Diabetes, glucose tolerance, and the risk of sudden cardiac death

Background: Diabetes predisposes to sudden cardiac death (SCD). However, it is uncertain whether greater proportion of cardiac deaths are sudden among diabetes patients than other subjects. It is also unclear whether the risk of SCD is pronounced already early in the course of the disease. The relationship of impaired glucose tolerance (IGT) and SCD is scarcely documented. Methods: A general population cohort of 10594 middle-aged subjects (mean age 44 years, 52.6 % male, follow-up duration 35-41 years) was divided into diabetes patients (n = 82), subjects with IGT (n = 3806, plasma glucose = 9.58 mmol/l in one-hour glucose tolerance test), and controls (n = 6706). Results: Diabetes patients had an increased risk of SCD after adjustment confounders (hazard ratio 2.62, 95 % confidence interval 1.46-4.70, p = 0.001) but risk for non-sudden cardiac death was similarly increased and the proportion of SCD of cardiac deaths was not increased. The SCD risk persisted after exclusion of subjects with baseline cardiac disease or non-fatal cardiac events during the follow-up. Subjects with IGT were at increased risk for SCD (univariate hazard ratio 1.51; 95 % confidence interval 1.31-1.74; p <0.001) and also for non-sudden cardiac deaths and non-fatal cardiac events but adjustments for other risk factors attenuated these effects. Conclusions: Diabetes was associated with increased risk of SCD but also the risk of non-sudden cardiac death was similarly increased. The proportion of cardiac deaths being sudden in subjects with diabetes was not increased. The higher SCD risk in diabetes patients was independent of known cardiac disease at baseline or occurrence of nonfatal cardiac event during the follow-up.Peer reviewe

Risk of sudden cardiac death associated with QRS, QTc, and JTc intervals in the general population

BACKGROUND QRS duration and corrected QT (QTc) interval have been associated with sudden cardiac death (SCD), but no data are available on the significance of repolarization component (JTc interval) of the QTc interval as an independent risk marker in the general population. OBJECTIVE In this study, we sought to quantify the risk of SCD associated with QRS, QTc, and JTc intervals. METHODS This study was conducted using data from 3 population cohorts from different eras, comprising a total of 20,058 individuals. The follow-up period was limited to 10 years and age at baseline to 30-61 years. QRS duration and QT interval (Bazett's) were measured from standard 12-lead electrocardiograms at baseline. JTc interval was defined as QTc interval - QRS duration. Cox proportional hazards models that controlled for confounding clinical factors identified at baseline were used to estimate the relative risk of SCD. RESULTS During a mean period of 9.7 years, 207 SCDs occurred (1.1 per 1000 person-years). QRS duration was associated with a significantly increased risk of SCD in each cohort (pooled hazard ratio [HR] 1.030 per 1-ms increase; 95% confidence interval [CI] 1.017-1.043). The QTc interval had borderline to significant associations with SCD and varied among cohorts (pooled HR 1.007; 95% CI 1.001-1.012). JTc interval as a continuous variable was not associated with SCD (pooled HR 1.001; 95% CI 0.996-1.007). CONCLUSION Prolonged QRS durations and QTc intervals are associated with an increased risk of SCD. However, when the QTc interval is deconstructed into QRS and JTc intervals, the repolarization component (JTc) appears to have no independent prognostic value.Peer reviewe

Risk of sudden cardiac death associated with QRS, QTc, and JTc intervals in the general population

BackgroundQRS duration and corrected QT (QTc) interval have been associated with sudden cardiac death (SCD), but no data are available on the significance of repolarization component (JTc interval) of the QTc interval as an independent risk marker in the general population.ObjectiveIn this study, we sought to quantify the risk of SCD associated with QRS, QTc, and JTc intervals.MethodsThis study was conducted using data from 3 population cohorts from different eras, comprising a total of 20,058 individuals. The follow-up period was limited to 10 years and age at baseline to 30–61 years. QRS duration and QT interval (Bazett’s) were measured from standard 12-lead electrocardiograms at baseline. JTc interval was defined as QTc interval – QRS duration. Cox proportional hazards models that controlled for confounding clinical factors identified at baseline were used to estimate the relative risk of SCD.ResultsDuring a mean period of 9.7 years, 207 SCDs occurred (1.1 per 1000 person-years). QRS duration was associated with a significantly increased risk of SCD in each cohort (pooled hazard ratio [HR] 1.030 per 1-ms increase; 95% confidence interval [CI] 1.017–1.043). The QTc interval had borderline to significant associations with SCD and varied among cohorts (pooled HR 1.007; 95% CI 1.001–1.012). JTc interval as a continuous variable was not associated with SCD (pooled HR 1.001; 95% CI 0.996–1.007).ConclusionProlonged QRS durations and QTc intervals are associated with an increased risk of SCD. However, when the QTc interval is deconstructed into QRS and JTc intervals, the repolarization component (JTc) appears to have no independent prognostic value.</p

The role of electrocardiographic abnormalities, obesity, and diabetes in risk stratification for sudden cardiac death in the general population

