The Finnish Cardiovascular Study (FINCAVAS): characterising patients with high risk of cardiovascular morbidity and mortality

Genetic risk score for coronary artery calcification and its predictive ability for coronary artery disease

Aim

The modest added predictive value of the existing genetic risk scores (GRSs) for coronary artery disease (CAD) could be partly due to missing genetic components, hidden in the genetic architecture of intermediate phenotypes such as coronary artery calcification (CAC). In this study, we investigated the predictive ability of CAC GRS for CAD.

Materials and methods

We investigated the association of CAC GRSs with CAD and coronary calcification among the participants in the Ludwigshafen Risk and Cardiovascular Health study (LURIC) (n = 2742), the Tampere Vascular Study (TVS) (n = 133), and the Tampere Sudden Death Study (TSDS) (n = 660) using summary data from the largest multi-ancestry GWAS meta-analysis of CAC to date. Added predictive value of the CAC GRS over the traditional CVD risk factors as well as metaGRS, a GRS for CAD constructed with 1.7 million genetic variants, was tested with standard train-test machine learning approach using the LURIC data, which had the largest sample size.

Results

CAC GRS was significantly associated with CAD in LURIC (OR=1.41, 95 % CI [1.28-1.55]), TVS (OR=1.79, 95 % CI [1.05-3.21]) as well as in TSDS (OR=4.20, 95 % CI [1.74-10.52]). CAC GRS showed strong association with calcification areas in left (OR=1.78, 95 % CI [1.16-2.74]) and right (OR=1.71, 95 % CI [1.98-2.67]) coronary arteries. There was statistically significant added predictive value of the CAC GRS for CAD over the used traditional CVD risk factors (AUC 0.734 vs 0.717, p-value = 0.02). Furthermore, CAC GRS improved the prediction accuracy for CAD when combined with metaGRS.

Conclusions

This study showed that CAC GRS is a new risk marker for CAD in three European cohorts, with added predictive value over the traditional CVD risk factors.

Use of ST/HR hysteresis decreases false positive rate in exercise electrocardiography test of middle-aged asymptomatic women

BACKGROUND

Exercise electrocardiography (ECG) is a common diagnostic and prognostic method for the detection of coronary artery disease (CAD). However, its accuracy in asymptomatic women has not been comprehensively investigated and the diagnostic criteria may require refinements. This study evaluated the performance of ECG-derived ST/HR-index, ST/HR hysteresis and ST-segment depression parameters among asymptomatic middle-aged women.

METHODS

108 women (mean age 56 ± 4 years) performed exercise ECG test on treadmill until exhaustion three times within a nine-month period. False-positive rates of maximum ST/HR-index, ST/HR hysteresis, and ST-segment depression values measured from 12 leads at peak exercise and after one-minute recovery were evaluated with recommended diagnostic partition values. Repeatability was assessed with intraclass correlation (ICC) and Bland-Altman plot analysis.

RESULTS

False-positive rate was lower for all variables when a two‑lead configuration was used instead of a single‑lead configuration. Using a two‑lead configuration, ST/HR hysteresis (0-1.9 %) and ST-segment depression after one-minute recovery (0-2.8 %) had lower false-positive rates compared to ST/HR index (3.7-20.4 %) and ST-segment depression at peak exercise (9.3-27.8 %). ICC values indicated moderate repeatability for ST/HR hysteresis while ST/HR index, ST-segment at peak exercise, and ST-segment after one-minute recovery had moderate-to-good repeatability. Bland-Altman analysis indicated poor repeatability for all evaluated ECG variables.

CONCLUSION

In asymptomatic middle-aged women, practitioners should prefer the use of ST/HR hysteresis and ST-segment after one-minute recovery over the conventional ST-segment depression at peak exercise or ST/HR index, and evaluate the ECG data from a two‑lead configuration instead of single‑lead.

Prediction of Sudden Cardiac Death With Ultra-Short-Term Heart Rate Fluctuations

BACKGROUND

Conventional measures of heart rate variability (HRV) have shown only modest associations with sudden cardiac death (SCD). Detrended fluctuation analysis (DFA), with novel methodological developments to evaluate the short-term scaling exponent, is a potentially superior method compared to conventional HRV tools.

OBJECTIVES

In this study, the authors studied the analysis of the association between DFA and SCD.

METHODS

The investigators studied the predictive value of ultra-short-term heart rate fluctuations (1-minute electrocardiogram samples) with DFA at rest and during different stages of physical exertion for incident SCD among 2,794 participants undergoing clinical exercise testing in the prospective FINCAVAS (Finnish Cardiovascular Study). The novel key DFA measure, the short-scale scaling exponent computed with second-order detrending (DFA2 α1), was the main exposure variable. SCDs were defined by American Heart Association/European Society of Cardiology criteria using death certificates with written accounts of the events.

RESULTS

During a median follow-up of 8.3 years (Q1-Q3: 6.4-10.5), 83 SCDs occurred. DFA2 α1 measured at rest (but not in exercise) associated highly significantly with the risk of SCD, with 1-SD lower values associating with a 2.4-fold (Q1-Q3: 2.0-3.0) risk (P < 0.001). The results persisted when adjusting for other major risk factors for SCD, including age, cardiovascular morbidities, cardiorespiratory fitness, heart rate reduction, and left ventricular ejection fraction. Associations between conventional HRV parameters (measured at any stage of exercise or at rest) and SCD were substantially weaker and statistically nonsignificant after adjusting for other risk factors.

CONCLUSIONS

Ultra-short-term DFA2 α1, when measured at rest, is a powerful and independent predictor of SCD. The association between DFA2 α1 and SCD is modified by physical exertion.

The role of β-adrenergic stimulation in QT interval adaptation to heart rate during stress test

The adaptation lag of the QT interval after heart rate (HR) has been proposed as an arrhythmic risk marker. Most studies have quantified the QT adaptation lag in response to abrupt, step-like changes in HR induced by atrial pacing, in response to tilt test or during ambulatory recordings. Recent studies have introduced novel methods to quantify the QT adaptation lag to gradual, ramp-like HR changes in stress tests by evaluating the differences between the measured QT series and an estimated, memoryless QT series obtained from the instantaneous HR. These studies have observed the QT adaptation lag to progressively reduce when approaching the stress peak, with the underlying mechanisms being still unclear. This study analyzes the contribution of β-adrenergic stimulation to QT interval rate adaptation in response to gradual, ramp-like HR changes. We first quantify the QT adaptation lag in Coronary Artery Disease (CAD) patients undergoing stress test. To uncover the involved mechanisms, we use biophysically detailed computational models coupling descriptions of human ventricular electrophysiology and β-adrenergic signaling, from which we simulate ventricular action potentials and ECG signals. We characterize the adaptation of the simulated QT interval in response to the HR time series measured from each of the analyzed CAD patients. We show that, when the simulated ventricular tissue is subjected to a time-varying β-adrenergic stimulation pattern, with higher stimulation levels close to the stress peak, the simulated QT interval presents adaptation lags during exercise that are more similar to those measured from the patients than when subjected to constant β-adrenergic stimulation. During stress test recovery, constant and time-varying β-adrenergic stimulation patterns render similar adaptation lags, which are generally shorter than during exercise, in agreement with results from the patients. In conclusion, our findings support the role of time-varying β-adrenergic stimulation in contributing to QT interval adaptation to gradually increasing HR changes as those seen during the exercise phase of a stress test.

Evaluation of the QRS score for diagnosing coronary artery disease in women: A Finnish cardiovascular study

BACKGROUND

Exercise electrocardiography is a widely used diagnostic modality for diagnosing coronary artery disease. This method has been used for both sexes; however, its diagnostic accuracy in women is limited.

