Abstract
BackgroundHypertrophic cardiomyopathy (HCM) is characterized by increased left ventricular wall thickness, cardiomyocyte hypertrophy, and fibrosis. Adverse cardiac risk characterization has been performed using late gadolinium enhancement (LGE), native T1, and extracellular volume (ECV). Relaxation time constants are affected by background field inhomogeneity. T1ρ utilizes a spin-lock pulse to decrease the effect of unwanted relaxation. The objective of this study was to study T1ρ as compared to T1, ECV, and LGE in HCM patients.MethodsHCM patients were recruited as part of the Novel Markers of Prognosis in Hypertrophic Cardiomyopathy study, and healthy controls were matched for comparison. In addition to cardiac functional imaging, subjects underwent T1 and T1ρ cardiovascular magnetic resonance imaging at short-axis positions at 1.5T. Subjects received gadolinium and underwent LGE imaging 15–20 min after injection covering the entire heart. Corresponding basal and mid short axis LGE slices were selected for comparison with T1 and T1ρ. Full-width half-maximum thresholding was used to determine the percent enhancement area in each LGE-positive slice by LGE, T1, and T1ρ. Two clinicians independently reviewed LGE images for presence or absence of enhancement. If in agreement, the image was labeled positive (LGE + +) or negative (LGE −−); otherwise, the image was labeled equivocal (LGE + −).ResultsIn 40 HCM patients and 10 controls, T1 percent enhancement area (Spearman’s rho = 0.61, p < 1e-5) and T1ρ percent enhancement area (Spearman’s rho = 0.48, p < 0.001e-3) correlated with LGE percent enhancement area. T1 and T1ρ percent enhancement areas were also correlated (Spearman’s rho = 0.28, p = 0.047). For both T1 and T1ρ, HCM patients demonstrated significantly longer relaxation times compared to controls in each LGE category (p < 0.001 for all). HCM patients also showed significantly higher ECV compared to controls in each LGE category (p < 0.01 for all), and LGE −− slices had lower ECV than LGE + + (p = 0.01).ConclusionsHyperenhancement areas as measured by T1ρ and LGE are moderately correlated. T1, T1ρ, and ECV were elevated in HCM patients compared to controls, irrespective of the presence of LGE. These findings warrant additional studies to investigate the prognostic utility of T1ρ imaging in the evaluation of HCM patients.
Highlights
Hypertrophic cardiomyopathy (HCM) is characterized by increased left ventricular wall thickness, cardiomyocyte hypertrophy, and fibrosis
Controls had similar distributions of age, gender, and body surface area (BSA). 30% of patients had a history of ventricular arrhythmia, and 15% had a history of syncope
In our study characterizing the role of endogenous T1ρ imaging in the assessment of patients with HCM, we found that (1) percent area enhancement as measured by T1 and T1ρ at full width at half maximum (FWHM) were moderately correlated with late gadolinium enhancement (LGE) area enhancement, (2) HCM short-axis slices categorized as LGE + +, LGE + −, and LGE −− each demonstrated elevated pre-contrast T1, T1ρ, and extracellular volume (ECV) compared to controls, and (3) ECV was significantly different between images rated LGE + + compared to LGE −−
Summary
Hypertrophic cardiomyopathy (HCM) is characterized by increased left ventricular wall thickness, cardiomyocyte hypertrophy, and fibrosis. Adverse cardiac risk characterization has been performed using late gadolinium enhancement (LGE), native T1, and extracellular volume (ECV). Hypertrophic cardiomyopathy (HCM), characterized by an unexplained increase in left ventricular (LV) wall thickness, is the most common genetic cardiac disorder, with a prevalence of approximately 1 in 500; this. Seen as late gadolinium enhancement (LGE), has been identified as a risk factor for sudden cardiac death and heart failure in this population [3]. Not all HCM patients will go on to have an event; LGE has a high prevalence (as high as 70%) in this population [6, 7] but a low specificity for the prediction of future cardiovascular events, limiting its negative predictive value [8]. There is interest in the development and validation of more specific and non-contrast methods for myocardial characterization in HCM patients
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