We identified patients with hospital discharge ICD-10 diagnosis code (I49.01, I49.02, I47.2, I46.2, I46.8, or I46.9) between April 2017 and August 2022. From this eligible population, a convenience sample of 103 adult (age >18 years) patients with a transthoracic echocardiogram before the SCA that were suitable for postprocessing using the EchoPAC software were selected. Patients were excluded if they had LVEF <50% (n = 36), hypertrophic cardiomyopathy (obstructive or nonobstructive) (n = 6), severe aortic stenosis (n = 6), atrial fibrillation (n = 8) or paced rhythm (n = 4) at time of echocardiography. Final population comprised 43 SCA patients. The majority of excluded patients were excluded for LVEF <50%. The control group consisted of individuals from the same source population who underwent complete transthoracic echocardiography (TTE) during the same period and met the same inclusion criteria but did not have subsequent SCA. Controls were matched by age and sex to SCA survivors in a 2:1 ratio. The study protocol complied with the Declaration of Helsinki and was approved by the Institutional Review Board.

SCA was defined as a sudden loss of cardiac function resulting in hemodynamic collapse, requiring resuscitation or leading to death within one hour of symptom onset. SCA events were identified based on hospital discharge ICD-10 codes consistent with sudden cardiac arrest or malignant ventricular arrhythmia. Patients’ characteristics were recorded from medical charts. CAD was defined as >50% stenosis in any proximal or mid coronary artery distribution. For patients without overt cardiovascular disease (no CAD or ischemic stroke), the 10-year risk of major adverse cardiovascular and cerebrovascular events was estimated using the ASCVD risk score, calculated according to current guidelines for individuals aged 40 to 79 years. In addition, ASCVD and PREVENT risk scores were calculated in line with recent recommendations. A high-risk category was defined as a 10-year estimated risk of ≥20% for both ASCVD and PREVENT risk scores. ^,

Twelve-lead electrocardiograms (ECGs) were retrospectively collected from patient charts. For each patient, the ECG recording closest in time to the echocardiographic examination was selected. Heart rate, QRS duration, and QT interval were recorded. The QT interval was defined as the time from the onset of the Q wave to the end of the T wave. Heart rate correction of the QT interval was performed using the Fridericia formula: QTc = QT interval/³√ RR.

Echocardiograms were performed using Vivid E9 and Vivid E95 ultrasound systems (GE Healthcare, Horten, Norway and Chicago, USA). Left ventricular (LV) geometry was categorized according to the recommendations of the American Society of Echocardiography. An increased LV mass index was defined as ≥134 g/m² in males and ≥110 g/m² in females. Increased relative wall thickness (RWT) was defined as ≥0.45. Based on the combination of LV mass index and RWT, 4 geometric patterns were identified: normal (normal LV mass index and normal RWT), concentric remodeling (normal LV mass index with increased RWT), concentric hypertrophy (increased LV mass index and increased RWT), and eccentric hypertrophy (increased LV mass index with normal RWT). Concentric remodeling, concentric hypertrophy, and eccentric hypertrophy were collectively classified as abnormal LV geometry.

Speckle-tracking strain analysis was computed from cine-loops acquired at 40 to 90 frames/second during sinus rhythm. Speckle-tracking echocardiography was conducted in accordance with the recommendations of the strain standardization task force using the Automated Function Imaging tool. Postprocessing was performed using commercially available dedicated software (EchoPAC version 2.06, GE Healthcare, Horten, Norway). Time to peak longitudinal strain was defined as the interval from the onset of the QRS complex on the ECG to the peak negative longitudinal strain. LVMD was calculated as the standard deviation of the time to peak negative strain from 16 left ventricular segments. Mechanical dysfunction was defined as the combination of impaired GLS and prolonged LVMD as defined from the receiver-operating characteristics (ROC) curve analysis by Youden index.

Standard statistical software programs (SPSS, version 30, SPSS, Inc. Chicago, IL) and R Project for Statistical Computing (version 4.4.0, Vienna, Austria) were used. Propensity scores were estimated using age and sex, and 1:2 nearest-neighbor matching was performed to create balanced population for the comparison of groups with and without SCA. Balanced cohorts by 1:2 propensity score matching was conducted using the MatchIt package in R, with logistic regression to estimate the propensity score for each patient based on age and gender. Nearest-neighbor matching was applied with a caliper width of 0.1 and a 1:1 ratio, without replacement. Covariate balance between groups was assessed using standardized mean differences, with values <0.1 indicating good balance. The normal distribution of the data was tested by the Kolmogorov-Smirnov test, with a p-value <0.05 indicating a non-normal distribution. For comparison of 2 independent groups, Student’s t test was used for normally distributed continuous variables, the Mann-Whitney U test for non-normally distributed variables. For categorical variables, the Pearson Chi-Square test was used to assess associations between groups. Fisher’s exact test (2-sided) was additionally applied for the ASCVD and PREVENT subgroup analysis, given the smaller sample size. Median of LVEF (60%) was used for purposes of dichotomization in logistic regression models as all the patients had preserved LVEF. The optimal discriminatory GLS and LVMD thresholds were determined from the ROC curves and Youden Index. Stratified logistic regression analysis was further performed to assess effect modification by CAD for the associations of GLS ≥–14% and LVMD ≥75 ms with SCA. Likelihood ratio tests were used to assess the incremental value of GLS LVMD to CAD, ASCVD and PREVENT risk scores (≥20%). A p-value <0.05 was considered statistically significant.