Page created on September 29, 2018. Last updated on May 21, 2020 at 17:14
Backward failure symptoms of left-sided cardiac failure
The main backward failure symptoms of left-sided heart failure are:
- Dyspnoea, especially on exertion
- Paroxysmal (sudden) nocturnal dyspnoea
- Wet lung
- Pulmonary oedema (when alongside acute left heart failure)
Left-sided heart failure won’t just cause hypoperfusion of organs but also congestion of the pulmonary circulation. This happens because the amount of blood going into the left ventricle is higher than the amount going out, which causes a sort of “traffic jam” of congestion backwards, causing blood to congest inside the pulmonary circulation (and further backwards into the right heart as well). This congestion causes the pressure in all pulmonary vessels to increase.
Pulmonary congestion is defined as when the lungs contain more than 9% of the total blood in the body, but no fluid has left the vessels yet. See this topic for more information. Pulmonary congestion increases the elastic resistance, work of breathing and causes dyspnoea by mechanisms explained here.
Because of the increased hydrostatic pressure in the pulmonary capillaries will fluid leave the capillaries into the interstitium, a process called extravasation. This is called wet lung, where fluid accumulates in the interstitium of the lung. The interstitial fluid makes gas exchange more difficult. The amount of fluid isn’t enough to cause oedema, as the lymphatic system will drain it.
Backward failure symptoms of right-sided cardiac failure
For the same reasons as in left-sided heart failure will right-sided heart failure cause congestions in the vessels before it, the large veins. When symptoms of congestion appear we call the condition congestive heart failure. Symptoms are:
- Hepatic venous congestion
- Haemolytic anaemia
- Distended jugular vein
- Lower extremity oedema
- Impaired nutritional absorption
Because of the congestion in the veins will the pressure inside them increase as well. The congestion will travel “backwards” into the capillaries, especially in the lower limbs. The resulting increase in capillary hydrostatic pressure will cause a large amount of salt and water to leave the capillaries into the interstitium. The amount is so large that it cannot be carried away be the lymphatic circulation. This causes a lot of fluid to remain in the interstitium, which is what causes swelling, or oedema. Congestive heart failure causes how pitting oedema, where the swelling will leave a “pit” if pressed. 1 – 1.5 L of fluid must enter the tissues for pitting oedema to be visible.
During the day when the patient is up and walking will fluid accumulate in the legs due to gravity. However, at night, when the patient lies flat will the fluid be reabsorbed into the circulation, which is what causes the nycturia. Note that nycturia develops in both right sided (backward) failure and in left sided (forward) failure, but by different mechanisms.
Because of the congestion in the large veins the portal vein will be congested as well, which makes absorption of nutrients more difficult for the GI tract.
Congestion of the inferior vena cava can cause all kinds of problems with the liver. In addition to becoming enlarged, jaundice can occur.
Splenomegaly occurs due to congestion. The spleen will fill up with RBCs. The enlargement also causes the spleen to become hyperactive and haemolyse too many RBCs, a condition called hypersplenism. Haemolytic anaemia may develop because the hyperactive spleen destroys too many RBCs.