Transthoracic high-frequency echocardiographic detection of atherosclerotic lesions in the descending portion of the left coronary artery

Relationship between the number of coronary risk factors and coronary atherosclerosis assessed by high-frequency transthoracic echocardiography

Atherosclerosis is a diffuse process and can be evaluated in the distal part of the left anterior descending coronary artery (LAD). We evaluated whether 2-dimensional high-frequency transthoracic echocardiography could detect changes in coronary wall thickness and size associated with coronary risk factors. In all, 312 patients without a history of coronary artery disease and 40 patients with LAD disease proven by coronary angiography underwent transthoracic echocardiography evaluation of the distal LAD using high-frequency transducer. LAD wall thickness, luminal diameter, external diameter, and coronary flow velocity were measured, and these values were compared according to the number of coronary risk factors (hypertension, hypercholesterolemia, diabetes, smoking, and family history). The feasibility of measuring coronary thickness and coronary flow velocity was 86% and 90%, respectively. LAD wall thickness and external diameter significantly increased according to the increase in the number of risk factors. Patients with 3 or more coronary risk factors showed similar LAD wall thickness (0.82 +/- 0.2 vs 0.89 +/- 0.2 mm) and external diameter (3.4 +/- 0.8 vs 3.3 +/- 0.9 mm) compared with those obtained in patients with LAD disease. High-frequency transthoracic echocardiography is feasible to measure coronary artery wall thickness and external diameter in the distal LAD. This approach has a potential for noninvasive evaluation of the arterial remodeling and the changes in these variables after risk factor modification and intensive drug therapy.

Comparison of high-frequency two-dimensional transthoracic echocardiography versus intravascular ultrasound for evaluation of the left anterior descending coronary artery

The purpose of this study was to evaluate the feasibility of high-frequency transthoracic echocardiography for measuring the wall thickness and luminal area of the left anterior descending coronary artery (LAD). Fifteen patients underwent simultaneous high-frequency transthoracic echocardiography and intravascular ultrasound (IVUS) examinations. There were good agreements for wall thickness (0.38 +/- 0.05 vs 0.38 +/- 0.06 mm, p = 0.0004) and luminal area (3.24 +/- 1.05 vs 3.32 +/- 1.34 mm2, p <0.0001) between high-frequency transthoracic echocardiography and IVUS measurements. High-frequency transthoracic echocardiography was reliable in the measurement of the wall thickness and luminal area of the LAD.

Pattern of exercise-induced ST change is related to coronary flow reserve in patients with chest pain and normal coronary angiogram

OBJECTIVE

To evaluate the usefulness of exercise treadmill test in determining the true microvasculature-induced ischemia, we compared the pattern of ST depression with coronary flow reserve (CFR) using transthoracic Doppler echocardiography (TTE) in patients with chest pain and normal coronary angiogram.

DESIGN

Fifty-nine subjects (M/F=21:38, mean age 55+/-9 years) with chest pain and normal coronary angiogram underwent maximal symptom-limited exercise treadmill test (ETT). CFR was estimated with TTE and dipyridamole. Patients with a history of acute myocardial infarction, regional wall motion abnormalities, hypertrophic cardiomyopathy, ejection fraction less than 50%, or primary valvular heart disease were excluded from this study.

RESULTS

No ST change was observed in 20 of 59 (34%) patients, up slope depression was observed in 20 (34%), flat depression in 13 (22%), and down slope depression in 6 (10%). Eleven of thirty nine (28%) exercise positive patients had decreased CFR <2.1. CFR was 3.1+/-0.6 in group with no ST change, 3.1+/-0.6 in group with up slope depression, 2.1+/-0.6 in group with flat depression (p<0.05 versus group with no change and group with upslope depression, respectively), and 2.0+/-0.4 in group with down slope depression (p<0.05 versus group with no change and group with up slope depression, respectively). Flat to down slope depression of ST change during ETT had sensitivity of 58% and specificity of 95% for predicting CFR <2.1.

CONCLUSION

Flat and down slope depression of ST segment during ETT might increase the sensitivity and specificity to detect the true microvasculature-induced ischemia that is defined as CFR less than 2.1 in patients with chest pain and normal coronary angiogram.

