Extreme heat is hard on all of us, but researchers at the Institute for Exercise and Environmental Medicine (IEEM) on the Texas Health Presbyterian Dallas campus suspect patients with heart failure may be especially vulnerable. They've launched a study into how and why.
Craig Crandall, Ph.D. heads the institute's Thermal and Vascular Physiology Laboratory.
He told KERA's Sam Baker the idea for the study began with existing epidemiological data.
Crandall: We see from these data that some of the individuals that are most susceptible to heat wave conditions, both as far as things like hospitalization, as well as death, are individuals who have heart failure.
So, we're very interested in identifying what is it about heart failure that results in these individuals being at greater risk during a heat wave or extreme heat condition, and what can we do to reduce that risk in these individual.
Baker: Give me an example of how bad a situation this is. We get into the high temperatures that we have in Texas, June, July, certainly August. What becomes of people with heart failure during this time?
Crandall: Let's just say, for example, the apartment, the air conditioner, no longer is working. We believe their core temperatures will go up higher and that will put more strain and stress on the heart and ultimately result in some sort of a hospitalization type of symptoms and I guess ultimately death.
We should make it clear that if somebody who has heart failure is in an air conditioned space, they're just fine.
We become concerned, if they choose to not use the air conditioner. Perhaps they have some cognitive disabilities and are not turning on the air conditioner, or their air conditioner is broken, or perhaps they're concerned about paying for the bill. And so they don't turn it on.
The bottom line is that they get hotter. That puts more strain on the heart that results in potentially, culminating the extreme would be to death.
Baker: Tell me about this study, and how it works.
Crandall: We've got a climate chamber where we can simulate really any heat wave that we want. What we're currently focusing in is on a Pacific Northwest heat wave where the temperature is quite warm, upwards to 100 degrees and it's relatively dry.
We'll take an individual who we've diagnosed who has heart failure and we will put them inside the environmental chamber for three hours. Of course, we're monitoring everything throughout this time, so it's quite safe. We're monitoring their heart function, we're measuring their core temperature, we're monitor their skin temperature, and we want to see how much stress this particular heat environment places on the heart.
We are doing some echocardiography-based measurements before they get into the chamber, and then near the end of the chamber exposure, so we can actually look at changes in heart function and how this simulated heat wave affects heart function from all these different measures.
Baker: What have you found so far?
Crandall: Well, we've not collected enough data. We started Jan. 1. It's premature to know what's going to happen.
There is some basic data that suggests that individuals who have heart failure don't increase their skin blood flow appropriately, which is one of the measurements that we are going to obtain. And if they don't increase their blood flow and if they sweat appropriately, that will lead to their core temperatures being higher.
So some basics that we and others have collected show individuals with heart failure do not appropriately increase skin blood flow or sweating, which we believe will result in them becoming hotter, which will place greater strain on the heart.
And then we're following it up with different cooling modalities. We want to see what can we do with individuals who are experiencing a heat wave to reduce how high their body temperature becomes.
And so we are exploring different cooling modalities with water, perhaps something as simple as spring water on an individual, or taking a t-shirt and immersing it in water and then having an individual put that t-shirt on. are these effective in reducing the risk of individuals who have heart failure during a heatwave scenario?
RESOURCES:
Heart problems and the heat: What to know and do
CDC: Clinical Overview of Heat and Cardiovascular Disease
Extremely hot and cold days may pose higher cardiovascular death risk
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