Noninvasive assessment of left internal mammary artery graft patency using duplex Doppler echocardiography from supraclavicular fossa

Different flow patterns between left and right internal thoracic artery grafts influence the evaluation of severe graft stenosis by transthoracic Doppler echocardiography

OBJECTIVE

An increase in the diastolic to systolic flow velocity ratio (D/S) in the proximal left internal thoracic artery (ITA) after coronary artery bypass grafting (CABG) enables noninvasive assessment of graft patency by transthoracic Doppler echocardiography (TTDE). The increase in the D/S can be less pronounced at a site distant from the anastomosis. We postulated that proximal ITA flow patterns differ between the left and right ITAs and that the increase in D/S is less pronounced in the right than in the left proximal ITA.

METHODS

Proximal ITA flow was examined by TTDE in 129 consecutive patients after CABG of the left (75) or right (69) ITA to the left coronary artery. The mean D/S of the ITAs was compared with coronary angiography.

RESULTS

The D/S was lower in the group with a patent right ITA than in the group with a patent left ITA (P < .05). The D/S of both the left and right ITAs negatively correlated with angiographic stenosis (r = 0.56 or 0.67, P < .001, respectively). The regression line was significantly shifted downward in the right ITA compared with the left ITA, according to analysis of covariance (P = .01). Graft stenosis was predicted by a D/S of <0.57 and <0.28 with an accuracy of 91% and 97% in the left and right ITAs, respectively.

CONCLUSION

The patency of both left and right ITA grafts to the left coronary artery can be assessed using TTDE, but different cutoff values of D/S are required to diagnose severe ITA stenosis.

Evaluation of early and late postoperative flow capacity of internal thoracic artery bypass by means of stress Doppler echocardiography

OBJECTIVES

Arterial revascularization with the internal thoracic artery (ITA) has shown exceptional long-term results, even though early hypoperfusion can occur and can cause ischemia and contractile dysfunction. Therefore, it is still controversial as to whether the bypass vessel can guarantee the required demand for blood flow during the early postoperative (EPO) phase or whether this is only possible a long time after the operation. This question is important particular in the early postoperative phase to manage afterload and reduce left ventricular oxygen demand. Therefore, stress Doppler echocardiography was performed to assess EPO and late postoperative (LPO) flow capacity after minimal-invasive coronary artery bypass grafting (MIDCAB) in subjects with single vessel disease.

METHODS

Doppler echocardiography was performed after MIDCAB in 15 patients (mean age 65 years+/-12 standard deviation) in the EPO (15 days) and LPO (266 days) at rest and under stress.

RESULTS

The mean diastolic velocity (MDV) as a measure for the coronary perfusion in the bypass-graft was comparable (30.9+/-14.5 EPO to 30.8+/-13.9 cm/s LPO, P>0.05) for both settings (early vs. late). In both tests, the stress reactions by means of handgrip maneuver lead to comparable increases in blood flow: MDV 65.0+/-54.4% (EPO) to 62.5+/-53.7% n.s. (LPO). The flow increase in the bypass graft was just as similar [48.2+/-46.2% (EPO) to 51.1+/-41.6% n.s. (LPO)].

CONCLUSION

The stress echocardiography revealed for the first time that the ITA-graft after MIDCAB-operation is able to produce the same flow reserve through the EPO phase as well as the LPO phase. Restrictions to a maximum early flow adaptation are not justified. Thus, particularly a patient with severe comorbidities or higher age should be mobilized in the EPO phase to minimize the postoperative complications without risk of myocardial ischemia caused by impaired early blood flow through recent implanted ITA. This method for assessment of ITA blood flow allows for long-time observations and can detect disturbances in perfusion at an early stage.

[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.

Assessment of internal thoracic artery patency with transesophageal echocardiography during coronary artery bypass graft surgery

OBJECTIVE

The purpose of this study was to evaluate intraoperative transesophageal echocardiography (TEE) for assessing patency of internal thoracic artery grafts.

DESIGN

A retrospective study.

SETTING

A university hospital.

PARTICIPANTS

Fifty-one consecutive patients who underwent coronary artery bypass graft (CABG) surgery using the left internal thoracic artery (LITA)-to-left coronary artery were examined postoperatively with coronary angiography (CAG).

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

The authors measured blood flow velocity using TEE after anastomosis of a LITA graft. Intraoperative TEE findings and routine CAG results were compared to evaluate the quality of TEE assessment. The LITA was detected in 45 of 51 patients (88%) intraoperatively with TEE. Peak and mean velocities and velocity time integral ratios were determined by dividing each diastolic value by its corresponding systolic value. The peak velocity ratio was 0.51 +/- 0.04 (range, 0.40-0.59) in the presence of stenosis and 1.14 +/- 0.10 (range, 0.58-3.87) in its absence (p = 0.0289), whereas mean velocity ratios were 0.62 +/- 0.05 (range, 0.45-0.72) and 1.27 +/- 0.10 (range, 0.66-4.08) (p = 0.0223), respectively, and velocity time integral ratios were 0.83 +/- 0.09 (range, 0.64-1.05) and 2.69 +/- 0.29 (range, 0.91-8.35) (p = 0.0224), respectively. The critical values for peak and mean velocities and velocity time integral ratios were 0.60, 0.73, and 1.06, respectively, whereas the sensitivity for each was 100% and the specificity was 92%, 94%, and 89%, respectively.

