Climate change could spell trouble for those with heart failure, a new study suggests.
When the temperatures soared in France during the summer of 2019, the heat wave appears to have worsened the conditions of heart failure patients, researchers report.
"The finding is timely, given the heat waves again this year," said study author Dr. François Roubille, head of the intensive care unit at Montpellier University Hospital in France.
The study, published Sept. 22 in ESC Heart Failure, a journal of the European Society of Cardiology, found that warmer temps were associated with weight loss, which worsens heart failure.
"The weight loss we observed in people with heart failure may lead to low blood pressure, especially when standing up, and renal failure, and is potentially life-threatening," Roubille said. "With rising temperatures forecast for the future, clinicians should be ready to reduce the dose of diuretics when weight loss occurs."
The researchers hypothesized that a heat wave affects the fluid intake of a heart failure patient.
"When healthy people drink more fluids during hot weather, the body automatically regulates urine output. This does not apply to patients with heart failure because they take diuretics," Roubille explained in a journal news release.
With heart failure, a patient's heart does not pump blood throughout the body as well as it should. This can cause shortness of breath and fluid build-up in the lungs, legs and abdomen.
Doctors tend to monitor patients' weight gain because it can suggest congestion and may require hospitalization.
Patients with heart failure are prescribed diuretics to increase urine output, which can help with their symptoms of breathlessness and swelling. They may be told to increase their diuretic dose if they're experiencing breathlessness, swelling or sudden weight gain.
This study included 1,420 patients with chronic heart failure and looked at their body weight and the air temperature between June 1 and Sept. 20, 2019, a time frame that included two heat waves.
The researchers used a national tele-monitoring system to remotely gather information on weight and symptoms, with patients weighting themselves daily on a scale that sent data to the clinic.
The patients also reported daily symptoms including edema [swelling], fatigue, breathlessness and cough, with answers sent automatically via a device to the clinic.
The researchers considered patient weight, ambient weather temperature on the same day, and temperature two days prior to the weight measurement. They found a strong relationship between temperature and weight, with weight dropping as temperature rose.
The strongest connection was found with temperatures two days prior to the weight measurement.
"The weight loss we observed during the heat wave was clinically relevant. Patients weighing [179 pounds] lost [3.3 pounds] in a short period of time. We were surprised to see that weight dropped with hot temperatures, as we had expected the opposite," Roubille said.
Given the findings, tele-monitoring systems also need to alert clinicians of weight loss in heart failure patients, Roubille said, especially during heat waves.
"In addition, systems could notify patients losing weight that it may be due to the heat and they should contact their health care provider about reducing the dose of diuretics," Roubille said.
"For heart failure patients not monitored remotely, a good rule of thumb would be to contact a health care professional if weight drops by [4.4 pounds] during a heat wave for advice on adjusting diuretic medication," he advised. "Reacting early should help us to prevent complications."
The American Heart Association has more on heart failure.
SOURCE: European Society of Cardiology, news release, Sept. 22, 2022