Combined QT interval and voltage criteria improve left ventricular hypertrophy detection in resistant hypertension

Independent Influence of Blood Pressure on QTc Interval: Results from a General Chinese Population

Aims

We performed the current study primarily to characterize the independent association of blood pressure with heart rate-corrected QT (QTc) interval after adjusting for cardiovascular confounding factors and left ventricular mass (LVM) in a large general population in China.

Methods

All enrolled 10,553 permanent residents with age ≥ 35 years from Liaoning Province were investigated by a questionnaire and then subjected to physical examinations, laboratory analyses, and electrocardiogram (ECG) as well as echocardiogram at the same visit. Multivariate linear and logistic regression analyses were conducted to assess the independent association of blood pressure with QTc interval.

Results

Hypertensive subjects had significantly longer QTc interval and higher prevalence of prolonged QTc interval compared with normotensive ones in all subgroups stratified by gender and left ventricular hypertrophy (LVH) (all Ps ≤ 0.001). Multiple relevant clinical confounding factors and LVM were all adjusted in the multivariate linear and logistic regression analyses. As a result, both systolic blood pressure (SBP) and diastolic blood pressure (DBP) were independently associated with QTc interval (β = 0.12 and 0.16, respectively; Ps < 0.001). Furthermore, as categorical variables, hypertension was independently associated with prolonged QTc interval (OR = 1.71; P < 0.001). Sex-specific analyses revealed that the independent associations were detected in both males and females (all Ps < 0.001).

Conclusions

These key findings of the current study highlighted the fact that hypertension was significantly associated with prolonged QTc interval and the correlations were independent of confounding factors and LVM.

Consistency of left ventricular hypertrophy diagnosed by electrocardiography and echocardiography: the Northern Shanghai Study

Background

Left ventricular hypertrophy (LVH) is one of the preclinical manifestations of hypertensive target organ damage (TOD). However, it remains unclear which electrocardiographic criterion perform better in diagnosing LVH.

Purpose

To investigate the consistency of LVH diagnosed by electrocardiography (ECG) and echocardiography (ECHO). Taking LVH by ECHO as reference, to compare three different ECG criteria (Sokolow-Lyon, Cornell and Cornell Product criteria) and find the best ECG indicator for identifying LVH in community-based elderly Chinese.

Patients and methods

Echocardiography and electrocardiography were applied to define LVH in 1789 elderly Chinese aged >65 years old in communities located at the northern Shanghai. Echocardiographic LVH (ECHO-LVH) was defined by left ventricular mass indexed for Body Surface Area (LVM/BSA) or for height^2.7 (LVM/height^2.7). Electrocardiographic LVH (ECG-LVH) was defined by Sokolow-Lyon (SL), Cornell and Cornell Product (CP) criteria. ECHO-LVH was defined by LVM/BSA≥125 g/m² in male or ≥110 g/m² in female (LVH1); LVM/BSA≥115 g/m² in male, or ≥95 g/m² in female (LVH2) and LVM/height^2.7 ≥51 g/m^2.7 in male or ≥47 g/m^2.7 in female (LVH3).

Results

As compared with SL and Cornell criteria, CP had the greatest correlation coefficient in the association with echocardiography-defined LVH, except for LVM/BSA in men. Of note, CP criterion had the greatest area under curve of ROC than Cornell criterion and the SL index, not only in total population but also in subgroups classified by blood pressure.

Conclusion

In ECG-LVH criteria, CP criterion complies better than SL index and Cornell criterion in assessing cardiac hypertrophy.

Interrelationship between electrocardiographic left ventricular hypertrophy, QT prolongation, and ischaemic stroke: the REasons for Geographic and Racial Differences in Stroke Study

AIMS

To determine if the association between electrocardiographic left ventricular hypertrophy (ECG-LVH) and ischaemic stroke is partially explained by the concomitant presence of QT prolongation.

METHODS AND RESULTS

A total of 24 948 (mean age = 65 ± 9.4 years; 40% black; 55% women) participants from the REasons for Geographic And Racial Differences in Stroke (REGARDS) study were included in this analysis. Electrocardiographic left ventricular hypertrophy was defined by the Sokolow-Lyon criteria. Heart rate-adjusted QT (QTa) was computed using a linear regression model. Adjudicated ischaemic stroke events were the outcome of interest. Cox regression was used to compute hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between ECG-LVH and prolonged QTa, in isolation and combined, with ischaemic stroke. There were 2422 (9.7%) participants with ECG-LVH, 820 (3.3%) with prolonged QTa, and 161 (0.6%) with both. Over a median follow-up of 7.6 years, 714 (2.9%) ischaemic stroke events occurred. After adjustment for stroke risk factors and potential confounders, an increased risk of ischaemic stroke was observed among participants with ECG-LVH and prolonged QTa (HR = 1.85, 95% CI = 1.04-3.30), isolated ECG-LVH (HR = 1.40, 95% CI = 1.13-1.75), and isolated prolonged QTa (HR = 1.45, 95% CI = 1.04-2.03) compared with participants without either condition. When ECG-LVH and prolonged QTa were examined as separate variables, the risk of ischaemic stroke for each condition remained statistically significant.

