Pressure-volume loops can be used to model the changing pressure and volume during the normal cardiac cycle, as well as demonstrating the changing haemodynamics involved in disease states. A pressure-volume loop is a model used to describe the dynamic relationship between pressure and volume over a cardiac cycle.
The two components of heart failure are distinct when explored through pathophysiological principles, but in clinical practice there is considerable overlap – and the majority of cases will be a mixed pathology. Diastolic failure will often have an element of impaired myocardial contractility (Yip et al., 2002), while in the case of systolic failure preload may also be increased (Skaluba & Litwin, 2004). Figure 3 demonstrates the crossover of the pathological spectrum; an ejection fraction of around 45–50% of normal represents the midpoint (Komamura et al., 2013).
Systolic time intervals also change during cardiac dysfunction with the left ventricular ejection time shown to be an independent predictor of incident heart failure among 1,980 middle-aged African-Americans participating in a community-based cohort (Biering-Sørensen et al., 2018).