Increased QT dispersion in sickle cell disease: effect of pulmonary hypertension

Cardiovascular Consequences of Sickle Cell Disease

Background

Sickle cell disease is an inherited blood disorder which can lead to severe complications, particularly in the cardiovascular and respiratory systems, potentially resulting in arrhythmias, pulmonary hypertension (PH), and cardiomegaly. This study aims to investigate the risk of PH and arrhythmias in adult SCD patients.

Methods

Retrospective analysis of medical records from King Abdulaziz University Hospital (KAUH) for patients with SCD aged 15 and above between 2009 and 2021. The study included 517 patients, with echocardiograms and electrocardiograms assessed according to the European Society of Cardiology/the European Respiratory Society (ESC/ERS) guidelines for categorizing PH risk (low, moderate, high) and detecting arrhythmias. Data analysis employed the Statistical Package for the Social Sciences (SPSS), utilizing quantitative and qualitative data representation. Multivariate logistic regression identified independent risk factors with odds ratios at a 95% confidence interval (CI).

Results

Among participants, 50.3% were male, with a total sample average age of 34.45 ± 9.28 years. Results indicated that 1.4% of patients experienced arrhythmias, 3.7% had a moderate PH risk, and 3.3% were classified as high PH risk. Logistic regression revealed significant independent risk factors for PH and arrhythmia in patients with SCD, with chronic kidney disease (CKD) carrying the highest odds (26.4 times higher odds of PH and 15.36 times higher odds of arrhythmias).

Conclusion

Patients with SCD are at risk for developing PH and various arrhythmias but are often underdiagnosed. Key risk factors for PH included CKD, liver cirrhosis, and pre-existing cardiac conditions. Arrhythmias were significantly associated with CKD and pre-existing cardiac conditions. To mitigate these risks, we recommend involving a multidisciplinary healthcare team in the care of adult patients with SCD. Future prospective studies are advised for early detection of PH and arrhythmias in hemoglobinopathy patients, potentially reducing mortality.

Genetic variants and effect modifiers of QT interval prolongation in patients with sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is a common inherited blood disorder among African Americans (AA), with premature mortality which has been associated with prolongation of the heart rate-corrected QT interval (QTc), a known risk factor for sudden cardiac death. Although numerous genetic variants have been identified as contributors to QT interval prolongation in the general population, their impact on SCD patients remains unclear. This study used an unweighted polygenic risk score (PRS) to validate the previously identified associations between SNPs and QTc interval in SCD patients, and to explore possible interactions with other factors that prolong QTc interval in AA individuals with SCD.

METHODS

In SCD patients, candidate genetic variants associated with the QTc interval were genotyped. To identify any risk SNPs that may be correlated with QTc interval prolongation, linear regression was employed, and an unweighted PRS was subsequently constructed. The effect of PRS on the QTc interval was evaluated using linear regression, while stratification analysis was used to assess the influence of serum alanine transaminase (ALT), a biomarker for liver disease, on the PRS effect. We also evaluated the PRS with the two subcomponents of QTc, the QRS and JTc intervals.

RESULTS

Out of 26 candidate SNPs, five risk SNPs were identified for QTc duration under the recessive model. For every unit increase in PRS, the QTc interval prolonged by 4.0 ms (95% CI: [2.0, 6.1]; p-value: <0.001) in the additive model and 9.4 ms in the recessive model (95% CI: [4.6, 14.1]; p-value: <0.001). Serum ALT showed a modification effect on PRS-QTc prolongation under the recessive model. In the normal ALT group, each PRS unit increased QTc interval by 11.7 ms (95% CI: [6.3, 17.1]; p-value: 2.60E-5), whereas this effect was not observed in the elevated ALT group (0.9 ms; 95% CI: [-7.0, 8.8]; p-value: 0.823).

CONCLUSION

Several candidate genetic variants are associated with QTc interval prolongation in SCD patients, and serum ALT acts as a modifying factor. The association of a CPS1 gene variant in both QTc and JTc duration adds to NOS1AP as evidence of involvement of the urea cycle and nitric oxide metabolism in cardiac repolarization in SCD. Larger replication studies are needed to confirm these findings and elucidate the underlying mechanisms.

Clinical and Laboratory Correlates of QTc Duration in Adult and Pediatric Sickle Cell Disease

Background

Sickle cell disease, a common genetic disorder in African Americans, manifests an increased risk of sudden death, the basis of which is incompletely understood. Prolongation of heart rate-corrected QT (QTc) interval on the electrocardiogram, a standard clinical measure of cardiac repolarization, may contribute to sudden death by predisposing to torsades de pointes ventricular tachycardia.

Methods

We established a cohort study of 293 adult and 121 pediatric sickle cell disease patients drawn from the same geographic region as the Jackson Heart Study (JHS) cohort, in which significant correlates of QT duration have been characterized and quantitatively modeled. Herein, we establish clinical and laboratory correlates of QTc duration in our cohort using stepwise multivariate linear regression analysis. We then compared our adult sickle cell disease data to effect-size predictions from the published JHS statistical model of QT interval duration.

