Impact of Arterial Load and Loading Sequence on Left Ventricular Tissue Velocities in Humans
Barry A. Borlaug, MD*,*,
Vojtech Melenovsky, MD, PhD ,1,
Margaret M. Redfield, MD, FACC*,
Kristy Kessler, RN, BSN,
Hyuk-Jae Chang, MD, PhD,
Theodore P. Abraham, MD, FACC and
David A. Kass, MD, FACC
* Mayo Clinic College of Medicine, Rochester, Minnesota
Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland.
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Figure 1 Components of Arterial Load and Loading Sequence
(A) Net/total afterload is effective arterial elastance (Ea), the ratio of left ventricular (LV) end-systolic pressure (ESP) to stroke volume (SV). The red dotted lines shows an increase in Ea. (B) Characteristic impedance (Zc) is the mean of impedance moduli at harmonics 2 to 12 Hz. The Zc is elevated with aging and hypertension. (C) Late-systolic load is determined by the ratio of the augmented pressure (AP) to pulse pressure (PP): the augmentation index (AI). (D) The last one-third of the area under the pulse pressure-time integral curve (PTI3) is another measure of late-systolic load.
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Figure 2 Relationships between E' and Total, Nonpulsatile, and Early/Proximal Arterial Load
The tissue Doppler echocardiography early-diastolic velocity (E') varies inversely with mean (systemic vascular resistance index [SVRI]), net (arterial elastance [Ea]), and early (characteristic impedance [Zc]) left ventricular afterload, as well as aortic stiffness (carotid-femoral pulse wave velocity [PWV]). Dotted lines show 95% confidence bands for the regression slopes.
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Figure 3 Relationships Between E', Compliance, and Late-Systolic Load
The association between tissue Doppler echocardiography early-diastolic velocity (E') and afterload is strongest for arterial compliance and late-systolic load (carotid augmentation index [cAI], radial augmentation index [rAI], and last tertile of central pulse pressure-time integral [PTI]), suggesting that these factors may particularly affect early relaxation. Dotted lines show 95% confidence bands for the regression slopes. Ca = total arterial compliance.
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