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European Journal of Echocardiography 2004 5(1):25-33; doi:10.1016/S1525-2167(03)00047-7
© 2004 by European Society of Cardiology
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Copyright © 2003, The European Society of Cardiology

Simultaneous transesophageal Doppler assessment of coronary flow reserve in the left anterior descending artery and coronary sinus allows differentiation between proximal and non-proximal left anterior descending artery stenoses

A.V. Vrublevsky*, A.A. Boshchenko and R.S. Karpov

Cardiology Research Institute, Russian Academy of Medical Sciences, Siberian Branch, Tomsk, Russia

Received 28 January 2003; received in revised form 26 May 2003; accepted after revision 28 May 2003.

* Corresponding author. Department of Atherosclerosis and Coronary Artery Disease, Cardiology Research Institute, Russian Academy of Medical Sciences, Siberian Branch, Kievskaya Street, 111a, Tomsk 634012, Russia. Tel.: +7-382-2-55-34-45; fax: +7-382-2-55-50-57. alexvr{at}mail.tomsknet.ru


   Abstract
Top
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusions
 References
 
Aim and methods: The role of simultaneous transesophageal Doppler assessment of coronary flow reserve (CFR) in the left anterior descending artery (LAD) and coronary sinus (CS) in the diagnostics of hemodynamically significant LAD stenoses of various localization was studied in 16 CAD patients with angiographically proven <50% stenotic atherosclerosis of the LAD (nine—in the proximal third, seven—in the mid and/or distal third) and 23 healthy volunteers (all men). Dipyridamole was used as a stress agent. The diastolic phase of coronary flow in the LAD and the antegrade phase of coronary flow in the CS were analyzed. CFR in the LAD and CS was calculated in two ways: one—as ratio of peak hyperemic flow velocity to the peak baseline blood flow velocity (CFR by Vp); two—as ratio of volume hyperemic blood flow velocity to the volume baseline blood flow velocity (CFR by VBF). The level of the CFR <2 in both ways of calculation was diagnosed as reduced.

Results: It was found that in CAD patients with LAD proximal stenosis the values of CFR in the LAD were significantly lower than those in healthy individuals by both Vp (1.87 ± 0.43 and 3.54 ± 0.82; P<0.001) and VBF (1.79 ± 0.77 and 3.85 ± 1.25; P<0.01). In proximal stenosis CFR in the LAD by Vp was significantly lower than that in non-proximal stenosis (1.87 ± 0.43 and 3.31 ± 1.44; P<0.05). Sensitivity and specificity of CFR <2 in the LAD by Vp in the diagnostics of LAD proximal stenosis were 56% and 97%, respectively; and CFR <2 in the LAD by VBF—89% and 93%, respectively. In CAD patients with both proximal and non-proximal LAD stenoses CFR in the CS by Vp was significantly lower than that in healthy volunteers and was 1.74 ± 0.53, 1.63 ± 0.30 and 2.56 ± 0.87; P<0.05, respectively. Sensitivity and specificity of CFR <2 in the CS by Vp in the diagnostics of hemodynamically significant LAD stenoses were 75% and 70%, respectively. The values of CFR in the CS by VBF in CAD patients and healthy volunteers did not differ significantly.

Conclusions: Thus, simultaneous evaluation of CFR in the LAD and CS makes it possible to diagnose hemodynamically significant LAD stenoses and to differentiate between proximal and non-proximal impairments.

Keywords: coronary flow reserve; left anterior descending artery; coronary sinus; transesophageal echocardiography; coronary atherosclerosis


   1. Introduction
Top
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 5. Conclusions
 References
 
Over the last decade, the interest of clinicians and pathophysiologists in the problem of coronary flow reserve (CFR) has not decreased. Assessment of CFR in atherosclerosis has become an essential supplement to the findings of coronary angiography as it enables to evaluate the degree of coronary functional impairment.1,2 Some researchers consider CFR to be an integral index of the total atherosclerotic lesion of the cardiac arteries, which, in dynamic observation, can be a highly sensitive and specific marker of therapeutical, cardiosurgical and roentgenological intervention effectiveness.1–4

