Earliest cardiac toxicity induced by iron overload selectively inhibits electrical conduction

Severe iron overload cardiomyopathy manifested as acute myopericarditis: A case report

Iron overload cardiomyopathy (IOC) is a condition in which iron deposition in the heart causes cardiac dysfunction. We described a 21-year-old woman who presented with acute chest pain, dyspnea, and fever. The patient had a history of transfusion-dependent thalassemia (TDT) and secondary hemochromatosis with the latest serum ferritin ranging from 8000 to 15,000. Physical examinations revealed signs of anemia and heart failure. Electrocardiography showed diffuse ST-segment elevation with reciprocal ST-segment depression in aVR and complete atrioventricular block. Cardiac markers were markedly elevated. Echocardiography demonstrated the dilated size, impaired systolic function, global wall hypokinesia, restrictive filling pattern of the left ventricle, and a small amount of pericardial effusion. Coronary angiography showed normal coronary arteries. A cardiac magnetic resonance imaging showed multifocal early and late gadolinium enhancement involving mid-wall and subepicardial areas of biventricular myocardium suggestive of diffuse myocardial injury from an inflammatory process. She was provisionally diagnosed with acute myopericarditis. Ibuprofen and loop diuretic were prescribed; however, cardiogenic shock occurred. Thus, an endomyocardial biopsy was done and revealed diffuse myocardial hemosiderin deposition without evidence of inflammatory cell infiltration. Severe IOC mimicking acute myopericarditis was considered based on an endomyocardial biopsy result. An intravenous iron chelating agent was immediately administered. Unfortunately, cardiogenic shock was refractory resulting in death. This case demonstrated a rare manifestation of IOC, which can masquerade as acute myopericarditis, and emphasized that IOC should be differentially diagnosed, particularly in patients with TDT and hemochromatosis.

Hereditary Hemochromatosis: A Cardiac Perspective

Hereditary hemochromatosis (HH) is a common genetic metabolic disorder characterized by excessive iron absorption and elevated serum iron levels, which accumulate in various organs, such as the heart, pancreas, gonads, and damage these organs. There are only a few articles and clinical studies describing the characteristics of cardiac involvement in HH along with the significance of early diagnosis and management in preventing complications. In this review article, we have reviewed multiple pieces of literature and gathered available information regarding the subject. We compiled the data to investigate the importance of early detection of symptoms, regular monitoring, and prompt management with strict adherence to reverse or prevent complications. This article has reviewed different aspects of cardiac hemochromatosis, such as pathogenesis, clinical presentation, diagnosis, and management. Recognition of early symptoms, diagnosis of cardiac involvement with various modalities, and implementation of early treatment are essentially the foundation of better outcomes in HH.

Blood donation and heavy metal poisoning in developing nations: Any link?

Long term health effects of heavy metal exposure from both occupational and environmental settings involve multi-organ toxicities including but not limited to disturbances of neurological, cognitive, and metabolic processes, immune system dysregulation, carcinogenesis and sometimes permanent disabilities. Humans are exposed to toxic metals through various sources and routes of entry. The risk of heavy metal poisoning from donor blood has been the subject of many scientific investigations. In this review we highlight how the access to a safe and adequate blood transfusion with minimal risk of toxic metals to recipients is a public health challenge, especially in developing nations. For quality assurance purposes, blood donors are screened for various blood-borne pathogens, but screening for toxic metal levels is not routine. Evidence from scientific studies used in this review lends credence to the risk of heavy metal poisoning from donors with high blood concentrations of these heavy metals. The risk of toxicity is exceptionally high in vulnerable populations such as neonates and preterm infants, as well as in pregnant women and other individuals with conditions requiring multiple blood transfusions. This is worse in developing countries where some members of the population engage in illegal refining and artisanal mining activities. In order to reduce toxic metal exposure in vulnerable populations, blood meant for transfusion in vulnerable subjects, e.g. children, should be routinely screened for heavy metal concentrations. Patients receiving multiple blood transfusions should also be monitored for iron overload and its attendant toxicities.

Iron overload and arrhythmias: Influence of confounding factors

Arrhythmias as a cardiac complication of iron overload (IO) have been well described for decades in the clinical literature. They are assumed to be directly associated with the myocardial accumulation of iron. However, the influence of heart failure and elevated oxidative stress, which are major arrhythmogenic confounding factors associated with IO on arrhythmias, has not been critically reviewed in the published literature. A comprehensive narrative review of published articles in PubMed was conducted to address the influence of confounding factors of IO on arrhythmias. The previous data may have been largely confounded by the other cardiac complications of IO, particularly heart failure. The previous studies on IO-related arrhythmias lack proper age-gender-matched control subjects and/or comparison groups with properly controlled confounding factors to assess accurately their etiology and clinical significance. Given the above considerations, further mechanistic investigations to clarify the etiology and clinical relevance of IO-induced arrhythmias are needed. In addition, investigations to develop arrhythmia management strategy specific to IO, are warranted.

