Association between heart rate-corrected QT interval and coronary risk factors in 2,894 healthy subjects (the DESIR Study). Data from an Epidemiological Study on the Insulin Resistance syndrome

Factors associated with prolonged QTc interval in Iranian population: MASHAD cohort study

AIM

QTc interval prolongation is a growing global issue which can cause torsades de pointes, a potentially fatal arrhythmia. We aimed to identify risk factors for prolonged QT interval in men and women.

METHODS

The Mashhad stroke and heart atherosclerotic disorder (MASHAD) cohort study collected electrocardiogram interval data. QT was corrected for heart rate using the Bazett's formula. Ordinal logistic regression with crude (univariable) and adjusted (multivariate) association analyses in the form of odds ratio and corresponding 95% confidence interval (CI) were used to identify the factors associated with QTc prolongation.

RESULTS

A total of 8878 individuals including 5318 females and 3560 males, aged 35 to 65 years, were included in this cross-sectional study. Participants with QTc prolongation were more likely to be older and have hypercholesterolemia, hypertension (HTN), and Type 2 diabetes mellitus (T2DM), but to have lower levels of physical activity (P < 0.05). Age (OR = 1.68, 95%CI = 1.18-2.39), hypercholesterolemia (OR = 1.77, 95%CI = 1.24-2.51), HTN (OR = 1.36, 95%CI = 1.06-1.73), T2DM (OR = 1.59, 95%CI = 1.19-2.13), severe anxiety (OR = 1.80, 95%CI = 1.05-3.11) and mild depression (OR = 1.38, 95%CI = 1.01-1.88) were independent risk factors for prolonged QTc interval in men. For women, only HTN (OR = 1.29, 95%CI = 1.02-1.63) and T2DM (OR = 1.50, 95%CI = 1.14-1.97) were independent risk factors.

CONCLUSIONS

Older age, Hypercholesterolemia, HTN, T2DM, severe anxiety and mild depression in men, and HTN and T2DM in women were associated with high risk of prolonged QTc interval. Healthcare practitioners should be aware of the risk factors of QTc interval prolongation and should exercise caution in the management of certain patients.

Smoking-associated Electrocardiographic Abnormalities Predict Cardiovascular Mortality: Insights from NHANES

Background—

Smoking is associated with arrhythmia and sudden cardiac death, but the biological mechanisms remain unclear. Abnormal electrocardiogram (ECG) durations of ventricular repolarization (QT interval), atrial depolarization (P wave), and atrioventricular depolarization (PR interval and segment), predict cardiac arrhythmia and mortality.

Objectives—

To elucidate how smoking affects cardiac excitation, we assessed in a nationally representative sample (NHANES III) associations between cotinine, abnormalities in P duration, PR interval, PR segment, rate-corrected QT (QTc), QRS duration, and JT interval, and long-term mortality.

Methods—

We analyzed data from 5,633 adults using survey-weighted multinomial logistic regression to estimate associations between tobacco use (>15 ng/ml serum cotinine) and short (<5th percentile) or long (>95th percentile) ECG intervals, relative to reference (5 - 95th percentile).

Results—

After adjustment for demographics, risk factors, and conduction-altering medications, smoking was associated with a higher odds of short PR interval, PR segment, and QRS, and long JT. Broader ECG effects of smoking were also assessed by survey-weighted linear regression of continuous cotinine and ECG intervals, which revealed cotinine inversely associated with PR segment and QTc. Over a 22-year follow-up, many ECG abnormalities predicted cardiovascular mortality in smokers, including long JT, QRS, and QTc, and short QRS.

Conclusions—

Smoking increases likelihood for rapid atrioventricular conduction, rapid ventricular depolarization, and slow ventricular repolarization. The ventricular electrophysiologic abnormalities associated with smoking also predict cardiovascular mortality in smokers; however, traditional ECG measures of cardiac risk like QTc can overlook these ventricular defects and their independent predictive value in smokers.

