Noninvasive detection of total occlusion of the left anterior descending coronary artery with transthoracic Doppler echocardiography

Assessment of coronary microcirculation alterations in a porcine model of no-reflow using ultrasound localization microscopy: a proof of concept study

BACKGROUND

Coronary microvascular obstruction also known as no-reflow phenomenon is a major issue during myocardial infarction that bears important prognostic implications. Alterations of the microvascular network remains however challenging to assess as there is no imaging modality in the clinics that can image directly the coronary microvascular vessels. Ultrasound Localization Microscopy (ULM) imaging was recently introduced to map microvascular flows at high spatial resolution (∼10 μm). In this study, we developed an approach to image alterations of the microvascular coronary flow in ex vivo perfused swine hearts.

METHODS

A porcine model of myocardial ischemia-reperfusion was used to obtain microvascular coronary alterations and no-reflow. Four female hearts with myocardial infarction in addition to 6 controls were explanted and placed immediately in a dedicated preservation and perfusion box manufactured for ultrasound imaging. Microbubbles (MB) were injected into the vasculature to perform Ultrasound Localization Microscopy (ULM) imaging and a linear ultrasound probe mounted on a motorized device was used to scan the heart on multiple slices. The coronary microvascular anatomy and flow velocity was reconstructed using dedicated ULM algorithms and analyzed quantitatively.

FINDINGS

We were able to image the coronary microcirculation of ex vivo swine hearts at a resolution of tens of microns and measure flow velocities ranging from 10 mm/s in arterioles up to more than 200 mm/s in epicardial arteries. Under different aortic perfusion pressures, we measured in large arteries of a subset of control hearts an increase of flow velocity from 31 ± 11 mm/s at 87 mmHg to 47 ± 17 mm/s at 132 mmHg (N = 3 hearts, P < 0.05). This increase was compared with a control measurement with a flowmeter in the aorta. We also compared 6 control hearts to 4 hearts in which no-reflow was induced by the occlusion and reperfusion of a coronary artery. Using average MB velocity and average density of MB per unit of surface as two ULM quantitative markers of perfusion, we were able to detect areas of coronary no-reflow in good agreement with a control anatomical pathology analysis of the cardiac tissue. In the no-reflow zone, we measured an average perfusion of 204 ± 305 MB/mm2 compared to 3182 ± 1302 MB/mm2 in the surrounding re-perfused area.

INTERPRETATION

We demonstrated this approach can directly image and quantify coronary microvascular obstruction and no-reflow on large mammal perfused hearts. This is a first step for noninvasive, quantitative and affordable assessment of the coronary microcirculation function and particularly coronary microvascular anatomy in the infarcted heart. This approach has the potential to be extended to other clinical situations characterized by microvascular dysfunction.

FUNDING

This study was supported by the French National Research Agency (ANR) under ANR-21-CE19-0002 grant agreement.

Quantitative imaging of coronary flows using 3D ultrafast Doppler coronary angiography

Coronary flow rate remains complex to assess in clinical practice using non-invasive, non-ionizing imaging tools. In this study, we introduce 3D ultrafast Doppler coronary angiography (3D UDCA), an ultrasound-based method to assess coronary blood flows in three-dimensions at high volume-rate and in one single heartbeat. We demonstrate that 3D UDCA can visualize the coronary vasculature with high temporal and spatial resolution and quantify the absolute flow. The feasibility of the technique was demonstrated in an open-chest swine model. The flow rate of the left-anterior descending artery (LAD) assessed by 3D UDCA was reconstructed successfully at the early diastolic and late diastolic phases and was in good agreement with an invasive gold-standard flowmeter during baseline, reactive hyperemia and coronary stenosis (r² = 0.84). Finally, we demonstrate that a coronary stenosis on the LAD can be visualized as well as its associated flow acceleration.

Coronary artery occlusions diagnosed by transthoracic Doppler

Background

Our aim was to assess whether anterograde flow velocities in septal perforating branches could identify an occluded contralateral coronary artery, and to assess the feasibility and accuracy of diagnosing occlusions in the three main coronary arteries by the combined use of several noninvasive parameters indicating collateral flow.

Methods

A total of 108 patients scheduled for coronary angiography because of chest pain or acute coronary syndromes were studied using transthoracic Doppler echocardiography.