Calcium Deregulation: Novel Insights to Understand Friedreich's Ataxia Pathophysiology

Friedreich's Ataxia (FRDA) is a neurodegenerative disorder, characterized by degeneration of dorsal root ganglia, cerebellum and cardiomyopathy. Heart failure is one of the most common causes of death for FRDA patients. Deficiency of frataxin, a small mitochondrial protein, is responsible for all clinical and morphological manifestations of FRDA. The focus of our study was to investigate the unexplored Ca²⁺ homeostasis in cerebellar granule neurons (CGNs) and in cardiomyocytes of FRDA cellular models to understand the pathogenesis of degeneration. Ca²⁺ homeostasis in neurons and cardiomyocytes is not only crucial for the cellular wellbeing but more importantly to generate action potential in both neurons and cardiomyocytes. By challenging Ca²⁺ homeostasis in CGNs, and in adult and neonatal cardiomyocytes of FRDA models, we have assessed the impact of frataxin decrease on both neuronal and cardiac physiopathology. Interestingly, we have found that Ca²⁺ homeostasis is altered both cell types. CGNs showed a Ca²⁺ mishandling under depolarizing conditions and this was also reflected in the endoplasmic reticulum (ER) content. In cardiomyocytes we found that the sarcoplasmic reticulum (SR) Ca²⁺ content was pathologically reduced, and that mitochondrial Ca²⁺ uptake was impaired. This phenomenon is due to the excess of oxidative stress under FRDA like conditions and the consequent aberrant modulation of key players at the SR/ER and mitochondrial level that usually restore the Ca²⁺ homeostasis. Our findings demonstrate that in both neurons and cardiomyocytes the decreased Ca²⁺ level within the stores has a comparable detrimental impact in their physiology. In cardiomyocytes, we found that ryanodine receptors (RyRs) may be leaking and expel more Ca²⁺ out from the SR. At the same time mitochondrial uptake was altered and we found that Vitamin E can restore this defect. Moreover, Vitamin E protects from cell death induced by hypoxia-reperfusion injury, revealing novel properties of Vitamin E as potential therapeutic tool for FRDA cardiomyopathy.

Randomized, Blinded, Placebo- and Positive-Controlled Crossover Study to Determine the Effect of Deferiprone on the QTc Interval in Healthy Subjects

This study evaluated whether deferiprone, an oral iron chelator, acts to prolong the QT interval. Fifty healthy volunteers received single doses of each of the following: therapeutic dose of deferiprone (33 mg/kg), supratherapeutic dose (50 mg/kg), placebo, or moxifloxacin, a positive control known to significantly prolong QT interval. Following each dose, subjects underwent cardiac monitoring, pharmacokinetics assessments, and safety assessments. Based on the QT interval obtained using the Fridericia correction for heart rate (QTcF), the upper bound of the 1-sided 95% confidence interval of the mean difference between deferiprone and placebo was <10 milliseconds (the threshold of concern defined by authorities) at all time points for both doses: maximum difference of 3.01 milliseconds for the therapeutic dose and 5.23 milliseconds for the supratherapeutic dose. The difference in dQTcF between moxifloxacin and placebo demonstrated that the study was adequately sensitive to detect a significant prolongation of QTcF. The concentration-response correlation analyses revealed some weak but statistically significant trends of increase in dQTcF and ddQTcF with increasing exposure to deferiprone, but these trends should have no clinical consequence even at the recommended maximum dosage. In conclusion, there was no clinically meaningful effect on QTc interval following single therapeutic or supratherapeutic doses of deferiprone.

Impact of Oxidative Stress in Premature Aging and Iron Overload in Hemodialysis Patients

Background. Increased oxidative stress is a well described feature of patients in hemodialysis. Their need for multiple blood transfusions and supplemental iron causes a significant iron overload that has recently been associated with increased oxidation of polyunsaturated lipids and accelerated aging due to DNA damage caused by telomere shortening. Methods. A total of 70 patients were evaluated concomitantly, 35 volunteers with ferritin levels below 500 ng/mL (Group A) and 35 volunteers with ferritin levels higher than 500 ng/mL (Group B). A sample of venous blood was taken to extract DNA from leukocytes and to measure relative telomere length by real-time PCR. Results. Patients in Group B had significantly higher plasma TBARS (p = 0.008), carbonyls (p = 0.0004), and urea (p = 0.02) compared with those in Group A. Telomeres were significantly shorter in Group B, 0.66 (SD, 0.051), compared with 0.75 (SD, 0.155) in Group A (p = 0.0017). We observed a statistically significant association between relative telomere length and ferritin levels (r = −0.37, p = 0.001). Relative telomere length was inversely related to time on hemodialysis (r = −0.27, p = 0.02). Conclusions. Our findings demonstrate that iron overload was associated with increased levels of oxidative stress and shorter relative telomere length.

Iron Overload Leading to Torsades de Pointes in β-Thalassemia and Long QT Syndrome

The authors present a unique case of torsades de pointes in a β-thalassemia patient with early iron overload in the absence of any structural abnormalities as seen in hemochromatosis. Genetic testing showed a novel KCNQ1 gene mutation 1591C>T [Gln531Ter(X)]. Testing of the gene mutation in Xenopus laevis oocytes showed loss of function of the IKs current. The authors hypothesize that iron overload combined with the KCNQ1 gene mutation leads to prolongation of QTc and torsades de pointes.

Iron-Sensitive Cardiac Magnetic Resonance Imaging for Prediction of Ventricular Arrhythmia Risk in Patients With Chronic Myocardial Infarction: Early Evidence

BACKGROUND

Recent canines studies have shown that iron deposition within chronic myocardial infarction (CMI) influences the electric behavior of the heart. To date, the link between the iron deposition and malignant ventricular arrhythmias in humans with CMI is unknown.

