Assessment of coronary blood flow by transesophageal two-dimensional pulsed Doppler echocardiography

Assessment of the Severity of Left Anterior Descending Coronary Artery Stenoses by Enhanced Transthoracic Doppler Echocardiography: Validation of a Method Based on the Continuity Equation

BACKGROUND

To verify whether the severity of coronary stenosis could be non-invasively assessed by enhanced transthoracic coronary echo Doppler in convergent color Doppler mode (E-Doppler TTE) over a wide range of values (from mild to severe).

METHODS

Color-guided pulsed wave Doppler sampling in the left anterior descending coronary artery (LAD) was performed in 103 diseased LAD segments (corresponding to 94 patients examined) as assessed by quantitative coronary angiography (QCA) or intracoronary ultrasound (IVUS). The E-Doppler TTE examinations consisted of measuring the velocity (vel) at the stenosis site and a reference adjacent segment. Then the continuity equation (C-Eq) was applied to calculate the percent cross-sectional area reduction (%CSA) at the stenosis site. The applied formula was: %CSA = 100 × (1 - [TVIref × 0.5]/TVIs). TVI = the time velocity integral at the stenosis [s] and the reference site [ref], respectively); 0.5 = the correcting factor for a parabolic profile was used only when the % accelerated stenotic flow was >122% (AsF = diastolic peak vel at first site - diastolic peak vel at second site/diastolic peak vel at second site × 100).

RESULTS

E-Doppler TTE feasibility was 100%. Doppler and QCA/IVUS-derived %CSA stenosis showed very good agreement over a large range of values (from mild to severe), with no significant bias; the maximum difference between QCA/IVUS and transthoracic Doppler %CSA was mostly around 20% with a few patients exceeding this limit (limits of agreement = -27.53 to 23.5%). The scattering was slightly larger for the non-significant stenoses. The correlation was strong (r = 0.89, p < 0.001).

CONCLUSION

E-Doppler TTE is a feasible and reliable method for assessing the severity of LAD stenosis by applying the C-Eq.

Comparison of transesophageal coronary sinus and left anterior descending coronary artery Doppler measurements for the assessment of coronary flow reserve

BACKGROUND

Currently used methods for assessment of coronary flow reserve are invasive and require extensive laboratory equipment. Recently, noninvasive assessment of coronary flow reserve by transesophageal Doppler evaluation of coronary sinus (CS) or left anterior descending coronary artery (LAD) flow has been proposed. Direct comparison between these two techniques is lacking.

METHODS

Doppler recordings of CS and LAD flow velocity were obtained before and after 0.6 mg/kg/5 min dipyridamole in 16 patients with significant stenosis of the LAD (Group A) and in 14 control patients (Group B). Flow recordings and all measurements were performed in a blinded manner. For assessment of coronary flow reserve, Doppler measurements after dipyridamole were divided by the respective baseline values.

RESULTS

Doppler studies of the CS and LAD were feasible in 30 of 30 (100%) and 23 of 30 (71%) patients, respectively. Analyzing the maximum flow velocities, coronary flow reserve in Groups A and B was 1.18 +/- 0.28 and 1.68 +/- 0.53 with CS recordings and 1.78 +/- 0.83 and 2.51 +/- 0.76 with LAD recordings, respectively. Analyzing the velocity time integrals, coronary flow reserve in Groups A and B was 1.53 +/- 0.68 and 2.59 +/- 0.74 with CS recordings and 1.77 +/- 0.38 and 2.68 +/- 0.93 with LAD recordings, respectively. Correlation between LAD and CS recordings was 0.69 (p < 0.001), when coronary flow reserve was calculated from the velocity time integral and 0.68 (p < 0.001) when the maximum flow velocities were used.

CONCLUSION

Both transesophageal Doppler techniques might be useful for noninvasive assessment of coronary flow reserve.

Coronary flow velocity reserve in hypertensive patients with left ventricular systolic dysfunction

BACKGROUND

Hypertensive microvascular disease is speculated to be a limiting factor for the ability of left ventricular (LV) hypertrophy to maintain LV systolic function in systemic hypertension. The role of coronary reserve, which may be affected by microvascular disease, remains uncertain in the pathophysiology of hypertensive heart disease.

HYPOTHESIS

A progressive impairment of coronary flow velocity reserve (CFVR) according to the presence and severity of LV systolic dysfunction is anticipated to occur in hypertension.

METHODS

According to the absence or presence of LV dysfunction (LV fractional shortening - FS% < 30), two groups of hypertensive patients were investigated: HP1 (n = 9, FS% = 36+/-6) and HP2 (n = 13, FS% = 18+/-6). Eight normal subjects (NL) served as controls (LVFS% = 35+/-3). Doppler blood flow velocity was obtained from the left anterior descending coronary artery using transesophageal echocardiography before, and during 6-min continuous adenosine infusion (140 microg x kg(-1) x min(-1) intravenous). The CFVR was calculated as the ratio of maximal to baseline peak diastolic flow velocities.

RESULTS

The comparison among NL, HP1, and HP2 groups showed statistically different (p < 0.05) mass index (101+/-18, 172+/-46, and 257+/-54 g x m(-2)), end-systolic wall stress (76.9+/-14.4, 78.4+/-23.9, and 174.5+/-43.0 10(3) x dyn x cm(-2)), and CFVR (3.5+/-0.6, 3.2+/-0.4, and 2.6+/-0.8), respectively. The CFVR correlated significantly and directly with LVFS% (r = 0.40) and correlated inversely with both mass index (r = -0.54) and end-systolic stress (r = -0.40).

CONCLUSIONS

These results indicate that CFVR impairment is weakly related to LV dysfunction in hypertension.

Intra-aortic balloon counterpulsation

Intra-aortic balloon counterpulsation (IABP) is sometimes used in critically ill patients with cardiac disease. By increasing diastolic arterial pressure and decreasing systolic pressure, it reduces left ventricular afterload. IABP may be beneficial in subjects with cardiogenic shock, mechanical complications of myocardial infarction, intractable ventricular arrhythmias, or advanced heart failure or those who undergo "high-risk" surgical or percutaneous revascularization, but the evidence to support its use in these patient groups is largely observational. Contraindications to IABP include severe peripheral vascular disease as well as aortic regurgitation, dissection, or aneurysm. The potential benefits of IABP must be weighed against its possible complications (bleeding, systemic thromboembolism, limb ischemia, and, rarely, death).

Extra-aortic balloon counterpulsation: an intraoperative feasibility study

BACKGROUND

Current methods of counterpulsation or ventricular assistance have significant vascular and limb complications. The aim of this study was to determine the safety and performance of a new method of non-blood-contacting counterpulsation using an inflatable cuff around the ascending aorta (extra-aortic balloon [EAB]).

METHODS AND RESULTS

In 6 patients undergoing first time off-pump coronary bypass surgery via sternotomy, the EAB was secured around the ascending aorta and attached to a standard counterpulsation console. At baseline and with 1:2 and 1:1 augmentation, hemodynamic and echocardiographic parameters of ventricular function and coronary flow were measured. High-intensity transient signals were measured using transcutaneous Doppler over the right common carotid artery. No complications occurred. With EAB there was no significant change in heart rate or blood pressure and no increase in high-intensity transient signals. There was a 67% increase in diastolic coronary blood flow (mean left-main diastolic velocity time integral 15.3 cm unassisted versus 25.1 cm assisted, P<0.05). Measurements with transesophageal echocardiography at baseline and with 1:1 counterpulsation demonstrated a 6% reduction in end-diastolic area (P=NS), a 16% reduction in end-systolic area (P<0.01), a 31% reduction in left ventricular wall stress (P<0.05), and a 13% improvement in fractional area change (P<0.005).

CONCLUSIONS

EAB counterpulsation augments coronary flow and reduces left ventricular afterload. Further testing is warranted to assess the use of the EAB for chronic non-blood-contacting support of the failing heart.

New applications of intracardiac echocardiography: assessment of coronary blood flow by colour and pulsed Doppler imaging in dogs

OBJECTIVE

To explore the application of a new 10 French intracardiac echocardiography (ICE) catheter with phased array and Doppler capable transducer for the assessment of epicardial and intramyocardial coronary blood flow.

METHODS

The coronary arteries were detected by cross sectional imaging in seven closed chest dogs, and coronary blood flow visualised by colour Doppler. Blood flow velocities were recorded by pulsed Doppler at baseline for reproducibility of repeated measurements, and during hyperaemia for coronary flow reserve measurements. Comparisons were made with Doppler guide wire data obtained simultaneously. Intramyocardial coronary artery blood flow was assessed by colour flow mapping, and the blood flow velocities recorded using pulsed Doppler at baseline and during hyperaemia.

