Page 179 - Clinical Small Animal Internal Medicine

16 Imaging in Cardiovascular Disease 147

cardiomyopathy, respectively. Whatever the cause,
VetBooks.ir (b) aortic stenosis produces an accelerated turbulent sys-
tolic aortic flow, with similar spectral and color flow
Doppler characteristics to those described for pulmo-
nic stenosis (Figure 16.27).

Aortic Insufficiency
Common causes of aortic insufficiency include infec-
tious endocarditis, congenital abnormal aortic valve
(most often in association with subaortic stenosis),
and degenerative valvular disease. Color flow Doppler
mode criteria indicating severe aortic regurgitation
are large insufficiency jet size, compared to the left
ventricular outflow tract, and high extension of the
(c) diastolic jet within the left ventricle, that is, beyond
the mitral leaflets tips. Severe aortic insufficiency also
causes a rapid deceleration of the diastolic Doppler
CW signal, owing to the marked decrease in the dias-
tolic pressure gradient across the abnormal aortic
valve over time. Examples of mild and severe aortic
regurgitation jets are presented in Figures 16.27c
and 16.28.

Abnormal Mitral Flow Patterns
Alteration in Diastolic Transmitral Inflow
Alteration in left ventricular diastolic function may
induce transmitral inflow changes, including delayed
relaxation and restrictive transmitral flow patterns
Figure 16.16 (Continued) (Figures 16.29a and 16.29b). Impaired relaxation may
cause lower E wave velocity and higher A wave velocity
(E/A <1), as well as prolonged isovolumic relaxation
Nonphysiologic Pulmonary Regurgitations time, reduced flow acceleration time, and prolonged
Pulmonary regurgitation is often associated with congen- deceleration time (Figure 16.29a). However, in the case
ital pulmonic stenosis, because of the abnormally thic- of delayed relaxation associated with increased left
kened and irregular pulmonary leaflets (Figure 16.26c). atrial pressure and left ventricular stiffness, the trans-
Its severity may be mildly to moderately increased in mitral inflow may be normal (also called the “pseudo-
patients with pulmonary stenosis that have undergone normal” transmitral flow pattern). The restrictive
balloon valvuloplasty. In contrast, pulmonary regur- filling pattern is characterized by a shortened isovolu-
gitation caused by infectious endocarditis is a very rare mic relaxation time, a tall narrow mitral E wave, and a
condition. small A wave (Figure 16.29b).
Physiologic diastolic pulmonary regurgitation becomes Diastolic transmitral inflow is also altered in the case
turbulent as well as of increased velocity, duration and of congenital or acquired (endocarditis) mitral stenosis
extension in the case of diastolic pulmonary hyperten- (Figures 16.29c and 16.29d).
sion (see Figure 16.25 and above paragraph). In dogs with degenerative mitral valve disease, a high‐
velocity E wave (>1.5 m/s) suggests elevated left atrial
pressure and therefore severe mitral regurgitation.
Abnormal Aortic Flow Patterns
Alterations in Systolic Aortic Flow
Aortic stenosis may result from infectious endocardi- Mitral Regurgitation
tis. However, the two most common causes of systolic One of the methods commonly used to assess mitral
aortic flow obstruction in the dog and cat are cong- regurgitation severity in dogs with mitral valve dysplasia
enital aortic stenosis and obstructive hypertrophic or degenerative mitral valve disease consists of