Results

Anterograde peak diastolic flow velocities (pDV) in septal perforating branches were higher in patients with angiographic occluded contralateral artery compared with corresponding velocities in patients without significant disease in the contralateral artery (0.80 ± 0.31 m/sec versus 0.37 ± 0.13 m/sec, p < 0.001). Receiver operating characteristic curve showed pDV ≥ 0.57 m/sec to be the optimal cutoff value to identify occluded contralateral artery, with a sensitivity of 79% and a specificity of 69%. Demonstration of at least one positive parameter (retrograde flow in main coronary arteries, reversed flow in septal perforating and left circumflex marginal branches, pDV ≥ 0.57 m/sec, or demonstration of other epicardial or intramyocardial collaterals) indicating collateral flow to an occluded main coronary artery had sensitivity, specificity, positive and negative predictive value of 89%, 94%, 63%, and 99%, respectively, for detection of a coronary occlusion. With this combined use of several parameters, 25 of 28 coronary occlusions were identified.

Conclusions

By investigating several parameters indicating collateral flow, we were able to identify most of the main coronary occlusions in the patient cohort. Furthermore, our study demonstrated that coronary artery occlusions may result in complex and diverging coronary pathophysiology depending on which coronary artery segment is occluded and the extent of accompanying coronary artery disease.

Trial registration

ClinicalTrials.gov number NTC00281346.

Acceleration time of systolic coronary flow velocity to diagnose coronary stenosis in patients with microvascular dysfunction

BACKGROUND

The aim of this study was to test whether acceleration time of systolic coronary flow velocity could contribute to the diagnosis of coronary stenosis in patients with microvascular dysfunction, on the basis of the hypothesis that systolic coronary flow is less influenced by microvascular function because of compressed myocardium.

METHODS

Coronary flow velocity was assessed in the left anterior descending coronary artery during hyperemia with intravenous adenosine by echocardiography in 502 patients who were scheduled for coronary angiography because of coronary artery disease and significant valvular disease. Coronary flow velocity reserve (CFVR) and the percentage acceleration time (%AT), as the percentage of the time from the beginning to the peak of systolic coronary flow over systolic time during hyperemia, were calculated. The diagnostic ability of CFVR and %AT for angiographic coronary artery stenosis was then analyzed. As invasive substudies, fractional flow reserve and %AT by a dual-sensor (pressure and Doppler velocity) guidewire were measured simultaneously with %AT on transthoracic echocardiography (n = 14).

RESULTS

Patients with coronary stenosis had significantly lower CFVR (1.7 ± 0.4) and greater %AT (65 ± 9%) compared with those without stenosis (2.6 ± 0.6 and 50 ± 13%, respectively). Percentage acceleration time by Doppler echocardiography was in good agreement with %AT (r = 0.98) and fractional flow reserve (r = 0.74) invasively measured by dual-sensor guidewire. Cutoff values of CFVR and %AT were determined as 2.0 and 60% in receiver operating characteristic curve analysis. The sensitivity, specificity, and accuracy of CFVR to detect coronary stenosis were 71.1%, 77.3%, and 75.4%, while those of %AT were 83.4%, 71.8%, and 75.4%, respectively. In addition, %AT provided high accuracy to detect coronary stenosis, especially in patients with previous myocardial infarctions, valvular disease, and left ventricular hypertrophy (81.1%, 84.1%, and 73.4%, respectively).

CONCLUSIONS

The %AT of systolic coronary flow velocity is a promising marker to diagnose coronary stenosis in patients with microvascular dysfunction.

Patient with pseudo-retrograde coronary flow in the normal right coronary artery and left circumflex artery: pitfall of retrograde coronary flow to detect coronary artery occlusion

A 75-year-old lady with hypertension and paroxysmal atrial fibrillation underwent echocardiography to evaluate cardiac function. Transthoracic Doppler echocardiography revealed retrograde coronary flow in the right coronary artery (RCA) and left circumflex artery (LCX). Computed tomographic coronary angiography demonstrated normal but tortuous coronary arteries. This tortuosity of the coronary arteries was thought be a cause of pseudo-retrograde coronary flow in the RCA and LCX. The present case demonstrates a pitfall of retrograde coronary flow for the detection of coronary artery occlusion in daily practice.

