Association of early repolarization and sudden cardiac death during an acute coronary event

BACKGROUND

Electrocardiographic early repolarization (ER) pattern has been previously associated with arrhythmic mortality and with an increased risk of ventricular fibrillation. We hypothesized that there is an association between ER and sudden cardiac death (SCD) during an acute coronary event.

METHODS AND RESULTS

The present study included 432 consecutive victims of SCD because of acute coronary event and 532 survivors of such an event, in whom 12-lead ECGs recorded before and unrelated to the event could be evaluated. SCDs were verified by medicolegal autopsy to be because of acute coronary event. ER was defined as an elevation of the QRS-ST junction in at least 2 inferior or lateral leads, manifested as QRS notching or slurring. The prevalence of ER pattern ≥0.1 mV was more common in cases (62/432; 14.4%) than controls (42/532; 7.9%) (P=0.001). The victims of SCD were younger, were more commonly men and smokers, had lower body mass index, had elevated heart rate, had prolonged QRS complex, and had lower prevalence of history of prior cardiovascular disease than controls. After adjustments for baseline differences, the odds ratio for J waves without ST-segment elevation in the SCD group was 2.15 (95% CI, 1.20-3.85; P=0.01).

CONCLUSIONS

Higher prevalence of ER in a standard 12-lead ECG in victims of SCD than in survivors of an acute coronary event suggests that the presence of ER increases the vulnerability to fatal arrhythmia during acute myocardial ischemia and provides a plausible mechanistic link between this ECG pattern and higher arrhythmic mortality of middle-aged/elderly subjects.

Association of early repolarization and sudden cardiac death during an acute coronary event

BACKGROUND

Electrocardiographic early repolarization (ER) pattern has been previously associated with arrhythmic mortality and with an increased risk of ventricular fibrillation. We hypothesized that there is an association between ER and sudden cardiac death (SCD) during an acute coronary event.

METHODS AND RESULTS

The present study included 432 consecutive victims of SCD because of acute coronary event and 532 survivors of such an event, in whom 12-lead ECGs recorded before and unrelated to the event could be evaluated. SCDs were verified by medicolegal autopsy to be because of acute coronary event. ER was defined as an elevation of the QRS-ST junction in at least 2 inferior or lateral leads, manifested as QRS notching or slurring. The prevalence of ER pattern ≥0.1 mV was more common in cases (62/432; 14.4%) than controls (42/532; 7.9%) (P=0.001). The victims of SCD were younger, were more commonly men and smokers, had lower body mass index, had elevated heart rate, had prolonged QRS complex, and had lower prevalence of history of prior cardiovascular disease than controls. After adjustments for baseline differences, the odds ratio for J waves without ST-segment elevation in the SCD group was 2.15 (95% CI, 1.20-3.85; P=0.01).

CONCLUSIONS

Higher prevalence of ER in a standard 12-lead ECG in victims of SCD than in survivors of an acute coronary event suggests that the presence of ER increases the vulnerability to fatal arrhythmia during acute myocardial ischemia and provides a plausible mechanistic link between this ECG pattern and higher arrhythmic mortality of middle-aged/elderly subjects.

Prevalence and prognostic significance of T-wave inversions in right precordial leads of a 12-lead electrocardiogram in the middle-aged subjects

BACKGROUND

T-wave inversion in right precordial leads V(1) to V(3) is a relatively common finding in a 12-lead ECG of children and adolescents and is infrequently found also in healthy adults. However, this ECG pattern can also be the first presentation of arrhythmogenic right ventricular cardiomyopathy. The prevalence and prognostic significance of T-wave inversions in the middle-aged general population are not well known.

METHODS AND RESULTS

We evaluated 12-lead ECGs of 10 899 Finnish middle-aged subjects (52% men, mean age 44 ± 8.5 years) recorded between 1966 and 1972 for the presence of inverted T waves and followed the subjects for 30 ± 11 years. Primary end points were all-cause mortality, cardiac mortality, and arrhythmic death. T-wave inversions in right precordial leads V(1) to V(3) were present in 54 (0.5%) of the subjects. In addition, 76 (0.7%) of the subjects had inverted T waves present only in leads other than V(1) to V(3). Right precordial T-wave inversions did not predict increased mortality (not significant for all end points). However, inverted T waves in leads other than V(1) to V(3) were associated with an increased risk of cardiac and arrhythmic death (P<0.001 for both).