Results

In adult sickle cell disease, gender, diuretic use, QRS duration, serum ALT levels, anion gap, and diastolic blood pressure show positive correlation; hemoglobin levels show inverse correlation; in pediatric sickle cell disease, age, hemoglobin levels, and serum bicarbonate and creatinine levels show inverse correlation. The mean QTc in our adult sickle cell disease cohort is 7.8 milliseconds longer than in the JHS cohort, even though the JHS statistical model predicts that the mean QTc in our cohort should be > 11 milliseconds shorter than in the much older JHS cohort, a differential of > 18 milliseconds.

Conclusion

Sickle cell disease patients have substantial QTc prolongation relative to their age, driven by factors some overlapping, in adult and pediatric sickle cell disease, and distinct from those that have been defined in the general African American community.

Assessment of Ventricular Repolarization in Sickle Cell Anemia Patients: The Role of QTc Interval, Tp-e Interval and Tp-e/QTc Ratio and Its Gender Implication

Background

Many specific and non-specific electrocardiographic abnormalities including ventricular arrhythmias have been reported in subjects with sickle cell anemia (SCA). In SCA patients, cardiac electrical abnormalities may be the leading cause of increased risk of arrhythmias. The corrected QT (QTc) interval, peak to the end of the T wave (Tp-e) interval and associated Tp-e/QTc ratio are promising measures of altered ventricular repolarization and increased arrhythmogenesis risk.

Aim

This study assessed ventricular repolarization abnormalities in subjects with SCA using the QTc interval, Tp-e interval and Tp-e/QTc ratio, and also evaluated the gender differences in these parameters, as well as their determinants.

Methods

Sixty subjects with SCA and 60 healthy control subjects, matched for age and gender, were studied. All participants underwent physical examination, hematological and biochemical evaluation, and 12-lead electrocardiography (ECG) recording. QT and Tp-e intervals were measured from the ECG, and the QTc interval was calculated using Bazett’s formula. Tp-e/QT and Tp-e/QTc ratios were also derived.

Results

QT and QTc intervals were prolonged in subjects with SCA. Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio were prolonged in male SCA subjects, with a paradoxical shortening in female SCA subjects. Plasminogen activator inhibitor-1 (PAI-1) was an independent determinant of QTc, while body mass index (BMI) was an independent determinant of both Tp-e interval and Tp-e/QTc ratio.

Conclusion

Our results suggest an elevated risk for ventricular arrhythmogenesis in male SCA subjects. Furthermore, increased BMI and PAI-1 level are possible markers of ventricular repolarization abnormalities in SCA subjects.

Altered cardiac repolarisation in highlanders with high-altitude pulmonary hypertension during wakefulness and sleep

High-altitude pulmonary hypertension (HAPH) is an altitude-related illness associated with hypoxaemia that may promote sympathetic excitation and prolongation of the QT interval. The present case-control study tests whether QT intervals, markers of malignant cardiac arrhythmias, are prolonged in highlanders with HAPH (HAPH+) compared to healthy highlanders (HH) and healthy lowlanders (LL). The mean pulmonary artery pressure (mPAP) was measured by echocardiography in 18 HAPH+ (mPAP, 34 mmHg) and 18 HH (mPAP, 23 mmHg) at 3,250 m, and 18 LL (mPAP, 18 mmHg) at 760 m, Kyrgyzstan (p < .05 all mPAP comparisons). Groups were matched for age, sex and body mass index. Electrocardiography and pulse oximetry were continuously recorded during nocturnal polysomnography. The heart rate-adjusted QT interval, QTc, was averaged over consecutive 1-min periods. Overall, a total of 26,855 averaged 1-min beat-by-beat periods were semi-automatically analysed. In HAPH+, maximum nocturnal QTc was longer during sleep (median 456 ms) than wakefulness (432 ms, p < .05) and exceeded corresponding values in HH (437 and 419 ms) and LL (430 and 406 ms), p < .05, respectively. The duration of night-time QTc >440 ms was longer in HAPH+ (median 144 min) than HH and LL (46 and 14 min, p < .05, respectively). HAPH+ had higher night-time heart rate (median 78 beats/min) than HH and LL (66 and 65 beats/min, p < .05, respectively), lower mean nocturnal oxygen saturation than LL (88% versus 95%, p < .05) and more cyclic oxygen desaturations (median 24/hr) than HH and LL (13 and 3/hr, p < .05, respectively). In conclusion, HAPH was associated with higher night-time heart rate, hypoxaemia and longer QTc versus HH and LL, and may represent a substrate for increased risk of malignant cardiac arrhythmias.

Predictive value of P-wave and QT interval dispersion in children with congenital heart disease and pulmonary arterial hypertension for the occurrence of arrhythmias

OBJECTIVES

To evaluate P-wave dispersion (PWD) and QT dispersion (QTd) in children with congenital heart disease and pulmonary arterial hypertension (PAH-CHD) and to investigate the predictive value of both PWD and QTd for prediction of arrhythmias in such children.