METHODS AND RESULTS

Patients with CMI (n=94) who underwent late-gadolinium-enhanced cardiac magnetic resonance imaging before implantable cardioverter-defibrillator implantation for primary and secondary preventions were retrospectively analyzed. The predictive values of hypointense cores (HIC) in balanced steady-state free precession images and conventional cardiac magnetic resonance imaging and ECG malignant ventricular arrhythmia parameters for the prediction of primary combined outcome (appropriate implantable cardioverter-defibrillator therapy, survived cardiac arrest, or sudden cardiac death) were studied. The use of HIC within CMI on balanced steady-state free precession as a marker of iron deposition was validated in a canine MI model (n=18). Nineteen patients met the study criteria with events occurring at a median of 249 (interquartile range of 540) days after implantable cardioverter-defibrillator placement. Of the 19 patients meeting the primary end point, 18 were classified as HIC+, whereas only 1 was HIC-. Among the cohort in whom the primary end point was not met, there were 28 HIC+ and 47 HIC- patients. Receiver operating characteristic curve analysis demonstrated an additive predictive value of HIC for malignant ventricular arrhythmias with an increased area under the curve of 0.87 when added to left ventricular ejection fraction (left ventricular ejection fraction alone, 0.68). Both cardiac magnetic resonance imaging and histological validation studies performed in canines demonstrated that HIC regions in balanced steady-state free precession images within CMI likely result from iron depositions.

CONCLUSIONS

Hypointense cores within CMI on balanced steady-state free precession cardiac magnetic resonance imaging can be used as a marker of iron deposition and yields incremental information toward improved prediction of malignant ventricular arrhythmias.

Comparison of tissue Doppler imaging with MRI t2* and 24-hour rhythm holter heart rate variability for diagnosing early cardiac impairment in thalassemia major patients

OBJECTIVES

Cardiology follow up is important in thalassemia major patients. The object of this study is to define parameters which can be used in the early detection of cardiac impairment.

MATERIAL AND METHODS

Forty seven beta thalassemia major patients (mean age 16.3 ± 4.47 years; 22 boys, 25 girls) whose left ventricular systolic functions were normal and a healthy control group of fifty age and gender matched children were included in the study. M-mode echocardiographic measurements, systolic and diastolic functions with PW and tissue Doppler and heart rate variabilities (HRVs) were compared between the two groups. The patients were also grouped according to MRT2*, ferritin and left ventricular diastolic diameters (LVDds) to compare the echocardiographic and Holter parameters among them.

RESULTS

None of the children in the study group had symptomatic congestive heart failure. PW Doppler late diastolic forward flow in pulmonary artery was higher in the thalassemia group when compared with the control group (P = 0.01) indicating decreased compliance of the right ventricle. While the systolic and diastolic functions were normal, all the HRV parameters in the thalassemia group were significantly lower than the control group (P = 0.005).

CONCLUSIONS

Significant decrease in HRV and increase in PW late diastolic forward flow in pulmonary artery in the absence of systolic or diastolic dysfunction, points out that these parameters can be useful in detection of early cardiac impairment.

Spatial repolarization heterogeneity detected by magnetocardiography correlates with cardiac iron overload and adverse cardiac events in beta-thalassemia major

Background

Patients with transfusion-dependent beta-thalassemia major (TM) are at risk for myocardial iron overload and cardiac complications. Spatial repolarization heterogeneity is known to be elevated in patients with certain cardiac diseases, but little is known in TM patients. The purpose of this study was to evaluate spatial repolarization heterogeneity in patients with TM, and to investigate the relationships between spatial repolarization heterogeneity, cardiac iron load, and adverse cardiac events.

Methods and Results

Fifty patients with TM and 55 control subjects received 64-channel magnetocardiography (MCG) to determine spatial repolarization heterogeneity, which was evaluated by a smoothness index of QT_c (SI-QT_c), a standard deviation of QT_c (SD-QT_c), and a QT_c dispersion. Left ventricular function and myocardial T2* values were assessed by cardiac magnetic resonance. Patients with TM had significantly greater SI-QT_c, SD-QT_c, and QT_c dispersion compared to the control subjects (all p values<0.001). Spatial repolarization heterogeneity was even more pronounced in patients with significant iron overload (T2*<20 ms, n = 20) compared to those with normal T2* (all p values<0.001). Log_e cardiac T2* correlated with SI-QT_c (r = −0.609, p<0.001), SD-QT_c (r = −0.572, p<0.001), and QT_c dispersion (r = −0.622, p<0.001), while all these indices had no relationship with measurements of the left ventricular geometry or function. At the time of study, 10 patients had either heart failure or arrhythmia. All 3 indices of repolarization heterogeneity were related to the presence of adverse cardiac events, with areas under the receiver operating characteristic curves (ranged between 0.79 and 0.86), similar to that of cardiac T2*.

Conclusions

Multichannel MCG demonstrated that patients with TM had increased spatial repolarization heterogeneity, which is related to myocardial iron load and adverse cardiac events.

Correlation between iron stores and QTc dispersion in chronic ambulatory peritoneal dialysis patients

AIM

We aimed to investigate the QT dispersion and corrected QT (QTc) dispersion which are suggested as the signals of ventricular arrhythmias, in patients on maintenance CAPD and to evaluate the correlation between iron stores and these electrocardiographic parameters.