Abstract The incidence of sudden cardiac death (SCDs) in the western countries is 50 – 100 in a population of 100,000. The most common disease causing SCDs is coronary heart disease. A large proportion of the victims are unaware of the underlying cardiac disease or only mildly symptomatic. Many SCDs could be prevented with therapies targeted to the underlying cardiac disease and with implantable cardioverter defibrillators. However, current protocols identify only patients at highest risk and only a minority of SCDs occur in this group. Thus, markers for identifying subjects at risk for SCD are needed. The aim of this thesis was to study the roles of abnormalities in the electrocardiogram (ECG), obesity, and diabetes in SCD risk stratification. The prevalence and prognostic significance of the location of QRS transition zone (the chest lead in the ECG in which R wave amplitude ≥ S wave amplitude) and abnormal P terminal force in lead V1 of the ECG were assessed. In addition, the value of ECG abnormalities in SCD risk stratification in subjects with different relative weights were studied. These topics were assessed in a cohort of 10,000 middle-aged Finnish subjects followed over 30 years from national registers. Delayed QRS transition (occurring at V4 or leftwards) occurred in 16.4% of subjects and a markedly delayed QRS transition (at V5 or leftwards) occurred in 1.3% of subjects. Delayed QRS transition was associated with an increased risk of death and SCD and the risk of SCD was over 1.5-fold among those with markedly delayed QRS transition. An abnormal PTF (≥ 0.04mm∙s) was present in 4.8% of subjects and a markedly abnormal PTF (≥ 0.06mm∙s) in 1.2% of subjects. A markedly abnormal PTF was associated with an almost 2-fold risk of death and atrial fibrillation, but it did not predict SCDs. Both obesity and diabetes were associated with an increased risk of SCD, but the proportion of SCDs of all cardiac deaths did not increase in subjects with either of these conditions. ECG abnormalities provided most value in SCD risk stratification among normal weight subjects with a low level of risk factors. Overall, these studies provide information on the predictive value of some ECG risk markers and cardiovascular risk factors. However, the definite role of these risk markers in predicting the risk of SCD in general population at an individual level remains indecisive.Tiivistelmä Sydänperäisten äkkikuolemien ilmaantuvuus länsimaissa on 50 – 100 tapausta 100000 ihmisen väestössä vuodessa. Suurin osa näistä kuolemista kohdistuu henkilöihin, joilla ei ole todettu sydänsairautta tai jotka ovat vähäoireisia. Yleisin sydänperäisen äkkikuoleman taustasairaus on sepelvaltimotauti. Näitä kuolemia voidaan ehkäistä sydänsairauksien hoidolla ja rytmihäiriötahdistimilla, mutta vain suurimman riskin potilaat tunnistetaan nykymenetelmin. Toimivia riskimarkkereita tarvitaan, jotta lisää potilaita saataisiin prevention piiriin. Tämän tutkimuksen tavoite oli tutkia 12-kytkentäisestä EKG:sta määritettävien QRS-transitioalueen (rintakytkentä, jossa R-aallon amplitudi ≥ S-aallon amplitudi) ja poikkeavan P terminal forcen (PTF) yleisyyttä ja yhteyttä sydänperäisiin äkkikuolemiin. Lisäksi tavoitteena oli tutkia lihavuuden ja diabeteksen vaikutusta sydänperäisen äkkikuoleman riskiin ja EKG-muutosten ennustearvoa eri painoisilla henkilöillä sydänperäisen äkkikuoleman riskiarviossa. Tutkimusaineistona käytettiin yli 10000:n keski-ikäisen suomalaisen väestökohorttia, jota seurattiin kansallisista rekistereistä. QRS-transitio tapahtui myöhään (V4:ssä tai siitä vasemmalle) 16.4 %:lla tutkituista ja huomattavan myöhään (V5:ssä tai siitä vasemmalle) 1.3 %:lla tutkituista. Myöhäinen QRS-transitio liittyi kuoleman ja sydänperäisen äkkikuoleman riskiin. Sydänperäisen äkkikuoleman riski oli yli 1.5-kertainen henkilöillä, joilla oli huomattavan myöhäinen QRS-transitio. Poikkeava PTF (≥ 0.04 mm∙s) todettiin 4.8 %:lla väestöstä ja huomattavan poikkeava PTF (≥ 0.06 mm∙s) 1.2 %:lla väestöstä. Huomattavan poikkeavaan PTF:en liittyi lähes kaksinkertainen kuoleman ja eteisvärinän riski, mutta ei äkkikuolemariskiä. Lihavuuteen ja diabetekseen liittyi kohonnut sydänperäisen äkkikuoleman riski. Toisaalta lihavilla ja diabeetikoilla myös ei-äkillisten sydänkuolemien riski oli suurentunut, eikä äkillisten kuolemien osuus sydänkuolemista korostunut. Sydänperäisen äkkikuoleman riskiin liitetyt EKG-muutokset paransivat riskiarviota eniten normaalipainoisilla henkilöillä, joilla oli vähemmän sydän- ja verisuonitautien riskitekijöitä. Kokonaisuutena nämä tutkimukset luovat uutta tietoa EKG-riskimarkkereista, lihavuudesta ja diabeteksesta sydänperäisen äkkikuoleman riskiarviossa. Näiden biomarkkereiden lopullinen rooli yksilötasolla perusväestössä vaatii kuitenkin vielä lisätutkimuksia