Can HRV predict a heart attack?

HRV cannot predict a heart attack as a standalone test, but low HRV is an independent predictor of cardiovascular mortality in clinical populations, men in the lowest quartile of HRV have approximately 3.5× the cardiovascular mortality risk of those in the highest quartile after controlling for other risk factors (Tsuji et al., Circulation, 1996).

The distinction between "predictor of mortality" and "predictor of a specific heart attack" matters. HRV reflects the overall state of the autonomic nervous system, which influences cardiac arrhythmia susceptibility, blood pressure regulation, vascular tone, and inflammatory activation, all pathways to cardiovascular events. In the post-myocardial infarction literature, HRV below specific thresholds identifies patients at high risk for sudden cardiac death. In healthy men, declining HRV trend data is a signal worth taking seriously, not a diagnosis. The man whose HRV has dropped from 45 ms to 22 ms over 8 weeks without illness or lifestyle change has a nervous system telling him something has changed. That deserves a physician's evaluation, not reassurance from an app.

Honesty Scale: Solid (1) for HRV as cardiovascular mortality predictor in clinical research. Early (3) for consumer wearable HRV as a heart attack prediction tool, the evidence is suggestive, not validated for clinical screening.

What to do: Do not use your wearable's HRV as your only cardiovascular screening tool. A declining trend is a reason to get a complete cardiovascular evaluation, ApoB, hsCRP, blood pressure, and discussion of a CAC score, not a standalone alarm.

For the full picture, read Your Whoop Is Worried. Here Is What It Actually Found.