Abstract
Cardiac time intervals (CTIs) are sensitive markers of cardiac hemodynamics, and have previously been demonstrated to contain prognostic information consistent with conventional echocardiographic parameters. As LVEF decreases, aortic valve opening (AO) is delayed relative to ejection time (ET). HEMOTAG is the first known device to provide hemodynamics wirelessly via a smartphone using cardiac vibrations and an ECG signal transducer via multiple anterior chest wall electrodes. The purpose of this study was to assess LV function using CTIs from echo and HEMOTAG.
Within a 4 months period, 136 consecutive patients undergoing TTE were recruited at an outpatient office. CTIs by HEMOTAG and Echo along with TTE and cardiologist reports were recorded. Heart failure (HF) was characterized from echo variables according to standards from the 2016 ASE. Patients with reduced LVEF (< 53%) were analyzed according to systolic time ratio (STR) = AO/ET. A 2-way ANOVA was performed to assess the effects of heart failure group and CTI instrument on STR. Echo variables and HEMOTAG CTIs were compared among all HF groups. Furthermore, for patients with normal LVEF, echo variables and HEMOTAG CTIs were regressed against the number of positive conditions for HFpEF diagnosis to identify variables sensitive to severity or progression of HF. The data set was analyzed using MATLAB 2014a.
A total of 110 patients had normal LVEF, while 26 patients had reduced LVEF. Among patients with normal LVEF, 43 had normal diastolic function, 31 had diastolic dysfunction and 36 had indeterminate HF. Figure 1 shows STR mean±SE for each HF group and CTI instrument. Mean STR for HFrEF patients was significantly higher than normal, HFpEF and indeterminate patients (F(3,239) = 26.58, p < 0.0001); there was no significant effect of CTI instrument or interaction. For patients with normal LVEF, as the number of positive diastolic impairment conditions increased from zero (most healthy) to four (most certain diastolic impairment), the following HEMOTAG measures increased: AC (393 to 431 ms, p < 0.05), and ET (281 to 324 ms, p < 0.01).
STR from Echo and HEMOTAG successfully predicted reduced LVEF in a population of HF patients. Diastolic HF severity/progression was predicted by increasing AC from both Echo and HEMOTAG and from Echo ET. Our results also showed the effect of age on Echo and HEMOTAG measures which should be accounted for when interpreting measures for HF diagnosis.