CONCLUSIONS

The authors concluded that the intraoperative assessment of LITA patency with TEE was a markedly useful and powerful tool for anesthesiologists during CABG surgery.

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.

Assessment of minimally invasive direct coronary artery bypass grafting of the left internal thoracic artery by means of magnetic resonance imaging

OBJECTIVES

We sought to evaluate graft patency, flow, and flow reserve in patients with minimally invasive direct coronary artery bypass surgery of internal thoracic artery grafts by a combined magnetic resonance protocol with a phase-contrast technique and magnetic resonance angiography.

METHODS

At 1.5 T (Magnetom Sonata, Siemens), 30 symptomatic patients with 30 left internal thoracic artery grafts were examined 6 years after minimally invasive surgical intervention. Navigator-gated magnetic resonance angiography and contrast-enhanced FLASH-3D magnetic resonance angiography (0.2 mmol gadopentate-diethylene triamine pentetic acid [Gd-DTPA]/kg body weight) was used to assess bypass patency. Phase-contrast flow measurements with retrospective gating were performed in the internal thoracic artery grafts at rest and after stress induction with dipyridamole (0.57 mg/kg body weight). Graft patency was evaluated by means of multidetector computed tomography (Sensation 16, Siemens).

RESULTS

Internal thoracic artery grafts were occluded in 5 of 30 patients. In 6 patients the anastomosis to the left anterior descending artery was highly stenotic (>70 % ) at multidetector computed tomography. In patients with regular grafts (multidetector computed tomography), a significant improvement of graft flow ( P < .001) and diastolic/systolic peak velocity ratio ( P < .001) after stress induction was detected. Magnetic resonance angiography combined with flow reserve measurements could differentiate between occluded-stenotic and regular minimally invasive direct coronary artery bypass grafts.

CONCLUSIONS

Magnetic resonance imaging allows a combined assessment of bypass patency and flow with flow reserve in patients after the minimally invasive direct coronary artery bypass operation. The protocol of this study might be applicable for the evaluation of graft status in symptomatic patients after revascularization.

Off-pump total arterial revascularization: our experience

BACKGROUND AND AIM

Off-pump coronary artery bypass grafting with both the internal thoracic arteries, such as the Tector technique, can reduce the morbidity associated with extracorporeal circulation and aortic cross-clamp. The aim of the present study is to describe our experience and the results obtained.

METHODS

From April 1998 to December 2003, the off-pump Tector technique was performed on 743 patients, of whom 621 were male (83.5%), with a mean age of 65.3 +/- 9.5 years (23-90). Preoperative risk factors were diabetes mellitus in 29.5% and peripheral vasculopathy in 14.7% of the patients. Angiography showed left main disease in 25.6% and triple-vessel disease in 50.3% of the patients, with a mean ejection fraction of 60%+/- 13% (23-88). Both the internal thoracic arteries were harvested using the skeletonization technique and were anastomosed as "Y" or "T" grafts. Intraoperative graft patency was checked using a Doppler flowmeter.

RESULTS

A total of 2028 distal anastomoses were performed, the average being 2.7 (1 to 5) per patient. At least three distal anastomoses were undertaken in 62% of the patients. Postoperative complications included atrial fibrillation in 40 patients (5.4%), myocardial infarction in 24 (3.2%), mediastinitis and reoperation for bleeding in 7 (0.9%) and stroke in 3 (0.4%). Twenty-four patients (3.2%) died in the first month postoperatively.

CONCLUSIONS

The off-pump Tector technique appears to be safe, showing a low surgical morbidity.

Evaluation of flow in the left anterior descending coronary artery but not in the left internal mammary artery graft predicts significant stenosis of the arterial conduit

OBJECTIVES

The purpose of this study was to evaluate which Doppler-derived flow index best predicts new distal left anterior descending coronary artery (LAD) stenosis in patients with left internal mammary artery (LIMA) graft.

BACKGROUND

The LIMA flow measurement has been proposed to assess graft function, but it may be misleading in case of new distal LAD stenosis and/or competitive flow from native LAD. Distal LAD coronary flow reserve (CFR: hyperemic/baseline peak flow velocity ratio) may be more appropriate.

METHODS

The LIMA and distal LAD flow was measured by transthoracic Doppler echocardiography in 96 patients undergoing diagnostic/therapeutic coronary angiography, 7 +/- 4 years after cardiac bypass surgery. The LIMA flow indexes (systolic-to-diastolic peak velocity ratio [SDPVr] >1, diastolic time velocity integral fraction [DTVIf] <0.5, and CFR <2) and LAD CFR <2 were used to predict > or =70% new LAD stenosis.

RESULTS

The LAD CFR <2 predicted new LAD stenosis, found in 21 of 77 patients without competitive flow from native LAD, with significantly higher diagnostic accuracy (98%) than LIMA flow indexes (SDPVr >1 = 61%, DTVIf <0.5 = 69%, and CFR <2 = 72%). The LIMA flow indexes were abnormal in 17 of 19 patients with competitive graft flow, but only 5 had graft restriction, and none had significant LAD stenosis. In a multivariate model of new distal LAD stenosis prediction, competitive flow from native LAD reduced the predictive role of LIMA but not of LAD CFR.

