Coronary bypass graft patency cannot be determined by multidetector spiral computed tomography

Objectives. Angiography by selective catheterization is the reference standard for coronary bypass graft patency assessment but carries a risk of serious complications. We have investigated whether 16-slice multidetector spiral computed tomography (MDCT) can substitute for selective angiography. Design. Two to three years after coronary artery bypass grafting, 45 patients with a total of 156 bypasses (100 single and 28 sequential grafts) were examined with both MDCT and conventional selective angiography on the same day. The bypasses were classified as patent, stenotic or occluded. Results. The likelihood ratio for MDCT-detected occlusion was 40, reflecting a fairly high combined sensitivity and specificity. However, 24% of the distal anastomoses could not be evaluated by MDCT, mainly because of respiratory movements, artifacts due to metal clips, and small vessel dimensions. Moreover, seven out of 117 bypasses (6%) deemed evaluable by MDCT were wrongly classified by this method. Conclusions. At present, 16-slice MDCT cannot replace selective angiography for assessment of coronary bypass graft patency since 24% of bypasses could not be evaluated by this method, and an error rate of 6% is unacceptable.     

Coronary bypass graft patency cannot be determined by multidetector spiral computed tomography

OBJECTIVES: Angiography by selective catheterization is the reference standard for coronary bypass graft patency assessment but carries a risk of serious complications. We have investigated whether 16-slice multidetector spiral computed tomography (MDCT) can substitute for selective angiography. DESIGN: Two to three years after coronary artery bypass grafting, 45 patients with a total of 156 bypasses (100 single and 28 sequential grafts) were examined with both MDCT and conventional selective angiography on the same day. The bypasses were classified as patent, stenotic or occluded. RESULTS: The likelihood ratio for MDCT-detected occlusion was 40, reflecting a fairly high combined sensitivity and specificity. However, 24% of the distal anastomoses could not be evaluated by MDCT, mainly because of respiratory movements, artifacts due to metal clips, and small vessel dimensions. Moreover, seven out of 117 bypasses (6%) deemed evaluable by MDCT were wrongly classified by this method. CONCLUSIONS: At present, 16-slice MDCT cannot replace selective angiography for assessment of coronary bypass graft patency since 24% of bypasses could not be evaluated by this method, and an error rate of 6% is unacceptable.     

Detection of coronary artery bypass graft patency by contrast enhanced magnetic resonance angiography.

OBJECTIVE: The subject and purpose of the prospective study was to delineate coronary artery bypass graft (CABG) course and to determine patency of aortocoronary venous bypass grafts (ACVB) compared with internal mammary artery bypass grafts (IMA) in the early postoperative follow-up, by contrast enhanced magnetic resonance angiography (MRA). For control, patients were examined with X-ray angiography and spiral-computed tomography (CT). METHODS: Eighty-five patients (74 male/11 female) with a mean age of 63.7 years underwent MRA examination, applying contrast enhanced gradient-echo sequence after an average distance of 7 days from CABG surgery. A 1.5 Tesla magnetom vision (Siemens, Erlangen, Germany) with phased array coil technology was used. Overall, 247 bypass grafts (160 ACVB/87 IMA) were studied with a 3D (three dimensional) ultrashort TE gradient-echo sequence (TR/TE/a:5 ms/2 ms/40 degrees) with 512*512 matrix and 500 mm FoV in single breath-hold technique after Gd-DTPA bolus injection. CABGs were judged in three different parts, including the course of CABG and both anastomoses. CABGs were controlled by angiography and spiral-CT to examine sensitivity, specificity and efficiency of MRA examination. Additional measurement of bypass graft flow velocity of arterial and venous grafts was performed with 2D phase contrast technique in breath-hold technique with ECG triggering. RESULTS: One hundred and thirty-nine of 160 (86.9%) ACVB grafts and 83 of 87 (95.4%) IMA grafts could be visualized. Suspected occlusions of 10 CABGs were confirmed in 80% with a second modality. Five CABGs were false positive in MRA. MRA proved a high specificity (93.8%), sensitivity (89.9%) and efficiency (1.73), especially in detection of IMA to LAD and ACVB to LAD and RCA (Table 1). 3D maximum intensity projection (MIP) reconstruction was helpful in delineating CABG course and in several cases in detecting stenosis of coronary arteries. Results of flow velocity showed a significant higher mean systolic velocity in arterial bypasses than in venous grafts with a higher maximum velocity in systole than in diastole in both grafts. Bypass stenosis in distal anastomosis could not be verified with MRA and flow method. CONCLUSION: Contrast enhanced 3D ultrashort TE gradient-echo magnetic resonance angiography has the potential for being a reliable method for CABG visualization and CABG patency determination in the early postoperative period. MR flow measurement was not qualified for detection of a bypass stenosis.     

