MRI Evaluation of Local Myocardial Treatments: Epicardial Versus Endocardial (Cell‐Fix Catheter) Injections

AIMS: We compared two procedures for local myocardial treatment: transepicardial versus transendocardial catheter injection. Transepicardial injections were performed under direct surgical visualization whereas transendocardial injections were performed using electrophysiological guidance. METHODS: A left ventricle (LV) myocardial infarction (MI) was surgically created in 14 sheep. At 3 months, gadolinium was injected IV followed by the injection of super paramagnetic iron oxide (SPIO) into MI. Animals were divided in two groups: transepicardial injection (Group I) versus transendocardial (Group II) using "Cell-Fix" catheter injection. This catheter was developed to identify by electrophysiology the infarcted area and to stabilize injections suctioning the device to the endocardium. Postgadolinium delayed-enhancement magnetic resonance imaging (MRI) was performed to stain the infarct size. SPIO injections were used to assess the magnitude of the treated area. The ratio between SPIO black stained treatment areas and white gadolinium stained infarcted areas was calculated using MRI. RESULTS: The electrophysiological recordings by the catheter for the MI versus normal LV wall were: R wave amplitude 4.16 versus 12.08 mV (P = 0.003), slew rate (slope of the signal) 0.36 V/s versus 1.04 V/s (P = 0.008). The ratio of the SPIO diffusion into the MI was 41.2 +/- 8.1% for surgical and 63.7 +/- 8.2% for percutaneous endocardial injections (P = 0.0132). CONCLUSION: MRI allows evaluation of the extent of local myocardial treatments. The differences shown between epicardial and endocardial injections concerning the distribution of SPIO can be justified by the methodology of injection and by a more precise MI detection by electrophysiology. In conclusion, electrophysiological recordings to guide injections is superior to direct surgical visualization in terms of injecting into infarcted tissue.