CONCLUSIONS

In patients without competitive flow from native LAD, LAD CFR is more accurate for the detection of LAD stenosis than LIMA CFR. In patients with competitive graft flow, abnormal LIMA flow patterns and blunted LIMA CFR do not reflect downstream LAD flow as LAD CFR does.

Impact of ostial stenosis on the Doppler flow profiles in internal thoracic artery graft

As ostial stenoses of internal thoracic artery (ITA) grafts rarely occur after coronary artery bypass grafting, little is known about their Doppler flow profile. This report describes changes in the Doppler flow of ITA grafts with ostial stenosis after surgical repair of the stenosis. A 54-year-old male underwent coronary artery bypass grafting (CABG) in which the left ITA was anastomosed to the left anterior descending coronary artery. The follow-up coronary angiography revealed an ostial 90% stenosis of the ITA. The patient underwent elective surgery during which the radial artery was interposed between the left subclavian artery and the ITA. Intraoperative ultrasonography was performed immediately before cut down of the ITA graft and again immediately after completion of all anastomoses. Both diastolic and systolic velocities and the velocity time integral increased more than 2-fold after the repair. Neither the diastolic-to-systolic peak velocity ratio nor the diastolic velocity time integral fraction showed remarkable change. These profiles were different from those reported previously for distal stenosis.

Transthoracic Doppler validation in mammary artery grafts after minimal invasive direct coronary artery bypass operation

OBJECTIVE

This study was performed to validate noninvasive transthoracic Doppler ultrasound (TTD) with simultaneous invasive Doppler guidewire measurements in patients after minimal invasive direct coronary artery bypass operation.

METHODS

A total of 14 patients were examined 3 to 8 days after minimal invasive direct coronary artery bypass operation. TTD was performed to measure systolic and diastolic peak velocities of the left internal mammary artery (LIMA) at rest and during adenosine-induced hyperemia. Simultaneous Doppler guidewire measurements were performed.

RESULTS

LIMA flow was detected in 12 of 14 patients (86%). There was high agreement between TTD and Doppler guidewire measurements of LIMA flow velocities (systolic peak velocity: r = 0.86, y = 11.3 + 0.82x +/- 7.9; diastolic peak velocity: r = 0.95, y = 5.7 + 1.02x +/- 7.5; average peak velocity: r = 0.95, y = 5.2 + 0.94x +/- 5.4; and flow velocity reserve: r = 0.97, y = 5.2 + 0.99x +/- 4.5).

CONCLUSION

TTD represents an accurate method to evaluate flow velocities and flow velocity reserve of LIMA bypass grafts even in the early phase after minimal invasive direct coronary artery bypass operation.

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

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

Echocardiographic evaluation of internal mammary artery graft patency

The feasibility of using transthoracic echocardiography to assess internal mammary artery graft patency and function was examined. Coronary angiography and transthoracic echocardiography was performed in 60 consecutive patients undergoing coronary artery bypass from April 2000 to March 2002. Flow velocity, velocity-time integral, and the ratio of the diastolic fraction of the velocity-time integral to total velocity-time integral were measured by doppler transthoracic echocardiography. A stress test was carried out to detect coronary flow changes by echocardiography. The relationship between the coronary angiogram and the echocardiogram was analyzed. The overall graft patency rate was 98%. The mean diastolic velocity-time integral in patients with patent grafts was 0.64, and it increased up to 0.72 in response to physical stress. The occluded grafts showed diastolic velocity-time integral fractions of less than 0.60 in all grafts. There was a statistical correlation between patency > or = FitzGibbon grade B and diastolic velocity-time integral > 0.60. The diastolic velocity-time integral recorded by transthoracic echocardiography predicted the patency of internal mammary artery grafts. As echocardiography is noninvasive and accurate, it might be a useful method of verifying arterial graft patency.

Usefulness of High-Frequency Transthoracic Doppler Echocardiography in Noninvasive Diagnosis of the Left Internal Thoracic Artery Graft Stenosis at the Anastomosis

BACKGROUND

Stenosis of the left internal thoracic artery (LITA) graft, which usually occurs at the site of the anastomosis, can be noninvasively evaluated by the flow pattern in the proximal graft, but the flow pattern is influenced by several other factors.

METHODS AND RESULTS

In the present study, LITA graft flow was investigated by high-frequency transthoracic Doppler echocardiography in 75 consecutive patients who underwent postoperative angiography of the LITA graft. The flow velocity was measured at both the anastomosis and proximal to it, and compared with the quantitative angiographic results. Flow at both sites was detected in 61 (81%) of the 75 patients. The diastolic velocity ratio of the anastomosis to the proximal site correlated with the percent diameter stenosis at the anastomosis. A diastolic velocity ratio >2.0 had a high sensitivity, specificity, positive predictive value and negative predictive value for the presence of significant stenosis at the anastomosis of a LITA graft.

CONCLUSIONS

High-frequency transthoracic Doppler echocardiography can be used for the noninvasive diagnosis of LITA graft stenosis.

