Deep down, the heart drives the blood circulation system. However, its main pipe has a flexible wall and hence behaves non-linearly in response to the applied pressure. The transients in the heartbeat will gradually be smoothed while passing through the artery. Everywhere in the blood circulation system, the heartbeat can be found in a related but gradually different way. Ultimo, some non-invasive measurements at spread-out locations can be used to model an invasive measurement at the heart.
Circulation Diagnosis
Electrocardiogram (ECG) measurements need proper placement of a number of probes. If accurately executed, the signal can be detailed enough allowing more than 250 heart diseases to be detected by the trained nurse. The operation is costly and limited in use to special situations. For the early detection of heart failure, the procedure needs to be cheap and casual.
The heart signal is an intricate set of positive and negative pulses with intermediate planes: the PQRST complex (Figure 1a). It shows the ventricular activity and can be measured as electrical signals. As every peak and every plane has a functional meaning, any aberration has consequences. Though such deviations may be meaningful, they are not appearing often, if ever. Usually a Holter device needs to be carried for one or more days to catch a glimpse of the heart failure. With heart failure being a major cause of sudden death, a cheap and casual detection without special installations is required.
Figure 1.
The (a) PQRST vs. (b) PPG relationship
A healthy body is one in which the heart has no problems to bring blood to all parts of the body. Classical medicine targets the organs, but the body is much more. For instance, an early sign of diabetes is lack of blood flow in the toes. So general health needs to capture both the quality of the heart, usually read from ECG analysis, as well as the service ability of the blood circulation system, potentially found from a distributed Photoplethysmography (PPG) application.