Increasing Daily Physical Activity and Its Effects on QTc Time in Severe to Very Severe COPD: A Secondary Analysis of a Randomised Controlled Trial

Approximately, half of COPD patients die from cardiovascular diseases. A prolongation of cardiac repolarization (measured as QTc interval) is associated with cardiovascular events or cardiovascular deaths in populations of older adults and COPD. One way to reduce the QTc could be to increase physical activity (PA). We investigated whether QTc can be reduced by an increase in PA in patients with severe COPD. This is a secondary outcome analysis from a randomized controlled trial investigating the effects of a 3 months pedometer based program to improve PA. 12-lead ECG was assessed at baseline and after 3 months. We measured PA using a validated triaxial accelerometer. Data were analyzed from 59 participants. Multiple regression modeling, including adjustment for baseline QTc, sex, QT prolonging medications, BMI, smoking status and FEV1%, showed no evidence for an association between an improvement of ≥15% PA and QTc reduction. A 15% improvement in PA according to step counts over 3 months seems not to reduce QTc interval by its MCID of 20 ms in patients with severe to very severe COPD.

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.

Smoking Accelerates Atrioventricular Conduction in Humans Concordant with Increased Dopamine Release

Smoking is associated with cardiac arrhythmia, stroke, heart failure, and sudden cardiac arrest, all of which may derive from increased sympathetic influence on cardiac conduction system and altered ventricular repolarization. However, knowledge of the effects of smoking on supraventricular conduction, and the role of the sympathetic nervous system in them, remains incomplete. Participants with intermediate-high cardiovascular disease risk were measured for urinary catecholamines and cotinine, and 12-lead electrocardiograms (ECGs) were measured for atrial and atrioventricular conduction times, including P duration, PR interval, and PR segment (lead II), which were analyzed for associations with cotinine by generalized linear models. Statistical mediation analyses were then used to test whether any significant associations between cotinine and atrioventricular conduction were mediated by catecholamines. ECG endpoints and urinary metabolites were included from a total of 136 participants in sinus rhythm. Atrial and atrioventricular conduction did not significantly differ between smokers (n = 53) and non-smokers (n = 83). Unadjusted and model-adjusted linear regressions revealed cotinine significantly and inversely associated with PR interval and PR segment, but not P duration. Dopamine, norepinephrine, and epinephrine all inversely associated with PR interval, whereas only dopamine was also inversely associated with PR segment (p < 0.05). Dopamine and norepinephrine (but not epinephrine) also associated positively with cotinine. Dopamine mediated the relationship between cotinine and PR interval, as well as the relationship between cotinine and PR segment. Smoking is associated with accelerated atrioventricular conduction and elevated urinary dopamine and norepinephrine. Smoking may accelerate atrioventricular nodal conduction via increased dopamine production.

Cardiovascular injury induced by tobacco products: assessment of risk factors and biomarkers of harm. A Tobacco Centers of Regulatory Science compilation

Although substantial evidence shows that smoking is positively and robustly associated with cardiovascular disease (CVD), the CVD risk associated with the use of new and emerging tobacco products, such as electronic cigarettes, hookah, and heat-not-burn products, remains unclear. This uncertainty stems from lack of knowledge on how the use of these products affects cardiovascular health. Cardiovascular injury associated with the use of new tobacco products could be evaluated by measuring changes in biomarkers of cardiovascular harm that are sensitive to the use of combustible cigarettes. Such cardiovascular injury could be indexed at several levels. Preclinical changes contributing to the pathogenesis of disease could be monitored by measuring changes in systemic inflammation and oxidative stress, organ-specific dysfunctions could be gauged by measuring endothelial function (flow-mediated dilation), platelet aggregation, and arterial stiffness, and organ-specific injury could be evaluated by measuring endothelial microparticles and platelet-leukocyte aggregates. Classical risk factors, such as blood pressure, circulating lipoproteins, and insulin resistance, provide robust estimates of risk, and subclinical disease progression could be followed by measuring coronary artery Ca2+ and carotid intima-media thickness. Given that several of these biomarkers are well-established predictors of major cardiovascular events, the association of these biomarkers with the use of new and emerging tobacco products could be indicative of both individual and population-level CVD risk associated with the use of these products. Differential effects of tobacco products (conventional vs. new and emerging products) on different indexes of cardiovascular injury could also provide insights into mechanisms by which they induce cardiovascular harm.

