Validation Study of Pulse Wave Velocity and Augmentation Index in Atrial Fibrillation

In recent years the role of arterial stiffness in the development of cardiovascular diseases has garnered attention. Indeed, arterial stiffness is now well accepted as one of the most important determinants of increasing systolic and pulse pressure thus playing a germane role in the risk of stroke and myocardial infarction. Longitudinal epidemiological studies have demonstrated the independent predictive value of arterial stiffness for cardiovascular events after adjustment for classical cardiovascular risk factors. Arterial stiffness is now a recognized intermediate endpoint for cardiovascular events. The pressure wave speed in large arteries is directly related to square root of the elastic modulus of the arterial wall (Moens-Korteweg Equation). Carotid-femoral PWV is considered the gold standard method for assessing aortic stiffness. The stiffness gradient along the aorta and central arteries, local arterial branchings and narrowing of the arterial lumen cause partial reflections of forward pressure waves traveling back to the central aorta. Forward and reflected pressure waves overlap, and the final amplitude and shape of the pulse pressure wave are determined by the phase timing of these component waves. In the aorta, forward and reflected waves are not in phase. In subjects with low PWV, reflected waves reach the central arteries during late-systole and diastole, increasing the aortic pressure in early diastole, which is physiologically advantageous. With increasing PWV, the reflected waves return earlier and impact on the central arteries during systole, thereby augmenting systolic and left ventricular pressure. This is why increasing PWV is accompanied by increasing AIx (defined as the difference between the second and first systolic pressure peak) and central PP. AIx and central PP depend on the speed of wave travel, the amplitude of reflected wave and the duration and pattern of ventricular ejection, especially with respect to change in heart rate and ventricular contractility. Where PWV is considered a direct measure of arterial stiffness, central PP and AIx are only indirect, surrogate measures. However, they provide additional information concerning wave reflections. Whether PWV, AIx and central PP measurements are influenced by the presence of AF is unknown. Studying AF patients before and after elective electrical cardioversion offers an appropriate setting to evaluate the effect of heart rate and rhytm on PWV, AIx and central PP. Patient specific confounding factors are minimized because each patient serves as its own control.