Heart Failure explained..

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Heart has the important function of pumping blood forward to the rest of the body. It does so by first ‘relaxing’ to accept the blood and then ‘contracts’ to pump the blood forward. Both these events, relaxation and contraction, could be affected and broadly constitute the term of ‘heart failure’. These are not independent of each other and it is not unusual for patients to have both the functions affected. Each is a topic of its own. Problems with heart contraction function is called systolic heart failure. 

Systolic heart failure: 

Normally the left lower chamber pumps forward 55-60% of the blood contained within it. This is called the ejection fraction of the left ventricle and commonly quoted number when describing heart function (figure 1).

Figure 1: Deconstructed blood flow diagram

The percentage at which a person is called to have systolic heart failure varies with the person answering. However, most physicians would agree that the absolute number carries less importance than the symptoms themselves. 

The most common cause of systolic heart failure is if the heart muscles do not get enough blood supply. Refer to the basic anatomy blog for more details on the blood supply to the heart. The blood supply problem may either occur suddenly in case of a heart attack or slowly and progressively when plaque builds up over time. In majority of these cases, opening the blockage or bypassing it could offer the best results. This is not always possible, and the reasons are explained in another blog

Some of the other causes include direct injury to the heart muscles from toxins such as alcohol, hereditary iron deposition, conditions causing protein called amyloid deposition, certain chemotherapy agents, poorly controlled hypertension, diabetes or obesity, thyroid or other gland problems and advanced heart valve disease. There are some hereditary/congenital conditions which can cause weakened heart muscles. Other causes include pregnancy-induced, inflammation of heart muscles, autoimmune disease such as lupus or rheumatoid arthritis and HIV.  

Progression of heart failure: 

The direct consequence of failure of the left chamber pump is poor blood supply to the organs (figure 2).  

Figure 2: Failure of left chamber pump causes poor blood supply to organs

As the blood does not move forward from the left pump, the blood from the lungs is not able to enter the left chambers. Consequently, the pressure builds up in the lungs (figure 3). This is called pulmonary hypertension

Figure 3: Blood from the lungs is unable to enter the already filled left chambers, and pressure in the lungs rise.

Now this rising pressure is felt by the right chambers which have the important role of pumping blood into the lungs. However, the right chambers are not used to work against such high pressures, and it start failing progressively. This is like a low horsepower car with a trailer attached at the back attempting to climb a steep hill (figure 4). 

Figure 4: Rising pressure in the lungs increases the workload of the right chambers

Working our way back in the circuit, the blood now is not moving out of the right chambers, which makes it difficult for blood to leave the organs. This is like traffic building up on a ramp of a blocked freeway. The ‘congestion’ of blood in the organs causes progressive failure of these organs and this is called ‘congestive’ heart failure (figure 5). 

Figure 5: Blood unable to enter right chambers causes congestion within the organs

The speed of progression and the sequence of involvement may vary. Sometimes the right chambers may be affected early and the progression is rapid in this case. 

What is happening in the kidneys? 

Congestion, as described above, commonly affects the kidneys and the liver. Kidneys reflexively start retaining water and salt. This is a reflex inherited from our ancestors when one of the common causes of death was bleeding after a wild animal attack. The kidneys perceive the lack of blood coming from the failing heart as though the body is losing blood after an ‘animal attack’ and start retaining fluids to keep the blood vessels filled. Though this reflex may have saved many of our ancestors then, it works to worsen the workload on an already failing heart. 

Consequence of heart failure: 

Organs fail if they do not get blood supply. Blood backing up in the system can increase the pressure within the veins. One of the results is increased pressure in the lungs, called pulmonary hypertension. This then results in leakage of fluid into the lungs. It is perceived as increased shortness of breath, unable to sleep flat on the bed, waking up in the night choking.  

Fluid also leaks out in the legs, arms and/or belly causing swelling. If this continues, multiple hospital admissions result and require medications given directly into the blood.  

The heart failure process can be progressive in some, if not caught early and taken care of well. This is when advanced therapy through heart transplantation or a device placement which pumps the blood forward, called the ventricular assist device. However, there are multiple facets that need to be fulfilled to make sure the outcome is favorable. This is because, advanced heart surgeries can be life changing and need a lot of reserve. Consequently, they may not be the ideal solution in some cases. A good discussion with the physician is highly emphasized. 

What can be done? 

Treatment of the cause can reverse the heart failure in many cases. Simultaneously, certain medications are started which bring about favorable changes in the heart and prevent scar formation.  

Monitoring daily weights is essential and any indication of increasing weight needs to be noted. Medications are given to overcome this reflex in the kidneys and increase the urine output. These medications either act on the hormonal pathway within this reflex or remove the concentrating capacity. Either ways, the idea is to increase the urine output. This may also increase the flushing out of electrolytes, which need to be monitored. It also helps to restrict the daily fluid intake. 

There are other medications started shown in research to stop the heart failure process and also reverse some of the above-mentioned changes. Regular intake of these medications is of paramount importance. 

In advanced stages, a discussion is done for placement of an artificial heart pump or heart transplantation. Stay posted for a description on these.

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