CONCLUSIONS

T-wave inversions in right precordial leads are relatively rare in the general population, and are not associated with adverse outcome. Increased mortality risk associated with inverted T waves in other leads may reflect the presence of an underlying structural heart disease.

Intraventricular Conduction Delay in a Standard 12-Lead Electrocardiogram as a Predictor of Mortality in the General Population

Background—

Prolonged duration of QRS complex in a 12-lead ECG is associated with adverse prognosis in patients with cardiac disease, but its significance is not well established in the general population. In particular, there is a paucity of data on the prognostic significance of nonspecific intraventricular conduction delay in apparently healthy subjects.

Methods and Results—

We evaluated the 12-lead ECGs of 10 899 Finnish middle-aged subjects from the general population (52% of whom were men; mean age 44±8.5 years) between 1966 and 1972 and followed them for 30±11 years. Primary end points were all-cause mortality, cardiac mortality, and arrhythmic death. Prolonged QRS duration was defined as QRS ≥110 ms and intraventricular conduction delay as QRS ≥110 ms, without the criteria of complete or incomplete bundle-branch block. QRS duration ≥110 ms was present in 1.3% (n=147) and intraventricular conduction delay in 0.6% (n=67) of the subjects. Prolonged QRS duration predicted all-cause mortality (multivariate-adjusted relative risk [RR] 1.48; 95% confidence interval [CI] 1.22–1.81; P <0.001), cardiac mortality (RR 1.94; CI 1.44–2.63; P <0.001), and sudden arrhythmic death (RR 2.14; CI 1.38–3.33; P =0.002). Subjects with intraventricular conduction delay had increased all-cause mortality (RR 2.01; CI 1.52–2.66; P <0.001), increased cardiac mortality (RR 2.53; CI 1.64–3.90; P <0.001), and an elevated risk of arrhythmic death (RR 3.11; CI 1.74–5.54; P =0.001). Left bundle-branch block also weakly predicted arrhythmic death ( P =0.04), but right bundle-branch block was not associated with increased mortality.

Conclusions—

Prolonged QRS duration in a standard 12-lead ECG is associated with increased mortality in a general population, with intraventricular conduction delay being most strongly associated with an increased risk of arrhythmic death.

Safety of serial MRI in patients with implantable cardioverter defibrillators

OBJECTIVE

While patients with cardiac implantable electronic devices could benefit from magnetic resonance (MR) imaging, the presence of such devices has been designated as an absolute contraindication to MR. Although scanning algorithms are proposed for cardiac implantable electronic devices, their safety remains uncertain. To address this issue, the safety of serial cardiac MR scans was evaluated in patients with implantable cardioverter defibrillators (ICDs).

METHODS

Three serial cardiac MR scans were prospectively performed at 1.5 T on 10 patients (9 men) of median age 56 years (range 51-68) with ICDs. ICD interrogation was performed before and after the MR scan and at a follow-up of median 370 days (range 274-723). Image quality was also assessed.

RESULTS

In all patients MR scanning occurred without complications. There were no differences between pre- and post-MR pacing capture threshold, pacing lead or high voltage lead impedance, or battery voltage values. During follow-up there were no occurrences of ICD dysfunction. Although most patients had image artifacts, the studies were generally diagnostic regarding left ventricular function and wall motion. Delayed enhancement imaging was of good quality for inferior wall and inferolateral infarcts, but ICD artifacts often affected the imaging of anterior wall infarcts.

CONCLUSION

Serial MR scans at 1.5 T in patients with ICDs, when carefully performed in a monitored setting, have no adverse effects on either patient or device. When required, single or multiple MR scans at 1.5 T may therefore be considered for clinical diagnostic purposes in these patients.