Noninvasive evaluation of internal thoracic artery and left anterior descending coronary artery anastomotic sites using transthoracic Doppler echocardiography: comparison with coronary arteriography

OBJECTIVES

This study was designed to evaluate anastomotic sites located between the internal thoracic artery and left anterior descending coronary artery using transthoracic Doppler echocardiography, and then to clarify the accuracy of those results by comparison with coronary arteriographic findings.

METHODS

We examined 35 consecutive patients who had undergone bypass surgery. The echocardiographic examinations were performed within approximately 1 week of follow-up coronary arteriography, which occurred at 4.3 +/- 2.2 months after bypass surgery. We measured the diameter using intraluminal flow signals, and we also measured flow velocity.

RESULTS

Adequate spectral Doppler recordings of coronary flow in the anastomosis were obtained in 31 (89%) of the 35 study patients. In the normal anastomosis group (n = 25), the diameter and the peak blood flow velocity of the internal thoracic artery and left anterior descending coronary artery were 1.5 +/- 0.3 mm and 2.0 +/- 0.4 mm, and 58 +/- 25 cm/s and 47 +/- 20 cm/s, respectively. Stringed internal thoracic artery was found in 4 patients; the echocardiographic findings revealed a greater amount of information regarding the physiologic state in the area of anastomosis compared with angiographic findings. In a stenotic anastomosis found in 2 patients, the blood flow velocity findings at the anastomotic sites (83 +/- 228 cm/s) were higher than those in normal anastomotic patients (59 +/- 28 cm/s).

CONCLUSIONS

Transthoracic Doppler echocardiography enabled an effective evaluation of anastomotic sites between the internal thoracic artery and left anterior descending coronary artery in over 80% of our patients. This totally noninvasive method is thought to be reliable and able to provide a greater amount of information, compared with coronary arteriography, regarding the physiologic state of an anastomosis, such as a competitive relationship.

Noninvasive assessment of flow velocity and flow velocity reserve in the right gastroepiploic artery graft by transcutaneous Doppler echocardiography: comparison with an invasive technique

BACKGROUND

The measurement of flow velocity (FV) in coronary artery bypass grafts using a Doppler guidewire has provided useful clinical and physiologic information. The recently developed transcutaneous Doppler echocardiography is a noninvasive technique to measure FV and FV reserve (FVR) in the right gastroepiploic artery (GEA) graft. The purpose of this study was to evaluate whether transcutaneous Doppler echocardiography accurately measures FV and FVR in the right GEA graft in a clinical setting.

METHODS

In 33 patients who underwent graft angiography for the assessment of the right GEA graft, FV in the right GEA graft was measured by transcutaneous Doppler echocardiography under the guidance of color flow Doppler imaging at the time of examination using a Doppler guidewire. FV in the midportion of the right GEA graft was measured at baseline and during hyperemic conditions using both transcutaneous Doppler echocardiography and a Doppler guidewire.

RESULTS

There were excellent correlations between the value of FV obtained by transcutaneous Doppler echocardiography and those obtained with the Doppler guidewire (averaged peak velocity: y = 0.95 x + 1.46, r = 0.98, standard error of the estimate [SEE] = 2.94 cm/s; averaged systolic peak velocity: y = 0.94 x + 1.18, r = 0.97, SEE = 3.15 cm/s; diastolic peak velocity: y = 0.97 x + 1.62, r = 0.98, SEE = 4.40 cm/s; averaged diastolic peak velocity: y = 0.95 x + 1.75, r = 0.98, SEE = 3.60 cm/s). The FVR as determined by transcutaneous Doppler echocardiography showed a good correlation with that determined using the Doppler guidewire method (y = 0.90 x + 0.21, r = 0.92, SEE = 0.31).

CONCLUSIONS

Transcutaneous Doppler echocardiography proved to be an accurate noninvasive method to measure FV and FVR in the right GEA graft.

Comparison of the postoperative blood flow waveforms of the bypassing grafts in patients following minimally invasive direct coronary artery bypass

PURPOSE

To use Doppler ultrasound velocimetry to detect and compare the postoperative flow characteristics of the bypassing grafts in patients following minimally invasive direct coronary artery bypass surgery (MIDCAB).

MATERIALS AND METHODS

From January 1997 to June 1999, 34 patients underwent MIDCAB with the left internal thoracic artery (LITA) to the left anterior descending coronary artery (LAD) [n = 23], with the right gastroepiploic artery (RGEA) to the right posterior descending artery (RPD) [n = 3], or with the LITA with a saphenous vein graft extension to the LAD (n = 6), the diagonal coronary artery (n = 1), or the right acute coronary artery (n = 1). There were two patients with LITA to the LAD and RGEA to the RPD. Patients underwent MIDCAB due to coronary artery stenosis (100% occlusion, n = 10; 90 to 99% stenosis, n = 18; < 90% stenosis, n = 5) or unsuccessful percutaneous transcoronary angioplasty with dissection (n = 1). All patients underwent flow velocity measurement by Doppler ultrasound velocimetry in the immediate postoperative period, and at 6-month and 12-month intervals; graft flows were quantified based on Doppler velocimetric data.

RESULTS

The results showed that in a patient with a totally occluded LAD or RPD, typical biphasic velocity waveforms were consistently observed. However, a delayed diastolic wave was noted in RGEA grafts. In patients with less-occluded stenotic lesions or with strong back flows, the flow velocity patterns showed biphasic waveforms but systolic reversal was observed in the area closest to the anastomotic site.

