This research letter presents an exploratory pilot analysis of baseline overnight heart rate variability (HRV) data from the Sleep Heart Health Study (SHHS), examining whether autonomic markers at baseline differ between subjects who subsequently developed congestive heart failure (CHF) and those who remained free of cardiovascular events. Using pre-computed HRV summary data from the NSRR for 486 SHHS subjects (30 incident CHF, 456 healthy controls), we compared eight standard HRV metrics using Mann-Whitney U test. The LF/HF ratio — an established index of sympathovagal balance — was significantly lower at baseline in subjects who subsequently developed CHF (mean 1.847 vs 2.484, p=0.0066). No other metric reached significance. This observation suggests that reduced sympathovagal balance may be detectable in overnight recordings before clinical heart failure diagnosis. The finding is hypothesis-generating only. The CHF sample is small (n=30), the analysis is retrospective and exploratory, and no adjustment for confounders was performed. Replication in a larger prospective cohort is required before any clinical conclusions can be drawn. To our knowledge this is the first analysis linking overnight HRV scaling metrics to adjudicated CHF outcomes in the SHHS dataset. The finding motivates expanded HRV analysis across the full SHHS cohort and prospective investigation of sympathovagal balance as a pre-diagnostic marker for incident heart failure. Data accessed under NSRR data use agreement. Analysis code available on request