Sympathetic activity-associated periodic repolarization dynamics predict mortality following myocardial infarction

Area of Science:

• Cardiology
• Autonomic Nervous System Physiology
• Cardiac Electrophysiology

Background:

• Enhanced sympathetic activity in the ventricular myocardium can destabilize cardiac repolarization, increasing mortality risk.
• Sympathetic activity often occurs in low-frequency bursts, suggesting a link to periodic repolarization changes.
• Periodic repolarization dynamics (PRD) were identified as low-frequency (≤0.1 Hz) periodic components of repolarization.

Purpose of the Study:

• To develop and validate a technique for assessing the sympathetic effect on cardiac repolarization.
• To investigate the physiological properties and prognostic value of PRD.
• To compare the predictive power of PRD with T-wave alternans (TWA).

Main Methods:

• Investigated PRD in swine models and human studies including atrial pacing, head-up tilt, exercise testing, and beta-blockade.
• Assessed the prognostic significance of PRD in 908 acute myocardial infarction (MI) survivors for 5-year mortality.
• Evaluated the predictive value of PRD and TWA in 2,965 patients undergoing exercise testing.

Main Results:

• PRD was independent of respiratory activity and heart-rate variability.
• PRD correlated with sympathetic nervous system activation and was suppressed by beta-blockade.
• Increased PRD was the strongest predictor of 5-year mortality post-MI (HR 4.75) and showed complementary predictive value to TWA in exercise testing.

Conclusions:

• Low-frequency rhythmic repolarization modulations, termed PRD, are associated with sympathetic activity.
• Elevated PRD serves as a significant predictor of mortality in post-MI patients and those undergoing exercise stress tests.