A patient came back with retrograde coronary flow in the distal right coronary artery 2 years after coronary intervention: clinical significance of retrograde coronary flow to detect coronary artery occlusion

A 69-year-old male patient, who had a history of coronary stent implantation to the proximal right coronary artery (RCA), presented with exertional chest pain. Transthoracic Doppler echocardiography revealed retrograde coronary flow in the distal RCA, and treadmill stress echocardiography revealed inducible myocardial ischemia in the inferior and posterior segments. Coronary angiography demonstrated a severe stenotic lesion with flow delay in the mid RCA and collateral circulation to the distal RCA from the left coronary artery. Detection of retrograde coronary flow in the distal RCA using transthoracic Doppler echocardiography is a useful method to diagnose subtotal occlusion of the RCA.

Resting coronary flow velocity in the functional evaluation of coronary artery stenosis: study on sequential use of computed tomography angiography and transthoracic Doppler echocardiography

AIMS

Accelerated flow at the site of flow-limiting stenosis can be detected by transthoracic Doppler echocardiography (TTDE). We studied feasibility and accuracy of sequential coronary computed tomography angiography (CTA) and TTDE in detection of haemodynamically significant coronary artery disease (CAD).

METHODS AND RESULTS

We prospectively enrolled 107 patients with intermediate (30-70%) pre-test likelihood of CAD. All patients underwent CTA using a 64-slice scanner. Using TTDE, the ratio of maximal diastolic flow velocity to pre-stenotic flow velocity (M/P ratio) was measured in the coronary segments with stenosis in CTA. In all patients, the results were compared with invasive coronary angiography, including measurement of fractional flow reserve when appropriate. All analyses were done blinded. TTDE was feasible in 276 of 285 evaluated coronary segments. Significant coronary stenoses were associated with a higher M/P ratio than non-significant stenoses (3.59 ± 1.82 vs. 1.28 ± 0.60, P < 0.001). The optimal M/P ratio for detection of significant stenosis was 2.2 (area under receiver operating characteristic curve 0.92, P < 0.001). Compared with the strategy of CTA alone, sequential CTA and focused TTDE had a better positive predictive value (PPV; 61 vs. 78%) and diagnostic accuracy (93 vs. 96%, P = 0.006) without impairment of the negative predictive value (97 vs. 97%).

CONCLUSION

Sequential use of CTA and TTDE is feasible for combined anatomic and functional evaluation of coronary stenoses. Compared with coronary CTA alone, addition of TTDE improved PPV for detection of significant CAD.

Detection of severe left anterior descending coronary artery stenosis by transthoracic evaluation of resting coronary flow velocity dynamics

In the presence of severe stenosis, coronary artery flow may be reduced at rest. Recent advances in echocardiography have made non-invasive sampling of velocities in the left anterior descending coronary artery (LAD) possible. The aim of our study was to evaluate feasibility and capability of transthoracic Doppler to detect severe stenosis of the LAD. The study population consisted of 42 subjects with suspected coronary artery disease scheduled for coronary angiography. All had complete transthoracic echocardiography and Doppler sampling of LAD velocities. Quantitative coronary angiography was performed within 24 hours of the echocardiogram. Correlations between LAD velocity profile, measurements and calculations, and the angiographic results were performed. Six subjects had LAD occlusion, 10 had severe (>80% diameter) LAD stenosis, and 26 had normal or non-occlusive LAD disease. In all six subjects with LAD occlusion, distal LAD velocities were not detectable, while in the other 36 subjects, LAD velocities were recorded indicating the vessels were patent. In the 10 subjects with severe LAD stenosis, the diastolic/systolic velocity ratio was <1.5, while in those with non-significant LAD disease, the diastolic/systolic velocity ratio was >1.5 (P<0.005). Diastolic LAD flow was 21.8±13 mL/min in the presence of severe stenosis as compared to 48.5±20 mL/min in subjects without severe stenosis (P<0.0013). LAD velocities had high sensitivity and specificity for the prediction of severe angiographic stenosis. Thus transthoracic Doppler measurement of LAD velocities is feasible and can predict the presence of severe LAD stenosis or occlusion.

Transthoracic echocardiography for imaging of the different coronary artery segments: a feasibility study

Background

Transthoracic echocardiography (TTE) may be used for direct inspection of various parts of the main coronary arteries for detection of coronary stenoses and occlusions. We aimed to assess the feasibility of TTE to visualise the complete segments of the left main (LM), left descending (LAD), circumflex (Cx) and right (RCA) coronary arteries.

