Causes
Congestive heart failure has both cardiac (i.e. heart-related) or extra-cardiac (i.e. from somewhere other than the heart) causes. Cardiac causes include coronary artery disease, previous myocardial infarction, valvular heart disease and other kinds of heart conditions. Extra-cardiac causes include hypertension, pulmonary disease, renal disease, diabetes and other conditions that place more demands on the cardiovascular system.
Classifications
Congestive heart failure can be classified according to anatomy, function or onset. Anatomical classification can be broken down into right-sided failure, left-sided failure or biventricular (i.e. both ventricles) failure. Functional classifications are systolic dysfunction (i.e. inability of the heart to contract) and diastolic dysfunction (i.e. inability of the heart to relax). Onset can be either acute or chronic.
Pathophysiology
When the heart is unable to pump around sufficient blood, the stroke volume decreases, causing cardiac output to decrease and tissue perfusion to decrease. Also, blood can back up in the veins leading to the heart (hence congestive heart failure). If the right side of the heart fails, then this congestion mainly occurs in the systemic circulation, whereas if the left side of the heart fails, then this congestion mainly occurs in the pulmonary circulation.
Our body has ways of trying to compensate when cardiac output is decreased. Unfortunately, in the case of congestive heart failure, these compensatory mechanisms can often aggravate rather than improve the condition. Two of the main ways that the body attempts to compensate is by activation of the sympathetic nervous system (discussed in more detail here) and by activation of the RAAS (Renin-Angiotensin-Aldosterone System) pathway (discussed in more detail here). Both of these work to try and increase blood pressure, but of course this just puts more work on the heart as it has to pump harder in order to overcome the increased blood pressure. Other ways in which the heart tries to compensate is by growing larger (cardiomegaly), but that also aggravates the problem as the larger heart cells require more oxygen than usual to keep going.
Manifestations
General manifestations of congestive heart failure (CHF) include dyspnea (shortness of breath), fatigue and cough following exertion, as well as tachycardia, pallor and oliguria (lack of urine) due to the compensatory effects of the sympathetic nervous system and RAAS system. Some of the other manifestations of congestive heart failure are more specific to the side that is being affected.
As mentioned earlier, left-sided CHF causes blood to back up in the pulmonary circulation. This causes dyspnea (shortness of breath), orthopnea (shortness of breath even when lying down), paroxysmal nocturnal dyspnea (PND) (shortness of breath during the night), haemoptysis (coughing up blood) and other lovely respiratory symptoms. In acute left-sided CHF, pulmonary oedema can occur.
Right-sided CHF, which is usually caused by left-sided CHF, causes blood to back up in the systemic circulation. This causes dependent oedema (oedema due to gravity- when the patient is standing fluid pools in the legs, when they're lying down it pools in their back), digestive disturbances, hepatomegaly, splenomegaly, ascites (fluid in the abdominal cavity), distended jugular veins and in acute cases, headache and visual disturbances. Aside from left-sided CHF, other conditions can cause right-sided CHF, such as cor pulmonale (chronic lung disease leading to CHF), and other factors such as diseases and valve lesions.
Diagnosis
There are several ways to look at diagnosing heart failure. The most important ones are chest X-ray and echocardiography, which can help to visualise the heart and look for cardiomegaly, valve lesions, wall motion abnormalities and so forth. ECG and cardiac catheterisation may also help in some cases.
Treatment
Just like the other heart diseases examined so far, treatment involves a mixture of drugs, non-drug treatments and treating the cause directly.
Drug treatments include diuretics (stop the body from retaining too much fluid in the blood), inhibitors of the RAAS pathway, β-blockers, vasodilators and positive inotropic agents (i.e. stuff that increases strength of contraction) such as digitalis. Non-drug treatments involve bed rest (during acute condition) with gradual rehabilitation back to normal activity, restricting salt in the diet and surgical treatments such as valve repair and transplantation.
Here's another alphabetic mnemonic for you:
- A is for ACE (angiotensin-converting enzyme) inhibitors, angiotensin receptor blockers and aldosterone antagonists (i.e. RAAS inhibitors)
- B is for bed rest and beta-blockers
- C is for cardiac transplantation
- D is for diet, digitalis, diuretics and dilators
In Children...
Children can get CHF too, unfortunately. In children, it's usually secondary to congenital heart defects. Usually the first sign of CHF is feeding difficulty, followed by failure to thrive (i.e. inability to gain weight), short sleep periods and some respiratory distress. Their heartbeats may also have a "gallop rhythm" (i.e. sound like a horse galloping).
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