Thursday, January 19, 2012

Types of Heart Failure and Causes

The heart failure may be classified in several ways.
  1. Acute versus chronic
  2. Left versus right and biventricular or congestive heart failure (CCF)
  3. Forward versus backward
  4. Systolic versus diastolic
  5. low output versus high output

ACUTE VERSUS CHRONIC HEART FAILURE
Acute heart failure
Heart failure developing suddenly in hours a days in a previously asymptomatic patient is called acute heart failure.

Causes
The causes of acute heart failure occur when a previously normal person suddenly develops a serious anatomical or functional abnormality and time is not sufficient for compensatory mechanisms to operate such conditions are:
  • Massive acute myocardial infarction.
  • Tachyarrhythmias with very rapid heart rate.
  • Rupture of valve secondary to infective endocarditis.

Chronic heart failure
Heart failure developing gradually is called chronic heart failure. In this type of failure a variety of compensatory changes may take place in early phase to improve cardiac function. These adoptive mechanisms allow the patient to adjust and tolerate not only the anatomic abnormality but also a reduction in cardiac output with less difficulty.

LEFT VERSUS RIGHT AND BIVENTRICULAR OR CONGESTIVE HEART FAILURE

Left sided heart failure
The left sided heart failure is characterized by a reduction in effective left ventricular output for a given pulmonary venous or left atrial pressure.
An acute increase in left atrial pressure may cause pulmonary congestion or pulmonary edema, while chronic increase in left atrial pressure leads to reflects pulmonary vasoconstriction which protects the patient from pulmonary adema at the cost of increasing pulmonary hypertension (as a compensatory mechanism).

Causes of left heart failure
  • Ischemic heat disease (commonest)
  • Systemic hypertension
  • Mitral and aortic valve disease
  • Cardiomyopathies

Right side heart failure
Right-sided heart failure in characterized by reduction in right ventricular output for any given right atrial pressure.
Causes of right heart failure
  • Secondary to left heart failure (most common)
  • Chronic lung disease (Causing cor-pulmonale)
  • Pulmonary embolism or pulmonary hypertension
  • Tricuspid and pulmonary valve disease
  • ASD & VSD
  • Right ventricular cardiomyopathy

Biventricular or congestive cardiac failure (CCF)
When both sides of heart are involved, features of both right and left heart failure are present. In most of the patient right heart failure is a result of preexisting left heart failure.

FORWARD VERSUS BACKWARD FAILURE

Forward failure
In some patients with cardiac failure predominant problem is an inadequate cardiac output that leads to diminished perfusion of vital organs, leading to ischemia of these organs this is called forward failure. Ischemia of brain causes mental confusion, ischemia of skeletal muscles leads to weakness, ischemia of kidneys causes sodium and water retention leading to symptoms of heart failure.

Backward Failure
In some patients cardiac failure presents mainly with features of damming of blood into venous system such as lung congestion in left heart failure and congestion of liver, spleen and other areas in right heart failure.

SYSTOLIC VERSUS DIASTOLIC FAILURE

In majority of patients heart failure is due to combine systolic and diastolic dysfunction, however isolated systolic or diastolic dysfunction may be present.

Systolic Failure
Heart failure may develop as a result of impaired myocardial contraction (systolic dysfunction). The most common cause of systolic ventricular dysfunction is ischemic heart disease usually after myocardial infarction. The left ventricle is usually dilated and fails to contract normally resulting in symptoms of predominantly forward failure.

Diastolic Failure
Heart failure may develop due to poor ventricular filling caused by impaired ventricular relaxation (diastolic dysfunction). The most common cause is left ventricular hypertrophy as a result of hypertension and coronary artery disease. Other causes of diastolic dysfunction are hypertrophic and restrictive cardiomyopathy, diabetes and pericardial disease.

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