Methods

One hundred and eleven patients scheduled for diagnostic coronary angiography because of chest pain or acute coronary syndrome had a TTE study to map the passage of the main coronary arteries. LAD, Cx and RCA were each divided into proximal, middle and distal segments. If any part of the individual segment of a coronary artery with antegrade blood flow was not visualised, the segment was labeled as not satisfactorily seen.

Results

Complete imaging of the LM was achieved in 98% of the patients. With antegrade directed coronary artery flow, the proximal, middle and distal segments of LAD were completely seen in 96%, 95% and 91% of patients, respectively. Adding the completely seen segments with antegrade coronary flow and segments with retrograde coronary flow, the proximal, middle and distal segments of LAD were adequately visualised in 96%, 96% and 93% of patients, respectively. With antegrade directed coronary artery flow, the proximal, middle and distal segments of Cx were completely seen in 88%, 61% and 3% and in RCA in 40%, 28% and 54% of patients. Retrograde coronary artery flow was correctly identified as verified by coronary angiography in seven coronary segments, mainly in the posterior descending artery (labeled as the distal segment of RCA) and distal LAD.

Conclusions

TTE is a feasible method for complete demonstration of coronary flow in the LM, the proximal Cx and the different segments of LAD, but less suitable for the RCA and mid and distal segments of the Cx. (ClinicalTrials.gov number NTC00281346.)

Detection of severe stenosis and total occlusion in the left anterior descending coronary artery with transthoracic Doppler echocardiography in the emergency room

BACKGROUND

The noninvasive measurement of coronary flow velocity in the left anterior descending artery (LAD) has recently been realized by using the transthoracic Doppler echocardiography (TTDE). A couple of investigations demonstrated that the diastolic-to-systolic peak velocity ratio (DSVR) by TTDE is a simple and noninvasive method for the detection of severe stenosis in the elective settings. However, the usefulness of DSVR by TTDE in the emergency settings has not been evaluated.

OBJECTIVE

The purpose of this study was to assess the clinical feasibility to document the LAD flow by TTDE in emergency patients who complained of chest pain.

METHODS

We studied 49 consecutive patients with acute coronary syndrome who were going to undergo emergency coronary angiography (CAG) for the anatomical diagnosis and the facilitated percutaneous coronary intervention (PCI). Prior to CAG, we recorded the LAD flow by TTDE and measured the diastolic peak velocity (DVp), systolic peak velocity (SVp), and their ratio, DSVR (DVp/SVp) of LAD flow.

RESULTS

By CAG, the culprit lesions actually resided in the proximal LAD in 36 patients. Among the 36 patients, we detected the Doppler LAD flow in 29. Five out of 7 patients who were unable to detect the LAD flow revealed total occlusions by CAG. DSVR of the LAD is significantly lower in 17 patients who showed severe stenoses (>90%) than those in the rest of 12 patients who did not show such critical stenoses (1.44 +/- 0.16 vs 2.10 +/- 0.26, P < 0.0001).

CONCLUSION

In the emergency settings, a noninvasive assessment of the LAD flow by TTDE accurately estimates the critical stenotic lesions of the LAD.

Coronary microcirculation in the beating heart

The phase opposition of velocity waveforms between coronary arteries (predominantly diastolic) and veins (systolic) is the most prominent characteristic of coronary hemodynamics. This unique arterial and venous flow patterns indicate the importance of intramyocardial capacitance vessels and variable resistance vessels during a cardiac cycle. It was shown that during diastole the intramyocardial capacitance vessels have two functional components, unstressed volume and ordinary capacitance. Unstressed volume is defined as the volume of blood in a vessel at zero transmural pressure. In vivo observation of systolic narrowing of arterioles in mid-wall and in subendocardium indicates the increase in resistance by cardiac contraction.

Transthoracic echocardiography in the detection of chronic total coronary artery occlusion

AIMS

The aim of our study was to detect chronic total occlusion of the left anterior descending coronary artery (LAD), circumflex coronary artery (Cx), and right coronary artery (RCA) using transthoracic echocardiography (TTE) in 110 consecutive patients who underwent coronary angiography for investigation of angina.