Coronary artery diameter can be assessed reliably with transthoracic echocardiography

We studied whether diameters of coronary arteries can be measured accurately with the use of transthoracic echocardiography (TTE). By knowing the anatomic diameter of the coronary artery together with coronary flow velocity it is possible to measure coronary flow volume more precisely by TTE. However, the suitability of TTE for measurement of diameters of all main epicardial coronary arteries has not been systematically validated. We measured the diameters of the left main (LM), left anterior descending (LAD), left circumflex (LCX), and right coronary arteries (RCA) with the use of TTE [manual two-dimensional (2D), color-Doppler, and automated 2D analysis] in 30 patients who had normal coronary anatomy. We compared these diameters to those measured with quantitative coronary angiography (QCA). We could measure diameters of LM, LAD, LCX, and RCA by TTE in up to 37%, 63%, 7%, and 60% of patients, respectively. The overall correlation coefficients between TTE and QCA measurements were 0.83 ( P < 0.01) with manual 2D analysis, 0.82 ( P < 0.01) with automated 2D analysis, and 0.94 ( P < 0.01) with a color-Doppler-based analysis. Interobserver variability of TTE measurements was low (coefficient of variation 5.4 ± 4.6–7.5 ± 8.8%). TTE is an accurate method to evaluate coronary artery diameter in patients with healthy coronary arteries.

Detection of subclinical coronary atherosclerosis using two-dimensional, high-resolution transthoracic echocardiography

OBJECTIVES

We evaluated whether two-dimensional high-resolution transthoracic echocardiography (HR-2DTTE) can detect changes in arterial wall thickness and size associated with subclinical coronary artery disease (CAD).

BACKGROUND

Arterial wall thickening, compensatory arterial enlargement and a preserved arterial lumen characterize subclinical atherosclerosis. Detection of these changes during the asymptomatic stage of CAD may allow early treatment and prevention of acute coronary events.

METHODS

Twenty-six patients with angiographically proven CAD and 29 normal volunteers underwent HR-2DTTE evaluation of the left anterior descending coronary artery (LAD) using an ATL 5000 echograph (Advanced Technology Laboratories, Bothell, Washington) with a 4 to 7 MHz transducer. Significant (>70%) LAD stenosis was present in 15 patients (mean 82%); 11 patients did not have significant LAD stenosis (mean 26%) and represented a surrogate for subclinical LAD disease. Wall thickness, maximal luminal diameter and external diameter of the LAD were measured.

RESULTS

Left anterior descending coronary artery wall thickness was larger in patients (1.9 +/- 0.4 mm) than it was in volunteers (0.9 +/- 0.1 mm, p < 0.001). The external diameter of the LAD was (6.0 +/- 1.1 mm) in patients and (3.9 +/- 0.7 mm) in volunteers (p < 0.001). Luminal diameter was 2.2 +/- 0.5 mm in patients and 2.1 +/- 0.6 mm in volunteers (p = NS). There was no difference in wall thickness (1.9 +/- 0.4 mm vs. 2.0 +/- 0.4 mm), luminal diameter (2.2 +/- 0.5 mm vs. 2.2 +/- 0.4 mm) and external diameter (5.9 +/- 1.0 mm vs. 6.2 +/- 1.2 mm) between the patients with <70% and >70% LAD stenosis.

CONCLUSIONS

Left anterior descending coronary artery wall thickness and external diameter are significantly increased in patients with CAD as compared with normal subjects, and HR-2DTTE is sensitive enough to detect these differences. Wall thickness and external diameter are increased to the same extent in patients with obstructive and subclinical LAD disease.