METHODS

The study analyzed 332 women participating in the Finnish Cardiovascular Study. Among 332 women, 125 with angiographically proven coronary artery disease (mean age 62.1 ± 9.5 years), 91 with a low likelihood of coronary artery disease (mean age 47.3 ± 13.5 years), and 116 without angiographically proven coronary artery disease (mean age 56.3 ± 9.9 years) were analyzed. The Q, R, S, and ST-segment changes and QRS score were determined by subtracting the Q, R, S, and ST-segment amplitudes immediately after the maximal exercise changes from their rest values (Δ). Receiver operating characteristic curve analysis was performed to evaluate the overall diagnostic performance of the parameters for predicting coronary artery disease.

RESULTS

The areas under the receiver operating characteristic curve between coronary artery disease and low likelihood of coronary artery disease groups for the QRS score and ΔSTV5, ΔQaVF, and ΔRaVF were 0.75, 0.73, 0.71, and 0.71, respectively. These areas were lower (0.62, 0.57, 0.60, and 0.60, respectively) between the groups with and without angiographically proven coronary artery disease. QRS score demonstrated the highest sensitivity at 80% specificity (61.5%) and the highest specificity at 80% sensitivity (57.6%).

CONCLUSIONS

This study suggests that the QRS and ST-segment depression have a moderate diagnostic ability to predict coronary artery disease in women. Q and R waves in lead aVF showed good diagnostic ability.

QT variability unrelated to RR variability during stress testing for identification of coronary artery disease

Stress test electrocardiogram (ECG) analysis is widely used for coronary artery disease (CAD) diagnosis despite its limited accuracy. Alterations in autonomic modulation of cardiac electrical activity have been reported in CAD patients during acute ischemia. We hypothesized that those alterations could be reflected in changes in ventricular repolarization dynamics during stress testing that could be measured through QT interval variability (QTV). However, QTV is largely dependent on RR interval variability (RRV), which might hinder intrinsic ventricular repolarization dynamics. In this study, we investigated whether different markers accounting for low-frequency (LF) oscillations of QTV unrelated to RRV during stress testing could be used to separate patients with and without CAD. Power spectral density of QTV unrelated to RRV was obtained based on time-frequency coherence estimation. Instantaneous LF power of QTV and QTV unrelated to RRV were obtained. LF power of QTV unrelated to RRV normalized by LF power of QTV was also studied. Stress test ECG of 100 patients were analysed. Patients referred to coronary angiography were classified into non-CAD or CAD group. LF oscillations in QTV did not show significant differences between CAD and non-CAD groups. However, LF oscillations in QTV unrelated to RRV were significantly higher in the CAD group as compared with the non-CAD group when measured during the first phases of exercise and last phases of recovery. ROC analysis of these indices revealed area under the curve values ranging from 61 to 73%. Binomial logistic regression analysis revealed LF power of QTV unrelated to RRV, both during the first phase of exercise and last phase of recovery, as independent predictors of CAD. In conclusion, this study highlights the importance of removing the influence of RRV when measuring QTV during stress testing for CAD identification and supports the added value of LF oscillations of QTV unrelated to RRV to diagnose CAD from the first minutes of exercise. This article is part of the theme issue 'Advanced computation in cardiovascular physiology: new challenges and opportunities'.

Examining the effect of mitochondrial DNA variants on blood pressure in two Finnish cohorts

High blood pressure (BP) is a major risk factor for many noncommunicable diseases. The effect of mitochondrial DNA single-nucleotide polymorphisms (mtSNPs) on BP is less known than that of nuclear SNPs. We investigated the mitochondrial genetic determinants of systolic, diastolic, and mean arterial BP. MtSNPs were determined from peripheral blood by sequencing or with genome-wide association study SNP arrays in two independent Finnish cohorts, the Young Finns Study and the Finnish Cardiovascular Study, respectively. In total, over 4200 individuals were included. The effects of individual common mtSNPs, with an additional focus on sex-specificity, and aggregates of rare mtSNPs grouped by mitochondrial genes were evaluated by meta-analysis of linear regression and a sequence kernel association test, respectively. We accounted for the predicted pathogenicity of the rare variants within protein-encoding and the tRNA regions. In the meta-analysis of 87 common mtSNPs, we did not observe significant associations with any of the BP traits. Sex-specific and rare-variant analyses did not pinpoint any significant associations either. Our results are in agreement with several previous studies suggesting that mtDNA variation does not have a significant role in the regulation of BP. Future studies might need to reconsider the mechanisms thought to link mtDNA with hypertension.

The ST segment depression pattern in asymptomatic peri-menopausal female athletes

Background

ST segment has not been well investigated in asymptomatic peri-menopausal female athletes, when the CV risk is higher.

Aims

The aims of the study is to investigate the prevalence of ST segment depression in peri-menopausal female athletes, divided in four age groups.

Methods

in a cohort of 6010 female athletes aged 45–65 years old, 161 subjects were selected for the presence of ST segment depression, revealed by maximal ergometric test. All athletes were also evaluated by physical examination and echocardiography. Inclusion criteria for ST segment depression were ST depression >0.5 mm respect to baseline and its depth was divided in 0.5 mm, 0.5–1 mm, 1–2 mm categories. Its behavior was classified in ascending, horizontal and descending and it was studied in relation to the age range (<51; 51–55; 56–60; >60).

Results

ST segment depression was mainly evident in inferolateral leads in all groups (63%, 70,3%, 71%, 63,6%, for <51; 51–55, 56–60 and 61–65 respectively) with horizontal pattern (52,2%, 59,5%, 57,8%, 63,6%) and 1–2 mm depth (43,5%, 46,7%, 60,6%), with the exception of the range 51–55, mainly showing a depth of 0,5-1 mm (45,9%). The older group showed increased SBP (137.5 mmHg, p = 0.007) and BMI (24.3, p = 0.093) values. Mitral prolapse was shown in 11,8% while 36,6% showed systolic flattening of mitral leaflets.

Conclusions

ST depression in asymptomatic menopausal female athletes is frequent and it is characterized by a specific presentation pattern. This is particularly important in the menopausal age when CV risk factors are more prevalent.

Association of Factor V Leiden With Subsequent Atherothrombotic Events: A GENIUS-CHD Study of Individual Participant Data

BACKGROUND

Studies examining the role of factor V Leiden among patients at higher risk of atherothrombotic events, such as those with established coronary heart disease (CHD), are lacking. Given that coagulation is involved in the thrombus formation stage on atherosclerotic plaque rupture, we hypothesized that factor V Leiden may be a stronger risk factor for atherothrombotic events in patients with established CHD.

METHODS

We performed an individual-level meta-analysis including 25 prospective studies (18 cohorts, 3 case-cohorts, 4 randomized trials) from the GENIUS-CHD (Genetics of Subsequent Coronary Heart Disease) consortium involving patients with established CHD at baseline. Participating studies genotyped factor V Leiden status and shared risk estimates for the outcomes of interest using a centrally developed statistical code with harmonized definitions across studies. Cox proportional hazards regression models were used to obtain age- and sex-adjusted estimates. The obtained estimates were pooled using fixed-effect meta-analysis. The primary outcome was composite of myocardial infarction and CHD death. Secondary outcomes included any stroke, ischemic stroke, coronary revascularization, cardiovascular mortality, and all-cause mortality.

RESULTS

The studies included 69 681 individuals of whom 3190 (4.6%) were either heterozygous or homozygous (n=47) carriers of factor V Leiden. Median follow-up per study ranged from 1.0 to 10.6 years. A total of 20 studies with 61 147 participants and 6849 events contributed to analyses of the primary outcome. Factor V Leiden was not associated with the combined outcome of myocardial infarction and CHD death (hazard ratio, 1.03 [95% CI, 0.92-1.16]; I2=28%; P-heterogeneity=0.12). Subgroup analysis according to baseline characteristics or strata of traditional cardiovascular risk factors did not show relevant differences. Similarly, risk estimates for the secondary outcomes including stroke, coronary revascularization, cardiovascular mortality, and all-cause mortality were also close to identity.

