Figure 1

Isovolumic contraction force and second heart sound (S2) amplitude. A Micro-Electro-Mechanical Systems (MEMS) accelerometer is temporarily positioned in the mid-sternal precordial region before starting the scheduled stress test in all patients. A peak detection algorithm, synchronized with the ECG, scans the first 150 ms following the R wave to record the isovolumic contraction force vibration and then the interval before the following R wave to record the second heart sound amplitude (S2, pink symbol). All the parameters are acquired as instantaneous values at baseline and during stress. The data can be also read remotely by a wireless bluetooth sensor network, with reliable continuous remote monitoring 'See additional file 1: Appendix'.