MATERIALS AND METHOD

Fifty-eight patients on maintenance CAPD and 19 healthy age- and sex-matched adults without cardiac disease were included. The PD patients were divided into two groups according to whether their computerized measurements of QTc dispersion were longer than 65 ms.

RESULTS

Although QT interval was statistically significantly shorter in control group (34 ± 28 vs. 43 ± 34 ms; p < 0.05), there was no significant difference in regards to the QTc, QT dispersion and QTc dispersion between two groups. PD patients with QTc dispersion longer than 65 ms had higher levels of serum ferritin (p = 0.038) and transferrin saturation (TSAT; p = 0.022) than the others. QTc dispersion were positively correlated with ferritin (r = 0.469, p < 0.01) and TSAT (r = 0.430, p < 0.01) in CAPD patients.

CONCLUSION

Although prolonged QTc, QT dispersion and QTc dispersion were suggested as the markers of ventricular arrhythmias we did not find any significant difference in regards to these parameters between control patients and CAPD patients. But the high body iron stores in these patients increase the risk of increased QT dispersion. The concern over iron overload in dialysis patients is not only because of its oxidative toxicity, but also its precipitation of arrhythmias, which may be measured by the surrogate marker of QTc dispersion.

Iron deposition following chronic myocardial infarction as a substrate for cardiac electrical anomalies: initial findings in a canine model

Purpose

Iron deposition has been shown to occur following myocardial infarction (MI). We investigated whether such focal iron deposition within chronic MI lead to electrical anomalies.

Methods

Two groups of dogs (ex-vivo (n = 12) and in-vivo (n = 10)) were studied at 16 weeks post MI. Hearts of animals from ex-vivo group were explanted and sectioned into infarcted and non-infarcted segments. Impedance spectroscopy was used to derive electrical permittivity () and conductivity (). Mass spectrometry was used to classify and characterize tissue sections with (IRON+) and without (IRON-) iron. Animals from in-vivo group underwent cardiac magnetic resonance imaging (CMR) for estimation of scar volume (late-gadolinium enhancement, LGE) and iron deposition (T2*) relative to left-ventricular volume. 24-hour electrocardiogram recordings were obtained and used to examine Heart Rate (HR), QT interval (QT), QT corrected for HR (QTc) and QTc dispersion (QTcd). In a fraction of these animals (n = 5), ultra-high resolution electroanatomical mapping (EAM) was performed, co-registered with LGE and T2* CMR and were used to characterize the spatial locations of isolated late potentials (ILPs).

Results

Compared to IRON- sections, IRON+ sections had higher, but no difference in. A linear relationship was found between iron content and (p<0.001), but not (p = 0.34). Among two groups of animals (Iron (<1.5%) and Iron (>1.5%)) with similar scar volumes (7.28%±1.02% (Iron (<1.5%)) vs 8.35%±2.98% (Iron (>1.5%)), p = 0.51) but markedly different iron volumes (1.12%±0.64% (Iron (<1.5%)) vs 2.47%±0.64% (Iron (>1.5%)), p = 0.02), QT and QTc were elevated and QTcd was decreased in the group with the higher iron volume during the day, night and 24-hour period (p<0.05). EAMs co-registered with CMR images showed a greater tendency for ILPs to emerge from scar regions with iron versus without iron.

Conclusion

The electrical behavior of infarcted hearts with iron appears to be different from those without iron. Iron within infarcted zones may evolve as an arrhythmogenic substrate in the post MI period.

Cardiovascular function and treatment in β-thalassemia major: a consensus statement from the American Heart Association

This aim of this statement is to report an expert consensus on the diagnosis and treatment of cardiac dysfunction in β-thalassemia major (TM). This consensus statement does not cover other hemoglobinopathies, including thalassemia intermedia and sickle cell anemia, in which a different spectrum of cardiovascular complications is typical. There are considerable uncertainties in this field, with a few randomized controlled trials relating to treatment of chronic myocardial siderosis but none relating to treatment of acute heart failure. The principles of diagnosis and treatment of cardiac iron loading in TM are directly relevant to other iron-overload conditions, including in particular Diamond-Blackfan anemia, sideroblastic anemia, and hereditary hemochromatosis. Heart failure is the most common cause of death in TM and primarily results from cardiac iron accumulation. The diagnosis of ventricular dysfunction in TM patients differs from that in nonanemic patients because of the cardiovascular adaptation to chronic anemia in non-cardiac-loaded TM patients, which includes resting tachycardia, low blood pressure, enlarged end-diastolic volume, high ejection fraction, and high cardiac output. Chronic anemia also leads to background symptomatology such as dyspnea, which can mask the clinical diagnosis of cardiac dysfunction. Central to early identification of cardiac iron overload in TM is the estimation of cardiac iron by cardiac T2* magnetic resonance. Cardiac T2* <10 ms is the most important predictor of development of heart failure. Serum ferritin and liver iron concentration are not adequate surrogates for cardiac iron measurement. Assessment of cardiac function by noninvasive techniques can also be valuable clinically, but serial measurements to establish trends are usually required because interpretation of single absolute values is complicated by the abnormal cardiovascular hemodynamics in TM and measurement imprecision. Acute decompensated heart failure is a medical emergency and requires urgent consultation with a center with expertise in its management. The first principle of management of acute heart failure is control of cardiac toxicity related to free iron by urgent commencement of a continuous, uninterrupted infusion of high-dose intravenous deferoxamine, augmented by oral deferiprone. Considerable care is required to not exacerbate cardiovascular problems from overuse of diuretics or inotropes because of the unusual loading conditions in TM. The current knowledge on the efficacy of removal of cardiac iron by the 3 commercially available iron chelators is summarized for cardiac iron overload without overt cardiac dysfunction. Evidence from well-conducted randomized controlled trials shows superior efficacy of deferiprone versus deferoxamine, the superiority of combined deferiprone with deferoxamine versus deferoxamine alone, and the equivalence of deferasirox versus deferoxamine.