RESULTS

Seven left main, six left anterior descending, seven left circumflex, and five right coronary arteries were visualised in the seven animals by cross sectional or colour Doppler imaging. Repeated measurements of coronary flow velocity showed a good correlation (mean diastolic velocity, r = 0.93, n = 22, p < 0.0001; peak diastolic velocity, r = 0.96, n = 22, p < 0.0001, respectively). Intraobserver/interobserver variability was satisfactorily low. Coronary flow reserve from ICE correlated highly with the value obtained from the Doppler guide wire (r = 0.90, n = 26, p < 0.0001). Intramyocardial coronary blood flow was identified in all seven dogs, and flow velocities were recorded at baseline and during hyperaemia in four animals.

CONCLUSIONS

This new ICE catheter provides high quality diagnostic resolution. It is useful for coronary blood flow assessment.

Transesophageal echocardiography in patients with ischemic stroke accurately detects significant coronary artery stenosis and often changes management

OBJECTIVES

TEE is performed in many patients with ischemic stroke, and it is possible to examine the proximal coronaries by TEE in these patients. Our purpose was to (1) determine the accuracy of transesophageal echocardiography (TEE) in the diagnosis of proximal coronary stenosis in patients with ischemic stroke and (2) show that TEE detection of proximal coronary stenosis changed management in a substantial number of patients.

METHODS

Thirty-two patients with ischemic stroke undergoing TEE, in whom the proximal coronaries were examined and who had angiographic results available, were studied.

RESULTS

Proximal coronaries were visualized as follows: left main (LM) in 31 (97%), left anterior descending (LAD) in 32 (100%), left circumflex (LCx) in 30 (94%) and right coronary artery (RCA) in 21 (66%). The sensitivity and specificity of TEE in diagnosing significant coronary stenosis in visualized vessels were as follows: LM 100% and 100%, LAD 100% and 95%, LCx 100% and 96%, and RCA 100% and 100%, respectively. When visualized and nonvisualized segments were considered, TEE detected significant stenosis as follows: 4 of 5 in the LM (80%), 13 of 13 in the LAD (100%), 2 of 3 in the LCx (66%), and 2 of 8 in the RCA (25%). Of the 32 patients, TEE results changed management in 17 patients (53%). Angiographic findings resulted in 10 of the 17 patients (59%) undergoing revascularization.

CONCLUSIONS

TEE was very accurate in diagnosing significant coexisting coronary artery disease in patients with ischemic stroke. TEE diagnosis of these lesions prompted coronary angiography and subsequent revascularization in a substantial number of patients.

Lowering of blood pressure and coronary blood flow in isolated systolic hypertension

BACKGROUND

In essential hypertension, the lower limit of autoregulation of coronary flow shifts to higher perfusion and the hypertensive ventricle is at a higher than normal risk of ischemia, and less able to tolerate acute reduction of coronary perfusion pressure. Little is known about pattern of coronary flow in isolated systolic hypertension, a pathologic condition in which the elevated systolic blood pressure is associated with a lower than normal vascular compliance and normal or slightly greater than normal mean arterial pressure and vascular resistance.

OBJECTIVE

To evaluate the effects of rapid normalization of blood pressure on coronary blood flow in isolated systolic hypertension.

METHODS

We subjected 20 patients with isolated systolic hypertension to intraoperative hemodynamic and transesophageal echocardiographic monitoring during peripheral vascular surgery. Coronary flow velocity integrals and diameters in the left anterior descending coronary artery were evaluated under baseline conditions and after normalization of blood pressure, which occurred spontaneously during anesthesia (10 cases; group 1A) or was induced by infusion of nitrate (10 cases, group 1B).

RESULTS

After normalization of systolic blood pressure integrals decreased significantly only for patients in group 1A; percentage changes of diameter were significantly greater for patients in group 1B. Therefore, coronary blood flow after normalization of systolic blood pressure increased for patients in group 1B (by 28+/-25%) and decreased for patients in group 1A (by 30+/-21%). Changes in integrals were inversely related to those in diameter (r= -0.72, P < 0.001); for patients in group 1A changes in coronary perfusion pressure and diameter were related to those of integrals (r= 0.94; P < 0.0005).

CONCLUSIONS

In isolated systolic hypertension, despite there being similar changes of the systolic blood pressure, administration of nitrates caused a marked increase of coronary flow through direct effects on coronary circulation, whereas spontaneous normotension was associated with a significant reduction of coronary flow.

Transesophageal echocardiographic evaluation of coronary arteries for stenosis in the elderly patient

This article documents the ability of transesophageal echocardiography to provide adequate images and clinically relevant information about the coronary anatomy of the elderly patient. Transesophageal echocardiography is commonly used to assess elderly patients who suffer cerebral vascular accidents. It is important to evaluate not only for the usually suspected causes of a cardiac source of emboli but also for direct and indirect evidence of coronary artery disease--the leading cause of death in the elderly stroke patient. Because atherosclerotic cardiovascular diseases identified in one vascular bed are prone to universally involve the other vascular territories to some degree, it is not surprising that the coronary arteries are often stenotic. As a sudden event with catastrophic symptoms, a stroke is commonly the first vascular event the elderly patient experiences. Depending on the degree of recovery, physical limitations may contribute to the lack of symptoms from coexistent peripheral or coronary artery disease. Transesophageal echocardiography may be the first, or only, coronary evaluation for high-risk elderly patients.

Novel method for assessing myocardial perfusion: visualization and measurement of intramyocardial coronary blood flow in the entire left ventricular wall using contrast enhanced, high frequency Doppler echocardiography

Using a high frequency ultrasonic transducer, intramyocardial coronary blood flow (IM-CBF) can be visualized and evaluated during hemodynamic changes in the anterior wall and septum of the left ventricle (LV). We tested the hypothesis that detection and quantitative measurement of IM-CBF of entire LV segments are feasible using a high frequency ultrasonic transducer in conjunction with intravenous contrast injection in vivo. A 3 - 8 MHz transducer was used to image and measure IM-CBF in 10 anesthetized dogs. We obtained a color Doppler image of IM-CBF in the LV short-axis view after intravenous Levovist injection (25 mg/ml). The IM-CBF velocity was recorded using spectral Doppler in the antero-septal and infero-posterior wall of closed chest dogs and in the entire LV after opening the chest. A significant increase in IM-CBF velocity was observed in all LV regions after adenosine 5'- triphosphate (ATP) administration. After Levovist(TM) injection, the visualization of IM-CBF was improved and the spectral Doppler pattern of coronary flow velocity was clarified compared to baseline. IM-CBF was assessed in the antero-septal region of the LV before and after left anterior descending coronary artery occlusion. A high frequency ultrasonic transducer in conjunction with intravenous contrast injection improved IM-CBF visualization, enabling quantitative evaluation of the intramyocardial coronary circulation in the entire LV after coronary occlusion and hyperemia. This study may represent a step towards noninvasive assessment of myocardial perfusion before and after coronary reperfusion.

Transesophageal echocardiography (TEE) in the evaluation of the coronary arteries

With technical advancements, including high frequency, multiplane transducers, digital acquisition and display, and left-sided contrast agents, TEE is emerging as a promising method for evaluating coronary artery disease. Visualization of proximal coronary artery stenoses and coronary artery anomalies is already possible. Research studies using TEE measurement have contributed to understanding coronary artery physiology and may prove to be a valuable clinical tool in the future.

Echocardiographic assessment of coronary blood flow velocity during controlled hypotensive anesthesia with nitroglycerin

OBJECTIVE

To determine the effect of nitroglycerin on coronary blood flow velocity during controlled hypotensive anesthesia in humans.

DESIGN

Internally controlled prospective study.

SETTING

Single university hospital.

PARTICIPANTS

Twenty American Society of Anesthesiologists class I and II patients undergoing general anesthesia for surgical resection of a malignancy.

INTERVENTIONS

General anesthesia was induced with thiopental, fentanyl, and succinylcholine and maintained with isoflurane and vecuronium. Transesophageal echocardiography was used to evaluate left ventricular wall motion and blood flow velocity in the left anterior descending coronary artery. Intravenous nitroglycerin was used to reduce systolic arterial pressure to 60 to 70 mmHg. Intravenous albumin 5% was administered to maintain pulmonary capillary wedge pressure >5 mmHg.

MEASUREMENTS AND MAIN RESULTS

The left anterior descending coronary artery was visualized clearly in 16 of 20 patients. At a mean nitroglycerin dose of 16+/-14 microg/kg/min, peak diastolic left anterior descending flow velocity increased significantly from 32.5+/-10.3 cm/sec to 44.7+/-14.6 cm/sec (p = 0.0103). None of the patients developed any ST-segment changes.