Prolonged QT dispersion in inflammatory bowel disease

AIM: To investigate the frequency and factors of prolonged QT dispersion that may lead to severe ventricular arrhythmias in patients with inflammatory bowel disease (IBD).

METHODS: This study included 63 ulcerative colitis (UC) and 41 Crohn’s disease (CD) patients. Forty-seven healthy patients were included as the control group. Heart rate was calculated using electrocardiography, corrected QT dispersion (QTcd) and the Bazett’s formula. Homeostasis model assessment (HOMA) was used to determine insulin resistance (IR). HOMA values < 1 were considered normal and values > 2.5 indicated a high probability of IR.

RESULTS: Prolonged QTcd was found in 12.2% of UC patients, and in 14.5% of CD patients compared with the control group (P < 0.05). A significant difference was found between the insulin values (CD: 10.95 ± 6.10 vs 6.44 ± 3.28, P < 0.05; UC: 10.88 ± 7.19 vs 7.20 ± 4.54, P < 0.05) and HOMA (CD: 2.56 ± 1.43 vs 1.42 ± 0.75, P < 0.05; UC: 2.94 ± 1.88 vs 1.90 ± 1.09, P < 0.05) in UC and CD patients with and without prolonged QTcd. Disease behavior types were determined in CD patients with prolonged QTcd. Increased systolic arterial pressure (125 ± 13.81 vs 114.09 ± 8.73, P < 0.01) and age (48.67 ± 13.93 vs 39.57 ± 11.58, P < 0.05) in UC patients were significantly associated with prolonged QTcd.

CONCLUSION: Our data show that IBD patients have prolonged QTcd in relation to controls. The routine follow-up of IBD patients should include determination of HOMA, insulin values and electrocardiogram examination.

Cigarette Smoking Is Associated with Prolongation of the QTc Interval Duration in Patients with Type 2 Diabetes Mellitus

Aims. Aim of the study was to evaluate the effect of smoking on autonomic nervous system (ANS) activity and QTc interval duration in patients with Type 2 diabetes mellitus (T2DM). Methods. A total of 70 patients with T2DM (35 chronic smokers, 35 nonsmokers) treated with oral antidiabetic medications underwent continuous ECG Holter monitoring for 24 hours and analysis of time- and frequency-domain measures of heart rate variability (HRV). HRV over short time was also assessed using the deep breathing test. In addition, baroreflex sensitivity (BRS) was evaluated using the spontaneous sequence method. The mean QTc interval was measured from the 24-hour ECG recordings. Results. Smokers had lower body mass index (BMI) and exhibited higher 24-hour mean heart rate. There was no difference regarding all measures of ANS activity between the two groups. Smokers showed increased mean QTc duration during the 24 hours (439.25 ± 26.95 versus 425.05 ± 23.03 ms, P = 0.021) as well as in both day (439.14 ± 24.31 ms, P = 0.042) and night periods (440.91 ± 32.30 versus 425.51 ± 24.98 ms, P = 0.033). The association between smoking status and mean QTc interval persisted after adjusting for BMI. Conclusions. Cigarette smoking is associated with prolongation of the QTc interval in patients with T2DM by a mechanism independent of ANS dysfunction.

Prolongation of QTc and risk of stroke: The REGARDS (REasons for Geographic and Racial Differences in Stroke) study

OBJECTIVES

The purpose of this study was to examine the association between prolongation of QT interval corrected for heart rate (QTc) with incident stroke.

BACKGROUND

Unlike cardiovascular morbidity and mortality, little is known about the relationship between QTc and risk of stroke.

