A 43-year-old man with nonobstructive hypertrophic cardiomyopathy (HCM) and a history of atrial tachycardia was referred for adenosine stress perfusion cardiac magnetic resonance (CMR) due to a suspicion of myocardial ischemia because of exercise-induced angina pectoris. Images were acquired using a 3T whole body MR scanner (Magnetom Vida, Siemens Healthcare, Erlangen, Germany). Stress arterial input function and perfusion images were acquired after intravenous administration of adenosine for at least 3 minutes (140 μg/kg/min), according to a dual-bolus protocol (prebolus 0.0075 mmol/kg + main bolus 0.075 mmol/kg of gadoteric acid [0.5 mmol/ml], Guerbet, Villepinte, France, each followed by 20 ml of saline, infusion rate 3 ml/s). Fully-automated quantitative perfusion (QP) analysis was performed using cvi42 software (Circle Cardiovascular Imaging Inc., Calgary, Canada).

CMR showed typical features of HCM, including severe, asymmetric left ventricular (LV) hypertrophy (basal anteroseptum, 23 mm), with good global function and hypokinesia of hypertrophic segments. Late gadolinium enhancement (LGE) images revealed typical midmyocardial, patchy fibrosis (Figure 1A1C, Supplementary material, Figure S1A–S1C). Adenosine stress first-pass perfusion imaging showed extensive perfusion defects in the hypertrophied mid inferoseptal segment, apical inferior, septal, and partially lateral segment (Figure 1D1F, Supplementary material, Figure S1D–S1I). The hypoperfused areas exceeded the area of LGE and were not consistent with any specific coronary territory. The fully automated QP analysis revealed substantially reduced stress myocardial blood flow (MBF) values (1.3 ml/g/min) and myocardial perfusion reserve (MPR) of 1.5 (Figure 1G and 1H, Supplementary material, Figure S1J–S1P). Subsequently performed coronary angiography showed no features of obstructive coronary artery disease. As more frequently observed in HCM patients, 50%–60% bridging of the left anterior descending artery was present. Such a combination of observations is highly suggestive of extensive coronary microvascular dysfunction (MVD).

Figure 1. Cardiac magnetic resonance imaging in a patient with hypertrophic cardiomyopathy; AC – late gadolinium enhancement (LGE) images showing typical midmyocardial patchy fibrosis (arrows) in the basal (A), mid, (B) and apical (C) left ventricular segments; DF – color pixel maps of fully-automated quantitative adenosine stress first-pass perfusion analysis revealing perfusion defects in the hypertrophied mid inferoseptal segment, apical inferior, septal, and partially lateral segment that exceed the area of LGE; G, H – results of quantitative perfusion assessment showing stress MBF values reduced to 1.3 ml/g/min (G) and impaired MPR (1.5 ml/g/min; H)

Abbreviations: AHA, American Heart Association; MBF, myocardial blood flow; MPR, myocardial perfusion reserve

Chest pain is a frequent complaint occurring in up to 50% of patients with HCM, and can often be caused by MVD.1 In HCM, myocyte disarray and MVD are prevalent even at the early stages of the disease. Importantly, MVD occurs in mutation carriers even when hypertrophy is not present, therefore it may serve as an early-phenotype biomarker in subclinical HCM.2,3 The presence of MVD can be considered an important ischemic substrate in HCM, which may contribute to LV remodeling, fibrosis, systolic dysfunction, and adverse outcomes, including sudden cardiac death.1,4 Studies have shown prognostic significance of MBF and MPR in HCM. Therefore, adding these measures to a clinical risk assessment may be beneficial for this group of patients.5

Recently introduced fully-automated QP CMR allows for noninvasive and radiation-free absolute quantification of MBF and detection of MVD. This advanced method can be integrated into a comprehensive, one-stop shop CMR assessment of HCM patients, evaluating cardiac anatomy, function, presence, and extent of myocardial fibrosis. All these components can be included in a time-efficient image acquisition protocol lasting less than 45 minutes.

This case highlights that QP CMR may serve as an effective tool to detect MVD as a cause of chest pain in patients with HCM. Therefore, incorporation of QP CMR into clinical practice may provide valuable diagnostic and prognostic insight for this cohort of patients.