pathophysiology of DHF is not completely understood
generally there is impaired left ventricular relaxation, particularly during exercise, probably due to changes in cytoskeletal proteins; and increased left ventricular diastolic stiffness due to increased myocardial mass and fibrosis
subtle abnormalities of systolic function are also frequently present
impaired left ventricular relaxation is greatly exacerbated during exercise
increased large artery stiffness (manifest as systolic hypertension) also appears to play a key role
net effect is impaired LV diastolic filling resulting in higher diastolic pressures with consequent pulmonary congestion and a reduced ability to increase cardiac output
impairment of left ventricular filling can also result in episodes of acute pulmonary oedema ("flash pulmonary oedema") often precipitated by the development of atrial fibrillation and/or fluid retention
Cardiac Physiological Factors
Diastolic Dysfunction
inability to fill the ventricle to an adequate preload volume, diastolic dysfunction is at the core of heart failure with preserved ejection fraction
such as in obesity changes in diastology are a primary dysfunction whereas in others such as prolonged hypertension they reflect other factors that change the loading conditions upon the heart
effect of diastolic dysfunction becomes more pronounced upon exercise:
the filling time remains prolonged, meaning the ventricle cannot completely fill in between beats, further reducing efficiency
Chronotropic Incompetence
inability to increase heart rate on exertion is frequently reported in HFpEF
seems to correlate with feelings of breathlessness
Systolic Dysfunction
though overall ejection fraction is preserved, deficiencies in global longitudinal strain are identifiable, even in those with ejection fraction greater than 55%, indicating subtle systolic impairment
limitations are frequently seen during stress in the HFpEF group
Atrial Dysfunction
where the diastolic function of the left ventricle is impaired, the left atrium gains greater importance and HFpEF patients may be more reliant upon the LA's booster function
loss of atrial contractile function occurs progressively (again, especially under stress) and it has also been observed that HFpEF patients tolerate atrial fibrillation very poorly
when the left atria from patients with HFpEF and HFrEF are compared, there is a greater degree of stiffening in HFpEF, perhaps contributing to the rise in pulmonary pressures
Right Ventricular Dysfunction / Pulmonary Vascular Disease
even discounting the effects of elevated pulmonary artery pressures, there is both systolic and diastolic impairment of the right ventricle, much in the same way as the left
pulmonary vascular resistance itself is also commonly elevated (raising the PA pressures above the results of left atrial hypertension)
Reference:
BHF Factfile 4/2010. Diastolic Heart Failure.
Watson W. Heart Failure with Preserved Ejection Fraction: Pathologies, Aetiology and Directions for Treatment. British Cardiovascular Society Editorials (Accessed 9/11/19)
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