Sixteen-slice multidetector computed tomography for graft patency evaluation after coronary artery bypass surgery

OBJECTIVE: To investigate the ability of 16-slice multidetector computed tomography (MDCT) to assess coronary artery bypass graft patency and to detect bypass stenosis by comparison with coronary angiography. METHODS: Thirty patients underwent both conventional coronary bypass angiography and retrospective ECG gated 16-slice multidetector computed tomography after surgery using 0.4 seconds rotation time and 1.25 mm slice thickness. RESULTS: Among a total of 107 bypass grafts, 101 grafts (94.4%) were evaluable by MDCT. Thirteen patients were taking oral beta blockers. Mean heart rate was 73.6 (52-105). Of the 40 internal mammary arteries and two radial arteries examined, only one was occluded by coronary bypass angiography and MDCT, resulting in a sensitivity of 100% and a specificity of 100%. MDCT correctly diagnosed all patent venous grafts and missed two of the 14 venous grafts shown occluded by conventional angiography resulting in a sensitivity of 85.7% and specificity of 100%. When occluded grafts were excluded, MDCT did not detect two out of two anastomotic arterial graft stenosis >50% and resulted in one false positive result for a sensitivity and specificity of 0% and 97.4%, respectively. MDCT correctly diagnosed one out of three venous stenosis >50% and falsely diagnosed one venous graft stenosis >50% yielding a 33.3% and 97.6% sensitivity and specificity, respectively. CONCLUSION: Sixteen-slice MDCT allows for noninvasive evaluation of coronary bypass grafts patency with high diagnostic accuracy. Assessment of distal anastomotic stenosis was deficient, particularly for arterial grafts, still limited by low resolution or artifacts. Improved accuracy may be obtained by more aggressive heart rate reduction.     

Non-invasive assessment of coronary artery bypass graft patency using 16-slice computed tomography angiography

Background  

Invasive coronary angiography is the gold standard means of imaging bypass vessels and carries a small but potentially serious risk of local vascular complications, including myocardial infarction, stroke and death. We evaluated computed tomography as a non-invasive means of assessing graft patency.     

Augmentation of coronary bypass graft flow induced by dipyridamole and its relation to bypass graft patency

To evaluate the effect of dipyridamole on coronary bypass graft flow, 10 mg of dipyridamole was injected intravenously, during the measurement of graft flow, at the time of surgery. Its concentration in serum was measured and compared with that after oral administration. In 50 individual vein grafts performed on 35 patients, graft flow increased from 65 ±37 to 96±55 ml/min (p<0.001) after the dipyridamole injection and the arterial pressure decreased slightly. In 40 grafts whose graft flow was increased by more than 10 ml/min by dipyridamole, the patency rate (at 5 weeks) was 98 per cent, whereas that of the 10 other grafts, which responded poorly, was only 50 per cent (p<0.01). The serum concentration of dipyridamole, 3 minutes after intravenous injection, was 1.46±0.68 μg/ml, while the level of orally administrated dipyridamole, in 3 groups of patients who were given 50 mg, 75 mg and 100 mg, three times a day, respectively, was steady, being 0.68±0.20 μg/ml, 1.43±0.41 μg/ml and 1.73±0.50 μg/ml, 2 hours following ingestion. We concluded that intravenous dipyridamole increases the graft flow and that a better patency is obtained in those grafts in which the graft flow is increased by more than 10 ml/min. It is also expected that routine doses of oral dipyridamole possibly increase the graft flow after coronary bypass surgery. This paper was presented at the Xth World Congress of Cardiology held in Washington DC, USA, September 14–19, 1986     