CONCLUSIONS

During nitroglycerin-induced hypotensive anesthesia, coronary blood flow as assessed by peak diastolic left anterior descending flow velocity is preserved or increased in most patients. Increases in left anterior descending flow velocity are predictably achieved only at nitroglycerin doses >5 microg/kg/min. Intraoperative transesophageal echocardiography is useful in monitoring coronary flow velocity responses to controlled hypotensive anesthesia.

Transesophageal Echocardiographic Assessment of Proximal Coronary Artery Stenosis in Elderly Patients With Ischemic Stroke

Coronary artery disease is common in elderly patients with ischemic stroke. Most patients with ischemic stroke undergo transesophageal echocardiography to rule out cardiac sources of cerebral embolism. Transesophageal echocardiography has been shown to be very accurate in diagnosing significant proximal coronary artery stenosis, and may be used to evaluate the coronary arteries for the presence of stenosis in elderly patients with ischemic stroke. Transesophageal echocardiographic detection of these lesions might lead to subsequent coronary angiography and revascularization, dramatically changing the management and outcome of these patients. (c) 2000 by CVRR, Inc.

Definition of flow parameters in proximal nonstenotic coronary arteries using transesophageal Doppler echocardiography

Transesophageal echocardiography (TEE) enables the visualization of proximal coronary arteries. We investigated the feasibility of coronary flow evaluation using TEE, as well as to define flow parameters found in normal proximal coronary arteries. The subgroups of patients with normal proximal segments of coronary arteries were selected from the cohort of 210 patients undergoing routine coronary angiography. The left main coronary artery (LMCA), proximal segment of left anterior descending coronary artery (LAD), left circumflex artery (LCx), and right coronary artery (RCA) were analyzed separately in 147, 64, 53, and 70 patients, respectively. Proximal coronary arteries were evaluated in the transverse plane using a 5-MHz TEE probe, and the flow in normal arteries was registered using pulsed-wave Doppler. The registration of flow with pulsed-wave Doppler was feasible in 88% of studies for the LMCA, 85% for the LAD, 58% for the LCx, and 65% for the RCA. Normal flow was laminar with distinct phasic character (diastolic predominance). Mean +/- SD values of peak coronary flow velocity were (systole/diastole) for the LMCA, 36 +/- 11/71 +/- 19 cm/sec; the LAD, 31 +/- 9/67 +/- 19 cm/sec; the LCx, 36 +/- 13/75 +/- 24 cm/sec; and the RCA, 25 +/- 8/39 +/- 12 cm/sec. Peak diastolic coronary flow velocity was most significantly correlated with heart rate. Doppler evaluation of proximal coronary flow is feasible using TEE in the majority of patients. The knowledge of normal flow values, which is different for the left and the right coronary artery, provides the background for proper interpretation of flow in diseased coronary arteries.

The flow-function relationship in patients with chronic coronary artery disease and reduced regional function: a Doppler transesophageal and bidimensional transthoracic echocardiography study

BACKGROUND

Infra-low dose dipyridamole allows one to selectively explore myocardial viability. Transesophageal echocardiography Doppler measurement of left anterior descending coronary artery flow at baseline and following dipyridamole is an efficient tool to assess coronary flow response. Aim of this study was to determine the flow-function relationship during coronary vasodilatory stress in patients with coronary artery disease and baseline dysfunction.

METHODS AND RESULTS

Twelve patients with resting dyssynergies and 6 controls underwent assessment of regional function and of left anterior descending blood flow velocity. Flow and function were evaluated at rest and following infra-low dose dipyridamole (0.28 mg/Kg over 4 min). Controls showed a normal function at rest and after dipyridamole. Six patients ('Responders') with resting dyssynergies showed an improvement in segments of left anterior descending artery territory, whereas the other six ones ('Non-responders') showed no functional change. Controls and 'Responders' had similar values of resting peak diastolic left anterior descending artery flow velocity both at rest and after dipyridamole, whereas 'Non-responders' showed a blunted flow response to dipyridamole.

CONCLUSION

Myocardial segments with a resting dysfunction and a contractile reserve more often exhibit a residual flow response, whereas segments with fixed pattern show a flat flow response during coronary vasodilator stress.

Transesophageal Echocardiographic Diagnosis of Proximal Coronary Artery Stenosis in Patients with Ischemic Stroke

Atherosclerosis is the leading cause of death worldwide. It encompasses several clinical entities, including coronary artery disease and cerebrovascular disease. Because the underlying pathophysiological mechanism is the same, coronary artery disease and cerebrovascular disease frequently coexist. Transesophageal echocardiography (TEE) is routinely done in patients with ischemic stroke to exclude possible cardiac sources of cerebral embolism. Since the introduction of multiplane transesophageal transducers, it has become easier to visualize the proximal coronary arteries during transesophageal examinations. We report three cases in which routine TEE for ischemic stroke revealed significant coronary artery disease that was not previously suspected. In one patient, the stroke was so severe that further evaluation of the coronary artery disease was not deemed useful. The other two patients underwent coronary angiography based on the echocardiographic findings, confirming the lesions noted on the echocardiogram. Subsequently, both patients were successfully revascularized: one by percutaneous transluminal coronary angioplasty and the other by coronary artery bypass graft surgery. We conclude that the examination of coronary arteries during routine TEE for ischemic stroke may become a useful screening tool for the detection of coexisting, asymptomatic, significant proximal coronary artery disease.

Demonstration of penetrating intramyocardial coronary arteries with high-frequency transthoracic echocardiography and Doppler in human subjects

Characterization of intramyocardial coronary artery flow may offer insight into the spectrum of coronary physiology. The purposes of this study were to test the feasibility of detection and measurement of intramyocardial coronary artery flow by using high-frequency transthoracic ultrasound and to evaluate the hemodynamic and morphologic differences in intramyocardial coronary arteries between patients with echocardiographically normal myocardium and patients with diseased myocardium. In 116 subjects (age 58 +/- 19 years; male:female 67:49; 58 normal [control subjects], 40 with left ventricular hypertrophy [LVH], 18 with systolic left ventricular dysfunction [cardiomyopathy, CM]), we examined the myocardium just beneath the apical impulse window at a depth of 3 to 5 cm by using a 6- or 7-MHz centerline frequency transducer. For color Doppler examination, a special preset coronary program with a low Nyquist limit (12 to 20 cm) was used. After obtaining linear color signals, the width and length, peak and mean diastolic pulsed Doppler flow velocities, diastolic velocity time integrals, and percent duration of diastolic Doppler flow were measured. The number of linear color flow signals per square centimeter was counted in 520 different cardiac cycles, and the angles formed by their inner curvature was measured with a graduated protractor. We identified color flow Doppler signals within the myocardium having a mean width of 1.1 +/- 0.4 mm and flow direction from epicardium to endocardium in 104 (89. 7%) subjects and spectral Doppler signals in 74 (63.8%) subjects. In 33 (45.8%) subjects, only diastolic flow was detected and in 39 (54. 2%) subjects, diastolic flow was predominant with systolic reversal. Peak and mean diastolic flow velocities and velocity time integrals of spectral Doppler signal in control subjects were 26.2 +/- 8.6 cm/s, 19.0 +/- 6.3 cm/s, and 9.5 +/- 2.7 cm, respectively. There were no significant differences in width and density of linear color flow signals among the 3 groups. The color flow signals in the LVH and CM groups had a narrower angle of inner curvature (P <.005 for LVH, P <.05 for CM, respectively), and their spectral Doppler signals showed significantly higher diastolic velocities and shorter diastolic flow duration (P <.005 for LVH, P <.05 for CM, respectively) than those of the control subjects. Detection and measurement of flow signals consistent with penetrating intramyocardial coronary arteries are feasible in a high percentage of subjects by use of high-frequency transthoracic ultrasound. The findings in patients with LVH and CM suggest that there are distinct hemodynamic and morphologic departures from those with normal left ventricles that may be a consequence of disordered myocardial perfusion in diseased myocardium.

Use of the continuity equation for transesophageal Doppler assessment of severity of proximal left coronary artery stenosis: a quantitative coronary angiography validation study

OBJECTIVES

We tested the value of transesophageal Doppler echocardiography (TEDE) for quantitating proximal left coronary artery (LCA) stenosis by using the continuity equation.