Recent publications extensively discuss the diagnostic potentials of new technologies in the assessment of CFR. In practical cardiology preference is given to noninvasive techniques because of minimum complications, lower cost and the possibility of dynamic reevaluations.4,5 Numerous clinical studies have shown that transesophageal Doppler echocardiography in the evaluation of coronary arteries is, at present, one of the most reliable methods allowing us to noninvasively estimate the coronary blood flow reserve.6–11

The clinical significance of the left anterior descending coronary artery (LAD) atherosclerotic lesion is outstanding. In our previous work12 we demonstrated the possibilities of transesophageal Doppler study with application of a modified equation of the flow continuity in quantitative diagnostics of LAD proximal stenoses. However, transesophageal Doppler fails to visualize the mid and distal parts of the LAD and to calculate stenoses of these localizations. Intracoronary Doppler studies showed that in hemodynamically significant LAD stenoses coronary blood flow reserve in the vessel was sharply reduced.1,3 Recent data provide evidence of the difficulties of differentiating between proximal and non-proximal LAD stenoses according to the findings of transesophageal Doppler assessment of CFR only in the proximal part of this artery.7,10 Zehetgruber et al.6 found that in CAD patients with distal LAD stenosis the values of CFR in the coronary sinus (CS) calculated by transesophageal Doppler were highly correlated with the parameters of CFR in the LAD stenotic zone determined by intracoronary measurements. Thus, theoretically, simultaneous evaluation of CFR in the LAD and CS is expected to be informative for the diagnostics of LAD stenoses of any localization.

The aim of our study was to determine the value of simultaneous assessment of CFR in the LAD and CS in the diagnostics of hemodynamically significant LAD stenoses of various localization as well as to develop the Doppler criteria for differentiating the LAD impairment level.


   2. Methods
Top
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 5. Conclusions
 References
 
2.1 Study group
We have assessed 39 men who gave an informed consent to participate in the study. The main group consisted of 16 CAD patients (mean age 47 ± 7 years) with stable angina of I–III functional classes or silent myocardial ischemia and with angiographically proven isolated LAD stenosis (>50% diameter stenosis) of various localization. For this study the following definitions were used: the proximal LAD stenosis group (group 1, n = 9) was defined as having <50% stenosis proximal to the first diagonal branch. The mid/distal-LAD stenosis group (group 2, n = 7) was defined as having <50% stenosis distal to the first diagonal branch. All CAD patients had a sinus rhythm, normal wall thickness and function of the left and right ventricles, normal right ventricular systolic pressure, mitral and tricuspid valvular regurgitation less than grade 2, arterial normotension (blood pressure <130/90 mmHg). CAD patients with valvular disease, cardiomyopathy, diabetes mellitus, esophageal, gastric or severe pulmonary diseases were excluded from the study. The control group (group 3) consisted of 23 healthy volunteers with chest pain (mean age 35 ± 5 years) who had angiographically normal coronary arteries. The research protocol was approved by the Ethical Committee of the Tomsk Cardiology Research Institute, Russia.

2.2 Coronary angiography
Coronary angiography was performed via femoral approach according to Judkins' standard method (1967) using COROSKOP Plus angiographic complex (Siemens, Germany). Angiographic measurements of stenosis severity were made.

2.3 Multiplane transesophageal echocardiography
All patients underwent transesophageal echocardiography within a week after coronary angiography. They had continuous electrocardiographic (ECG) monitoring and every 2 min blood pressure monitoring. A 7–4 MHz multiplane probe with ultrasound diagnostic systems HDI 5000 SonoCT or Ultramark 9 HDI CV (Philips-ATL, Germany–USA) was used. All kinds of medication, except sublingual nitroglycerine, were discontinued 48 h before the study. The investigators were ignorant of coronary angiography data.