MATERIALS AND METHODS

We included 40 children with PAH-CHD as Group I. Forty other children with CHD and no PAH were included as Group II. Forty healthy children of matched age and sex served as a Control group. Electrocardiography was performed to determine PWD and QTd. Furthermore, 24-hour Holter monitoring was performed to detect the presence of arrhythmias. Echocardiographic evaluation was also performed.

RESULTS

QTd and PWD were significantly higher in Group I than in Group II and Control group. A significant positive correlation was present between both QTd and PWD and mean pulmonary artery pressure, right ventricular diameter, pulmonary vascular resistance (PVR), and PVR to systemic vascular resistance ratio. QTd showed 93% sensitivity, 80% specificity, and 85% accuracy for prediction of occurrence of arrhythmias in patients with PAH-CHD at a cutoff point of 61 ms, whereas PWD showed 87% sensitivity, 80% specificity, and 85% accuracy for prediction of arrhythmias at a cutoff point of 32.5 ms in such patients. Logistic regression analysis showed that both QTd and PWD were good predictors for the occurrence of arrhythmias in children with PAH-CHD (p = 0.003 and p = 0.01, respectively).

CONCLUSIONS

PWD and QTd were good predictors for the occurrence of various arrhythmias in children with PAH-CHD.

Pulmonary hypertension among 5 to 18 year old children with sickle cell anaemia in Nigeria

BACKGROUND

Pulmonary hypertension (PHT) is a significant cause of mortality in patients with sickle cell disease (SCD). Few studies on PHT in SCD have been carried out in children. This study aimed to estimate the prevalence of PHT in children with sickle cell anaemia (SCA) and determine its clinical and laboratory correlates.

METHODS

In this cross sectional study, evaluation involved obtaining bio-data, history and physical examination findings in 175 SCA subjects with haemoglobin genotype SS aged 5 to 18 years and 175 age and sex matched controls with haemoglobin genotype AA. PHT was determined using peak Tricuspid Regurgitant Velocity (TRV) obtained from echocardiography as a marker. Complete blood count (CBC), lactate dehydrogenase (LDH) assay, reticulocyte count, foetal haemoglobin (HbF) estimation as well as Human Immunodeficiency Virus (HIV) I and II, Hepatitis B Virus (HBV) and Hepatitis C Virus (HCV) screening were done for patients with SCA.

RESULTS

The mean peak TRV of subjects with SCA and controls was 2.2 ± 0.4 m/s and 1.9 ± 0.3 m/s respectively and prevalence of PHT among children with SCA and controls was 22.9% and 2.3% respectively. PHT in SCA correlated negatively with body mass index, haematocrit and haemoglobin.

CONCLUSION

This study affirms that PHT prevalence is high in children with SCA in Nigeria. Cardiovascular examination for signs of PHT is recommended for children with SCA and if required, further echocardiographic assessment from as early as five years.

Lack of Effect of Rivipansel on QTc Interval in Healthy Adult African American Male Subjects

Rivipansel is a pan-selectin inhibitor in phase 3 development for the treatment of vaso-occlusive crises in patients with sickle cell disease. This single-dose, randomized, 3-period, 3-treatment (400 mg moxifloxacin open-label, 4 g rivipansel-blinded, and placebo-blinded) crossover study evaluated the effect of rivipansel on the QT/QTc interval in 48 healthy male African American subjects (age, 21-53 years; weight, 60-115 kg). Time-matched, placebo-adjusted change from baseline QT interval using Fridericia's correction method (QTcF) was determined using a repeated-measures mixed-effects model. The highest upper bound of the 2-sided 90% confidence interval (CI) for QTcF change was 3.22 milliseconds 3 hours postdose. Moxifloxacin showed the anticipated QTcF effect, indicating that the study had adequate sensitivity to detect changes in the QTcF interval. The study concluded that no QTcF effect was demonstrated with rivipansel compared with placebo, as the upper bound of the 2-sided 90%CI was less than 10 milliseconds at all times. Exposure-response modeling for rivipansel concentrations and change from baseline in QTcF data corroborated a lack of effect with rivipansel compared with placebo. Single doses of rivipansel 4 g by intravenous infusion over 20 minutes were well tolerated in this study.

Associations of Prolonged QTc in Sickle Cell Disease

Sudden death is a leading cause of mortality in sickle cell disease, implicating ventricular tachyarrhythmias. Prolonged QTc on an electrocardiogram (ECG), commonly seen with myocardial ischemia, is a known risk for polymorphic ventricular tachycardia (VT). We hypothesized that prolonged QTc is associated with mortality in sickle cell disease. ECG were analyzed from a cohort of 224 sickle patients (University of Illinois at Chicago, UIC) along with available laboratory, and echocardiographic findings, and from another cohort of 38 patients (University of Chicago, UC) for which cardiac MRI and free heme values were also measured. In the UIC cohort, QTc was potentially related to mortality with a hazard ratio (HR) of 1.22 per 10ms, (P = 0.015), and a HR = 3.19 (P = 0.045) for a QTc>480ms. In multivariate analyses, QTc remained significantly associated with survival after adjusting for inpatient ECG status (HR 1.26 per 10ms interval, P = 0.010) and genotype status [HR 1.21 per 10ms interval, P = 0.037). QTc trended toward association with mortality after adjusting for both LDH and hydroxyurea use (HR 1.21 per 10ms interval, P = 0.062) but was not significant after adjusting for TRV. In univariate analyses, QTc was related to markers of hemolysis including AST (P = 0.031), hemoglobin (P = 0.014), TR velocity (P = 0.036), higher in inpatients (P<0.001) and those with an SS compared to SC genotype (P<0.001) in the UIC cohort as well as to free heme in the UC cohort (P = 0.002). These findings support a relationship of prolonged QTc with hemolysis and potentially mortality in sickle cell disease.

