PTC1 and PTC2: New indices of blood pressure waveforms and cardiovascular disease

Systolic and diastolic blood pressures provide information about cardiovascular disease (CVD) but are only extremes of the pressure waveform during the cardiac cycle. We developed summaries of the pressure decay, called PTC1 and PTC2, that are related to arterial compliance and to an existing proprietary summary that has been shown to predict CVD. We derived the summaries from a Windkessel model (consisting of a decaying exponential plus a dampened cosine, with an intercept so they are independent of calibration with blood pressure, unlike the proprietary measures), and we estimated them using nonlinear least squares with standard, free software. Among 6,228 adults from the Multi-Ethnic Study of Atherosclerosis, initially free of CVD in 2000-2002, mean PTC2 was 94 (standard deviation, 46) milliseconds. During median 15-year follow-up, there were 911 CVD events (including 609 incidents of coronary heart disease and 270 strokes). One-standard-deviation higher PTC2 was associated with 17% (95% confidence interval: 10, 24) lower CVD risk, after adjustment for traditional risk factors. Results were similar for PTC1. PTC1 and PTC2 are relatively straightforward to compute and add information beyond traditional risk factors for prediction of CVD. Our work enables others to replicate and extend our results with waveforms from any suitable device.