CONCLUSIONS

Factor V Leiden was not associated with increased risk of subsequent atherothrombotic events and mortality in high-risk participants with established and treated CHD. Routine assessment of factor V Leiden status is unlikely to improve atherothrombotic events risk stratification in this population.

Combination of low blood pressure response, low exercise capacity and slow heart rate recovery during an exercise test significantly increases mortality risk

Aims: We investigated the combination of low systolic blood pressure (SBP) response, low exercise capacity (EC) and slow heart rate recovery (HRR) during an exercise test in mortality prediction.Patients and methods: Our population consisted of 3456 patients from the Finnish Cardiovascular Study. A failure of SBP to increase >42 mmHg was defined as a low response. Low EC was defined as  < 8 metabolic equivalents. 1-minute HRR ≤18 bpm from maximum was defined as slow HRR.Results: During a median follow up of 10.0 years, 537 participants died. Reduced SBP response, low EC and slow HRR were independent predictors of all-cause and CV mortality (p < .001 for all). Patients with reduced SBP response, low EC and slow HRR had a very high mortality rate of 42.1% during follow up compared to only 4.5% of the patients without any of these risk factors. The hazard ratios for all-cause mortality in patients with one, two or three of the studied risk factors were 3.2, 6.0, and 10.6, respectively (p < .001 for all).Conclusion: The combination of reduced SBP response, low exercise capacity, and reduced HRR in an exercise test is associated with very high mortality and can be used in risk stratification.Key messagesThe combination of low blood pressure response, low exercise capacity and slow heart rate recovery in an exercise test is able to identify a group of patients in a very high mortality risk.These parameters are easily derived from an exercise test.All parameters are commonly available in clinical practice.

Cardiorespiratory fitness and heart rate recovery predict sudden cardiac death independent of ejection fraction

OBJECTIVE

To evaluate whether cardiorespiratory fitness (CRF) and heart rate recovery (HRR) associate with the risk of sudden cardiac death (SCD) independently of left ventricular ejection fraction (LVEF).

METHODS

The Finnish Cardiovascular Study is a prospective clinical study of patients referred to clinical exercise testing in 2001-2008 and follow-up until December 2013. Patients without pacemakers undergoing first maximal or submaximal exercise testing with cycle ergometer were included (n=3776). CRF in metabolic equivalents (METs) was estimated by achieving maximal work level. HRR was defined as the reduction in heart rate 1 min after maximal exertion. Adjudication of SCD was based on death certificates. LVEF was measured for clinical indications in 71.4% of the patients (n=2697).

RESULTS

Population mean age was 55.7 years (SD 13.1; 61% men). 98 SCDs were recorded during a median follow-up of 9.1 years (6.9-10.7). Mean CRF and HRR were 7.7 (SD 2.9) METs and 25 (SD 12) beats/min/min. Both CRF and HRR were associated with the risk of SCD in the entire study population (HR_CRF0.47 (0.37-0.59), p<0.001 and HR_HRR0.57 (0.48-0.67), p<0.001 with HR estimates corresponding to one SD increase in the exposure variables) and with CRF, HRR and LVEF in the same model (HR_CRF0.60 (0.45-0.79), p<0.001, HR_HRR0.65 (0.51-0.82), p<0.001) or adjusting additionally for all significant risk factors for SCD (LVEF, sex, creatinine level, history of myocardial infarction and atrial fibrillation, corrected QT interval) (HR_CRF0.69 (0.52-0.93), p<0.01, HR_HRR0.74 (0.58-0.95) p=0.02).

CONCLUSIONS

CRF and HRR are significantly associated with the risk of SCD regardless of LVEF.

Periodic repolarization dynamics as a risk predictor after myocardial infarction: Prospective validation study

BACKGROUND

Periodic repolarization dynamics (PRD) is a novel electrocardiographic phenomenon that refers to sympathetic activity-associated low-frequency modulations of cardiac repolarization. Retrospective post-myocardial infarction (MI) studies revealed that increased PRD indicates an increased risk of subsequent death.

OBJECTIVE

This is the first prospective study to validate PRD in patients after MI receiving up-to-date treatment.

METHODS

Four hundred fifty-five survivors of MI (age ≤80 years) in sinus rhythm were enrolled. PRD was assessed from 20-minute electrocardiographic recordings (2048 Hz) and prospectively dichotomized at 5.75 deg². Primary and secondary end points were total mortality and cardiovascular mortality, respectively. Multivariable analyses additionally included Global Registry of Acute Coronary Events score (dichotomized at >140), left ventricular ejection fraction (dichotomized at ≤35%), diabetes mellitus, and deceleration capacity of heart rate (dichotomized at ≤2.5 ms). The prognostic power of PRD was evaluated using receiver operating characteristic curve analysis, Cox regression analysis, and the integrated discrimination improvement index.

RESULTS

During a median follow-up period of 27 months, 47 patients died. Twenty-three of these deaths were classified as cardiovascular. Increased PRD was significantly associated with both end points, yielding areas under receiver operating characteristic curves of 69.3% (60.2%-77.8%) and 79.1% (69.7%-86.7%) for total mortality and cardiovascular mortality, respectively (P < .001 for both). In multivariable analysis, increased PRD indicated a 2.2- and 9.5-fold risk of total mortality and cardiovascular mortality (P = .024 and P = .003, respectively). Addition of PRD to the models significantly improved the integrated discrimination improvement index for total (P = .047) and cardiovascular mortality (P = .007).

CONCLUSION

PRD is a strong and independent predictor of total mortality and cardiovascular mortality in patients after MI treated with contemporary therapy.

The Duke treadmill score with bicycle ergometer: Exercise capacity is the most important predictor of cardiovascular mortality

Background

The Duke treadmill score, a widely used treadmill testing tool, is a weighted index combining exercise time or capacity, maximum ST-segment deviation and exercise-induced angina. No previous studies have investigated whether the Duke treadmill score and its individual components based on bicycle exercise testing predict cardiovascular death.

Design

Two populations with a standard bicycle testing were used: 3936 patients referred for exercise testing (2371 men, age 56 ± 13 years) from the Finnish Cardiovascular Study (FINCAVAS) and a population-based sample of 2683 men (age 53 ± 5.1 years) from the Kuopio Ischaemic Heart Disease study (KIHD).

Methods

Cox regression was applied for risk prediction with cardiovascular mortality as the primary endpoint.

Results

In FINCAVAS, during a median 6.3-year (interquartile range (IQR) 4.5–8.2) follow-up period, 180 patients (4.6%) experienced cardiovascular mortality. In KIHD, 562 patients (21.0%) died from cardiovascular causes during the median follow-up of 24.1 (IQR 18.0–26.2) years. The Duke treadmill score was associated with cardiovascular mortality in both populations (FINCAVAS, adjusted hazard ratio (HR) 3.15 for highest vs. lowest Duke treadmill score tertile, 95% confidence interval (CI) 1.83–5.42, P < 0.001; KIHD, adjusted HR 1.71, 95% CI 1.34–2.18, P < 0.001). However, after progressive adjustment for the Duke treadmill score components, the score was not associated with cardiovascular mortality in either study population, as exercise capacity in metabolic equivalents of task was the dominant harbinger of poor prognosis.

Conclusions

The Duke treadmill score is associated with cardiovascular mortality among patients who have undergone bicycle exercise testing, but metabolic equivalents of task, a component of the Duke treadmill score, proved to be a superior predictor.

