Estimation of coronary wave intensity analysis using noninvasive techniques and its application to exercise physiology

Wave intensity analysis (WIA) has found particular applicability in the coronary circulation where it can quantify traveling waves that accelerate and decelerate blood flow. The most important wave for the regulation of flow is the backward-traveling decompression wave (BDW). Coronary WIA has hitherto always been calculated from invasive measures of pressure and flow. However, recently it has become feasible to obtain estimates of these waveforms noninvasively. In this study we set out to assess the agreement between invasive and noninvasive coronary WIA at rest and measure the effect of exercise. Twenty-two patients (mean age 60) with unobstructed coronaries underwent invasive WIA in the left anterior descending artery (LAD). Immediately afterwards, noninvasive LAD flow and pressure were recorded and WIA calculated from pulsed-wave Doppler coronary flow velocity and central blood pressure waveforms measured using a cuff-based technique. Nine of these patients underwent noninvasive coronary WIA assessment during exercise. A pattern of six waves were observed in both modalities. The BDW was similar between invasive and noninvasive measures [peak: 14.9 +/- 7.8 vs. -13.8 +/- 7.1 x 10(4) W.m(-2).s(-2), concordance correlation coefficient (CCC): 0.73, P < 0.01; cumulative: -64.4 +/- 32.8 vs. -59.4 +/- 34.2 x 10(2) W.m(-2).s(-1), CCC: 0.66, P < 0.01], but smaller waves were underestimated noninvasively. Increased left ventricular mass correlated with a decreased noninvasive BDW fraction (r = -0.48, P < 0.02). Exercise increased the BDW: at maximum exercise peak BDW was -47.0 +/- 29.5 x 10(4) W.m(-2).s(-2) (P < 0.01 vs. rest) and cumulative BDW -19.2 +/- 12.6 x 10(3) W.m(-2).s(-1) (P < 0.01 vs. rest). The BDW can be measured noninvasively with acceptable reliably potentially simplifying assessments and increasing the applicability of coronary WIA.