Esophageal intubation was made in the left lateral decubitus position after slight sedation (0.5% sibazone in 0.5 mg boluses) and oropharyngeal local anesthesia (2% dicaine). The transducer was advanced to a standard mid-esophageal position. The proximal left coronary artery system was imaged in transversal plane, rotation of the transducer array (from 0° to 50°) and flexion were adjusted to image the proximal LAD optimally. The pulsed-wave sample volume was placed over the proximal portion of the LAD, spectral recordings of the flow were made and end diastolic diameter of the LAD before the P wave on ECG was measured. The sampling site depended on the maximum peak diastolic velocity site. The CS was imaged in four-chamber plane with the rotation of the transducer array from 0° to 30°. A good quality image of the CS existed during the entire cardiocycle. The CS diameter was measured at a 1 cm distance from the mouth in the end diastolic phase before the P wave on ECG. The pulsed-wave sample volume was placed at a 1 cm distance from the mouth, and spectral recordings of the flow were made. The Doppler angle between ultrasound beam and vessels did not exceed 30°. After baseline recording of flows and measurement of diameters, dipyridamole (Persantin, Boehringer Ingelheim, Austria; 0.56 mg/kg) was infused over a 4-min period. An additional infusion of dipyridamole (0.28 mg/kg over a 2-min period) was used if heart rate (HR) increased <10% from the baseline.14 Two minutes after the end of the infusion, hyperemic spectral profiles in the LAD and CS were recorded and diameters of the vessels were measured. All images were recorded for playback analysis and were later measured off-line.

Systolic (SBP) and diastolic blood pressure (DBP) and HR were automatically measured and digitally displayed by Bosotron 2 (Bosch + Sohn, Germany).

2.4 Analysis of coronary blood flow in the left anterior descending artery and coronary sinus
The diastolic phase of coronary flow in the LAD and the antegrade phase of coronary flow in the CS were analyzed. The peak (Vp, cm/s) and mean (Vm, cm/s) flow velocities and the velocity time integrals (VTI, cm) were determined. The volume blood flow velocity (VBF, ml/min) in the LAD and CS was calculated according to the formula13: VBF, ml/min {pi} x D2/4 x VTI x HR, where D, cm—diameter of the LAD or CS. The average value of three spectral and planimetric envelopes was used.

2.5 Coronary flow reserve
CFR in the LAD and CS was calculated in two ways: one—as ratio of peak hyperemic blood flow velocity to the peak baseline blood flow velocity (CFR by Vp); two—as ratio of volume hyperemic blood flow velocity to the volume baseline blood flow velocity (CFR by VBF). The level of CFR <2 in both ways of calculation was diagnosed as reduced.10,11

2.6 Statistical analysis
The statistical analysis of the findings was performed by STATISTICA software package, version 6.0 (StatSoft Inc, USA). The data were analyzed by one-way analysis of variance (baseline-hyperemia test in the group) and Student–Scheffi post-testing. The data are expressed as mean value ± SD.


   3. Results
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 5. Conclusions
 References
 
3.1 Visualization of the left anterior descending artery and coronary sinus
Adequate gray-scale visualization of the LAD proximal third and CS as well as a good spectral Doppler flow in these vessels were obtained in 100% CAD patients and 100% healthy volunteers.

3.2 Coronary flow reserve in the left anterior descending artery
Baseline HR, SBP, DBP, LAD diameter and Doppler indexes of coronary blood flow did not differ significantly in CAD patients and healthy volunteers (Table 1). However, group 1 showed a pronounced trend to an increase of velocity characteristics of coronary blood flow depending on the position of strobe volume in the stenotic zone. At peak of dipyridamole action the HR and SBP increase was uniform in all evaluated individuals, the DBP parameters did not differ significantly.


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  		Table 1 Parameters of CFR, systemic hemodynamics and Doppler parameters of the coronary blood flow in the LAD and CS in CAD patients and healthy volunteers at rest and after dipyridamole infusion

 
A significant increase of the LAD diameter during dipyridamole stress test was observed only in healthy volunteers. In the groups of CAD patients the LAD diameter increase was insignificant. At peak of dipyridamole action a significant increase of linear and VBF in the LAD was observed both in CAD patients and healthy volunteers. However, in group 1 of CAD patients the increase of velocity and volume characteristics of coronary blood flow was less marked, and there was no significant increase of VTI. Consequently, CAD patients with proximal stenoses showed a significantly lower CFR by both Vp and VBF in the LAD compared to healthy volunteers (Table 1). In addition, in CAD patients with proximal stenoses CFR calculated by Vp in the LAD was much lower than that in CAD patients with non-proximal stenoses. In patients with non-proximal stenoses and healthy volunteers the CFR indexes by both Vp and VBF in the LAD did not differ significantly.