Pro-opiomelanocortin and its Processing Enzymes Associate with Plaque Stability in Human Atherosclerosis - Tampere Vascular Study

α-melanocyte-stimulating hormone (α-MSH) is processed from pro-opiomelanocortin (POMC) and mediates anti-inflammatory actions in leukocytes. α-MSH also promotes macrophage reverse cholesterol transport by inducing ATP-binding cassette transporters ABCA1 and ABCG1. Here we investigated the regulation of POMC and α-MSH expression in atherosclerosis. First, transcript levels of POMC and its processing enzymes were analyzed in human arterial plaques (n = 68) and non-atherosclerotic controls (n = 24) as well as in whole blood samples from coronary artery disease patients (n = 55) and controls (n = 45) by microarray. POMC expression was increased in femoral plaques compared to control samples as well as in unstable advanced plaques. α-MSH-producing enzyme, carboxypeptidase E, was down-regulated, whereas prolylcarboxypeptidase, an enzyme inactivating α-MSH, was up-regulated in unstable plaques compared to stable plaques, suggesting a possible reduction in intraplaque α-MSH levels. Second, immunohistochemical analyses revealed the presence of α-MSH in atherosclerotic plaques and its localization in macrophages and other cell types. Lastly, supporting the role of α-MSH in reverse cholesterol transport, POMC expression correlated with ABCA1 and ABCG1 in human plaque and whole blood samples. In conclusion, α-MSH is expressed in atherosclerotic plaques and its processing enzymes associate with plaque stability, suggesting that measures to enhance the local bioavailability of α-MSH might protect against atherosclerosis.

Prediction of sudden and non-sudden cardiac death in post-infarction patients with reduced left ventricular ejection fraction by periodic repolarization dynamics: MADIT-II substudy

Aims

To test the value of Periodic Repolarization Dynamics (PRD), a recently validated electrocardiographic marker of sympathetic activity, as a novel approach to predict sudden cardiac death (SCD) and non-sudden cardiac death (N-SCD) and to improve identification of patients that profit from ICD-implantation.

Methods and results

We included 856 post-infarction patients with left-ventricular ejection fraction (LVEF) ≤30% of the MADIT-II trial in sinus rhythm. Of these, 507 and 348 patients were randomized to ICD or conventional treatment. PRD was assessed from multipolar 10-min baseline ECGs. Primary and secondary endpoints were total mortality, SCD and N-SCD. Multivariable analyses included treatment group, QRS-duration, New York Heart Association classification, blood-urea nitrogen, diabetes mellitus, beta-blocker therapy and LVEF. During follow-up of 20.4 months, 119 patients died (53 SCD and 36 N-SCD). On multivariable analyses, increased PRD was a significant predictor of mortality (standardized coefficient 1.37[1.19–1.59]; P < 0.001) and SCD (1.40 [1.13–1.75]; P = 0.003) but also predicted N-SCD (1.41[1.10–1.81]; P = 0.006). While increased PRD predicted SCD in conventionally treated patients (1.61[1.23–2.11]; P < 0.001), it was predictive of N-SCD (1.63[1.28–2.09]; P < 0.001) and adequate ICD-therapies (1.20[1.03–1.39]; P = 0.017) in ICD-treated patients. ICD-treatment substantially reduced mortality in the lowest three PRD-quartiles by 53% (P = 0.001). However, there was no effect in the highest PRD-quartile (mortality increase by 29%; P = 0.412; P < 0.001 for difference) as the reduction of SCD was compensated by an increase of N-SCD.

Conclusion

In post-infarction patients with impaired LVEF, PRD is a significant predictor of SCD and N-SCD. Assessment of PRD is a promising tool to identify post-MI patients with reduced LVEF who might benefit from intensified treatment.

Genetic Interactions with Age, Sex, Body Mass Index, and Hypertension in Relation to Atrial Fibrillation: The AFGen Consortium

It is unclear whether genetic markers interact with risk factors to influence atrial fibrillation (AF) risk. We performed genome-wide interaction analyses between genetic variants and age, sex, hypertension, and body mass index in the AFGen Consortium. Study-specific results were combined using meta-analysis (88,383 individuals of European descent, including 7,292 with AF). Variants with nominal interaction associations in the discovery analysis were tested for association in four independent studies (131,441 individuals, including 5,722 with AF). In the discovery analysis, the AF risk associated with the minor rs6817105 allele (at the PITX2 locus) was greater among subjects ≤ 65 years of age than among those > 65 years (interaction p-value = 4.0 × 10⁻⁵). The interaction p-value exceeded genome-wide significance in combined discovery and replication analyses (interaction p-value = 1.7 × 10⁻⁸). We observed one genome-wide significant interaction with body mass index and several suggestive interactions with age, sex, and body mass index in the discovery analysis. However, none was replicated in the independent sample. Our findings suggest that the pathogenesis of AF may differ according to age in individuals of European descent, but we did not observe evidence of statistically significant genetic interactions with sex, body mass index, or hypertension on AF risk.

Talin and vinculin are downregulated in atherosclerotic plaque; Tampere Vascular Study

BACKGROUND AND AIMS

Focal adhesions (FA) play an important role in the tissue remodeling and in the maintenance of tissue integrity and homeostasis. Talin and vinculin proteins are among the major constituents of FAs contributing to cellular well-being and intercellular communication.

METHODS

Microarray analysis (MA) and qRT-PCR low-density array were implemented to analyze talin-1, talin-2, meta-vinculin and vinculin gene expression in circulating blood and arterial plaque.

RESULTS

All analyzed genes were significantly and consistently downregulated in plaques (carotid, abdominal aortic and femoral regions) compared to left internal thoracic artery (LITA) control. The use of LITA samples as controls for arterial plaque samples was validated using immunohistochemistry by comparing LITA samples with healthy arterial samples from a cadaver. Even though the differences in expression levels between stable and unstable plaques were not statistically significant, we observed further negative tendency in the expression in unstable atherosclerotic plaques. The confocal tissue imaging revealed gradient of talin-1 expression in plaque with reduction close to the vessel lumen. Similar gradient was observed for talin-2 expression in LITA controls but was not detected in plaques. This suggests that impaired tissue mechanostability affects the tissue remodeling and healing capabilities leading to development of unstable plaques.

CONCLUSIONS

The central role of talin and vinculin in cell adhesions suggests that the disintegration of the tissue in atherosclerosis could be partially driven by downregulation of these genes, leading to loosening of cell-ECM interactions and remodeling of the tissue.

Kindlin 3 (FERMT3) is associated with unstable atherosclerotic plaques, anti-inflammatory type II macrophages and upregulation of beta-2 integrins in all major arterial beds

BACKGROUND

Kindlins (FERMT) are cytoplasmic proteins required for integrin (ITG) activation, leukocyte transmigration, platelet aggregation and thrombosis. Characterization of kindlins and their association with atherosclerotic plaques in human(s) is lacking.

METHODS AND RESULTS

Exploratory microarray (MA) was first performed followed by selective quantitative validation of robustly expressed genes with qRT-PCR low-density array (LDA). In LDA, ITGA1 (1.30-fold, p = 0.041) and ITGB3 (1.37-fold, p = 0.036) were upregulated in whole blood samples of patients with coronary artery disease (CAD) compared to healthy controls. In arterial plaques, both robustly expressed transcript variants of FERMT3 (MA: 5.90- and 3.4-fold; LDA: 3.99-fold, p < 0.0001 for all) and ITGB2 (MA: 4.81- and 4.92-fold; LDA: 5.29-fold, p < 0.0001 for all) were upregulated while FERMT2 was downregulated (MA: -1.61-fold; LDA: -2.88-fold, p < 0.0001 for both). The other integrins (ITGA1, ITGAV, ITGB3, ITGB5) were downregulated. All these results were replicated in at least one arterial bed. The latter FERMT3 transcript variant associated with unstable plaques (p = 0.0004). FERMT3 correlated with M2 macrophage markers and in hierarchical cluster analysis clustered with inflammatory and macrophage markers, while FERMT2 correlated with SMC-rich plaque markers and clustered with SMC markers. In confocal immunofluorescence analysis, FERMT3 protein colocalized with abundant CD68-positive cells of monocytic origin in the atherosclerotic plaques, while co-localization of FERMT3 with HHF35 indicative of smooth muscle cells was low.

