This study aims to determine whether skeletal muscle ultrasound is a useful technique for measuring low muscle mass in patients with heart failure (HF). Muscle wasting and abnormal muscle quality has been identified in patients with advanced HF and may contribute to patients' physical limitations. However assessments of body composition for patients with HF currently rely on the research tool of dual X-ray absorptiometry (DXA) for measurements of skeletal muscle mass, which is limited by cost, use of radiation, and the need for patients to be transported to the DXA scanner for imaging. Therefore this observational study is designed to validate a new approach that allows a safe and portable assessment of body composition.

The investigators will be recruiting both healthy subjects without HF, as well as subjects with either HF, a left ventricular assist device (LVAD) or cardiac transplantation. This is an observational study to validate the use of the BodyMetrix BX 2000 Pro ultrasound machine for the assessment of body composition, particularly muscle wasting. The ultrasound device received 501(k) designation from the FDA in 2009 for measurement of localized fat and muscle thickness. Participation will last for only one day, with approximately 2 hours of study activity in total:

1. For woman with child-bearing potential, potential participants will be required to undergo a urine pregnancy test prior to DXA imaging.
2. The investigators will record participant age, sex, height, weight and heart failure status.
3. Muscle ultrasound: investigators will make measurements at 7 positions on the arm, chest wall, and leg (participant's dominant side). Clear ultrasound gel will be applied to the skin, a BodyMetrix ultrasound probe placed against the skin, and the muscle thickness measurement made five times at each position. The gel is then wiped away.
4. Whole body dual X-ray absorptiometry (DXA) scan: the DXA scan involves lying on a flat and open scanner for approximately 5 minutes while an X-ray arm passes over the body to form a picture for whole body composition.
5. Handgrip strength: this involves the participant squeezing a handheld machine on three occasions in the dominant hand to measure grip strength.
6. 5 sit-to-stand test: investigators will time how long it takes for the participant to stand up from a seated position five times to assess lower body strength.

Inclusion Criteria:

1. Cohort 1: Healthy volunteers:

   • 18+ years
   • No history of heart failure
   • Not pregnant
   • Willing to take a urinary pregnancy test if there is a possibility of pregnancy
   • Able to freely provide informed consent

2. Cohort 2: Participants in our existing left ventricular assist device (LVAD) body composition study (#12026) who consent to undergo skeletal muscle ultrasound the same day as an LVAD body composition study visit that already includes the DXA and handgrip strength procedures:

   • Meet the eligibility criteria outlined in study #12026

3. Cohort 3: Patients with heart failure, an LVAD or heart transplantation

   • 18+ years
   • Not pregnant
   • Willing to take a urinary pregnancy test if there is a possibility of pregnancy

Exclusion Criteria:

1. Patients requiring temporary mechanical circulatory support
2. Pregnant women, or women who report there is a possibility they could be pregnant and decline to complete a pregnancy test

Three study populations will be recruited for this observational validation study:

Cohort 1: Healthy volunteers Cohort 2: Participants in our existing left ventricular assist device (LVAD) body composition study (#12026) who consent to undergo skeletal muscle ultrasound the same day as an LVAD body composition study visit that already includes the DXA and handgrip strength procedures Cohort 3: Patients with heart failure, an LVAD or heart transplantation Cohort 4: Inpatients with heart failure, an LVAD or heart transplantation, currently admitted to Tufts Medical Center