Electrocardiogram as a predictor of sudden cardiac death in middle-aged subjects without a known cardiac disease

Background: Abnormal 12 lead electrocardiogram (ECG) findings and proposing its ability for enhanced risk prediction, majority of the studies have been carried out with elderly populations with prior cardiovascular diseases. This study aims to denote the association of sudden cardiac death (SCD) and various abnormal ECG morphologies using middle-aged population without a known cardiac disease. Methods: In total, 9511 middle-aged subjects (mean age 42 +/- 8.2 years, 52% males) without a known cardiac disease were included in this study. Risk for SCD was assessed after 10 and 30-years of follow-up. Results: Abnormal ECG was present in 16.3% (N = 1548) of subjects. The incidence of SCD was distinctly higher among those with any ECG abnormality in 10 and 30-year follow-ups (1.7/1000 years vs. 0.6/1000 years, P 100', left ventricular hypertrophy, and T-wave inversions were the most significant independent ECG risk markers for 10-year SCD prediction with up to 3-fold risk for SCD. Those with ECG abnormalities had a 1.3-fold risk (95% CI 1.07-1.57, P - 0.007) for SCD in 30-year follow-up, whereas QRST-angle > 100 degrees, LVH, ER 0.1 mV and 0.2 mV were the strongest individual predictors. Subjects with multiple ECG abnormalities had up to 6.6-fold risk for SCD (P <0.001). Conclusion: Several ECG abnormalities are associated with the occurrence of early and late SCD events in the middle-age subjects without known history of cardiac disease. (C) 2018 The Authors. Published by Elsevier B.V.Peer reviewe

Waveform prototype-based feature learning for automatic detection of the early repolarization pattern in ECG signals

Objective: Our aim was to develop an automated detection method, for prescreening purposes, of early repolarization (ER) pattern with slur/notch configuration in electrocardiogram (ECG) signals using a waveform prototype-based feature vector for supervised classification. Approach: The feature vectors consist of fragments of the ECG signal where the ER pattern is located, instead of abstract descriptive variables of ECG waveforms. The tested classifiers included linear discriminant analysis, k-nearest neighbor algorithm, and support vector machine (SVM). Main results: SVM showed the best performance in Friedman tests in our test data including 5676 subjects representing 45408 leads. Accuracies of the different classifiers showed results well over 90%, indicating that the waveform prototype-based feature vector is an effective representation of the differences between ECG signals with and without the ER pattern. The accuracy of inferior ER was 92.74% and 92.21% for lateral ER. The sensitivity achieved was 91.80% and specificity was 92.73%. Significance: The algorithm presented here showed good performance results, indicating that it could be used as a prescreening tool of ER, and it provides an additional identification of critical cases based on the distances to the classifier decision boundary, which are close to the 0.1 mV threshold and are difficult to label.Peer reviewe

Electrocardiographic Risk Markers of Cardiac Death : Gender Differences in the General Population

Background Cardiac death is one of the leading causes of death and sudden cardiac death (SCD) is estimated to cause approximately 50% of cardiac deaths. Men have a higher cardiac mortality than women. Consequently, the mechanisms and risk markers of cardiac mortality are not as well defined in women as they are in men. Aim The aim of the study was to assess the prognostic value and possible gender differences of SCD risk markers of standard 12-lead electrocardiogram in three large general population samples. Methods The standard 12-lead electrocardiographic (ECG) markers were analyzed from three different Finnish general population samples including total of 20,310 subjects (49.9% women, mean age 44.8 +/- 8.7 years). The primary endpoint was cardiac death, and SCD and all-cause mortality were secondary endpoints. The interaction effect between women and men was assessed for each ECG variable. Results During the follow-up (7.7 +/- 1.2 years), a total of 883 deaths occurred (24.5% women, p 110 ms (p = 490 ms and T-wave inversions predicted SCD (p <0.047 and 0.033, respectively). In the interaction analysis, LVH (HR: 2.4; 95% CI: 1.2-4.9; p = 0.014) was stronger predictor of primary endpoint in women than in men. Conclusion Several standard ECG variables provide independent information on the risk of cardiac mortality in men but not in women. LVH and T-wave inversions predict SCD also in women.Peer reviewe

Impact of age and sex on the long-term prognosis associated with early repolarization in the general population

BACKGROUND Early repolarization (ER) has been linked to the risk of sudden cardiac death (SCD) in the general population, although controversy remains regarding risks across various subgroups. OBJECTIVE The purpose of this study was to investigate whether age and sex influence the prognostic significance of ER. METHODS We evaluated the 12-lead electrocardiograms of 6631 Finnish general population subjects age >= 30 years (mean age 50.1 +/- 13.9 years; 44.5% men) for the presence of ER (J-point elevation >= 0.1 mV in >= 2 inferior/lateral leads) and followed them for 24.4 +/- 10.3 years. We analyzed the association between ER and the risk of SCD, cardiac death, and ad-cause mortality in subgroups according to age (= 50 years) and sex. RESULTS ER was present in 367 of the 3305 subjects age = 50 years. ER was not associated with any of the endpoints in the entire study population. After adjusting for clinical factors, ER was associated with SCD (hazard ratio [HR] 1.88; 95% confidence interval [CI] 1.16-3.07) in subjects CONCLUSION ER is associated with SCD in subjects younger than 50 years, particularly in women, but not in subjects 50 years and older.Peer reviewe