Identification of a sudden cardiac death susceptibility locus at 2q24.2 through genome-wide association in European ancestry individuals

Sudden cardiac death (SCD) continues to be one of the leading causes of mortality worldwide, with an annual incidence estimated at 250,000–300,000 in the United States and with the vast majority occurring in the setting of coronary disease. We performed a genome-wide association meta-analysis in 1,283 SCD cases and >20,000 control individuals of European ancestry from 5 studies, with follow-up genotyping in up to 3,119 SCD cases and 11,146 controls from 11 European ancestry studies, and identify the BAZ2B locus as associated with SCD (P = 1.8×10⁻¹⁰). The risk allele, while ancestral, has a frequency of ∼1.4%, suggesting strong negative selection and increases risk for SCD by 1.92–fold per allele (95% CI 1.57–2.34). We also tested the role of 49 SNPs previously implicated in modulating electrocardiographic traits (QRS, QT, and RR intervals). Consistent with epidemiological studies showing increased risk of SCD with prolonged QRS/QT intervals, the interval-prolonging alleles are in aggregate associated with increased risk for SCD (P = 0.006).

Family studies have clearly demonstrated a role for genes in modifying risk for sudden cardiac death (SCD), however genetic studies have been limited by available samples. Here we have assembled over 4,400 SCD cases with >30,000 controls, all of European ancestry, and utilize a two-stage study design. In the first stage, we conducted an unbiased genome-wide scan in 1,283 SCD cases and >20,000 controls, and then performed follow-up genotyping in the remainder of the samples. We demonstrate strong association to a region of the genome not previously implicated in SCD, the BAZ2B locus, which contains 3 genes not previously known to play a role in cardiac biology. In addition, we used the genome-wide scan data to test a focused hypothesis that genetic variants that modulate ECG traits associated with SCD (QT, QRS, and RR intervals) also modify risk for SCD, and we demonstrate that QT- and QRS-prolonging alleles are, as a group, associated with increased risk of SCD. Taken together, these findings begin to elucidate the genetic contribution to SCD susceptibility and provide important targets for functional studies to investigate the etiology and pathogenesis of SCD.

Early repolarization: electrocardiographic phenotypes associated with favorable long-term outcome

BACKGROUND

Early repolarization (ER) in inferior/lateral leads of standard ECGs increases the risk of arrhythmic death. We tested the hypothesis that variations in the ST-segment characteristics after the ER waveforms may have prognostic importance.

METHODS AND RESULTS

ST segments after ER were classified as horizontal/descending or rapidly ascending/upsloping on the basis of observations from 2 independent samples of young healthy athletes from Finland (n=62) and the United States (n=503), where ascending type was the dominant and common form of ER. Early repolarization was present in 27/62 (44%) of the Finnish athletes and 151/503 (30%) of the US athletes, and all but 1 of the Finnish (96%) and 91/107 (85%) of US athletes had an ascending/upsloping ST variant after ER. Subsequently, ECGs from a general population of 10 864 middle-aged subjects were analyzed to assess the prognostic modulation of ER-associated risk by ST-segment variations. Subjects with ER ≥0.1 mV and horizontal/descending ST variant (n=412) had an increased hazard ratio of arrhythmic death (relative risk 1.43; 95% confidence interval 1.05 to 1.94). When modeled for higher amplitude ER (>0.2 mV) in inferior leads and horizontal/descending ST-segment variant, the hazard ratio of arrhythmic death increased to 3.14 (95% confidence interval 1.56 to 6.30). However, in subjects with ascending ST variant, the relative risk for arrhythmic death was not increased (0.89; 95% confidence interval 0.52 to 1.55).

CONCLUSIONS

ST-segment morphology variants associated with ER separates subjects with and without an increased risk of arrhythmic death in middle-aged subjects. Rapidly ascending ST segments after the J-point, the dominant ST pattern in healthy athletes, seems to be a benign variant of ER.

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.