METHODS AND RESULTS

Coronary blood flow direction was assessed in the epicardial collaterals [distal LAD (dLAD), obtuse marginal branches and right posterior descending artery (PDA)] and intramyocardial collaterals [LAD septal branch (SB LAD) and RCA septal branch (SB RCA)]. The sensitivity and specificity of retrograde flow for identification of the occluded LAD by TTE in the dLAD only were 78 and 96%, respectively, and those in both dLAD and SB LAD were 89 and 96%, respectively. The retrograde SB LAD flow detects proximal LAD occlusion with 88% sensitivity and 75% specificity. The sensitivity and specificity of retrograde flow for identification of the occluded RCA by TTE in the PDA only were 79 and 97%, respectively, and those in both PDA and SB RCA were 89 and 97%, respectively. The retrograde SB RCA flow does not allow us to differentiate between proximal and non-proximal RCA occlusion. Transthoracic echocardiography is not a method for diagnosing Cx occlusions as the success in visualizing the Cx epicardial collaterals was achieved in 31% of cases only.

CONCLUSION

TTE is a sensitive and highly specific non-invasive method for diagnosis of LAD and RCA occlusions, based on the detection of the coronary blood flow direction in the epicardial and intramyocardial collaterals.

Non-invasive assessment of coronary flow and coronary flow reserve by transthoracic Doppler echocardiography: a magic tool for the real world

Transthoracic Doppler echocardiography, introduced in the echo-lab in recent last years, to measure coronary flow and coronary flow reserve, is a very attractive tool, totally non-invasive, and easily available at bedside. This review summarizes the actual possibilities of this tool, its multiple potential clinical applications and diagnostic insights, and its arising prognosis value, in coronary artery disease as in various settings affecting the coronary microcirculation.

Decreased coronary flow reserve in haemodialysis patients

BACKGROUND

Coronary flow reserve (CFR) reflects the functional capacity of microcirculation to adapt to blood demand during increased cardiac work.

METHODS

Forty-one patients who had already undergone coronary angiography were studied. They consisted of 21 haemodialysis patients with no significant left anterior descending coronary artery (LAD) stenosis and 20 non-renal failure patients without LAD stenosis. We performed transthoracic Doppler recording of diastolic coronary flow velocity in the LAD at baseline and after maximal vasodilatation by adenosine triphosphate (ATP) infusion. CFR was defined as the ratio of hyperaemic to basal averaged peak flow velocity.

RESULTS

Although the peak coronary velocities during hyperaemia were similar between the two groups, CFR was smaller in haemodialysis (HD) patients than in control subjects (1.96 +/- 04 versus 2.3 +/- 0.5, P = 0.001) due to the higher baseline peak coronary velocities in the former.

CONCLUSIONS

The elevated baseline peak coronary velocity may be caused by cardiac hypertrophy and anaemia in HD patients.

Functional assessment of the collateral-dependent circulation in chronic total coronary occlusion using transthoracic Doppler ultrasound and venous adenosine infusion

The measurement of collateral flow reserve (CFR; the hyperemic/baseline collateral flow velocity ratio) in patients with chronic total coronary occlusion requires invasive and expensive techniques. Noninvasive transthoracic coronary Doppler echocardiography may be an alternative option. Fifty-one patients with chronic total coronary occlusion were evaluated by transthoracic coronary Doppler echocardiography and venous adenosine infusion to measure CFR in occluded coronary arteries (the left anterior descending artery in 44 patients and the artery supplying the posterior descending artery in 7 patients). CFR data were plotted against 3 angiographic parameters: (1) grade of the epicardial filling of the occluded artery (1=absent, 2=partial, 3=complete), (2) stenosis of the donor artery, and (3) the extent of coronary artery disease (vessels with >or=70% stenosis). Collateral flow was maintained at stress in 34 patients (CFR>or=1, range 1.0 to 2.2) but was withdrawn in 17 patients (CFR<1, range 0.25 to 0.90). CFR increased with the degree of angiographic collateral flow (grade 1: 0.73+/-0.29; grade 2: 1.16+/-0.31; grade 3: 1.34+/-0.49; F=5.31, p=0.008). A multivariate model of CFR prediction showed a direct relation with angiographic collateral grade and the number of diseased vessels and an inverse relation with stenosis of the donor artery. In conclusion, CFR measurement is feasible by transthoracic coronary Doppler echocardiography. One third of the patients with chronic total coronary occlusion had collateral flow withdrawal at stress, which occurs when collateral circulation is poor and when the donor artery is stenotic. CFR correlates with angiographic collateral grade and with the extent of coronary artery disease.

