Left ventricular global function index is associated with myocardial iron overload and heart failure in thalassemia major patients

Biatrial and Biventricular Reference Ranges Based on Cardiac Magnetic Resonance in Sickle Cell Disease Patients Without Heart Damage

BACKGROUND/OBJECTIVES

We aimed to establish biatrial and biventricular reference ranges using cardiac magnetic resonance (CMR) parameters in SCD patients without heart damage.

METHODS

This study compared CMR parameters, quantified by cine SSFP sequences, in 48 adult SCD patients without apparent cardiac involvement (defined by the absence of known risk factors, normal electrocardiogram, and no macroscopic myocardial fibrosis or significant cardiac iron on T2* CMR) to matched cohorts of 96 healthy controls and 96 thalassemia major (TM) patients without cardiac damage. Nine paediatric SCD patients were also analysed and compared to age- and gender-matched groups of nine TM patients and nine healthy subjects.

RESULTS

In all groups, studied males displayed higher biventricular volumes and mass indexes than females. Male SCD patients showed significantly higher left ventricular (LV) end-diastolic volume index (EDVI), LV end-systolic volume index (ESVI), LV stroke volume index (SVI), cardiac index, LV and right ventricular (RV) mass index, and atrial areas than healthy subjects. Females with SCD exhibited increased LV EDVI, LV SVI, RV mass index, and left atrial area index compared to healthy controls. SCD and TM patients showed comparable biatrial areas and biventricular volumes and function. When compared to TM, SCD males exhibited a larger mass index, while SCD females showed an increased RV mass index. CMR parameters were similar across all paediatric groups.

CONCLUSIONS

By establishing the biatrial and biventricular reference ranges through CMR for adult male and female SCD patients, we aimed to prevent possible misdiagnosis of cardiomyopathy in this population by taking into account cardiac adaptation due to anaemia.

Cardiovascular magnetic resonance in β-thalassemia major: beyond T2

Β-thalassemia major (TM) patients underwent regular transfusions to prevent complications of chronic anemia. However, these regular transfusions result in progressive iron accumulation in vital organs, including the heart. Myocardial iron overload can lead to cardiac dysfunction and ultimately to heart failure. Diagnosis of cardiac dysfunction in β-TM patients is usually made through clinical examination, electrocardiogram, and echocardiography. Cardiac magnetic resonance (CMR), through the measurement of T2* relaxation time, represents the diagnostic modality of choice for assessing myocardial iron overload and guiding the iron chelation therapy. Despite a tailored chelation therapy reducing myocardial iron overload, heart failure remains the leading cause of morbidity and mortality even in well-treated β-TM patients. Advances in CMR, including myocardial strain, parametric mapping (T1, T2, and extracellular volume), and late gadolinium enhancement (LGE) measurements, have expanded its role in the diagnosis, prognosis, and follow-up of these patients. This review seeks to offer a thorough overview of the potential uses of CMR in β-TM, extending beyond the established role of T2* measurement in guiding chelation therapy. It delves into the emerging applications of new CMR imaging biomarkers that could improve the overall management of β-TM patients.

Ventricular Ejection Fraction and Global Strains in Connection with the Volume Regulation Graph

Ejection fraction (EF) is traditionally considered useful to infer ventricular function. Newer metrics such as global function index (GFI) and various strains add supplemental diagnostic or prognostic value. All these candidates refer to dimensionless ratios, rather than to the characteristics of the underlying components. Therefore, we introduced the volume regulation graph (VRG), relating end-systolic volume (ESV) to end-diastolic volume (EDV). An individual patient is then uniquely defined by the prevailing working point in the volume domain. Alternatively, the combination of EF=(1-ESV/EDV) and any suitable companion (denoted as C) metric (e.g. the Pythagorean mean) specifies this working point.An expression relates EF to global longitudinal (GLS) and circumferential strain (GCS): ESV/EDV = (GLS+1) (GCS+1)2, resembling the empirical regression equation for the VRG. However, the latter has a non-zero intercept (mL). The discrepancy can be solved by the introduction of one or more pertinent companion metrics.We studied 96 patients by cardiac magnetic resonance imaging and calculated EF, EFC, GFI, GLS and GCS. The GFI is inversely related to GLS (R2=0.26). For regression we found: ESV=0.74 EDV-27.0 with R2=0.81 for N=96. Similar results were obtained for echocardiography data (N=25). Graphs relating EF to GLS and GCS indicate that EFC can distinguish patients with nearly identical values for these 3 metrics.Thus, the VRG offers a unifying framework that visualizes the association between ESV and EDV, while documenting iso-EF and iso-EFC trajectories. Newer metrics including GFI, GLS and GCS require consideration of a companion variable such as EFC to permit a comprehensive analysis.Clinical Relevance- The VRG allows insight into ventricular functioning and illustrates the working point concept. Companion metrics (having a physical dimension) should be considered in conjunction with any traditional ratio-based index.