Inferolateral early repolarization in athletes

PURPOSE

Early repolarization (ER) has been considered a common benign ECG pattern among young athletes. In contrast, an inferolateral early repolarization pattern has been associated with an increased risk for sudden cardiac death (SCD). The aim of the study was to assess the prevalence of inferolateral ER among young collegiate athletes and to describe the characteristics associated to the pattern.

METHODS

We analyzed ECGs from 503 athletes (51% males; age range, 17-24). Information on gender, body weight, race, sport, and family history of SCD was collected. ER was defined as a slow deflection of the down slope of the R wave (≥0.1 mV) or positive wave at J point (≥0.1 mV) in two consecutive inferior or in lateral leads. Additionally, we included voltage measurements according to the Sokolow-Lyon criteria and RR interval measurement.

RESULTS

The prevalence of ER was 30% (inferior, 20%; lateral, 21%; both, 11%). Male gender (59% vs. 48%, p = 0.019), left ventricular hypertrophy (LVH) voltage (39% vs. 12%, p < 0.001) was significantly associated with the ER pattern. In addition, there was a trend towards longer RR interval in the inferior ER group (p = 0.06) and there were slightly more African-Americans with ER compared to non-African-American (34% vs. 28%, p = 0.22). Among females (p = 0.039) and African-Americans (p = NS), the association of LVH to ER was not as strong.

CONCLUSION

ER is a common finding among young athletes. The ECG marker of LVH is the dominant shared characteristic among the athletes with ER, along with male gender and a trend to greater prevalence among African-American athletes.

Predictors of long-term risk for heart failure hospitalization after acute myocardial infarction

BACKGROUND

Data on the value of baseline brain natriuretic peptide (BNP) and autonomic markers in predicting heart failure (HF) hospitalization after an acute myocardial infarction (AMI) are limited.

METHODS

A consecutive series of patients with AMI without a previous history of HF (n = 569) were followed up for 8 years. At baseline, the patients had a blood sample for determination of BNP, a 24-hour Holter recording for evaluating heart rate variability (HRV) and heart rate turbulence (HRT), and an assessment of baroreflex sensitivity (BRS) using phenylephrine test.

RESULTS

During the follow-up, 79 (14%) patients were hospitalized due to HF. Increased baseline BNP, decreased HRV, HRT, and BRS had a significant association with HF hospitalization in univariate comparisons (P < 0.001 for all). After adjusting with all the relevant clinical parameters, BNP, HRV, and HRT still significantly predicted HF hospitalization (P < 0.001 for BNP and for the short-term scaling exponent alpha(1), P < 0.01 for turbulence slope). In the receiver operator characteristics curve analysis, the area under the curve for BNP was 0.77, for the short-term scaling exponent alpha(1) 0.69, for turbulence slope 0.71, and for BNP/standard deviation of all N-N intervals ratio 0.80.

CONCLUSION

Baseline increased BNP and impaired autonomic function after AMI yield significant information on the long-term risk for HF hospitalization.

Hundreds of variants clustered in genomic loci and biological pathways affect human height

Most common human traits and diseases have a polygenic pattern of inheritance: DNA sequence variants at many genetic loci influence the phenotype. Genome-wide association (GWA) studies have identified more than 600 variants associated with human traits, but these typically explain small fractions of phenotypic variation, raising questions about the use of further studies. Here, using 183,727 individuals, we show that hundreds of genetic variants, in at least 180 loci, influence adult height, a highly heritable and classic polygenic trait. The large number of loci reveals patterns with important implications for genetic studies of common human diseases and traits. First, the 180 loci are not random, but instead are enriched for genes that are connected in biological pathways (P = 0.016) and that underlie skeletal growth defects (P < 0.001). Second, the likely causal gene is often located near the most strongly associated variant: in 13 of 21 loci containing a known skeletal growth gene, that gene was closest to the associated variant. Third, at least 19 loci have multiple independently associated variants, suggesting that allelic heterogeneity is a frequent feature of polygenic traits, that comprehensive explorations of already-discovered loci should discover additional variants and that an appreciable fraction of associated loci may have been identified. Fourth, associated variants are enriched for likely functional effects on genes, being over-represented among variants that alter amino-acid structure of proteins and expression levels of nearby genes. Our data explain approximately 10% of the phenotypic variation in height, and we estimate that unidentified common variants of similar effect sizes would increase this figure to approximately 16% of phenotypic variation (approximately 20% of heritable variation). Although additional approaches are needed to dissect the genetic architecture of polygenic human traits fully, our findings indicate that GWA studies can identify large numbers of loci that implicate biologically relevant genes and pathways.

