Page 148 - Feline Cardiology

Chapter 11: Hypertrophic Cardiomyopathy 147

5 30
Volume Derivative
End Systole
4.5 20 MR EFR
MR AFR
4 10 End Diastole
Volume [cm 3 ] 3.5 Volume dV/dt [cm 3 /s] 0

3 End Systole –10
End Diastole
MidPoint
2.5 –20

2 –30 Cardiomyopathies
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
A Time [sec] C Time [sec]

30
Volume Derivative
End Systole
20 MR EFR
MR AFR
End Diastole
10
dV/dt [cm 3 /s] 0

–10

–20

–30
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
B Time [sec]
Figure 11.24. Assessment of diastolic left ventricular function by cardiac magnetic resonance imaging and Simpson’s rule. Left ven-
tricular volume is summated throughout the cardiac cycle and plotted versus time (A). End-systolic and end-diastolic volumes, stroke
volume, cardiac output, cardiac index, and early filling percentage are then calculated. The first derivative is obtained and plotted as
dV/dT (B) to determine peak diastolic filling rate, mean diastolic filling rate, early diastolic filling rate (EFR), and late diastolic filling rate
(AFR). Normally, the peak diastolic filling rate occurs in early diastole. Both (B) and (C) are obtained from cats with HCM. The cat in (B) has
a normal diastolic filling profile where the peak diastolic filling rate is greatest in early diastole, but the cat in (C) has abnormal diastolic
function, with equal early and late diastolic filling rates.

are acquired from only one slice placed below and paral- and myocardial tagging to assess regional myocardial
lel to the mitral annulus. Velocity encoded cine may also function and quantify myocardial strain and torsion
be applied to quantify myocardial velocities over the (Rathi et al. 2004). Early diastolic impairment (i.e., a
cardiac cycle, and myocardial strain rates may be calcu- reduced early diastolic strain rate) was identified in
lated. There are no velocity encoded cine studies evaluat- humans with familial HCM using cMRI tagging (Ennis
ing diastolic function in people with HCM. The majority et al. 2003). Impaired regional LV contractility and sys-
of the velocity encoded cine studies have involved aortic tolic LV wall asynchrony has also been identified in
stenosis or aortic insufficiency. In patients with aortic people with HCM using cMRI tagging (Ennis et al. 2003;
stenosis and compensatory concentric LV hypertrophy, Mishiro et al. 1999). Overall, there are limited potential
velocity encoded cine has been used to detect an increased clinical applications for the use of cMRI to assess dia-
atrial contribution to LV filling, indicating a restrictive stolic function at present, both because of the general
pattern of diastolic dysfunction (Hartiala et al. 1994). limitations of cardiac MRI in veterinary patients and
Other advanced cMRI techniques for quantification because of effects of general anesthesia on cardiac
of diastolic function include regional wall thinning rate function.