By individual analysis CFR <2 calculated by Vp in the LAD was registered in five of nine CAD patients in group 1, in one of seven patients in the group 2 and in none of healthy volunteers. At the same time, CFR <2 calculated by VBF in the LAD was observed in 8 of 9 CAD patients in group 1, in 1 of 7 patients in group 2 and in 1 of 23 healthy volunteers. Thus, sensitivity and specificity of CFR <2 by Vp and VBF in the LAD in the diagnostics of LAD proximal stenoses were calculated as 56%, 97% and 89%, 93%, respectively. We have revealed a reverse correlation between the CFR indexes by Vp, CFR by VBF in the LAD and the maximum percentage of LAD proximal third stenosis according to coronary angiography findings, which were: r = –0.61, P<0.001 (Fig. 1) and r = –0.51, P<0.01, respectively.


Figure 1
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  		Figure 1 Left panel, a correlation between the maximum percentage of the proximal LAD stenosis according to coronary angiography findings and CFR indexes by Vp in the LAD. Right panel, a correlation between the maximum percentage of the proximal or non-proximal LAD stenosis according to coronary angiography findings and CFR indexes by Vp in the CS. Vp—peak diastolic velocity of coronary blood flow in the LAD and peak velocity of the antegrade phase of coronary blood flow in the CS.

 
3.3 Coronary flow reserve in the coronary sinus
At baseline the CS diameter and its coronary blood flow Doppler indexes in CAD patients of both groups and healthy volunteers did not differ significantly (Table 1). However, in healthy volunteers the antegrade wave was presented by systolo-diastolic flow with the prevalence of a systolic phase, while in CAD patients—by either biphasic flow with the prevalence of a diastolic phase or monophasic diastolic flow. A significant increase of the CS diameter at peak of dipyridamole action was observed in healthy volunteers and CAD patients of group 2. The CS diameter in CAD patients of group 1 did not differ significantly. During dipyridamole stress test CAD patients of both groups and healthy individuals showed a significant increase of linear and VBF in the CS. However, in CAD patients of both groups the increase of velocity and volume characteristics of coronary blood flow was less marked than that in healthy individuals. Hence, in CAD patients of both groups CFR in the CS calculated by Vp was significantly less than in healthy volunteers (Table 1). At the same time, no significant differences of CFR in the CS by VBF were revealed in CAD patients of both groups in comparison with that of healthy volunteers.

By individual analysis it was found that CFR <2 in the CS by Vp was registered in 6 of 9 CAD patients in group 1, in 6 of 7 patients in group 2 and in 7 of 23 healthy individuals. At the same time, CFR <2 in the CS by VBF was registered only in 4 of 9 CAD patients of group 1, 2 of 7 patients of group 2 and 1 of 23 healthy individuals. Thus, sensitivity and specificity of CFR <2 in the CS calculated by Vp and VBF in the diagnostics of hemodynamically significant LAD stenoses of any localization were 75%, 70% and 38%, 96%, respectively. We have revealed a reverse correlation between the CFR indexes by Vp, CFR by VBF in the CS and the maximum percentage of proximal or non-proximal LAD stenosis according to coronary angiography findings, which were: r = –0.52, P = 0.001 (Fig. 1) and r = –0.45, P<0.01, respectively.

Fig. 2 illustrates adequate CFR in the LAD and CS in a healthy volunteer during dipyridamole test.