Sudden cardiac death after myocardial infarction in patients with type 2 diabetes

BACKGROUND

Type 2 diabetes mellitus is a well-established risk factor for atherosclerosis, but its contribution to sudden cardiac death (SCD) risk after myocardial infarction (MI) is not well defined.

OBJECTIVE

The purpose of this study was to compare the incidence and time-dependent risk of SCD in diabetic patients versus nondiabetic patients during 5-year follow-up after acute MI.

METHODS

A total of 3,276 patients were enrolled at the time of acute MI between 1996 and 2005. Mean age at entry was 60 ± 11 years, and the cohort was followed until 2009. At entry into the study, diabetes was present in 629 (19.2%) patients. The primary endpoint was SCD, and the secondary endpoints were non-SCD and all-cause mortality.

RESULTS

Among diabetic patients, the incidence of SCD was higher (5.9%) than in nondiabetic patients (1.7%), with a hazard ratio (HR) of 3.8 (95% confidence interval [CI] 2.4-5.8; P <.001) and adjusted HR of 2.3 (95% CI 1.4-3.8; P <.01). In diabetic patients with left ventricular ejection fraction >35%, the incidence of SCD was nearly identical to that of nondiabetic patients with ventricular ejection fraction ≤35% (4.1% vs 4.9%; P = .48). An excess in the incidence of non-SCD began to appear among diabetic patients within the first 6 months of follow-up (P <.001) but not in the incidence of SCD (P = .09). The excess in SCD among diabetic patients began to appear more than 6 months after the index event.

CONCLUSION

Patients with type 2 diabetes are at higher risk for SCD after MI than are nondiabetic patients. The incidence of SCD in post-MI type 2 diabetic patients with left ventricular ejection fraction >35% is equal to that of nondiabetic patients with left ventricular ejection fraction <35%.

Long-term outcome associated with early repolarization on electrocardiography

BACKGROUND

Early repolarization, which is characterized by an elevation of the QRS-ST junction (J point) in leads other than V(1) through V(3) on 12-lead electrocardiography, has been associated with vulnerability to ventricular fibrillation, but little is known about the prognostic significance of this pattern in the general population.

METHODS

We assessed the prevalence and prognostic significance of early repolarization on 12-lead electrocardiography in a community-based general population of 10,864 middle-aged subjects (mean [+/-SD] age, 44+/-8 years). The primary end point was death from cardiac causes, and secondary end points were death from any cause and death from arrhythmia during a mean follow-up of 30+/-11 years. Early repolarization was stratified according to the degree of J-point elevation (> or = 0.1 mV or > 0.2 mV) in either inferior or lateral leads.

RESULTS

The early-repolarization pattern of 0.1 mV or more was present in 630 subjects (5.8%): 384 (3.5%) in inferior leads and 262 (2.4%) in lateral leads, with elevations in both leads in 16 subjects (0.1%). J-point elevation of at least 0.1 mV in inferior leads was associated with an increased risk of death from cardiac causes (adjusted relative risk, 1.28; 95% confidence interval [CI], 1.04 to 1.59; P=0.03); 36 subjects (0.3%) with J-point elevation of more than 0.2 mV in inferior leads had a markedly elevated risk of death from cardiac causes (adjusted relative risk, 2.98; 95% CI, 1.85 to 4.92; P<0.001) and from arrhythmia (adjusted relative risk, 2.92; 95% CI, 1.45 to 5.89; P=0.01). Other electrocardiographic risk markers, such as a prolonged QT interval corrected for heart rate (P=0.03) and left ventricular hypertrophy (P=0.004), were weaker predictors of the primary end point.