CONCLUSION

The combination of ECG-LVH and prolonged QT is associated with a higher risk of ischaemic stroke compared with either condition in isolation, and the stroke risk for each condition does not depend on the presence of the other.

Cardiovascular and renal complications in patients with resistant hypertension

With an increased prevalence, resistant hypertension is recognized as an entity with a high cardiovascular morbidity and mortality. In a large cohort of patients with resistant hypertension, the crude incidence rate of total cardiovascular events reached 4.32 per 100 patient-years of follow-up (19.6 %), with a cardiovascular mortality of 8.3 % (incidence rate of 1.72 per 100 patient-years). Cardiovascular event rates are significantly higher in resistant hypertensives compared with non-resistant (18.0 % versus 13.5 %). In the same way, the prevalence of established cardiovascular and renal disease, as the asymptomatic organ damage (represented by left ventricular hypertrophy, carotid wall thickening, arterial stiffness, and microalbuminuria) is higher in these patients. Many studies have demonstrated a strong association between damage to these organs with higher blood pressure levels, the diagnosis of true resistant hypertension, and refractory hypertension. All efforts should be employed in order to control blood pressure and also to regress and/or prevent subclinical cardiovascular and renal damage. The focus should be on prevention of cardiovascular and renal complications, improving the prognosis of resistant hypertension.

Inter-relationship between electrocardiographic left ventricular hypertrophy and QT prolongation as predictors of increased risk of mortality in the general population

BACKGROUND

Prolonged-QT commonly coexists in the ECG with left ventricular hypertrophy (ECG-LVH). However, it is unclear whether to what extent QT prolongation coexisting with ECG-LVH can explain the prognostic significance of ECG-LVH, and whether prolonged-QT coexisting with ECG-LVH should be considered as an innocent consequence of ECG-LVH.

METHODS AND RESULTS

The study population consisted of 7506 participants (mean age, 59.4±13.3 years; 49% whites; and 47% men) from the US Third National Health and Nutrition Examination Survey. ECG-LVH was defined by Cornell voltage criteria. Prolonged heart-rate-adjusted QT (prolonged-QTa) was defined as QTa≥460 ms in women or 450 ms in men. Cox proportional hazards analysis was used to calculate the hazard ratios with 95% confidence intervals for the risk of all-cause mortality for various combinations of ECG-LVH and prolonged-QTa. ECG-LVH was present in 4.2% (N=312) of the participants, of whom 16.4% had prolonged-QTa. In a multivariable-adjusted model and compared with the group without ECG-LVH or prolonged-QTa, mortality risk was highest in the group with concomitant ECG-LVH and prolonged-QTa (hazard ratio, 1.63; 95% confidence interval, 1.12-2.36), followed by isolated ECG-LVH (1.48; 1.24-1.77), and then isolated prolonged-QTa (1.27; 1.12-1.46). In models with similar adjustment where ECG-LVH and prolonged-QTa were entered as 2 separate variables and subsequently additionally adjusted for each other, the mortality risk was essentially unchanged for both variables.

CONCLUSIONS

Although prolonged-QT commonly coexists with LVH, both are independent markers of poor prognosis. Concomitant presence of prolonged-QT and ECG-LVH carries a higher risk than either predictor alone.

Influence of the left ventricular types on QT intervals in hypertensive patients

Objective:

To investigate the possible electrophysiological background of the greater excitability of concentric and eccentric left ventricular hypertrophy types in relation to the asymmetric type.

Methods:

187 patients with essential hypertension, without ishaemic heart disease were divided into three groups with regard to left ventricule type: concentric (relative wall thickness >0.42, interventricular septum/left ventricular posterior wall ≤1.3), eccentric (left ventricular diameter in systoles >32, relative wall thickness <0.42), asymmetric left ventricular hypertrophy (interventricular septum/left ventricular posterior wall >1.3), and three subgroups: mild (interventricular septum or left ventricular posterior wall 11-12 mm), moderate (interventricular septum or left ventricular posterior wall 13-14 mm) and severe left ventricular hypertrophy (interventricular septum or left ventricular posterior wall ≥15 mm). In all patients QT intervals, QT dispersion, left ventricular mass index and ventricular arrhythmias were measured. An upper normal limit for QT corrected interval: 450/460 ms for men/women; for QT dispersion: 70 ms.

Results:

The QT corrected interval and QT dispersion were increased in severe concentric and eccentric left ventricular hypertrophy (443 and 480 ms for QT corrected; 53 and 45 ms for QT dispersion, respectively), not significantly. QT dispersion in men with severe left ventricular hypertrophy was significantly enlarged (67.5 vs. 30 ms, p=0.047). QT interval was significantly longer in patients with complex ventricular arrhythmias (p=0.037).

Conclusion:

No significant association of QT intervals or QT dispersion with the degree/type of left ventricular hypertrophy was found. QT corrected interval and QT dispersion tend to increase proportionally to the left ventricular mass only in the concentric and eccentric type.

QT dispersion predicts mortality and correlates with both coronary artery calcification and atherosclerosis in hemodialysis patients

PURPOSE

QT dispersion (QTd) was shown to be an independent predictor of mortality in hemodialysis (HD) patients. It may be hypothesized that coronary artery calcification is related to QTd in HD patients because widespread calcification may also involve the cardiac conducting system in these patients. In this study, we aimed to investigate the relationships of corrected QTd (QTcd) with coronary artery calcification score (CACS), carotid plaque score (CPS) and possible influence of these parameters on survival of HD patients.

