QT interval and long-term mortality risk in the Framingham Heart Study

QTc Interval: A frequently unrecognized electrocardiographic interval

The QT interval, an electrocardiographic temporal representation of the ventricular depolarization and repolarization, is an integral parameter that must be carefully evaluated to gather critical information regarding electrical instability that may cause malignant ventricular dysrhythmias or sudden cardiac death. The QT interval is affected by several inheritable and acquired factors, such as genetic mutations, electrolyte disturbances, and medication interactions. We strongly believe that prompt and accurate recognition of any QT interval abnormalities is critical in many clinical settings. This concise review article highlights the importance of accurate measurement of the QT interval, enhances understanding of the most prevalent factors yielding abnormalities within the QT interval and the prognostic value of the QT interval, as well as provides several key practical reminders for healthcare professionals to strengthen our clinical practice.

Prolongation of the QTc interval is associated with an increased risk of cardiovascular diseases: The Hoorn study

BACKGROUND/OBJECTIVE

Prolonged heart rate-corrected QT interval (QTc) on the electrocardiogram (ECG) is maybe associated with the occurrence of cardiovascular diseases (CVD), but the evidence is inconsistent. Therefore, we investigated whether baseline prolongation of the QTc interval is associated with CVD morbidity and mortality and its subtypes and whether glucose tolerance modifies this association in a population-based cohort study with a mean follow-up of 10.8 years.

METHODS

We analyzed a glucose tolerance stratified sample (N = 487) from the longitudinal population-based Hoorn Study cohort (age 64 ± 7 years, 48% female). Cox regression was used to investigate the association between sex-specific baseline QTc quartiles and CVD morbidity and mortality. The risk was also estimated per 10 ms increase in QTc. All analyses were adjusted for age, sex, smoking status, systolic blood pressure, prevalent CVD, glucose tolerance status, hypertension and total cholesterol. In addition, stratified analyses were conducted for glucose tolerance status.

RESULTS

During a mean follow-up of 10.8 years, 351 CVD events were observed. The adjusted hazard ratios (95% CI) for each 10 ms increase in QTc interval were 1.06 (95% CI: 1.02-1.10) for CVD, 1.06 (95% CI: 0.97-1.15) for acute myocardial infarction, 1.07 (95% CI: 1.01-1.13) for stroke, 1.12 (95% CI: 1.06-1.19) for heart failure, 1.04 (95% CI: 0.96-1.12) for peripheral arterial disease and 1.01 (95% CI:0.95-1.08) for coronary heart disease. Glucose tolerance status did not modify the association (P > 0.2).

CONCLUSION/INTERPRETATION

Prolongation of the QTc interval is associated with morbidity and mortality due to general CVD. Glucose tolerance status did not modify these associations.

Association between corrected QT interval and long-term cardiovascular outcomes in elderly patients who had undergone endovascular therapy for lower extremity arterial disease

Background

Population-based studies have reported the association between prolonged corrected QT (QTc) intervals and an increased risk of adverse cardiovascular events. Data regarding the association between longer QTc intervals and incident cardiovascular outcomes in patients with lower extremity arterial disease (LEAD) are scarce.

Objective

To examine the impact of QTc interval on long-term cardiovascular outcomes in elderly patients with symptomatic LEAD.

Methods

This cohort study extracted data from the Tzu-chi Registry of ENDovascular Intervention for Peripheral Artery Disease (TRENDPAD) and enrolled 504 patients aged ≥ 70 treated with endovascular therapy for atherosclerotic LEAD from July 1, 2005, to December 31, 2019. The main outcomes of interest were all-cause mortality and major adverse cardiovascular events (MACE). Multivariate analysis was conducted using the Cox proportional hazard model to determine independent variables. We performed interaction analysis between corrected QT and other covariates and Kaplan-Meier analysis to compare the outcome of interest among the groups stratified by the tercile of QTc intervals.

Results

A total of 504 patients [235 men (46.6%); mean age, 79.9 ± 6.2 years; mean QTc interval, 459 ± 33 msec] entered the final data analysis. We categorized the baseline patient characteristics according to terciles of QTc intervals. During the median follow-up time of 3.15 (interquartile ranges, 1.65-5.42) years, we noted 264 deaths and 145 MACEs. The 5-year rates of freedom from all-cause mortality (71% vs. 57% vs. 31%, P < 0.001) and MACEs (83% vs. 67% vs. 46%, P < 0.001) were significantly different among the tercile groups. Multivariate analysis showed that a 1-SD increase in the QTc interval increased the risk of all-cause mortality [hazard ratio (HR) 1.49, P < 0.001] and MACEs (HR 1.59, P < 0.001) after adjusting for other covariates. The interaction analysis showed that QTc interval and C-reactive protein levels were most strongly associated with death (HR = 4.88, 95% CI 3.09-7.73, interaction P < 0.001) and MACEs (HR = 7.83, 95% CI 4.14-14.79, interaction P < 0.001).

Conclusions

In elderly patients with symptomatic atherosclerotic LEAD, a prolonged QTc interval is associated with advanced limb ischemia, multiple medical comorbidities, increased risk of MACEs, and all-cause mortality.

Prolongation of the heart rate-corrected QT interval is associated with cardiovascular diseases: Systematic review and meta-analysis

BACKGROUND

Conflicting findings have described the association between prolonged heart rate-corrected QT interval (QTc) and cardiovascular disease.

AIMS

To identify articles investigating the association between QTc and cardiovascular disease morbidity and mortality, and to summarize the available evidence for the general and type 2 diabetes populations.

METHODS

A systematic search was performed in PubMed and Embase in May 2022 to identify studies that investigated the association between QTc prolongation and cardiovascular disease in both the general and type 2 diabetes populations. Screening, full-text assessment, data extraction and risk of bias assessment were performed independently by two reviewers. Effect estimates were pooled across studies using random-effect models.

RESULTS

Of the 59 studies included, 36 qualified for meta-analysis. Meta-analysis of the general population studies showed a significant association for: overall cardiovascular disease (fatal and non-fatal) (hazard ratio [HR] 1.68, 95% confidence interval [CI] 1.33-2.12; I²=69%); coronary heart disease (fatal and non-fatal) in women (HR 1.27, 95% CI 1.08-1.50; I²=38%; coronary heart disease (fatal and non-fatal) in men (HR 2.07, 95% CI 1.26-3.39; I²=78%); stroke (HR 1.59, 95% CI 1.29-1.96; I²=45%); sudden cardiac death (HR 1.60, 95% CI 1.14-2.25; I²=68%); and atrial fibrillation (HR 1.55, 95% CI 1.31-1.83; I²=0.0%). No significant association was found for cardiovascular disease in the type 2 diabetes population.

CONCLUSION

QTc prolongation was associated with risk of cardiovascular disease in the general population, but not in the type 2 diabetes population.

Prolonged QT Interval in Cirrhosis: Twisting Time?

Approximately 30% to 70% of patients with cirrhosis have QT interval prolongation. In patients without cirrhosis, QT prolongation is associated with an increased risk of ventricular arrhythmias, such as torsade de pointes (TdP). In cirrhotic patients, there is likely a significant association between the corrected QT (QTc) interval and the severity of liver disease, and possibly with increased mortality. We present a stepwise overview of the pathophysiology and management of acquired long QT syndrome in cirrhosis. The QT interval is mainly determined by ventricular repolarization. To compare the QT interval in time it should be corrected for heart rate (QTc), preferably by the Fridericia method. A QTc interval >450 ms in males and >470 ms in females is considered prolonged. The pathophysiological mechanism remains incompletely understood, but may include metabolic, autonomic or hormonal imbalances, cirrhotic heart failure and/or genetic predisposition. Additional external risk factors for QTc prolongation include medication (IKr blockade and altered cytochrome P450 activity), bradycardia, electrolyte abnormalities, underlying cardiomyopathy and acute illness. In patients with cirrhosis, multiple hits and cardiac-hepatic interactions are often required to sufficiently erode the repolarization reserve before long QT syndrome and TdP can occur. While some risk factors are unavoidable, overall risk can be mitigated by electrocardiogram monitoring and avoiding drug interactions and electrolyte and acidbase disturbances. In cirrhotic patients with prolonged QTc interval, a joint effort by cardiologists and hepatologists may be useful and significantly improve the clinical course and outcome.

