Chronic lack of exercise – dubbed “exercise deficiency” – is associated with cardiac atrophy, reduced cardiac output and chamber size, and diminished cardiorespiratory fitness (CRF) in a subgroup of patients with heart failure with preserved ejection fraction (HFpEF), researchers say.
Increasing the physical activity levels of these sedentary individuals could be an effective preventive strategy, particularly for those who are younger and middle-aged, they suggest.
Thinking of HFpEF as an exercise deficiency syndrome leading to a small heart “flies in the face of decades of cardiovascular teaching, because traditionally, we’ve thought of heart failure as the big floppy heart,” Andre La Gerche, MBBS, PhD, of the Baker Heart and Diabetes Institute, Melbourne, told this news organization.
“While it is true that some people with HFpEF have thick, stiff hearts, we propose that another subset has a normal heart, except it’s small because it’s been underexercised,” he said.
The article, published online as part of a Focus Seminar series in the Journal of the American College of Cardiology, has “gone viral on social media,” Jason C. Kovacic, MBBS, PhD, of the Victor Chang Cardiac Research Institute, Darlinghurst, Australia, told this news organization.
Dr. Kovacic is a JACC section editor and the coordinating and senior author of the series, which covers other issues surrounding physical activity, both in athletes and the general public.
‘Coin-dropping moment’
To support their hypothesis that HFpEF is an exercise deficiency in certain patients, Dr. La Gerche and colleagues conducted a literature review that highlights the following points:
- There is a strong association between physical activity and both CRF and heart function.
- Exercise deficiency is a major risk factor for HFpEF in a subset of patients.
- Increasing physical activity is associated with greater cardiac mass, stroke volumes, cardiac output, and peak oxygen consumption.
- Physical inactivity leads to loss of heart muscle, reduced output and chamber size, and less ability to improve cardiac performance with exercise.
- Aging results in a smaller, stiffer heart; however, this effect is mitigated by regular exercise.
- Individuals who are sedentary throughout life cannot attenuate age-related reductions in heart size and have increasing chamber stiffness.
“When we explain it, it’s like a coin-dropping moment, because it’s actually a really simple concept,” Dr. La Gerche said. “A small heart has a small stroke volume. A patient with a small heart with a maximal stroke volume of 60 mL can generate a cardiac output of 9 L/min at a heart rate of 150 beats/min during exercise – an output that just isn’t enough. It’s like trying to drive a truck with a 50cc motorbike engine.”
“Plus,” Dr. La Gerche added, “exercise deficiency also sets the stage for comorbidities such as obesity, diabetes, and high blood pressure, all of which can ultimately lead to HFpEF.”
Considering HFpEF as an exercise deficiency syndrome has two clinical implications, Dr. La Gerche said. “First, it helps us understand the condition and diagnose more cases. For example, I think practitioners will start to recognize that breathlessness in some of their patients is associated with a small heart.”
“Second,” he said, “if it’s an exercise deficiency syndrome, the treatment is exercise. For most people, that means exercising regularly before the age of 60 to prevent HFpEF, because studies have found that after the age of 60, the heart is a bit fixed and harder to remodel. That doesn’t mean you shouldn’t try after 60 or that you won’t get benefit. But the real sweet spot is in middle age and younger.”