METHODS

Seventy-two HD patients (33 male, 39 female) were enrolled into the study. Mean age of the patients was 44 ± 12 years. Mean follow-up duration was 77 ± 24 months. CACS was determined by computed tomography. QTcd values were calculated as the difference of maximum and minimum QT intervals. Left ventricular mass index (LVMI) and CPS were measured by echocardiography.

RESULTS

QTcd was significantly correlated with CACS (r = 0.233, p = 0.049), CPS (r = 0.354, p = 0.003) and LVMI (p = 0.011, r = 0.299). CPS was found to be significantly higher in the group with high QTcd (>60 ms) [2 (1-4) versus 0 (0-1), p = 0.02]. CACS was significantly correlated with age (r = 0.44, p < 0.001), LVMI (r = 0.52, p < 0.001) and CPS (r = 0.32, p = 0.003). In Kaplan-Meier analysis, survival of patients with high QTcd was significantly lower than the patients with low QTcd. In Cox regression analysis for predicting mortality, age, serum albumin and QTcd were found to be the independent predictors of mortality.

CONCLUSIONS

QTcd independently predicted mortality, and it was significantly associated with coronary artery calcification, left ventricular hypertrophy and atherosclerosis in HD patients.

Resistant hypertension and target organ damage

Cardiovascular (CV) complications such as myocardial infarction, heart failure, stroke and renal failure are related to both the degree and the duration of blood pressure (BP) increase. Resistant hypertension (RH) is associated with a higher risk of CV complications and a higher prevalence of target organ damage (TOD). The relationship between CV disease and TOD can be bidirectional. Elevated BP in RH may cause CV structural and functional alterations, and the development or persistence of left ventricular hypertrophy, aortic stiffness, atherosclerotic plaques, microvascular disease and renal dysfunction, may render hypertension more difficult to control. Specifically, RH is related to several conditions, including obesity, sleep apnea, diabetes, metabolic syndrome and hyperaldosteronism, characterized by an overexpression of humoral and hormonal factors that are involved in the development and maintenance of TOD. Optimal therapeutic strategies, including pharmacological treatment and innovative invasive methodologies, have been shown to achieve adequate BP control and induce the regression of TOD, thereby potentially improving patient prognosis.

Prognostic significance of baseline heart rate and its interaction with beta-blocker use in resistant hypertension: a cohort study

BACKGROUND

The prognostic significance of heart rate (HR) and its relationship with beta-blocker use are controversial and have never been evaluated in resistant hypertension.

METHODS

In a prospective study, 528 patients with resistant hypertension had HR measured on clinical examination, electrocardiography (ECG), and during ambulatory blood pressure monitoring. Primary endpoints were a composite of fatal and nonfatal cardiovascular events, all-cause and cardiovascular mortality. Multivariable Cox regression was used to assess the associations between slow HR (< 60 bpm or < 55 bpm for nighttime HR) and fast HR (> 75 bpm or > 70 bpm for nighttime HR) and the occurrence of endpoints in relation to the reference middle HR (60-75 bpm) subgroup.

RESULTS

After a median follow-up of 4.8 years, 62 patients died, 44 from cardiovascular causes; and 94 cardiovascular events occurred. Fast and slow HRs were mainly predictors of mortality, and ambulatory HRs were more significant risk markers than clinic or ECG HR. A slow 24-hour HR was a predictor of the composite endpoint (hazard ratio, 2.0; 95% confidence interval [CI], 1.2-3.4), whereas both slow and fast ambulatory HRs were predictors of cardiovascular mortality (hazard ratio, 2.3; 95% CI, 1.1-5.1). Four hundred and seventeen patients (79%) were using beta-blockers and this affected the HR prognostic value. A fast HR was a more significant risk marker in patients using beta-blockers, whereas a slow HR was a predictor mainly in those not using beta-blockers.

CONCLUSIONS

There is an overall U-shaped relationship between HRs, particularly when measured during ambulatory monitoring, and prognosis in resistant hypertension. A fast HR is a significant predictor in patients using beta-blockers, while a slow heart rate is a more important predictor in those not using beta-blockers.

Prognostic factors in resistant hypertension: implications for cardiovascular risk stratification and therapeutic management

Resistant hypertension (RH) is defined as uncontrolled office blood pressure (BP) in spite of the use of at least three antihypertensive medications. Although its condition has a high prevalence, it is still understudied, and its prognosis is not well established. Some prospective studies evaluated the prognostic value of ambulatory BP monitoring, ECG and renal parameters. They pointed out that ambulatory BPs are important predictors of cardiovascular morbidity and mortality, whereas office BP has no prognostic value. The diagnosis of true RH and the nondipping pattern are also valuable predictors of cardiovascular outcomes. Moreover, several ECG (prolonged ventricular repolarization, serial changes in the strain pattern and left ventricular hypertrophy) and renal parameters (albuminuria and reduced glomerular filtration rate) are also powerful cardiovascular risk markers in RH. These markers and others yet unexplored, such as arterial stiffness and serum biomarkers, may improve cardiovascular risk stratification in these very high-risk patients.

