Endocardial infarct scar recognition by myocardial electrical impedance is not influenced by changes in cardiac activation sequence

Abstract

Background: Measurement of myocardial electrical impedance can allow recognition of infarct scar and is theoretically not influenced by changes in cardiac activation sequence, but this is not known.

Objectives: The objectives of this study were to evaluate the ability of endocardial electrical impedance measurements to recognize areas of infarct scar and to assess the stability of the impedance data under changes in cardiac activation sequence.

Methods: One-month-old myocardial infarction confirmed by cardiac magnetic resonance imaging was induced in 5 pigs submitted to coronary artery catheter balloon occlusion. Electroanatomic data and local electrical impedance (magnitude, phase angle, and amplitude of the systolic-diastolic impedance curve) were recorded at multiple endocardial sites in sinus rhythm and during right ventricular pacing. By merging the cardiac magnetic resonance and electroanatomic data, we classified each impedance measurement site either as healthy (bipolar amplitude ≥1.5 mV and maximum pixel intensity <40%) or scar (bipolar amplitude <1.5 mV and maximum pixel intensity ≥40%).

Results: A total of 137 endocardial sites were studied. Compared to healthy tissue, areas of infarct scar showed 37.4% reduction in impedance magnitude (P < .001) and 21.5% decrease in phase angle (P < .001). The best predictive ability to detect infarct scar was achieved by the combination of the 4 impedance parameters (area under the receiver operating characteristic curve 0.96; 95% confidence interval 0.92-1.00). In contrast to voltage mapping, right ventricular pacing did not significantly modify the impedance data.

Conclusion: Endocardial catheter measurement of electrical impedance can identify infarct scar regions, and in contrast to voltage mapping, the impedance data are not affected by changes in cardiac activation sequence.

Keywords: Electroanatomic mapping; Healed myocardial infarction; Myocardial electrical impedance; Pig; Ventricular pacing.