CONCLUSION

The presence of an LAD or RPD stenosis proximal to the anastomotic site significantly affects the LITA or RGEA graft flow volume. The biphasic flow pattern proves that an LITA or RGEA graft transports the blood primarily to coronary arteries during the diastolic phase.

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.

Mr flow measurement in the internal mammary artery-to-coronary artery bypass graft: comparison with graft stenosis at radiographic angiography

PURPOSE

To evaluate the sensitivity and specificity of breath-hold magnetic resonance (MR) flow measurement for detection of significant stenosis in internal mammary artery bypass grafts.

MATERIALS AND METHODS

Twenty-six consecutive patients who had undergone coronary artery bypass surgery were examined. Breath-hold velocity-encoded cine MR images were obtained at the midpoint of the internal mammary artery between its origin from the subclavian artery and the distal anastomosis to the left anterior descending artery.

RESULTS

MR images were obtained successfully in 24 patients. At conventional angiography, no significant stenosis was observed in 17 patients (group A), and significant stenosis (diameter > 70%) was observed in seven patients (group B). The mean diastolic-to-systolic peak velocity ratio in group B (0.61 +/- 0.44 [SD]) was significantly lower than that in group A (1.88 +/- 0.96; P <.01). Evaluation of graft stenosis with the diastolic-to-systolic peak velocity ratio revealed a sensitivity of 86% and a specificity of 88%. The mean blood flow rate at baseline in group B (16.9 mL/min +/- 5.5) was significantly lower than that in group A (79.8 mL/min +/- 38.2; P <.01). The sensitivity and specificity of MR blood flow measurement in predicting significant stenosis were 86% and 94%, respectively. The mean pharmacologic flow reserve ratios were 2.00 +/- 1.43 in group A and 1.39 +/- 1.46 in group B (P >.05).

CONCLUSION

Fast MR blood flow measurement at baseline is highly useful for predicting significant stenosis in internal mammary arterial grafts.

Assessment of Internal Mammary Artery Graft Patency: Angiography or Doppler?

Angiography is the usual means of assessing the patency of grafted internal mammary artery. The feasibility of assessing patency by Doppler echocardiography was studied prospectively in 49 patients undergoing left internal mammary artery-to-left anterior descending coronary artery anastomosis. Postoperative angiographic findings were normal in 45 patients (92%), 2 had > 70% and 2 had < 50% narrowing of either the arterial pedicle or the graft. The left internal mammary artery could be visualized by Doppler echocardiography in 44 patients, 4 of whom had abnormal angiograms; there was an unobstructed flow pattern in 42 patients and an obstructed flow pattern in 2 (completely blocked internal mammary artery in one and > 70% narrowing of the graft in the other). Thallium scanning in patients with suboptimal angiographic results but unobstructed Doppler flow patterns showed no evidence of myocardial ischemia in the left anterior descending artery territory. Echocardiography is a sensitive noninvasive screening modality to diagnose critical narrowing of internal mammary artery grafts. It is suggested that angiography may be reserved for cases in which Doppler echocardiography fails to visualize the internal mammary artery or reveals an abnormal flow pattern.

[Total arterial myocardial revascularization with both mammary arteries without extracorporeal circulation]

INTRODUCTION

Tector has described the off-pump total arterial revascularization technique, using multiple anastomosis with both internal thoracic arteries. To reduce surgical morbid-mortality, we have proposed the use of this technique without extracorporeal circulation.

PATIENTS AND METHODS

From April, 1998 the off-pump <<Tector>> technique was performed in 92 patients, 74 male (80%) and 18 female (20%), with a mean age of 64.9+/-8.1 years (42-78). Preoperative angiography demonstrated triple-vessel disease in 58 (63%) patients, and left main disease was present in 19 (20.5%) patients. Forty patients (43.5%) showed unstable angina, 24 patients (26%) significant peripheral vascular disease, and 26 (28%) diabetes mellitus. Both internal thoracic arteries were harvested using the skeletonization technique and were used like a <<T or T>> graft. The flow in the graft was measured using a flowmeter, and in 24 (26%) patients by angiographic study.

RESULTS

A total of 274 distal anastomoses were performed, 122 (44.6%) in the lateral or inferior wall, and 69 (25.2%) were sequential, with an average of 2.98 bypass/patient. In 59.8% of the patients a triple bypass was performed, 22% double bypass, 17% cuadruple bypass and 1 patient a quintuple bypass. During the initial six hours 64.9% of patients were extubated. Only one patient (1.1%) needed intraaortic ballon pumping and 3 (3.2%) inotropics during the postoperative course. Hospital mortality was 3 (3.2%) patients. Reoperation for bleeding was needed in just one patient (1.1%), and 78.3% of patients were not transfused. Mediastinitis occurred in 3 patients (3.2%). Postoperative stroke was not observed. At 7.7+/-2.8 months of mean follow-up all patients were free of symptoms and the global patency rate of 94%.

CONCLUSIONS

Off-pump Tector technique appears to be safe, offering a complete arterial revascularization and showing a reduction of surgical morbidity.

