features, advantages and disadvantages of stress echocardiography
Load echocardiography, or, as it is called,
stress echocardiography (stress echocardiography), represents a fusion of the two-dimensional echocardiography
and load test. This method of complex non-invasive diagnostic
that allows detail myocardial ischemia, to determine
pool of stenotic coronary arteries, to identify viable myocardium in the area
postinfarction lesion, to evaluate the inotropic reserve of contractility of the left ventricle
. The main premise underlying the method is the fact that
occurrence of myocardial ischemia is accompanied by a breach of contractility of the left ventricle
.
Prolonged reduction or complete cessation of coronary blood flow
leads to the development of acute myocardial infarction. If a violation of myocardial perfusion
is transitory, it becomes pathological movement
left ventricular wall serves as a marker to determine the localization and
severity of myocardial ischemia.
Violation of left ventricular developed after
reduction of blood flow, but as a asle, before the characteristic changes in
electrocardiogram (ECG) and an angina attack. This ischemic cascade
has been known for several decades. Was to develop a standard assessment protocol
functional ability of the heart in response to physical stress while
monitoring of ECG and hemodynamic parameters.
first foreign and domestic work, studying with
by echocardiography of left ventricular function response to physical exercise (bicycle stress,
isometric) and pharmacological stress (adrenoceptor agonists, cardiac glycosides
, nitrates), emerged in the late 70's. Studies
demonstrated unique capabilities of the method in detecting latent coronary insufficiency
. However, despite the optimistic results, the application of the load
echocardiography in clinical practice for a long time hindered
numerous technical limitations, mainly related to the inability to achieve satisfactory image quality
stasctures of the heart in most patients
on the background load.
Fig. 1. The diagnostic capabilities of some of the methods
studies used for load tests.
Since that time, the method has undergone significant changes.
appearedmoresophisticated ultrasound devices equipped with digital image analysis system
with simultaneous removal of several on-screen projections of the heart
mode cineloop, new stress agents, new protocols
the test. Currently, the method of stress echocardiography was
widespread throughout the world.
Several reasons have necessitated the appearance of such
diagnostic method. Firstly, it is a low predictive value
routine ECG load.
In comparison, the stress echocardiography and myocardial perfusion scintigraphy
(PSM) have significantlymoresensitivity, specificity and
accuracy in detecting latent coronary insufficiency (Fig. 1).
specificity of stress echocardiography according to a series of studies was higher than the MSP.
Secondly, unlike conventional stress tests, stress echocardiography can be used to
baseline ECG changes (blocking leg bundle branch block, left ventricular hypertrophy
, postinfarction changes, the impact of dasg therapy and
etc.), as well as dubious and false-positive cases, the exercise test.
Third, even such a "gold standard" in diagnosing
coronary heart disease (CHD) as X-ray coronary angiography (CAG),
has some limitations: the inability to assess lesions of the distal channel
coronary arteries, the influence of ekstrakoronarnyh factors (eg, myocardial hypertrophy
), poor detection of eccentric stenoses, a general description of the collateral
channel, the relative threshold criteria of stenosis. Finally,
comparing costs of different diagnostic methods, it should be noted that
stress echocardiography in about half the price of PSM and muchmoreeconomical to CAG.
main advantages of stress echocardiography are:
- the possibility of multiple sections of the heart,
visualization of each segment of the left ventricle;
- evaluation of research results in real time with
excellent spatial resolution;
- large selection of echocardiography, indices of regional and global contractile
cardiac function;
- mobility of modern ultrasound devices;
- non-invasive, security studies, good tolerability
patients, the exclusion of ionizing radiation, the ability to conduct research
unlimited number of times;
- a relatively low cost method.
- inability to perform the study in patients with poor-quality
heart visualization;
- the importance of the subjective factor in the processing
results;
- the high cost of training qualified specialists. Advantages and disadvantages of different types of loads
stress echocardiography
the impairment of contractile function of the left ventricle by echocardiography
data, represents one of the most difficult to interpret
problems. Identification and comparative analysis of pathological cardiac motion
wall for a short time (the load) increases the complexity
study, therefore, according to the recommendations of the American and European
Heart Association, stress echocardiography should be done only in specially
equipped laboratories experienced cardiologists, Successful long-course
training on this issue.