BACKGROUND

The continuity equation applied to a stenosis states that the ratio of the time-velocity integral (TVI) of prestenotic to stenotic flow velocities is equal to the ratio of stenotic to prestenotic cross-sectional areas. TEDE allows the measurement of coronary blood flow velocities within the proximal part of the LCA. METHODS; Forty-one patients with a stenosis of the proximal or mid left anterior descending coronary artery or with a nonostial stenosis of the left main coronary artery were studied. Coronary flow velocities were recorded by TEDE guided by color flow imaging. Prestenotic velocities were recorded by pulsed Doppler echocardiography and transstenotic velocities were recorded by pulsed or high pulse repetition frequency or continuous wave Doppler echocardiography. The prestenotic and transstenotic diastolic TVIs were calculated and the TEDE-derived percent area stenosis was calculated as (1 - TVI ratio) x 100. Quantitative angiography lesion analysis was performed using a computer-assisted automated edge-detection system.

RESULTS

TEDE recordings were successful in 35 of the 41 patients. A good linear correlation was found between TEDE and quantitative angiographically derived percent area stenosis (r = 0.89, p = 0.0001, SEE 5.7). However, TEDE measurements underestimated the actual percent area stenosis (slope of regression 0.54). A better agreement (slope 1.08) was obtained after dividing prestenotic velocity by 2 in the continuity equation, based on the assumption of a parabolic cross-sectional velocity profile in the prestenotic segment.

CONCLUSIONS

TEDE may be used for quantitating stenosis of the proximal part of the LCA with the use of a modified continuity equation that takes into account the parabolic velocity profile in the normal prestenotic segment.

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

BACKGROUND

The intracoronary Doppler tipped guide wire has been shown to be highly accurate in the measurement of coronary flow velocity (CFV). Recent studies have indicated that blood flow velocity in the left anterior descending coronary artery (LAD) can be determined by transesophageal echocardiography (TEE). The purpose of this study was to compare flow velocity recordings and coronary flow reserve measurements in the LAD by TEE with those obtained by Doppler guide wire.

METHODS AND RESULTS

The study population consisted of 14 patients with chest pain and normal coronary arteriograms. After routine coronary arteriography was performed, a 0.014-inch Doppler guide wire was advanced into the proximal part of the LAD. After baseline measurement of coronary flow velocity (CFV) was obtained, 140 microg/kg/min adenosine was administered intravenously for 3 minutes, and the flow velocity was recorded. TEE was performed within 24 hours of the cardiac catheterization. After baseline measurements of CFV in the LAD, heart rate, and blood pressure were obtained, 140 microg/kg/min adenosine was administered intravenously, and the CFV was recorded. Coronary flow reserve was calculated as the ratio of the peak diastolic CFV during adenosine infusion to the peak diastolic CFV at baseline. A good correlation was found (r = 0.91, p < 0.0001) between CFV by Doppler guide wire and that determined by TEE. A good correlation was also found between the coronary flow reserve assessed by Doppler guide wire and that determined by TEE (r = 0.92, p < 0.0001).

CONCLUSION

Our data indicate that CFV and coronary flow reserve in the LAD can be accurately measured by transesophageal echocardiography.

Transesophageal Doppler evaluation of left anterior descending coronary artery angioplasty

Transesophageal Doppler echocardiography can noninvasively evaluate the functional results of left anterior descending coronary artery angioplasty. Coronary flow reserve assessed by this technique is significantly increased only in those patients with less severe residual stenosis as detected by intravascular ultrasound, thus allowing a noninvasive assessment of the results of left anterior coronary artery angioplasty.

Assessment of coronary artery aneurysms with multiplane transesophageal echocardiography

Coronary artery aneurysms are rare and may be difficult to detect clinically. Multiplane transesophageal echocardiography provides numerous imaging planes that may improve the assessment of coronary aneurysms and act as an adjunct to standard angiography. Five patients with angiographically detected coronary aneurysms were studied with multiplane transesophageal echocardiography and Doppler flow imaging. Transesophageal echocardiography was successful in identifying the size and characteristics of the coronary aneurysms. Doppler ultrasound identified markedly increased flow velocity in a patient with a coronary arteriovenous fistula and decreased coronary flow velocity in two patients with aneurysmal coronary arteries and intracoronary thrombus. Multiplane transesophageal echocardiography is a useful, noninvasive method of assessing coronary artery aneurysms and may act as an adjunct to angiography in identifying fistula anastomosis.

Coronary flow reserve assessed by transesophageal echocardiography identifies early restenosis of the left anterior descending coronary artery angioplasty

Although an increase in diastolic coronary flow velocity can be detected by transesophageal echocardiography 72 hours after both successful and unsuccessful left anterior coronary artery angioplasty, a significant improvement in coronary flow reserve is observed only in patients with a successful procedure. Transesophageal echocardiography-derived coronary flow reserve can identify early restenosis and thus serve as an index of the outcome of the procedure.

Determination of coronary flow measurements by transesophageal echocardiography: dependence of flow velocity reserve on the location of stenosis

Doppler velocimetry with the use of transesophageal echocardiography can record flow in the proximal left anterior descending artery (LAD). To assess whether this limited sampling ability influences the recording of velocity and the calculation of coronary flow reserve (CFR), 32 patients with LAD stenosis (4 ostial stenoses, 18 proximal stenoses, 10 mid-LAD stenoses) and 33 patients with arteriographically normal LADs were studied. Basal flow and dipyridamole-induced hyperemic flow rates were recorded. The mean basal flow velocity in ostial stenoses was greater than in other groups, and the mean basal flow velocity in proximal stenoses was less than that in mid-LAD stenoses and in the normal group. Maximal hyperemic velocity did not differ between the groups. CFR in all stenoses groups was less than that in the normal group. Ostial CFR was less than in all other groups, and proximal CFR was less than that in either the mid-LAD or the normal LAD groups. With this technique, coronary flow velocimetry and estimation of CFR is affected by the location of stenosis.

Influences of aortic pressure gradient and ventricular septal thickness with systolic coronary flow in aortic valve stenosis

This study evaluates flow patterns of the left anterior descending and circumflex coronary arteries by multiplane transesophageal echocardiography in 25 patients with aortic valve stenosis, and assesses the relation between coronary flow characteristics and anatomic and hemodynamic parameters.

Usefulness of dipyridamole transesophageal echocardiography in the evaluation of myocardial ischemia and coronary artery flow

High-dose dipyridamole transesophageal stress echocardiography has recently been proposed as a useful and safe method to assess myocardial ischemia in patients with poor transthoracic acoustic window. It has also been shown that transesophageal echocardiography (TEE) allows the study of coronary blood flow reserve (CBFR) in the left anterior descending artery (LAD). The aim of our study was to assess whether the morphologic information and pathophysiologic data on CBFR and myocardial ischemia can be collected by a single stress TEE without comprimizing its feasibility, safety and accuracy. We studied, 29 patient with known or suspected CAD (previous myocardial infarction or angina) (Group A), and as a control group, we studied 11 patients with mitral disease or mitral prostheses (Group B). All patients underwent the coronary angiography. None of Group B patients showed significant coronary artery stenosis (> 70%). In baseline conditions left ventricular wall motion and LAD coronary blood flow velocity (CBFV) were also evaluated. The following CBFV parameters were measured: maximal diastolic velocity (MaxDV), mean diastolic velocity (MnDV), maximal systolic velocity (MaxSV), mean systolic velocity (MnSV). The ratios of dipyridamole to rest maximal and o mean to diastolic velocities (MaxDV-Dip/Max DV-rest; MnDv-Dip/MnDV-rest) were measured as indexes of CBFR. No side effects were observed and the test could be completed in all patients (feasibility 100%). Wall motion analysis was adequate in all patients (feasibility 100%). Comparison between wall motion analysis was obtained and angiographic findings shown that the overall sensitivity and specificity of TEE were 84% and 93% respectively. Sensitivity for one, two and three vessel disease was 60%, 70% and 100%, respectively. LAD CBFV was adequately recorded in 85% of patients. CBFR parameters showed a significant difference between the two groups (Max DV-Dip/Max DV-rest: 1.67 +/- 0.7 vs. 2.73 +/- 0.6, P < 0.001); comparison between Group B patients and those of Group A with angiographically documented LAD stenosis showed a statistically significant difference in CBFR parameters (MaxDV-Dip/MnDV-rest, 2.73 +/- 0.6 vs. 1.65 +/- 0.7, P < 0.001, MnDV-Dip/MnDV-rest, 2.56 +/- 0.5 vs. 1.69 +/- 0.6 < 0.001). We conclude that transesophageal stress echocardiography is a useful method to study CAD and that it is possible to assess both morphologic and pathophysiologic information during a single examination.

