Correlation of left ventricular dyssynchrony on gated myocardial perfusion SPECT analysis with extent of late gadolinium enhancement on cardiac magnetic resonance imaging in hypertrophic cardiomyopathy

The Utility of Nuclear Imaging in Hypertrophic Cardiomyopathy: A Narrative Review

Hypertrophic cardiomyopathy (HCM) is the most common genetically inherited cardiac condition, characterized by clinical heterogeneity and a significantly increased risk of adverse cardiovascular outcomes, including sudden cardiac death. Current diagnostic methods primarily use echocardiography, often supplemented by cardiovascular magnetic resonance imaging (MRI), to assess the clinical profile of the disorder. Effective risk stratification protocols are essential for managing patients with HCM. These models rely on patient histories, imaging findings, and genetic information to evaluate the prognosis. Important factors in risk assessment include severe left ventricular hypertrophy (>30 mm), late gadolinium enhancement (>15%), or the presence of an apical aneurysm. However, these imaging techniques may lack sensitivity when it comes to detecting ischemia or microvascular dysfunction. Nuclear imaging methods, such as single-photon emission computed tomography (SPECT) and positron emission tomography (PET), offer a more comprehensive analysis of HCM. They provide valuable insights into the complex physiological mechanisms underlying the disease and facilitate early detection of functional abnormalities. This is particularly important for identifying high-risk phenotypes and understanding associated risk factors that may increase morbidity or mortality. This narrative review focuses on the role of nuclear imaging in the context of hypertrophic cardiomyopathy.

The Utility of a Combination of ^99mTc-MIBI Washout Imaging and Cardiac Magnetic Resonance Imaging in the Evaluation of Cardiomyopathy

Background: In cardiomyopathy, ^99mTc-MIBI washout can reflect mitochondrial dysfunction and late gadolinium enhancement (LGE) on cardiac magnetic imaging (MRI) is associated with tissue fibrosis. We sought to determine the relationship between ^99mTc-MIBI uptake, ^99mTc-MIBI washout, and LGE on MRI in patients with cardiomyopathy. Methods: Twenty-one patients underwent rest myocardial perfusion scintigraphy at 45 minutes (early) and 4 hours (delayed) after intravenous ^99mTc-MIBI administration and cardiac MRI. We assessed myocardial perfusion, ^99mTc-MIBI washout, and LGE. We divided the left ventricle (LV) wall into 16 segments using a polar map. Then, we classified each segment into 5 groups according to ^99mTc-MIBI uptake in early-rest images and washout. Additionally, we created a contingency table based on LGE presence/absence in the groups. Results: We evaluated 336 segments in 21 patients. ^99mTc-MIBI uptake was decreased in 168 segments in the early-rest ^99mTc-MIBI images. ^99mTc-MIBI washout was observed in 108 segments with either normal perfusion or reduced perfusion in the early-rest ^99mTc-MIBI images. LGE was positive in 104 segments. A contingency table analysis with Fisher's exact test showed that LGE was observed significantly more frequently in the segments with decreased ^99mTc-MIBI uptake (p<0.001). In segments without a decreased ^99mTc-MIBI uptake, there was a significant correlation between increased ^99mTc-MIBI washout and the presence of LGE (p=0.033). Conclusions: In cardiomyopathy, the mitochondrial dysfunction in the early stage is shown as ^99mTc-MIBI washout, and fibrotic changes in the myocardium in advanced stages are shown as LGE on cardiac MRI. The severity of myocardial damage and the clinical stage of cardiomyopathy can be evaluated using multimodal imaging.

The rate of myocardial perfusion recovery after steroid therapy and its implication for cardiac events in cardiac sarcoidosis and primarily preserved left ventricular ejection fraction

BACKGROUND

Sarcoidosis is a multisystemic disorder of unknown cause characterized by immune granuloma formation in the involved organs. Few studies have reported on the myocardial perfusion changes by immunosuppression therapy in cardiac sarcoidosis (CS). Additionally, the relationship between myocardial perfusion changes and prognosis is unknown. Therefore, this study aimed to clarify myocardial perfusion recovery after steroid therapy and its prognostic value for major adverse cardiac events (MACE) in patients with CS.