Morphologic and functional evaluation of coronary artery bypass conduits

There is clear evidence in the literature that conventional spin-echo and gradient-echo magnetic resonance imaging (MRI) is capable of assessing patency of coronary artery vein grafts. With more recently introduced breath-hold two-dimensional (2D) and contrast-enhanced 3D techniques, the predictive accuracy has further improved, with sensitivities and specificities in the 90% range. Limitations arise with regard to assessing obstructive disease and evaluating distal segments of sequential grafts, due to insufficient spatial resolution, low signal-to-noise ratio, and cardiac motion. Imaging of arterial grafts is complicated by the metallic clip artifacts. Adding information on graft flow patterns and flow reserve using velocity-encoded cine MRI may help to reduce some of the problems. Clinically, these functional measurements may become of use in non-invasive monitoring of gradually increasing graft narrowing. However, apart from a few exceptions, most patients undergo evaluation of their grafts because they are considered for a re-intervention by angioplasty or coronary artery bypass graft surgery. In these cases information on the status of the native coronary arteries is required. A broader clinical use of MRI in the evaluation of patients with coronary artery bypass grafts may therefore only be expected with further improvement in MR techniques for coronary angiography. J. Magn. Reson. Imaging 1999;10:734-740.

Assessment of left internal mammary artery graft patency and flow reserve after minimally invasive direct coronary artery bypass

Despite its merits, minimally invasive direct coronary artery bypass surgery (MIDCAB) has been criticized for variable left internal mammary artery (LIMA) graft patency rates, prompting the frequent use of postoperative LIMA angiography. Noninvasive transthoracic Doppler interrogation of LIMA grafts has recently been shown to have utility for assessing patency and flow reserve after conventional bypass surgery, but data after MIDCAB has been limited. The objective of this study was to assess LIMA graft anatomy and physiology in 54 patients after MIDCAB using angiography and noninvasive LIMA Doppler imaging. The right internal mammary artery (RIMA) was studied as a control. LIMA flow reserve in response to adenosine was evaluated in a subgroup of 18 randomly chosen patients with patent grafts. LIMA angiographic patency was 93%. Forty-four patients (81%) had obtainable LIMA Doppler data. Patent grafts had a diastolic dominant flow pattern with a peak diastolic/systolic velocity ratio of 1.3 +/- 0.6 and a percent diastolic time-velocity integral (TVI) of 70 +/- 11%. These data were significantly different than the RIMA control values of 0.2 +/- 0.1 and 30 +/- 10%, respectively (p <0.05). Occluded grafts had absent flow or a systolic dominant pattern. Adenosine-induced increases in LIMA peak diastolic velocity from 48 +/- 20 to 105 +/-28 cm/s (p <0.05 vs baseline) and diastolic TVI from 21 +/- 10 to 37 +/- 19 cm (p <0.05 vs baseline), yielding adenosine/baseline ratios of 2.4 +/- 0.9 and 2.0 +/- 0.7, respectively, which was consistent with normal flow reserve. The diastolic flow velocity reserve response was inversely related to baseline diastolic flow (r = -0.69). In conclusion, MIDCAB can be associated with a high rate of LIMA potency and favorable physiologic Doppler flow patterns. Correlation of these findings to long-term patient outcome after MIDCAB is warranted.

Effect of distal stenosis of internal thoracic artery bypass grafts on longitudinal phasic blood flow velocity characteristics

BACKGROUND

Left internal thoracic artery (LITA) bypass conduits show gradual longitudinal transition in their phasic flow velocity patterns from the proximal to distal segments, but little is known about the influence of distal stenosis, particularly early after surgery, on that characteristic. The purpose of this study was to evaluate the influence of distal stenosis on these flow velocity patterns.

METHODS

We examined 24 LITAs within 1 month (7 to 30 days) after surgery with a Doppler-tipped guide wire at the proximal, mid, and distal segments. Maximum peak velocities (MPV), time averaged peak velocities (APV), and velocity-time integrals (VTI) were measured.

RESULTS

In LITAs without stenosis (n = 14, group A), the APV, MPV, and VTI values at the diastole were significantly greater than those for distal stenosis (minimal lumen diameter >75%, n = 10, group B). The values of the 3 indexes at the systole in each segment did not differ significantly between the 2 groups. Both groups showed gradual increases in the diastolic/systolic ratios of the 3 indexes from the proximal to distal portions, the ratios in group A being significantly larger than that in group B (APV, P <. 001; MPV, P <.01; TVI, P <.01, respectively). For these indexes, sensitivity and specificity for predicting stenosis of LITA was higher in the proximal and mid portion than in the distal.

CONCLUSIONS

Anastomotic stenosis decreases the diastolic flow component but not the systolic one. By using diastolic/systolic ratios of the 3 indexes, it is possible to predict distal stenosis of LITA from the resting phasic flow velocity pattern.

[Evaluation of the patency of left internal mammary artery graft by transcutaneous Doppler flow velocity analysis]

OBJECTIVE

To analyze the features of Doppler flow velocity curve of left internal mammary artery by-pass grafts in relation with their permeability as assessed by selective angiography.

METHODS

Twenty-five consecutive patients with a left mammary artery graft were studied by angiography and transcutaneous Doppler technique. From the Doppler tracings, peak velocity and time-velocity integral of the systolic and diastolic components were determined. Patency of the graft and the characteristics of the distal native coronary artery were evaluated at angiography.