Usefulness of transoesophageal echocardiography in showing the route of anomalous coronary arteries

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Coronary haemodynamics in left ventricular hypertrophy

BACKGROUND

Left ventricular hypertrophy is associated with an increased risk of cardiovascular morbidity and mortality. Previous studies have shown that patients with left ventricular hypertrophy develop electrocardiographic changes and left ventricular dysfunction during acute hypotension, and suggest that the lower end of autoregulation may be shifted upwards.

AIM

To measure coronary blood flow (velocity) and flow reserve during acute hypotension in patients with left ventricular hypertrophy.

PATIENTS

Eight patients with atypical chest pain and seven with hypertensive left ventricular hypertrophy; all with angiographically normal epicardial vessels.

SETTING

Tertiary referral centre.

METHODS

The physiological range of blood pressure was determined by previous ambulatory monitoring. Left ventricular mass was determined by echocardiography. At cardiac catheterisation, left coronary blood flow velocity was measured using a Judkins style Doppler tipped catheter. During acute hypotension with sodium nitroprusside, coronary blood flow velocity was recorded at rest and during maximal hyperaemia induced by intracoronary injection of adenosine. Quantitative coronary angiography was performed manually.

RESULTS

For both groups coronary blood flow velocity remained relatively constant over a range of physiological diastolic blood pressures and showed a steep relation with diastolic blood pressure during maximal hyperaemia with intracoronary adenosine. Absolute coronary blood flow (calculated from quantitative angiographic data), standardised for left ventricular mass, showed reduced flow in the hypertensive group at rest and during maximal vasodilatation.

CONCLUSION

The results are consistent with an inadequate blood supply to the hypertrophied heart, but no upward shift of the lower end of the autoregulatory range was observed.

Effects of intraaortic balloon pumping on septal arterial blood flow velocity waveform during severe left main coronary artery stenosis

OBJECTIVES

We sought to evaluate the effect of intraaortic balloon pumping on the phasic blood velocity waveform into myocardium with severe coronary artery stenosis.

BACKGROUND

In the presence of severe coronary artery stenosis, it is not clear whether intraaortic balloon pumping augments intramyocardial inflow during diastole or changes systolic retrograde blood flow from the myocardium to the extramural coronary arteries.

METHODS

Using anesthetized open chest dogs (n=7), we introduced severe stenosis in the left main coronary artery to reduce the poststenotic pressure to approximately 60 mm Hg (>90% diameter stenosis). Septal arterial blood flow velocities were measured with a 20-MHz, 80-channel ultrasound pulsed Doppler velocimeter. Left anterior descending arterial flow, aortic pressure and poststenotic distal coronary pressure were measured simultaneously. The diastolic anterograde flow integral and systolic retrograde flow integral were compared in the presence and absence of intraaortic balloon pumping.

RESULTS

Although intraaortic balloon pumping augmented diastolic aortic pressure, this pressure increase was not effectively transmitted through stenosis. Septal arterial diastolic flow velocity was not augmented, and left anterior descending arterial flow was unchanged during intraaortic balloon pumping.

CONCLUSIONS

In the presence of severe coronary artery stenosis, intraaortic balloon pumping failed to increase diastolic inflow in the myocardium and did not enhance systolic retrograde flow from the myocardium to the extramural coronary artery. Thus, the major effect of intraaortic balloon pumping on the ischemic heart with severe coronary artery stenosis may be achieved by reducing oxygen demand by systolic unloading.

Transesophageal Doppler echocardiographic assessment of left coronary blood flow velocity in chronic aortic regurgitation

Assessment of systolic and diastolic coronary blood flow velocities (FVs) in patients with aortic regurgitation (AR) has remained a clinical challenge. We recorded left anterior descending coronary blood FV in 21 patients with chronic AR an in 6 control subjects using transesophageal pulsed Doppler echocardiography. In 7 patients FV was measured 4.0 +/- 5.2 months after aortic valve replacement. Peak and mean FVs during systole and diastole and systolic/diastolic ratios of these FVs were determined. Left ventricular (LV) mass index was calculated by means of standard M-mode echocardiography. In patients with severe AR, peak and mean systolic FVs were significantly increased (34 +/- 8 cm/sec and 21 +/- 6 cm/sec, respectively) compared with FVs in the control group (15 +/- 4 and 12 +/- 3 cm/sec, respectively) and in patients with mild AR (17 +/- 3 cm/sec and 13 +/- 2 cm/sec, respectively). Peak and mean systolic FVs were also significantly increased in severe AR (54 +/- 13 cm/sec and 33 +/- 9 cm/sec, respectively) compared with FVs in the control (30 +/- 8 cm/sec and 21 +/- 5 cm/sec, respectively) and mild AR groups (30 +/- 5 cm/sec and 21 +/- 4 cm/sec, respectively). Peak systolic and diastolic FVs were correlated significantly with LV mass index (r = 0.72 and r = 0.73, respectively). Systolic and diastolic FVs and LV mass index were significantly decreased, normalized or both after aortic valve surgery. In conclusion, LV mass seems to have an effect on the significantly increased systolic and diastolic left coronary blood FV pattern in patients with chronic, severe AR. Increased systolic and diastolic FV appears to be normalized in the late period after surgery.

Transesophageal echocardiography in myocardial ischemia: a review

This article reviews established as well as emerging fields in the application of transesophageal echocardiography (TEE) in the investigation of myocardial ischemia. TEE already has a well defined and established role in stress echocardiography in patients with poor transthoracic acoustic window, and in the detection of intraoperative myocardial ischemia in cardiac and noncardiac surgery. The evaluation of right ventricular ischemia and infarction and the assessment of coronary flow reserve (CFR) are relatively new fields in the application of TEE and the potential of this technique has not yet been fully evaluated. The evidence collected and reviewed in this article is still preliminary but it presupposes a significant role of TEE in the diagnosis and pathophysiological assessment of myocardial ischemia.

Adenosine-induced coronary vasodilation during transesophageal Doppler echocardiography. Rapid and safe measurement of coronary flow reserve ratio can predict significant left anterior descending coronary stenosis

BACKGROUND

Less invasive methods are replacing traditional invasive means of measuring coronary flow reserve (CFR). Transesophageal echocardiography (TEE) is becoming a useful tool for evaluation of coronary artery disease and has recently been used to measure CFR. This has always been done using dipyridamole, but adenosine has a greater vasodilator potency and more favorable kinetics than dipyridamole. This study was done to evaluate the hypothesis that adenosine is safe, rapid, and accurate in measuring coronary blood flow reserve by TEE Doppler.

METHODS AND RESULTS

Forty-nine patients who had recently undergone angiography had a transesophageal echocardiogram with visualization of the coronary arteries and measurement of blood flow velocity in the left anterior descending coronary artery (LAD) during adenosine infusion of 0.14 mg/kg per minute. Angiograms were analyzed by quantitative coronary angiography, and significant stenosis was defined as > 70% lumenal diameter narrowing. Thirty-nine of the 49 patients did not have a significant LAD stenosis (group 1); the remainder had significant disease (group 2). Good spectral Doppler recordings of blood flow velocity in the LAD were obtained in 41 of 46 patients (89%). There were no significant differences in baseline coronary blood flow velocities between the two groups. Hyperemic to baseline flow ratios were significantly higher in patients without significant LAD stenosis for peak (2.83 +/- 1.04 versus 1.78 +/- 0.36) and mean (2.68 +/- 0.96 versus 1.75 +/- 0.39) diastolic velocity. A CFR ratio > 2.1 had a sensitivity of 86%, a specificity of 79%, a positive predictive value of 46%, and a negative predictive value of 96% for the absence of critical LAD stenosis. The infusion was well tolerated. It had to be prematurely terminated in only 3 patients (6.5%), and they were asymptomatic. No patient experienced chest pain, palpitations, or flushing. Intraobserver and interobserver variabilities were low, and reproducibility of data was good (< 4%).

CONCLUSIONS

Adenosine Doppler TEE is an effective, rapid, safe, and superior means of measuring CFR ratio. This method is convenient for serial measurements of CFR as well as in clinical settings such as evaluation of syndrome X, cardiomyopathy, and aortic regurgitation.

Coronary flow reserve assessment by dobutamine transesophageal Doppler echocardiography

OBJECTIVES

This study attempted to determine the sensitivity and specificity of coronary flow reserve derived using transesophageal echocardiography for left anterior descending coronary artery stenosis.

BACKGROUND

Transesophageal echocardiography can be used to measure coronary flow velocity and may provide a less invasive means of assessing coronary flow reserve.