A Novel Technique to Detect Total Occlusion in the Right Coronary Artery Using Retrograde Flow by Transthoracic Doppler Echocardiography

BACKGROUND

We hypothesized that detection of reverse flow in the distal right coronary artery (d-RCA) and the inferior septal branches (ISB) by transthoracic Doppler echocardiography (TTDE) would be useful for noninvasive diagnosis of the occluded right coronary artery (RCA).

METHODS

Coronary angiography and TTDE were performed on 129 patients. Antegrade flows in the d-RCA and the ISB were defined as directions from the base to the apex in the posterior sulcus and from anterior to inferior in the inferior septum, respectively. Retrograde flow was defined as an inverse direction.

RESULTS

Retrograde flow was obtained by TTDE in 14 patients (d-RCA:11, ISB:3) of 18 patients with occluded RCA. The sensitivity and the specificity for identification of occluded RCA were 100% and 97.8%, respectively.

CONCLUSION

Detection of reverse flow in the d-RCA and the ISB using TTDE is a useful method for the noninvasive diagnosis of occluded RCA.

Transthoracic Doppler Echocardiography as a Noninvasive Tool to Assess Coronary Artery Stenoses-A Comparison with Quantitative Coronary Angiography

We prospectively tested the diagnostic accuracy of Doppler transthoracic echocardiography in detection of coronary artery stenoses throughout the main coronary arterial tree. In all, 84 patients referred for diagnostic quantitative coronary angiography were studied. Coronary artery stenosis was identified with color Doppler as local spot of turbulence, and local flow velocity was measured using pulsed wave Doppler. Angiography showed significant stenoses (diameter reduction > 50%) in 33 patients. An abnormal maximal-to-prestenotic blood flow velocity ratio greater than 2.0 in subtotal stenoses, or the detection of collateral blood flow in the absence of normal antegrade flow in the case of total occlusion (N = 6), resulted in overall sensitivity of 82% and specificity of 92%. The sensitivity and specificity were, respectively, 73% and 92% for left anterior descending coronary artery, 63% and 96% for right coronary artery, and 38% and 99% for left circumflex coronary artery stenoses. Transthoracic echocardiography is a promising noninvasive technique to diagnose significant coronary artery stenoses.

Correlation Between Distal Left Anterior Descending Artery Flow Velocity by Transthoracic Doppler Echocardiography and Corrected TIMI Frame Count Before Mechanical Reperfusion in Patients With Anterior Acute Myocardial Infarction

BACKGROUND

This study was designed to determine the utility of transthoracic Doppler echocardiography (TTDE) in evaluating angiographic Thrombolysis in Myocardial Infarction (TIMI) frame count as a quantitative index of coronary reperfusion in patients with anterior acute myocardial infarction (AMI) before mechanical reperfusion.

METHODS AND RESULTS

Color and pulsed TTDE was performed to evaluate distal left anterior descending coronary artery (LAD) reperfusion in 56 consecutive patients with a first anterior AMI before coronary intervention, and these findings were compared with the corrected TIMI frame count (cTFC) by subsequent angiography. Twenty-four of the 56 patients had LAD reperfusion (TIMI 2 or 3) by angiography. Visual antegrade distal LAD flow by color TTDE was detected in 21 of these 24 patients. In the 21 patients, diastolic peak velocity of the distal LAD flow by pulsed TTDE showed a significant correlation with cTFC by angiography (r = -0.74, p < 0.001). The diagnosis of high risk with angiographic cTFC >40 by distal LAD peak velocity <21 cm/s using TTDE had a sensitivity, specificity, and accuracy of 82%, 93%, and 91%, respectively.

CONCLUSION

TTDE enables noninvasive and quantitative evaluation of distal LAD reperfusion in patients with anterior AMI in the acute phase before mechanical reperfusion.