Protein kinase C (PKC)ζ-mediated Gαq stimulation of ERK5 protein pathway in cardiomyocytes and cardiac fibroblasts

Gq-coupled G protein-coupled receptors (GPCRs) mediate the actions of a variety of messengers that are key regulators of cardiovascular function. Enhanced Gα(q)-mediated signaling plays an important role in cardiac hypertrophy and in the transition to heart failure. We have recently described that Gα(q) acts as an adaptor protein that facilitates PKCζ-mediated activation of ERK5 in epithelial cells. Because the ERK5 cascade is known to be involved in cardiac hypertrophy, we have investigated the potential relevance of this pathway in cardiovascular Gq-dependent signaling using both cultured cardiac cell types and chronic administration of angiotensin II in mice. We find that PKCζ is required for the activation of the ERK5 pathway by Gq-coupled GPCR in neonatal and adult murine cardiomyocyte cultures and in cardiac fibroblasts. Stimulation of ERK5 by angiotensin II is blocked upon pharmacological inhibition or siRNA-mediated silencing of PKCζ in primary cultures of cardiac cells and in neonatal cardiomyocytes isolated from PKCζ-deficient mice. Moreover, upon chronic challenge with angiotensin II, these mice fail to promote the changes in the ERK5 pathway, in gene expression patterns, and in hypertrophic markers observed in wild-type animals. Taken together, our results show that PKCζ is essential for Gq-dependent ERK5 activation in cardiomyocytes and cardiac fibroblasts and indicate a key cardiac physiological role for the Gα(q)/PKCζ/ERK5 signaling axis.

Serum 25-hydroxyvitamin D, calcium, phosphorus, and electrocardiographic QT interval duration: findings from NHANES III and ARIC

CONTEXT

Disturbances in 25-hydroxyvitamin D, calcium, and phosphorus concentrations have been associated with increased risks of total and cardiovascular mortality. It is possible that changes in electrocardiographic QT interval duration may mediate these effects, but the association of 25-hydroxyvitamin D, phosphorus, and calcium concentrations with QT interval duration has not been evaluated in general population samples.

OBJECTIVE

The objective of the study was to evaluate the association of 25-hydroxyvitamin D, phosphorus, and calcium concentrations with QT interval duration in two large samples of the U.S. general population.

DESIGN

This study included cross-sectional analyses the Third National Health and Nutrition Survey (NHANES III) and the Atherosclerosis Risk in Communities (ARIC) study.

SETTING

The study was conducted in the general community.

PATIENTS OR OTHER PARTICIPANTS

Patients included 7,312 men and women from NHANES III and 14,825 men and women from the ARIC study.

INTERVENTIONS

Serum 25-hydroxyvitamin D, total and ionized calcium, and inorganic phosphorus were measured in NHANES III, and serum total calcium and inorganic phosphorus were measured in ARIC.

MAIN OUTCOME MEASURE

QT interval duration was obtained from standard 12-lead electrocardiograms.

RESULTS

In NHANES III, the multivariate adjusted differences in average QT interval duration comparing the highest vs. the lowest quartiles of serum total calcium, ionized calcium, and phosphorus were -3.6 msec (-5.8 to -1.3; P for trend = 0.005), -5.4 msec (-7.4 to -3.5; P for trend <0.001), and 3.9 msec (2.0-5.9; P for trend <0.001), respectively. The corresponding differences in ARIC were -3.1 msec (-4.3 to -2.0; P for trend <0.001), -2.9 msec (-3.8 to -1.9; P for trend <0.001), and 2.3 msec (1.3-3.3; P for trend <0.001). No association was found between 25-hydroxyvitamin D concentrations and QT interval duration.

CONCLUSIONS

In two large samples of the general population, QT interval duration was inversely associated with the serum total and ionized calcium and positively associated with serum phosphorus.

[Computerized interpretation of the electrocardiogram in the diagnosis of left ventricular hypertrophy. The ELECTROPRES project]

INTRODUCTION

Despite its low sensitivity, the electrocardiogram (ECG) is the tool used the most in the daily practice for detection of left ventricular hypertrophy (LVH). This study has aimed to assess the impact of the computerized interpretation of the ECG on the diagnosis of LVH in the practical clinical setting.

METHODS

ELECTROPRES is a project based on a free access computer platform that permits an online interpretation of the electrocardiogram. It includes 19 different left LVH criteria previously validated by echocardiography in a substudy. We analyzed the data from the first 669 patients with essential arterial hypertension (ATH) included in the ELECTROPRES platform from 21 primary care centers in 9 of the 17 Spanish autonomous communities.

RESULTS

Up to April 2010, a cohort of 669 hypertensive patients (51.7% women), with a mean age of 66.3±11.89 years, was analyzed. The mean evolution of the disease was 8 years, and the patients had been receiving an average of 2.4 antihypertensive agents. Systolic blood pressure was 139±17 mmHg and diastolic blood pressure 76±11. The ECG-known frequency of LVH was 3%. The prevalence of LVH increased up to 33.3% (P<0.001) with the ELECTROPRES platform. When all the criteria were independently examined, the Lewis index (R-I+S-III) and the Cornell product [(R-aVL+S-V3 (+6 for women)] were those in which the most cases of left ventricular hypertrophy were detected (24.8% and 13.3%, respectively). The Lewis index and the Cornell product were the criteria that detected more cases of left ventricular hypertrophy, regardless of the AHT stage and of the presence of cardiovascular complications.