Repolarization Patterns in Congenital Heart Disease

The aim of this study was to study the repolarization patterns in pediatric patients with cyanotic and acyanotic congenital heart diseases as prolonged QT indicates a myocardium at risk of ventricular arrhythmia. A cross-sectional case-control study included 50 patients with acyanotic congenital heart diseases and 50 patients with cyanotic congenital heart diseases who presented to Catheterization Unit of Cairo University Pediatric Hospital between March 2013 and June 2014. We included 50 healthy children as a control. For all the patients' measurement of oxygen saturation, echocardiography and 12-lead electrocardiogram (ECG) were done and the corrected QT (QTc) was measured. The mean QTc was significantly higher in acyanotic congenital heart diseases with volume overload than in control: 0.426 versus 0.4 s (p = 0.009). Increased left ventricular end-diastolic dimension was significantly associated with QTc prolongation (p = 0.01). Early repolarization was higher in congenital heart diseases (18 % in acyanotic patient, 48 % in cyanotic patients) than in control 6 %. Decreased oxygen saturation was significantly associated with early repolarization (p = 0.01). Prolonged QTc was higher in acyanotic congenital heart diseases with volume overload and increased left ventricular end diastolic dimension was a significant association. Decreased oxygen saturation was a significant association.

Cardiovascular complications and risk of death in sickle-cell disease

In sickle-cell disease, a point mutation in the β-globin chain causes haemoglobin to polymerise within erythrocytes during deoxygenation, altering red blood cell rheology and causing haemolysis. Improvements in health infrastructure, preventive care, and clinical treatments have reduced the morbidity and mortality of sickle-cell disease in developed countries. However, as these patients live longer, the chronic effects of sustained haemolytic anaemia and episodic vaso-occlusive events drive the development of end-organ complications. Cardiopulmonary organ dysfunction and chronic kidney injury have a large effect on morbidity and premature mortality, and typically accelerate in the second decade of life. These processes culminate in the development of pulmonary hypertension, left ventricular diastolic heart disease, dysrhythmia, and sudden death. In this Series paper, we review the mechanisms, clinical features, and epidemiology of major cardiovascular complications in patients with sickle-cell disease and discuss how screening and intervention could reduce their incidence.

Mechanisms linking red blood cell disorders and cardiovascular diseases

The present paper aims to review the main pathophysiological links between red blood cell disorders and cardiovascular diseases, provides a brief description of the latest studies in this area, and considers implications for clinical practice and therapy. Anemia is associated with a special risk in proatherosclerotic conditions and heart disease and became a new therapeutic target. Guidelines must be updated for the management of patients with red blood cell disorders and cardiovascular diseases, and targets for hemoglobin level should be established. Risk scores in several cardiovascular diseases should include red blood cell count and RDW. Complete blood count and hemorheological parameters represent useful, inexpensive, widely available tools for the management and prognosis of patients with coronary heart disease, heart failure, hypertension, arrhythmias, and stroke. Hypoxia and iron accumulation cause the most important cardiovascular effects of sickle cell disease and thalassemia. Patients with congenital chronic hemolytic anemia undergoing splenectomy should be monitored, considering thromboembolic and cardiovascular risk.

Cardiac autonomic dysfunction in sickle cell anaemia and its correlation with QT parameters

Background:

Abnormalities of QT parameters together with cardiac autonomic neuropathy (CAN) confer significant risks of cardiac morbidity and mortality in patients with diabetes mellitus. We questioned whether or not CAN influences occurrence of QT interval prolongation and dispersion in patients with sickle cell anaemia (SCA).

Materials and Methods:

Forty stable adult sickle cell patients with 44 healthy haemoglobin AA controls were studied. Baseline electrocardiograms were obtained and cardiovascular autonomic function tests were performed using standard protocols.

Results:

Mean corrected QT (QTc) in sickle cell patients was significantly higher (P = 0.001) than the mean of controls. Similarly, mean QT dispersion (QTcd) was higher (P = 0.001) in the former than in the latter. Mean QTc in patients with CAN was longer than patients with normal autonomic function (461 ± 26 ms versus 411 ± 23 ms), P = 0.001 (OR of 17.1, CI 3.48–83.71). Similarly, QTcd was higher (P = 0.001) in patients with CAN than those with normal cardiac autonomic function. Positive correlations were found between CAN with QTc and QTcd (r = 0.604, P = 0.001, r = 0.523, P = 0.001, respectively).

