Introduction: We have previously reported that electrocardiographic (ECG) left ventricular hypertrophy (LVH) can occur in the absence of increased LV mass (echocardiographic LVH), and conveys unique risk of sudden cardiac arrest (SCA). We further characterized this adverse “electrical remodeling” by comparing SCA cases with isolated electrical vs. isolated anatomic LVH. Hypothesis: Cases with electrical versus anatomic LVH have distinct clinical profiles Methods: Adult SCA cases were prospectively ascertained from multiple sources in a Northwestern US metro area (population approx. 1 million). Clinical/demographic information was obtained from medical records. ECGs, prior and unrelated to SCA were reviewed in blinded fashion to detect ECG-LVH (Sokolow-Lyon criteria). LV mass, obtained from echocardiograms was used to identify echo-LVH (LV Mass Index > 134 g/m2 men; 110 g/m2 women). Cases with isolated ECG-LVH versus isolated echo-LVH were compared to identify distinctive characteristics. Patients who had LVH by both tests and those without LVH by either test were excluded. Results: Among 323 SCA cases (2002-14; 69.0 ± 13.5 yrs; 66.9% male) with adequate information available, echo-LVH was present in 134 (41.5%) cases and ECG-LVH in 58 (18.0%) cases. After elimination of cases with LVH by both modalities, 103 (31.9%) cases had isolated echo-LVH while 27 (8.3%) had isolated ECG-LVH. Compared to cases with isolated ECG-LVH, isolated echo-LVH cases had lower LV ejection fraction (45.2 ± 16.9 vs. 53.0 ± 14.8%; p=0.03), were more likely to be current smokers (30.8 vs. 8.7%; p=0.06), obese (41.7 vs. 25.9%; p=0.12) and African-American (19.4 vs 7.4%; p=0.15). There were no significant differences between the two groups for systemic hypertension (78.6 vs. 88.9%; p=0.23), age, sex, diabetes, renal disease, coronary artery disease or prior myocardial infarction. Prescription of anti-hypertensive medications including ACE inhibitors, angiotensin receptor blockers and beta blockers were equally likely in both groups. Conclusions: Patients with electrical vs. anatomic LVH appear to have distinct clinical profiles. These findings can serve as a foundation for further investigation of genetic and acquired mechanisms of electrical LVH leading to sudden death.