Establishing a Non-invasive Method to Measure Your Heart's Performance

Establishing a Non-invasive Method to Measure Heart Performance

The purpose of the study is to evaluate a new way to examine cardiac function, using software developed at Caltech. The experimental device is software loaded on an iPhone. The iPhone is used to capture a pulse (waveform) by simply placing the iPhone lightly over the neck where the carotid pulse can be felt. In this study the information collected from the iPhone app is compared to cardiac function data obtained from the current gold standard for measuring cardiac function, cardiac magnetic resonance imaging (MRI). Subjects referred from cardiologists will also generally have echocardiography information available for comparison with the iPhone app. For the study, subjects will have completely non-invasive studies done in one setting: The iPhone app to capture the waveforms (over carotid and radial (wrist) arteries), tonometry (another non-invasive method using a modified stethoscope), standard pulse oximetry, followed by a 30 minute MRI examination of the heart. A second complete study will be done about 6 months after the first. The complete study session takes about 1.5 hours.

Investigators at Caltech have developed an iPhone-based application that allows them to capture an arterial waveform using the iPhone camera held over the skin. Then based on the captured waveform and previous laboratory experiments and models, the investigators are able to calculate ejection fraction, the percentage of blood that goes out of the heart into the circulation with each beat. Previous studies suggested that the iPhone app measurements of ejection fraction were similar to those obtained with traditional cardiac echocardiography. In the current study the iPhone app measures are being compared to ejection fraction obtained using cardiac MRI. The iPhone also measures other physical properties of the heart and aorta that the investigators call "intrinsic frequencies". Using healthy subjects they have established the normal pattern/range of intrinsic frequencies, and in this study, a more diverse population of subjects (some with heart disease) will be studied, to determine how intrinsic frequency measures compare to traditional clinical measures of cardiac function.

Inclusion Criteria:

• Adult age 18-90, outpatients

Exclusion Criteria:

• Inability to lie flat for 30 minutes with periodic breath holding
• Metal implants or other standard contraindications to MRI
• Acute cardiac decompensation (active chest pain, shortness of breath)
• Hypotension (SBP<90 mm Hg)
• Claustrophobia
• Patient too large to fit in closed MRI