CONCLUSIONS

Kindlin-3 (FERMT3) is upregulated in atherosclerotic, especially unstable plaques, mainly in cells of monocytic origin and of M2 type. Simultaneous upregulation of ITGB2 suggests a synergistic effect on leukocyte adherence and transmigration into the vessel wall.

Is the adiposity-associated FTO gene variant related to all-cause mortality independent of adiposity? Meta-analysis of data from 169,551 Caucasian adults

Previously, a single nucleotide polymorphism (SNP), rs9939609, in the FTO gene showed a much stronger association with all-cause mortality than expected from its association with body mass index (BMI), body fat mass index (FMI) and waist circumference (WC). This finding implies that the SNP has strong pleiotropic effects on adiposity and adiposity-independent pathological pathways that leads to increased mortality. To investigate this further, we conducted a meta-analysis of similar data from 34 longitudinal studies including 169,551 adult Caucasians among whom 27,100 died during follow-up. Linear regression showed that the minor allele of the FTO SNP was associated with greater BMI (n = 169,551; 0.32 kg m(-2) ; 95% CI 0.28-0.32, P < 1 × 10(-32) ), WC (n = 152,631; 0.76 cm; 0.68-0.84, P < 1 × 10(-32) ) and FMI (n = 48,192; 0.17 kg m(-2) ; 0.13-0.22, P = 1.0 × 10(-13) ). Cox proportional hazard regression analyses for mortality showed that the hazards ratio (HR) for the minor allele of the FTO SNPs was 1.02 (1.00-1.04, P = 0.097), but the apparent excess risk was eliminated after adjustment for BMI and WC (HR: 1.00; 0.98-1.03, P = 0.662) and for FMI (HR: 1.00; 0.96-1.04, P = 0.932). In conclusion, this study does not support that the FTO SNP is associated with all-cause mortality independently of the adiposity phenotypes.

A genome-wide expression quantitative trait loci analysis of proprotein convertase subtilisin/kexin enzymes identifies a novel regulatory gene variant for FURIN expression and blood pressure

Proprotein convertase subtilisin/kexin (PCSK) enzymes cleave and convert their immature substrates into biologically active forms. Polymorphisms in the PCSK genes have been reported to associate with human diseases and phenotypes, including hypercholesterolemia and blood pressure (BP), and targeting PCSKs is considered a promising future form of drug therapy. PCSK processing is readily induced upon upregulation of the enzyme, but the genetic factors contributing to PCSK expression have not been thoroughly characterized. To gain a comprehensive understanding of the genetic regulation of PCSK expression, we performed, for the first time, a genome-wide expression quantitative trait loci (eQTL) analysis using mRNA expression in >1400 human peripheral blood samples from the Cardiovascular Risk in Young Finns Study and ca. ten million single-nucleotide polymorphisms (SNPs). The expression data showed clear expression for FURIN, PCSK5, PCSK7 and MBTPS1 (membrane-bound transcription factor peptidase, site 1) mRNAs in virtually all tested samples. A discovery analysis demonstrated a genome-wide significant (p < 5 × 10(-8)) association with the selected PCSK probes for 1024 variants, which were located at ten independent loci. Of these loci, 5/10 could be confirmed to regulate PCSK expression in two additional and independent sample sets. Finally, a phenotypic analysis demonstrated that a novel cis-eQTL SNP rs4702 for FURIN is strongly associated with both diastolic (p = 0.012) and systolic (p = 0.035) BP levels, as well as peripheral vascular resistance (p = 0.003). These findings indicate that the expression of the PCSK enzymes is regulated by genetic factors, which have biological roles in health and disease.

Development and psychometric validation of the second version of the Coronary Artery Disease Education Questionnaire (CADE-Q II)

OBJECTIVES

To develop and psychometrically-validate a revised version of the Coronary Artery Disease Education Questionnaire (CADE-Q)--a tool to assess patients' knowledge about CAD in cardiac rehabilitation (CR).

METHODS

After a needs assessment, a literature review and focus group with CR experts, the revised questionnaire was developed. It underwent pilot-testing in 30 patients, which lead to further refinement. The questionnaire was then psychometrically-tested in 307 CR patients. Internal consistency was assessed using Cronbach's alpha, the dimensional structure through exploratory factor analysis, and criterion validity with regard to educational level.

RESULTS

Cronbach's alpha was 0.91. Criterion validity was supported by significant differences in mean scores by educational level (p<0.001). Factor analysis revealed four factors, which were internally-consistent (0.65-0.77), and well-defined by items. The mean total score was 64.2±18.1/93. Patients with a history of heart failure, cardiomyopathy and percutaneous coronary intervention (p<0.05) had significantly higher knowledge scores compared with patients without such a history. Knowledge about exercise and their medical condition was significantly higher than risk factors, nutrition and psychosocial risk.

CONCLUSIONS

The CADE-QII has good reliability and validity.

PRACTICAL IMPLICATIONS

This tool may be useful to assess CR participants' knowledge gaps, and to evaluate the efficacy of educational delivery in CR.

Effect of heart rate correction on pre- and post-exercise heart rate variability to predict risk of mortality-an experimental study on the FINCAVAS cohort

The non-linear inverse relationship between RR-intervals and heart rate (HR) contributes significantly to the heart rate variability (HRV) parameters and their performance in mortality prediction. To determine the level of influence HR exerts over HRV parameters' prognostic power, we studied the predictive performance for different HR levels by applying eight correction procedures, multiplying or dividing HRV parameters by the mean RR-interval (RRavg) to the power 0.5-16. Data collected from 1288 patients in The Finnish Cardiovascular Study (FINCAVAS), who satisfied the inclusion criteria, was used for the analyses. HRV parameters (RMSSD, VLF Power and LF Power) were calculated from 2-min segment in the rest phase before exercise and 2-min recovery period immediately after peak exercise. Area under the receiver operating characteristic curve (AUC) was used to determine the predictive performance for each parameter with and without HR corrections in rest and recovery phases. The division of HRV parameters by segment's RRavg to the power 2 (HRVDIV-2) showed the highest predictive performance under the rest phase (RMSSD: 0.67/0.66; VLF Power: 0.70/0.62; LF Power: 0.79/0.65; cardiac mortality/non-cardiac mortality) with minimum correlation to HR (r = -0.15 to 0.15). In the recovery phase, Kaplan-Meier (KM) survival analysis revealed good risk stratification capacity at HRVDIV-2 in both groups (cardiac and non-cardiac mortality). Although higher powers of correction (HRVDIV-4and HRVDIV-8) improved predictive performance during recovery, they induced an increased positive correlation to HR. Thus, we inferred that predictive capacity of HRV during rest and recovery is augmented when its dependence on HR is weakened by applying appropriate correction procedures.

Sympathetic activity-associated periodic repolarization dynamics predict mortality following myocardial infarction

BACKGROUND

Enhanced sympathetic activity at the ventricular myocardium can destabilize repolarization, increasing the risk of death. Sympathetic activity is known to cluster in low-frequency bursts; therefore, we hypothesized that sympathetic activity induces periodic low-frequency changes of repolarization. We developed a technique to assess the sympathetic effect on repolarization and identified periodic components in the low-frequency spectral range (≤0.1 Hz), which we termed periodic repolarization dynamics (PRD).