CONCLUSIONS

An early-repolarization pattern in the inferior leads of a standard electrocardiogram is associated with an increased risk of death from cardiac causes in middle-aged subjects.

Genetic modulation of brugada syndrome by a common polymorphism

BACKGROUND

Brugada syndrome predisposes some subjects to ventricular tachyarrhythmias and sudden cardiac death. Mutations in SCN5A gene have been associated with approximately 25% of Brugada syndrome patients. A common variant in SCN5A, H558R has shown to improve sodium channel activity in mutated channels. We studied whether common variant H558R has any clinical implications in the phenotype of Brugada syndrome.

METHODS

Our study population consisted of Brugada syndrome subjects 75 with SCN5A mutation and 92 without SCN5A mutation. Their mean age was 39 +/- 15 and 42 +/- 17 years, and 65% and 86% were male, respectively. We measured PR-, QRS-, QTc-intervals from leads II and V2 of the 12-lead ECG. We also evaluated J-point amplitude from lead V2 and R'/S ratio from lead aVR (the "aVR sign"). The H558R (A-->G) genotype was detected with direct sequencing of the SCN5A gene.

RESULTS

The AA genotype carriers had longer QRS duration in lead II (P = 0.017) and higher J-point elevation in lead V2 (P = 0.013), higher "aVR sign" (P = 0.005) and a trend toward more subjects with symptoms (P = 0.067) than G allele carriers. None of the results were significant in Brugada syndrome subjects without SCN5A mutation.

CONCLUSION

The common variant H558R seems to be a genetic modulator of Brugada syndrome among carriers of a SCN5A mutation, in whom the presence of the less common allele G improves the ECG characteristics and clinical phenotype.

Differences in 12-lead electrocardiogram between symptomatic and asymptomatic Brugada syndrome patients

INTRODUCTION

Brugada syndrome (BrS) is an inherited disorder that predisposes some subjects to sudden cardiac death (SCD). It is not well established which BrS patients are at risk of severe arrhythmias. Our aim was to study whether standard 12-lead electrocardiogram (ECG) would give useful information for this purpose.

METHODS

This study included 200 BrS probands (142 male, 62%; mean age 42 +/- 16 years). Symptoms related to BrS were defined as syncope, documented ventricular tachyarrhythmia, or SCD. We determined PR, QRS, QTc, T(peak), and T(end) interval from leads II and V(2) and QRS from lead V(5), R'/S ratio from lead aVR (aVR sign), QRS axis, and J-point elevation amplitude from right precordial leads from the baseline ECGs.

RESULTS

Sixty-six subjects (33%) had experienced symptoms related to BrS. The only significant difference between the symptomatic and asymptomatic BrS subjects was the QRS duration measured from lead II or lead V(2), for example, the mean QRS in V(2) was 115 +/- 26 ms in symptomatic versus 104 +/- 19 ms in asymptomatic patients (P < 0.001). The optimized cut-off point of V(2) QRS > or =120 ms gave an odds ratio (OR) of 2.5 (95% CI: 1.4-4.6, P = 0.003) for being symptomatic. In a multivariate analysis adjusted with gender, age, and SCN5A mutation, the OR was 2.6 (95% CI: 1.4-4.8, P = 0.004).

CONCLUSION

Prolonged QRS duration, measured from standard 12-lead ECG, is associated with symptoms and could serve as a simple noninvasive risk marker of vulnerability to life-threatening ventricular arrhythmias in BrS.

Prevalence and prognostic significance of short QT interval in a middle-aged Finnish population

BACKGROUND

Short-QT syndrome is an inherited disorder characterized by a short QT interval and an increased risk of sudden cardiac death. The clinical significance of a short QT interval observed in a randomly recorded ECG is not known. Therefore, we assessed the prevalence and prognostic significance of a short QT interval in a general population.

