Transthoracic Sensor for Noninvasive Assessment of Left Ventricular Contractility: Validation in A Minipig Model of Chronic Heart Failure.

Background: Invasively measured left ventricular (LV) dP/dt is the accepted standard for measuring acute and chronic directional changes in LV contractility. Recently, we developed a noninvasive force sensor based on an accelerometer positioned on the chest, which measures the vibrations generated by isovolumic myocardial contraction. The aim of this paper was to compare noninvasive (accelerometer) versus invasive (LV dP/dt) indices of myocardial contractility in a chronic minipig model of pacinginduced heart failure (HF). Comparative assessment was performed both at rest and following dobutamine infusion. Methods: In adult male minipigs (n = 6), LV contractility was simultaneously assessed both invasively (LV dP/dt, Millar catheter) and noninvasively (accelerometer) at rest and following dobutamine (up to 7.5 mcg/kg/min), both before and after development of HF by pacing the LV at 180 beats/min for 3 weeks. Results: Invasive and noninvasive assessments were obtained in 24 conditions (12 at rest and 12 after dobutamine infusion). Sensor-based cardiac force changes were significantly related to positive peak LV dP/dtmax changes following dobutamine infusion both in normal (r = 0.88, P < 0.001) and failing heart (r = 0.89, P < 0.001). The force-frequency relation showed a tight correlation between invasive and noninvasive assessment (r = 0.68, P = 0.02). Conclusions: The force-frequency relation can be assessed noninvasively by a transthoracic sensor based on an accelerometer. The method can efficiently detect the development of resting dysfunction and the contractile reserve at different HF steps, with potential for wearable HF monitoring. (PACE 2010; 33:795-803)