METHODS

We investigated the physiological properties of PRD in multiple experimental studies, including a swine model of steady-state ventilation (n=7) and human studies involving fixed atrial pacing (n=10), passive head-up tilt testing (n=11), low-intensity exercise testing (n=11), and beta blockade (n=10). We tested the prognostic power of PRD in 908 survivors of acute myocardial infarction (MI). Finally, we tested the predictive values of PRD and T-wave alternans (TWA) in 2,965 patients undergoing clinically indicated exercise testing.

RESULTS

PRD was not related to underlying respiratory activity (P<0.001) or heart-rate variability (P=0.002). Furthermore, PRD was enhanced by activation of the sympathetic nervous system, and pharmacological blockade of sympathetic nervous system activity suppressed PRD (P≤0.005 for both). Increased PRD was the strongest single risk predictor of 5-year total mortality (hazard ratio 4.75, 95% CI 2.94-7.66; P<0.001) after acute MI. In patients undergoing exercise testing, the predictive value of PRD was strong and complementary to that of TWA.

CONCLUSION

We have described and identified low-frequency rhythmic modulations of repolarization that are associated with sympathetic activity. Increased PRD can be used as a predictor of mortality in survivors of acute MI and patients undergoing exercise testing.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00196274.

FUNDING

This study was funded by Angewandte Klinische Forschung, University of Tübingen (252-1-0).

Association of Neuroimmune Guidance Cue Netrin-1 and Its Chemorepulsive Receptor UNC5B With Atherosclerotic Plaque Expression Signatures and Stability in Human(s)

Background—

Macrophage (MΦ) infiltration and smooth muscle cell (SMC) proliferation are hallmarks of atherosclerosis and unstable plaques. Neuroimmune guidance cue 1 (netrin-1 [NTN1]) plays a critical role controlling MΦ trafficking and SMC activation. Characterization of expression of NTN1 and its receptors and their association with plaque stability in human(s) is lacking.

Methods and Results—

The expression of NTN1 and its receptors did not differ in either whole blood or circulating monocytes from patients with coronary artery disease (n=55) compared with healthy controls (n=45). However, NTN1 was downregulated (−2.9-fold; P <0.0001) and UNC5B upregulated (2.2-fold; P <0.0001) in atherosclerotic plaques (n=68), whereas there were no differences in other NTN1 receptors compared with histologically normal controls (n=28). Increased UNC5B expression is associated with histologically more stable plaques ( P =0.011). NTN1 expression correlated positively with SMC markers and signatures and negatively with inflammatory markers and M1 and especially M2 signatures in the atherosclerotic plaques. UNC5B clustering correlated positively with inflammatory and MΦ markers. NTN1 protein colocalized with CD68-positive cells of monocytic origin and muscle-actin-specific-antibody (HHF3)-positive cells indicative of SMCs in the plaques and only with SMCs in the control samples. NTN1 protein was highly expressed in the intimal layer of the control vessels.

Conclusions—

Present findings provide support for the hypothesis that dysregulation of expression of NTN1 in SMCs and its chemorepulsive receptor UNC5B in macrophages are involved in the development of atherosclerosis and unstable plaques.

Genome-Wide Association Study Identifies 3 Genomic Loci Significantly Associated With Serum Levels of Homoarginine

Background—

Low serum levels of the amino acid derivative, homoarginine, have been associated with increased risk of total and cardiovascular mortality. Homoarginine deficiency may be related to renal and heart diseases, but the pathophysiologic role of homoarginine and the genetic regulation of its serum levels are largely unknown.

Methods and Results—

In 3041 patients of the Ludwigshafen Risk and Cardiovascular Health (LURIC) study referred for coronary angiography and 2102 participants of the Young Finns Study (YFS), we performed a genome-wide association study to identify genomic loci associated with homoarginine serum levels and tested for associations of identified single-nucleotide polymorphisms with mortality in LURIC. We found genome-wide significant associations with homoarginine serum levels on chromosome 2 at the carbamoyl phosphate synthetase I locus, on chromosome 5 at the alanine-glyoxylate aminotransferase 2 locus, and on chromosome 15 at the glycine amidinotransferase locus, as well as a suggestive association on chromosome 6 at the Homo sapiens mediator complex subunit 23 gene/arginase I locus. All loci harbor enzymes located in the mitochondrium are involved in arginine metabolism. The strongest association was observed for rs1153858 at the glycine amidinotransferase locus with a P value of 1.25E-45 in the combined analysis and has been replicated in both the Die Deutsche Diabetes Dialyse Studie (4D study) and the Graz Endocrine Causes of Hypertension (GECOH) study.

Conclusions—

In our genome-wide association study, we identified 3 chromosomal regions significantly associated with serum homoarginine and another region with suggestive association, providing novel insights into the genetic regulation of homoarginine.

Genome-wide association study pinpoints a new functional apolipoprotein B variant influencing oxidized low-density lipoprotein levels but not cardiovascular events: AtheroRemo Consortium

BACKGROUND

Oxidized low-density lipoprotein may be a key factor in the development of atherosclerosis. We performed a genome-wide association study on oxidized low-density lipoprotein and tested the impact of associated single-nucleotide polymorphisms (SNPs) on the risk factors of atherosclerosis and cardiovascular events.

METHODS AND RESULTS

A discovery genome-wide association study was performed on a population of young healthy white individuals (N=2080), and the SNPs associated with a P<5×10(-8) were replicated in 2 independent samples (A: N=2912; B: N=1326). Associations with cardiovascular endpoints were also assessed with 2 additional clinical cohorts (C: N=1118; and D: N=808). We found 328 SNPs associated with oxidized low-density lipoprotein. The genetic variant rs676210 (Pro2739Leu) in apolipoprotein B was the proxy SNP behind all associations (P=4.3×10(-136), effect size=13.2 U/L per allele). This association was replicated in the 2 independent samples (A and B, P=2.5×10(-47) and 1.1×10(-11), effect sizes=10.3 U/L and 7.8 U/L, respectively). In the meta-analyses of cohorts A, C, and D (excluding cohort B without angiographic data), the top SNP did not associate significantly with the age of onset of angiographically verified coronary artery disease (hazard ratio=1.00 [0.94-1.06] per allele), 3-vessel coronary artery disease (hazard ratio=1.03 [0.94-1.13]), or myocardial infarction (hazard ratio=1.04 [0.96-1.12]).

CONCLUSIONS

This novel genetic marker is an important factor regulating oxidized low-density lipoprotein levels but not a major genetic factor for the studied cardiovascular endpoints.

Comparison of standard versus orthogonal ECG leads for T-wave alternans identification

T-wave alternans (TWA), an electrophysiologic phenomenon associated with ventricular arrhythmias, is usually detected from selected ECG leads. TWA amplitude measured in the 12-standard and the 3-orthogonal (vectorcardiographic) leads were compared here to identify which lead system yields a more adequate detection of TWA as a noninvasive marker for cardiac vulnerability to ventricular arrhythmias. Our adaptive match filter (AMF) was applied to exercise ECG tracings from 58 patients with an implanted cardiac defibrillator, 29 of which had ventricular tachycardia or fibrillation during follow-up (cases), while the remaining 29 were used as controls. Two kinds of TWA indexes were considered, the single-lead indexes, defined as the mean TWA amplitude over each lead (MTWAA), and lead-system indexes, defined as the mean and the maximum MTWAA values over the standard leads and over the orthogonal leads. Significantly (P < 0.05) higher TWA in the cases versus controls was identified only occasionally by the single-lead indexes (odds ratio: 1.0-9.9, sensitivity: 24-76%, specificity: 76-86%), and consistently by the lead-system indexes (odds ratio: 4.5-8.3, sensitivity: 57-72%, specificity: 76%). The latter indexes also showed a significant correlation (0.65-0.83) between standard and orthogonal leads. Hence, when using the AMF, TWA should be detected in all leads of a system to compute the lead-system indexes, which provide a more reliable TWA identification than single-lead indexes, and a better discrimination of patients at increased risk of cardiac instability. The standard and the orthogonal leads can be considered equivalent for TWA identification, so that TWA analysis can be limited to one-lead system.