Heart rate-corrected QT interval prolongation is associated with decreased heart rate variability in patients with type 2 diabetes

We investigated the association between the heart rate-corrected QT interval (QTc interval) measured by standard electrocardiography and heart rate variability (HRV) in patients with type 2 diabetes mellitus (T2DM). From March 1, 2009, to December 12, 2009, 411 patients with T2DM who underwent resting 12-lead electrocardiography and cardiovascular autonomic function testing concurrently without the exclusion criteria were consecutively recruited in this cross-sectional study. Time- and frequency-domain HRV variables were assessed for 5 minutes by beat-to-beat HRV recording. The QT interval was corrected for the heart rate using Bazett's formula. QTc interval measurements of >440 ms were considered abnormally prolonged. The mean age and diabetes duration were 56.3 ± 10.6 years and 9.6 ± 7.3 years, respectively. A total of 90 patients had QTc interval prolongation (21.9%). The participants with a prolonged QTc interval were older (59.4 ± 10.1 years vs 55.5 ± 10.6 years, P = .002), were more likely to be a woman (72.2% vs 51.7%, P = .001), had a higher prevalence of hypertension (46.7% vs 33.4%, P = .022), had a higher hemoglobin A1c level (8.8% ± 2.2% vs 8.2% ± 1.8%, P = .045), and had decreased values for the variables measuring HRV, except for the low frequency (LF)/high frequency (HF) ratio (total power [TP], 147.7 [74.1-335.9] ms vs 328.7 [185.7-721.7] ms, P = .002). After adjusting for multiple confounders, QTc interval prolongation was associated with the lowest quartile of the HRV parameters of TP (odds ratio [OR] = 3.99; 95% confidence interval [CI]: 2.29-6.96), HF (OR = 3.20; 95% CI: 1.84-5.58), LF (OR = 3.68; 95% CI: 2.10-6.43), standard deviation of the normal-to-normal interval (OR = 3.31; 95% CI: 1.89-5.77), and root-mean-square of the successive differences (OR = 1.98; 95% CI: 1.13-3.47) in patients with T2DM. Decreased values for the variables measuring HRV, except for the LF/HF ratio, might be associated with QTc interval prolongation in patients with T2DM.

Deep neural networks reveal novel sex-specific electrocardiographic features relevant for mortality risk

Aims

Incorporation of sex in study design can lead to discoveries in medical research. Deep neural networks (DNNs) accurately predict sex based on the electrocardiogram (ECG) and we hypothesized that misclassification of sex is an important predictor for mortality. Therefore, we first developed and validated a DNN that classified sex based on the ECG and investigated the outcome. Second, we studied ECG drivers of DNN-classified sex and mortality.

Methods and results

A DNN was trained to classify sex based on 131 673 normal ECGs. The algorithm was validated on internal (68 500 ECGs) and external data sets (3303 and 4457 ECGs). The survival of sex (mis)classified groups was investigated using time-to-event analysis and sex-stratified mediation analysis of ECG features. The DNN successfully distinguished female from male ECGs {internal validation: area under the curve (AUC) 0.96 [95% confidence interval (CI): 0.96, 0.97]; external validations: AUC 0.89 (95% CI: 0.88, 0.90), 0.94 (95% CI: 0.93, 0.94)}. Sex-misclassified individuals (11%) had a 1.4 times higher mortality risk compared with correctly classified peers. The ventricular rate was the strongest mediating ECG variable (41%, 95% CI: 31%, 56%) in males, while the maximum amplitude of the ST segment was strongest in females (18%, 95% CI: 11%, 39%). Short QRS duration was associated with higher mortality risk.

Conclusion

Deep neural networks accurately classify sex based on ECGs. While the proportion of ECG-based sex misclassifications is low, it is an interesting biomarker. Investigation of the causal pathway between misclassification and mortality uncovered new ECG features that might be associated with mortality. Increased emphasis on sex as a biological variable in artificial intelligence is warranted.

The best QT correction formula in a non-hospitalized population: the Fasa PERSIAN cohort study

Background

QT interval as an indicator of ventricular repolarization is a clinically important parameter on an electrocardiogram (ECG). QT prolongation predisposes individuals to different ventricular arrhythmias and sudden cardiac death. The current study aimed to identify the best heart rate corrected QT interval for a non-hospitalized Iranian population based on cardiovascular mortality.

Methods

Using Fasa PERSIAN cohort study data, this study enrolled 7071 subjects aged 35–70 years. Corrected QT intervals (QTc) were calculated by the QT interval measured by Cardiax® software from ECGs and 6 different correction formulas (Bazett, Fridericia, Dmitrienko, Framingham, Hodges, and Rautaharju). Mortality status was checked using an annual telephone-based follow-up and a minimum 3-year follow-up for each participant. Bland–Altman, QTc/RR regression, sensitivity analysis, and Cox regression were performed in IBM SPSS Statistics v23 to find the best QT. Also, for calculating the upper and lower limits of normal of different QT correction formulas, 3952 healthy subjects were selected.

Results

In this study, 56.4% of participants were female, and the mean age was 48.60 ± 9.35 years. Age, heart rate in females, and QT interval in males were significantly higher. The smallest slopes of QTc/RR analysis were related to Fridericia in males and Rautaharju followed by Fridericia in females. Thus, Fridericia’s formula was identified as the best mathematical formula and Bazett’s as the worst in males. In the sensitivity analysis, however, Bazett’s formula had the highest sensitivity (23.07%) among all others in cardiac mortality. Also, in the Cox regression analysis, Bazett’s formula was better than Fridericia’s and was identified as the best significant cardiac mortality predictor (Hazard ratio: 4.31, 95% CI 1.73–10.74, p value = 0.002).

Conclusion

Fridericia was the best correction formula based on mathematical methods. Bazett’s formula despite its poorest performance in mathematical methods, was the best one for cardiac mortality prediction. Practically, it is suggested that physicians use QTcB for a better evaluation of cardiac mortality risk. However, in population-based studies, QTcFri might be the one to be used by researchers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02502-2.

Corrected QT Interval Is Associated With Stroke but Not Coronary Heart Disease: Insights From a General Chinese Population

Background: Prolonged heart rate-corrected QT (QTc) interval has been associated with incident cardiovascular diseases (CVD) in general Western populations. However, this association is unclear in Asian population. We aim to estimate the association between QTc interval and incident CVD in a general Chinese population.

Methods: We analyzed 8,867 participants age ≥35 years and free of CVD at baseline in the Northeast China Rural Cardiovascular Health Study. A resting 12-lead electrocardiogram was performed on all participants, and QTc interval computed using the Framingham formula. Cox proportional hazards models were used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) for associations between QTc interval and incident stroke, coronary heart disease, and combined CVD events.

Results: Over a median follow-up of 4.66 years, a total of 439 CVD events occurred (298 stroke cases and 152 CHD cases). After full adjustment, prolonged QTc defined by a sex-specific cutoff was associated with increased risk of developing stroke (HR: 1.82, 95% CI 1.20–2.75, P = 0.004) and combined CVD (HR: 1.52, 95% CI 1.05–2.19, P = 0.026). Spline analyses demonstrated no clear thresholds; when modeled as a linear relationship, each 10 ms increase of QTc interval was associated with an HR of 1.12 (95% CI 1.06–1.19, P < 0.001) for stroke and an HR of 1.10 (95% CI 1.05–1.15, P < 0.001) for combined CVD. Baseline QTc interval was not associated with incident CHD with either modeling strategy.

Conclusions: Baseline QTc interval is associated with incident stroke and CVD in adults without prior CVD from a general Chinese population.

Combined corrected QT interval and growth differentiation factor-15 level has synergistic predictive value for long-term outcome of angiographically confirmed coronary artery disease

BACKGROUND

The corrected QT interval (QTc) predicts prognosis for the general population and patients with coronary artery disease (CAD). Growth differentiation factor-15 (GDF-15) is a biomarker of myocardial fibrosis and left ventricular (LV) remodelling. The interaction between these two parameters is unknown.

SUBJECTS AND METHODS

This study included 487 patients with angiographically confirmed CAD. QTc was calculated using the Bazett formula. Multiple biochemistries and GDF-15 levels were measured. The primary endpoint was total mortality, and the secondary endpoints comprised the combination of total mortality, myocardial infarction and hospitalisation for heart failure and stroke.

