Linking diastolic function to cardiac exercise performance in heart failure with preserved ejection fraction: a virtual patient study

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NWO-ZonMw Background The relative impact of left ventricular (LV) diastolic dysfunction (LVDD) and impaired left atrial (LA) function on cardiac exercise performance (CEP) in heart failure with preserved ejection fraction (HFpEF) remains largely unknown Purpose To elucidate the relative effects of LVDD and impaired LA function on hemodynamics at rest and on cardiac performance during exercise by performing virtual HFpEF patient simulations. Methods Using a well-validated cardiovascular system model (CircAdapt), impaired LV relaxation was simulated by increasing the rate of myocardial relaxation (tau) from 35 to 65 ms. To study the effect of moderate and sever LV myocardial stiffness increase, LV end-diastolic elastance was increased from 0.15 mmHg/ml to 0.60 mmHg/ml and 2.00 mmHg/ml, respectively. In each simulation, LV diastolic function at rest (cardiac output (CO) and heart rate (HR) of 5.1 l/min and 70 bpm, respectively) was assessed using LV ejection fraction (LVEF), mitral E/A ratio, maximum LA volume (LAV), and mean left atrial (LA) pressure (mLAP). To investigate the relative effect of these cardiac abnormalities on exercise capacity, CO and HR were gradually increased using a fixed CO-HR relationship until mLAP exceeded a threshold pressure of 35 mmHg, which was assumed to be a physiological limit of exercise intensity. Results Simulations showed that regardless of the modelled LV and LA function, LVEF was preserved (>50%). Impaired LV relaxation function was associated with decreased E/A-ratio and a small increase in mLAP at rest, regardless of LA function. Increased LV passive stiffness resulted in increased E/A-ratio, LA dilation and markedly elevated mLAP at rest, regardless of LA function (Figure: top-left). Impaired LA function resulted in reduced A-peak velocity, and increased E/A–ratio, LAV and mLAP at rest regardless of LV function (Figure: top-right) Exercise simulations showed that increased LV passive stiffness exerts a stronger exercise-limiting effect than impaired LV relaxation function, in particular when LA function is impaired (Figure: bottom). Conclusions Through simple and well-controlled variations in LV and LA function, we were able to simulate virtual HFpEF patients with a wide range of LVDD severities at rest, preserved LVEF, and reduced cardiac exercise performance. In general, our simulations suggest that increased LV passive stiffness, rather than impaired LV relaxation function, reduces exercise tolerance, especially in the presence of LA dysfunction. Abstract Figure. Simulating rest & exercise hemodynamics