Potential use of transthoracic echocardiography in the assessment of coronary flow reserve

Coronary flow reserve provides a gold standard assessment of the epicardial and microvascular coronary circulation. However, measurement of coronary flow reserve is limited by the invasiveness or complexity of the methods hitherto available. We investigated whether transthoracic echocardiography could be used to assess coronary flow reserve. We imaged distal left anterior descending coronary artery diameter and flow in 14 healthy volunteers, both at rest and during intravenous infusion of adenosine (140 microg/kg per minute). Volunteers were men, with an average (+/-SD) age of 28.4 +/- 6.3 years. Complete data were acquired in 11 cases. Average distal left anterior descending coronary artery diameter was 0.213 +/- 0.03 cm. Velocity time integral rose from 8.6 +/- 2.1 cm to 27.7 +/- 5.6 cm with adenosine infusion. Heart rate rose from 64.7 +/- 9. 8 to 75.3 +/- 11.7 bpm. The Doppler angle of incidence to flow was 42.4 +/- 8.7 degrees. Resting distal left anterior descending coronary artery flow was therefore calculated as 13.4 +/- 3.2 mL/min and hyperemic flow as 51.2 +/- 16.2 mL/min, yielding a coronary flow reserve of 3.81 +/- 0.6. We conclude that coronary flow reserve can be assessed in a selected population with the use of transthoracic echocardiography and an intravenous infusion of adenosine. The simplicity of this noninvasive technique suggests that it could become a useful tool for measurement of coronary flow reserve if imaging success rates can be optimized.

Visualization of stents in the left anterior descending coronary artery by transthoracic echocardiography in pigs and humans

In this study, we demonstrate that coronary artery stents can be visualized by transthoracic 2-dimensional echocardiography. We were able to image stents in the left anterior descending coronary artery in 6 of 6 pigs and in 6 of 7 patients studied.

Improved Doppler detection of proximal left anterior descending coronary artery stenosis after intravenous injection of a lung-crossing contrast agent: a transesophageal Doppler echocardiographic study

OBJECTIVE

This study was designed to verify the usefulness of transesophageal Doppler recording of blood flow velocity in the proximal left anterior descending coronary artery, after a peripheral injection of a lung-crossing contrast agent (SHU 508A), in detecting and locating a hemodynamically significant stenosis (vessel narrowing > or = 50%) affecting this portion of the vessel.

BACKGROUND

Transesophageal Doppler echocardiography has a limited diagnostic impact on the evaluation of proximal left anterior descending coronary artery stenoses. Peripheral injection of SHU 508A, a lung-crossing contrast agent enhancing Doppler signal to noise ratio in coronary arteries, may allow recording of localized disturbed blood flow velocity at the stenosis site even in the absence of a clear B-mode visualization of the vessel.

METHODS

Transesophageal Doppler echocardiography, before and after echo contrast injection, was performed in 31 patients who underwent coronary angiography. Using color Doppler as a guide, pulsed wave Doppler recording of blood flow velocity in the left anterior descending coronary artery was attempted to detect a localized increase in blood flow velocity. B-mode evaluation of the vessel was also performed.

RESULTS

Angiography showed a significant proximal left anterior descending coronary artery stenosis in 16 patients (group 1) and no stenosis in 15 patients (group 2). In 15 of 16 group 1 patients, Doppler after contrast injection revealed a localized velocity increase of at least 50% of the reference value; mean (+/-SD) percent increase in velocity was 150 +/- 89% (range 367% to 0%). In group 2 Doppler after contrast injection revealed a mild localized increase in velocity in four patients and no increase in velocity in the remaining 11 patients; mean (+/-SD) percent increase in velocity was 5 +/- 7% (range 21% to 0%, p < 0.001 vs. percent increase in group 1). When a percent velocity increase > or = 50% of the reference value was considered a positive criterion for detecting significant stenosis, the sensitivity and specificity were 92% and 100% respectively. The sensitivity of the evaluation before contrast injection or considering B-mode imaging alone was much lower (25% and 19%, respectively, p < 0.001 vs. evaluation after contrast injection). In addition, color Doppler after contrast injection correctly located the stenosis along the vessel, as compared with angiography.

CONCLUSIONS

Blood flow evaluation of the proximal left anterior descending coronary artery by transesophageal Doppler echocardiography after contrast injection is a feasible and reliable method for detecting and locating significant stenoses affecting this part of the vessel and is an improvement over the traditional ultrasound approach.

