Diastolic flow velocity

Fig. 19.5a,b. Sonography in haemolytic uremic syndrome (HUS), a Severe thickening of the howel wall caused by severe E. coli enteritis (extended view sonography with tissue harmonic imaging), b Alteration of renal parenchymal echogenicity in HUS, with duplex Doppler sonography showing elevated RI (RI = 0,82) due to reduced diastolic flow velocity and increased renal vascular resistance... 

RI is calculated by the formula RI= (Vg-V )/Vg, where Vg is maximal systolic flow velocity and is end-diastolic flow velocity. 

Appleton CP, Basnight MA, Gonzalez MS. Diastolic mitral regurgitation with atrioventricular conduction abnormalities relation of mitral flow velocity to transmittal pressure gradients in conscious dogs. J. Am. Coll. Cardiol. 1991 18 843-9. 

The Doppler spectrum of the normal hepatic artery shows low vascular resistance and continuous diastolic flow there is a rapid systolic upstroke with acceleration time inferior to 80 ms the resistive index [(peak systolic velocity - peak diastolic veloc-ity)/peak systolic velocity] should be between 0.5 and 0.7 (Crossin et al. 2003) (Fig. 4.2.17). Doppler criteria for diagnosing a significant hepatic artery complication are peak systolic velocities greater than 200cm/s, focal increase in velocity greater than threefold, resistive index less than 0.5, and acceleration time greater than 80 ms (tardus-parvus... 

Boskovski MT, Shmuylovich L, and Kovacs SJ. Transmitral flow velocity-contour variation after premature ventricular contractions A novel test of the load-independent index of diastolic filling. Ultrasound in Medicine and Biology 2008 34 1901-8. 

Courtois M, Kovics SJ, and Ludbrook PA. Transmitral pressiu-e-flow velocity relation. Importance of regional pressure gradients in the left ventricle during diastole. Circulation 1988 78 661-71. de Tombe PP. Cardiac myofilaments Mechanics and regulation. Journal of Biomechanics 2003 36 721-30. 

Velocity varies across the vessel due to viscous and inertial effects as mentioned earher. The velocities in Figure 56.3 were measured at one point in the artery. Velocity profiles are complex because the flow is pulsatile and vessels are elastic, curved, and tapered. Profiles measured in the thoracic aorta of a dog at normal arterial pressure and cardiac output are shown in Figure 56.4. Backflow occurs during diastole, and profiles are flattened even during peak systohc flow. The shape of the profiles varies considerably with mean aortic pressure and cardiac output [Ling et al., 1973]. 

Dorsal-cavernosal anastomosis is commonly detected in patients after pharmacologically induced erection, independently of the nature of the erectile dysfunction. The flow direction is normally from the dorsal artery to the cavernosal and the end diastolic velocity is always high and not influenced by the intracorporeal pressure. 

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