[Measurement of coronary flow and flow reserve with transthoracic echocardiography: an old concept, a new tool, a lot of applications]

Non invasive evaluation of coronary flow and flow reserve by using transthoracic echocardiography is a promising method for evaluating coronary disease. Left anterior descending and right posterior descending coronary flow are accessible in the majority of patients. This technique is useful in various settings: detection of coronary artery stenosis, coronary occlusion, follow up after percutaneous coronary intervention, evaluation of the significance of coronary stenosis of intermediate severity, evaluation of the microcirculation, study of reperfusion and no reflow in the acute phase of myocardial infarction, evaluation of bypass grafts, improvement of the diagnostic accuracy during stress echocardiography. After a period of training, it's possible to change an old concept, formerly not easily accessible in clinical practice, into a useful and modern tool for evaluating coronary artery disease.

Demonstration of coronary artery flow using transthoracic Doppler echocardiography

Transthoracic Doppler echocardiography is emerging as a promising method for evaluating coronary artery disease. After a period of training, detection and measurement of distal left anterior descending coronary artery flow with transthoracic Doppler echocardiography is feasible in more than 90% of the patients. Using transthoracic Doppler echocardiography with a high-frequency transducer and special setting of low Nyquist limits, pathologic coronary flow dynamics can be demonstrated. Measurement of coronary flow reserve may impact diagnosis or clinical treatment in those: (1) with anginal chest pain and angiographically normal coronary arteries; (2) with intermediate-grade coronary obstruction where the physiologic significance is in doubt; and (3) who have had an attempt at revascularization and the effectiveness of the therapy is uncertain.

Simple detection of occluded coronary artery using retrograde flow in septal branch and left anterior descending coronary artery by transthoracic doppler echocardiography at rest

BACKGROUND

We hypothesized that coronary flow assessment by transthoracic Doppler echocardiography (TTDE) for both intramyocardial collateral channel and epicardial channels would be useful for identifying occluded left anterior descending coronary artery (LAD).

METHODS

We assessed flow direction in the LAD and the septal branch (SEP) by TTDE in 302 consecutive patients who were suggested to have ischemic heart disease. We defined antegrade LAD flow as a direction from the base to the apex of the left ventricle in the anterior groove area, and antegrade SEP flow as a direction from anterior to inferior in the anterior interventricular septum. By contrast, we defined retrograde LAD and SEP flow as an inverse direction. We performed angiography on all patients.

RESULTS

Retrograde flow was detected in 22 (LAD, 16 patients; SEP, 6 patients) of 23 patients with occluded LAD, and antegrade flow was detected in all patients without occluded LAD. The sensitivity and specificity for identification of occluded LAD by TTDE were 96% and 100%, respectively.

CONCLUSIONS

Assessment of flow direction in both LAD and SEP by TTDE is a useful method in identification of occluded LAD.

Changes in left anterior descending coronary artery flow profiles after coronary artery bypass grafting examined by means of transthoracic Doppler echocardiography

OBJECTIVE

We sought to investigate the changes of velocity profiles in the left anterior descending coronary artery after coronary artery bypass grafting using transthoracic Doppler echocardiography.

METHODS

Forty-five patients who received a bypass graft to the left anterior descending coronary artery were studied. Before coronary artery bypass grafting, Doppler velocity profiles of the distal left anterior descending coronary artery were recorded with transthoracic Doppler echocardiography. Peak systolic velocity, mean systolic velocity, peak diastolic velocity, mean diastolic velocity, total velocity time integral, systolic velocity time integral, and diastolic velocity time integral were measured. Three weeks after coronary artery bypass grafting, left anterior descending coronary artery antegrade flow in the distal portion of the anastomosis was obtained by using the same method. Coronary angiography was performed before and 3 weeks after coronary artery bypass grafting.

RESULTS

The overall success rate of measuring the left anterior descending coronary artery flow was 60.0% preoperatively and 80.0% postoperatively. In 25 patients, in whom all parameters were obtained both before and after coronary artery bypass grafting, the following increased significantly after coronary artery bypass grafting: peak systolic velocity (14.86 +/- 7.50 vs 25.07 +/- 17.02 cm/s, P =.0045), mean systolic velocity (9.86 +/- 5.42 vs 18.03 +/- 12.94 cm/s, P =.0026), peak diastolic velocity (24.26 +/- 12.54 vs 48.28 +/- 31.66 cm/s, P =.0021), mean diastolic velocity (14.94 +/- 6.65 vs 30.36 +/- 20.71 cm/s, P =.0022), diastolic velocity time integral (7.22 +/- 2.88 vs 15.55 +/- 10.39 cm, P =.0009), total velocity time integral (10.50 +/- 4.48 vs 19.27 +/- 12.63 cm, P =.0034), and diastolic-to-systolic velocity time integral ratio (3.09 +/- 1.53 vs 4.97 +/- 2.75, P =.0044). Angiography showed graft patency and no significant change in left anterior descending coronary artery stenosis in all patients.