CONCLUSIONS

The ECG computerized reading (ELECTROPRES platform) significantly increases detection of left ventricular hypertrophy in a population of essential hypertense subjects compared to conventional detection with the ECG by the physician in the usual clinical practice setting.

Resistant hypertension and left ventricular hypertrophy: an overview

Available data on subclinical cardiac damage in resistant hypertension (RH) are rather scanty. Thus, we sought to review the literature focusing on the association between RH and left ventricular hypertrophy (LVH). A MEDLINE search was performed to identify relevant articles using the key words "resistant hypertension, " "refractory hypertension," "left ventricular hypertrophy," "cardiac damage," and "left ventricular dysfunction." Full articles published in the English language in the last two decades (December 1, 1989, to July 31, 2010) reporting studies in adult or elderly individuals, were considered. Checks of the reference lists of selected articles complemented the electronic search. A total of 11 cross-sectional and longitudinal studies, including 3325 patients attending outpatient hypertension clinics, were considered. Prevalence rates of echocardiographic LVH, as assessed by updated criteria, ranged from 55% to 75% of patients with RH, peaking to 91% in the subgroup with concomitant electrocardiographic (ECG) LV strain. Reduction in ECG-LVH induced by treatment showed a relevant beneficial impact on cardiovascular prognosis. These data support the view that initial and on-treatment assessment of LVH in patients with RH is important for cardiovascular risk monitoring and therapeutic strategies decision-making.

QT Dispersion Measured by Automatic Computerized 12-Lead Electrocardiography Contributes Significantly to Detection of Left Ventricular Hypertrophy in Japanese Patients

This study assessed the diagnostic value of QT dispersion for left ventricular hypertrophy (LVH) as determined by echocardiography. The QT and QRS interval parameters were determined automatically using computerized 12-lead electrocardiography in 153 Japanese outpatients. Corrected QT dispersion (QTcD) and maximal QRS duration (MaxQRS) were significantly correlated with left ventricular mass index. The sum of QTcD and MaxQRS showed the highest correlation with left ventricular mass index among QT and QRS interval parameters and their combinations. The cut-off points for LVH discrimination in this study were different to those reported in Western, mainly Caucasian, populations, suggesting the need for ethnicity-specific LVH detection criteria. A scoring system derived from multiple logistic regression analysis, employing a combination of QTcD, QRS time–voltage product and ST-T change, showed a specificity of 86.3%. It was concluded that QTcD, in addition to QRS time–voltage product and ST-T change, improved the detection of LVH.

Prognostic impact of baseline and serial changes in electrocardiographic left ventricular hypertrophy in resistant hypertension

BACKGROUND

The prognostic value of electrocardiographic left ventricular hypertrophy (ECG-LVH) in resistant hypertension (RH) is unknown. The aim was to evaluate the importance of baseline and serial changes in ECG-LVH as predictors of cardiovascular morbidity and mortality in patients with RH.

METHODS

At baseline and during follow-up, 552 resistant hypertensive patients had 3 ECG-LVH criteria obtained: Sokolow-Lyon, Cornell voltage, and Cornell voltage-duration product. Primary end points were a composite of fatal and nonfatal cardiovascular events and all-cause and cardiovascular mortalities. Total strokes and coronary heart disease (CHD) events were secondary end points. Multiple Cox regression assessed the associations between time-varying ECG-LVH and subsequent end points.

RESULTS

After a median follow-up of 4.8 years, 70 patients died, 46 from cardiovascular causes; and 109 total cardiovascular events occurred, 46 strokes, and 44 CHD events. After adjustment for several cardiovascular risk factors, baseline Cornell voltage and product, but not Sokolow-Lyon voltage, were independent predictors of the composite end point and of all-cause and cardiovascular mortalities. Reductions of all ECG-LVH criteria were protective factors for the composite end point: a 1-SD (1.1 mV) reduction in Sokolow-Lyon voltage was associated with a 35% lower risk (95% CI 10%-53%) of cardiovascular events, whereas prevention or regression of Cornell product LVH criterion implied a 40% lower risk (95% CI 11%-60%). Baseline and serial changes in Sokolow-Lyon voltage were independent predictors of strokes, whereas Cornell voltage was predictive of CHD events.

CONCLUSIONS

Baseline and serial changes in ECG-LVH predict cardiovascular morbidity and mortality in RH patients. Antihypertensive treatment targeted at regression or prevention of ECG-LVH may improve prognosis.

Clinical correlates and heritability of QT interval duration in blacks: the Jackson Heart Study

BACKGROUND

Electrocardiographic QT interval prolongation is a risk factor for sudden cardiac death and drug-induced arrhythmia. The clinical correlates and heritability of QT interval duration in blacks have not been well studied despite their higher risk for sudden cardiac death compared with non-Hispanic whites. We sought to investigate potential correlates of the QT interval and estimate its heritability in the Jackson Heart Study.

