The cardiac cycle and the physiologic basis of left ventricular contraction, ejection, relaxation, and filling.

Heart failure is defined as the pathologic state in which the heart is unable to pump blood at a rate required by the metabolizing tissues or can do so only with an elevated filling pressure. Heart failure in adults most frequently results from the inability of the left ventricle to fill (diastolic performance) or eject (systolic performance) blood. The severity of heart failure and its prognosis are more closely related to the degree of diastolic filling abnormalities than the ejection fraction, which underscores the importance of understanding the mechanisms of diastolic abnormalities in heart failure.