RESULTS

The mean follow-up period was 1029 ± 343 days (5-1692 days), during which 21 patients died and 47 had secondary endpoints. ROC curve analysis for the optimal cut-off value of primary endpoint is 1.12 ng/mL for GDF-15 (AUC = 0.787, P = 9.0 × 10^-6 ) and 438.5 msec for QTc (AUC = 0.698, P = .002). Utilising linear regression, QTc has a positive correlation with Log-GDF-15 (r = .216, P = 1.0 × 10^-6 ). Utilising Kaplan-Meier analysis, both QTc interval and GDF-15 level are significant predictors for primary end point (P = .000194, P = 2.0 × 10^-6 , respectively) and secondary endpoint (P = .00028, P = 6.15 × 10^-8 , respectively). When combined these two parameters together, a significant synergistic predictive power was noted for primary and secondary endpoint (P = 2.31 × 10^-7 , P = 1.26 × 10^-8 , respectively). This combined strategy also showed significant correlation with the severity of CAD (P < .001).

CONCLUSION

In Chinese patient with angiographically confirmed CAD, a combined strategy utilising an ECG parameter (QTc) and a circulating biomarker (GDF-15) has good correlation with the severity of CAD, and improves the predictive power for total mortality.

Assessing Prescriber Behavior with a Clinical Decision Support Tool to Prevent Drug-Induced Long QT Syndrome

OBJECTIVE

Clinical decision support (CDS) alerts built into the electronic health record (EHR) have the potential to reduce the risk of drug-induced long QT syndrome (diLQTS) in susceptible patients. However, the degree to which providers incorporate this information into prescription behavior and the impact on patient outcomes is often unknown.

METHODS

We examined provider response data over a period from October 8, 2016 until November 8, 2018 for a CDS alert deployed within the EHR from a 13-hospital integrated health care system that fires when a patient with a QTc ≥ 500 ms within the past 14 days is prescribed a known QT-prolonging medication. We used multivariate generalized estimating equations to analyze the impact of therapeutic alternatives, relative risk of diLQTS for specific medications, and patient characteristics on provider response to the CDS and overall patient mortality.

RESULTS

The CDS alert fired 15,002 times for 7,510 patients for which the most common response (51.0%) was to override the alert and order the culprit medication. In multivariate models, we found that patient age, relative risk of diLQTS, and presence of alternative agents were significant predictors of adherence to the CDS alerts and that nonadherence itself was a predictor of mortality. Risk of diLQTS and presence of an alternative agent are major factors in provider adherence to a CDS to prevent diLQTS; however, provider nonadherence was associated with a decreased risk of mortality.

CONCLUSION

Surrogate endpoints, such as provider adherence, can be useful measures of CDS value but attention to hard outcomes, such as mortality, is likely needed.

Prediction of Drug-Induced Long QT Syndrome Using Machine Learning Applied to Harmonized Electronic Health Record Data

BACKGROUND

Drug-induced QT prolongation is a potentially preventable cause of morbidity and mortality, however there are no widespread clinical tools utilized to predict which individuals are at greatest risk. Machine learning (ML) algorithms may provide a method for identifying these individuals, and could be automated to directly alert providers in real time.

OBJECTIVE

This study applies ML techniques to electronic health record (EHR) data to identify an integrated risk-prediction model that can be deployed to predict risk of drug-induced QT prolongation.

METHODS

We examined harmonized data from the UCHealth EHR and identified inpatients who had received a medication known to prolong the QT interval. Using a binary outcome of the development of a QTc interval >500 ms within 24 hours of medication initiation or no ECG with a QTc interval >500 ms, we compared multiple machine learning methods by classification accuracy and performed calibration and rescaling of the final model.

RESULTS

We identified 35,639 inpatients who received a known QT-prolonging medication and an ECG performed within 24 hours of administration. Of those, 4,558 patients developed a QTc > 500 ms and 31,081 patients did not. A deep neural network with random oversampling of controls was found to provide superior classification accuracy (F1 score 0.404; AUC 0.71) for the development of a long QT interval compared with other methods. The optimal cutpoint for prediction was determined and was reasonably accurate (sensitivity 71%; specificity 73%).

CONCLUSIONS

We found that deep neural networks applied to EHR data provide reasonable prediction of which individuals are most susceptible to drug-induced QT prolongation. Future studies are needed to validate this model in novel EHRs and within the physician order entry system to assess the ability to improve patient safety.

A Practical Method for QTc Interval Measurement

Objective The various formulae used for QT correction by heart rate (HR) require the execution of operations with the aid of calculators or applications. This study aimed to evaluate the performance of a simple rule for QTc estimation, comparing the measurements obtained with those provided by the commonly used equations of Bazett, Fridericia, Framingham, and Hodges. Methods We used the database of a previous observational study, which analyzed patients prospectively with acute pulmonary edema admitted in an emergency service. One hundred four patients were included for QTc assessment, of whom 86 patients underwent two ECG: one ECG <24h and other >24h after admission. Thus, a total of 190 ECGs were analyzed by two observers that manually measured QT and HR. QTc was obtained using the known formulae and the proposed equations: QTc = QT+2 (FC-60) for HR ≤ 90 bpm and QTc=QT+2(FC-60)-10 for HR>90 bpm. Results Bland-Altman plots show good agreement between the simple rule and Hodges equation, with a mean difference of -3,4, SD of 4.96 and 95% limits of agreement from -9,9 to 3.2. There was not a good agreement between the simple method and the other formulae. Conclusion The proposed method has good agreement with the measures of QTc by the equation of Hodges in the HR range of 40 to 130bpm in acutely ill patients. Our method may be a plausible option for quick QT correction in these subjects.

Testosterone therapy in hypogonadal patients and the associated risks of cardiovascular events

Since the male secondary sex characters, libido and fertility are attributed to their major androgen hormone testosterone, the sub-optimum levels of testosterone in young adults may cause infertility and irregularities in their sexual behaviour. Such deficiency is often secondary to maladies involving testes, pituitary or hypothalamus that could be treated with an administration of exogenous testosterone. In the last few decades, the number of testosterone prescriptions has markedly increased to treat sub-optimal serum levels even though its administration in such conditions is not yet approved. On account of its associated cardiovascular hazards, the food and drug authority in the United States has issued safety alerts on testosterone replacement therapy (TRT). Owing to a great degree of conflict among their findings, the published clinical trials seem struggling in presenting a decisive opinion on the matter. Hence, the clinicians remain uncertain about the possible cardiovascular adversities while prescribing TRT in hypogonadal men. The uncertainty escalates even further while prescribing such therapy in older men with a previous history of cardiovascular ailments. In the current review, we analysed the pre-clinical and clinical studies to evaluate the physiological impact of testosterone on cardiovascular and related parameters. We have enlisted studies on the association of cardiovascular health and endogenous testosterone levels with a comprehensive analysis of epidemiological studies, clinical trials, and meta-analyses on the cardiovascular risk of TRT. The review is aimed to assist clinicians in making smart decisions regarding TRT in their patients.

Late-onset hypogonadism: Reductio ad absurdum of the cardiovascular risk-benefit of testosterone replacement therapy

BACKGROUND

Low testosterone (T) level is considered a marker of poor cardiovascular health. Ten years ago, the Testosterone in Older Men with Mobility Limitations (TOM) trial was discontinued due to a higher number of adverse events in men receiving T compared with placebo. Since then, several studies have investigated the risks of T replacement therapy (TRT) in late-onset hypogonadism (LOH).

OBJECTIVE

To review the mechanism by which TRT could damage the cardiovascular system.

MATERIALS AND METHODS

Comprehensive literature search of recent clinical and experimental studies.

RESULTS

The mechanisms of T-mediated coronary vasodilation were reviewed with emphasis on calcium-activated and ATP-sensitive potassium ion channels. We showed how T regulates endothelial nitric oxide synthase (eNOS) and phosphoinositide 3-kinase/protein kinase B/eNOS signaling pathways in vessel walls and its direct effects on cardiomyocytes via β1-adrenergic and ryanodine receptors and provided data on myocardial infarction and heart failure. Vascular smooth muscle senescence could be explained by the modulation of growth factors, matrix metalloproteinase-2, and angiotensin II by T. Furthermore, leukocyte trafficking, facilitated by changes in TNF-α, could explain some of the effects of T on atheromatous plaques. Conflicting data on prothrombotic risk linked to platelet aggregation inhibition via NO-triggered arachidonate synthesis or increased aggregability due to enhanced thromboxane A in human platelets provide evidence regarding the hypotheses on plaque maturation and rupture risk. The effects of T on cardiac electrophysiology and oxygen delivery were also reviewed.