METHODS AND RESULTS

The Jackson Heart Study comprises a sample of blacks residing in Jackson, Miss, of whom 5302 individuals with data at the baseline examination were available for study. Jackson Heart Study participants on QT-altering medications, with bundle-branch block, paced rhythm, atrial fibrillation/flutter, or other arrhythmias were excluded, resulting in a sample of 4660 individuals eligible for analyses. The relation between QT and potential covariates was tested using multivariable stepwise linear regression. Heritability was estimated using Sequential Oligogenic Linkage Analysis Routine in a subset of 1297 Jackson Heart Study participants in 292 families; the remaining sample included unrelated individuals. In stepwise multivariable linear regression analysis, covariates significantly associated with QT interval duration included R-R interval, sex, QRS duration, age, serum potassium, hypertension, body mass index, coronary heart disease, diuretic use, and Sokolow-Lyon voltage (P < or = 0.01 for all). The heritability of QT interval duration in the age-, sex-, and R-R interval-adjusted model and in the fully adjusted model was 0.41 (SE, 0.07) and 0.40 (SE, 0.07; P < 10(-11) for both), respectively.

CONCLUSIONS

There is substantial heritability of adjusted QT interval in blacks, supporting the need for further investigation to identify its genetic determinants.

Prognostic value of ventricular repolarization prolongation in resistant hypertension: a prospective cohort study

OBJECTIVE

The prognostic value of prolonged ventricular repolarization in patients with resistant hypertension is unknown. The aim of this prospective study was to investigate the usefulness of electrocardiographic QT-interval parameters as predictors of cardiovascular morbidity and mortality.

METHODS

At baseline, 538 resistant hypertensive patients had five QT-interval components measured in standard 12-lead ECGs: maximum QRS, QTpeak, QTend, JT and Tpeak-to-end-interval durations. Primary endpoints were a composite of fatal and nonfatal cardiovascular events, all-cause and cardiovascular mortalities. Multiple Cox regression assessed the associations between QT-interval parameters and subsequent endpoints.

RESULTS

After a median follow-up of 4.8 years, 69 (12.8%) patients died, 46 from cardiovascular causes, and 107 (19.9%) fatal or nonfatal cardiovascular events occurred. After adjustment for several traditional risk factors, including 24-h ambulatory systolic blood pressure, an increment of 1 SD (35 ms) in QTcend-interval was associated with hazard ratios of 1.38 (1.15-1.67), 1.51 (1.16-1.98) and 1.30 (1.03-1.64), respectively, for the composite endpoint, cardiovascular mortality and all-cause mortality. Further adjustment for left ventricular hypertrophy attenuated the relative risks, but they remained significant for cardiovascular mortality (1.45, 1.07-1.97) and for the composite endpoint (1.35, 1.11-1.66). After full adjustment, a prolonged QTcend-interval (> or =460 ms) conferred a 1.7-fold (1.1-2.6) higher risk of having a future fatal or nonfatal cardiovascular event. No other QT-interval component added further prognostic information to QTcend-interval duration.

CONCLUSIONS

Prolonged ventricular repolarization is a risk marker for cardiovascular morbidity and mortality in patients with resistant hypertension, over and beyond traditional cardiovascular risk factors, including ambulatory blood pressure and left ventricular hypertrophy.

Ambulatory arterial stiffness index or pulse pressure: which correlates better with arterial stiffness in resistant hypertension?

The ambulatory arterial stiffness index (AASI) is a recently proposed index derived from 24-h ambulatory blood pressure monitoring (ABPM) for the evaluation of arterial stiffness. In this cross-sectional study we investigated whether AASI reflects arterial stiffness in patients with resistant hypertension by comparing AASI and ambulatory pulse pressure (PP) with aortic pulse wave velocity (PWV), a measure of arterial stiffness, in 391 resistant hypertensives. Clinical, laboratory and echocardiographic variables, 24-h ABPM and aortic PWV (measured using the Complior device) were obtained. AASI was calculated as 1--the regression slope of 24-h diastolic on systolic blood pressure (BP). Statistical analysis involved single and multiple linear regressions to assess the correlations between the two ABPM variables and PWV, both unadjusted and adjusted for potential confounders (age, gender, body height, presence of diabetes, 24-h mean arterial pressure [MAP], heart rate, and nocturnal BP reduction). Ambulatory PP and aortic PWV were independently associated with age, gender, presence of diabetes, and 24-h MAP, whereas AASI was associated with age, diabetes, and nocturnal diastolic BP reduction. PP showed stronger unadjusted (r=0.39, p<0.001) and adjusted (r=0.22, p<0.001) correlations with aortic PWV than AASI (r=0.12, p=0.032 and r= -0.04, p=0.47, respectively). In the analysis of subgroups stratified by gender, age, presence of atherosclerotic diseases and diabetes, dipping pattern, and ambulatory BP control, the superiority of PP over AASI was apparent in all subgroups. In conclusion, 24-h ambulatory PP was better correlated to arterial stiffness, as evaluated by aortic PWV, than the novel AASI, in patients with resistant hypertension.

Pulse pressure or dipping pattern: which one is a better cardiovascular risk marker in resistant hypertension?

OBJECTIVE

Nocturnal blood pressure (BP) reduction and ambulatory pulse pressure (PP) are well known prognostic markers obtained from ambulatory BP monitoring (ABPM). The aim of this study is to investigate which one of these ABPM parameters is related to high cardiovascular risk profile in resistant hypertension, based on their associations with target organ damage (TOD).

