Fig. 10

Atrial strain, with examples of different zero-reference points. Figure (a) displays a typical LA strain waveform while (b) demonstrates measured atrial strain parameters. On the lower left (c), the onset of the QRS has been chosen as the zero-reference point. With this method, the atrium is at the beginning of the reservoir phase and initially expands, resulting in a positive deflection (c). On the right, the p-wave is used as the zero-reference, and consequently the first deflection is negative as the atrium enters the pump phase (d). Red vertical arrow demonstrates peak reservoir strain, blue vertical arrow the passive contraction strain (conduit phase), and green vertical arrow active pump (contractile) strain (c and d). The choice of zero-reference point will systematically alter the values obtained, with the QRS-onset methodology (c) leading to systematically larger strain values than the p-wave methodology