METHODS

A total of 27,411 participants age 45 years and older without previous stroke from the REGARDS (REasons for Geographic and Racial Differences in Stroke) study were included in this analysis. QTc was calculated using Framingham formula (QTc(Fram)). Stroke cases were identified and adjudicated during up to 8.2 years of follow-up (median, 5.1 years).

RESULTS

The risk of incident stroke in study participants with prolonged QTc(Fram) was almost 3 times the risk in those with normal QTc(Fram) (hazard ratio [HR] [95% confidence interval (CI)]: 2.88 [2.12 to 3.92], p < 0.0001). After adjustment for demographics (age, race, and sex), traditional stroke risk factors (antihypertensive medication use, systolic blood pressure, current smoking, diabetes, left ventricular hypertrophy, atrial fibrillation, and previous cardiovascular disease), warfarin use, aspirin use, QRS duration and use of QTc-prolonging drugs, the risk of stroke remained significantly high (HR [95% CI]: 1.67 [1.16 to 2.41], p = 0.0061) and was consistent across several subgroups of REGARDS study participants. Similar results were obtained when the risk of stroke was estimated per 1-SD increase in QTc(Fram), (HR [95% CI]: 1.12 [1.03 to 1.21], p = 0.0053 in multivariable-adjusted model) and when other QTc correction formulas including those of Hodge, Bazett, and Fridericia were used.

CONCLUSIONS

QTc prolongation is associated with a significantly increased risk of incident stroke independent of traditional stroke risk factors. Examining the risk of stroke associated with QTc-prolonging drugs may be warranted.

Coffee, alcohol, smoking, physical activity and QT interval duration: results from the Third National Health and Nutrition Examination Survey

Background

Abnormalities in the electrocardiographic QT interval duration have been associated with an increased risk of ventricular arrhythmias and sudden cardiac death. However, there is substantial uncertainty about the effect of modifiable factors such as coffee intake, cigarette smoking, alcohol consumption, and physical activity on QT interval duration.

Methods

We studied 7795 men and women from the Third National Health and Nutrition Survey (NHANES III, 1988–1994). Baseline QT interval was measured from the standard 12-lead electrocardiogram. Coffee and tea intake, alcohol consumption, leisure-time physical activities over the past month, and lifetime smoking habits were determined using validated questionnaires during the home interview.

Results

In the fully adjusted model, the average differences in QT interval comparing participants drinking ≥6 cups/day to those who did not drink any were −1.2 ms (95% CI −4.4 to 2.0) for coffee, and −2.0 ms (−11.2 to 7.3) for tea, respectively. The average differences in QT interval duration comparing current to never smokers was 1.2 ms (−0.6 to 2.9) while the average difference in QT interval duration comparing participants drinking ≥7 drinks/week to non-drinkers was 1.8 ms (−0.5 to 4.0). The age, race/ethnicity, and RR-interval adjusted differences in average QT interval duration comparing men with binge drinking episodes to non-drinkers or drinkers without binge drinking were 2.8 ms (0.4 to 5.3) and 4.0 ms (1.6 to 6.4), respectively. The corresponding differences in women were 1.1 (−2.9 to 5.2) and 1.7 ms (−2.3 to 5.7). Finally, the average differences in QT interval comparing the highest vs. the lowest categories of total physical activity was −0.8 ms (−3.0 to 1.4).

Conclusion

Binge drinking was associated with longer QT interval in men but not in women. QT interval duration was not associated with other modifiable factors including coffee and tea intake, smoking, and physical activity.

Electrocardiographic abnormalities in young athletes with mitral valve prolapse

BACKGROUND

Mitral valve prolapse (MVP) is the most common primary valvular abnormality in a young population. In some individuals, MVP is silent or associated with palpitations, dizziness, chest pain, and abnormal electrocardiogram (ECG) repolarization with or without ventricular arrhythmias.

