New estimate of valvuloarterial impedance in aortic valve stenosis: A cardiac magnetic resonance study

Abstract

1 J. Magn. Reson. Imaging 2017;45:795-803.

Ageing, Hypertension and Aortic Valve Stenosis: A Conscious Uncoupling

“…Stiffer vessels lead to a faster pulse wave velocity of blood ejected from the heart and earlier timing of wave reflections from vascular branch points, augmenting central aortic pressure and yielding a greater LV afterload. Steady-state load is best represented by systemic vascular resistance (SVR), whereas pulsatile arterial load, is best represented as either Z IN , Z VA-INS or VAL in the setting of AS [5,21,22]. Impedance patterns in younger patients typically show a minimum value of modulus and crossing zero before 3 Hz.…”

“…This represents a significant limitation and one that may be affected by physiological alterations such as heart rate. Z VA may be more accurately described as a resistance index of global LV load during systole [5,20,21,35,45].…”

“…where DP -Q95 is the LV pressure (taken to be the same as carotid tonometric pressure) change from its end-diastolic foot to time of 95% of peak flow (Q -95 ) and MaxG -NET is the maximum gradient calculated across the aortic valve taking into account pressure recovery [21]. Soulat and colleagues found Z VA-INS to be increased in the presence of AS severity and symptoms (Table 1) [21].…”

“…This may lead to an underestimation of forward flow but better accounts for the multiple eccentric flow profiles that are typically observed in patients with AS. In this respect, the two techniques are fundamentally different-Z VA-INS acquires LVOT flow at the level of the LVOT, whereas VAL acquires flow at the level of the MPA in the ascending aorta [21,22].…”

“…Valvulo-arterial impedance (Z VA ) is the most widely adopted index to assess global LV load in patients with AS by Doppler echocardiography. Recent studies have also used non-invasive pressure (from carotid or derived radial applanation tonometry [AT]) and flow velocity (from the ascending aorta on cardiac magnetic resonance [CMR]) [5,[20][21][22] to estimate load in the time or frequency domain [22]. Valvulo-arterial impedance instantaneous (Z VA-INS ) and valvulo-arterial load (VAL) are two, newer indices that measure pulsatile load in patients with AS.…”