Figure 2
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  		Figure 2 Normal CFR in the LAD and CS in a healthy volunteer. Dipyridamole test. (a) Doppler spectrum of coronary blood flow in the LAD before dipyridamole infusion. (b) Doppler spectrum of coronary blood flow in the LAD after dipyridamole infusion. CFR—4.3. (c) Doppler spectrum of coronary blood flow in the CS before dipyridamole infusion. (d) Doppler spectrum of coronary blood flow in the CS after dipyridamole infusion. CFR—3.1. Vp—peak diastolic velocity of coronary blood flow in the LAD and peak velocity of the antegrade phase of coronary blood flow in the CS.

 
Figs. 3 and 4Go obviously demonstrate the role of decreased CFR in the LAD and CS in the diagnostics of proximal and non-proximal hemodynamically significant LAD stenoses.


Figure 3
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  		Figure 3 CFR in a CAD patient with 60% proximal stenosis of the LAD. Dipyridamole test. (a) Doppler spectrum of coronary blood flow in the LAD before dipyridamole infusion. (b) Doppler spectrum of coronary blood flow in the LAD after dipyridamole infusion. Decreased CFR—1.3. (c) Doppler spectrum of coronary blood flow in the CS before dipyridamole infusion. (d) Doppler spectrum of coronary blood flow in the CS after dipyridamole infusion. Decreased coronary flow reserve—0.9. Vp—peak diastolic velocity of coronary blood flow in the LAD and peak velocity of the antegrade phase of coronary blood flow in the CS.

 


Figure 4
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  		Figure 4 CFR in a CAD patient with 70% non-proximal stenosis of the LAD. Dipyridamole test. (a) Doppler spectrum of coronary blood flow in the LAD dipyridamole infusion. (b) Doppler spectrum of coronary blood flow in the LAD dipyridamole infusion. Normal CFR—3.8. (c) Doppler spectrum of coronary blood flow in the CS before dipyridamole infusion. (d) Doppler spectrum of coronary blood flow in the CS after dipyridamole infusion. Decreased CFR—1.2. Vp—peak diastolic velocity of coronary blood flow in the LAD and peak velocity of the antegrade phase of coronary blood flow in the CS.

 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
5. Conclusions
 References
 
Until recently, an accurate topical diagnosis of coronary artery stenotic atherosclerosis with determination of CFR has been possible with the help of invasive evaluation methods only. However, over the last decade priorities have been given to up-to-date noninvasive techniques. Introduction of transesophageal Doppler study of coronary arteries into clinical practice with the application of a modified equation of the flow continuity has made it possible to accurately calculate the stenosis percentage of the left main coronary artery and proximal segments of the left anterior descending, circumflex and right coronary arteries.12 But, at present, there is one more Doppler approach to the diagnostics of hemodynamically significant stenoses of coronary arteries, which is based on determination of CFR.7,10

CFR is known to be defined as the ability of coronary vessels to increase the volume blood flow adjusting it to the myocardium demands for oxygen and energy substrates in a definite hemodynamic situation.15 Invasive assessment of coronary hemodynamics with the use of dipyridamole and adenosine shows that adequate vasodilatation of healthy coronary system provides CFR level <2.4,5,10,11 In Doppler evaluation CFR is generally defined as ratio of stress-induced peak diastolic velocity of the coronary blood flow to the baseline.10,11 Vasodilatation potentials of the coronary artery in the zone of hemodynamically significant stenosis are reduced and even completely exhausted. Consequently, in Doppler assessment no adequate increase of coronary blood flow velocity in response to pharmacological stress agents is observed. There is a reverse correlation between the coronary artery stenosis percentage and CFR level.2,3

Many authors have reported high sensitivity and specificity of transesophageal Doppler assessment of CFR in the LAD in the diagnostics of LAD proximal stenoses.7,10 Doppler study of CFR in the LAD via transesophageal approach is most correct methodically as it permits to set the strobe volume practically parallel to the blood flow. Zehetgruber et al.6 have confirmed a high accuracy of transesophageal Doppler evaluation of CFR in LAD proximal stenoses by revealing a significant correlation between CFR in LAD proximal stenoses determined by both Doppler study and direct measurements. At the same time, transesophageal Doppler of coronary arteries fails to visualize the mid and distal segments of the coronary system. However, Zehetgruber et al.6 have found a high correlation of CFR in the CS, calculated by transesophageal Doppler findings, and CFR values in the CS in both the proximal and distal segments of the LAD determined by direct measurements. Hence, we hypothesized that simultaneous evaluation of CFR in the LAD and CS might be highly informative for the diagnostics of hemodynamically significant LAD stenoses of various localizations. Since CS is a main venous collector of the left coronary artery system,16 a decrease of CFR in the LAD proximal third is likely to be an evidence of proximal hemodynamically significant LAD stenoses, while a decrease of CFR in the CS is a sign of both proximal and distal impairments of this artery.

