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Background Electronic cigarettes have gained popularity as a nicotine delivery system, which has been recommended by some as an aid to help people quit traditional smoking. The potential long‐term effects of vaping on the cardiovascular system, as well as how their effects compare with those from standard cigarettes, are not well understood. The intrinsic frequency (IF) method is a systems approach for analysis of left ventricle and arterial function. Recent clinical studies have demonstrated the diagnostic and prognostic value of IF. Here, we aim to determine whether the novel IF metrics derived from carotid pressure waveforms can detect effects of nicotine (delivered by chronic exposure to electronic cigarette vapor or traditional cigarette smoke) on the cardiovascular system. Methods and Results One hundred seventeen healthy adult male and female rats were exposed to purified air (control), electronic cigarette vapor without nicotine, electronic cigarette vapor with nicotine, and traditional nicotine‐rich cigarette smoke, after which hemodynamics were comprehensively evaluated. IF metrics were computed from invasive carotid pressure waveforms. Standard cigarettes significantly increased the first IF (indicating left ventricle contractile dysfunction). Electronic cigarettes with nicotine significantly reduced the second IF (indicating adverse effects on vascular function). No significant difference was seen in the IF metrics between controls and electronic cigarettes without nicotine. Exposure to electronic cigarettes with nicotine significantly increased the total IF variation (suggesting adverse effects on left ventricle‐arterial coupling and its optimal state), when compared with electronic cigarettes without nicotine. Conclusions Our IF results suggest that nicotine‐containing electronic cigarettes adversely affect vascular function and left ventricle‐arterial coupling, whereas standard cigarettes have an adverse effect on left ventricle function.

IntroductionThe wave condition number (WCN) is a non-dimensional number that determines the state of arterial wave reflections. WCN is equal to HR × Leff/PWV where HR, Leff, and PWV are the heart rate, effective length, and pulse wave velocity, respectively. It has been shown that a value of WCN = 0.1 indicates the optimum state of arterial wave reflection in which left ventricle workload is minimized. The pressure wave, flow wave, and PWV are all required to compute WCN, which may limit the potential clinical utility of WCN. The aims of this study are as follows: (1) to assess the feasibility of approximating WCN from the pressure waveform alone (WCNPinf), and (2) to provide the proof-of-concept that WCNPinf can capture age related differences in arterial wave reflection among healthy women and men.MethodsPreviously published retrospective data composed of seventeen patients (age 19–54 years; 34.3 ± 9.6) were used to assess the accuracy of WCNPinf. The exact value of WCN was computed from PWV (measured by foot-to-foot method), HR, and Leff. A quarter wavelength relationship with minimum impedance modulus were used to compute Leff. WCNPinf was calculated using HR and the reflected wave arrival time. Previously published analyses from a healthy subset of the Anglo-Cardiff Collaborative Trial (ACCT) study population were used to investigate if non-invasive WCNPinf captures age related differences in arterial wave reflection among healthy women and men.ResultsA strong correlation (r = 0.83, p-value