METHODS

Seventy-eight adult patients were studied by pulsed Doppler transesophageal echocardiography of the proximal left anterior descending coronary artery during a control period and peak (i.e., 40 micrograms/kg body weight per min) dobutamine infusion. Coronary flow reserve index was calculated as the ratio of maximal diastolic coronary velocity at peak dobutamine infusion to the control level and was considered abnormal if < 1.81. Two-dimensional transesophageal left ventricular views were obtained for analysis of wall motion.

RESULTS

Coronary angiography showed > or = 70% (group A, n = 18), 0% to < 70% (group B, n = 21) and no (group C, n = 39) left anterior descending coronary artery diameter stenosis. An abnormal coronary flow reserve index did not differ from a new regional wall motion abnormality in sensitivity for left anterior descending coronary stenosis in group A (15 [83%] of 18 vs. 15 [83%] of 18, p = NS) but was significantly more sensitive in group B (12 [57%] of 21 vs. 2 [10%] of 21, p < 0.025). The specificity for no left anterior descending coronary stenosis in group C between a normal coronary flow reserve index and no new regional wall motion abnormality did not differ (87% vs. 97%, p = NS).

CONCLUSION

Doppler coronary flow reserve and two-dimensional dobutamine transesophageal echocardiography are equally sensitive for the detection of left anterior descending coronary stenosis > or = 70% and equally specific. However, Doppler coronary flow reserve, compared with two-dimensional dobutamine transesophageal echocardiography, is more sensitive for intermediate left anterior descending coronary stenosis and may play a significant adjunctive role to cardiac catheterization and other noninvasive techniques for assessing coronary artery disease.

Delineation of extended lengths of coronary arteries by multiplane transesophageal echocardiography

OBJECTIVES

The purpose of this study was to evaluate the utility of multiplane transesophageal echocardiography in assessing the coronary artery tree.

BACKGROUND

Evaluation of coronary disease with single-plane and biplane transesophageal echocardiography is limited to the very proximal vessels. The numerous views provided by multiplane imaging may enhance visualization of coronary arteries and detection of their abnormalities.

METHODS

Intraoperative multiplane transesophageal echocardiography was performed in 45 consecutive adults who had recently undergone angiography. Recordings were reviewed in blinded manner.

RESULTS

We describe the coronary segments visualized with the different imaging planes and define new views. The left main coronary artery with its bifurcation was visualized in all 45 patients. Sensitivity and specificity for detection of coronary narrowings were 100% when results were compared with angiographic data. Visualization of proximal, mid and distal segments of the left anterior descending coronary artery was possible in 69%, 31% and 16% of patients, respectively. Among patients in whom the proximal segment was visualized, sensitivity and specificity for detection of significant narrowings were 80% and 100%. Proximal, mid and distal portions of the left circumflex coronary artery were visualized in 80%, 51% and 20% of patients. Among patients in whom the proximal portion was well seen, sensitivity and specificity were 89% and 100%. The proximal, mid and distal portions of the right coronary artery were visualized in 84%, 16% and 11% of patients. Among patients in whom the proximal segment was visualized, sensitivity and specificity were 82% and 100%. Color Doppler examination was less useful because it detected only 52% of all patients with proximal stenosis.

CONCLUSIONS

Multiplane transesophageal echocardiography allows enhanced visualization of extended lengths of coronary arteries and the reliable identification of coronary artery abnormalities.

Abnormal coronary flow velocity pattern in patients with left ventricular hypertrophy, angina pectoris, and normal coronary arteries: a transesophageal Doppler echocardiographic study

Previous invasive studies have suggested that coronary flow reserve is impaired in patients with left ventricular hypertrophy (LVH) and symptoms of ischemia. We tested whether transesophageal Doppler, a semiinvasive technique, can detect altered characteristics of baseline coronary blood flow velocity in such patients. Thirty patients with LVH (hypertrophic cardiomyopathy in 4, aortic stenosis in 17, hypertension in 9) were studied. Fourteen patients had asymptomatic LVH. Sixteen patients had clinical symptoms of ischemia with angiographically normal epicardial coronary arteries. Ten subjects with no cardiovascular disease were studied as a control group. Peak diastolic and systolic coronary flow velocities were recorded in the proximal part of the left anterior descending artery (LAD) with the use of pulsed Doppler guided by color flow imaging. Patients with symptomatic LVH had higher diastolic peak coronary flow velocity (81 +/- 10 cm/sec, p = 0.0001) compared with normal subjects (41 +/- 8 cm/sec) and patients with asymptomatic LVH (44 +/- 8 cm/sec). In patients with asymptomatic LVH the diastolic coronary flow velocity/indexed ventricular mass ratio was lower (0.28 +/- 0.09 cm/gm/m2, p = 0.0001) compared with symptomatic patients (0.52 +/- 0.12 cm/gm/m2) and compared with controls (0.47 +/- 0.16 cm/gm/m2). Patients with symptomatic LVH but no aortic stenosis also had higher peak systolic coronary flow velocity (38 +/- 9 cm/sec) compared with the other groups (p = 0.0001). In the group of patients with aortic stenosis a significant inverse linear relation was found between peak systolic coronary flow velocity and peak pressure gradient (r = -0.60, p 0.01). In conclusion, patients with symptomatic LVH have abnormally high baseline coronary flow velocities resulting in magnified intimal shear stress. Because flow velocity equals flow/vessel cross-sectional area, it is suggested that high coronary flow velocities in patients with symptomatic LVH result from both augmented coronary flow and failure of the vessel to enlarge commensurately with the increase in LV mass (relative functional stenosis). In patients with aortic stenosis, peak systolic coronary flow velocity appears to be influenced by transvalvular pressure drop.

Increased sensitivity of flow detection in the left coronary artery by transesophageal echocardiography after intravenous administration of transpulmonary stable echocontrast agent

Transesophageal echocardiography (TEE) combined with color and pulsed Doppler allows a noninvasive assessment of flow in the proximal anterior descending coronary artery (LAD). The aim of this study was to assess whether the peripheral administration of a transpulmonary stable echocontrast agent with prolonged in vivo stability may improve the feasibility and accuracy of coronary flow detection by TEE Doppler. In 12 out of 14 consecutive patients undergoing routine diagnostic TEE examination, color-coded images of left main coronary artery (LM) and the origin of the LAD and circumflex artery (CXA), as well as spectral Doppler signals from the LAD, were evaluated before and after intravenous injection of SHU 508 A. After administration of echocontrast material, the coronary Doppler signal (both color-coded and spectral) was enhanced for approximately 100 seconds. The length and diameter of color-coded flow increased significantly in the LM, LAD, and CXA. (The length of color-coded flow before and after injection of contrast material were the following: in LM 0.94 +/- 0.44 versus 1.39 +/- 0.52 cm, p < 0.001; in LAD 0.68 +/- 0.36 versus 1.20 +/- 0.41 cm, p < 0.001; and in CXA 0.54 +/- 0.20 versus 1.06 +/- 0.86 cm; in this artery, color-coded flow was visualized only in six patients before and 11 patients after injection of contrast material. The corresponding values for the diameters of color-coded flow in LM were 0.36 +/- 0.08 versus 0.46 +/- 0.09 cm, p < 0.001; in LAD 0.29 +/- 0.07 versus 0.41 +/- 0.1 cm, p < 0.002; and in CXA 0.26 +/- 0.05 versus 0.40 +/- 0.04 cm.) By pulsed Doppler, significant increments in peak diastolic (47.8 +/- 21.3 versus 37.2 +/- 14.5 cm/sec, p < 0.05), mean diastolic (37.4 +/- 14.7 versus 27.9 +/- 8.4 cm/sec, p < 0.005), mean systolic flow velocity (23.2 +/- 6.8 versus 19.0 +/- 4.7 cm/sec, p < 0.005), and diastolic (11.0 +/- 3.9 versus 7.7 +/- 3.0 cm, p < 0.001) and total flow integral (16.8 +/- 5.3 versus 10.5 +/- 4.6 cm, p < 0.001) were observed. By contrast, peak systolic velocity did not increase. However, the systolic component of coronary flow, detectable in 7 out of 12 patients before injection of contrast material, became detectable in all 12 patients after injection of contrast material.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of coronary artery stenoses and poststenotic blood flow patterns using a miniature high-frequency epicardial transducer

BACKGROUND

Intraoperative epicardial coronary Doppler ultrasound has the potential to provide anatomic and functional information. This technique has been hindered by the large size of standard transducers, but a miniature transducer is available that may fulfill the potential of coronary ultrasound.