Waveform prototype-based feature learning for automatic detection of the early repolarization pattern in ECG signals

Objective: Our aim was to develop an automated detection method, for prescreening purposes, of early repolarization (ER) pattern with slur/notch configuration in electrocardiogram (ECG) signals using a waveform prototype-based feature vector for supervised classification. Approach: The feature vectors consist of fragments of the ECG signal where the ER pattern is located, instead of abstract descriptive variables of ECG waveforms. The tested classifiers included linear discriminant analysis, k-nearest neighbor algorithm, and support vector machine (SVM). Main results: SVM showed the best performance in Friedman tests in our test data including 5676 subjects representing 45408 leads. Accuracies of the different classifiers showed results well over 90%, indicating that the waveform prototype-based feature vector is an effective representation of the differences between ECG signals with and without the ER pattern. The accuracy of inferior ER was 92.74% and 92.21% for lateral ER. The sensitivity achieved was 91.80% and specificity was 92.73%. Significance: The algorithm presented here showed good performance results, indicating that it could be used as a prescreening tool of ER, and it provides an additional identification of critical cases based on the distances to the classifier decision boundary, which are close to the 0.1 mV threshold and are difficult to label.Peer reviewe

Gender differences in prevalence and prognostic value of fragmented QRS complex

Background: Fragmented QRS (fQRS) on 12-lead electrocardiogram(ECG) is associated with scarred myocardium and adverse outcome. However, the data on gender differences in terms of its prevalence and prognostic value is sparse. The aim of this study was to evaluate whether gender differences in fQRS exist among subjects drawn from populations with different risk profiles. Methods: We analyzed fQRS from 12-lead ECG in 953 autopsy-confirmed victims of sudden cardiac death (SCD) (78% men; 67.0 +/- 11.4 yrs), 1900 coronary artery disease (CAD) patients with angiographically confirmed stenosis of >= 50% (70% men; 66.6 +/- 9.0 yrs, 43% with previous myocardial infarction [MI]), and in 10,904 adults drawn from the Finnish adult general population (52% men; 44.0 +/- 8.5 yrs). Results: Prevalence of fQRS was associated with older age, male sex and the history and severity of prior cardiac disease of subjects. Among the general population fQRS was more commonly found among men in comparison to women (20.5% vs. 14.8%, p <0.001). The prevalence of fQRS rose gradually along with the severity of prior cardiac disease in both genders, yet remained significantly higher in the male population: subjects with suspected or known cardiac disease (25.4% vs. 15.8% p <0.001), CAD patients without prior MI (39.9% vs. 26.4%, p <0.001), CAD patients with prior MI (42.9% vs. 31.2%, p <0.001), and victims of SCD (56.4% vs. 44.4%, p <0.001). Conclusions: The prevalence of QRS fragmentation varies in different populations. The fragmentation is clearly related to the underlying cardiac disease in both genders, however women seem to have significantly lower prevalence of fQRS in each patient population in comparison to men. (C) 2020 The Authors. Published by Elsevier Inc.Peer reviewe

Dynamics of cardiac repolarization during exercise:rate-dependence and prognostic significance

