2.6 Feasibility of Aortic Wave Intensity Analysis from Sequentially Acquired Cardiac Mri and Non-Invasive Central Blood Pressure

Abstract

Background

Wave intensity analysis (WIA) in the aorta offers important clinical and mechanistic insights but is difficult non-invasively. We performed WIA by combining high temporal resolution cardiovascular magnetic resonance (CMR) flow velocity and non-invasive central blood pressure (BP) waveform data.

Method

206 healthy volunteers (36 ± 11 years, 47% male) underwent sequential phase contrast CMR (Siemens Aera 1.5T, 1.97 × 1.77 mm², ~9 ms temporal resolution) and supra-systolic oscillometric central BP (Uscom Ltd BP+) measurement. Velocity (U) and central pressure (P) waveforms (200 Hz) were aligned using the wave foot, and local wave speed was calculated both from the P-U slope during early systole (c) and the sum of squares method (cSS) (Figure 1), and compared with CMR aortic arch pulse wave velocity (PWV) by transit time.

Results

The peak intensity of the initial compression wave (dI+1), backward compression wave (dI-) and protodiastolic decompression wave (dI + 2) were 69.5 ± 28, −6.6 ± 4.2 and 6.2 ± 2.5 W/m² respectively. PWV correlated with c or cSS (r = 0.60, and 0.68 respectively; bias −1.3 [limits of agreement: −3.8 to 1.2 m/s], and bias −0.64 [limits of agreement: −3.0 to 1.7 m/s] respectively), Figure 1.

Conclusion

Wave intensity patterns and values are similar to those measured using invasive methods. Local wave speed showed good agreement with PWV. CMR and central blood pressure provides a novel non-invasive technique for performing wave intensity analysis and is feasible for large scale studies.