DISCUSSION

The effects of TRT on the cardiovascular system are complex. Although molecular studies suggest a potential benefit, several clinical observations reveal neutral or occasionally detrimental effects, mostly due to confounding factors.

CONCLUSIONS

Attempts to demonstrate that TRT damages the cardiovascular system via systematic analysis of the putative mechanisms led to the contradiction of the initial hypothesis. Current evidence indicates that TRT is safe once other comorbidities are addressed.

Effectiveness of testosterone therapy in hypogonadal patients and its controversial adverse impact on the cardiovascular system

Testosterone is the major male hormone produced by testicles which are directly associated with man's appearance and secondary sexual developments. Androgen deficiency starts when the male hormonal level falls from its normal range though, in youngsters, the deficiency occurs due to disruption of the normal functioning of pituitary, hypothalamus glands, and testes. Thus, testosterone replacement therapy was already known for the treatment of androgen deficiency with lesser risks of producing cardiovascular problems. Since from previous years, the treatment threshold in the form of testosterone replacement therapy has effectively increased to that extent that it was prescribed for those conditions which it was considered as inappropriate. However, there are some research studies and clinical trials available that proposed the higher risk of inducing cardiovascular disease with the use of testosterone replacement therapy. Thus under the light of these results, the FDA has published the report of the increased risk of cardiovascular disease with the increased use of testosterone replacement therapy. Nevertheless, there is not a single trial available or designed that could evaluate the risk of cardiovascular events with the use of testosterone replacement therapy. As a result, the use of testosterone still questioned the cardiovascular safety of this replacement therapy. Thus, this literature outlines the distribution pattern of disease by investigating the data and link between serum testosterone level and the cardiovascular disease, also the prescription data of testosterone replacement therapy patients and their tendency of inducing cardiovascular disease, meta-analysis and the trials regarding testosterone replacement therapy and its connection with the risks of causing cardiovascular disease and lastly, the possible effects of testosterone replacement therapy on the cardiovascular system. This study aims to evaluate the available evidence regarding the use of testosterone replacement therapy when choosing it as a treatment plan for their patients.

Protective role of cardiac-specific overexpression of caveolin-3 in cirrhotic cardiomyopathy

Cirrhotic cardiomyopathy is a clinical syndrome in patients with liver cirrhosis characterized by blunted cardiac contractile responses to stress and/or heart rate-corrected QT (QTc) interval prolongation. Caveolin-3 (Cav-3) plays a critical role in cardiac protection and is an emerging therapeutic target for heart disease. We investigated the protective role of cardiac-specific overexpression (OE) of Cav-3 in cirrhotic cardiomyopathy. Biliary fibrosis was induced in male Cav-3 OE mice and transgene negative (TG_neg) littermates by feeding a diet containing 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC; 0.1%) for 3 wk. Liver pathology and blood chemistries were assessed, and stress echocardiography, telemetry, and isolated heart perfusion studies to assess adrenergic responsiveness were performed. Cav-3 OE mice showed a similar degree of hyperdynamic contractility, pulmonary hypertension, and QTc interval prolongation as TG_neg mice after 3 wk of DDC diet. Blunted systolic responses were shown in both DDC-fed Cav-3 OE and TG_neg hearts after in vivo isoproterenol challenge. However, QTc interval prolongation after in vivo isoproterenol challenge was significantly less in DDC-fed Cav-3 OE hearts compared with DDC-fed TG_neg hearts. In ex vivo perfused hearts, where circulatory factors are absent, isoproterenol challenge showed hearts from DDC-fed Cav-3 OE mice had better cardiac contractility and relaxation compared with DDC-fed TG_neg hearts. Although Cav-3 OE in the heart did not prevent cardiac alterations in DDC-induced biliary fibrosis, cardiac expression of Cav-3 reduced QTc interval prolongation after adrenergic stimulation in cirrhosis.NEW & NOTEWORTHY Prevalence of cirrhotic cardiomyopathy is up to 50% in cirrhotic patients, and liver transplantation is the only treatment. However, cirrhotic cardiomyopathy is associated with perioperative morbidity and mortality after liver transplantation; therefore, management of cirrhotic cardiomyopathy is crucial for successful liver transplantation. This study shows cardiac myocyte specific overexpression of caveolin-3 (Cav-3) provides better cardiac contractile responses and less corrected QT prolongation during adrenergic stress in a cirrhotic cardiomyopathy model, suggesting beneficial effects of Cav-3 expression in cirrhotic cardiomyopathy.

Testosterone replacement therapy and cardiovascular risk

Testosterone is the main male sex hormone and is essential for the maintenance of male secondary sexual characteristics and fertility. Androgen deficiency in young men owing to organic disease of the hypothalamus, pituitary gland or testes has been treated with testosterone replacement for decades without reports of increased cardiovascular events. In the past decade, the number of testosterone prescriptions issued for middle-aged or older men with either age-related or obesity-related decline in serum testosterone levels has increased exponentially even though these conditions are not approved indications for testosterone therapy. Some retrospective studies and randomized trials have suggested that testosterone replacement therapy increases the risk of cardiovascular disease, which has led the FDA to release a warning statement about the potential cardiovascular risks of testosterone replacement therapy. However, no trials of testosterone replacement therapy published to date were designed or adequately powered to assess cardiovascular events; therefore, the cardiovascular safety of this therapy remains unclear. In this Review, we provide an overview of epidemiological data on the association between serum levels of endogenous testosterone and cardiovascular disease, prescription database studies on the risk of cardiovascular disease in men receiving testosterone therapy, randomized trials and meta-analyses evaluating testosterone replacement therapy and its association with cardiovascular events and mechanistic studies on the effects of testosterone on the cardiovascular system. Our aim is to help clinicians to make informed decisions when considering testosterone replacement therapy in their patients.

A prolonged QTc-interval at the emergency department: Should we always be prepared for the worst?

INTRODUCTION

QTc-interval prolongation is associated with ventricular arrhythmias and mortality in a general population. Bazett's correction formula (QTcB) is routinely used despite its overcorrection at high heart rates. Recently, we proposed a patient-specific QT correcting algorithm (QTcA) resulting in improved rate correction and predictive value in a general population. We hypothesize risk stratification at the Emergency Department (ED) could be improved using QTcA.

METHODS AND RESULTS

A retrospective case-control study including a randomized age- and sex-matched control population was performed at a tertiary care ED. A total of 1930 patients were included in the analysis (63.0% males, age 71.5 ± 15.6 years). Patient characteristics, history, and test results at the time of the electrocardiogram were collected. QTc was dichotomized as prolonged (>450 millisecond for men, >470 millisecond for women) or severely prolonged (>500 millisecond). Implementation of QTcA would reduce the number of patients considered to have a prolonged QTc by 65.2%, for severely prolonged QTc 79.6%. Multivariate regression was performed for in-hospital mortality, cardiovascular endpoints, and hospital admission. Neither a prolonged QTcB (HR 1.04; 95% CI, 0.64-1.69) nor QTcA (HR 0.76; 95% CI, 0.42-1.38) was an independent predictor of in-hospital mortality. A severely prolonged QTcA (OR, 2.54; 95% CI, 1.04-6.23) was an independent predictor of cardiovascular events. Both a prolonged QTcA (OR, 1.52; 95% CI, 1.06-2.18) and a prolonged QTcB (OR, 1.37; 95% CI, 1.05-1.79) were associated with higher hospitalization rates.

CONCLUSIONS

QTcA reduced the number of patients considered at risk. Neither QTcB nor QTcA were predictors of in-hospital mortality. A severely prolonged QTcA was associated with cardiovascular events.

Pretransplant QT Interval: The Relationship with Severity and Etiology of Liver Disease and Prognostic Value After Liver Transplantation

BACKGROUND Prolonged QT interval is an integral part of the definition of cirrhotic cardiomyopathy. The aim of this study was to analyze the relationship between QT corrected (QTc) and the etiology and the severity of liver disease in relation to the complications of cirrhosis in candidates for orthotropic liver transplantation (OLTx). MATERIAL AND METHODS From 360 consecutive patients with end-stage liver disease (ESLD) consulted by a designated cardiologist, 160 patients underwent OLTx. The QTc was calculated according to 3 formulas in 151 ECG tracings with good quality. The severity of liver disease was assessed according to Child-Pugh classification and model for end-stage liver disease (MELD). This was a single-center study with register-based follow-up design. RESULTS Prolonged QTc over 440 ms was found in 51 subjects (33.8%), but none had prolonged QTc >500 ms. QTc corrected by Fridericia (F) formula was more suitable for patients with ESLD. We found no correlation between QTc interval and severity of liver disease. The QTc interval was higher in patients with alcoholic cirrhosis when compared to patients with viral hepatitis and ESLD of other etiologies. We observed a higher QTc interval in patients with gastroesophageal varices and encephalopathy. We did not notice any significant difference in the effect of the QTc interval on survival. CONCLUSIONS QTc interval might be associated with etiology and complication of ESLD. The prolonged QT interval is not associated with higher all-cause mortality after OLTx.

