Transcutaneous ultrasound assessment of internal thoracic artery to coronary artery grafts in patients with and without ischaemic symptoms

The impact of ligation of proximal side branches on blood flow and functional status of the internal thoracic artery in coronary anastomosis

BACKGROUND

The effect of proximal side branches on the patency of the internal thoracic artery (ITA) is controversial. We used echocardiography and Doppler to verify the effect of ligation of branches on the flow and coronary flow reserve (CFR) of the grafted ITA in patients after coronary artery bypass grafting (CABG).

METHODS

We prospectively investigated 53 patients with preserved left ventricular ejection fraction (LVEF >50%) who underwent CABG of the ITA. In Group I (25 patients), major branches were ligated during ITA anastomosis to the left anterior descending (LAD) coronary artery, whereas no ligation was performed in Group II (28 patients). Systolic flow (SF), diastolic flow (DF), and total flow (TF = SF + DF) were measured by Doppler echocardiography at the proximal level of the ITA preoperatively, at early postoperative stage, and 6 months after surgery. Dobutamine stress echocardiography (DSE) was performed at 6 months to determine CFR.

RESULTS

The ITA flow was predominantly systolic before surgery and diastolic in the postoperative period. We found no differences between the groups in DF. On DSE, SF (19.5±9 mL/min vs 32.7±19 mL/min; P=.003) and TF (79±21 mL/min vs 101±47 mL/min; P=.037) were higher in Group II. There were no differences in CFR (1.9±0.46 vs 2.11±0.56; P=.143).

CONCLUSION

In patients with preserved LVEF, ligation of major side branches during anastomosis to the LAD does not alter ITA flow or CFR.

Looking a bit superficial to the pleura

Background

The internal thoracic artery (ITA) is a descendant branch of the subclavian artery. The former is located bilaterally in both internal sides of the thorax near the sternum and is accompanied by two internal thoracic veins (ITV). From a practical point of view, the ITA (and the ITV) identification is important because these vessels can be injured when pericardiocentesis with the parasternal approach is used. Other advantage of the ITA recognition is to check the patency of the ITA grafts in coronary artery revascularizated patients with new onset chest pain. The purpose of this article is to introduce a simple ultrasonographic technique for recognition of the aforementioned vessels and to highlight the utility of this finding in clinical practice.

Findings

With linear probe and along paraesternal line, the internal thoracic vessels are recognized on grayscale imaging as an anechoic tubular structure immediately anterior to pleural line. Color Doppler identifies a pulsatile (ITA) and a non-pulsatile (ITV) flow. Spectral Doppler normally shows a high resistance velocity profile in non-grafted ITA and a phasic flow in ITV. A biphasic low resistance velocity profile is normally expected in the grafted and permeable ITA.

Conclusions

The ITA (non-grafted) and ITV are recognized routinely along the parasternal line. The operators should identify these vessels when the parasternal approach pericardiocentesis is required and should also consider obtaining spectral Doppler images to check permeability of grafted ITA in coronary artery bypass graft patients with chest pain.

[Ultrasound measurement of left internal mammary artery grafts. Interest and limits in cardiac rehabilitation]

OBJECTIVE

The aim of the study is to demonstrate the feasibility, interest and limits of ultrasound exploration of left internal mammary artery grafts in cardiac rehabilitation.

METHODS

From January 2000 to December 2008, 1434 patients entered in cardiac rehabilitation underlying coronary artery bypass graft, were studied by transthoracic doppler echocardiography in left internal mammary artery graft, from supraclavicular fossa.

RESULTS

One thousand two hundred and fifty-nine grafts were recorded (87.8 %); the diameter was 2.6 +/- 0.3 mm, the peak systolic velocity 46.3 +/- 17.7 cm/s, the peak diastolic velocity 34.0 +/- 13.4 cm/s, the diastolic/systolic (D/S) peak velocity ratio 0.77 +/- 0.26 and the mean blood flow 64.3 +/- 34.5 ml/min. The D/S peak ratio is lower in the presence of high blood pressure or diabetes, is higher in men, with sequential graft or when left ventricle ejection fraction is low. It tends to increase by sportsmen.

CONCLUSION

Transthoracic echo-doppler assessment of internal mammary artery grafts is easily useful and allows to establish a "functional identity card" of the graft in postoperative period, which will be used like a reference for the follow-up.

Can Late Supraclavicular Echo Doppler Reliably Predict Angiographical String Sign of Lima to Lad Area Grafts?

OBJECTIVE

To investigate whether supraclavicular ultrasonography of left internal mammary artery (LIMA) to left anterior descending (LAD) area grafts can reliably predict (distal) string sign grafts on arteriography.