Conclusion:

CAN is a risk factor for abnormalities of QT parameters in SCA and both may be harbinger for cardiac death.

Asthma management in sickle cell disease

Asthma is a common comorbid factor in sickle cell disease (SCD). However, the incidence of asthma in SCD is much higher than expected compared to rates in the general population. Whether "asthma" in SCD is purely related to genetic and environmental factors or rather is the consequence of the underlying hemolytic and inflammatory state is a topic of recent debate. Regardless of the etiology, hypoxemia induced by bronchoconstriction and inflammation associated with asthma exacerbations will contribute to a cycle of sickling and subsequent complications of SCD. Recent studies confirm that asthma predisposes to complications of SCD such as pain crises, acute chest syndrome, and stroke and is associated with increased mortality. Early recognition and aggressive standard of care management of asthma may prevent serious pulmonary complications and reduce mortality. However, data regarding the management of asthma in SCD is very limited. Clinical trials are needed to evaluate the effectiveness of current asthma therapy in patients with SCD and coincident asthma, while mechanistic studies are needed to delineate the underlying pathophysiology.

Considerations for Care: Management of Asthma in the Child with Sickle Cell Disease

Asthma is difficult to diagnose in the child with sickle cell disease because symptoms and pulmonary function abnormalities are similar to the spectrum of pulmonary manifestations in sickle cell disease. There are no published reports of controlled trials of asthma medications in children with sickle cell disease. Thus, treatment decisions should be guided by the Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma (www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf). However, issues specific to children with sickle cell disease should be considered. Initial strategies should focus on control of environmental triggers, as effectiveness on asthma outcomes is proven and the cost for implementation can be low. Use of short- and long-acting β₂-agonists may prolong QTc, particularly in this population of children who already have a higher prevalence of prolonged QTc than the general population. Long-acting β₂-agonist use has been associated with life-threatening asthma exacerbations with potentially higher risks in African Americans. Montelukast has been reported to increase suicidal thinking and behavior, and persons with asthma and sickle cell disease are already at risk for these events. Oral corticosteroids in the treatment of acute chest syndrome may increase risk of readmission even in children with asthma. The lack of prospective controlled trials of asthma drug treatment in children with asthma and sickle cell disease compels us to move this issue forward.

Dispersion durations of P-wave and QT interval in children with congenital heart disease and pulmonary arterial hypertension

This study aimed to investigate homogeneity disorders of ventricular repolarization and atrial conduction via QT dispersion and P-wave dispersion in children with congenital heart disease (CHD) and pulmonary arterial hypertension (PAH). Three groups of 20 each were generated and involved in this study. The first group included 20 children with both CHD and PAH. The second group consisted of 20 children with CHD but no PAH, and the third group was composed of 20 age- and sex-matched healthy children. Electrocardiographic records were used to determine P-wave, QT, and corrected QT (QTc) dispersions. The pulmonary hypertension group compared with the group having no pulmonary hypertension and the control group showed a significantly longer P-wave dispersion duration (39.10 ± 9.54 vs. 26.30 ± 4.99 ms, p < 0.001; and 24.80 ± 6.94 ms, p < 0.001, respectively) and QT dispersion duration (52.80 ± 15.11 vs. 37.60 ± 6.00 ms, p < 0.001; and 35.00 ± 7.77 ms, p < 0.001, respectively). In addition, the durations of maximum QTc and QTc dispersion were significantly longer in pulmonary hypertension group than in the other two groups. The risk of atrial and ventricular arrhythmia was found to be increased in the patients with both CHD and PAH. Physicians should pay close attention to possible atrial and ventricular arrhythmias during the treatment and follow-up evaluation of these patients.

QTc prolongation is associated with impaired right ventricular function and predicts mortality in pulmonary hypertension

BACKGROUND

In rodent models of pulmonary hypertension (PH) and right ventricular hypertrophy (RVH), the QTc interval is prolonged, reflecting downregulation of repolarizing Kv channels in RV myocytes. The significance of QTc prolongation in human PH is unknown. We hypothesized that QTc prolongation occurs in human PH, is associated with RVH and decreased RV function, and predicts adverse prognosis.

METHODS

Patients receiving a PAH-specific therapy (a prostanoid, endothelin-receptor antagonist and/or a phosphodiesterase-5 inhibitor), who had a 12-lead electrocardiogram (ECG) (n=202) were compared to age- and sex-matched controls (n=100). The duration of QTc on ECG was correlated with invasive hemodynamics (n=156) and with the status of the RV, as measured by Brain Natriuretic Peptide (NT-proBNP, n=145) and magnetic resonance imaging (n=24). Survival of the entire PH cohort and a subgroup with WHO Groups 1 and 4 PAH was prospectively determined from the Social Security Death Index.