Analyzing the parameters of the LAD coronary blood flow in the dynamics of dipyridamole stress test we have found that the vascular wall rigidity in LAD proximal stenosis does not provide an adequate vasodilatation and increase of the blood flow velocity characteristics. Therefore, in the group of CAD patients with marked proximal LAD stenosis the values of CFR in the LAD by both Vp and VBF were much lower compared to those in healthy volunteers. It was also confirmed by a reverse correlation between the proximal LAD stenosis percentage and the values of CFR in the LAD by Vp and VBF. Moreover, in CAD patients with proximal LAD stenoses CFR by Vp was even much lower than in CAD patients with non-proximal stenoses in whom the vasodilatation reserve of the unaffected proximal segment remained adequate. In CAD patients with non-proximal LAD stenoses the CFR values in the LAD by both Vp and VBF practically did not differ from the controls owing to the adequate vasodilatation and increase of blood flow velocity characteristics in the unaffected segment. It is not consistent with the data of some authors reporting a decreased CFR in the LAD in both proximal and non-proximal stenoses.7 However, it may be explained by different criteria of hemodynamically significant stenoses of the LAD in selection of study patients (>50%—in the present study and <70%—in the works of other researchers).7

Thus, CFR decrease <2 in the LAD both by Vp and VBF is an evidence of hemodynamically significant stenosis of the LAD proximal segment.

In our study an increase of VBF in the CS during the stress test in healthy volunteers was caused, to a greater extent, by vasodilatation and, to a lesser extent, by acceleration of blood flow while an increase of VBF in the LAD was caused mainly by an increase of linear velocity (during the stress test: {Delta}% of CS diameter 17 ± 13% vs {Delta}% of LAD diameter 9 ± 10%, P = 0.058; {Delta}% of Vp in the LAD 254 ± 82% vs {Delta}% of Vp in the CS 156 ± 87%, P<0.01). It is clear from similar CFR values by Vp and VBF in the LAD and much greater CFR by VBF than CFR by Vp in the CS in the group of healthy individuals. This fact also caused a decreased CFR in the CS by Vp in seven healthy volunteers but CFR in the CS by VBF in only one healthy volunteer.

Coronary blood flow analysis in the CS after dipyridamole infusion showed that both proximal and non-proximal hemodynamically significant LAD stenoses limit an increase of coronary blood flow velocity distally beyond the impairment; this fact accounts for a significantly lower CFR in the CS by Vp in CAD patients of both groups in comparison with healthy volunteers. However, one-vessel impairment of the coronary system was not associated with a significant decrease of CFR in the CS by VBF in comparison with healthy individuals, apparently due to an adequate or compensating increase of blood inflow from the intact circumflex artery pool. So, CFR decrease <2 by Vp is an evidence of hemodynamically significant LAD stenoses irrespective of the impairment level, while in one-vessel impairment CFR level in the CS by VBF is not diagnostically informative.

Thus, simultaneous Doppler assessment of CFR in the LAD and CS via transesophageal approach is a highly informative procedure that can not only reveal hemodynamically significant LAD stenoses but differentiate between proximal and non-proximal impairments of this artery. Determination of CFR level in the dynamics can be a sensitive and specific marker of the effectiveness of different surgical interventions on the LAD.

4.1 Study limitation
A considerably greater age of CAD patients compared to that of healthy volunteers should be considered a study limitation that might result in lower values of CFR in CAD patients. However, absence of significant differences of CFR in the LAD in the group of healthy volunteers and CAD patients with non-proximal stenoses emphasizes a low value of this factor.


