Cardiac resynchronization therapy: could a numerical simulator be a useful tool in order to predict the response of the biventricular pacemaker synchronization?

Background and Objectives: Cardiac resynchronization therapy (CRT) can be considered as an established therapy for patients with moderate or severe heart failure (HF), depressed systolic function and a wide QRS complex. Biventricular stimulation through the CRT is applied at patients with an intra and/or inter-ventricular conduction delay. The goal of this technique is to resynchronize contraction between and within ventricles. A numerical model of the cardiovascular system, together with the numerical model of the biventricular pacemaker (BPM), can be an useful tool to study the better synchronization of the BPM in order to reduce the inter-ventricular and/or intra-ventricular conduction delay. Subjects and Methods: Within a group of patients which were representative of the most common disease etiologies of heart failure, seven patients, affected by dilated cardiomyopathy undergoing CRT with BPM, were studied and simulated using the numerical model of the cardiovascular system CARDIOSIM (c). The patients were submitted to echocardiographic evaluation (with pulsate Doppler and tissue Doppler imaging) and electrocardiography evaluation in order to evaluate intra-ventricular and/or inter-ventricular dyssynchrony. These evaluations were made three times: the first one before BPM implantation, the second and the third one respectively within seven days and six months after BPM implantation. Also haemodynamic parameters were measured. Using the software simulator, the pathological conditions before CRT, within seven days and within six months since CRT were reproduced for each patients in order to evaluate the following haemodynamic parameters: the end-systolic and end-diastolic left ventricular volume, the systolic pulmonary arterial pressure, the systolic, diastolic and mean aortic blood pressure and the ejection fraction. Also the trend of the left ventricular elastance was studied for each patient in order to evaluate the benefits produced by the CRT. Results: The results obtained by means the numerical simulator were in good agreement with clinical data measured on the patients. For each patient also the evolution of the left ventricular elastance was in accordance with the literature data. Conclusion: The cardiovascular numerical model seems to be a useful tool to study the synchronization of the BPM in order to reduce the inter-ventricular and/or intra-ventricular conduction delay and to reproduce the condition of a patient.