Pulse arrival time accurately detects pacing-induced mechanical alternans

Accurate cardiac risk stratification is crucial for preventing cardiac death, but still remains an unmet need. Mechanical alternans (MA), an oscillation of blood pressure that occurs on a beat-to-beat basis, has been recognized as a marker of cardiac instability and is associated with an increased risk of cardiac death. However, the use of MA for risk stratification is currently limited by the invasiveness and costs of continuous blood pressure monitoring. A non-invasive, cuffless and affordable method to detect MA is therefore highly desirable. The pulse transit time (PTT) and the pulse arrival time (PAT) are promising techniques for continuous blood pressure monitoring, particularly for detecting short-term blood pressure changes. In this work, we hypothesized that PAT, measured as the interval between the R-wave in the ECG and a distal arterial pulse, can be used to accurately track fast beat-to-beat blood pressure dynamics and detect MA. A total of 42 ECG and femoral arterial pressure recordings from 12 patients with normal ventricles were analyzed. Patients were instructed to breath at a fixed respiratory rate and MA was induced by ventricular pacing. Both MA and PAT alternans were detected using spectral analysis. MA was present in 69% of blood pressure recordings (n=29). ROC analysis showed that PAT accurately detected MA, with an area under the curve was equal to AUC = 0.94. The optimal threshold for detecting MA by using PAT provided 90% sensitivity and 85% specificity. In conclusion, this study demonstrates that PAT can be used to accurately detect pacing-induced MA and may represent a first step toward non-invasive, cuff-less and affordable MA screening for cardiac risk assessment.