Under the concept of "threshold analysis, the results
diagnostic test are significant only when they alter the degree
probability of a diagnosis so that it entails a change
treatment tactics. Themorethe doctor knows about the patient (data from medical history, risk factors
and objective of the survey), the less new information can provide
load test.
It is important to choose for each patient the kind of load,
that will help bring the sample to obtain a diagnostically meaningful results,
avoiding adverse reactions and complications.
| results of the diagnostic test are important only when they alter the likelihood of a diagnosis so much that it entails a change in treatment policy. Themore doctor knows about the patient (data from medical history, risk factors and objective survey), the less new information can provide a load test. |
preferences in the application of various types of loads
stress echocardiography
There are a number loads used during stress echocardiography
:
• physical activity - both horizontal and vertical
bicycle ergometry (BEM), asnning on the treadmill, Work on hand ergometer,
isometric load;
• electrical stimulation of the atria - direct and transesophageal
(TEAC);
• pharmacologic stress - test with dobutamine,
dipyridamole, adenosine, ergonovine, arbutaminom, ATP;
• other types of loads - cold, mental , hyperventilation.
most commonly used horizontal bicycle exercise, treadmill, TEAC,
pharmacological test with dobutamine and dipyridamole. As a synthetic
catecholamines, dobutamine selectively stimulates beta1-receptors, amplifying
inotropic and chronotropic activity of the heart. The rationale for use
dobutamine as a stress agent was that the hemodynamic parameters of its actions
linearly correlated with the dose and concentration in plasma,
half-life is only 2 min, and the administration of small doses (up to 10 - 15 mcg / kg / min),
increasing cardiac contractility, including a "sleeper", identifies
viability of dysfunctional myocardium.
mechanism of action of the arterial vasodilator dipyridamole
based on the phenomenon of intracoronary mezhkoronarnogo and "steal",
occurring with increasing concentration of endogenous adenosine. Preparation
patient for the stress test depends on indication for the study and
kind of load. Maximum sensitivity is achieved by lifting
antianginal dasgs, beta-blockers, calcium antagonists, limiting food intake to
study.
Each load has its advantages and disadvantages. In
table lists recommended types of loads in different clinical
states. The advantage of exercise over the other is their
physiology, well tolerated by patients, as well as the possibility of evaluating
reaction of the cardiovascular system to physical stress, including early
infarction. The disadvantage tredmilovoy stress echocardiography is the difficulty
of ultrasonic testing during the execution load, which reduces its
sensitivity compared with other types of loads. The main difference
pharmacological stress echocardiography is to get the best quality
images of the heart and the ability to detect "sleeper" (hibernating)
infarction, but may also result in various cardiac arrhythmias,
fluctuations in blood pressure. TEAC advantage is short studies,
the possibility of a quick stop, and drawbacks - low specificity and
inconvenience delivered by the patient. Descriptiveness of stress echocardiography, depending on the type of
exercise test is shown in Fig. 2. Stress echocardiography, as
relatively new and promising method of investigation, continues to evolve.
ways this development related to improving the quality of visualization, creation of new
technologies, new approaches of ultrasound (transesophageal echocardiography, contrast echocardiography
), the introduction of new stress agent objectification
processing the information received, etc. The possibility of using stressEhoKG
not limited to the diagnosis of CHD. It is very important
prognosis revaskulyarizatsionnyh activities, which largely depends on the state of viability
dissinergichnogo myocardial inotropic reserve
contractility, particularly in patients with reduced left ventricular ejection fraction
and manifestations of heart failure.
Fig. Figure 3 shows examples stress_EhoKG in normal and stenotic lesions
anterior descending coronary artery.
Fig. 2. Comparative evaluation of different types of informative
loads used in stress_EhoKG.
Fig. 3. Examples of stress echocardiography