   5. Conclusions
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusions
References
 

1. Simultaneous Doppler assessment of CFR in the proximal third of the LAD and CS via the transesophageal approach makes it possible to diagnose hemodynamically significant stenoses of the LAD differentiating between the proximal and non-proximal impairments of this artery.
2. A decrease of CFR <2 in the proximal third of the LAD both at peak and volume velocities of coronary blood flow is a predictor of hemodynamically significant stenoses of the LAD in this segment and is accompanied by a decrease of CFR at the peak blood flow velocity in the CS.
3. A decrease of CFR <2 in the CS at the peak blood flow velocity with the adequate flow reserve in the proximal third of the LAD is a marker of hemodynamically significant stenoses of non-proximal segments of the LAD.


   References
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusions
 References
 

  1. Bimbaum Y., Luo H., Siegel R.J. Evaluation of the coronary arteries by intravascular ultrasound and Doppler flow wires. ACC Curr J Rev (1998) 7(2):31–37.
  2. Kern M.J. Focus for the new millennium: diffuse coronary artery disease and physiologic measurements of severity. ACC Curr J Rev (2000) 9(2):13–19.
  3. Klocke F.J, Greenberg J. Measurements of coronary flow reserve in clinically problematic coronary stenoses. ACC Curr J Rev (1998) 7(2):37–41.[CrossRef]
  4. Baumgart D., Haude M., Liu F., Ge J., Goerge G., Erbel R. Current concepts of coronary flow reserve for clinical decision making during cardiac catheterization. Am Heart J (1998) 136(1):136–149.[CrossRef][Web of Science][Medline]
  5. Hoffman J.I.E. Problems of coronary flow reserve. Ann Biomed Eng (2000) 28:884–896.[CrossRef][Web of Science][Medline]
  6. Zehetgruber M., Porenta G., Mundigler G., et al. Transesophageal versus intracoronary Doppler measurement for calculation of coronary flow reserve. Cardiovasc Res (1997) 36:21–27.[Abstract/Free Full Text]
  7. Hutchison S.J, Soldo S.J., Gadallah S., Kawanishi D.T, Chandraratna P.A.N. Determination of coronary flow measurements by transesophageal echocardiography: dependence of flow velocity reserve on the location of stenosis. Am Heart J (1997) 133:44–52.[CrossRef][Web of Science][Medline]
  8. Mundigler G., Zehetgruber M., Christ G., Siostrzonek P. Comparison of transesophageal coronary sinus and left anterior descending coronary artery measurements for the assessment of coronary flow reserve. Clin Cardiol (1997) 20:225–231.[Web of Science][Medline]
  9. Gadallah S., Thaker K.B., Kawanishi D., et al. Comparison of intracoronary Doppler guide wire and transesophageal echocardiography in measurement of flow velocity and coronary flow reserve in the left anterior descending coronary artery. Am Heart J (1998) 135:38–42.[CrossRef][Web of Science][Medline]
  10. Youn H.-J., Foster E. Transesophageal echocardiography (TEE) in the evaluation of the coronary arteries. Cardiol Clin (2000) 18(4):833–848.[CrossRef][Medline]
  11. Vrublevsky A.V., Boshchenko A.A., Karpov R.S. Noninvasive Doppler ultrasound of coronary arteries: methodical and diagnostic aspects. J Clin Imaging (2001) 19:50–60.
  12. Vrublevsky A.V., Boshchenko A.A., Karpov R.S. Diagnostics of main coronary artery stenoses and occlusions: multiplane transoesophageal Doppler echocardiographic assessment. Eur J Echocardiogr (2001) 2(3):170–177. 10.1053/euje.2001.0092.[Abstract/Free Full Text]
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  15. Karpov R.S, Doodko V.A. Atherosclerosis: pathogenesis, clinical course, functional diagnostics, treatment. (1998) Tomsk: SST. 656 pp.
  16. Fatenkov V.N. Cardiac biomechanics in experimental studies and clinical evaluation. (1990) Moscow: Medicina. 160 pp.

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