Early Screening of Hypertension and Cardiac Dysautonomia in Each Hypertensive is Needed-inference from a Study of QTc Interval in Gujarat, India

Background

Hypertension (HTN) is linked to cardiac dysautonomia that can end up as life-threatening arrhythmias. The same can be screened by simple electrocardiogram (ECG)-based QTc (QT corrected for heart rate) interval which indicates repolarization abnormality. We quantified QTc interval among treated hypertensives in comparison to controls, testing effect of age, gender, and blood pressure.

Methods

We conducted a cross-sectional study was done at a tertiary care teaching hospital of Gujarat, India, on 142 hypertensives on monotherapy (60 males, 82 females) and 72 age-, sex-, and time-matched normotensives. ECG was recorded with minimum 10 complexes of Lead II. QTc was derived from average of 10 values, using Bazett's formula. QTc > 0.43 s in male and > 0.45 s in female was considered abnormal.

Results

Hypertensives (mean age 40 and duration 5 years) had significantly higher QTc value than normotensives among males (0.42 vs. 0.40, P < 0.001), females (0.44 vs. 0.41, P < 0.001), and in total (0.43 vs. 0.41, P < 0.001) with 24% prevalence of ECG-based left ventricular hypertrophy. Hypertensives had odds ratio 1.63 in males (P = 0.15), 23.71 in females (P = 0.003), and 3.83 in total (P < 0.001) for prolonged QTc. QTc values were significantly affected by increasing age amongst hypertensives but not by duration of HTN or current blood pressure.

Conclusions

Our study showed a high prevalence of prolonged QTc, both qualitatively and quantitatively, in hypertensives on monotherapy with poor pressure control, associated with female gender and age but not duration or blood pressure. This underscores high risk of repolarization abnormality induced future event, suggesting QTc screening as primary prevention.

Validation of Polygenic Scores for QT Interval in Clinical Populations

BACKGROUND

Polygenic risk scores (PGS) enable rapid estimation of genome-wide susceptibility for traits, which may be useful in clinical settings, such as prediction of QT interval. In this study, we sought to validate PGS for QT interval in 2 real-world cohorts of European ancestry (EA) and African ancestry (AA).

METHODS AND RESULTS

Two thousand nine hundred and fifteen participants of EA and 366 of AA in the MGH CAMP study (Cardiology and Metabolic Patient) were genotyped on a genome-wide array and imputed to the 1000 Genomes reference panel. An additional 820 EA and 57 AA participants in the Partners Biobank were genotyped and used for validation. PGS were created for each individual using effect estimates from association tests with QT interval obtained from prior genome-wide association studies, with variants selected based from multiple significance thresholds in the original study. In regression models, clinical variables explained ≈9% to 10% of total variation in resting QTc in EA individuals and ≈12% to 18% in AA individuals. The PGS significantly increased variation explained at most significance thresholds (P<0.001), with a trend toward increased variation explained at more stringent P value cut points in the CAMP EA cohort (P<0.05). In AA individuals, PGS provided no improvement in variation explained at any significance threshold.

CONCLUSIONS

For individuals of European descent, PGS provided a significant increase in variation in QT interval explained compared with a model with only nongenetic factors at nearly every significance level. There was no apparent benefit gained by relaxing the significance threshold from conventional genome-wide significance (P<5×10^-8).

Androgen Deprivation Therapy Is Associated With Prolongation of QTc Interval in Men With Prostate Cancer

CONTEXT

Androgen deprivation therapy (ADT) for prostate cancer (PCa) is associated with increased cardiovascular mortality and sudden cardiac death, with some events occurring early after initiation of ADT. Testosterone levels are inversely associated with corrected QT (QTc) interval duration; therefore, prolongation of QTc duration could be responsible for some of these events during ADT.

OBJECTIVE

To evaluate changes in QTc duration during ADT.

DESIGN AND INTERVENTIONS

A 6-month prospective cohort study that enrolled men with PCa about to undergo ADT (ADT group) and a control group of men who previously underwent prostatectomy for PCa and never received ADT (non-ADT group).

PATIENTS

At study entry, all participants were eugonadal and had no history of cardiac arrhythmias or complete bundle branch block.

OUTCOMES

Difference in change in QTc duration from baseline on a 12-lead electrocardiogram at 6, 12, and 24 weeks after initiation of ADT compared with electrocardiograms performed at the same intervals in the non-ADT group. PR, QRS, and QT interval durations were also evaluated.

RESULTS

Seventy-one participants formed the analytical sample (33 ADT and 38 non-ADT). ADT was associated with prolongation of the QTc by 7.4 ms compared with the non-ADT group [95% confidence interval (CI) 0.08 to 14.7 ms; P = 0.048]. ADT was also associated with shortening of the QRS interval by 2.4 ms (95% CI -4.64 to -0.23; P = 0.031). Electrolytes did not change.

CONCLUSIONS

Men undergoing ADT for PCa experienced prolongation of the QTc. These findings might explain the increased risk of sudden cardiac death seen in these patients.

Trials of testosterone replacement reporting cardiovascular adverse events

The numbers of testosterone prescriptions written have increased several-fold worldwide, but the incidence of pathological hypogonadism due to hypothalamic, pituitary, and testicular disease has remained unchanged. Most of these prescriptions are being dispensed to middle-aged and older men who have experienced age-related decline in serum testosterone levels; a subset of the population in which benefits of testosterone replacement is at best, modest. Recently, some randomized controlled trials have reported increased cardiovascular events in men (mainly older men and those with prevalent cardiovascular disease) with testosterone use, and a few recent meta-analyses have confirmed these findings. In this review, we discuss trials of testosterone therapy that have reported higher cardiovascular events, relevant trials that have not reported increased cardiovascular events and large trials that have focused on cardiovascular risk (mainly atherosclerosis progression) as their main outcome. We also review findings from meta-analyses that have evaluated cardiovascular events in various testosterone trials. Finally, we discuss some potential mechanisms by which testosterone use might result in an increased cardiovascular risk. As none of the trials conducted to date were adequately powered to evaluate cardiovascular events, no firm conclusions can be drawn regarding the cardiovascular safety of testosterone therapy at this time. In the interim, we hope that this review will help practitioners make informed decisions regarding the care of their patients.

Recent heart rate history affects QT interval duration in atrial fibrillation

QT interval prolongation is associated with a risk of polymorphic ventricular tachycardia. QT interval shortens with increasing heart rate and correction for this effect is necessary for meaningful QT interval assessment. We aim to improve current methods of correcting the QT interval during atrial fibrillation (AF). Digitized Holter recordings were analyzed from patients with AF. Models of QT interval dependence on RR intervals were tested by sorting the beats into 20 bins based on corrected RR interval and assessing ST-T variability within the bins. Signal-averaging within bins was performed to determine QT/RR dependence. Data from 30 patients (29 men, 69.3±7.3 years) were evaluated. QT behavior in AF is well described by a linear function (slope ~0.19) of steady-state corrected RR interval. Corrected RR is calculated as a combination of an exponential weight function with time-constant of 2 minutes and a smaller “immediate response” component (weight ~ 0.18). This model performs significantly (p<0.0001) better than models based on instantaneous RR interval only including Bazett and Fridericia. It also outperforms models based on shorter time-constants and other previously proposed models. This model may improve detection of repolarization delay in AF. QT response to heart rate changes in AF is similar to previously published QT dynamics during atrial pacing and in sinus rhythm.

Twelve-lead electrocardiogram and mortality in young adults after ischaemic stroke

Introduction

Ischaemic stroke at young age carries an increased risk for mortality in comparison to the general population, but factors associated with mortality have been poorly studied. We studied the role of electrocardiogram in mortality risk stratification in young stroke patients.

