have exposure chambers where we can combine noise and air pollution,” which often go together in the real world, he explained. “The combination of different environmental stressors and their cardiovascular impact—this is more important for the future, not just a single [risk factor].”

It’s also possible for the mechanisms to move in different directions, with “big overlap,” Münzel said. “For example, when you have cardiovascular disease already, you are more likely to get an acceleration of the atherosclerotic process. On the other hand, if you have strong air pollution exposure, you are more likely to develop coronary artery disease.”

Beyond ‘Warming’

Importantly, climate change isn’t just about global warming.  Vedanthan described climate change as a “matrix, or a mishmash, of different climate and weather events that are happening in different parts of the world in different patterns.

“Some places are getting hotter and drier. Some places are getting hotter and wetter. Some places are actually getting cooler and drier. So it’s quite variable. I think the one common thing is that climate patterns that have been there for a long time are definitely changing . . . and then extreme acute weather events are also happening with greater frequency,” he observed.

Kazi stressed that a key message is that the threats posed by climate change aren’t distant, far in the future or far across the globe. “It’s happening in Texas, it’s happening in northern California,” he said. Exactly how much climate shifts affect CV risk will vary by local conditions and resources, Kazi pointed out. Places like Phoenix, AZ, where weather has long been hot, though getting hotter, are better equipped to handle heat waves, for instance, that cities like Seattle, WA, where air conditioning is less widespread. “It’s not absolute temperature, it’s deviation from the norm that gets people in trouble with cardiovascular disease,” Kazi explained.

The same holds true for air pollution, where wildfires more severely augment risk for people living in places that typically enjoy clean air. “On average across the US, wildfires contribute more to particulate matter than transportation and energy. And yet we talk about wildfires by saying, ‘That affects California or New Mexico, it hurts the American West’—totally untrue. This particulate matter travels very far,” Kazi said. “So there are currently wildfire-related air-quality changes in Illinois and in states that have no wildfires within their boundaries. You see them because they’re transported out of the Canadian fires or western US fires. The smoke goes all the way.”

Cardiologists are, by nature, super evidence-driven. Michael B. Hadley

Chandan Devireddy, MD (Emory University Hospital, Atlanta, GA), said that as an interventional cardiologist, he hasn’t yet encountered any tangible effects of climate change in his daily practice. Atlanta’s currently facing a heat wave, for instance, yet it would be hard to detect a rise in STEMIs at an operator or institution level, even when larger effects might exist on a population level.

“People in their day-to-day lives and professions digest and filter what their immediate experience is,” he explained. With climate change, there can be “cognitive dissonance,” in that it’s “almost too big to wrap your head around.”

For some, it may seem that a few degrees’ difference in temperature won’t matter, Devireddy observed. But “when we have a certain homeostasis in blood pressure and vascular function, [with] the projection of the type of world humans may be living in 25 to 50 years from now, there’s a great concern that [it’s] going to be beyond our ability to compensate in many areas of the world,” said Devireddy.

What Cardiologists Can Do

Cardiologists can already take small steps toward integrating climate change considerations into their daily practice, Hadley said, though he acknowledged that many either aren’t ready to be or don’t want “to be responsible for the impact of the environment on their patients’ cardiovascular health.”

For at-risk patients, advice can be as simple as telling them to stay inside when there’s wildfire smoke or to wear masks when driving in rush-hour traffic, he suggested.

Kazi pointed out that another key demographic is patients taking diuretics, particularly if they’re also on an ACE inhibitor and/or beta-blocker, who are at risk of heat-related adverse events. “We should be telling our older patients to maybe hold their diuretic or halve their diuretic on the warmest days, especially if they’re living in a place that doesn’t have air conditioning, which is very common in New England but also on the West Coast,” he said.

Some advice can be found in a 2020 AHA scientific statement that addresses strategies individuals can use to avoid harm from air pollution, Münzel noted. Outdoor exercise, for instance, can be adjusted based on local conditions, and there are digital health apps to help gauge the level of risk, he said.

Change is hard, and some of these changes, at least in the beginning, may involve some sacrifices . . . when it comes to efficiency, speed, and whatnot.  Chandan Devireddy

Many of the things that can be done are “big picture.” As the BMJ Global Health paper outlines, there are strategies that simultaneously deter climate change and reduce CVD risk. For example, a transition to plant-based diets would reduce greenhouse gases produced by livestock while lowering people’s saturated fat intake. Expansion of green spaces and a shift toward active transportation like biking could reduce the ill effects of fossil fuels while increasing physical activity. Others include renewable energy and clean stoves for at-home use, both of which can reduce greenhouse gases and deforestation while decreasing people’s exposure to air pollution.

Medicine, as a whole, has a role to play. “First, healthcare systems must expand efforts in CVD prevention, reducing the burden of disease and resource-intensive interventions. In particular, providers should promote prompt telemedicine visits, local ambulatory care, and empowered self-care over inpatient management,” Hadley et al say. “Second, hospitals can reduce wasteful practices that may have health consequences, including overtreatment, overprescribing, and unnecessary interventions. Third, health systems should invest in disaster planning and early warning systems to prepare for waves of illness associated with extreme weather events, wildfire smoke, or climate refugees.”