RESULTS

Doppler flow signal was obtained in 23 (92%) of 25 analyzed patients. The graft was angiographically patent in 17 (68%) of 25 patients; in 15 (88%) of them the Doppler flow velocity signal was mainly diastolic and in only 2 (12%) it was predominantly systolic. In 8 (32%) of the 25 patients the graft was angiographically occluded, 6 (75%) of these patients showing a predominantly systolic Doppler signal, while the remaining 2 (25%) patients were those in whom the signal could not be elicited. Sensitivity and specificity of a predominantly diastolic Doppler flow pattern for the presence of graft patency was 88% and 100% respectively, with a predictive positive value of 100% and a negative one of 80%.

CONCLUSIONS

Doppler flow velocity pattern of internal mammary artery by-pass grafts is related with patency of the graft, the presence of a predominantly diastolic curve being highly indicative of a patent graft.

Echocardiography in Minimally Invasive Direct Coronary Artery Bypass

Minimally invasive direct coronary artery bypass (MIDCAB) is a recently developed, less-invasive alternative to standard bypass surgery. MIDCAB is performed through a small incision (2-3 inches) on the beating heart without the use of cardiopulmonary bypass or cardioplegia. It is associated with less trauma and a shorter hospital stay than conventional surgery. Transesophageal echocardiography helps in patient selection by detecting protruding aortic atheromas (PATHs), which are associated with a high risk of stroke during typical cardiopulmonary bypass. MIDCAB may be the technique of choice in patients with PATHs. Intraoperative echocardiography can detect wall motion abnormalities and helps in determining intraoperative myocardial ischemia and the postoperative prognosis. Duplex study of the internal mammary arteries is helpful in evaluating coronary anastomosis patency. Characteristically, a patent coronary anastomosis demonstrates a high diastolic flow fraction, with a ratio between peak diastolic and peak systolic flow velocity of > 1.

Usefulness of flow reserve in the left internal mammary artery to determine graft patency to the left anterior descending coronary artery

Two-dimensional Doppler echocardiography (DE) and intravascular Doppler-tipped guidewire (flowire) have been used to measure flow in aortocoronary conduits at rest and during hyperemia, but they have not been compared. We investigated which flow velocity parameters obtained with these 2 different techniques can predict left internal mammary artery (LIMA) graft patency. Twenty-nine patients with previous coronary artery bypass grafting referred for evaluation of symptoms of coronary artery disease were studied after cardiac catheterization using the flowire and DE. Proximal LIMA graft flow velocity was measured at rest and during hyperemia produced by 140 microg/kg/min of intravenous adenosine infusion over 6 minutes with both methods. Normal LIMA grafts and left anterior descending artery (LAD) distal to the anastomosis were present in 16 patients, whereas 13 had >70% graft or native vessel stenosis. The coronary flow velocity reserve (r = 0.79) and the diastolic-to-systolic velocity ratio during hyperemia (r = 0.73) correlated very well between the 2 techniques. Among the variables obtained with the 2 techniques, the intragraft coronary flow velocity reserve measured by both methods was the only independent predictor of graft/recipient LAD patency. This variable had a sensitivity and specificity of 86% at a cutoff point of 2.07 with the flowire method and 83% at a cutoff point of 1.54 with DE. The areas below the receiver-operating characteristic curves were 0.91 and 0.93, respectively. Coronary flow velocity reserve measurements obtained with DE appears a reliable noninvasive method for assessing LIMA graft and/or LAD distal to the anastomosis patency in patients after bypass surgery and correlate very well with those directly obtained by intravascular Doppler.

[The Doppler color detection of internal mammary artery anastomoses and a functional assessment of their patency]

BACKGROUND

Left internal mammary artery coronary graft patency is usually evaluated invasively by cardiac catheterization. The objective of this study was to assess the ability of a high-frequency transthoracic Doppler echocardiographic system in the evaluation of patency and flow velocities changes in left internal mammary artery.

METHODS

Twenty-two patients (63 +/- 9 years, 17 male) who had previously undergone left internal mammary artery to left anterior descending artery were evaluated by transthoracic echocardiography, with an Acuson Sequoia C256 equipment (Acuson, Mountain view, USA), placing the transducer (5 MHz) in the second-third left intercostal space. Left internal mammary artery flow was considered to be found in the presence of one systolic/diastolic biphasic blood flow. Dipiridamol 0.5 mg/kg was administered in absence of contraindications in order to evaluate the flow reserve.

RESULTS

In 16 patients (73%), a biphasic systolic-diastolic flow was visualized. Peak velocity of systolic and diastolic waves was 38 +/- 13 and 37 +/- 15 cm/s, respectively. Eleven patients received i.v. dipiridamol 0.5 mg/kg. After dipiridamol, systolic and diastolic velocities rose from 32 +/- 8 to 43 +/- 14 cm/s (p = 0.0429) and from 25 +/- 8 to 50 +/- 17 cm/s (p = 0.0002), respectively (an increasing of 33 +/- 22% and 103 +/- 46% over the baseline, respectively).

CONCLUSION

This descriptive study shows that a non-invasive functional evaluation of left internal mammary artery grafts by a transthoracic approach with a high-frequency echocardiographic equipment is possible.