QRS-T morphology measured from exercise electrocardiogram as a predictor of cardiac mortality

AIMS

Total cosine R-to-T (TCRT) measured from the standard 12-lead electrocardiogram (ECG) reflects the spatial relationship between depolarization and repolarization wavefronts and a low TCRT value is a marker of poor prognosis. We tested the hypothesis that measurement of TCRT or QRS/T angle from exercise ECG would provide even more powerful prognostic information.

METHODS AND RESULTS

The prognostic significances of TCRT and QRS/T angle were assessed from exercise ECG recordings in 1297 patients [age 56 ± 13 years (mean ± SD), 67% males] undergoing a clinically indicated bicycle stress-test and the subsequent follow-up. During an average follow-up of 45 ± 12 months, 74 patients died (5.7%); 34 (2.6%) were cardiac deaths, and 24 (1.9%) were sudden cardiac deaths. Total cosine R-to-T and QRS/T angle exhibited a correlation with the RR intervals in the total cohort, but the individual responses were variable, e.g. median correlation of TCRT-RR was 0.89 with an inter-quartile range from 0.55 to 0.98. A reduced correlation of TCRT-RR during the recovery phase of exercise ECG predicted cardiac death [adjusted heart rate (HR) 3.5, 95% confidence interval (CI): 1.8-6.8, P= 0.001] similarly as the baseline TCRT measured from ECG at rest (adjusted HR 3.4, 95% CI: 1.4-8.1, P= 0.01). The poor correlation between the TCRT-RR both during the exercise and recovery was specifically related to a risk of sudden cardiac death (adjusted HR 6.2, 95% CI: 2.1-17.8, P< 0.001).

CONCLUSIONS

Loss of rate-adaptation of the spatial relationship between depolarization and repolarization wavefronts is a strong predictor of cardiac death, especially of sudden cardiac death.

Importance of regional specificity of T-wave alternans in assessing risk for cardiovascular mortality and sudden cardiac death during routine exercise testing

BACKGROUND

T-wave alternans (TWA) indicates increased risk for life-threatening arrhythmias. However, the regional distribution and predictivity of TWA among precordial leads remain unknown.

OBJECTIVE

We analyzed the magnitude and prognostic power of TWA in precordial leads separately and in combination during routine exercise stress testing in the largest TWA study conducted to date.

METHODS

The Finnish Cardiovascular Study (FINCAVAS) enrolled consecutive patients (n = 3,598, 56 ± 13 [mean ± standard deviation] years old, 2,164 men, 1,434 women) with a clinically indicated exercise test with bicycle ergometer. TWA was analyzed with the time-domain modified moving average method.

RESULTS

During a follow-up of 55 months (interquartile range of 35-78 months), 231 patients died; 97 deaths were cardiovascular, and 46 were classified as sudden cardiac deaths (SCDs). In Cox analysis after adjustment for common coronary risk factors, each 20-μV increase in TWA in leads V1-V6 multiplied the hazard ratio for cardiovascular mortality by 1.486-fold (95% confidence interval [CI] 1.127-1.952; P = .005). Each 20-μV increase in TWA in lead V5 amplified the hazard ratio for cardiovascular mortality by 1.545 (95% CI 1.150-2.108; P = .004) and for SCD by 1.576 (95% CI 1.041-2.412; P = .033).

CONCLUSIONS

Maximum TWA monitored from anterolateral precordial lead V5 is the strongest predictor of cardiovascular mortality and SCD during routine exercise testing in our analysis. Higher TWA values indicate greater cardiovascular mortality and SCD risk, supporting the concept that quantification of TWA should receive more attention.

IL-18 gene polymorphism, cardiovascular mortality and coronary artery disease

BACKGROUND

Interleukin 18(IL-18) is a pro-atherosclerotic cytokine. Elevated IL-18 levels and the genetic variation of the IL-18 have been previously linked with acute coronary events and cardiovascular mortality among patients with coronary artery disease (CAD). We studied the possible association between the IL-18 gene polymorphism and cardiovascular mortality during follow-up among Finnish patients who had undergone a clinical exercise stress test, in addition to the possible effect on the expression of angiography-verified CAD.

MATERIALS AND METHODS

A total of 2152 patients of the Finnish Cardiovascular Study (cohort study) were followed up for 6·3years and cardiovascular mortality was recorded. Angiography was performed on 461 patients. Genotyping of five common single nucleotide polymorphisms (SNPs) of the IL-18 gene was performed using the 5'nuclease assay for allelic discrimination with the ABI Prism 7900HT Sequence Detection System.

RESULTS

Among the study population, IL-18 gene polymorphism did not associate with cardiovascular mortality. According to adjusted binary regression analysis, the male carriers of one major haplotype (the only ones carrying the t allele of the +127 C/t SNP) had a lower occurrence rate for significant CAD defined as > 50% stenosis in at least one of the main branches of the coronary arteries (OR 0·495, 95% CI 0·862-0·284, P=0·041). No associations were observed among women. The sex-by-genotype interaction was significant (P=0·033).

CONCLUSIONS

The IL-18 gene was not found to associate significantly with mortality. Among patients who had coronary angiography, one major haplotype of the IL-18 gene has a gender-dependent different impact on the expression of CAD.

Value of leads V4R and CM5 in the detection of coronary artery disease during exercise electrocardiographic test

The usefulness of the right precordial unipolar leads and the value of the bipolar lead CM5 in the detection of coronary artery disease (CAD) with exercise electrocardiographic (ECG) test are not well documented. The objective of this study was to evaluate the diagnostic performance of leads V4R and CM5. The study population comprised 579 patients referred for a bicycle exercise ECG test in the Finnish Cardiovascular Study. Patients were divided into three groups: angiographically proven CAD (CAD, n = 255), no CAD by angiography (NoCAD, n = 126), and low likelihood of CAD (LLC, n = 198). The maximum ST-segment depression at peak exercise was used as a parameter, and the diagnostic accuracy of different leads was assessed by receiver operating characteristic (ROC) analysis. Sensitivity and specificity values at a cut-off criterion of -0.10 mV ST-segment, 1-mm ST depression, were determined. According to the results, incorporating lead V4R with the standard leads decreased the ROC area from 0.71 to 0.69 (comparison CAD versus LLC) and from 0.55 to 0.53 (comparison CAD versus NoCAD) and had no effect on sensitivity or specificity. Adding lead CM5 to the standard leads did not affect the ROC area but increased the sensitivity and decreased the specificity. In conclusion, the use of right precordial lead V4R along with the standard 12-lead system does not improve the performance of the exercise ECG in diagnosing CAD. Adding lead CM5 to the standard leads increases the sensitivity but does not change the overall diagnostic performance.

Impaired exercise capacity predicts sudden cardiac death in a low-risk population: enhanced specificity with heightened T-wave alternans

AIMS

Because sudden cardiac death (SCD) is due to cardiac electrical instability, we postulated that prediction of this mode of death by exercise capacity will be enhanced by combined assessment with T-wave alternans (TWA), an index of repolarization abnormality.

MATERIAL AND METHODS

The Finnish Cardiovascular Study enrolled consecutive patients (n=2,044) with a routine clinically indicated exercise test. Exercise capacity was measured in metabolic equivalents (METs) and TWA by time-domain modified moving average method.

RESULTS

During 47.2+/-12.8-month follow-up (mean+/-SD) 120 patients died; 58 were cardiovascular deaths, and 29 were SCD. In multivariate analysis after adjustment for sex, age, smoking, use of beta-blockers, as well as other common coronary risk factors, the relative risk of patients whose exercise capacity was depressed (MET < 8) was 8.8 (95% CI 2.0-38.9, P=0.004) for SCD. The combination of low exercise capacity (MET < 8) and elevated TWA (> or =65 microV) yielded relative risks for SCD of 36.1 (6.3-206.0, P<0.001), for cardiovascular mortality of 21.1 (6.7-66.2, P<0.001), and for all-cause mortality of 7.8 (3.5-17.4, P<0.001) over patients with neither factor.