And finally, they add, medical education should cover knowledge about environmental health and sustainable practice.

Devireddy emphasized that the “healthcare world and physicians need to take a tough look in the mirror.” As of 2016, the healthcare sector contributed 4% to 6% of greenhouse gas emissions, with Iceland and the United States leading the pack. Reducing this could have a profound impact, researchers have argued.

Although it can be easy to tell others what steps to take, “when we have to change our own behaviors and own practice patterns, it’s hard. Change is hard, and some of these changes, at least in the beginning, may involve some sacrifices to conveniences we’ve become accustomed to and expectations when it comes to efficiency, speed, and whatnot,” Devireddy noted. Until now, “we may have gotten accustomed to being able to do things at [what seems like] low cost because we haven’t acknowledged the true cost of what we do.”

This can’t be accomplished by a physician on their own, however, and instead requires system-wide change, he added. “I think it will be hard to solve this crisis if the solution is outlined under the umbrella of individual responsibility.”

Businesses that provide supplies to healthcare facilities can rise to the occasion as well. Devireddy said that at Emory they no longer use disposable surgical gowns apart from keeping extras on hand. Now, by working with a company, the “entire table drape, towels, bowls, the personal physician gowns are all recycled and sent back for sterilization and reused,” he said. “That’s just a small piece of the puzzle, but it does something.”

Another area to tackle are medical conferences, Devireddy proposed. The air travel that enables the advantages of in-person connections with colleagues also carries a carbon footprint. He said this begs the question, albeit a “tough one” given the potential for face-to-face professional growth, of: “Do we need as many meetings as are out there now?”

No Room for Nihilism

It may be hard for many to envision how climate change will upend all aspects of life, including heart health.

“Most cardiologists aren’t confronted daily with the effects of climate change on their patients,” Hadley said. Awareness tends to be location-dependent, though, such that those who are practicing in regions where climate has more-obvious changes are already having to adapt. He’s heard from colleagues in British Columbia, for example. “They’re having terrible wildfires out there, so doctors there are being asked by their patients: ‘What about this wildfire smoke, is this going to have an impact on my health?’ So doctors are having to respond to those sorts of questions and that’s putting pressure on them to understand these issues more,” Hadley said.

Both he and Vedanthan are members of the World Heart Federation’s air pollution expert group.  Vedanthan said there are currently discussions on how to put together a group dedicated to climate and cardiovascular health.

Hadley predicted interest in climate cardiology will continue to grow in tandem with a growing field: “Once you have that evidence base [to say], ‘Look, there are things we can actually do about this problem,’ then I think you’re going to really see a shift in perspective. Cardiologists are, by nature, super evidence-driven . . . and there’s a very high expectation for them before you’re going to have the buy-in from the average cardiologist.”

The most-important thing is really to try, both professionally and personally, to avoid a sense of hopelessness. Rajesh Vedanthan

This process of gathering data on environmental risks may take decades, Hadley cautioned. To protect patients will require knowing who’s most susceptible, how to predict climate-related events, and which interventions might mitigate the harm they pose. But what can’t be forgotten, he urged, is the continued need to prevent climate change itself, at least as much as possible, in order to reduce this health burden.

Together, these have downstream effects on things like supply chains, the food supply, and economic opportunities, creating the sorts of disruptions seen during the COVID-19 pandemic, he noted.  “Those obviously impact people’s lives and impact people’s health as well.”

Indeed, early on in the pandemic, the disruptions in care led to higher-than-expected CV mortality rates.

For Kazi, the whole experience of COVID-19 serves as “the most-prominent example in recent history of how we’ve got to stop thinking about cardiovascular disease as something that affects one patient at a time and [start] thinking about collective, systems-related issues that can improve or adversely affect people’s health.

“Systems-related thinking—the idea that we’re all in this together and that what affects one patient affects other patients, and in fact generations of patients—is what’s going to be needed to tackle the cardiovascular effects of climate change,” he said.

The supply chain disruptions spurred by COVID-19 are a reminder, too, of how interconnected the world is. Even now there are ongoing shortages specific to cardiology—like IV contrast media. In an earlier era, a saline shortage occurred when Hurricane Maria hit Puerto Rico. This is an argument that the field needs to plan for disruptions, especially since many cardiovascular treatments and procedures require both advanced technologies and human capital, Kazi said. “We can’t exclusively rely on centralized supply systems, even if they’re the most cost-effective way to do it, because they reduce our resilience to climate change.”

All of these conversations must take place—not just about risk factors and day-to-day patient care but also about the healthcare infrastructure and workforce—and cardiologists can inform the discussion, Kazi urged. “There’s a lot of climate change nihilism. . . . In the cardiovascular community, we should understand that in our world there are things we can do to help our patients and things we can plan for, because they are coming down the pike.”

For clinicians today, Vedanthan advised, “the most-important thing is really to try, both professionally and personally, to avoid a sense of hopelessness. I think that’s a major issue for me as an individual person as well as me as a professional physician.” While climate change at this point is likely inevitable, “I can’t now just be doom and gloom, I should really motivate [myself] to do something,” he said.