METHODS

Fifty-five patients (42 M, 61 +/- 7 years) with the LIMA to LAD area grafting were prospectively studied. Control arteriography was performed at 1.4 +/- 0.8 years postoperatively. Angiography demonstrated in 46 patients (group I) functional grafts, in 4 patients (group II) sequential distal string sign grafts and in 5 patients (group III) total string sign grafts. Ultrasonography was performed at 1.8 +/- 0.8 year postoperatively and compared with control angiography. Data were tested by unpaired t- and ANOVA tests. The diagnostic accuracy was assessed by the area under the curve of the Receiver Operator Characteristic. A formula was developed to predict the probability of (distal) string sign phenomena of sequential as well as single LIMA grafts.

RESULTS

Between the groups all duplex parameters showed a highly significant linear relation (p < or = 0.004) and all parameters between group I and III are significantly different with high Area Under Curve values. The model for the probability of (distal) string sign grafts fitted best with diastolic and systolic peak velocities as the most discriminative factors for (distal) string sign grafts.

CONCLUSIONS

Postoperative supraclavicular duplex as a method to assess the patency of LIMA to LAD area grafts allows discriminating functional grafts from (distal) string sign grafts.

Detection of Patency of Internal Mammary Artery Grafts to the Left Anterior Descending Artery by Transthoracic Doppler Echocardiography

BACKGROUND

To determine whether a coronary artery bypass graft (CABG) is patent, we examined the flow of the left internal mammary artery (LIMA) to the left anterior descending artery (LAD) by transthoracic Doppler echocardiography (TTDE).

PATIENTS AND METHODS

Eighty-seven patients with CABG (LIMA to distal LAD) were enrolled in the study. The flows from each subject were analyzed by three criteria: mosaic flow at the anastomosis site, distal anterograde flow (ante flow), and proximal retrograde flow (retro flow).

RESULTS

On angiography, 79 grafts were patent and eight were not. TTDE study of 79 patent grafts demonstrated mosaic, ante, and retro flow in 63 (79.7%), 74 (93.7%), and 35 grafts (49.4%), respectively. The averaged diastolic peak velocity of ante flow was 26.3 +/- 11.0 cm/sec, significantly higher than that (4.8 +/- 7.1 cm/sec, P < or = 0.0001) in eight patients without patent grafts. These eight patients had no mosaic or retro flow and only three had ante flow. The accuracies to predict patency were 81.6%, 90.8%, and 49.4% for mosaic, ante, and retro flows, respectively.

CONCLUSIONS

The existence of mosaic, retro, or sufficient ante flows strongly indicated the patency of LIMA to the LAD. When symptoms are possible to be derived from the occlusion of CABG to LAD, TTDE is a promising method to examine whether a LIMA to LAD bypass is patent.

Differences in LIMA Doppler characteristics for different LAD perfusion areas

OBJECTIVES

To correlate supraclavicular left internal mammary artery (LIMA) to left anterior descending artery (LAD) area Doppler characteristics with angiographically perfused area.

METHODS

Sixty patients (50 male, mean age 62+/-7.3 years) with LIMA to LAD area grafting were prospectively entered in a follow up study. Supraclavicular echo Doppler of the LIMA was studied at the LIMA origin preoperatively, and at 4.8+/-3.8 months and 1.8+/-0.9 years postoperatively. The potential area to be revascularized judged from preoperative angiography was called the 'target' area. Control angiography (native and LIMA) was done at 1.5+/-0.9 years. The perfused area % was classified into group I < or =17.0% (n=16), group II >17.0% and <22.50% (n=17), and group III > or =22.50% (n=18) and related to LIMA Doppler characteristics. Multivariate linear regression analyses (MLRA) were performed to assess the relations between Doppler variables and the perfused area, target area and ratio of perfused/target area.

RESULTS

At MLRA perfused area was significantly related to the natural logarithm of diastolic peak velocity (DPV) (P=0.013) and diastolic mean velocity (P=0.048) and the ratio only to the degree of LAD stenosis (P=0.004). In hyperaemic response maximal DPV (DPV max) showed significant correlation to the perfused area (P=0.005) as well as to the ratio (P=0.017). When analyzing the additive power of both investigations, only DPV max (P=0.005) correlated significantly to the perfused area and for the ratio only the degree of stenosis of the LAD emerged as significant (P=0.004).

CONCLUSIONS

At MLRA the diastolic flow pattern at rest and the maximal DPV in hyperaemic response correlated significantly with the LIMA run-off area whereas the last variable is the strongest predictor of the LIMA run-off area.

Assessment of internal mammary artery and saphenous vein graft patency and flow reserve using transthoracic Doppler echocardiography

OBJECTIVE

To investigate transthoracic Doppler echocardiography in the identification of coronary artery bypass graft (CABG) flow for assessing graft patency.

DESIGN

The initial study group comprised 45 consecutive patients with previous CABG undergoing elective cardiac catheterisation for recurrent ischaemia. The Doppler variables best correlated with angiographic graft patency were then tested prospectively in a further 84 patients (test group).

