Abstract
BackgroundThe real-time and continuous assessment of left ventricular (LV) myocardial contractility through an implanted device is a clinically relevant goal. Transvalvular impedance (TVI) is an impedentiometric signal detected in the right cardiac chambers that changes during stroke volume fluctuations in patients. However, the relationship between TVI signals and LV contractility has not been proven. We investigated whether TVI signals predict changes of LV inotropic state during clinically relevant loading and inotropic conditions in swine normal heart.MethodsThe assessment of RVTVI signals was performed in anesthetized adult healthy anesthetized pigs (n = 6) instrumented for measurement of aortic and LV pressure, dP/dtmax and LV volumes. Myocardial contractility was assessed with the slope (Ees) of the LV end systolic pressure-volume relationship. Effective arterial elastance (Ea) and stroke work (SW) were determined from the LV pressure-volume loops. Pigs were studied at rest (baseline), after transient mechanical preload reduction and afterload increase, after 10-min of low dose dobutamine infusion (LDDS, 10 ug/kg/min, i.v), and esmolol administration (ESMO, bolus of 500 µg and continuous infusion of 100 µg·kg−1·min−1).ResultsWe detected a significant relationship between ESTVI and dP/dtmax during LDDS and ESMO administration. In addition, the fluctuations of ESTVI were significantly related to changes of the Ees during afterload increase, LDDS and ESMO infusion.ConclusionsESTVI signal detected in right cardiac chamber is significantly affected by acute changes in cardiac mechanical activity and is able to predict acute changes of LV inotropic state in normal heart.
Highlights
The ideal index of ventricular performance, which describes the pumping properties of the left ventricle, should be sensitive to changes of left ventricular (LV) inotropic state, independent of loading conditions, reproducible and safe [1]
Left ventricular pressure-volume (PV) loops are considered to be the gold standard for complete hemodynamic assessment during each cardiac cycle [2,3] and are widely used in research to evaluate the LV inotropic state and to quantify mechanical ventricular dyssynchrony in large animal model [4,5] and humans [6,7]
We accurately evaluated the feasibility of conductance catheter-derived P-V loops and Transvalvular impedance (TVI) waveform during transient reduction of preload, acute increase of LV afterload, during low dose dobutamine stress (LDDS) and following esmolol infusion
Summary
The ideal index of ventricular performance, which describes the pumping properties of the left ventricle, should be sensitive to changes of left ventricular (LV) inotropic state, independent of loading conditions, reproducible and safe [1]. The PV loops assessment by conductance catheter is an invasive and complex approach, and its clinical application does not enable a permanent monitoring of ventricular contractility in patients with pacemaker implants. The continuous real-time assessment of the LV myocardial contractility by an implanted device could provide useful information to calibrate the electrical stimulation in proportion to the real inotropic state of the heart and to monitor maladaptive hemodynamic response to electrical therapy of the heart [8] and the overall patient care [9]. The real-time and continuous assessment of left ventricular (LV) myocardial contractility through an implanted device is a clinically relevant goal. We investigated whether TVI signals predict changes of LV inotropic state during clinically relevant loading and inotropic conditions in swine normal heart
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