Pressure-volume Relationship in Heart Failure

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.

Pressure volume loop in systolic heart failure.

Figure 1. Pressure volume loop in systolic heart failure (adapted from Komamura et al., 2013). Left ventricular pressure follows a loop during cardiac cycles: contraction and ejection (systole, red arrow), relaxation and filling (diastole, blue arrow). In systolic failure, it is the Emax which is decreased. In order to maintain adequate cardiac output, the pressure-volume loop shifts to the right, which increases preload on the heart, causing venous back-pressure.
Emax, index of systolic function; LV, left ventricle.

The pressure volume loop in diastolic heart failure.

Figure 2. The pressure volume loop in diastolic heart failure (adapted from Komamura et al., 2013).
A) Due to inadequate LV relaxation, the end diastolic pressure-volume relationship shifts upwards.
B) When an increase in blood pressure occurs, the pressure-volume loop shifts to the right without a decrease in Emax. This leads to a significantly higher end-diastolic pressure, causing back-pressure and venous congestion.
Emax, index of systolic function; LV, left ventricle.

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).

 Illustration of pathological spectrum and cross-over between diastolic and systolic components of heart failure

Figure 3. Illustration of pathological spectrum and cross-over between diastolic and systolic components of heart failure (adapted from Komamura et al., 2013).
LV, left ventricle.

Systolic time intervals also change during cardiac dysfunction with the left ventricular ejection time being 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).