Chronic manifestation of postreperfusion intramyocardial hemorrhage as regional iron deposition: a cardiovascular magnetic resonance study with ex vivo validation

BACKGROUND

Intramyocardial hemorrhage frequently accompanies large reperfused myocardial infarctions. However, its influence on the makeup and the ensuing effect on the infarcted tissue during the chronic phase remain unexplored.

METHODS AND RESULTS

Patients (n=15; 3 women), recruited after successful percutaneous coronary intervention for first segment-elevation myocardial infarction, underwent cardiovascular magnetic resonance imaging on day 3 and month 6 after percutaneous coronary intervention. Patients with hemorrhagic (Hemo+) infarctions, as determined by T2* cardiovascular magnetic resonance on day 3 (n=11), showed persistent T2* losses colocalized with scar tissue on the follow-up scans, suggesting chronic iron deposition. T2* values of Hemo+ territories were significantly higher than nonhemorrhagic (Hemo-) and remote territories (P<0.001); however, T2* values of nonhemorrhagic (Hemo-) and remote territories were not different (P=0.51). Canines (n=20) subjected to ischemia-reperfusion injury (n=14) underwent cardiovascular magnetic resonance on days 3 and 56 after ischemia-reperfusion injury. Similarly, sham-operated animals (Shams; n=3) were imaged using cardiovascular magnetic resonance at similar time points. Subsequently, hearts were explanted and imaged ex vivo, and samples of Hemo+, Hemo-, remote, and Sham myocardium were isolated and stained. The extent of iron deposition ([Fe]) within each sample was measured using mass spectrometry. Hemo+ infarcts showed significant T2* losses compared with the other (control) groups (P<0.001), and Perls stain confirmed localized iron deposition. Mean [Fe] of Hemo+ was nearly an order of magnitude greater than that of the control groups (P<0.001), but no significant differences were observed among the control groups. A strong linear relationship was observed between log(T2*) and -log([Fe]); R(2)=0.7 and P<0.001. The monoclonal antibody Mac387 stains, along with Perls stains, showed preferential localization of newly recruited macrophages at the site of chronic iron deposition.

CONCLUSIONS

Hemorrhagic myocardial infarction can lead to iron depositions within the infarct zones, which can be a source of prolonged inflammatory burden in the chronic phase of myocardial infarction.

d-Propranolol protects against oxidative stress and progressive cardiac dysfunction in iron overloaded rats

d-Propranolol (d-Pro: 2-8 mg·(kg body mass)(-1)·day(-1)) protected against cardiac dysfunction and oxidative stress during 3-5 weeks of iron overload (2 mg Fe-dextran·(g body mass)(-1)·week(-1)) in Sprague-Dawley rats. At 3 weeks, hearts were perfused in working mode to obtain baseline function; red blood cell glutathione, plasma 8-isoprostane, neutrophil basal superoxide production, lysosomal-derived plasma N-acetyl-β-galactosaminidase (NAGA) activity, ventricular iron content, and cardiac iron deposition were assessed. Hearts from the Fe-treated group of rats exhibited lower cardiac work (26%) and output (CO, 24%); end-diastolic pressure rose 1.8-fold. Further, glutathione levels increased 2-fold, isoprostane levels increased 2.5-fold, neutrophil superoxide increased 3-fold, NAGA increased 4-fold, ventricular Fe increased 4.9-fold; and substantial atrial and ventricular Fe-deposition occurred. d-Pro (8 mg) restored heart function to the control levels, protected against oxidative stress, and decreased cardiac Fe levels. After 5 weeks of Fe treatment, echocardiography revealed that the following were depressed: percent fractional shortening (%FS, 31% lower); left ventricular (LV) ejection fraction (LVEF, 17%), CO (25%); and aortic pressure maximum (P(max), 24%). Mitral valve E/A declined by 18%, indicating diastolic dysfunction. Cardiac CD11b+ infiltrates were elevated. Low d-Pro (2 mg) provided modest protection, whereas 4-8 mg greatly improved LVEF (54%-75%), %FS (51%-81%), CO (43%-78%), P(max) (56%-100%), and E/A >100%; 8 mg decreased cardiac inflammation. Since d-Pro is an antioxidant and reduces cardiac Fe uptake as well as inflammation, these properties may preserve cardiac function during Fe overload.