METHODS AND RESULTS

Twenty consecutive patients who were undergoing coronary artery bypass grafting were studied and compared with 9 control patients with normal coronary arteries who were undergoing routine mitral valve surgery. A miniature 6.5-MHz transducer was used to image coronary arteries and measure coronary blood flow velocities. Seventeen proximal left anterior descending and 3 right coronary artery stenoses were studied. As defined by coronary angiography (1 to 34 days before surgery), there were 13 severe stenoses (> 70%), 4 moderate stenoses (40% to 70%), 2 minor stenoses (< 40%), and 1 subtotal occlusion. Stenoses were readily identified by ultrasound. Color flow mapping demonstrated laminar flow in normal arteries and nonlaminar flow across moderate and severe stenoses. In the control patients with unobstructed arteries, peak and mean diastolic velocities were 35 +/- 2.1 and 26 +/- 1.9 cm/s with peak and mean systolic velocities of 16 +/- 1.4 and 11 +/- 0.8 cm/s, respectively. Prestenotic flow velocities were not significantly different from normal control values, but a wide range of poststenotic flow disturbances were detected. Analysis of the 20 study patients did not reveal significant differences in poststenotic compared with prestenotic flow. A subgroup analysis of 12 patients with severe left anterior descending coronary artery stenoses was performed, and reversed poststenotic systolic flow was seen in 9. Prestenotic peak and mean systolic velocities were 16.5 +/- 1.7 and 11.9 +/- 1.1 cm/s, respectively, and were significantly altered downstream of the stenoses at -22.7 +/- 17.2 and -15.9 +/- 10.9 cm/s (P < .05 and P < .01, respectively). Reversed systolic flow was seen only distal to severe left anterior descending coronary artery stenoses and did not correlate with retrograde collateral filling as determined by preoperative coronary angiography. Moderate stenoses appeared to increase both systolic and diastolic components of poststenotic flow.

CONCLUSIONS

Epicardial Doppler ultrasound with a miniature transducer identifies coronary stenoses and associated blood flow disturbances. Compared with moderate lesions, severe stenoses demonstrated different poststenotic flow patterns. Intraoperative use of this technique may determine the hemodynamic significance of coronary stenoses.

Assessment of flow profile of left anterior descending coronary artery in hypertrophic cardiomyopathy by transesophageal pulsed Doppler echocardiography

This study assessed the flow velocity profiles of the left anterior descending coronary artery (LAD) in 7 patients with nonobstructive hypertrophic cardiomyopathy (HC) and in 6 normal subjects by transesophageal pulsed Doppler echocardiography, and evaluated their characteristics and the hemodynamic determinants. Systolic peak flow velocity of the LAD (7 +/- 30 cm/sec) was significantly lower in patients with HC than in normal subjects (34 +/- 11 cm/s, p < 0.05), and there was a significant inverse correlation between systolic peak flow velocity and the thickness of the ventricular septum (r = 0.81, p < 0.01). In 2 cases of HC with ventricular septal thickness of > 20 mm, a remarkable systolic reverse flow was observed in the LAD. However, there was no significant difference in diastolic peak flow velocity between HC and normal subjects. During early diastole, the acceleration time of LAD flow velocity was significantly prolonged (210 +/- 67 vs 95 +/- 15 ms, p < 0.01) and the acceleration rate was significantly decreased (3.6 +/- 2.0 vs 6.6 +/- 1.8 m/s2, p < 0.02) in patients with HC. The time constant of the left ventricular pressure decay was significantly prolonged in patients with HC (55 +/- 6 ms) compared with normal subjects (39 +/- 2 ms, p < 0.001). In HC, increased intramural perivascular pressure of the thickened ventricular septum during systole may be attributed to systolic LAD flow pattern. However, the early and mid-diastolic LAD flow pattern may be affected by impaired left ventricular relaxation.

Noninvasive assessment of coronary flow dynamics before and after coronary angioplasty using transesophageal Doppler

Recent invasive studies using intracoronary Doppler catheters or guide wires reported improved coronary flow dynamics after successful percutaneous transluminal coronary angioplasty. Transesophageal Doppler enables the measurement of coronary flow velocities within the left anterior descending artery. The present study was designed to test: (1) whether transesophageal Doppler may detect coronary flow velocity changes in patients undergoing angioplasty for left anterior descending artery stenosis, and (2) whether this technique may help to evaluate non-invasively the results of the procedure. Twenty-three patients undergoing angioplasty of the left anterior descending artery were studied by transesophageal Doppler before and < or = 24 hours after the interventional procedure. Coronary flow velocities were measured in the proximal part of the left anterior descending artery with the use of pulsed Doppler guided by color flow imaging. The degree of stenosis was measured by computerized quantitative coronary arteriography. Coronary flow velocity signals were successfully obtained in 19 of 23 patients (83%). In 16 successful angioplasty procedures, peak diastolic velocity increased from 37 +/- 14 cm/s before angioplasty to 51 +/- 16 cm/s after (p = 0.0001). In the 3 patients in whom angioplasty was unsuccessful, transesophageal Doppler showed no significant increase in peak diastolic coronary flow velocity. In a total of 19 angioplasty procedures, a good linear relation was found between the percent changes in coronary flow diastolic velocity and the reduction in the degree of stenosis (r = 0.85; p = 0.0001). All patients with > 20% increase in peak diastolic velocity had > 40% stenosis reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Left main coronary flow velocity associated with stenosis. Evaluation by transesophageal color-guided pulsed Doppler technique

To quantitatively estimate the extent of left main coronary artery (LMCA) stenosis, flow velocity of the LMCA in 33 patients was analyzed by a transesophageal color-guided pulsed Doppler technique. In 11 of 20 patients with LMCA stenosis, coronary flow velocity could be measured. The peak diastolic flow velocity at the stenotic segments was 90 +/- 32 (SD) cm/s which was significantly greater than that at the nonstenotic segments (n = 13; 34 +/- 8 cm/s; p < 0.01), and was correlated with the angiographically determined percentage of diameter stenosis of the vessel which ranged from 52 to 90 percent (r = 0.77; y = 6.34 square root of x + 10.4; p < 0.01). These results suggest that acceleration of flow velocity at the point of stenosis may be correlated with the severity of the stenosis. Measurement of flow at the point of stenosis by transesophageal color-guided pulsed Doppler technique may facilitate the quantitative assessment of LMCA stenosis, although its sensitivity requires improvement.

Complementary role of transoesophageal echocardiography to coronary angiography in the assessment of coronary artery anomalies

OBJECTIVE

To examine the role of transoesophageal echocardiography in the assessment of patients with coronary artery anomalies.

BACKGROUND

Coronary artery anomalies are difficult to detect clinically. Most are benign but some may produce symptoms that can be life threatening. Until recently the non-invasive assessment of coronary artery anomalies has been limited.

METHODS

The data base of transoesophageal echocardiographic studies performed between September 1988 and April 1991 were reviewed to identify all cases of coronary artery anomalies. There were six patients with such anomalies who had also had coronary angiography. The findings of these two imaging techniques were analysed to determine whether transoesophageal echocardiography added useful data in these cases.

RESULTS

Of the six patients, the coronary anomaly was discovered during angiography in four patients, during a transthoracic echocardiographic study in one patient, and as an incidental finding in the other patient. Aberrant origins of the left coronary artery were detected in two patients, and coronary artery fistulae were present in the other four. Transoesophageal echocardiography provided unique information on the course of an aberrant left coronary artery in one patient and the precise location of drainage sites of coronary artery fistulas in three patients.

CONCLUSION

Transoesophageal echocardiography was complementary to angiography in the assessment of coronary artery anomalies. It can locate and delineate the course of an ectopic coronary artery and the drainage site of a coronary fistula. These anatomical data can be crucial to the management of these patients.

Intraoperative measurement of saphenous vein bypass graft flow with transesophageal echocardiography

The value of transesophageal echocardiography (TEE) for detecting saphenous vein coronary graft (SVG) flow was investigated. Thirty-five consecutive patients undergoing elective coronary artery bypass grafting (CABG) were studied intraoperatively. SVG flow characteristics obtained by TEE were compared with those gathered by an electromagnetic flowmeter (EMF). A total of 59 patent bypass grafts were examined. Pulsed-wave Doppler signals could be detected in 38/59 of the grafts studied (64.4%). The detection rate was the same for all types of grafts encountered (left anterior descending, right coronary, left circumflex, and lateral ventricular branches). The flow profiles obtained by TEE were very similar to those detected by EMF. Both profiles showed a bifid appearance with maximal flow in late diastole. The peak velocity seen in a SVG during diastole was 39.0 +/- 12.7 cm/sec. Graft volume determined by TEE correlated well with data obtained by EMF (r = 0.84). TEE is an attractive technique for noninvasively detecting phasic flow in SVGs; however, the flow detection rate is too low for the routine evaluation of graft patency.