METHODS AND RESULTS

Thirty-eight consecutive patients with CS {median age, 63 [interquartile range (IQR) 51-68] years; 10 men} underwent both 18F-fluorodeoxyglucose positron emission tomography/computed tomography (CT) and electrocardiography-gated single-photon emission CT (SPECT) pre- and post-steroid therapy. Patients with improved or preserved myocardial perfusion after post-therapy were defined as the recovery group and those with worsened myocardial perfusion as the non-recovery group. Twenty-six patients (68%) were categorized as the recovery group. MACE occurred in eight patients. The Kaplan-Meier curves revealed a significantly higher rate of MACE in the non-recovery group (17.4%/y vs 2.9%/y, P = 0.007).

CONCLUSIONS

Myocardial perfusion was recovered by steroid therapy in 61% and preserved in 8% of patients. Myocardial perfusion recovery after steroid therapy was significantly associated with a low incidence of MACE.

Prognostic value of left ventricular mechanical dyssynchrony in hypertrophic cardiomyopathy patients with low risk of sudden cardiac death

PURPOSES

This study aims to explore the prognostic value of left ventricular mechanical dyssynchrony (LVMD) in hypertrophic cardiomyopathy (HCM) patients with low risk of sudden cardiac death (SCD).

METHODS

This retrospective study was performed in 50 patients with HCM who underwent Tc-99m sestamibi GSPECT-MPI. All patients were at low risk of SCD, defined as HCM risk-SCD scores <6%. Phase SD (PSD) and phase histogram bandwidth (PBW) were measured for assessment of LVMD. The primary endpoint was the composite major adverse cardiovascular events (MACE), including all-cause mortality, rehospitalization of heart failure symptoms, new-onset stroke, and new-onset syncope. Variables with significant difference between MACE group and non-MACE group were further assessed by Cox regression analysis.

RESULTS

During follow-up, MACE occurred in 20 patients. Systolic-PSD, systolic-PBW, diastolic-PSD, and diastolic-PBW were all significantly greater in the MACE group. Multivariate analysis revealed that history of syncope, history of atrial fibrillation, and all the four LVMD parameters were independent predictors of MACE. All LVMD parameters showed similar accuracy to predict MACE. Sequential models indicated that both systolic and diastolic LVMD parameters added incremental value beyond atrial fibrillation and syncope.

CONCLUSION

LVMD parameters are independent predictors of MACE, which add incremental prognostic information in patients with HCM risk-SCD scores <6%.

The feasibility and diagnostic value of intravoxel incoherent motion diffusion-weighted imaging in the assessment of myocardial fibrosis in hypertrophic cardiomyopathy patients

PURPOSE

To investigate the feasibility and diagnostic value of intravoxel incoherent motion (IVIM) in the assessment of myocardial fibrosis in hypertrophic cardiomyopathy (HCM) patients.

METHODS

Fifty-five HCM patients underwent IVIM diffusion-weighted cardiovascular resonance imaging; Cine, T1 mapping, IVIM and late gadolinium enhancement (LGE) were performed. The relationship of strain, pre T1, extracellular volume (ECV), IVIM-derived parameters (D, D* and f) and LGE were analyzed based on 16 American Heart Association segments. Abnormal segments of myocardial fibrosis were defined as: the presence of LGE (LGE+) or ECV ≥ 29.6 %.

RESULTS

D parameter was significantly increased in LGE + vs LGE- (1.89 ± 0.14 μm²/ms vs. 1.63 ± 0.12 μm²/ms, p < 0.001) and ECV ≥ 29.6 % vs ECV < 29.6 % (1.84 ± 0.13 μm²/ms vs. 1.61 ± 0.12 μm²/ms, p < 0.001), respectively. D* and f parameters were significantly decreased in LGE + vs LGE- (D*: 34.9 ± 6.6 μm²/m vs 55.2 ± 11.4 μm²/m, p < 0.001; f: 10.8 ± 1.29 % vs 12.5 ± 1.26 %, p < 0.001) and ECV ≥ 29.6 % vs ECV < 29.6 % (D*: 37.5 ± 6.9 μm²/m vs 59.6 ± 9.2 μm²/m, p < 0.001; f: 10.9 ± 1.1 % vs 13.00 ± 1.0 %, p = 0.021), respectively. Moreover, significant correlations were demonstrated between D and ECV, as well as D* and f.

CONCLUSIONS

IVIM DW-CMR has proven to be ingenious in the investigation of myocardial fibrosis; D* and f parameters may have potential value to assess the perfusion status of fibrotic regions in HCM patients.