Heart failure was associated with similar resting characteristic impedance compared to normal subjects (93 vs 85 dyne-sec-cm-5), with exercise imposing no additional increase in hydraulic load.
Observational (n=19)
How does vascular hydraulic load differ between patients with heart failure and normal subjects at rest and during exercise?
In patients with heart failure, the pulsatile component of vascular hydraulic load is similar to normal subjects and does not increase during exercise, suggesting no additional hydraulic load is imposed on the ejecting left ventricle.
Absolute Event Rate: 93% vs 85%
Aortic input impedance and hydraulic power were derived from simultaneous catheter recordings of ascending aortic pressure and velocity in eight normal subjects and 11 age-matched subjects with clinical heart failure secondary to idiopathic congestive cardiomyopathy. Resting data revealed the characteristic depression of cardiac output and elevation of systemic vascular resistance in patients with heart failure. The pulsatile component of vascular hydraulic load, characteristic impedance (Zc), was similar in both groups (Zc normal: 85 +/- 30 dyne-sec-cm-5; Zc cardiomyopathy: 93 +/- 33 dyne-sec-cm-5). The oscillatory fraction of aortic input power in patients with heart failure (14 +/- 4%) was also similar to that of normal subjects (11 +/- 2%). The transition from rest to exercise in patients with heart failure was marked by a decrease in the steady component of arterial hydraulic load, although characteristic impedance did not change. A similar qualitative response occurred in normal subjects, although the systemic vascular resistance during exercise remained above normal in patients with heart failure. The modulus of the first harmonic of impedance significantly decreased during exercise in normal subjects but did not change significantly in patients with heart failure. Furthermore, the modulus of the first harmonic of the reflection coefficient decreased significantly during exercise in normal subjects but did not change in patients with heart failure in spite of systemic vasodilation. Exercise appears to impose no additional increase in vascular hydraulic load on the ejecting left ventricle. The similar aortic characteristic impedances in patients with heart failure and in normal subjects, at rest and during exercise, are consistent with a constant oscillatory fraction of input power.
Laskey et al. (1985) conducted an observational in Heart failure secondary to idiopathic congestive cardiomyopathy (n=19). Exercise vs. Normal subjects was evaluated on Characteristic impedance (Zc). Heart failure was associated with similar resting characteristic impedance compared to normal subjects (93 vs 85 dyne-sec-cm-5), with exercise imposing no additional increase in hydraulic load.