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BIOTRONIK SE & Co.KG
Tel. +49 (0) 30 68905 0
When the heart muscle is no longer strong enough to pump a sufficient supply of blood into the body and meet its needs for oxygen and nutrients, the condition is called congestive heart failure. Congestive heart failure, also called myocardial weakness, is one of the most common diseases of our time.
Congestive heart failure is responsible for the greatest number of hospital admissions and deaths for people under age 65. Across Germany alone, up to 1.5 million people suffer from cardiac failure, and there are 200,000 new cases each year. Congestive heart failure is most common in the elderly and is becoming more important in the healthcare sector due to increasing life expectancy.
Symptoms of heart failure can include:
Possible causes of heart failure
The possible causes of congestive heart failure include heart attacks (also known as myocardial infarctions), valvular heart disease, permanent high blood pressure and inflammation of the heart muscle (myocarditis). A significant proportion of patients also have a familial predisposition, e.g., a congenital heart defect. A heartbeat that is too slow, too fast or irregular also negatively affects the heart muscle over time and can weaken it permanently.
The causes of congestive heart failure, though, are not always obvious. Patients usually know that they have high blood pressure or damaged vessels, but they often do not know that over time it can cause such damage to their hearts—and that their heart muscles are severely weakened.
Abnormal enlargement of the heart
If the heart muscle is constantly stressed over time, for example by diseases (e.g., high blood pressure [hypertension]), the size and weight of the heart changes gradually. Like other muscles, it gradually builds additional muscle mass so that it can meet the increased demand and pump blood through the body.
Enlarged left ventricle
In many congestive heart failure patients, the left ventricle of the heart contracts too late. Because the ventricle does not sufficiently fill with blood, its ability to function properly is impaired. The body tries to regain a sufficient pumping output by making the ventricle larger, which results in an abnormal enlargement of the left ventricle.
Consequences of cardiac failure
When cardiac failure does not cause symptoms, even under stress, it is called compensated congestive heart failure. Over time, the heart muscle loses more and more power until, eventually, it cannot contract strongly enough. This also reduces the amount of blood pumped into the systemic circulation (circulation through the body in general).
The heart tissue dies slowly and is eventually replaced by scar tissue. Reduced cardiac output has several effects in the long term. Initially, patients are usually short of breath and notice swelling in their legs. The oxygen and nutrient supply then declines, especially under physical stress—and then later at rest, too. Shortness of breath worsens, and the patients often need to take frequent rests
Compensatory mechanisms for offsetting reduced pumping action
At the beginning of congestive heart failure, the heart attempts to maintain blood supply and to compensate for the poor conditions resulting from cardiac disease. To do this, it has to change its structure and the way it works:
For a time, the heart muscle is able to meet the increased demand and can still provide an adequate blood supply to the body (compensatory mechanisms). This constant stress has severe effects, though, as the diseased heart muscle has become large but also weak.
As a result of these different underlying diseases, the weakened heart is no longer able to pump blood into the systemic circulation with enough power. At the same time, the blood returning to the heart from organs can no longer be pumped on quickly enough. This blood builds up “in front of” the heart.
If the left half of the heart is weakened, this blood accumulates in the lungs, causing shortness of breath and fits of coughing. If the right half of the heart is weakened, the congestion in the systemic circulation causes water retention (edema) in the legs and other body parts. This causes a sharp increase in body weight. Often, both halves of the heart are affected.
Congestive heart failure emergency (decompensation)
Symptoms such as shortness of breath and edema typically develop slowly over the course of several days to weeks. Occasionally, there may be a sudden shortness of breath.
When the compensatory mechanisms are no longer effective (for example, due to ventricular fibrillation or a hypertensive crisis), breathing becomes increasingly difficult and sounds wet and raspy. This is often accompanied by a strong feeling of pressure or tightness in the chest (thoracic) area. In these situations, an ambulance should be called immediately. Until the ambulance arrives, the patient should relax and, if possible, sit upright while waiting. The emergency physician can assess the situation faster if the most critical documents (e.g., CRT ID, medication list, copies of medical reports) are immediately available.
Disturbance in electrical stimulus conduction (left bundle branch block)
Changes to the heart muscle may also have a negative effect on electrical stimulus conduction in the heart. Dying cardiac muscle cells and increasing connective tissue formation impede the conduction of electrical pulses. Electrocardiogram (ECG) examinations may show a broadened curve complex and an altered curve shape that is diagnosed by the doctor as left bundle branch block.
There is delay between conduction in the two ventricles and within the left ventricle itself. The uneven contraction of the left ventricle further lowers pumping output.
Around one-third of all cardiac failure patients also suffer from sometimes life-threatening cardiac rhythm disturbances. They have a six-to-nine-fold greater risk of dying of sudden cardiac death. The altered heart muscle causes occasional misfires in the ventricles that do not follow the normal excitation sequence and can trigger a chain reaction ending in ventricular fibrillation. The heart’s pumping function comes to a halt, so the brain and organs no longer receive oxygen. The patient loses consciousness and is at risk of dying if the ventricular fibrillation cannot be stopped within the next few minutes.
Stages of cardiac failure
Cardiac failure can be assessed according to its development over time. It is acute cardiac failure if symptoms arise suddenly, intensely and within a short time. In contrast, chronic cardiac failure develops slowly over many months or years.
Cardiac failure can be categorized into different stages as classified by the New York Heart Association (NYHA):
In class one, the patient does not feel affected, but the heart is already weakened. This aspect is important when taking medication. If you feel relatively well although your physician has diagnosed cardiac failure, it is important that you take your medications regularly and consistently so that you can counteract disease progression at an early stage.
ICD electroshocks terminate tachycardias
A heart failure implantable cardioverter-defibrillator (ICD) offers yet another level of treatment—it delivers electroshocks to terminate tachycardias (heart rhythms that are so fast that the blood no longer circulates sufficiently).
Causes for tachycardia include narrowing of the coronary arteries, myocardial infarctions or other cardiac diseases that occur frequently in concert with congestive heart failure.