Heart failure fluid retention loop

This diagram presents one simplified feedback pattern in heart failure. A fall in cardiac output can reduce renal perfusion, which can increase RAAS activation and promote sodium and water retention. Retention can raise circulating volume and preload, contributing to pulmonary congestion; congestion can in turn worsen cardiac output. The diagram makes the direction of each relationship explicit and names the resulting reinforcing loop. It omits many important compensatory, treatment and patient-specific factors so that the core pattern remains readable. Use it in teaching or discussion as a starting point, and add a balancing loop only when its causal links are clear. It is not a clinical model for assessing or treating an individual patient.