The role of transesophageal echocardiography in cardiac donor screening

Transthoracic echocardiography has played a useful role in the screening of cardiac transplant donors. However, transthoracic echocardiograms may be suboptimal in many patients on ventilators. The role of transesophageal echocardiography in cardiac donor screening is unknown. Therefore we compared the potential benefit of transesophageal echocardiography combined with transthoracic echocardiography in 24 (16 men and 8 women) consecutive brain-dead patients with a mean age of 29 +/- 9 years (range 16 to 44 years), who were being considered as cardiac transplant donors. Transthoracic echocardiography was performed immediately before or after transesophageal echocardiography. Transthoracic echocardiography was technically difficult in 7 of 24 (29%) patients. Results of transesophageal echocardiography were abnormal in five of the seven patients and demonstrated left (n = 4) and right (n = 3) ventricular wall motion abnormalities and concentric left ventricular hypertrophy (n = 2). The four patients with wall motion abnormalities were eliminated as potential donors. In 16 of 17 patients with technically adequate transthoracic echocardiograms, transesophageal and transthoracic echocardiographic findings agreed and demonstrated normal hearts in 13 patients, left (n = 2) and right (n = 1) ventricular wall motion abnormalities in two patients, and isolated concentric left ventricular hypertrophy in one patient. In 1 of the 17 patients with a technically adequate transthoracic echocardiographic study, a bicuspid aortic valve was demonstrated by transesophageal echocardiography but not diagnosed by transthoracic echocardiography. Overall seven patients were eliminated as cardiac donors on the basis of transesophageal echocardiograms (n = 7), transthoracic echocardiograms (n = 2), or both.(ABSTRACT TRUNCATED AT 250 WORDS)

Augmentation of coronary blood flow by intra-aortic balloon pumping in patients after coronary angioplasty

BACKGROUND

Controversy exists regarding the ability of intra-aortic balloon pumping to increase coronary blood flow in patients with obstructive coronary artery disease. To assess the effects of intra-aortic balloon pumping on coronary hemodynamics, we measured coronary blood flow velocity with a 0.018-in. Doppler-tipped angioplasty guide wire in 15 patients who received an intra-aortic balloon pump for typical clinical indications.

METHODS AND RESULTS

Intra-aortic balloon pumping augmented diastolic pressure 83 +/- 35%. In nine patients before angioplasty, peak diastolic coronary flow velocity beyond the stenosis (mean diameter narrowing, 95 +/- 7%) was 5.3 +/- 9.6 cm/sec and was unaffected by intra-aortic balloon pumping. After angioplasty, the improved coronary luminal diameter narrowing (n = 12; mean narrowing, 18 +/- 12%) was associated with increased distal diastolic flow velocity integral and peak diastolic and mean velocities (13.3 +/- 8.4 units: 36.4 +/- 18.3 and 24.0 +/- 11.4 cm/sec, respectively; all p < 0.01 versus before angioplasty), which were further augmented (36 +/- 37%, 54 +/- 49%, and 26 +/- 17%, respectively; all p < 0.01) with intra-aortic balloon pumping. Intra-aortic balloon pumping did not significantly increase the distal systolic velocity integral (10 +/- 59%) or peak systolic velocity (3 +/- 33%). Similar degrees of balloon pump augmentation of distal coronary flow velocity values were observed in five angiographically normal reference arteries in four patients.

CONCLUSIONS

These data demonstrate lack of significant flow improvement beyond most critical stenoses with intra-aortic balloon pumping and the unequivocal restoration and intra-aortic balloon pump-mediated augmentation of both proximal and distal coronary blood flow velocities after amelioration of severe coronary obstructions in patients after successful coronary angioplasty.

Enhanced coronary blood flow velocity during intraaortic balloon counterpulsation in critically ill patients

OBJECTIVES

The aim of this study was to assess coronary blood flow during intraaortic balloon counterpulsation by direct measurement.

BACKGROUND

In a majority of human studies, increased coronary blood flow during intraaortic balloon counterpulsation measured by indirect techniques has not been consistently demonstrated.

METHODS

Hemodynamic variables and coronary blood flow velocity (20-MHz Doppler-tipped catheter) data were measured in 19 patients requiring intraaortic balloon pumping for clinical indications (11 patients had acute myocardial infarction [9 with shock], 6 had unstable angina, 1 had acute mitral regurgitation and 1 was at high risk undergoing angioplasty). Hemodynamic data, mean and phasic diastolic flow velocity and velocity-time integrals (computed from digitized waveforms) were analyzed during periods of 1:1 balloon counterpulsation.

RESULTS

Intraaortic balloon pumping decreased systolic pressure (6 +/- 10%, p < 0.001) and increased diastolic pressure (80 +/- 30% from baseline, p < 0.001) without changing RR interval. Peak phasic, mean coronary flow velocity and diastolic flow velocity integral were significantly increased (115 +/- 115%, 67 +/- 61%, 103 +/- 81%, respectively, all p < 0.001) during intraaortic balloon pumping. In addition, although a wide splay of data was evident due to operator set variations in balloon inflation and deflation timing, the greater increases in diastolic flow velocity integral (DFVi) occurred in patients with basal systolic pressure < or = 90 mm Hg (% delta DFVi = 102 - 0.1.[unaugmented systolic pressure], SEE = 21.7 mm Hg, r = 0.30, p < 0.001).

CONCLUSIONS

Intraaortic balloon pumping unequivocally and significantly augments proximal coronary blood flow velocity, nearly doubling the coronary flow velocity integral in most patients. This mechanism may be a significant means of ischemia relief in hypotensive patients.

Observations of coronary flow augmentation and balloon function during intraaortic balloon counterpulsation using transesophageal echocardiography

The intraaortic balloon pump has been shown to decrease myocardial oxygen demand by afterload reduction, while increasing myocardial oxygen supply by diastolic augmentation of coronary blood flow. This diastolic augmentation of coronary flow has been demonstrated experimentally with invasive methods. Noninvasively, transesophageal echocardiography has demonstrated efficacy in enabling visualization of the proximal left coronary artery and in recording coronary blood flow velocity. To assess the potential of this technique in demonstrating quantitatively the increase in coronary flow during counterpulsation, 6 patients were studied during intermittent balloon pumping. Peak diastolic coronary blood flow velocity increased by a mean of 117% (range 62 to 287) during balloon inflation (p = 0.002). Furthermore, coronary flow velocity integral increased by a mean of 87% (range 43 to 176; p = 0.003). Problems associated with intraaortic balloon pumping were discovered by transesophageal echocardiography in 4 patients (incorrect balloon placement, damage to the aortic wall [2 patients], and premature balloon deflation time). Transesophageal echocardiography can be used in evaluating intraaortic balloon positioning within the aorta and in monitoring coronary artery flow augmentation during counterpulsation. This relatively noninvasive technique adds another dimension to the evaluation of balloon function and may help in optimizing the benefits of counterpulsation.

Usefulness and limitations of transesophageal echocardiography in the assessment of proximal coronary artery stenosis

To assess the usefulness of transesophageal echocardiography in the evaluation of proximal coronary artery stenosis, 111 consecutive patients (mean age 61 years) who had intraoperative transesophageal echocardiography and coronary angiography within 1 week of surgery were studied. Transesophageal echocardiography visualized the entire length of the left main artery (0.2 to 2.2 cm, mean 0.93), 0.2 to 2.2 cm of the proximal left anterior descending artery and 0.1 to 3.4 cm of the proximal left circumflex artery in 103 patients (93%) and 0.1 to 4.6 cm of the proximal right coronary artery in 55 patients (49%). In the coronary artery segments visualized by echocardiography and compared with the corresponding angiographic segments, transesophageal echocardiography correctly identified 23 (96%) of 24 left main stenoses, 11 (78%) of 14 stenoses involving the left anterior descending artery, 6 (75%) of 8 left circumflex stenoses and all 7 stenoses (100%) of the right coronary artery. In all seven patients with ostial stenosis (left main artery in five and right coronary artery in two), the condition was correctly diagnosed by this technique. The sensitivity and specificity of transesophageal echocardiography in the overall evaluation of proximal coronary artery stenosis as customarily defined by angiography were 96% and 99% for the left main artery, 48% and 99% for the left anterior descending artery, 67% and 100% for the left circumflex artery and 37% and 100% for the right coronary artery, respectively. The distance of the stenotic lesion from the origin of the vessel by transesophageal echocardiography also correlated well with that measured by angiography (r = 0.63 to 0.99).(ABSTRACT TRUNCATED AT 250 WORDS)