Is this cardiac measure the best predictor of early death?

Is this cardiac measure the best predictor of early death?

A simple measurement the cardiorespiratory sweet spot (COP) could predict how long someone will live or the severity of their heart failure, according to doctors supporting the assessment. COP is easier to achieve than cardiorespiratory measures that require people to exercise to the limit, advocates say; rather than running at full speed, someone can walk or jog lightly on a treadmill, with a COP value easily achieved.

But other doctors argue that maximal exercise testing has many prognostic benefits and that doctors should do everything in their power to push patients to exercise as hard as possible. In particular, the VO2 max captures the maximum amount of oxygen someone uses when exercising at their capacity and is the gold standard for measuring cardiovascular endurance.

COP is a measure of the minimum number of liters of air during breathing required to move one liter of oxygen through the bloodstream. The lower the COP, the better, because this means that someone is working less as hard as someone else to carry the the same amount of oxygen, denoting a more efficient interaction between the heart and lungs.

The COP for a fit person could be 15, about 20-25 for a healthy person and 35 for someone with heart failure, according to Claudio Gil Arajo, MD, PhD, director of research and education at CLINIMEX, a medicine clinic physics in Rio de Janeiro, Brazil.

“Maximum VO2 it is very important, this is indisputable. But when you use max VO2 in your daily life? Never,” Arajo said. But almost anyone can generate a COP.

Emerging uses for COP

“I can put someone on the treadmill or bike, and after 3 or 4 minutes I have the COP. It’s like a walking step,” Arajo said. Yet the values ​​are obtained with about half the effort as VO2 max. Other doctors argue that exercising at the edge of endurance offers unique clinical insights.

“We should do everything in our power to maximally exercise our patients. How long a patient is able to hold out for is really important,” said Anu Lala, MD, cardiologist specializing in the treatment of heart failure at the Mount Sinai Hospital in New York City. . A full-capacity exercise test provides useful information about heart rate, heart rate recovery, blood pressure, and ECG response to vigorous exercise, Lala added—all important clues to someone’s overall health.

Dr Claudio Gil Arajo

In 2012 Arajo co-authored a study that first defined COP, which is calculated by measuring the exhaled gases people produce during light exercise, perhaps up to the point where they start to sweat, and then dividing their capacity respiratory system for oxygen consumption every minute. The lowest value obtained during any exercise session is the COP.

Various studies show that higher COP values ​​are associated with more severe cardiac lesions in patients with congenital heart disease; higher levels of mortality in apparently healthy adult males; and with worse prognosis in patients with heart failure. All of these studies appeared within the last 7 months.

The mortality study, which Arajo co-authored, compared COP in more than 3,000 U.S. men and women who completed an exercise test from 1973 to 2018 and were followed for an average of 23 years. Although COP was introduced as a rating in 2012, calculating the value from tests prior to that date was possible because those tests captured the relevant respiration rate and oxygen uptake. In males aged 18 to 85, worse COP was significantly associated with an increased risk of early death. However, this finding didn’t hold true for women; Arajo noted that more research is needed to understand the discrepancy in the predictive power of COP based on gender.

In the heart failure study, all enrollees had heart failure and completed a COP test. People with the worst COPs also had the worst heart failure symptoms, but completing a physical rehabilitation program improved COP values ​​when the researchers measured them again. Arajo was also part of this studio, based in the Netherlands.

Dr Thijs Eijsvogels

“I think COP could become a new metric in clinical care,” said Thijs Eijsvogels, PhD, an exercise physiologist at Radboud University in Nijmegen and senior author of the heart failure study. That said, Eijsvogels said elite athletes will be increasingly interested in measuring VO2 max.

Lala agreed that tests like the COP have some value. His own work has shown that measuring the efficiency of someone’s breathing patterns for exhaling carbon dioxide, which can be done even without making people exercise at full strength, has prognostic value for patients with advanced heart failure. . Even so, she said she would like to see maximum effort tests used as much as possible.

“I care to say that we will settle for a metric that can be achieved at 50% of peak VO2 and then we don’t exercise our patients,” Lala said.

Arajo said he plans to continue measuring VO2 max but believes COP has utility for elite athletes as well. One of his patients is a frequent ironman competitor who competes well despite having a solid but unsurprising VO2 maximum level. But his COP is quite low, Arajo said, suggesting a particularly efficient interaction between his respiratory and cardiovascular systems.

“We have a new player in the game,” Arajo said.

The sources for this study report no relevant financial relationships.

Marcus A. Banks, MA, is a New York City-based journalist covering health news with a focus on new cancer research. His work appears in Medscape, Cancer Today, The Scientist, Gastroenterology & Endoscopy News, Slate, TCTMD and Spectrum.

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