METHODS

Clinical-demographic, laboratory and ABPM variables were recorded in a cross-sectional study involving 907 resistant hypertensive patients. Nocturnal systolic BP reduction and 24-h PP were assessed both as continuous and dichotomized variables (PP at the upper tertile value: 63 mmHg). Statistical analyses included bivariate tests and multivariate logistic regression with each TOD as the dependent variable.

RESULTS

Patients with the nondipping pattern and high 24-h PP shared some characteristics: they were older, had higher prevalence of cerebrovascular disease and nephropathy, higher office and 24-h BP levels, increased serum creatinine and microalbuminuria, and higher left ventricular mass index than their counterparts. Additionally, patients with high PP had a greater prevalence of diabetes and other TOD. In multivariate logistic regression, high PP was independently associated with all TODs even after adjustment for sex, age, BMI, cardiovascular risk factors, 24-h mean arterial pressure and antihypertensive treatment, whereas nondipping pattern was only associated with hypertensive nephropathy. Furthermore, PP was more strongly associated with the number of TOD than the nocturnal systolic blood pressure (SBP) fall.

CONCLUSIONS

In a large group of resistant hypertensive patients, an increased 24-h PP shows a closer correlation with high cardiovascular risk profile than the nocturnal BP reduction.

Recent ventricular repolarization markers in resistant hypertension: are they different from the traditional QT interval?

BACKGROUND

Two electrocardiographic markers of ventricular repolarization abnormalities have been recently proposed: spatial T-wave axis deviation and T(peak)-T(end)-interval duration. The aim of this study was to evaluate these markers in patients with resistant hypertension, particularly their relationships with left ventricular mass (LVM) and geometric patterns, in comparison with the more traditional marker, the QTc interval.

METHODS

In a cross-sectional study, 810 resistant hypertensive patients were evaluated. Clinical, laboratory, electrocardiographic, 24-h blood pressures and echocardiographic variables were obtained. Maximum T(peak)-T(end)-interval duration (Tpe(max)) was considered prolonged if it was beyond the upper quartile value (120 ms), and the spatial T-wave axis on the frontal plane was considered abnormally deviated if >105 degrees or < 15 degrees . Statistical analysis involved bivariate tests, multivariate logistic regression and analysis of covariance.

RESULTS

Tpe(max)-interval prolongation, like QTc-interval prolongation, was found to be associated with body mass index, 24-h systolic blood pressure (SBP), indexed LVM, serum potassium, and heart rate. Abnormal T-axis deviation was associated with male gender, presence of coronary heart disease, serum creatinine, 24-h SBP, LVM, and serum potassium. All three repolarization parameters were shown to be associated with increased LVM, after adjustment for possible confounders. However, when included together into the same model, only abnormal T-axis and QTc-interval prolongation remained independently associated with LVM. All three parameters were also increased in patients with concentric hypertrophy geometric pattern.

CONCLUSIONS

Both the recently proposed repolarization parameters are associated with increased LVM and hypertrophy in patients with resistant hypertension, but only abnormal T-wave axis deviation appears to have distinct and additive relationships to the more classic marker, the QTc interval. Their prognostic values should be addressed in prospective studies .

Electrocardiographic criteria for left ventricular hypertrophy in children

Previous studies to determine the sensitivity of the electrocardiogram (ECG) for left ventricular hypertrophy (LVH) in children had their imperfections: they were not done on an unselected hospital population, several criteria used in adults were not applied to children, and obsolete limits of normal for the ECG parameters were used. Furthermore, left ventricular mass (LVM) was taken as the reference standard for LVH, with no regard for other clinical evidence. The study population consisted of 832 children from whom a 12-lead ECG and an M-mode echocardiogram were taken on the same day. The validity of the ECG criteria was judged on the basis of an abnormal LVM index, either alone or in combination with other clinical evidence. The ECG criteria were based on recently established age-dependent normal limits. At 95% specificity, the ECG criteria have low sensitivities (<25%) when an elevated LVM index is taken as the reference for LVH. When clinical evidence is also taken into account, the sensitivity improved considerably (<43%). Sensitivities could be further improved when ECG parameters were combined. The sensitivity of the pediatric ECG in detecting LVH is low but depends strongly on the definition of the reference used for validation.

Relation of left ventricular hypertrophy with systemic inflammation and endothelial damage in resistant hypertension

The relation between left ventricular hypertrophy (LVH) and unfavorable cardiovascular prognosis may involve systemic inflammation and endothelial dysfunction/damage. The aim of this study was to investigate in a cross-sectional design the relationships of LVH with C-reactive protein (CRP) levels (a marker of systemic low-grade inflammation) and with microalbuminuria (a marker of glomerular endothelial damage) in 705 patients with resistant hypertension. At baseline, all were submitted to a laboratory evaluation including 24-hour urinary albumin excretion, 2D echocardiogram, and 24-hour ambulatory blood pressure monitoring. A total of 463 patients also had high-sensitivity CRP levels determined. LVH was defined as an indexed left ventricular mass >110 g/m(2) in women and >125 g/m(2) in men. Microalbuminuria was evaluated in 3 categories: low normal (<15 mg/24 hours), high normal (between 15 and 29 mg/24 hours), and abnormal (between 30 and 299 mg/24 hours). CRP was dichotomized at the median value (3.7 mg/L). Associations with LVH were examined after adjustment for all of the potential confounders by multivariate logistic regression. A total of 534 patients (75.7%) had LVH. After full adjustment, both abnormal microalbuminuria (odds ratio: 1.97; 95% CI: 1.04 to 3.73) and high CRP (OR: 1.76; 95% CI: 1.06 to 2.93) were independently associated with LVH occurrence. The high-normal albuminuria was associated with a borderline significant 46% increased chance of having LVH. Furthermore, the association between high CRP and LVH was observed exclusively in the subgroup with normal albuminuria. In conclusion, both systemic inflammation and endothelial damage were associated with LVH occurrence. These relationships offer insight into the pathophysiological mechanisms linking LVH to atherosclerosis and to increased cardiovascular morbidity and mortality.