Patients and methods

The Helsinki Young Stroke Registry encompasses 1008 patients aged <50 years with ischaemic stroke. We included 690 patients for this electrocardiogram substudy. Our endpoints were all-cause and cardiovascular mortality. Cox regression models - adjusted for clinical and demographic characteristics - were used to identify the electrocardiogram parameters associated with these endpoints.

Results

At a mean follow-up of 8.8 years, cumulative all-cause and cardiovascular mortality were 16.1 and 9.1%, respectively. Factors associated with both endpoints included diabetes (type 1 for all-cause, type 2 for cardiovascular mortality), heavy drinking, malignancy, as well as stroke severity and aetiology. Of the electrocardiogram parameters, higher heart rate (hazard ratio 1.35 per 10/min, 95% confidence interval 1.21-1.49), a shorter P-wave (hazard ratio 0.78 per 10 ms decrement, 0.64-0.92) and longer QTc interval (1.09 per 10 ms, 1.03-1.16) were associated with increased all-cause mortality. Only a higher heart rate (1.42 per 10/min, 1.24-1.60) was associated with death from cardiovascular causes.

Conclusions

A higher heart rate during the subacute phase after stroke is associated with an elevated risk of all-cause and cardiovascular mortality in young adults. A longer QTc interval is associated only with higher all-cause mortality. P-wave characteristics and their possible association with mortality need further studies.

QTc interval in young Gujarati hypertensives: Effect of disease, antihypertensive monotherapy, and coexisting risk factors

OBJECTIVES

To study the effect of disease duration, treatment and risk factors on QTc interval among young hypertensives.

MATERIALS AND METHODS

A case-control study was conducted on 142 hypertensives (60 males, 82 females) taking calcium channel blocker (CCB) or angiotensin-converting enzyme inhibitor (ACEI) as monotherapy. After blood pressure measurement, we recorded lead II electrocardiograph with minimum ten waveforms. QTc was derived from average of ten values using Bazett's formula. QTc interval >0.43 s in male and >0.45 s in female was considered abnormal.

RESULTS

Cases had mean duration of hypertension 5 years, mean age of 40 years, and poor blood pressure control (systolic blood pressure >140 and diastolic blood pressure >90 mm of Hg). Newly diagnosed hypertensives had significantly higher QTc values than the matched known cases (0.44 vs. 0.42 s, P < 0.05). Known hypertensives did not differ significantly in QTc values by the duration of disease. CCB users showed small, insignificant disadvantage for abnormally prolonged QTc values than ACEI users. With coexisting diabetes, smoking, and positive family history of hypertension, there was odds risk of 7.69, 2.75, and 2.54, respectively for prolonged QTc.

CONCLUSION

Our study showed prolonged QTc in hypertensives more so in newly diagnosed, unaffected by duration or use of ACEI, or CCB but associated with modifiable risk factors. This underscores high risk of repolarization abnormality-induced future events, suggesting early screening of hypertension, strict blood pressure control, optimum use of QTc measurement, and preventive pharmacotherapy to reduce this aftermath.

First-generation antipsychotics and QTc: any role for mediating variables?

OBJECTIVE

Corrected QT (QTc) interval prolongation is often associated with use of first-generation antipsychotics (FGAs). However, other factors require appropriate consideration, including age and gender, the role of other known medications associated with QTc prolongation, and severe comorbid conditions, such as co-occurring alcohol abuse/dependence. We aimed to study potential mediating roles of different, related, candidate variables on QTc.

METHODS

We capitalized on data from a large (N = 2366), cross-sectional, national survey, the STAR Network QTc study, using a representative sample of people taking FGAs, and recruited from mental health services across Italy.

RESULTS

About one-third of the sample was treated with FGAs, and almost one-tenth of the subjects took a different, additional, drug known to cause QTc prolongation. Our findings confirmed that there is an impact from FGAs, age, gender, alcohol misuse, and concurrent risky drugs on QTc. However, comorbid alcohol abuse/dependence and concurrent risky drugs did not mediate the effect of FGAs on QTc.

CONCLUSIONS

Our findings showed that FGAs, concurrent risky drugs, and alcohol use disorders prolonged QTc. FGAs had a direct effect on QTc, confirming the need for clinicians to monitor a risk that could lead to sudden unexplained death. Copyright © 2016 John Wiley & Sons, Ltd.

Which QT Correction Formulae to Use for QT Monitoring?

Background

Drug safety precautions recommend monitoring of the corrected QT interval. To determine which QT correction formula to use in an automated QT‐monitoring algorithm in our electronic medical record, we studied rate correction performance of different QT correction formulae and their impact on risk assessment for mortality.

Methods and Results

All electrocardiograms (ECGs) in patients >18 years with sinus rhythm, normal QRS duration and rate <90 beats per minute (bpm) in the University Hospitals of Leuven (Leuven, Belgium) during a 2‐month period were included. QT correction was performed with Bazett, Fridericia, Framingham, Hodges, and Rautaharju formulae. In total, 6609 patients were included (age, 59.8±16.2 years; 53.6% male and heart rate 68.8±10.6 bpm). Optimal rate correction was observed using Fridericia and Framingham; Bazett performed worst. A healthy subset showed 99% upper limits of normal for Bazett above current clinical standards: men 472 ms (95% CI, 464–478 ms) and women 482 ms (95% CI 474–490 ms). Multivariate Cox regression, including age, heart rate, and prolonged QTc, identified Framingham (hazard ratio [HR], 7.31; 95% CI, 4.10–13.05) and Fridericia (HR, 5.95; 95% CI, 3.34–10.60) as significantly better predictors of 30‐day all‐cause mortality than Bazett (HR, 4.49; 95% CI, 2.31–8.74). In a point‐prevalence study with haloperidol, the number of patients classified to be at risk for possibly harmful QT prolongation could be reduced by 50% using optimal QT rate correction.

Conclusions

Fridericia and Framingham correction formulae showed the best rate correction and significantly improved prediction of 30‐day and 1‐year mortality. With current clinical standards, Bazett overestimated the number of patients with potential dangerous QTc prolongation, which could lead to unnecessary safety measurements as withholding the patient of first‐choice medication.

Longitudinal Community-Based Study of QT Interval and Mortality in Southeast Asians

Introduction

The prognostic impact of QT interval prolongation has not been well studied in healthy Asians. We investigated the association between the QT interval with mortality and cardiovascular events in a healthy Southeast Asian population.

Methods

The QT interval corrected for heart rate using the Bazett’s formula (QTc) was measured in 2536 (825 men, mean age 65.7±7.5 years) Singaporean adults free of cardiovascular disease in the population-based Singapore Longitudinal Ageing Study. Outcomes were all-cause mortality and incident cardiovascular events (cardiovascular mortality, myocardial infarction (MI) and/or stroke).

Results

Over a mean 7.78 years (19695 person-years) of follow-up, there were 202 deaths (45 from cardiovascular causes), 62 cases of myocardial infarction and 64 cases of stroke. Adjusting for age, sex, and cardiovascular risk factors, QTcB prolongation remained independently associated with increased all-cause mortality (HR(per standard deviation) 1.27 (1.10–1.48), p = 0.0015), as well as increased risk of cardiovascular events (HR 1.20 (1.01–1.43), p = 0.0415) and MI/stroke (HR 1.22 (1.01–1.47), p = 0.0455), but not cardiovascular mortality alone (HR 1.05 (0.77–1.44), p = 0.7562).

Conclusions

We provide the first community-based estimates of the independent association of QT prolongation with all-cause mortality and cardiovascular events in Southeast Asians.

Association of Age, Sex, Body Size and Ethnicity with Electrocardiographic Values in Community-based Older Asian Adults

BACKGROUND

Existing electrocardiographic (ECG) reference values were derived in middle-aged Caucasian adults. We aimed to assess the association of age, sex, body size and ethnicity on ECG parameters in a multi-ethnic Asian population.

METHODS

Resting 12-lead ECG and anthropometric measurements were performed in a community-based cohort of 3777 older Asians (age 64.7±9.1 years, 1467 men, 88.8% Chinese, 7.7% Malay, 3.5% Indian, body mass index [BMI] 24.0±3.9kg/m(2)).

RESULTS

Men had longer PR interval, wider QRS, shorter QTc interval and taller SV3. In both sexes, older age was associated with longer PR interval, wider QRS, larger R aVL and more leftward QRS axis, while higher BMI was associated with longer PR interval, wider QRS, larger RaVL and more negative QRS axis. There were significant inter-ethnic differences in QRS duration among men, as well as in PR and QTc intervals among women (all adjusted p<0.05). Findings were similar in a healthy subset of 1158 adults (age 61.2±9.1 years, 365 men) without cardiovascular risk factors.

