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.
