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Magnetic resonance imaging of microvascular obstruction in hypertrophic obstructive cardiomyopathy after percutaneous transluminal septal myocardial ablation

Background The clinical significance of microvascular obstruction (MO) in hypertrophic cardiomyopathy (HOCM) after percutaneous transluminal septal myocardial ablation (PTSMA) remains unknown. Purpose To assess the relationship between the location of MO and the improvement in symptoms and pressure gradient after PTSMA in patients with HOCM. Material and Methods Twenty-three patients with HOCM underwent MRI within 24 weeks after PTSMA. The MO was defined visually as the hypointense region adjacent to the left or right ventricular cavity, which was surrounded by myocardial infarction. The location of MO and improvement in clinical symptoms and pressure gradient at 3–6 months follow-up were assessed. Results MO was observed in 16 patients who underwent MRI within 7 weeks after PTSMA. Left-sided MO was observed in 12 patients, and right-sided MO was observed in four patients. Improvement in clinical symptoms and reduction in the pressure gradient were not sufficient in the patients with right-sided MO, while PTSMA was effective in the patients with the left-sided MO. Conclusion The location of MO identified by MRI may be related to the effectiveness of PTSMA at the short-term follow-up. The left-sided MO is related to complete improvement in clinical symptoms and pressure gradients.