Cardiac Vascular Calcification and QT Interval in ESRD Patients: Is There a Link?

We will present our experience and our preliminary data about the correlation between cardiac calcification and QT interval (and QT dispersion) in uraemia. We studied 32 haemodialysis (HD) patients (age 69 +/- 16 years, time on dialysis 32 +/- 27 months) and 12 chronic kidney disease stage 4 (CKD-4) patients (age 66 +/- 17 years, uraemia duration 38 +/- 16 months). The patients were characterized by a good mineral control, as shown by serum phosphate levels (3.6 +/- 1.3 mg/dl in CKD-4 and 4.3 +/- 1.6 mg/dl in HD patients) and Ca x P product (46 +/- 17 and 49 +/- 16 mg(2)/dl(2), respectively). The parathyroid hormone levels were higher in HD than CKD-4 patients (p < 0.0001). A TC score >400 was found to be highly prevalent in both groups. Significantly more HD patients (62.5%) showed cardiac calcification than CKD-4 patients (33%; p = 0.01). The patients were matched for TC scores higher or lower than 400. The two groups differed by gender (p < 0.05), age (p = 0.026), frequency of diabetes mellitus (p < 0.01), uraemia follow-up period (p < 0.001), low-density lipoprotein cholesterol level (p = 0.009), Ca x P product (p = 0.002), parathyroid hormone level (p < 0.0001), and corrected QT dispersion (p < 0.0001). The QT interval was higher in HD and CKD-4 patients with higher TC scores (approximately 11%), but QT interval dispersion was significantly higher in patients with TC scores >400. QT dispersion showed a linear correlation with TC scores in both groups (r = 0.899 and p < 0.0001 and r = 0.901 and p < 0.0001). Male gender, age, time (months) of uraemia, low-density lipoprotein cholesterol, albumin, calcium x phosphorus product, parathyroid hormone, and TC score are important determinants of QT dispersion. Our data show that it is possible to link dysrhythmias and cardiac calcification in uraemic patients.

Importance of the Electrocardiographic Strain Pattern in Patients With Resistant Hypertension

The electrocardiographic strain pattern is a marker of left ventricular hypertrophy and adverse cardiovascular prognosis. The objective of this study was to assess the factors associated with the presence of ECG strain in patients with resistant hypertension and, specifically, to evaluate the relationships between strain and left ventricular mass (LVM) and structure. In a cross-sectional design, 440 resistant hypertensive subjects were evaluated. Clinical, laboratory, electrocardiographic, 24-hour ambulatory blood pressures, and echocardiographic variables were obtained. Statistical analysis involved bivariate tests, analysis of covariance, and multivariate logistic regression. An ECG strain pattern was present in 101 patients (23%). Patients with strain were more frequently men with lower body mass index, had more target-organ damage, higher 24-hour blood pressure, higher serum creatinine and 24-hour microalbuminuria, and more prolonged QT interval duration than those without strain. After controlling for all covariates, the presence of strain remained associated with increased LVM and wall thicknesses, both in all patients and also in those with echocardiographic left ventricular hypertrophy. Furthermore, the presence of ECG strain was associated with increased LVM (P<0.001), higher 24-hour systolic blood pressure (P<0.001), prolonged maximum QTc-interval duration (P<0.001), lower waist circumference (P=0.009), male gender (P=0.011), physical inactivity (P=0.020), higher serum creatinine (P=0.031) and fasting glycemia (P=0.027), and the presence of coronary heart disease (P=0.001) and peripheral arterial disease (P=0.045). Thus, in resistant hypertension patients, the presence of ECG strain is independently associated with increased left ventricular wall thicknesses and mass and also with other potentially adverse factors. These relationships offer insight into the known association between strain and unfavorable cardiovascular prognosis.

Is Electrocardiography Still Useful in the Diagnosis of Cardiac Chamber Hypertrophy and Dilatation?

The echocardiogram undoubtedly is part of the cardiologist's armamentarium in the diagnosis and elucidation of cardiac abnormalities, but the ECG still continues to be the most frequently recorded noninvasive test in medicine. For many patients, particularly those who have newly diagnosed hypertension, a 12-lead ECG recording may be the only test that is required as a baseline measure. For those who have possible heart failure, an ECG and B-type natriuretic peptide measurement may be sufficient to obviate the need for an echocardiogram. Electrocardiography and echocardiography will continue to live side-by-side for the foreseeable future.