1 Division of Cardiology, Department of Pediatrics, Stanford University, Palo Alto, California, USA.
2 Division of Biomedical Informatics Research, Department of Medicine, Quantitative Sciences Unit, Stanford University, Palo Alto, California, USA.
3 Division of Cardiology, Department of Pediatrics, Stanford University, Palo Alto, California, USA; Department of Bioengineering, Stanford University, Palo Alto, California, USA. Electronic address: jaf@stanford.edu.