Augmentation of coronary bypass graft flow induced by dipyridamole and its relation to bypass graft patency

To evaluate the effect of dipyridamole on coronary bypass graft flow, 10 mg of dipyridamole was injected intravenously, during the measurement of graft flow, at the time of surgery. Its concentration in serum was measured and compared with that after oral administration. In 50 individual vein grafts performed on 35 patients, graft flow increased from 65 +/- 37 to 96 +/- 55 ml/min (p less than 0.001) after the dipyridamole injection and the arterial pressure decreased slightly. In 40 grafts whose graft flow was increased by more than 10 ml/min by dipyridamole, the patency rate (at 5 weeks) was 98 per cent, whereas that of the 10 other grafts, which responded poorly, was only 50 per cent (p less than 0.01). The serum concentration of dipyridamole, 3 minutes after intravenous injection, was 1.46 +/- 0.68 micrograms/ml, while the level of orally administered dipyridamole, in 3 groups of patients who were given 50 mg, 75 mg and 100 mg, three times a day, respectively, was steady, being 0.68 +/- 0.20 micrograms/ml, 1.43 +/- 0.41 micrograms/ml and 1.73 +/- 0.50 micrograms/ml, 2 hours following ingestion. We concluded that intravenous dipyridamole increases the graft flow and that a better patency is obtained in those grafts in which the graft flow is increased by more than 10 ml/min. It is also expected that routine doses of oral dipyridamole possibly increase the graft flow after coronary bypass surgery.     

A study of the long-term graft patency using a saphenous vein graft following aorto-coronary bypass surgery

Long term graft patency after aorto-coronary (A-C) bypass surgery has been reported in the West and the data shows a lower patency rate in saphenous vein grafts (SVG) than internal mammary artery grafts. We studied the long term SVG patency in cases of Japanese patients at our institute, and we have compared our results with those in the West. The subjects, including children, were 211 cases who received A-C bypass surgery using at least one SVG from Jan., 1975 to Sept., 1989. 182 of these cases (examination rate: 86%) received a postoperative angiography one or three months after surgery. The postoperative study took the form of either a selective coronary angiography or a digital subtraction angiography. In 81 cases, using the same two methods, graft patency was reconfirmed from one to eleven years after surgery. Early graft patency including children was 95%. Long term graft patency in the adult cases was 89% from 1 to 2 years (mean: 1.3 years), 94% from 2 to 5 years (mean: 3.2 years), 88% from 6 to 11 years (mean: 7.1 years) following the operation. Six patients died during the post operative follow up period. Two cases were sudden death, one resulted from a reoperation for recurrent angina, two were caused by malignant neoplasm and other was the result of a cerebro-vascular accident. The results correlating the long term graft patency using a SVG and long term mortality were not as negative at our institute as they have been in studies done in the West.     

Operative flow measurements and coronary bypass graft patency.