CONCLUSIONS

These first community-based ECG data in multi-ethnic older Asians highlight the independent effects of age, sex, body size and ethnicity on ECG parameters.

Optimal QT interval correction formula in sinus tachycardia for identifying cardiovascular and mortality risk: Findings from the Penn Atrial Fibrillation Free study

BACKGROUND

The QT interval measures cardiac repolarization, and prolongation is associated with adverse cardiovascular outcomes and death. The exponential Bazett correction formula overestimates the QT interval during tachycardia.

OBJECTIVE

We evaluated 4 formulas of QT interval correction in individuals with sinus tachycardia for the identification of coronary artery disease, heart failure, and mortality.

METHODS

The Penn Atrial Fibrillation Free study is a large cohort study of patients without atrial fibrillation. The present study examined 6723 Penn Atrial Fibrillation Free study patients without a history of heart failure and with baseline sinus rate ≥100 beats/min. Medical records were queried for index clinical parameters, incident cardiovascular events, and all-cause mortality. The QT interval was corrected by using Bazett (QT/RR(0.5)), Fridericia (QT/RR(0.33)), Framingham [QT + 0.154 * (1000 - RR)], and Hodges (QT + 105 * (1/RR - 1)) formulas.

RESULTS

In 6723 patients with a median follow-up of 4.5 years (interquartile range 1.9-6.4 years), the annualized cardiovascular event rate was 2.3% and the annualized mortality rate was 2.2%. QT prolongation was diagnosed in 39% of the cohort using the Bazett formula, 6.2% using the Fridericia formula, 3.7% using the Framingham formula, and 8.7% using the Hodges formula. Only the Hodges formula was an independent risk marker for death across the range of QT values (highest tertile: hazard ratio 1.26; 95% confidence interval 1.03-1.55).

CONCLUSION

Although all correction formulas demonstrated an association between QTc values and cardiovascular events, only the Hodges formula identified one-third of individuals with tachycardia that are at higher risk of all-cause mortality. Furthermore, the Bazett correction formula overestimates the number of patients with a prolonged QT interval and was not associated with mortality. Future work may validate these findings and result in changes to automated algorithms for QT interval assessment.

QT interval prolongation associated with low magnesium in chronic alcoholics

BACKGROUND

Alcoholism is a psychoactive drug-dependence with high prevalence throughout the world. Alcoholism has already been shown to be associated with electrical heart disorders, such as QT interval prolongation. Long QT, rare among healthy individuals (0.0017-0.31%), can trigger tachyarrhythmias and sudden death and might be caused by alcohol consumption itself and the resulting hypomagnesaemia.

METHODS

This case-control study assessed active alcoholics and alcoholics who have been abstinent for at least seven days to compare changes in electrocardiographic, clinical and laboratory analyses among groups.

RESULTS

A total of 166 alcoholics were evaluated, of which 62 were active and 104 abstinent alcoholics. Long QT was more prevalent among active alcoholics compared to abstinent alcoholics (16% vs. 2%, respectively, odds ratio (OR) 9.81, p=0.011), as was hypomagnesaemia (23% vs. 10%, OR 3.11, p=0.013). Serum magnesium levels were inversely proportional to the length of the corrected QT interval among active alcoholics (β=-35.1ms, p=0.005).

CONCLUSIONS

Active chronic alcoholics exhibited a higher association of long QT and hypomagnesaemia. Low serum magnesium levels were predictive of QT interval prolongation. Because the above changes potentially trigger fatal arrhythmias, it is of fundamental importance to consider the diagnostic possibility by routinely requesting electrocardiograms and serum magnesium level assessment during the treatment of chronic alcoholic patients.

Haloperidol inhibits the development of atherosclerotic lesions in LDL receptor knockout mice

BACKGROUND AND PURPOSE

Antipsychotic drugs have been shown to modulate the expression of ATP-binding cassette transporter A1 (ABCA1), a key factor in the anti-atherogenic reverse cholesterol transport process, in vitro. Here we evaluated the potential of the typical antipsychotic drug haloperidol to modulate the cholesterol efflux function of macrophages in vitro and their susceptibility to atherosclerosis in vivo.

EXPERIMENTAL APPROACH

Thioglycollate-elicited peritoneal macrophages were used for in vitro studies. Hyperlipidaemic low-density lipoprotein (LDL) receptor knockout mice were implanted with a haloperidol-containing pellet and subsequently fed a Western-type diet for 5 weeks to induce the development of atherosclerotic lesions in vivo.

KEY RESULTS

Haloperidol induced a 54% decrease in the mRNA expression of ABCA1 in peritoneal macrophages. This coincided with a 30% decrease in the capacity of macrophages to efflux cholesterol to apolipoprotein A1. Haloperidol treatment stimulated the expression of ABCA1 (+51%) and other genes involved in reverse cholesterol transport, that is, CYP7A1 (+98%) in livers of LDL receptor knockout mice. No change in splenic ABCA1 expression was noted. However, the average size of the atherosclerotic size was significantly smaller (-31%) in the context of a mildly more atherogenic metabolic phenotype upon haloperidol treatment. More importantly, haloperidol markedly lowered MCP-1 expression (-70%) and secretion (-28%) by peritoneal macrophages.

CONCLUSIONS AND IMPLICATIONS

Haloperidol treatment lowered the susceptibility of hyperlipidaemic LDL receptor knockout mice to develop atherosclerotic lesions. Our findings suggest that the beneficial effect of haloperidol on atherosclerosis susceptibility can be attributed to its ability to inhibit macrophage chemotaxis.

The QT interval is associated with incident cardiovascular events: the MESA study

BACKGROUND

Prolonged heart rate-corrected QT interval on electrocardiograms (ECGs) is associated with increased risk of myocardial infarction and cardiovascular disease (CVD)-related deaths in patients with prevalent coronary heart disease.

OBJECTIVES

This study sought to examine the prognostic association between the baseline QT interval and incident cardiovascular events in individuals without prior known CVD.

METHODS

The corrected baseline 12-lead ECG QT interval duration (QTcorr) was determined by adjustment for age, sex, race/ethnicity, and RR interval duration in 6,273 participants in MESA (Multi-Ethnic Study of Atherosclerosis). Cox proportional hazards models adjusting for demographic and clinical risk factors were used to examine the association of baseline QTcorr with incident cardiovascular events.

RESULTS

The mean age at enrollment was 61.7 ± 10 years, and 53.4% of participants were women. Cardiovascular events occurred in 291 participants over a mean follow-up of 8.0 ± 1.7 years. Each 10-ms increase in the baseline QTcorr was associated with incident heart failure (hazard ratio [HR]: 1.25; 95% CI: 1.14 to 1.37), CVD events (HR: 1.12; 95% CI: 1.05 to 1.20), and stroke (HR: 1.19; 95% CI: 1.07 to 1.32) after adjustment for CVD risk factors and potential confounders. There was no evidence of interaction with sex or ethnicity.

CONCLUSIONS

The QT interval was associated with incident cardiovascular events in middle-aged and older adults without prior CVD.

Aging effects on QT interval: Implications for cardiac safety of antipsychotic drugs

Objectives

To explore the effect of aging on cardiac toxicity specifically the interaction of age and antipsychotic drugs to alter the QT interval.

Methods

The Medline databases were searched using the OvidSP platforms with the search strategy: “QT interval” or “QT” and “age” or “aging”. The entry criteria were: over 10,000 apparently healthy individuals with data on both sexes; QT interval corrected for heart rate (QTc) and an expression of its variance for multiple age decades extending into the older ages.

Results

QTc increased in duration with increasing age. Considering a modest one SD increment in QTc in the normal population, the addition of Chlorpromazine produced a QTc on average greater than 450 ms for ages 70 years and older. Risperidone, that did not on average alter QTc, would be expected to produce a QTc of 450 ms in persons in their mid 70 years under some circumstances. QTc prolongation > 500 ms with antipsychotic drugs is more likely for persons with QTc initially at the 99^th percentile. It may occur with Haloperidol which does not on average alter QTc.

Conclusions

The range of values for the QT interval in apparently normal older men or women, when combined with the range of expected QT interval changes induced by antipsychotic drugs, can readily be associated with prolonged QTc. Individuals with QTc at the 99^th percentile may have serious QTc prolongation with antipsychotic drugs even those that are not usually associated with QTc prolongation.

