Excessive tortuosity of the coronary arteries (TCA) is a somewhat common finding in patients referred for coronary angiography, reported in 14-40% of patients referred for angiography. The presence of TCA has been associated with chest pain and myocardial perfusion abnormalities during stress in the absence of obstructive coronary artery disease. Fluid dynamic modeling suggests that stress-induced ischemia may be attributable to a reduction in distal coronary artery perfusion pressure from viscous and turbulence energy losses. The physiologic reasons for TCA are unclear. The roles of TCA on prognosis of HCM are also needed to explore. Pre-clinical studies where elastases and collagenases were used to alter arterial morphology together with genetic and pathologic analysis of rare clinical disorders such as arterial tortuosity syndrome have indicated that arterial tortuosity arises from abnormalities in arterial elastin fibers and extracellular matrix. Apart from inherited disorders, some but not all studies have linked TCA with hypertension and female sex, and with increased left ventricular (LV) mass from pressure but not volume overload and smaller heart size.

Hypertrophic cardiomyopathy (HCM) is associated with an increased left ventricular (LV) wall thickness. HCM is the most common genetic heart disease, characterized by marked clinical and morphologic heterogeneity. Diagnosis is usually based on the echocardiographic finding of unexplained left ventricular (LV) hypertrophy, defined by increased wall thickness in 1 or more LV segments. LV mass is generally assumed to be increased in patients with phenotypically expressed HCM, based largely on early pathological studies. TCA among HCM patients have not been studied. So, firstly, we choose HCM and non-HCM patients to investigate the relationship between TCA and HCM, and further explore the potential roles of TCA for prognosis in HCM.

In HCM patients, disruption of the ordered arrangement of myofibers alters normal cardiac mechanical function, resulting in temporal and spatial heterogeneity in regional myocardial contractility. Although global LV function is generally unaltered, asynchrony and asynergy in regional function lead to delayed diastolic relaxation and impaired diastolic filling. Whilst LV ejection fraction is frequently normal in both, LV strain assessment could differentiate, compared to normal person. Cardiovascular magnetic resonance (CMR), by virtue of its high-resolution volumetric reconstruction of the LV chamber, currently affords a highly accurate and reproducible quantitative assessment of mass . So secondly, we sought to establish if cardiovascular magnetic resonance myocardial feature tracking (CMR-FT), an emerging method allowing accurate assessment of myocardial deformation, differentiates between HCM with or without TCA. Additionally, we want to explore the potential genetic factor on TCA in HCM.

This is a single-center, retrospective, case control study that will evaluate the difference of TCA between HCM and non-HCM, and explore the prognostic roles of TCA in the first part. In the second part, we will use CMR-FT to compare the myocardial strain between HCM with or without TCA and analyze the relationship of strain and TCA. In the third part, we choose HCM patients and non-HCM to investigate potential genetic factors for TCA in HCM.