HYPOTHESIS

The aim of the present study was to assess the occurrence of the clinical and electrocardiographic abnormalities in young athletes with silent MVP.

METHODS

A group of 10 children, who have been sport training intensively, with preparticipation silent MVP were examined for symptoms and/or ECG abnormalities. The diagnosis of MVP was made by echocardiography.

RESULTS

Three athletes were asymptomatic at initial presentation. The other 7 athletes presented with symptoms. The QTc intervals > 440 msec were recorded in 2 athletes (1 with syncope). Abnormal ECG repolarization was found in 7 athletes (4 athletes were symptomatic and 3 were asymptomatic). A large variety of T-waves was registered in athletes who presented with symptoms. In asymptomatic athletes, the tall and flat T-waves were recorded.

CONCLUSIONS

Young athletes with MVP are often predisposed to electrocardiographic abnormalities of ventricular repolarization, which requires annual cardiologic evaluation.

Influence of smoking abstinence and nicotine replacement therapy on heart rate and QT time-series

SUMMARY

Many smokers attempt to quit without using nicotine replacement therapy (NRT) or pharmacotherapy, i.e. 'cold-turkey'. The cardiac implications of this are important but are incompletely understood. Previous studies have associated smoking cessation with improvements in heart rate (HR) and its variability, but its influence on QT time-series is unclear. Furthermore, the relative influence on these parameters of acute nicotine withdrawal and of NRT has not been adequately compared. Additional insight might come from analysing the dynamic (e.g. fractal) properties of electrocardiographic data during different levels of nicotine exposure. We examined the influence of smoking cessation, during cold-turkey and subsequent NRT, on HR and QT time-series during 30 days of smoking abstinence. Seven smokers and sixteen healthy non-smokers received ECG monitoring at baseline (Day 0). Smokers subsequently refrained from smoking without using NRT for 24 h, and then received NRT for 29 days. ECG monitoring was repeated at Days 1, 7, 30. Following smoking cessation we observed that: HR and rate-corrected QT were both reduced, heart rate variability (HRV) increased (improved), and QT variability index (QTVI) showed signs of improvement (trend only). Improvements in HR and QT were maintained throughout NRT use, whilst improvements in HRV and QTVI were sustained for at least the early stages of NRT. The dynamic (multifractal) properties of HR and QT were similar for smokers and non-smokers, and were unchanged by smoking abstinence or NRT. Our results provide tentative evidence that electrocardiographic improvements during a cold-turkey smoking quit attempt (acute nicotine withdrawal) are maintained during NRT pharmacotherapy.

The effect of different stressors on the QT interval and the T wave

Prolonged QT interval is associated with the generation of life-threatening arrhythmias and sudden death. However, neither the relation between QT duration and heart rate, nor the association between mental stress and QT time has been clarified. Aim: The relationship between QT duration and smoking, cardiovascular reactivity, and mental stress as well as newer methods of QT correction were studied. Methods: In six laboratory experiments 166 volunteers were studied. Smoking, treadmill exercise, mental arithmetic and videogame were applied as stressors. Besides fixed formulae, study and subject-specific QT correction methods were also used. Results: 1. Bazett formula is not appropriate to compare QT durations. 2. Acute smoking has no effect on QT time. 3. QT changes are related to cardiovascular reactivity. 4. Mental stress may induce QT prolongation. 5. Bifid T waves often develop during mental and isometric stress. Conclusions: New methods for QT correction are more reliable than preformed formulae. QT prolongation and bifid T waves may be the links between mental stress and life threatening arrhythmias.

Gender-specific effect of metabolic syndrome on rate adjusted QT interval in middle-aged participants of an atherosclerosis prevention program

INTRODUCTION

The metabolic syndrome is a matter of immense public concern for atherosclerosis prevention. Key features are visceral obesity, dyslipidemia, hyperglycemia in the non-diabetic range, and arterial hypertension. Subclinical atherosclerosis is the clinical consequence of metabolic syndrome, which may influence the QT interval. The aim was to investigate the rate corrected QT interval in subjects with metabolic syndrome in comparison to those without cardiometabolic risk factor clusters, and to explore gender differences in cardiac repolarization between the two groups.