Abstract Based on experimental studies, heterogeneous ventricular repolarization has been suggested to predispose to the onset of life-threatening ventricular arrhythmias and subsequent studies in various patient populations have associated it with poor clinical outcome. The aim of this study was to assess the dynamics of ventricular repolarization from electrocardiogram (ECG) during a standard exercise stress test with techniques based on principal component analysis, and to investigate whether they would yield valuable prognostic information on cardiac mortality and sudden cardiac death. Exercise ECG recordings from 40 healthy men and women were analyzed in order to establish normal dynamics and rate-dependence for the spatial QRS/T angle and total cosine R to T (TCRT), which reflects the spatial deviation between the depolarization and repolarization wave-fronts. Subsequently, exercise ECG recordings from 20 patients with previous myocardial infarction (MI) were compared with 20 controls in order to assess the modulation of previous MI on the dynamics of TCRT. The prognostic value of abnormal dynamics and rate-dependence of TCRT and spatial QRS/T angle were assessed in 1,297 patients referred to a clinically indicated exercise stress test. The spatial QRS/T angle and TCRT were found to be significantly rate-dependent during both exercise and recovery periods as TCRT and the cosine of the spatial QRS/T angle decreased at higher heart rates (HR), indicating increase in the global heterogeneity of the ventricular repolarization. In the post-MI group, the dynamics of TCRT were impaired with a significantly lower rate-dependence in contrast to the healthy and control groups. In the study cohort, impaired rate-dependence of TCRT during both exercise and recovery periods was an independent predictor of cardiac and sudden cardiac death during the follow up of the study. Similarly, reduction of the area between the exercise and three-minute recovery TCRT/HR curves was associated with an increased risk of cardiac and sudden cardiac death. In conclusion, dynamics and rate-dependence of TCRT and spatial QRS/T angle are able to discriminate subjects with an increased risk of cardiac and sudden cardiac death. Reduced rate-dependence of TCRT during exercise and recovery periods, as well as decreased exercise-recovery hysteresis of TCRT, are significant predictors of cardiac and sudden cardiac death.Tiivistelmä Sydämen kammioiden poikkeavan palautumisen on kokeellisissa tutkimuksissa havaittu altistavan kammioperäisille rytmihäiriöille. Lisäksi, useat tutkimukset erilaisissa potilasaineistoissa ovat osoittaneet sen olevan yhteydessä heikkoon kliiniseen ennusteeseen. Tämän työn tarkoituksena oli analysoida sydämen kammioiden repolarisaation dynamiikkaa sydänsähkökäyrästä (EKG) rasituskokeen aikana pääkomponenttianalyysiin perustuvilla menetelmillä sekä tutkia, ennustavatko uudet muuttujat sydänperäistä kuolemaa tai sydänperäistä äkkikuolemaa. Neljänkymmenen terveen miehen ja naisen rasitus-EKG:t analysoitiin depolarisaatio- ja repolarisaatioaaltojen välistä avaruudellista kulmaa kuvaavan ’total cosine R to T’:n (TCRT) sekä kolmiulotteisen QRS/T-kulman dynamiikan sekä sykeriippuvuuden normaaliarvojen määrittämiseksi. Lisäksi, vertailtiin 20 sydäninfarktin sairastaneen sekä 20 kontrollipotilaan rasitusmittauksia aiemman infarktin TCRT:n dynamiikkaan sekä sykeriippuvuuteen aiheuttaman modulaation määrittämiseksi. Muuttujien poikkeavan dynamiikan ennustearvoa testattiin 1297 rasitus-EKG-mittaukseen lähetteen saaneella potilaalla. Sekä TCRT että avaruudellisen QRS/T-kulman kosini olivat molemmat erittäin sykeriippuvaisia sekä rasituksessa että palautumisessa. Molemmat muuttujat pienenivät sykkeen (HR) kasvaessa, osoittaen kammioiden repolarisaation heterogeenisyyden kasvua korkeammilla syketaajuuksilla. Sydäninfarktin sairastaneilla potilailla muuttujien dynamiikka ja sykeriippuvuus olivat heikentyneitä. Kohorttiaineistossa heikentynyt sykeriippuvuus sekä rasituksen että palautumisen aikana ennustivat myöhempää sydänperäistä kuolemaa sekä sydänperäistä äkkikuolemaa itsenäisesti. Vastaavasti, rasituksen ja kolmen minuutin palautumisen aikaisten TCRT/HR kuvaajien väliin jäävän pinta-alan pienentyminen oli yhteydessä korkeampaan sydänperäisen kuoleman sekä sydänperäisen äkkikuoleman riskiin. Kammioiden repolarisaation dynamiikkaa kuvaavat muuttujat pystyvät erottelemaan potilaat, joilla on korkeampi riski kokea sydänperäinen kuolema tai sydänperäinen äkkikuolema. Poikkeavan alhainen sykeriippuvuus rasituksen ja palautumisen aikana sekä alentunut rasituksen ja palautumisen välinen hystereesi olivat merkittäviä sydänperäisen kuoleman sekä sydänperäisen äkkikuoleman ennustajia

Feasible assessment of recovery and cardiovascular health:accuracy of nocturnal HR and HRV assessed via ring PPG in comparison to medical grade ECG

Abstract Objective: To validate the accuracy of the Oura ring in the quantification of resting heart rate (HR) and heart rate variability (HRV). Background: Wearable devices have become comfortable, lightweight, and technologically advanced for assessing health behavior. As an example, the novel Oura ring integrates daily physical activity and nocturnal cardiovascular measurements. Ring users can follow their autonomic nervous system responses to their daily behavior based on nightly changes in HR and HRV, and adjust their behavior accordingly after self-reflection. As wearable photoplethysmogram (PPG) can be disrupted by several confounding influences, it is crucial to demonstrate the accuracy of ring measurements. Approach: Nocturnal HR and HRV were assessed in 49 adults with simultaneous measurements from the Oura ring and the gold standard ECG measurement. Female and male participants with a wide age range (15—72 years) and physical activity status were included. Regression analysis between ECG and the ring outcomes was performed. Main results: Very high agreement between the ring and ECG was observed for nightly average HR and HRV (r2 = 0.996 and 0.980, respectively) with a mean bias of −0.63 bpm and −1.2 ms. High agreement was also observed across 5 min segments within individual nights in (r2 = 0.869 ± 0.098 and 0.765 ± 0.178 in HR and HRV, respectively). Significance: Present findings indicate high validity of the Oura ring in the assessment of nocturnal HR and HRV in healthy adults. The results show the utility of this miniaturised device as a lifestyle management tool in long-term settings. High quality PPG signal results prompt future studies utilizing ring PPG towards clinically relevant health outcomes