Early (one week) and late (one year) postoperative angiography was performed in 142 patients having 310 grafts (117 right coronary artery [RCA], 134 left anterior descending [LAD], and 59 circumflex coronary artery [CCA]) to assess the factors responsible for failure of aorta-coronary artery saphenous vein grafts. Early catheterization revealed an 85.5 per cent patency rate with similar rates for each artery (RCA 88 per cent, LAD 85 per cent, and CCA 81 per cent). At one year 238 grafts remained patent, for a cumulative patency rate of 76.8 per cent with a similar distribution for each vessel (RCA 75 per cent, LAD 78 per cent, and CCA 76 per cent). Intraoperative flow measurements were correlated with early and late patency. Grafts with a basal flow less than 20 ml. per minute have a 42 per cent early closure rate and a 21 per cent late closure rate (cumulative 63 per cent). A basal flow of less than 40 ml. per minute was associated with a 25 per cent early failure and an 11 per cent late failure rate (cumulative 36 per cent). Basal flow at levels greater than 40 ml. per minute was not associated with an increased probability of graft closure. Absence of reactive hyperemia (30 second graft occlusion) was associated with a 19 per cent probability of early closure and a 31 per cent probability of cumulative thrombosis. A papaverine-induced flow increase (15 mg. given into the graft) of less than 100 per cent over basal flow gave a 20 per cent probability of early failure and 30 per cent probability of cumulative closure. Thus intraoperative basal flow measurements are of predictive value in determining the fate of aorta-coronary artery vein bypass grafts, and vasodilatory maneuvers provide little additional information.     

The comparison of the graft patency after coronary artery bypass grafting using coronary angiography and multi-slice computed tomography.

OBJECTIVE: Coronary angiography (CAG) is the gold standard method in evaluating graft patency following coronary artery bypass grafting (CABG), even though there are several kinds of non-invasive methods. Recently developed multi-slice CT (m-CT), having effective scan times up to 0.25 s and multi-row detector array systems, enable rapid imaging of cardiac structures, including coronary arteries during one breath-hold. We compared m-CT with CAG for the evaluation of graft patency following CABG. METHODS: Forty-two patients having undergone m-CT and CAG within 3 months of CABG were studied. Twenty-three patients underwent conventional CABG and 19 off-pump CABG. A total of 125 grafts were used, including 42 left internal mammary arteries (LIMA), 25 radial arteries (RA), 3 right internal mammary arteries (RIMA) and 55 vein grafts. RESULTS: CAG showed a 96% (120/125) patency rate (1 LIMA, 2 RA and 2 vein grafts were occluded). m-CT showed a 98% (122/125) correct positive ratio with a sensitivity and specificity of 98 and 100%, respectively. The sensitivity in LIMA, RA, RIMA and vein grafts was 98, 91, 100 and 100%, respectively, with 100% specificity for all. There was an equivocal result in the competitive grafts with native coronary artery that were patent in the CAG, but faint opacification with no significant flow in the m-CT. CONCLUSIONS: This study showed that m-CT was very simple, useful and accurate in evaluating graft patency during the early post-operative period following CABG, even though there was an equivocal result in the competitive grafts with a native coronary artery.     

Graft flow assessment and early coronary artery bypass graft failure: a computed tomography analysis

Open in a separate window OBJECTIVESWe evaluated graft patency by computed tomography and explored the determinants of intraoperative mean graft flow (MGF) and its contribution to predict early graft occlusion.METHODSOne hundred and forty-eight patients under a single surgeon were prospectively enrolled. Arterial and endoscopically harvested venous conduits were used. Intraoperative graft characteristics and flows were collected. Graft patency was blindly evaluated by a follow-up computed tomography at 11.4 weeks (median).RESULTSGraft occlusion rate was 5.2% (n = 22 of 422; 8% venous and 3% arterial). Thirteen were performed on non-significant proximal stenosis while 9 on occluded or >70% stenosed arteries. Arterial and venous graft MGF were lower in females (P_arterial = 0.010, P_venous = 0.009), with median differences of 10 and 13.5 ml/min, respectively. Arterial and venous MGF were associated positively with target vessel diameter ≥1.75 mm (P_arterial = 0.025; P_venous = 0.002) and negatively with pulsatility index (P_arterial < 0.001; P_venous < 0.001). MGF was an independent predictor of graft occlusion, adjusting for EuroSCORE-II, pulsatility index, graft size and graft type (arterial/venous). An MGF cut-off of 26.5 ml/min for arterial (sensitivity 83.3%, specificity 80%) and 36.5 ml/min for venous grafts (sensitivity 75%, specificity 62%) performed well in predicting early graft occlusion.CONCLUSIONSWe demonstrate that MGF absolute values are influenced by coronary size, gender and graft type. Intraoperative MGF of >26.5 ml/min for arterial and >36.5 ml/min for venous grafts is the most reliable independent predictor of early graft patency. Modern-era coronary artery bypass graft is associated with low early graft failure rates when transit time flow measurement is used to provide effective intraoperative quality assurance.     

