Systolic time intervals assessed from analysis of the carotid pressure waveform

The timing of mechanical cardiac events is usually evaluated by conventional echocardiography as an index of cardiac systolic function and predictor of cardiovascular outcomes. We aimed to measure the systolic time intervals, namely the isovolumetric contraction time (ICT) and pre-ejection period (PEP), by arterial tonometry.

Sixty-two healthy volunteers (age 47  ±  17 years) and 42 patients with heart failure and reduced ejection fraction were enrolled (age 66  ±  14 years). Pulse waves were recorded at the carotid artery by arterial tonometry together with simultaneous aortic transvalvular flow by Doppler-echocardiography, synchronized by electrocardiographic gating. The ICT was determined from the time delay between the electrical R wave and the carotid pressure waveform, after adjustment for the pulse transit time from the aortic valve to the carotid artery site, estimated by an algorithm based on the carotid-femoral pulse wave velocity. The PEP was evaluated by adding the electrical QR duration to the ICT.

The ICT derived from carotid pulse wave analysis was closely related to that measured by echocardiography (r  =  0.90, p  <  0.0001), with homogeneous distribution in Bland-Altman analysis (mean difference and 95% confidence interval  =  0.2 from  -14.2 to 14.5 ms). ICT and PEP were higher in cardiac patients than in healthy volunteers (p  <  0.0001). The ratio between PEP and left ventricular ejection time was related to the ejection fraction measured with echocardiography (r  =  0.555, p  <  0.0001).

The timing of electro-mechanical cardiac events can be reliably obtained from the carotid pulse waveform and carotid-femoral PWV, evaluated using arterial tonometry. Systolic time intervals assessed with this approach showed good agreement with measurements performed with conventional echocardiography and may represent a promising additional application of arterial tonometry.