Effect of regional left ventricular dysfunctions on continuous flow lvad assistance

Objectives: Patients with severe heart failure are candidates for LVAD implantation. Left ventricular (LV) dysfunction is related to abnormal ventricular region (AVR) extension that could be affected by systolic abnormalities, diastolic abnormalities and electro-mechanical dissynchrony. The aim of this work is to study the effect of an AVR on hemodynamics during LVAD assistance. Methods: A lumped parameter model of the cardiovascular system was updated. Circulatory sections are described by Windkessel models. Atria, ventricular free walls and interventricular septum are described by variable elastance models driven by ECG times. LV free wall is represented by two variable elastance models to simulate an AVR. A model of parallel continuous flow LVAD was also implemented. Starting from a simulated pathological condition, the effect of LVAD on hemodynamics was studied changing: 1) AVR systolic elastance, 2) AVR diastolic elastance 3) the contraction delay between the two parts of the LV free wall and 4) AVR extension. Results: All experiments compare the relative changes between pathological and assisted conditions giving their mean values. The variable that is more influenced by AVR changing is the external work. The presence of an AVR dissynchrony (0÷150ms) influences mean aortic pressure (+10%). The changing of AVR systolic function (0.1÷1 mmHg/mL) affects both LV end systolic volume (+6%) and cardiac output (+12%), while the changing of AVR diastolic function (0.01÷0.2 mmHg/mL) affects left atrial pressure (-19%) and LV end diastolic volume (-14%). The presence of an AVR diastolic dysfunction could expedite the occurrence of right ventricular heart failure. This fact is more evident if a diastolic septum dysfunction occurs together with a moderate AVR diastolic dysfunction. Conclusions: The model could be useful to estimate the role of different parameters on LVAD performance and could be used to support the clinical decision adapting the LVAD assistance to specific patient conditions.