Assessment of cardiac parameters in evaluation of cardiac functions in patients with thalassemia major

The aim of the study was to evaluate cardiac function and early cardiac dysfunction of patients followed as thalassemia major. In this study, the authors compared 100 patients, diagnosed as thalassemia major with mean age 11.84 ± 4.35, with 60 healthy control subjects at the same age between 2008 and 2011. Early diagnosis of iron overload that may occur after repeated transfusions is important in this patient group. To detect early iron accumulation, the authors compared ferritin with the echo findings, the 24-hour Holter, and cardiac magnetic resonance imaging (MRI) T2* values in the patients of same age and sex, treated with chelators, without heart failure, nonsplenectomized, and do not differ in the presence of hepatitis C. Ferritin levels, left ventricular systolic functions (ejection fraction [EF], shortening fraction [SF]), left ventricular measurements, left ventricular diastolic functions, T2* image on cardiac magnetic resonance, heart rate variables in 24 hours, and Holter rhythm were evaluated to show the early failure of cardiac functions. In this study the authors confirmed that iron-related cardiac toxicity damages electrical activity earlier than myocardial contractility. Left ventricular diastolic diameter (LVDd), left ventricular mass (LVM), and LV systolic diameter (LVDs) levels were significantly higher in the patient group with ectopia. Patients with ectopia are the ones in whom LVM and LVDd are increased. In thalassemia major patients with ectopia, LF/HF ratio was markedly increased, QTc dispersion was clearly found higher in patients with ectopia rather than nonectopic patients. The standard deviation all normal RR interval series (SDNN) was found clearly lower in thalassemia major group with ectopia than control group because it is assumed that increase in cardiac sympathetic neuronal activity is related to exposure to chronic diastolic and systolic failure.

Iron overload decreases CaV1.3-dependent L-type Ca2+ currents leading to bradycardia, altered electrical conduction, and atrial fibrillation

BACKGROUND

Chronic iron overload (CIO) is associated with blood disorders such as thalassemias and hemochromatosis. A major prognostic indicator of survival in patients with CIO is iron-mediated cardiomyopathy characterized by contractile dysfunction and electrical disturbances, including slow heart rate (bradycardia) and heart block.

METHODS AND RESULTS

We used a mouse model of CIO to investigate the effects of iron on sinoatrial node (SAN) function. As in humans, CIO reduced heart rate (≈20%) in conscious mice as well as in anesthetized mice with autonomic nervous system blockade and in isolated Langendorff-perfused mouse hearts, suggesting that bradycardia originates from altered intrinsic SAN pacemaker function. Indeed, spontaneous action potential frequencies in SAN myocytes with CIO were reduced in association with decreased L-type Ca(2+) current (I(Ca,L)) densities and positive (rightward) voltage shifts in I(Ca,L) activation. Pacemaker current (I(f)) was not affected by CIO. Because I(Ca,L) in SAN myocytes (as well as in atrial and conducting system myocytes) activates at relatively negative potentials due to the presence of Ca(V)1.3 channels (in addition to Ca(V)1.2 channels), our data suggest that elevated iron preferentially suppresses Ca(V)1.3 channel function. Consistent with this suggestion, CIO reduced Ca(V)1.3 mRNA levels by ≈40% in atrial tissue (containing SAN) and did not lower heart rate in Ca(V)1.3 knockout mice. CIO also induced PR-interval prolongation, heart block, and atrial fibrillation, conditions also seen in Ca(V)1.3 knockout mice.

CONCLUSIONS

Our results demonstrate that CIO selectively reduces Ca(V)1.3-mediated I(Ca,L), leading to bradycardia, slowing of electrical conduction, and atrial fibrillation as seen in patients with iron overload.

Iron overload cardiomyopathy: better understanding of an increasing disorder

The prevalence of iron overload cardiomyopathy (IOC) is increasing. The spectrum of symptoms of IOC is varied. Early in the disease process, patients may be asymptomatic, whereas severely overloaded patients can have terminal heart failure complaints that are refractory to treatment. It has been shown that early recognition and intervention may alter outcomes. Biochemical markers and tissue biopsy, which have traditionally been used to diagnose and guide therapy, are not sensitive enough to detect early cardiac iron deposition. Newer diagnostic modalities such as magnetic resonance imaging are noninvasive and can assess quantitative cardiac iron load. Phlebotomy and chelating drugs are suboptimal means of treating IOC; hence, the roles of gene therapy, hepcidin, and calcium channel blockers are being actively investigated. There is a need for the development of clinical guidelines in order to improve the management of this emerging complex disease.

Remission of paroxysmal atrial fibrillation with iron reduction in haemophilia A

SUMMARY

Two male first cousins with mild haemophilia A had baseline factor VIII levels of 12-15% and experienced bleeding requiring coagulation factor infusion therapy with trauma and surgical procedures. Both the patients with haemophilia A also had electrocardiographically documented symptomatic paroxysmal atrial fibrillation (PAF) for several years that had become resistant to pharmacological suppression. Radiofrequency ablation was considered in both the cases but deferred considering refusal of consent by the patients to undergo the procedure. Remission of arrhythmias has been reported in patients with iron-overload syndromes. Body iron stores assessed by serum ferritin levels were elevated in both men but neither had the C282Y or H63D genes for haemochromatosis. Calibrated reduction of iron stores by serial phlebotomy, avoiding iron deficiency, was followed by remission of symptomatic PAF in both cases. Iron reduction may be an effective treatment for arrhythmias apart from the classic iron-overload syndromes and deserves further study particularly in patients with bleeding disorders who might be at risk for arrhythmias and other diseases of ageing.

