Page created on September 29, 2018. Last updated on May 24, 2019 at 13:45
The consequences of heart failure are categorized into two group: signs of forward failure and signs of backward failure, where forward symptoms come from problems occurring after the heart while backward symptoms come from problems occurring before.
The backward failure symptoms come from the increased venous tone and the congestion. The forward failure symptoms depend on which area is hypoperfused because of the heart failure. The actual clinical symptoms depend on which ventricle is affected. However, as we saw in topic 4, left and right-sided heart failure mostly occur together, symptoms from failure of both ventricles are seen together as well.
Forward failure symptoms of left-sided cardiac failure
The symptoms are explained by how the peripheral tissues’ O2 demand isn’t met by the cardiac output. Common symptoms are:
- Daytime oliguria with nightly polyuria (nycturia)
- Decreased absorption due to intestinal hypoxia
- Increased risk for pressure sores due to hypoperfusion of the skin
- Exhaustion during mild physical activity
- Cerebral dysfunction
- Due to hyperventilation and hypocapnia
- Pulmonary oedema (in acute heart failure)
In heart failure the body must redistribute blood from the kidney and GI tract to maintain perfusion of more important organs. During physical activity (even just walking), this redistribution is made even worse because now the muscles need blood as well. All of this leads to a markedly reduced renal perfusion and glomerular filtration during the day. This causes slight oedema. During the night, when the muscles don’t need blood anymore the kidneys will become normally perfused, which will result in large amounts of urine as the fluid storage that has been built up during the day is excreted.
Another mechanism that contributes to nycturia is that during the night the body assumes a supine position. This increases the venous return to the heart, causing the atria to be dilated slightly. This stimulates release of atrial natriuretic peptide (ANP) from the atria. This hormone stimulates diuresis.
Another consequence of the renal hypoperfusion is the activation of RAAS. Recall that the juxtaglomerular apparatus will produce renin in response to decreased renal perfusion. The activation of the RAAS will increase the blood pressure, which can make the heart failure even worse.
In acute and end-stage heart failure the cerebral perfusion will be impaired, causing cerebral hypoxia. This signals to the lungs that pulmonary capillary permeability should be increased, which causes fluid to enter the alveoli. This is called pulmonary oedema.
According to the pathophysiology department, this is the mechanism of pulmonary oedema development in acute heart failure. According to them, the increased hydrostatic pressure in pulmonary capillaries is not the cause; however other sources disagree.
Forward failure symptoms of right-sided cardiac failure
The forward failure symptom of right-sided cardiac failure is actually just left-sided heart failure. This is because right-sided heart failure results in less blood being pumped into the pulmonary circulation and therefore the left ventricle. Reduced left ventricular filling will eventually cause left-sided heart failure and the symptoms that accompany it.
4. Causes and forms of heart failure
6. Backward failure symptoms (left- and right-sided) in heart failure