Hypertrophic cardiomyopathy (HCM) is a genetic heart disorder with a prevalence of approximately one in 500 individuals, often linked with sudden cardiac death in young people. It presents significant clinical variability, ranging from asymptomatic cases to severe complications such as heart failure and fatal arrhythmias. HCM is histologically characterised by myocyte hypertrophy, fibrosis and myocyte disarray, with the latter being particularly associated with life-threatening ventricular arrhythmias. Identifying myocyte disarray early is crucial for preventing severe cardiac events and improving patient management.
Traditional cardiac magnetic resonance imaging (MRI) techniques such as late gadolinium enhancement (LGE) and T1 mapping can detect fibrosis and hypertrophy but fail to effectively visualise myocyte disarray. However, advances in cardiac diffusion-tensor imaging (cDTI) provide a non-invasive means to investigate myocardial microstructure by assessing water diffusion patterns within the heart muscle. This novel imaging technique can reveal microstructural abnormalities even before hypertrophy and fibrosis manifest, potentially allowing for earlier diagnosis and risk assessment in HCM patients.
Identifying Early Microstructural Changes
A recent study evaluated the effectiveness of cDTI in detecting early myocardial alterations among HCM patients. Thirty-five individuals with HCM and 15 healthy volunteers underwent comprehensive cardiac MRI assessments, including cine imaging, LGE, T1 mapping and cDTI using a 3.0-T MRI scanner. Fractional anisotropy (FA) and the diastolic second eigenvector angle (E2A) were identified as key cDTI markers representing myocardial microstructural integrity.
The findings revealed significantly reduced FA and increased E2A in participants with HCM compared to healthy controls. Even in heart segments without visible hypertrophy or fibrosis, FA values were lower and E2A values were higher, indicating microstructural disarray. This suggests that cDTI can detect subclinical myocardial alterations before the structural changes typically observed with conventional imaging techniques. The capacity to identify microstructural disruptions in apparently healthy myocardial segments highlights the sensitivity of cDTI as a tool for early detection.
The study’s segmental analysis further supported these observations. HCM segments without hypertrophy or fibrosis demonstrated reduced FA and elevated E2A compared to controls. This difference was statistically significant, suggesting that cDTI offers a reliable approach for detecting early myocardial changes, potentially before structural abnormalities become apparent with standard imaging methods.
Enhanced Diagnostic Accuracy with cDTI
The study also compared cDTI parameters with traditional cardiac MRI metrics, including native T1 mapping and LGE. While T1 mapping was effective in identifying myocardial fibrosis, cDTI demonstrated superior sensitivity in detecting microstructural abnormalities in segments without hypertrophy or fibrosis. ROC analysis confirmed that FA and E2A measurements offered greater diagnostic accuracy than native T1 values alone in distinguishing HCM segments from healthy myocardium.
FA and E2A measurements were shown to be effective in identifying myocardial disarray even in the absence of visible disease markers. The area under the curve (AUC) values for FA and E2A were significantly higher than those for native T1, suggesting that cDTI provides a more sensitive assessment of myocardial microstructure. This enhanced sensitivity could be crucial for identifying HCM at an earlier stage, when clinical interventions may be more effective in preventing disease progression and adverse cardiac events.
The study also revealed that cDTI parameters could distinguish between varying stages of myocardial involvement. Segments with both hypertrophy and fibrosis showed the most significant alterations, while those with only hypertrophy or neither still exhibited abnormal FA and E2A values compared to healthy controls. This reinforces the potential role of cDTI in identifying myocardial abnormalities across the full spectrum of HCM pathology.
Clinical Implications and Future Research
The ability of cDTI to identify myocardial disarray before the onset of hypertrophy and fibrosis has significant clinical implications. Early identification of myocardial microstructural abnormalities could facilitate earlier intervention strategies, such as lifestyle modifications, pharmacological therapies and closer patient monitoring, ultimately reducing the risk of severe cardiac events.
Furthermore, cDTI could play a role in risk stratification for HCM patients. By detecting subtle microstructural abnormalities, it may help clinicians identify patients at higher risk for arrhythmias and sudden cardiac death, improving the precision of treatment planning. Additionally, cDTI could be valuable in monitoring treatment response in HCM patients undergoing therapies aimed at reversing myocardial remodelling.
Future research should focus on validating these findings in larger, multi-centre studies with diverse patient populations. Long-term follow-up studies are also necessary to explore whether cDTI findings correlate with clinical outcomes, such as the development of symptomatic heart failure or arrhythmic events. Comparative studies between cDTI and other advanced imaging techniques, such as feature tracking and strain analysis, could further clarify its relative diagnostic advantages.
Cardiac diffusion-tensor imaging represents a significant advancement in the early detection of myocardial microstructural alterations in hypertrophic cardiomyopathy. By identifying myocardial disarray even in the absence of overt hypertrophy or fibrosis, cDTI holds promise for improving diagnostic accuracy, guiding treatment strategies and enhancing patient outcomes. Its ability to detect subtle myocardial changes early could redefine clinical approaches to HCM management, making it a valuable addition to the diagnostic toolkit for early-stage detection and risk assessment.
Source: Radiology: Cardiothoracic Imaging
Image Credit: iStock