Clinical consequences of iron overload from chronic red blood cell transfusions, its diagnosis, and its management by chelation therapy

Iron overload from chronic transfusion therapy can be extremely toxic. Excess transfusional iron is deposited in the liver, heart, and other organs as free iron, which can cause organ dysfunction and damage over time. Increased awareness of the risk of iron overload in patients requiring chronic transfusion therapy is needed, and such patients should be screened for hyperferritinemia. Those with serial serum ferritin levels exceeding 1000 ng/mL and a total infused red blood cell volume of 120 mL/kg of body weight or more should be treated with chelation therapy and then monitored to ensure that treatment adequately reduces iron levels.

Iron overload and toxicity: the hidden risk of multiple blood transfusions

BACKGROUND

The quantity of iron in body is carefully regulated, primarily by control of iron absorption, and excess total body iron can be extremely toxic. Since humans have no mechanism for elimination of excess iron, multiple transfusions of red blood cells, which are required for the management of a number of disorders, inevitably result in iron overload. Cumulative iron overload, in turn, leads to iron toxicity with organ dysfunction and damage.

MATERIALS

This review examines the relationship between iron metabolism and hematologic disorders treated with multiple transfusions, with emphasis on the diagnosis and current methods of management of iron overload and toxicity in transfusion-dependent patients. Primarily using key words, we identified and reviewed more than 100 pertinent articles in English and other languages in the Medline database plus an additional number of abstracts of presentations at recent meetings of relevant scientific associations.

RESULTS

Transfusion-dependent disorders include those characterized by decreased red blood cell production, increased red blood cell destruction, or chronic blood loss. Patients receiving chronic transfusion therapy should be screened and monitored for iron overload, yet in our opinion, this is not always done routinely. Once iron overload has been identified, it should be treated to reduce the risk of morbidity and mortality from iron toxicity, which particularly affects the liver and heart.

CONCLUSION

Increased awareness of the risks of iron overload from chronic transfusion therapy should result in greater use of interventions such as iron chelation to reduce total body iron and the risk of long-term sequelae.

Iron overload thalassemic cardiomyopathy: iron status assessment and mechanisms of mechanical and electrical disturbance due to iron toxicity

Patients with thalassemia major have inevitably suffered from complications of the disease, due to iron overload. Among such complications, cardiomyopathy is the leading cause of morbidity and mortality (63.6% to 71%). The major causes of death in this group of patients are congestive heart failure and fatal cardiac tachyarrhythmias leading to sudden cardiac death. The free radical-mediated pathway is the principal mechanism of iron toxicity. The consequent series of events caused by iron overload lead to catastrophic cardiac effects. The authors review the electrophysiological and molecular mechanisms, pathophysiology and correlated clinical insight of heart failure and arrhythmias in iron overload thalassemic cardiomyopathy.

Influence of iron chelators on myocardial iron and cardiac function in transfusion-dependent thalassaemia: a systematic review and meta-analysis

Iron chelators have dramatically prolonged the life expectancy of patients with transfusion-dependent thalassaemia, but their precise clinical benefit in reducing the myocardial iron burden and improving cardiac function is unknown. This systematic review and meta-analysis included published clinical trials that assessed the efficacy of iron chelators in regularly transfused patients of thalassaemia major for two commonly reported outcomes - myocardial iron content and left ventricular ejection fraction (LVEF). The meta-analysis of 392 patients for myocardial iron content and 291 patients for LVEF showed that (i) iron chelators reduced cardiac iron content by 23.9% (95% confidence interval 17.3-29.8%); (ii) there was no significant difference between the amount of iron reduced by deferoxamine and deferiprone (P = 0.9504); and (iii) LVEF was not significantly influenced by iron chelators - summary Hedge's g 0.13 (95% confidence interval -0.10-0.36). A significant publication bias existed for LVEF (Egger's P = 0.049) but not for myocardial iron (Egger's P = 0.871). Our results indicate that iron chelators significantly reduce myocardial iron content. Further, the choice of deferoxamine versus deferiprone may rest on factors other than their efficacy to reduce cardiac iron load.

Increased QT variability in young asymptomatic patients with beta-thalassemia major

BACKGROUND

Despite recent progress in iron chelation therapy, sudden cardiac death due to malignant ventricular arrhythmias remains a vexing, clinical problem in patients with beta-thalassemia major (TM). In this study we assessed whether the major indices of QT variability, emerging tools for risk stratification of sudden cardiac death, differ in young asymptomatic patients with TM and healthy persons.

METHODS

Thirty patients with TM and 30 healthy control subjects underwent a 5-min electrocardiography recording to calculate the following variables: QT variance (QT(v)), QT(v) normalized for mean QT (QTVN) and QT variability index (QTVI). All subjects also underwent a two-dimensional and Doppler echocardiography study and magnetic resonance imaging (MRI) to determine cardiac and hepatic T2* values.

RESULTS

No differences were observed in clinical and conventional echo-Doppler findings in healthy control subjects and patients with TM whereas QT(v), QTVN and QTVI values were significantly higher in patients than those in controls (QT(v), P < 0.001; QTVN, P < 0.05 and QTVI, P < 0.001) and cardiac T2* and hepatic MRI T2* values were significantly lower in patients with TM (P < 0.001). The indices of temporal QT variability correlated significantly with MRI data.

CONCLUSIONS

Young asymptomatic patients with TM have increased cardiac repolarization variability as assessed by QT variability indices, probably due to cardiac iron deposition. These easily assessed, non-invasive markers could be used to identify increased myocardial repolarization lability early in asymptomatic patients with TM.