METHODS AND RESULTS

QT intervals were measured from the 12-lead ECGs of 10 822 randomly selected middle-aged subjects (5658 males, mean age 44+/-8.4 years) enrolled in a population study and followed up for 29+/-10 years. The end points were all-cause and cardiovascular mortality. In addition to Bazett's method (corrected QT interval, or QTc), the Fridericia (QTfc) and nomogram (QTnc) methods were used to correct the QT interval for heart rate. The cutoff values for short QT intervals were defined as 320 ms (very short) and 340 ms (short). The prevalence of QT interval <320 ms based on QTc, QTfc, and QTnc was 0.10%, 0.08%, and 0.06%, and the prevalence of QT interval <340 ms was 0.4%, 0.3%, and 0.3%, respectively. The majority of subjects with short QT intervals were males. All-cause or cardiovascular mortality did not differ between subjects with a very short or short QT interval and those with normal QT intervals (360 to 450 ms). There were no sudden cardiac deaths, aborted sudden cardiac deaths, or documented ventricular tachyarrhythmias among subjects with a QTfc <340 ms.

CONCLUSIONS

A short QT interval does not appear to indicate an increased risk for all-cause or cardiovascular mortality in middle-aged nonreferral, community-based individuals.

Familial clustering of lone atrial fibrillation in patients with saddleback-type ST-segment elevation in right precordial leads

AIMS

We recently identified a large family with a high prevalence of lone atrial fibrillation (AF) and saddleback-type ST-segment elevation in leads V(1-3), without a history of ventricular arrhythmias or syncope. On the basis of this finding, we studied whether there is a relationship between saddleback ST-elevation and lone AF.

METHODS AND RESULTS

We examined 168 (mean age 50+/-8 years, 130 males) lone AF patients and 541 (mean age 50+/-6 years, 274 males) healthy subjects. The prevalence of saddleback ST-elevation was higher in the lone AF group than the control group (10 vs. 0.4%, P<0.001). None had a coved-type ST-elevation in baseline ECG or during drug challenge with ajmaline or flecainide (n=13), a family history of sudden cardiac death, ventricular tachyarrhythmias, syncope, or any other features diagnostic to the Brugada syndrome. Familial clustering of lone AF (i.e. AF in >30% of first-degree relatives) was more common among the subjects with saddleback ST-elevation (24 vs. 7%, P=0.03).

CONCLUSION

Saddleback-type ST-segment elevation is a relatively common finding among patients with lone AF. The familial clustering of the disorder indicates that genetic factors may be involved in the pathogenesis of the ECG abnormality and lone AF in these patients.

Prevalence and prognosis of subjects with Brugada-type ECG pattern in a young and middle-aged Finnish population

AIMS

The purpose of this study was (1) to determine the prevalence of Brugada syndrome ECG abnormalities ("Brugada sign") in two Finnish populations and (2) to evaluate the natural course of subjects with the "Brugada sign".

METHODS AND RESULTS

The study population consisted of 2479 healthy male Air Force applicants (age 18-30 years), and 542 healthy middle-aged subjects (age 40-60 years). All subjects underwent a thorough physical examination and 12-lead ECG in 1980-1990 (first population) and in 1991-1992 (second population). The ECG criteria suggested by the European Society of Cardiology were used to identify subjects with the "Brugada sign". Fifteen (0.61%) subjects in the first population and three subjects in the second population (0.55%) fulfilled the ECG criteria for type 2 or 3 Brugada syndrome, i.e., they had J-point elevation and a saddleback-type ST-segment configuration in the right precordial leads. Type 1 Brugada ECG abnormality (coved ST-segment elevation) was not seen in any subject. No mortality or life-threatening ventricular arrhythmias occurred in either study population during follow-up (19+/-2 years and 11+/-1 years, respectively).

CONCLUSION

The benign natural course of the patients with the "Brugada sign" suggests that in asymptomatic subjects without a family history of sudden cardiac death, type 2 or 3 Brugada ECG pattern is a normal variant rather than a specific predictor of life-threatening ventricular arrhythmias.