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.

Noninvasive functional assessment of left internal mammary artery grafts by transcutaneous Doppler echocardiography

A noninvasive method to assess left internal mammary artery (LIMA) patency and function would be useful because this vessel is frequently used for revascularization of the left anterior descending coronary artery. The purpose of this study was to assess the feasibility of measuring changes in LIMA velocities by transcutaneous Doppler during dipyridamole-induced vasodilation. Twenty-five patients with a LIMA graft anastomosed to the left anterior descending coronary artery were studied at least 1 month after surgery by the use of a 5 MHz transducer placed in the left supraclavicular fossa. Doppler velocity parameters were measured at baseline and after intravenous administration of dipyridamole. Dipyridamole increased mean velocity by 127% +/- 54% (p < 0.001), systolodiastolic velocity time integral by 89% +/- 31% (p < 0.001), and diastolic-to-systolic peak velocity ratio from 0.7 +/- 0.3 to 1.2 +/- 0.4 (p < 0.001). The dipyridamole-to-baseline mean velocity ratio was 2.3 +/- 0.5. We conclude that it is possible to measure dipyridamole-induced changes in LIMA flow velocities and thus obtain an index of LIMA blood velocity reserve by transcutaneous Doppler echocardiography.

Internal mammary artery: 100% visualization with new ultrasound technology

We report our experience in visualizing the internal mammary artery (IMA) with new enhanced Doppler technology. Twenty-three patients without previous coronary artery bypass grafting formed the study group. Bilateral transthoracic two-dimensional and color flow Doppler IMA images were acquired from multiple intercostal spaces with a prototype ultrasound machine equipped with coherent beam formation technology. In all patients, the IMA was followed from its origin for an average of 15 cm. To our knowledge, a high rate of direct visualization (100%) of the IMA has not been reported previously. Noninvasive ultrasound assessment of the IMA may reduce the need for invasive preoperative testing for patency and length and allow postoperative assessment of coronary artery flow reserve.

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.

Breath-hold MR measurements of blood flow velocity in internal mammary arteries and coronary artery bypass grafts

Breath-hold velocity-encoded cine MR (VENC-MR) imaging is a feasible method for measuring phasic blood flow velocity in small vessels that move during respiration. The purposes of the current study are to compare breathhold VENC-MR measurements of flow velocities in the internal mammary arteries (IMA) with nonbreath-hold measurements and to characterize the systolic and diastolic flow velocity curves in a cardiac cycle in native IMA and IMA grafts. Flow velocity in 30 native IMA and 8 IMA grafts were evaluated with a breath-hold VENC-MR sequence with K-space segmentation and view-sharing reconstruction (TR/TE = 16/9 msec, VENC = 100 cm/s). In 10 native IMA, nonbreath-hold VENC-MR images were acquired as well for comparison. Breath-hold VENC-MR imaging showed significantly higher systolic and diastolic peak velocities in native IMA (43.1 cm/second +/- 15.0 and 10.0 cm/second +/- 4.8), in comparison to those of nonbreath-hold VENC-MR imaging (27.6 cm/second +/- 10.2 and 7.3 cm/second +/- 3.9, P < .05). The diastolic/systolic peak velocity ratio in the IMA grafts (.88 +/- .41) was significantly higher than that in native IMA (.24 +/- .08, P < .01). Interobserver variability in the flow velocity measurement was less than 4%. Breath-hold VENC-MR imaging demonstrated higher peak flow velocity in the IMA than nonbreath-hold VENC-MR imaging. This technique is a rapid and effective method for the noninvasive assessment of blood flow velocity in IMA grafts.

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

OBJECTIVE

To evaluate transcutaneous duplex ultrasound in the assessment of internal thoracic artery to coronary artery grafts.

SETTING

Regional cardiothoracic centre.

METHODS

Prospective duplex ultrasound evaluation of 83 consecutive patients undergoing left internal thoracic artery to coronary artery grafts, together with combined angiographic and duplex ultrasound evaluation of 17 patients with suspected recurrent myocardial ischaemia after internal thoracic artery grafting.

RESULTS

The grafted internal thoracic artery was imaged in 65 (78%) of 83 consecutive postoperative patients, and in 13 (75%) of 17 patients with suspected graft dysfunction. Grafts were recognised by their characteristic position and biphasic blood flow pattern. Resting graft flow was estimated from the time averaged velocity and graft cross sectional area. Median resting flow in patients without ischaemic symptoms was 36 ml/min (interquartile range 24 to 49 ml/min). Of 13 patients with recurrent ischaemia in whom the graft could be imaged, nine patients with estimated flow in the lowest quartile or abnormal flow profiles, or both, had graft disease or anastomotic problems on angiography, while four with satisfactory graft flow on ultrasound examination had normal graft flow on angiography, but had evidence of native disease progression in other vessels. Two of four patients in whom it was not possible to image the graft on ultrasound had satisfactory graft function on angiography.

CONCLUSIONS

For those patients whose internal thoracic artery graft can be imaged, transcutaneous duplex ultrasound is a helpful non-invasive guide to graft function. The main limitations to the technique are an inability to image the graft in about 20% of patients, and possible inaccuracy in estimating graft diameter.