SETTING

Three tertiary referral centres.

INTERVENTIONS

Flow velocities in grafts were recorded at rest and during hyperaemia induced by dipyridamole (0.56 mg/kg/4 min), under the guidance of transthoracic colour Doppler flow mapping. Findings on transthoracic Doppler were compared with angiography.

MAIN OUTCOME MEASURES

Feasibility of identifying open grafts by Doppler and diagnostic accuracy for Doppler detection of significant (>/= 70%) graft stenosis.

RESULTS

In the test group the identification rate for mammary artery grafts was 100%, for saphenous vein grafts to left anterior descending coronary artery 91%, for vein grafts to right coronary artery 96%, and for vein grafts to circumflex artery 90%. Coronary flow reserve (the ratio between peak diastolic velocity under hyperaemia and at baseline) of < 1.9 (95% confidence interval 1.83 to 2.08) had 100% sensitivity, 98% specificity, 87.5% positive predictive value, and 100% negative predictive value for mammary artery graft stenosis. Coronary flow reserve of < 1.6 (95% CI 1.51 to 1.73) had 91% sensitivity, 87% specificity, 85.4% positive predictive value, and 92.3% negative predictive value for significant vein graft stenosis.

CONCLUSIONS

Transthoracic Doppler can provide non-invasive assessment of CABG patency.

Improved MR flow mapping in coronary artery bypass grafts during adenosine-induced stress

PURPOSE

To validate a recently developed fast high-temporal-resolution magnetic resonance (MR) flow sequence and use it to assess coronary artery bypass graft function during pharmacologic stress.

MATERIALS AND METHODS

Aortic and internal mammary artery flow was measured in 11 healthy volunteers by using conventional cine gradient-echo imaging as a reference standard method and turbo-field echo-planar imaging (TFEPI). By using TFEPI, breath-hold flow mapping with a spatial and temporal resolution of 0.8 mm(2) and 23 msec, respectively, can be performed. This sequence was applied in 20 angiographically normal grafts, and total blood flow at rest and during adenosine infusion (140 microgram/kg/min) was measured.

RESULTS

Good agreement in aortic and internal mammary artery flow values between conventional fast-field echo and TFEPI techniques was found. The mean bypass graft total flow (+/- SD), as assessed with TFEPI, increased from 30.8 mL/min +/- 13.5 to 76.7 mL/min +/- 36.5 (P <.05) to yield a flow reserve of 2.7. Furthermore, this sequence revealed a difference in total flow between single and sequential grafts at rest (25.4 mL/min vs 40.9 mL/min; P <.05) and during stress (65.2 mL/min vs 98.3 mL/min; P <.05).

CONCLUSION

Breath-hold TFEPI provides fast accurate flow measurements with high temporal resolution and allows motion-compensated flow quantification in multiple coronary artery bypass grafts during one 6-minute adenosine infusion.

Transesophageal Echocardiographic Examination of Left Subclavian Artery Branches

This preliminary study demonstrates the feasibility of examining the proximal segments of the branches of the left subclavian artery during probe withdrawal toward the end of a routine transesophageal echocardiographic study. The branches identified most commonly were the vertebral and the internal mammary arteries.

Preoperative and early postoperative assessment of the internal thoracic artery by transcutaneous duplex ultrasound in coronary artery bypass grafting

We examined internal thoracic artery by transcutaneous duplex ultrasound in 26 patients on four occasions: 4 (+/-2) days before the operation, and 61 (+/-8) minutes, 5 days and 53 (+/-3) days postoperatively. There was dominant systolic flow in preoperative scans. After the operation a characteristic biphasic flow with increased peak diastolic velocity and a decrease in peak systolic/peak diastolic velocity ratio was detected in all patients. The pulsed Doppler spectrum was used to measure peak velocity, time averaged mean velocity and time averaged maximum velocity. Resting internal thoracic artery flows calculated using time averaged mean velocity were 30.9+/-5.4 ml/min preoperatively, 40.7+/-6.3 ml/min immediately after surgery, 41.1+/-8.2 ml/min at 5 days and 40.1+/-4.9 ml/min at 53 days. There were no significant changes in resting internal thoracic artery flow between early and late postoperative studies. Flow estimates calculated using 0.5 x time averaged maximum velocity or time averaged mean velocity showed good agreement. Early postoperative measurements appear to be a good predictor of later resting graft flow.

Assessment of left internal mammary artery grafts using dipyridamole Doppler echocardiography

Color Doppler echocardiography of the left mammary artery was combined with dipyridamole testing in order to assess the presence of significant (>70%) graft stenosis in 87 patients with a mammary artery graft to the left anterior descending coronary artery presenting with chest pain. Occluded grafts are detected by absent diastolic flow velocities at baseline, whereas the response of the diastolic flow velocity to dipyridamole distinguishes patients with critical versus noncritical stenosis of a patent graft.