APD Alternans

$$APD_n +RT_n = BCL$$ (1)

where

• $APD$ is the Action Potential Duration;
• $RT = DI$ is the Recovery Time or Diastolic Interval;
• $BCL$ is the Basic Cycle Length.

If $APD_n = A(RT_{n-1})$ is the restitution curve, then

$$RT_n = BCL - A(RT_{n-1}).$$ (2)