Echocardiographic and cardiac Doppler assessment of mice

Recent studies have suggested that intermediate-frequency M-Mode transthoracic echocardiographic imaging is a promising method for evaluating the left ventricle in transgenic mice. However, there is a paucity of data regarding two-dimensional (2-D) echocardiography and cardiac Doppler echocardiography in this model. Therefore we studied 15 mice (body weights 38 to 65 gm) with an ultrasound system equipped with a 9 MHz transducer. M-mode, 2-D, pulsed, and color-flow Doppler studies were performed. Mean +/- SD for septal, posterior wall, and left ventricular cavity dimensions at end diastole were the following: M-mode: 1.1 +/- 0.2, 1.0 +/- 0.2, and 3.7 +/- 0.7 mm; 2-D: 1.0 +/- 0.2, 1.1 +/- 0.3, and 3.0 +/- 0.6mm. Left ventricular fractional shortening was assessed from the M-mode echocardiogram: mean 53.7% +/- 10.7% (range 42% to 77%). 2-D assessment of left ventricular mass correlated better with left ventricular mass identified at necropsy than left ventricular mass identified by M-mode echocardiography (r = 0.70; p = 0.007 versus r = 0.07; p not significant). 2-D visualization of left ventricle, proximal aorta, and aortic and mitral valves was excellent and was obtained mainly from a "parasternal" window. Apical views were more difficult to obtain. Mean +/- SD for aortic peak and mean velocities and velocity-time integral were 0.53 +/- 0.13, 0.32 +/- 0.08, and 0.025 +/- 0.008 m/sec. Estimated stroke volume was 0.0506 +/- 0.018 ml/beat. Cardiac output was 12.64 +/- 7.87 ml/min. Mean +/- SD for mitral peak E, peak A, and E/A ratio were 0.45 +/- 0.09 m/sec, 0.19 +/- 0.06 m/sec, and 2.4 +/- 0.66 m/sec, respectively. In all mice the E/A ratio was greater than 1 (range 1.76 to 3.6). Color-flowing imaging clearly displayed normal mitral inflow and left ventricular outflow. In one mouse, aortic regurgitation was recorded by pulsed Doppler echocardiography. Echocardiographic, pulsed, and color-flow Doppler assessment of mice is feasible. In this study left ventricular mass was assessed better by 2-D measurement of left ventricular dimensions. Assessment of left ventricular performance is feasible. Color Doppler-guided evaluation of aortic flow and aortic root measurement permits assessment of stroke volume and cardiac output.

In vivo echocardiographic detection of enhanced left ventricular function in gene-targeted mice with phospholamban deficiency

We evaluated the ability of M-mode and Doppler echocardiography to assess left ventricular (LV) function reliably and repeatedly in mice and tested whether these techniques could detect physiological alterations in phospholamban (PLB)-deficient mice. Anesthetized wild-type mice (n = 7) and mice deficient in PLB (n = 8) were studied with two-dimensional guided M-mode and Doppler echocardiography using a 9-MHz imaging and 5- to 7.5-MHz Doppler transducer. Data were acquired in the baseline state and after intraperitoneal isoproterenol administration (2.0 micrograms/g IP). Interobserver and intraobserver variability and reproducibility were excellent. PLB-deficient mice were associated with significant (P < .05) increases in several physiological parameters (mean +/- SD) compared with wild-type control mice: normalized mean velocity of circumferential shortening (7.7 +/- 2.1 versus 5.5 +/- 1.0 circ/sec), peak aortic velocity (105 +/- 13 versus 75 +/- 9.2 cm/s), mean aortic acceleration (57 +/- 16 versus 31 +/- 4 m/s2), and peak early-diastolic transmitral velocity (80.0 +/- 7.2 versus 66.9 +/- 7.7 cm/s). LV dimensions, shortening fractions, heart rates, late diastolic transmitral (A) velocities, and early to late (E/A) diastolic velocity ratios were similar in both groups. Isoproterenol administration resulted in significant increases in Doppler indices of ventricular function in control but not PLB-deficient mice. These findings indicate that assessment of LV function can be performed noninvasively in mice under varying physiological conditions and that PLB regulates basal LV function in vivo.