title: Recognition of Fibrotic Infarct Density by the Pattern of Local Systolic-Diastolic Myocardial Electrical Impedance.
abstract: Myocardial electrical impedance is a biophysical property of the heart that is influenced by the intrinsic structural characteristics of the tissue. Therefore, the structural derangements elicited in a chronic myocardial infarction should cause specific changes in the local systolic-diastolic myocardial impedance, but this is not known. This study aimed to characterize the local changes of systolic-diastolic myocardial impedance in a healed myocardial infarction model. Six pigs were successfully submitted to 150 min of left anterior descending (LAD) coronary artery occlusion followed by reperfusion. 4 weeks later, myocardial impedance spectroscopy (1-1000 kHz) was measured at different infarction sites. The electrocardiogram, left ventricular (LV) pressure, LV dP/dt, and aortic blood flow (ABF) were also recorded. A total of 59 LV tissue samples were obtained and histopathological studies were performed to quantify the percentage of fibrosis. Samples were categorized as normal myocardium (<10% fibrosis), heterogeneous scar (10-50%) and dense scar (>50%). Resistivity of normal myocardium depicted phasic changes during the cardiac cycle and its amplitude markedly decreased in dense scar (18 ± 2 Ω·cm vs. 10 ± 1 Ω·cm, at 41 kHz; P < 0.001, respectively). The mean phasic resistivity decreased progressively from normal to heterogeneous and dense scar regions (285 ± 10 Ω·cm, 225 ± 25 Ω·cm, and 162 ± 6 Ω·cm, at 41 kHz; P < 0.001 respectively). Moreover, myocardial resistivity and phase angle correlated significantly with the degree of local fibrosis (resistivity: r = 0.86 at 1 kHz, P < 0.001; phase angle: r = 0.84 at 41 kHz, P < 0.001). Myocardial infarcted regions with greater fibrotic content show lower mean impedance values and more depressed systolic-diastolic dynamic impedance changes. In conclusion, this study reveals that differences in the degree of myocardial fibrosis can be detected in vivo by local measurement of phasic systolic-diastolic bioimpedance spectrum. Once this new bioimpedance method could be used via a catheter-based device, it would be of potential clinical applicability for the recognition of fibrotic tissue to guide the ablation of atrial or ventricular arrhythmias.
authors.affiliation: Department of Cardiology, Hospital de la Santa Creu i Sant Pau, Institut d'Investigació Biomèdica - Sant Pau, Universitat Autònoma de Barcelona Barcelona, Spain.
authors.forename: Gerard
authors.initials: G
authors.lastname: Amorós-Figueras
authors.affiliation: Department of Cardiology, Hospital de la Santa Creu i Sant Pau, Institut d'Investigació Biomèdica - Sant Pau, Universitat Autònoma de Barcelona Barcelona, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Jorge
authors.affiliation: Electronic and Biomedical Instrumentation Group, Department of Electronics Engineering, Universitat Politècnica de Catalunya Barcelona, Spain.
authors.forename: Tomás
authors.initials: T
authors.lastname: García-Sánchez
authors.affiliation: Electronic and Biomedical Instrumentation Group, Department of Electronics Engineering, Universitat Politècnica de Catalunya Barcelona, Spain.
authors.forename: Ramón
authors.initials: R
authors.lastname: Bragós
authors.affiliation: Electronic and Biomedical Instrumentation Group, Department of Electronics Engineering, Universitat Politècnica de Catalunya Barcelona, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Rosell-Ferrer
authors.affiliation: Department of Cardiology, Hospital de la Santa Creu i Sant Pau, Institut d'Investigació Biomèdica - Sant Pau, Universitat Autònoma de Barcelona Barcelona, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Cinca
keywords: healed myocardial infarction; hemodynamics; myocardial electrical impedance; novel bioimpedance device; swine