Ho-Joong Youn, MD, PhD
Elyse Foster, MD, FACC,

 [Journal of the American Society of Echocardiography]=Through technical
advances in ultrasound imaging, direct visualization of the arteries and
measurement of coronary artery flow is now possible in the majority of
patients.
 Although coronary angiography remains the reference standard for
measuring the anatomic severity of a stenotic lesion, analysis of coronary
artery flow signals and measurement of coronary flow reserve(CFR) provide
physiologic correlates of disease severity. Direct invasive measurements using
Doppler flow wires and catheters have provided a wealth of information on the
pathophysiology of coronary flow dynamics. In clinical practice, these invasive
techniques are rarely applied because of the time and expense required. Thus,
treatment is primarily on the basis of anatomic measures of severity. A reliable
noninvasive method such as those described below could change the
standard on which treatment of coronary disease is based.
 Direct echocardiographic assessment of coronary artery disease was first
described 15 years ago but only in the past few years has there been rapid
progress in the field. In 1987, Fusejima succeeded in measuring coronary
artery flow using Doppler transthoracic echocardiography(TTE) with a 3.75-㎒
transducer. However, clinical application was limited by low success rate;
adequate signals were available in only 35% of control subjects and 50% of
patients with cardiac disease. Subsequent publications by Ross et al, and
Kenny and Shapiro, demonstrated improved blood flow visualization rate using
higher-frequency transducers(≥5㎒).
 With the recent technologic advances in digital imaging along with the
availability of high-frequency transducers and low Nyquist Doppler capability,
visualization of the coronary artery tree has improved. Currently, skilled
operators can be expected to achieve a 90% success rate in visualizing the
coronary arteries. More recently, identification of penetrating intramyocardial
coronary arteries and the internal mammary artery(IMA) flow signals using TTE
has been reported. Although a recent study reports visualization of the distal
right coronary artery(RCA), most of the literature to date has examined flow in
the mid and distal left anterior descending coronary artery(LAD).
TECHNICAL ASPECTS OF
IMAGE ACQUISITION

 LAD
 The proximal LAD is visualized in a modified parasternal short-axis view just
above the level of the aortic valve. A septal branch of LAD may also visualized
in the parasternal short-axis view at the midpapillary muscle level. To visualize
the distal LAD, the optimal acoustic window is found close to the midclavicular
line in the fourth or fifth intercostals space with the patient positioned in the
left lateral decubitus position. The distal LAD can best be identified in the long-
axis view with the ultrasound beam inclined laterally
.
 Coronary blood flow is identified using Doppler color flow mapping with the
Nyquist limit set at 10 to 20㎝/s. Because the coronary artery is not in the
same plane throughout the entire cardiac cycle, because of translational
motion, flow sampling should be optimized during diastole when the position
of the coronary artery is most stable.
 The probe angle and sample volumes should be adjusted to orient the
Doppler ultrasound beam parallel to coronary flow. In normal coronary
arteries, the color and spectral Doppler signals of distal LAD show diastolic
dominant flow with a smaller systolic component. The flow patterns are very
similar to that in the proximal LAD measured using transesophageal Doppler
echocardiography, and the flow patterns obtained invasively using Doppler
guidewires or Doppler catheters. Extravascular compression and lower
coronary perfusion pressure during systole is likely to be responsible for the
lower systolic component.
 RCA
 For imaging peripheral RCA flow, a lower-frequency transducer is required
because of the distance between the transducer and the basal inferior cardiac
wall. The posterior descending branch of distal RCA may be visualized in the 2-
chamber view adjacent to the ostium of the coronary sinus
.
 The patient should be positioned in the left lateral decubitus position. Next,
the ultrasound beam should be inclined laterally or rotated to visualize the
coronary blood flow close to the epicardial layer of the proximal portion or
midportion of the posterior interventricular sulcus under color flow mapping
guidance. In a recent study, coronary flow velocities were measured with
pulsed wave Doppler using minimum angle correction(0~15 degrees).
QUALITATIVE AND QUANTITATIVE EVALUATION OF CORONARY FLOW
 The following Doppler parameters should be examined in the basal state to
detect pathologic flow disturbance.
 Coronary Flow Velocities
 The peak coronary flow velocity during systole and diastole should be
measured in the basal state. The duration of diastolic and systolic flow is
dependent on the heart rate and is another potentially useful measure.
Previous work of the author(H-J.Y.) of control subjects with normal coronary
angiograms and normal left ventricular systolic function showed that the peak
diastolic velocity in the distal LAD was 21.2 ± 7.9㎝/s and the duration of
diastolic coronary artery flow was 58.5 ± 6.4% of the R-R interval at rest
within the range of physiologic heart rates(60~100 bpm). In a study by
Hozumi et al,15 the peak diastolic velocity in the distal LAD was 22.9 ± 6.6㎝/s
in 24 participants without significant LAD stenosis.
 In the presence of coronary artery stenosis, the peak diastolic flow velocities
at the stenotic site are usually increased. Hozumi et al applied pulsed Doppler
to measure the flow velocities at a point proximal to the stenosi(prestenosis)
and at the site of stenosis(aliasing point).
 The mean diastolic velocity at the site of stenosis in the group with
restenosis was significantly higher than that in the group without restenosis
(60.3 ± 21.1㎝/s vs 35.1 ± 7.6㎝/s, P < .01), although prestenotic mean
diastolic velocity did not differ between 2 groups (20.2 ± 3.0㎝/s vs 19.6 ± 2.3
㎝/s).
 Rapid Diastolic Deceleration Slope
 The pressure half-time of the diastolic flow signal in the coronaries has been
studied and should be measured when possible. This parameter may reflect
the integrity of the distal coronary bed and, thus, reflect myocardial viability. In
a study of patients after primary angioplasty, the deceleration half time(DHT)
was steeper for patients with no reflow phenomenon than in those without it
(152 ± 109 vs 395 ± 128 milliseconds, P < .05). The following explanation for
this observation has been proposed.During diastole in control subjects and
those with intact microvasculature, coronary flow fills the intramyocardial blood
pool without an increased distal pressure. Thus, the deceleration slope of the
diastolic flow is gradual.


■ 기사 요지 

 가톨릭의대 성모병원 내과 윤호중 교수의 종설. 동양인으로서는 처음으로 미국 심초음파학
회지(JASE)에 `경흉부심초음파를 이용한 관상동맥 혈류의 관찰`이란 제목으로 게재됐다.
 경흉부 도플러심초음파술(TTDE)은 관상동맥질환의 진단을 위한 새로운 희망으로 떠오르
고 있다.
 고주파 탐촉자와 낮은 Nyquist limit의 특수세팅과 함께 TTDE를 사용할 경우, 관상동맥 혈
류를 관찰할 수 있다. 일정한 경험을 쌓은 후 대상 환자의 90% 이상에서 TTDE를 이용한 관
상동맥 좌전하행지 혈류의 측정과 평가가 가능해졌다. 이러한 관상동맥 혈류측정 방법을 통하
여 ▲흉통을 보이지만 혈관 조영술 상 정상 관상동맥 소견을 보이는 경우 ▲중등도의 관상동
맥협착 ▲관상동맥 확장술을 시도했거나 이로 인한 치료효과가 불확실환 환자들의 진단 및 임
상치료에 도움을 줄 수 있다.
정리·이상돈 기자
sdlee@kimsonline.co.kr
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