Role of Coronary Microvascular Dysfunction in restenosis after successful CTO recanalization assessed by angiography-derived index of microcirculatory resistance with a pressure-wire-free modality

Background and objectives: Development of coronary microvascular dysfunction (CMD) is a multifactorial, pathophysiological process resulting in impaired cardiac microcirculation. In patients with myocardial ischemia without coronary stenosis it occurs frequently predicting an increased mortality. The impact of CMD in patients with a chronic total occlusion of a coronary artery (CTO) is unclear. There are only limited studies investigating the occurrence and predictive value of CMD in patients with CTO, although successfully treated CTO vessels have a high risk of restenosis. CMD can be assessed by invasive and non-invasive modalities. Index of microcirculatory resistance (IMR) is one of the most commonly used indices. The invasive modality to assess microvascular dysfunction is a pressure-wire-based and thermodilution-derived method. A new method to assess IMR non-invasively is by using the software package Medis Suite 2.1.12.2 (Medis Medical Imaging System, Leiden, the Netherlands). The aim of this study was to investigate the effect of successful CTO PCI on microvascular function of the CTO supplied territory directly after PCI and at 6 months follow-up. On top of this we investigate whether microvascular dysfunction can be identified as a risk factor for restenosis after CTO PCI.

Methods and results: Our analysis included 60 patients (40 patients with good result in surveillance coronary angiography and 20 patients with restenosis at 6 month follow-up) had undergone successful CTO recanalization at the University Medical Center of Mainz. The measurement to assess IMR was performed directly after successful CTO PCI and at 6 months follow-up. IMR was performed offline using a software package (Medis Suite 2.1.12.2, Medis Medical Imaging System, Leiden, the Netherlands). 79.5 % were male with a median age of 62 years (45-80). The mean follow-up period was 187± 23.10 days. Median J-CTO Score was 2 (1-3), CTO was localized at the RCA in 65.0%,  at the LAD in 27.5% and at the RCX in 7.5% of the patients. All included patients had a good result after CTO recanalization confirmed by Quantitative flow ratio (QFR) (0.97± 0.02) directly after PCI. We found increased IMR values directly after CTO PCI with a significant decrease at 6 months follow-up (32.89± 6.87 vs. 28.82± 7.60¸p= 0.016). We found no difference of the IMR value between patients without restenosis and patients with restenosis at follow-up in our collective (32.70± 6.95 vs. 28.10± 7.17, p= 0.09)

Conclusions: We found microvascular dysfunction in our collective of patients with CTO assessed non-invasively by IMR. At 6 months follow-up we found decreased IMR value. In our collective we could not identify microvascular dysfunction as a risk factor for restenosis after successful recanalization.