RESULTS

QTc intervals were longer in PH vs. controls (454.8 ± 29 ms vs. 429.8 ± 18 ms, p<0.001) and did not differ based on PAH-specific therapy. NT-proBNP increased proportionately with QTc and was higher for those in the upper quintile (QTc ≥ 480 ms) vs. those with QTc<480 ms (4004 ± 6682 pg/mL vs. 1501 ± 1822 pg/mL, p<0.001). The QTc interval also correlated directly with increasing RV end-diastolic volume (r=.67, p<0.001) and mass (r=.0.51, p<0.05), and inversely with RV ejection fraction (r=-.49, p<0.05). In the entire PH cohort and WHO Groups 1 and 4 subgroup, QTc ≥ 480 ms and cardiac index were independent predictors of mortality.

CONCLUSIONS

QTc prolongation in PH patients reflects the status of the RV and is an independent predictor of mortality.

Clinical and electrocardiographic evaluation of sickle-cell anaemia patients with pulmonary hypertension

Pulmonary hypertension is an emerging complication of sickle cell anaemia with associated increased risk of mortality. In order to evaluate the clinical and electrocardiographic findings in adult sickle-cell patients with pulmonary hypertension, a cross sectional study was conducted on sixty two sickle cell anaemia patients and sixty two age and sex matched normal controls. Elevated pulmonary artery pressures (PAP), defined by PAP ≥ 30 mm Hg on echocardiography, was demonstrated in 41.9% of patients with sickle cell anaemia and in 3.2% of the controls; χ² = 26.571, P < 0.001. Right ventricular hypertrophy, increased P-wave duration, QTc interval, and QTc dispersion were significantly associated with pulmonary hypertension. Significant correlation was found between mean PAP and (1) Frequency of crisis (Spearman correlation = 0.320; P = 0.011), (2) body mass index (Pearson's correlation = −0.297; P = 0.019), and (3) QTc interval (Pearson's correlation 0.261; P = 0.040). Pulmonary hypertension in adult sickle anaemia patients is associated with electrocardiographic evidence of right ventricular hypertrophy, and correlates significantly with frequency of vaso-occlusive crisis, and QTc interval. The observations by this study tend to suggest that these parameters could be useful for early detection and prevention of pulmonary hypertension in patients with sickle cell anaemia.

Asthma in sickle cell disease: implications for treatment

Objective. To review issues related to asthma in sickle cell disease and management strategies. Data Source. A systematic review of pertinent original research publications, reviews, and editorials was undertaken using MEDLlNE, the Cochrane Library databases, and CINAHL from 1947 to November 2010. Search terms were [asthma] and [sickle cell disease]. Additional publications considered relevant to the sickle cell disease population of patients were identified; search terms included [sickle cell disease] combined with [acetaminophen], [pain medications], [vitamin D], [beta agonists], [exhaled nitric oxide], and [corticosteroids]. Results. The reported prevalence of asthma in children with sickle cell disease varies from 2% to approximately 50%. Having asthma increases the risk for developing acute chest syndrome , death, or painful episodes compared to having sickle cell disease without asthma. Asthma and sickle cell may be linked by impaired nitric oxide regulation, excessive production of leukotrienes, insufficient levels of Vitamin D, and exposure to acetaminophen in early life. Treatment of sickle cell patients includes using commonly prescribed asthma medications; specific considerations are suggested to ensure safety in the sickle cell population. Conclusion. Prospective controlled trials of drug treatment for asthma in patients who have both sickle cell disease and asthma are urgently needed.

QT dispersion in patients with pulmonary embolism

BACKGROUND

Various ECG patterns have been associated with acute pulmonary embolism. However, there is no data regarding the association between QT interval measurements and pulmonary embolism. We aimed to investigate the association between QT dispersion and the severity of pulmonary embolism (PE).

METHODS

One hundred twenty-nine pulmonary embolism patients (mean age 58 ± 16.5 years) with ECGs obtained within the first 24 hours of hospital admission were included in the study. Patients were classified into low, intermediate and high-risk groups. We retrospectively measured ECG scores; maximum and minimum corrected QT intervals (QTc(max) and QTc(min)) and corrected QT interval dispersion (QTcd) in each risk group of patients.

RESULTS

There was an increasing ECG score through from low to high-risk PE [3 (Interquartile Range, IQR: 2), 5 (IQR: 6) and 10 (IQR: 7) p < 0.0001]. QT interval analysis showed that QTcd was higher in high-risk group than in low and intermediate-risk groups (59.5 ± 23.4, 69.2 ± 21, 95.9 ± 33.2, p <0.001 and p = 0.01, respectively). Patients who died after diagnosis had significantly higher QTcd values at baseline compared with the QTcd values of surviving patients (89.1 ± 45.5 to 65 ± 22.9, p = 0.001). The sensitivity of QTcd > 71.5 ms for prediction of mortality was 71% with a specificity of 73% (p = 0.001). We observed a strong correlation between QTcd and ECG score values (r = 0.69, p< 0.001). There was also a correlation between QTcd values and pulmonary artery pressure (PAP) (r = 0.27, p = 0.05).