PATIENTS, MATERIALS AND METHODS

Heart rate and QT interval were automatically measured from surface ECG in 1086 participants (767 men, 319 women) from the Salzburg-Atherosclerosis-Prevention-program-in-subjects-at-High-Individual-Risk (SAPHIR). To omit the QT adjustment bias inherent in Bazett's formula we used a QT adjustment method with linear scaling as described by Rautaharju.

RESULTS

The prevalence of metabolic syndrome was 13.8% among males and 10% among females. Mean rate adjusted QT (QTa) intervals were longer in women than in men. Presence of metabolic syndrome, however, was associated with significantly prolonged QTa only in men but not in women. Adjustment for relevant confounders reduced the difference of mean QTa in men from 9.24 to 5.83 ms (95% CI 0.9-10.8), but this difference was still statistically significant (p = 0.021). The effect of metabolic syndrome on QTa was only partly mediated by hypertension and insulin resistance. In females, however, no relevant differences were detected for QTa interval between subjects categorized by presence or absence of metabolic syndrome.

CONCLUSIONS

The findings indicate a significant association between metabolic syndrome and rate-invariant QT in middle-aged men after adjustment for other risk factors. QT measurement may provide additive diagnostic and prognostic information in populations undergoing cardiovascular risk screening. However, the effect of metabolic and hormonal factors on ventricular repolarization seems to differ between the sexes.

An evaluation of the impact of gender and age on QT dispersion in healthy subjects

OBJECTIVES

To determine if gender, age, and gender per age category, have an impact on QT and QTc dispersion in healthy volunteers.

METHODS

This study was undertaken in 150 patients (50 per age group, 75 males, 75 females). The age groups included young (20-40 years), middle-aged (41-69 years) and elderly (> 70 years) subjects. The QT intervals on a 12 lead ECG were determined and Bazett's formula was used to derive the QTc intervals. The QT and QTc dispersion were determined by subtracting the shortest QTc interval from the longest on each 12-lead recording.

RESULTS

Males had higher QT dispersion than females (50 +/- 22 vs 42 +/- 18 ms, P = 0.017) but QTc dispersion was not significantly changed. No significant differences were seen among the different age categories for QT or QTc dispersion. In elderly subjects, males had higher QT and QTc dispersion than females (54 +/- 23 vs 42 +/-15 ms, P = 0.039 and 63 +/- 23.7 vs 48 +/- 21 ms, P = 0.032, respectively).

CONCLUSIONS

When evaluating the effect of gender in different age categories, elderly males have significantly greater QT and QTc dispersion than elderly female subjects. No other gender differences were noted for QT or QTc dispersion in the other two age categories. When evaluating a population of healthy volunteers, regardless of age, gender has an impact on QT dispersion but no significant interaction with QTc dispersion. Evaluating age without dividing the data by gender yields no significant differences in QT or QTc dispersion.

Relationship between QT interval and cardiovascular risk factors in healthy young subjects

A prolongation of QT interval increases the risk for coronary heart disease, ventricular arrhythmias, and sudden death in diabetic patients, after myocardial infarction, and in the elderly. An association between QT prolongation and cardiovascular risk factors has been demonstrated in middle-aged and elderly subjects. Aims of this study were to evaluate the prevalence of a prolonged corrected QT interval (QTc) in a healthy young population (n=170, age 22-25 years, 84 males) and to investigate the association of QTc and QT dispersion (QTd) with cardiovascular risk factors (body mass index, blood pressure, fasting blood glucose and cholesterol, smoking habits, and hypertensive familiarity). A prolonged QTc was observed in 10% of female and 5% of male subjects; in multiple regression analysis, QTc showed a significant positive relationship with blood glucose in females (P=0.04) and systolic blood pressure in male subjects (P=0.03), while QTd was not significantly related with any of the factors. In conclusion, the association between QTc length, glucose levels, and blood pressure is present also in young healthy subjects. QT measurement may represent a useful marker in the screening of young subjects for cardiovascular prevention. Journal of Human Hypertension (2005) 19, 623-627. doi:10.1038/sj.jhh.1001874; published online 19 May 2005.

