Edema is considered the cardinal feature of cardiac failure for decades. It is one of the minor criteria of the Framingham protocol to diagnose cardiac failure.
The mechanism of edema in cardiac failure is multifactorial . The major mechanism attributed is raised venous pressure. This is transmitted backwards into the circulation and resultant increase in hydrostatic pressure in the venous end of capillaries results in edema .
Even though this is considered as the dominant mechanism for decades , it may not be true. Apparent reduction in cardiac output (Effective circulatory volume) and resultant reduction in renal blood flow triggers renal ischemic response and RASS activation (Rennin angiotensin aldosterone system). This is a powerful stimulus for sodium and water retention . This could be the major mechanism of cardiac edema. While there is clearcut explanation for the mechanism of edema in cardiac failure the explanation for lack of edema in many is not available in literature.
Does the activation of neuroendocrine happen in every one with cardiac failure ?
We think so ! but it may not be. Further, activation of RASS trigger a counter hormone response mediated by atrial natriuretic peptide that promotes active water loss from the distal tublues which could prevent edema formation in many. So there is a distinct group of patients with cardiac failure who rarely develop edema .
In which type of cardiac failure edema is common and gross?
- Predominatly right sided failure.
- Corpulmonale
- Tricuspid valve disese
- Constrictive pericarditis
Dr.S.Venkatesan MD 