CONCLUSION

QTcd is significantly increased in high-risk PE patients compared to intermediate and low-risk patients. In addition, QTcd is significantly correlated with ECG score and PAP.

Pulmonary hypertension in thalassemia

Pulmonary hypertension (PH) is common in thalassemia and contributes to mortality. Advancing age and a history of splenectomy are major risk factors in this population. The etiology of PH is multifactorial, involving a complex interaction of platelets, the coagulation system, erythrocytes, and endothelial cells along with inflammatory and vascular mediators. The long-term effect of splenectomy, red cell membrane pathology, coagulation abnormalities, low nitric oxide (NO) bioavailability, excess arginase activity, platelet activation, oxidative stress, iron overload, and chronic hemolysis play a role. The process of hemolysis disables the arginine-NO pathway through the simultaneous release of erythrocyte arginase and cell-free hemoglobin. Both NO and its obligate substrate arginine are rapidly consumed. The biological consequences of hemolysis on NO bioavailability ultimately translate into the clinical manifestations of PH. Guidelines for the management of PH in thalassemia have not yet been established; however, clinical trials are ongoing in an effort to guide future therapy.

Heart rate-corrected QT interval and QT dispersion in patients with pulmonary hypertension

OBJECTIVE

Heart rate-corrected QT interval (QTc) and QTc dispersion (QTcd) are increased and associated with ventricular arrhythmia and an increase in sudden death in a variety of diseases. This study aimed to examine QTc and QTcd in pulmonary hypertension and assess their relationship with pulmonary arterial pressure.

PATIENTS AND METHODS

A total of 201 patients who had undergone right heart catheterization for a preliminary diagnosis of pulmonary hypertension between December 2003 and July 2008 were included in the study. Resting 12-lead electrocardiogram was recorded. QT interval was measured manually and corrected using Bazett's formula. Patients were divided into groups with mild-to-moderate and severe pulmonary hypertension and a control group according to mean pulmonary arterial pressure.

RESULTS

In all observed cases, mean QTc was higher in severe pulmonary hypertension than in controls (428.6 +/- 32.8 ms vs. 411.1 +/- 28.4 ms, P = 0.018) and QTcd was higher in mild-to-moderate (60.1 +/- 17.2 ms) and severe pulmonary hypertension (63.9 +/- 20.5 ms) than in controls (47.3 +/- 10.6 ms) (P = 0.031; P = 0.004). In men, there was no significant difference in mean QTc and QTcd. In women, mean QTc was higher in severe pulmonary hypertension than in controls (436.1 +/- 39.4 ms vs. 407.6 +/- 24.8 ms, P = 0.037) and QTcd was higher in severe pulmonary hypertension (68.5 +/- 20.9 ms) than in both the controls (45.1 +/- 12.6 ms) and patients with mild-to-moderate pulmonary hypertension (58.6 +/- 14.7 ms) (P = 0.002; P = 0.003). In addition, in women with pulmonary hypertension, mean QTc and QTcd were positively correlated to mean pulmonary arterial pressure (r = 0.207, P = 0.03; r = 0.236, P = 0.012).

CONCLUSIONS

In women with pulmonary hypertension, mean QTc and QTcd are positively correlated to mean pulmonary arterial pressure and are significantly increased in patients with severe pulmonary hypertension.

Prolonged QTc interval in children and young adults with sickle cell disease at steady state

BACKGROUND

Prolongation of the QTc interval may be more common than previously believed among individuals with sickle cell disease (SCD). The clinical associations and natural history of QTc prolongation remain unclear in this population. Our objectives were to determine the prevalence of prolonged QTc and evaluate its relationship to clinical factors in children and young adults with SCD.

PROCEDURES

We analyzed data from subjects 10 to 25 years old with SCD enrolled in our pulmonary hypertension screening protocol. Screening included echocardiography (ECHO), 12-lead electrocardiogram (ECG) and laboratory testing at steady state. QTc interval >440 msec was considered prolonged.

RESULTS

ECG data from 76 subjects (57% male, mean age 14.2 +/- 3 years old, range 10-24) were analyzed. We observed prolonged QTc in 29/76 (38%) subjects. Despite evidence of left ventricular hypertrophy (LVH) in 50/76 (66%) subjects, the frequency of LVH was not significantly different in subjects with and without QTc prolongation. When compared to subjects with normal QTc, subjects with prolonged QTc had higher mean tricuspid regurgitant jet velocity (2.51 +/- 0.27 m/sec vs. 2.33 +/- 0.26 m/sec, P = 0.010) as well as higher mean lactate dehydrogenase (433 +/- 142 IU/L vs. 343 +/- 142 IU/L, P = 0.000) and aspartate aminotransferase (48 +/- 20 IU/L vs. 39 +/- 15 IU/L, P = 0.026). A larger proportion of subjects with prolonged QTc also had a history of recurrent acute chest syndrome (66% vs. 38%, P = 0.038).

CONCLUSIONS

We conclude that QTc prolongation is a frequent finding in SCD not associated with LVH. Elevated pulmonary pressures, hemolysis and acute chest syndrome may represent risk factors for prolonged QTc in this population.