CONCLUSIONS

Reduced exercise capacity, particularly in combination with heightened TWA, indicating enhanced cardiac electrical instability, powerfully predicts risk for SCD in patients referred for exercise testing.

Effect of common KCNE1 and SCN5A ion channel gene variants on T-wave alternans, a marker of cardiac repolarization, during clinical exercise stress test: the Finnish Cardiovascular Study

T-wave alternans (TWA) in electrocardiography (ECG) is a marker of cardiac repolarization, the molecular regulation of which is incompletely understood. High TWA and prolonged QT intervals are both associated with ventricular arrhythmias and sudden death. Therefore, we tested the hypothesis of whether the same mutations that influence the QT interval also affect TWA variation. We examined the effect of 3 ion channel gene single nucleotide polymorphisms (SNPs), rs1805127, rs727957 KCNE1, and rs1805124 SCN5A, on TWA during a clinical exercise test. A total of 2008 subjects from the Finnish Cardiovascular Study underwent an exercise test with online ECG recording. TWA was measured by using the time-domain, modified moving average method. Maximum values at rest, during maximal exercise, and during recovery were used as outcome measures in statistical analysis. Moreover, 4-year survival data were collected and ion channel SNPs were determined. TWA was lowest in subjects with the TT genotype of rs1805127 during all phases of the exercise test (RANOVA main effect for genotype, P = 0.018). The result remained significant after adjustment for age, existing coronary heart disease, and beta-blocker medication status (RANCOVA, P = 0.035). Of the polymorphisms studied, only rs1805127 had a significant association with mortality (P = 0.047). The most common G-C haplotype, formed by rs727957 and rs1805127, was associated with TWA (RANOVA, P = 0.007) but not with mortality. The rs1805124 polymorphism was not associated with TWA. The common KCNE1 gene variant rs1805127 is associated with TWA during an exercise test in a Finnish population, which provides additional evidence that KCNE1 genetics may influence cardiac repolarization and cardiovascular mortality.

Gender and effects of a common genetic variant in the NOS1 regulator NOS1AP on cardiac repolarization in 3761 individuals from two independent populations

BACKGROUND

A longer heart-rate corrected QT interval (QTc) is associated with increased risk of ventricular arrhythmias. Women have longer resting QTc and are more likely than men to develop drug-induced QT prolongation. Recent studies have shown association between resting QTc and a common variant (rs10494366) of the NOS1 regulator, NOS1AP. We investigated the association between rs10494366 in NOS1AP and QTc, and assessed gender-specific NOS1AP associations with QTc during rest and after exercise.

METHODS

We investigated the SNP associations with resting QTc in 919 women and 918 men from 504 representative families in the UK GRAPHIC study, and with QTc at rest and at 3 min recovery after exercise in 699 women and 1225 men referred for exercise testing in the Finnish FINCAVAS study.

RESULTS

In the GRAPHIC study the minor allele (G) of the NOS1AP SNP rs10494366 prolonged QTc by 4.59 ms (95% CI 2.77-6.40; P = 7.63/10(7)) in women, but only by 1.62 ms (95% CI -0.15 to 3.38; P = 0.073) in men (gender-SNP interaction term P = 0.025). In the FINCAVAS study the G allele significantly prolonged QTc in both women (P = 0.0063) and men (P = 0.0043) at 3 min recovery after exercise, but at rest an association was only seen in women (P = 0.020 excluding outliers).

CONCLUSIONS

A common NOS1AP variant prolongs QTc with a difference between genders. Further studies should aim to confirm this finding and to assess whether NOS1AP genotype influences the risk of drug-induced QT prolongation and risk of consequent arrhythmias.

The prognostic value of haemodynamic parameters in the recovery phase of an exercise test. The Finnish Cardiovascular Study

We tested the hypothesis that the change from the peak to recovery values of systolic arterial pressure (SAP recovery) and rate-pressure product (RPP recovery) can be used to predict all-cause and cardiovascular mortality, as well as sudden cardiac death (SCD) in patients referred to a clinical exercise stress test. As a part of the Finnish Cardiovascular Study (FINCAVAS), consecutive patients (n=2029; mean age+/-SD=57+/-13 years; 1290 men and 739 women) with a clinically indicated exercise test using a bicycle ergometer were included in the present study. Capacities of attenuated SAP recovery, RPP recovery and heart rate recovery (HRR) to stratify the risk of death were estimated. During a follow-up (mean+/-s.d.) of 47+/-13 months, 122 patients died; 58 of the deaths were cardiovascular and 33 were SCD. In Cox regression analysis after adjustment for the peak level of the variable under assessment, age, sex, use of beta-blockers, previous myocardial infarction and other common coronary risk factors, the hazard ratio of the continuous variable RPP recovery (in units 1000 mm Hg x b.p.m.) was 0.85 (95% CI: 0.73-0.98) for SCD, 0.87 (0.78-0.97) for cardiovascular mortality, and 0.87 (0.81 to 0.94) for all-cause mortality. SAP recovery was not a predictor of mortality. The relative risks of having HRR below 18 b.p.m., a widely used cutoff point, were as follows: for SCD 1.28 (0.59-2.81, ns), for cardiovascular mortality 2.39 (1.34-4.26) and for all-cause mortality 2.40 (1.61-3.58). In conclusion, as a readily available parameter, RPP recovery is a promising candidate for a prognostic marker.

Potassium channel KCNH2 K897T polymorphism and cardiac repolarization during exercise test: The Finnish Cardiovascular Study

OBJECTIVE

Cardiac repolarization is regulated, in part, by the KCNH2 gene, which encodes a rapidly activating component of the delayed rectifier potassium channel. The gene expresses a functional single nucleotide polymorphism, K897T, which changes the biophysical properties of the channel. The objective of this study was to evaluate whether this polymorphism influences two indices of repolarization--the QT interval and T-wave alternans (TWA)--during different phases of a physical exercise test.

MATERIAL AND METHODS

The cohort consisted of 1,975 patients undergoing an exercise test during which on-line electrocardiographic data were registered. Information on coronary risk factors and medication was recorded. The 2690A>C nucleotide variation in the KCNH2 gene corresponding to the K897T amino acid change was analysed after polymerase chain reaction with allele-specific TaqMan probes.

RESULTS

Among all subjects, the QTc intervals did not differ between the three genotype groups (p> or =0.31, RANOVA). Women with the CC genotype tended to have longer QT intervals during the exercise test, but the difference was statistically significant only at rest (p = 0.011, ANOVA). This difference was also detected when the analysis was adjusted for several factors influencing the QT interval. No statistically significant effects of the K897T polymorphism on TWA were observed among all subjects (p = 0.16, RANOVA), nor in men and women separately.

CONCLUSIONS

The K897T polymorphism of the KCNH2 gene may not be a major genetic determinant for the TWA, but the influence of the CC genotype on QT interval deserves further research among women.

[Epidemiology of acute coronary syndrome in Europe]

Epidemiological data concerning acute coronary syndromes in Europe are based on national registries, studies by the European Society of Cardiology within the framework of the EuroHeart Survey and on the study of European population sub-groups in large international cohorts. In this article, recently published studies will be reviewed, and the principal developments in different countries as well as the characteristics and particularities of the most recent epidemiological data will be highlighted. In Europe, the presentation of acute coronary syndromes (ACS) has evolved considerably over the last ten years. This evolution is characterized by a reduction in the proportion of acute coronary syndromes with ST-segment elevation (STEMI) and by ageing populations.