Background: Despite recent progress in profiling of risk for sudden cardiac death (SCD) and prevention and intervention of cardiac diseases, SCD remains a major cause of death. Among women, the incidence of SCD is significant, but lower than in men, particularly in the premenopausal and early postmenopausal years. Possibly, as a consequence of the difference in population burden, the mechanisms and risk markers of SCD are not as well defined for women. The aim of this study was to determine the autopsy findings and causes of death among women in a large SCD population. Additionally, we sought to classify prior ECG characteristics in male and female subjects with SCD. Methods: The Fingesture study has systematically collected clinical and autopsy data from subjects with SCD in Northern Finland between 1998 and 2017. The cohort consists of 5869 subjects with SCD. Previously recorded ECGs were available and analyzed in 1101 subjects (18.8% of total population; and in 25.3% of women). Results: Female subjects with SCD were significantly older than men: 70.1±13.1 years versus 63.5±11.8 years (mean ± standard deviation, P <0.001). The most frequently identified cause of death was ischemic heart disease in both sexes: 71.7% among women versus 75.7% among men, P =0.005. In contrast, women were more likely to have nonischemic cause of SCD than men (28.3% versus 24.3%, P =0.005). The prevalence of primary myocardial fibrosis was higher among women (5.2%, n=64) than in men (2.6%, n=120; P <0.001). Female subjects with SCD were more likely to have normal prior ECG tracings (22.2% versus 15.3% in men, P <0.001). A normal ECG was even more common among nonischemic female subjects with SCD (27.8% versus 16.2% in men, P =0.009). However, ECG markers of left ventricular hypertrophy, with or without repolarization abnormalities, were more common among women (8.2%; 17.9%) than in men (4.9%; 10.6%, P =0.036; P <0.001, respectively). Conclusions: Women were considerably older at the time of SCD and more commonly had nonischemic causes. Women were also more likely to have a prior normal ECG than men, but an increased marker for SCD risk based on ECG criteria for left ventricular hypertrophy with repolarization abnormalities was more commonly observed in women.

The presence of a fragmented QRS complex (fQRS) in two contiguous leads of a standard 12-lead electrocardiogram (ECG) has been shown to be an indicator of myocardial scar in multiple different populations of cardiac patients. QRS fragmentation is also a predictor of adverse prognosis in acute myocardial infarction, coronary artery disease, and ischemic cardiomyopathy and a prognostic tool in structural heart diseases. An increased risk of sudden cardiac death associated with fQRS has been documented in patients with ischemic cardiomyopathy and hypertrophic cardiomyopathy. However, fQRS is also frequently observed in apparently healthy subjects. Thus, a more detailed classification of different QRS fragmentations is needed to identify the pathological fragmentation patterns and refine the role of fQRS as a risk marker of adverse cardiac events and sudden cardiac death. In most studies fQRS has been defined by the presence of an additional R wave (R′), or notching in the nadir of the S wave, or the presence of >1 R′ in two contiguous leads corresponding to a major coronary territory. However, this approach does not discriminate between minor and major fragmentations and the location of the fQRS is also neglected. In addition to this, the method is susceptible to large interobserver variability. We suppose that some fQRS subtypes result from conduction delays in the His-Purkinje system, which is a benign finding and thus can weaken the prognostic values of fQRS. The classification of fQRSs to subtypes with unambiguous definitions is needed to overcome the interobserver variability related issues and to separate fQRSs caused by myocardial scarring from benign normal variants. In this paper, we review the anatomic correlates of fQRS and the current knowledge of prognostic significance of fQRS. We also propose a detailed fQRS classification for research purposes which can later be simplified after the truly pathological morphologies have been identified. The research material of our study consist of 15,245 ECGs from the random general population and approximately six thousands (n = 6,241) ECGs from subjects with a known cardiac disease.

IMPORTANCE Myocardial infarction in the absence of major or unrecognized symptoms are characterized as silent (SMI). The prevalence of SMI among individuals who experience sudden cardiac death (SCD), with or without concomitant electrocardiographic (ECG) changes, has not previously been described in detail from large studies to our knowledge. OBJECTIVE To determine the prevalence of SMI in individuals who experience SCD without a prior diagnosis of coronary artery disease (CAD) and to detect ECG abnormalities associated with SMI-associated SCD. DESIGN, SETTING, AND PARTICIPANTS This case-control study compared autopsy findings, clinical characteristics, and ECG markers associated with SMI in a consecutive cohort of individuals in the Finnish Genetic Study of Arrhythmic Events (Fingesture) study population who were verified to have had SCD. The Fingesture study consists of individuals who had autopsy-verified SCD in Northern Finland between 1998 and 2017. Individuals who had SCD with CAD and evidence of SMI were regarded as having had cases; those who had SCD with CAD without SMI were considered control participants. Analyses of ECG tests were carried out by investigators blinded to the SMI data. Data analysis was completed from October 2018 through November 2018. MAIN OUTCOMES AND MEASURES Silent MI was defined as a scar detected by macroscopic and microscopic evaluation of myocardium without previously diagnosed CAD. Clinical history was obtained from medical records, previously recorded ECGs, and a standardized questionnaire provided to the next of kin. The hypothesis tested was that SMI would be prevalent in the population who had had SCD with CAD, and it might be detected or suspected from findings on ECGs prior to death in many individuals. RESULTS A total of 5869 individuals were included (2459 males [78.8%]; mean [SD] age, 64.9 [12.4] years). The cause of SCD was CAD in 4392 individuals (74.8%), among whom 3122 had no history of previously diagnosed CAD. Two individuals were excluded owing to incomplete autopsy information. An ECG recorded prior to SCD was available in 438 individuals. Silent MI was detected in 1322 individuals (42.4%) who experienced SCD without a clinical history of CAD. The participants with SMI were older than participants without MI scarring (mean [SD] age, 66.9 [11.1] years; 65.5 [11.6] years; P < .001) and were more often men (1102 of 1322 [83.4%] vs 1357 of 1798 [75.5%]; P < .001). Heart weight was higher in participants with SMI (mean [SD] weight, 483 [109] g vs 438 [106] g; P < .001). In participants with SMI, SCD occurred more often during physical activity (241 of 1322 [18.2%] vs 223 of 1798 [12.4%]; P < .001). A prior ECG was abnormal in 125 of the 187 individuals (66.8%) who had SCD after SMI compared with 139 of 251 (55.4%) of those who had SCD without SMI (P = .02). CONCLUSIONS AND RELEVANCE Many individuals who experienced SCD associated with CAD had a previously undetected MI at autopsy. Previous SMI was associated with myocardial hypertrophy and SCD during physical activ...