QTc dispersion in hyperthyroidism and its association with pulmonary hypertension

BACKGROUND

Several studies have reported that hyperthyroidism is associated with prolonged QT interval corrected by the heart rate (QTc) and pulmonary hypertension (PHT).

METHODS

Forty-seven patients with newly diagnosed overt hyperthyroidism and 20 healthy people were enrolled in the study. Transthoracic echocardiography, 12-lead surface electrocardiogram, and thyroid hormone levels were studied at the time of enrollment and after achievement of euthyroid state with propylthiouracil treatment.

RESULTS

Baseline clinical characteristics were similar. However, heart rate (90.5+/-19.6 vs 79.2+/-13.7 bpm, P = 0.024), pulmonary artery systolic pressure (PASP) (26.0+/-12.0 vs 10.6+/-4.0 mmHg, P < 0.001), E deceleration time (DT) (191.8+/-25.6 vs 177.0+/-10.7 ms, P = 0.016), isovolumetric relaxation time (IVRT) (91.38+/-12.3 vs 79.6+/-10.5 ms, P < 0.001), and QTc dispersion (QTcD) (50.3+/-17.2 vs 38.9+/-11.6 ms, P = 0.009) were significantly higher in hyperthyroid patients compared to control group. Heart rate (to 74.1+/-13.8, P < 0.001), QTcD (to 37.3+/-10.1 ms, P < 0.001), DT (to 185.3+/-19.7 ms, P = 0.008), IVRT (to 88.6+/-10.3 ms, P = 0.056), and PASP (23.1+/-10.1 mmHg P < 0.001) were significantly decreased after achievement of euthyroid state. Although PHT was present in 16 patients before treatment only six patients still had PHT during euyhyroid state. Compared to patients with normal PASP, QTcD was significantly longer in patients with PHT (56.5+/-15.8 vs 37.9+/-12.8 mmHg P < 0.001). There were also significant correlations between QTcD and presence of PHT (r = 0.516, P < 0.001) and PASP (r = 0.401, P = 0.009).

CONCLUSIONS

Hyperthyroidism is a reversible cause of PHT and diastolic dysfunction. Increased QTcD observed in hyperthyroidism may be associated with PHT and diastolic dysfunction. These abnormal findings in hyperthyroidism often normalize with the achievement of euthyroid state.

Asthma management: reinventing the wheel in sickle cell disease

Asthma is a common comorbidity in sickle cell disease (SCD) with a reported prevalence of 30-70%. The high frequency of asthma in this population cannot be attributed to genetic predisposition alone, and likely reflects in part, the contribution of overlapping mechanisms shared between these otherwise distinct disorders. There is accumulating evidence that dysregulated arginine metabolism and in particular, elevated arginase activity contributes to pulmonary complications in SCD. Derangements of arginine metabolism are also emerging as newly appreciated mechanism in both asthma and pulmonary hypertension independent of SCD. Patients with SCD may potentially be at risk for an asthma-like condition triggered or worsened by hemolysis-driven release of erythrocyte arginase and low nitric oxide bioavailability, in addition to classic familial asthma. Mechanisms that contributed to asthma are complex and multifactorial, influenced by genetic polymorphisms as well as environmental and infectious triggers. Given the association of asthma with inflammation, oxidative stress and hypoxemia, factors known to contribute to a vasculopathy in SCD, and the consequences of these factors on sickle erythrocytes, comorbid asthma would likely contribute to a vicious cycle of sickling and subsequent complications of SCD. Indeed a growing body of evidence documents what should come as no surprise: Asthma in SCD is associated with acute chest syndrome, stroke, pulmonary hypertension, and early mortality, and should therefore be aggressively managed based on established National Institutes of Health Guidelines for asthma management. Barriers to appropriate asthma management in SCD are discussed as well as strategies to overcome these obstacles in order to provide optimal care.

Assessment of corrected QT interval in sickle-cell disease patients who undergo erythroapheresis

Extension of the QT interval is characterized by syncope and cardiac arrest and often occurs in association with medical therapies and procedures. Whether erythroapheresis (EPH) could influence the QT interval duration in patients with sickle cell disease (SCD) is not known. We aimed to investigate the effects of EPH on the heart rate-corrected QT (QTc) interval. The study included 25 patients with SCD who underwent 34 EPH procedures. Two independent observers measured QTc interval duration from electrocardiograms performed continuously for 3 min at three different points during the EPH procedures (prior to EPH, after completion of 50% EPH and 15 min after EPH). Multiple regression analysis was used to determine if the ionized plasma calcium, the level of plasma magnesium, citrate infusion rate and painful crisis significantly contributed to the QTc interval. There was a non-significant trend (P = 0.184) towards increased QTc in sickle cell patients during EPH compared with pre-EPH values. QTc prolongation (>440 ms) occurred in 72% of the procedures. Fifty percent QTc values returned to baseline after the procedure. The independent variables were not significantly associated with QTc interval. Exchange procedures can induce QTc prolongation in patients with SCD.