Apart from acute heart failure, a heart attack may not cause sudden loss of heart muscle function, but progressive changes. This is because after the loss of a section of heart muscle, the heart adapts by enlarging reactively. In the short term this bolsters heart function, but after a period of time (weeks to months) causes heart function to weaken and cause progressive heart failure.
Myocarditis:
This is when a significant area of heart muscle becomes inflamed and dysfunctional. This usually secondary to a viral infection and is not that common. However it can affect people of any age. It can be self limiting and cure itself. However it can occasionally be progressive and cause permanent changes and heart failure (see later).
Dilated Cardiomyopathy:
Cardiomyopathy is a broad term to cover a wide spectrum of conditions affecting heart muscle specifically. Dilated cardiomyopathy (DCM) occurs when the heart becomes enlarged in response to an insult to the muscle cells. It can be acute and reversible as with viral myocarditis. It can also be acute if the muscle is inflamed with progressive alcohol exposure (alcohol cardiomyopathy). This is surprisingly common, and can be reversed in earlier stages of the condition.
In more chronic cases, dilated cardiomyopathy can occur after previous myocardial infarction. Less commonly, but increasingly recognised is a familial dilated cardiomyopathy. This is an inherited condition and very important to identify. It can present before any symptoms of heart failure, usually when a chest X ray might have been performed incidentally for other reasons, and the heart was noted to be enlarged. In this condition, heart failure develops for no particular reason. In such cases, the relevance is that other family members need to be screened for the condition before it becomes a problem. Another rare but important cause of heart failure is peri-partum cardiomyopathy. As the name suggests, this occurs in response to giving birth, and should be considered in any new mother complaining of increasing breathlessness.
Other Cardiomyopathies:
This includes restrictive cardiomyopathy, where the muscle becomes infiltrated with other pathological substances, or damaged by toxins or drugs. Hypertrophic cardiomyopathy where the there is abnormal thickening of heart muscle is discussed separately.
Diagnosis of Heart Failure:
Heart failure is usually suspected in patients who have developed breathlessness. Patients often complain of swelling in the ankles. Cardiac failure is often suspected in cases of leg swelling. It should be born in mind that leg swelling can be due to many other causes (see under Symptoms). Sometimes a cardiomyopathy may be suggested by a routine chest X-ray performed for other reasons, and the heart found to be enlarged. Often an apparently enlarged heart on the X ray in the absence of symptoms is usually a shadow projection issue, and not truly an enlarged heart, but it is worth checking it out.
An ECG is essential, although it can be normal. Prior to performing an echocardiogram, primary care doctors may perform a blood test to measure a body chemical called B-derived naturetic peptide (B-NP) that is elevated in heart failure. The main investigation in heart failure is the echocardiogram. This can confirm the diagnosis of heart failure and sometimes indicate the underlying cause. In addition it can detect the presence of diastolic failure. In this case, the heart is usually of normal size but the patient may be breathless. The failure is due to a loss of heart muscle elasticity. More recently cardiac MRI has become an established means of diagnosing the cause of heart failure. In a fair few patients cardiac catheterization is performed if underlying coronary disease is suspected.
Treating Heart Failure:
Initial investigations such as cardiac catheterization may reveal the underlying cause, and suggest treatment. Otherwise, diuretics are initially prescribed to treat breathlessness. The main drug that impacts on prognosis are a family of drugs called ACE inhibitors (see under Drugs). These drugs act to lower the pressure in the heart and arterial circulation, and reduce the work the heart has to do. In recent years another class of tablets called beta-blockers have been used. These drugs also impact on prognosis too. They take up to a month before patients may feel symptomatic relief. They act on the principle that lowering the heart rate may improve the efficiency of heart function. Occasionally beta blockers may worsen heart failure symptoms. The other main medication that is used in heart failure is spironolactone (or eplerenone), which improves symptoms.
In addition to medication, lifestyle measures are important, such as reducing salt intake from dietary sources (often in take away foods and pizza!).
Certain types of pacemaker (called biventricular pacing or cardiac resynchronization therapy -CRT) have been shown to improve symptoms. Patients need to be pre-selected for such device therapy as not everyone benefits. Importantly, the ECG should indicate underlying left bundle branch block (LBBB). Specialised methods of echocardiography may help identify potential patients who may benefit from this treatment.
|
Abnormalities of the Electrical
Conducting System
This covers a large number of conditions resulting in reduced heart pumping, and can be classified in many ways. If symptoms are sudden in onset, it is termed acute heart failure. If more progressive, it is termed as chronic heart failure. Most commonly when the heart’s ability to pump is affected, it is called systolic failure. Impaired systolic function is defined when the ejection fraction on echocardiography is less than 55%. Less commonly if the heart’s ability to relax and fill is affected it is termed diastolic failure (see below). Heart failure can present in many ways, but principally heralded by the onset of breathlessness on exertion. As the pump becomes less effective, the circulation is reduced causing increasing fatigue and reduced ability to exercise. 