“The healthy heart dances, while the dying organ can merely march.” Ary Goldberger.
It would seem obvious that a healthy heart should maintain a constant and steady heart rate, like clockwork. Conversely, a diseased heart would presumably be characterised by an irregular heartbeat. Until recently, expert medical opinion mirrored this seemingly obvious intuition. In 1989, Ary Goldberger and his colleagues showed1 that this conventional wisdom was not only mistaken, it was an exact inversion of reality. The time intervals between the beats of a healthy heart varied constantly in an unpredictable manner. It was in fact the diseased heart that exhibited perfect predictability and regularity, with the intervals between beats sometimes being identical. A healthy state is characterised not by stability or perfect predictability but by variability and unpredictability. In the diagram below showing the heart records of three patients, it is the relatively irregular heart rate of record B that is the only healthy one. The regular patterns of A and C are of patients suffering from severe heart failure.
But just as perfect order and predictability is pathological, so is constant disorder and excessive disturbance. Just as the regular heart-rate patterns of panels A and C signify a heart on the verge of failure, so does the excessively irregular heart-rate pattern of panel D below.
- ‘Fractal dynamics in physiology: Alterations with disease and aging’ (Goldberger et al, 2002). ↩