Echocardiography is the gold standard in diagnosing DMCM, owing to its high temporal and spatial resolutions, accessibility, affordability, and harmlessness (19, 21). One of the earliest features of DMCM is the impairment of diastolic function (19). In a case-control study among patients with DM2 with a median duration of > 5 years, systolic function was preserved among all patients. However, 54% of the diabetic patients had diastolic dysfunction, compared to 11% among non-diabetic controls, with more incident diastolic dysfunction correlating with duration of diabetes (22).

Further, Somaratane et al. inspected the prevalence of LVH in a cohort of DM2, and found that 56% of the diabetic population exhibited this structural abnormality. Interestingly, electrocardiograms (EKG) only detected 5% of LVH cases, and while NT-proBNP was superior to EKG, it remained inadequate; this study underscores the significant utility of echocardiography in detecting LVH (23).

Additionally, in patients with DM1 and average HbA1c of 8%, the lateral mitral annular early diastolic velocity was lower compared to non-diabetic controls, which is a marker of diastolic dysfunction (24). Moreover, in DM2 patients with a mean diabetes duration of 6.3 years, 45% demonstrated abnormal global longitudinal strain, which conferred a higher risk for the development of all-cause mortality or hospitalization (25).

Impaired diastolic parameters among diabetic patients are evidently associated with worse clinical outcomes. Rorth et al. showed that, among DM1 patients, higher filling pressures, as measured by early mitral inflow velocity and mitral annular early diastolic velocity ratio (e/e’), was associated with a higher risk of non-fatal myocardial infarction, cerebrovascular accidents, and death (26). Similarly, From et al. demonstrated that, among DM2 patients, the cumulative probability of both the incidence of heart failure and death more than doubled among diabetics with higher filling pressures as measured by e/e’ ratios (27).

In summary, echocardiography remains indispensable in the early detection and monitoring of DMCM, providing critical prognostic information that guides clinical decision-making and management. Its ability to identify subtle changes in cardiac structure and function underscores its role as the gold standard imaging modality in this patient population.

However, this technique is not without its challenges; the diagnostic accuracy can be operator-dependent, and image quality may be compromised in patients with poor acoustic windows, such as those with obesity or chronic lung disease (28). Additionally, while echocardiography is excellent for structural assessment, it provides limited information on myocardial tissue characterization and metabolism, which are crucial for understanding the pathophysiology of DMCM (3).

Cardiac magnetic resonance imaging (CMR) possesses higher spatial and temporal resolution than echocardiography, in addition to allowing the assessment of myocardial fibrosis and altered metabolism, which are hallmarks of DMCM (3, 19, 21).

Among DM1 patients, average HbA1c levels were inversely associated with stroke volume and positively correlated with the presence of myocardial scar tissue (29). Additionally, myocardial perfusion reserve and diastolic strain rate were abnormal in diabetic patients when compared to controls; further, increased myocardial triglyceride content, but not impaired myocardial flow reserve, was associated with abnormal diastolic function, suggesting that steatosis, but not necessarily small vessel disease, may be responsible for early diastolic dysfunction in DMCM (30). In a cohort derived from the general population, CMR revealed that pre-DM and DM were associated with LV remodeling compared to non-diabetic controls (31). Fibrotic tissue, as determined by late gadolinium enhancement, can be easily assessed using CMR and it has been associated with worse major adverse cardiovascular events (MACE) in diabetic patients (32).

However, CMR remains underutilized, largely owing to its perceived expense burden, patient comfort issues, and longer examination times (33). Additionally, traditional, older generation Gadolinium-based contrast media (CGBM) were associated with a low but serious risk of nephrogenic systemic fibrosis. Thankfully, with group II CGMB, this risk is significantly diminished (34). With further advancements in imaging and technology, it may be feasible in the future to incorporate CMR as a cornerstone in DMCM management.

Nuclear imaging allows the detection of low-density processes, making it possible to measure myocardial metabolism and to assess molecular imaging (20). Gated SPECT possesses the capability to assess myocardial perfusion and LV function; however, limited data exist on its widespread clinical utility in DMCM (3).

Positron emission tomography (PET) allows flexibility in radiotracer design radiolabeled with a variety of radionuclides, and radiotracers administered at low doses do not alter metabolic processes (20). In order to circumvent the low spatial resolution observed in PET, it is usually combined with computer tomography or CMR to allow for accurate radiotracer localization (3, 20).

PET imaging has been utilized to study a multitude of metabolic parameters in DMCM. Using PET-CMR in DM2 patients with average HbA1c of 7.1% and mean diabetes duration of 4 years, Rijzewijk et al. demonstrated impaired diastolic parameters among diabetics; more importantly, they revealed increased myocardial fatty acid uptake and oxidation compared to controls, indicating myocardial metabolic remodeling (35). Similarly, in DM1 patients, PET imaging revealed increased free fatty acid utilization and decreased myocardial glucose uptake (36). Further, phase analysis of gated SPECT MPI revealed that asymptomatic DM2 patients with normal perfusion scans exhibited significant left ventricular mechanical dyssynchrony, particularly in those with a diabetes duration of more than 15 years (37). In a study investigating the association between diabetes mellitus and myocardial glucose uptake using 18F-FDG PET/CT, it was demonstrated that DM is significantly associated with decreased myocardial glucose metabolism, with up to 84% of diabetic patients showing poor FDG uptake. Furthermore, multivariate logistic regression analysis revealed that gender (male), Homeostatic Model Assessment of Insulin Resistance, and metabolic dysfunction-associated steatotic liver disease were independent risk factors for poor myocardial FDG uptake in diabetic patients (38).

In summary, nuclear imaging techniques like PET and gated SPECT are valuable in assessing myocardial metabolism and function in DMCM, revealing significant alterations such as impaired diastolic parameters, increased myocardial fatty acid uptake and oxidation, decreased myocardial glucose uptake, and left ventricular mechanical dyssynchrony, particularly in patients with prolonged diabetes duration.

The main challenges associated with nuclear imaging include its high cost and limited availability (20). Additionally, the relatively low spatial resolution of PET compared to CMR can limit its ability to detect small areas of myocardial scar or fibrosis (19). The use of ionizing radiation in both PET and SPECT raises concerns about radiation exposure, particularly in younger patients and those requiring repeated imaging studies (20). Furthermore, the interpretation of nuclear imaging studies requires specialized expertise, which may not be readily available in all clinical settings (3).

In conclusion, while each imaging modality offers unique benefits in the assessment of DMCM, they also come with specific challenges ( Table 1 ). A multimodality approach, leveraging the strengths of each technique, can provide a comprehensive evaluation of diabetic cardiomyopathy, improving diagnostic accuracy and informing therapeutic strategies. Future advancements in imaging technology and reductions in cost may further enhance the integration of these modalities into routine clinical practice.