Risk prediction of cardiovascular death based on the QTc interval: evaluating age and gender differences in a large primary care population

Aims

Using a large, contemporary primary care population we aimed to provide absolute long-term risks of cardiovascular death (CVD) based on the QTc interval and to test whether the QTc interval is of value in risk prediction of CVD on an individual level.

Methods and results

Digital electrocardiograms from 173 529 primary care patients aged 50–90 years were collected during 2001–11. The Framingham formula was used for heart rate-correction of the QT interval. Data on medication, comorbidity, and outcomes were retrieved from administrative registries. During a median follow-up period of 6.1 years, 6647 persons died from cardiovascular causes. Long-term risks of CVD were estimated for subgroups defined by age, gender, cardiovascular disease, and QTc interval categories. In general, we observed an increased risk of CVD for both very short and long QTc intervals. Prolongation of the QTc interval resulted in the worst prognosis for men whereas in women, a very short QTc interval was equivalent in risk to a borderline prolonged QTc interval. The effect of the QTc interval on the absolute risk of CVD was most pronounced in the elderly and in those with cardiovascular disease whereas the effect was negligible for middle-aged women without cardiovascular disease. The most important improvement in prediction accuracy was noted for women aged 70–90 years. In this subgroup, a total of 9.5% were reclassified (7.2% more accurately vs. 2.3% more inaccurately) within clinically relevant 5-year risk groups when the QTc interval was added to a conventional risk model for CVD.

Conclusion

Important differences were observed across subgroups when the absolute long-term risk of CVD was estimated based on QTc interval duration. The accuracy of the personalized CVD prognosis can be improved when the QTc interval is introduced to a conventional risk model for CVD.

Hemodiafiltration beneficially affects QT interval duration and dispersion compared to hemodialysis

BACKGROUND/AIMS

The prolongation of the QT interval and dispersion could predict ventricular arrhythmias. It is not yet established whether there is a difference between the effects of hemodialysis and hemodiafiltration on QT interval duration and dispersion.

METHODS

Data of thirty patients was investigated while they were receiving hemodiafiltration over a period of 3 months; then the same group of patients was evaluated during treatment with conventional hemodialysis for at least another 3 months. Ionic parameters and surface electrocardiograms (ECG) were analyzed five times during each session, and 2D, M-mode echocardiography and Holter ECGs were performed to acquire additional information.

RESULTS

QT interval duration (QTmax) and dispersion (QTd) showed a significant increase during hemodialysis, but not during hemodiafiltration. QTmax was 388.66 ± 31.81 ms at the beginning of hemodialysis and increased to 400.66 ± 39.12 ms even at the 30th minute (p < 0.05). QTd was found to be 31.33 ± 10.08 ms before the commencement of hemodialysis with the largest prolongation being seen at the 240th minute (51.33 ± 14.56 ms, p < 0.05). The occurrence of ventricular premature beats was significantly higher during hemodialysis (p = 0.018). The left atrial diameter significantly decreased at the end of hemodiafiltration (at the beginning 45.1 ± 5.25 mm, at the end 40.77 ± 5.76 mm; p < 0.05).

CONCLUSION

Our results suggest a beneficial effect of hemodiafiltration on the studied electrocardiographic parameters compared to hemodialysis. The larger decrease in the left atrial diameter suggests a more efficient intracardiac volume-decreasing potential of hemodiafiltration.

Effect of risperidone metabolism and P-glycoprotein gene polymorphism on QT interval in patients with schizophrenia

Risperidone (RIS) is a frequently used efficacious psychotropic drug. However, it prolongs the QTc interval and may cause fatal arrhythmia. Little is known on the determinants of this RIS side effect. RIS is metabolized by CYP2D6, and is subject to drug efflux by P-glycoprotein (P-gp) encoded by the ATP-binding cassette subfamily B member 1 (ABCB1) gene. P-gp removes both RIS and its metabolite 9-OH-RIS from cardiac tissue. To investigate the effect of RIS metabolism and ABCB1 gene polymorphisms on QTc, steady-state plasma RIS and 9-OH-RIS levels, and QTc were measured. CYP2D6, ABCB1 C3435T and G2677T/A genotypes were determined in 66 schizophrenia patients on RIS. QTc was significantly longer in patients with ABCB1 3435CT+3435 TT than in those with 3435CC (P=0.006). ABCB1 G2677T/A genotype did not affect QTc. Multiple regression analysis showed that C/T or T/T genotypes at the ABCB1 C3435T locus, lower weight, and older age prolonged QTc. In summary, the T allele of the ABCB1 C3435T genotype should be considered in future diagnostic development efforts for RIS-associated QT.

Interictal 12-lead electrocardiography in patients with epilepsy

Interictal electrocardiographic predictors of sudden unexpected death in epilepsy (SUDEP) are unknown. This study was designed to identify the unique features of the interictal 12-lead electrocardiogram (EKG) in patients with epileptic seizures. We conducted a retrospective chart review of adult patients below the age of 65 admitted to our epilepsy monitoring unit. Using EEG telemetry data, we classified patients as having nonepileptic seizures (NESs), probable epilepsy (PE), or definite epilepsy (DE) and analyzed 12-lead EKGs obtained on admission. Patients with NESs were assigned as the control group. We included patients taking antipsychotic and/or antidepressant medications but excluded patients with medical conditions or taking other medications that would otherwise confound EKG measurements. Out of the 1007 charts reviewed, 195 patients were included in our analysis, and extensive subgroup analyses were performed. We found that patients with definite localization-related epilepsy displayed a significantly longer average PR interval (162.1 ms) than patients with NESs (148.8 ms). This effect was pronounced in female patients and did not vary with the number of antiepileptic drugs (AEDs) prescribed. In contrast to previous studies, mean QTc intervals were not significantly different between DE (428 ms) and NESs (422.6 ms). However, within females, this difference reached statistical significance (DE: 434.6 ms, NESs: 424.6 ms). Antiepileptic drug polytherapy was associated with a significantly lower QTc interval (416 ms in patients on 4-6 drugs and 436.4 ms in patients on 0-1 drugs). Levetiracetam was the most commonly used AED and was associated with the longest average PR (163 ms) and QTc (432 ms) intervals. The mean QRS axis displayed a significant leftward shift in patients with localization-related epilepsy (35.6° versus 54.3° in patients with NESs) and also in female patients with DE (42.1° versus 55.4° in female patients with NESs). No differences were observed between patients with left versus right hemisphere seizure foci. Overall, these findings may reflect cardiac structural changes and/or alterations in autonomic tone that deserve closer study. Further, longer-term prospective studies are required to understand how these electrocardiographic signatures may predict sudden unexpected death in epilepsy.

Association between high sensitivity C-reactive protein, heart rate variability and corrected QT interval in patients with chronic inflammatory arthritis

BACKGROUND

The risk of sudden cardiac death is increased in chronic inflammatory arthritis, particularly rheumatoid arthritis (RA). To evaluate the putative effect of systemic inflammation on heart rate variability (HRV) and ventricular repolarization in chronic inflammatory arthritis, we analyzed in these patients the possible relationship among HRV parameters, QT interval, and high sensitivity C-reactive protein (hsCRP).

METHODS

One hundred-one patients with chronic inflammatory arthritis underwent a 15-minute ambulatory twelve-channel electrocardiogram-recording, to evaluate HRV and QT interval, as well as a venous withdrawal for hsCRP as an estimation of ongoing systemic inflammation.

RESULTS

In patients with chronic inflammatory arthritis, hsCRP is inversely correlated with HRV and directly with QTc duration, but while hsCRP is associated with HRV independently from any other investigated factor, the association between hsCRP and QTc seems to be an indirect consequence of the autonomic dysfunction itself. Within the whole cohort of patients, those subjects having elevated hsCRP levels displayed both a significant reduction in HRV and a prolongation of QTc with respect to patients with a normal hsCRP value. A similar, although less marked, degree of HRV depression and QTc prolongation was found in RA patients when compared to subjects with spondyloarthritis (SpA) and healthy controls.

CONCLUSIONS

These data provide evidence of a link between systemic inflammation and the arrhythmic risk in patients with chronic inflammatory arthritis, also putatively explaining, at least in part, how the different inflammatory load characterizing RA and SpA parallels the different risks of cardiovascular death in these two conditions.