Table 3. Autonomic abnormalities and electrical instability as risk predictors in elderly populations with heart failure.

Predictors	Associated with	Studies in elderly populations
HR variability	Poor outcomes and SCD
HR deceleration capacity	SCD and mortality
HR recovery after exercise	Mortality	Yes
BRS	Cardiovascular mortality and SCD	Yes
HRT	HF severity and SCD	Yes
QT variability	Cardiovascular mortality	Yes
TWA	SCD	Yes
TWR	SCD

BRS: baroreflex sensitivity; HF: heart failure; HR: heart rate; HRT: heart rate turbulence; SCD: sudden cardiac death; TWA: T-wave alternans; TWR: T-wave morphology restitution.