Relationship of QT interval duration with carotid intima media thickness in a clinically healthy population undergoing cardiovascular risk screening

OBJECTIVES

To investigate the relationship between cardiac repolarization (QT interval duration) and intima media thickness (IMT) of the carotid arteries as surrogate measures of subclinical atherosclerosis.

DESIGN

Prospective study with consecutive subjects enrolled in the SAPHIR program (Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk).

SETTING

The analysis of the material was performed at the departments of medicine and neurology of a university hospital.

SUBJECTS

The study cohort comprises a population-based sample of 1199 clinically healthy subjects (851 men and 348 women; age 39-66 years). Exclusion criteria were cardiovascular disease, diabetes, atrial fibrillation, bundle branch block and use of medication affecting QT interval duration.

MAIN OUTCOME MEASURES

IMT of common (CCA) and internal carotid arteries (ICA) was measured by B-mode ultrasound. QT interval duration was determined in the resting 12-lead electrocardiogram by an automatic analysis program. The QT intervals were corrected for heart rate with five standard equations (QTc-Bazett, -Fridericia, -Framingham, -Hodges and -Rautaharju) and tested for their relationship with carotid IMT after adjustment for clinical and metabolic variables. Results. Females had higher heart rates than males (64 +/- 10 b min(-1) vs. 60 +/- 9 b min(-1), P <0.0005), with longer mean QT (410 +/- 28 ms vs. 404 +/- 28 ms, P=0.003) and QTc intervals in all correction formulae (P <0.0005). Significant correlations between QT/QTc and ICA IMT (r=0.14-0.16) were found in males. In the general linear model the association between QTc (except for Bazett) and ICA IMT remained significant after adjusting for age, BMI and further cardiovascular risk factors. In females the crude correlations between QT/QTc and ICA IMT were lower than those with CCA IMT. Only the correlation between uncorrected QT and CCA IMT (r=0.15, P=0.006) remained significant after adjustment for covariates.

CONCLUSIONS

The results of the present study demonstrate that QT and QTc prolongation are in part associated with IMT of carotid arteries, which is an established risk marker of subclinical atherosclerosis. In men the data support the hypothesis of an association between QTc and ICA IMT. In women a statistically significant relationship was found between the uncorrected QT interval and CCA IMT. These findings suggest that differences in carotid IMT and ventricular repolarization between genders might be related to hormonal and nonhormonal effects.

Acute effects of cigarette smoking on the QT interval in healthy smokers

This study assesses the effect of a first cigarette smoked in the morning on the QT interval duration in healthy habitual smokers after not smoking overnight. This study demonstrates that although after cigarette smoking the QT(Bc) values increase, the QT(Fc) and QT(Lc) values remained unchanged, and an increased sympathetic response was evident. The discrepancies between the results seen by different QT correction formulas emphasize the importance of selecting an accurate method for heart rate correction when evaluating and interpreting alterations in QT values.

Family studies: their role in the evaluation of genetic cardiovascular risk factors

Early epidemiological studies showed that genetic factors contribute to the risk of cardiovascular disease. Genetic epidemiological studies based upon families can be used to investigate familial trait aggregation, to localize genes implicated in cardiovascular diseases in the human genome, and to establish the role of environmental factors. Family studies can be also used to identify the physiological role of candidate genes for cardiovascular diseases, and to characterize shared environmental risk factors and their impact on the expression of genetic predisposition. The present paper reviews the existing family studies with special emphasis on those which have studied healthy populations in relation to cardiovascular disease such as the Framingham Heart Study, the National Heart, Lung, and Blood Institute Family Heart Study, and the STANISLAS cohort.