The purpose of this observational study is to compare the impact of rotational atherectomy to conventional stenting and to investigate how it may affect coronary microcirculation in patients with calcified coronary artery lesions and stable CAD. The study's objectives are to: * investigate the impact of rotational atherectomy on the prevalence of post-percutaneuos coronary intervention coronay microvascular dysfunction; * investigate the impact of conventional stenting on the prevalence of post-percutaneuos coronary intervention coronay microvascular dysfunction; and * compare the impact of both percutaneuos coronary interventions on coronary microvascular dysfunction. Patients with calcified lesions will be enrolled prospectively and will have serial invasive and non-invasive microvascular testing prior to and after rotational atherectomy or conventional stenting.