CONCLUSIONS

Transthoracic Doppler echocardiography showed a significant increase in some parameters in left anterior descending coronary artery flow after coronary artery bypass grafting. Measurement of left anterior descending coronary artery flow by means of transthoracic Doppler echocardiography might be a noninvasive method to evaluate the effect of bypass grafting on the left anterior descending coronary artery.

Noninvasive evaluation of coronary reperfusion by transthoracic Doppler echocardiography in patients with anterior acute myocardial infarction before coronary intervention

BACKGROUND

Transthoracic Doppler echocardiography (TTDE) enables evaluation of distal left anterior descending coronary artery (LAD) flow. The purpose of this study was to test whether TTDE can differentiate coronary reperfusion with Thrombolysis in Myocardial Infarction (TIMI) grade 3 from TIMI grade < or =2 in patients with anterior acute myocardial infarction (AMI).

METHODS AND RESULTS

In 46 consecutive patients with a first anterior AMI in the acute phase before emergent coronary intervention, the presence of antegrade distal LAD flow and its diastolic peak velocity were evaluated by color and pulsed TTDE and compared with TIMI grades by subsequent coronary angiography performed 29+/-12 minutes later. Nineteen patients had TIMI 0 reperfusion, 4 had TIMI 1, 10 had TIMI 2, and 13 had TIMI 3. Visual antegrade distal LAD flow was present in 22 of the 46 patients. TIMI 2 and 3 reperfusions were both generally visualized by color TTDE. However, peak distal LAD flow velocity by pulsed TTDE was significantly greater in patients with TIMI 3 compared with those with TIMI 2 (40+/-10 vs 20+/-6 cm/s, P<0.0001). The diagnosis of TIMI 3 based on diastolic peak distal LAD flow velocity > or =25 cm/s by TTDE had a sensitivity, specificity, and accuracy of 77%, 94%, and 89%, respectively.

CONCLUSIONS

TTDE enables noninvasive differentiation of TIMI 3 from TIMI < or =2 coronary reperfusion in patients with AMI in the acute phase before emergent coronary intervention.

Comparison of transthoracic Doppler echocardiography to intracoronary Doppler guidewire measurements for assessment of coronary flow reserve in the left anterior descending artery for detection of restenosis after coronary angioplasty

Transthoracic Doppler echocardiography (TDE) has been described as a feasible and accurate technique to noninvasively assess coronary flow reserve (CFR) in the left anterior descending artery (LAD). This study was designed to evaluate whether serial assessment of CFR in the LAD using TDE allows detection of restenosis after previously performed angioplasty. Thirty-three consecutive patients with single-vessel coronary artery disease of the LAD scheduled for angioplasty underwent assessment of coronary flow velocity at rest and during adenosine-induced hyperemia in the distal LAD using high-frequency TDE. CFR was calculated as the ratio of hyperemic to basal systolic/diastolic mean velocity. Investigations were performed before and immediately after angioplasty, and at the time of control angiography after 3 months. CFR results by TDE were compared with intracoronary Doppler guide wire measurements. Adequate pulse-wave Doppler signals to measure CFR were obtained in 30 patients (91%) using TDE. There was close correlation between echocardiographically and intracoronary derived CFR results (r = 0.80, 0.79, and 0.87 before angioplasty, early after, and at 3- month control angiography, respectively; p <0.001). Using a cut-off value of CFR < or =2.0 to identify significant coronary artery disease, TDE detected LAD restenosis with a sensitivity of 89% and specificity of 90%. Thus, high-frequency TDE is a feasible technique to noninvasively assess CFR in the LAD with results closely corresponding to invasive measurements. Defining a cut-off value of CFR < or =2.0, the technique has the potential to reliably detect LAD stenosis after coronary intervention.