Atrial pacing to 100 and 120 min(-1) demonstrated that frequency-dependent upregulation of cardiac output is blunted in HFNEF due to limited relaxation reserve and increased passive stiffness.
Observational (n=24)
Does increasing heart rate via atrial pacing impair relaxation and cardiac output augmentation in patients with HFNEF compared to age-matched controls?
In patients with HFNEF, increasing heart rate blunts cardiac output augmentation due to impaired relaxation reserve and increased passive stiffness, providing a pathophysiological mechanism for exercise intolerance.
AIMS: We tested the hypothesis that, in heart failure with normal ejection fraction (HFNEF), diastolic dysfunction is accentuated at increasing heart rates, and this contributes to impaired frequency-dependent augmentation of cardiac output. METHODS AND RESULTS: In 17 patients with HFNEF (median age 69 years, 13 female) and seven age-matched control patients, systolic and diastolic function was analysed by pressure-volume loops at baseline heart rate and during atrial pacing to 100 and 120 min(-1). At baseline, relaxation was prolonged and end-diastolic left ventricular stiffness was higher in HFNEF, whereas all parameters of systolic function were not different from control patients. This resulted in smaller end-diastolic volumes, higher end-diastolic pressure, and a lower stroke volume and cardiac index in HFNEF vs. control patients. During pacing, frequency-dependent upregulation of contractility indices (+dP/dt(max) and Ees) occurred similarly in HFNEF and control patients, but frequency-dependent acceleration of relaxation (dP/dt(min)) was blunted in HFNEF. In HFNEF, end-diastolic volume and stroke volume decreased with higher heart rates while both remained unchanged in control patients. CONCLUSION: In HFNEF, frequency-dependent upregulation of cardiac output is blunted. This results from progressive volume unloading of the left ventricle due to limited relaxation reserve in combination with increased LV passive stiffness, despite preserved force-frequency relation.
Wachter et al. (2009) conducted an observational in Heart failure with normal ejection fraction (HFNEF) (n=24). Atrial pacing vs. Age-matched control patients was evaluated on Systolic and diastolic function analysed by pressure-volume loops. Atrial pacing to 100 and 120 min(-1) demonstrated that frequency-dependent upregulation of cardiac output is blunted in HFNEF due to limited relaxation reserve and increased passive stiffness.