Evaluation of QT dispersion in beta thalassaemia major patients

Cardiac complications are considered to be the primary cause of death in patients with beta thalassaemia major. QT dispersion is a marker variability of ventricular repolarization and is elevated in various high risk groups of patients. This study was carried out in patients with beta thalassaemia major to evaluate QT dispersion and to investigate the relationship between QT dispersion and body iron load. Sixty-two beta thalassaemia major patients were enrolled into the study. The average serum ferritin levels and liver iron concentration was assessed. For each patient, QT-QTc intervals and QT-QTc dispersions were calculated and V1S and V5R were measured. All the subjects underwent two-dimensional M mode echocardiogram and Doppler study. LVMI was found higher in thalassaemia major patients compared to control group. beta thalassaemia major patients showed significantly higher mean QT, QTc, QTd, and QTcd values compared to the control group. The mean V5R and V1S amplitudes were also higher in beta thalassaemia major patients. There was a positive correlation between LVMI and QTc, QTd and QTcd. However, there was no significant correlation between QT dispersion and serum ferritin and liver iron concentration. Prospective longitudinal studies are needed to assess the prognostic significance of these findings.

Role of L-type Ca2+ channels in iron transport and iron-overload cardiomyopathy

Excessive body iron or iron overload occurs under conditions such as primary (hereditary) hemochromatosis and secondary iron overload (hemosiderosis), which are reaching epidemic levels worldwide. Primary hemochromatosis is the most common genetic disorder with an allele frequency greater than 10% in individuals of European ancestry, while hemosiderosis is less common but associated with a much higher morbidity and mortality. Iron overload leads to iron deposition in many tissues especially the liver, brain, heart and endocrine tissues. Elevated cardiac iron leads to diastolic dysfunction, arrhythmias and dilated cardiomyopathy, and is the primary determinant of survival in patients with secondary iron overload as well as a leading cause of morbidity and mortality in primary hemochromatosis patients. In addition, iron-induced cardiac injury plays a role in acute iron toxicosis (iron poisoning), myocardial ischemia–reperfusion injury, Friedreich ataxia and neurodegenerative diseases. Patients with iron overload also routinely suffer from a range of endocrinopathies, including diabetes mellitus and anterior pituitary dysfunction. Despite clear connections between elevated iron and clinical disease, iron transport remains poorly understood. While low-capacity divalent metal and transferrin-bound transporters are critical under normal physiological conditions, L-type Ca²⁺ channels (LTCC) are high-capacity pathways of ferrous iron (Fe²⁺) uptake into cardiomyocytes especially under iron overload conditions. Fe²⁺ uptake through L-type Ca²⁺ channels may also be crucial in other excitable cells such as pancreatic beta cells, anterior pituitary cells and neurons. Consequently, LTCC blockers represent a potential new therapy to reduce the toxic effects of excess iron.

QT interval dispersion in dialysis patients

The leading cause of mortality in dialysis patients is cardiovascular complications, including ventricular arrhythmias and sudden cardiac death. A reliable non-invasive predictive test of sudden death is therefore important. The interlead variation in duration of the QT interval on the surface electrocardiogram corrected with heart rate (QTc dispersion) might serve as a surrogate for ventricular arrhythmia. Prolonged QTc dispersion is commonly encountered in dialysis patients and possesses an increased risk of all mortality, including cardiovascular mortality. QT dispersion might be affected by shifts of the intracellular electrolytes during dialysis and increasing deposition of iron in cardiac muscles in these patients who have underlying heart diseases. Although no well-designed study has been done, the factors contributing to prolongation of QTc dispersion should be avoided. We summarize the results of the currently available clinical studies that examined QTc dispersion in dialysis patients.

Taurine Supplementation Reduces Oxidative Stress and Improves Cardiovascular Function in an Iron-Overload Murine Model

BACKGROUND

Iron overload has an increasing worldwide prevalence and is associated with significant cardiovascular morbidity and mortality. Elevated iron levels in the myocardium lead to impaired systolic and diastolic function and elevated oxidative stress. Taurine accounts for 25% to 50% of the amino acid pool in myocardium, possesses antioxidant properties, and can inhibit L-type Ca2+ channels. Thus, we hypothesized that this agent would reduce the cardiovascular effects of iron overload.

METHODS AND RESULTS

Iron-overloaded mice were generated by intraperitoneal injection of iron either chronically (5 days per week for 13 weeks) or subacutely (5 days per week for 4 weeks). Iron overload causes increased mortality, elevated oxidative stress, systolic and diastolic dysfunction, hypotension, and bradycardia. Taurine supplementation increased myocardial taurine levels by 45% and led to reductions in mortality and improved cardiac function, heart rate, and blood pressure in iron-overloaded mice. Histological examination of the myocardium revealed reduced apoptosis and interstitial fibrosis in iron-overloaded mice supplemented with taurine. Taurine mediated reduced oxidative stress in iron-overloaded mice along with attenuation of myocardial lipid peroxidation and protection of reduced glutathione level.

CONCLUSIONS

These results demonstrate that treatment with taurine reduces iron-mediated myocardial oxidative stress, preserves cardiovascular function, and improves survival in iron-overloaded mice. The role of taurine in protecting reduced glutathione levels provides an important mechanism by which oxidative stress-induced myocardial damage can be curtailed. Taurine, as a dietary supplement, represents a potential new therapeutic agent to reduce the cardiovascular burden from iron-overload conditions.