Pathophysiology
Diastolic heart failure sometimes presents with concentric hypertrophy. In contrast, systolic heart failure sometimes presents with eccentric hypertrophy.
Diastolic dysfunction is characterized by elevated diastolic pressure in the left ventricle, despite essentially normal/physiologic end diastolic volume (EDV). Histologic evidence supporting diastolic dysfunction demonstrates hypertrophy of the cardiomyocytes, increased interstitial collagen deposition and infiltration of the myocardium. Calcium deposition within the myocardium closely follows this physiology. These influences collectively lead to a downhill spiral in distensibility and elasticity (ability to stretch) of the myocardium. The ventricles behave as a series of balloons similar to physiologically tailored rubber or latex, engineered to the beat to beat needs of the end organs served. Despite filling with high pressure, diastolic dysfunction impairs volumetric expansion.
If the heart cannot readily fill with blood following contraction, either (a) the cardiac output becomes diminished, or (b) compensation must ensue to increase the ventricular diastolic pressure to higher levels. When the left ventricular diastolic pressure is elevated, venous pressure in the lungs must also become elevated to maintain forward flow. Increased pulmonary venous pressure results in alveolar edema causing the patient to be short of breath. Phrased differently, left ventricular stiffness makes it more difficult for blood to enter it from the left atrium. As a result, pressure rises in the atrium and is transmitted back to the pulmonary venous system, thereby increasing its hydrostatic pressure and promoting pulmonary edema.
It is important to note that a normal heart that is overfilled with blood may demonstrate increased stiffness and decreased compliance characteristics. This is loosely analogous to a balloon that is over-filled with air (except that the multichambered balloon is filled with viscous blood, not gas). Blowing more air (or blood) into the balloon becomes difficult because the balloon acts stiff and non-compliant at a filling volume it wasn't designed to hold. It may be misguided to classify the volume-overloaded heart as having diastolic dysfunction if it is behaving in a stiff and non-compliant manner. The term diastolic dysfunction should not be applied to the dilated heart. Dilated ("remodeled") hearts have increased volume relative to the amount of diastolic pressure, and therefore have increased (not decreased) distensibility. The term diastolic dysfunction is sometimes erroneously applied in this circumstance, when increased fluid volume retention causes the heart to be over-filled.
Although the term diastolic heart failure is often used when there are signs and symptoms of heart failure with normal left ventricular systolic function, this is not always appropriate. Diastolic function is determined by the relative end diastolic volume in relation to end diastolic pressure, and is therefore independent of left ventricular systolic function. A leftward shift of the end-diastolic pressure-volume relationship (i.e. decreased left ventricular distensibility) can occur both in those with normal and those with decreased left ventricular systolic function. Likewise, heart failure may occur in those with dilated left ventricular and normal systolic function. This is often seen in valvular heart disease and high-output heart failure. Neither of these situations constitutes a diastolic heart abnormality.
Read more about this topic: Diastolic Heart Failure