The clinical significance of contrast enhanced computed tomography in acute pancreatitis

58 patients with alcohol-induced acute pancreatitis were studied by contrast enhanced computed tomography (CT). The patients were divided into groups both on the basis of the clinical course and the prognostic signs. The contrast enhancement curves were then plotted for these patients. All patients with uncomplicated pancreatitis had increased or normal contrast enhancement, whereas all those with fulminant pancreatitis had decreased contrast enhancement of the pancreas. The patients with three, or more prognostic signs had lower enhancement values than those with fewer prognostic signs, but the prognostic signs did not correlate as well with the clinical course as did the contrast enhancement.     

Coronary graft patency after perioperative myocardial infarction: a study with multislice computed tomography

A total of 55 consecutive patients who experienced perioperative myocardial infarction (MI) after coronary artery bypass grafting were studied using multislice computed tomography (MSCT) angiography to evaluate for graft patency. The MSCT detected acute graft occlusion in 23% grafts. Of the 55 patients, 40% patients had occluded grafts and perioperative MI in the area of the grafted vessels; remaining 60% had patent grafts with infarction in the area of the grafted vessels. Compared with the patients with patent grafts, those with occluded grafts had a higher blood sugar level. In addition, graft occlusion was higher in grafts with severe distal disease. Among the patients with patent grafts, luminal stenosis of the native vessels supplying the infarcted myocardium was higher than that in the native vessels supplying the non-infarcted myocardium. In conclusion, MSCT is feasible for the assessment of graft patency in the setting of perioperative MI. Graft occlusion is detected in less than half of the cases and usually occurs in the grafts with severe distal involvement and the patients with uncontrolled hyperglycemia. In patients with patent grafts, the severity of luminal stenosis of the native grafted vessel is the main predisposing factor for perioperative MI.     

Aortic distensibility and coronary artery bypass graft patency

Background  

Aortic distensibility is an elasticity index of the aorta, and reflects aortic stiffness. Coronary artery disease has been found to be substantially associated with increased aortic stiffness. In this study we aimed to retrospectively analyze the association of angiographically determined aortic distensibility with the patency rates of coronary bypass grafts     

Results of sequential aorto-coronary bypass grafting using saphenous vein graft

Seventy patients underwent sequential coronary artery bypass grafting with saphenous vein during 28 months period. Seventy eight sequential grafts comprising 165 distal anastomoses were performed. Early death was 2.9%. Postoperative angiographic evaluation within 6 months showed 86% patency of the 65 sequential grafts and 89% patency of the 136 distal anastomoses. The patency of anastomosis to left anterior descending artery (LAD), diagonal branch (Dx), obtuse marginal branch (OM), posterior lateral branch (PL), and posterior descending branch (PD) was 87% (13/15), 92% (36/39), 91% (40/44), 81% (26/32) and 100% (6/6), respectively. The patency of Dx-LAD, Dx-OM and OM-PL was 86% (12/14), 94% (15/16) and 76% (13/17), respectively. There was no significant difference in the patency rate according to the site of anastomosis and the inner diameter of the coronary artery. The patency of side to side anastomoses was 92% (65/71) which was not significantly different from that of the end to side anastomoses; 86% (56/65). These results showed sequential aorto-coronary vein grafting means to be effective for the complete coronary artery revascularization .