Factors affecting upper airway patency

We studied the following functional factors which affect upper airway patency. First, the effects of inspiratory resistive loading, increased pulmonary resistance, hypercapnic gas or hypoxic gas loading on the upper airway pressure-flow (P-F) relationship were studied. The upper airway P-F curves under these loading conditions shifted upward with load dependency. Secondly, effects of limb muscle contraction on upper airway resistance (Rua) were studied. Rua decreased reflexly during limb muscle contraction. Thirdly, effects of body position on the stability of the upper airway were studied. The upper airway was kept patent in the lateral position. Fourthly, effects of electrical stimulation of the genioglossus muscle on P-F relationship of upper airway were studied. P-F curves of upper airway shifted upward with increase in stimulation frequency. Fifthly, effects of nasal or oropharyngeal lubrication by artificial surfactant on the critical stimulation frequency (CSF) for upper airway opening were studied. Nasal or oropharyngeal lubrication decreased CSF. Based on these fundamental studies, we applied constrained lateral position, submental stimulation due to demand-type stimulator and nasal or oropharyngeal lubrication for treatment of patients with obstructive sleep apnea syndrome (OSAS). We found these three methods were effective in treatment of OSAS patients.     

双源CT评价冠状动脉搭桥术后桥血管通畅率的临床研究

目的比较非体外循环下冠状动脉旁路移植术（OPCABG）与常规冠状动脉旁路移植术（常规CABG）术后5年血管桥的通畅率。方法2006年1月至2008年1月间40例单独行冠状动脉旁路移植术（CABG）的患者资料回顾性地被分为OPCABG组和常规CABG组。OPCABG组通过胸骨正中切口,在非体外循环心脏不停跳下完成CABG;常规CABG组建立常规体外循环心脏停搏下完成CABG。两组术前的一般情况无明显差异。利用双源CT造影检查及CT图像后处理,研究两种术式各条血管桥的通畅情况。结果常规CABG组及OPCABG组左乳内动脉（uMA）到前降支（LAD）的通畅率都达到100％,静脉桥的通畅率分别为93．87％和94．23％,组间比较差异均无统计学意义。结论OPCABG旁路血管桥的3~5年通畅率可以和常规CABG相媲美。OPCAB治疗冠心病的初期结果显示可以减少术后并发症,减少患者术后呼吸机辅助时间、ICU留观时间和住院时间,降低住院费用。     

Left ventricular performance and graft patency after coronary artery-saphenous vein bypass surgery: early and late follow-up.

Left ventircular performance and graft patency were studied postoperatively at 2 weeks in 19 patients, and at 9 months in 15 patients. At early follow-up, left ventricular ejection fraction and mean rate of circumferential shortening were unchanged for the group as a whole, but were slightly improved in patients who had had a moderately abnormal preoperative ejection fraction of 0.30 to 0.60. At late follow-up, 10 of 14 patients had occluded at least one graft or the proximal segment of the grafted coronary artery and had an associated decrease in ventricular function. The risk of graft occlusion was greater if the preoperative ejection fraction was decreased; seven of 10 patients with a preoperative EF of less than 0.60 suffered one or more graft occlusions, but only three of 16 patients with a preoperative EF greater than 0.60 had a postoperative graft occlusion (p is less than 0.05). The results suggest that bypass graft surgery is not generally indicated as a measure to improve ventricular function in patients with ischemic heart disease.     

Immediate postoperative aspirin improves vein graft patency early and late after coronary artery bypass graft surgery. A placebo-controlled, randomized study

BACKGROUND. The efficacy of aspirin for prevention of thrombotic graft occlusion after coronary artery bypass grafting (CABG) depends both on the dosage and time window of administration. Early and late graft patency were therefore assessed in a prospective, double-blind, randomized, placebo-controlled trial of aspirin, 324 mg daily, given within 1 hour of CABG. METHODS AND RESULTS. Angiographic graft patency was determined at 1 week (231 patients) and 1 year (219 patients) after CABG. The early vein graft occlusion rate was 1.6% on aspirin and 6.2% on placebo (p = 0.004), and late graft occlusion rate was 5.8% on continued aspirin and 11.6% on placebo (p = 0.01). New graft occlusion between 1 week and 1 year was less common in patients on aspirin than on placebo (4.3% versus 7.4%, p = 0.013). The protective effect of aspirin against occlusion persisted in most subgroups of graft type, graft flow, diameter of recipient artery, location of grafted artery, and endarterectomy. Mean chest tube blood loss for the first 24 hours was 571 ml for the aspirin group and 563 ml for the placebo group. Red cell transfusion requirements were 902 ml in the aspirin group and 934 ml in the placebo group (p = NS). The reoperation rate was 4.8% in the aspirin group and 1% in the placebo group (p = 0.1). CONCLUSIONS. Immediate postoperative administration of aspirin (324 mg) improves early graft patency and, with continued usage, protects against further occlusion up to 1 year after CABG. Postoperative blood loss was similar in the two groups; however, aspirin was associated with a nonsignificant higher rate of reoperation.     

Routine intraoperative angiography improves the early patency of coronary grafts performed on the beating heart

OBJECTIVES: The techniques of performing coronary revascularization without cardiopulmonary bypass are rapidly evolving. However, concern remains regarding the accuracy of coronary artery anastomoses performed on the beating heart. This report reviews the use of intraoperative angiography in the critical appraisal of "off-pump" coronary artery bypass graft (CABG) surgery. PATIENTS: Intraoperative angiography was performed in 24 consecutive patients undergoing CABG surgery without cardiopulmonary bypass. In all, 24 left internal mammary artery (LIMA) grafts and 18 saphenous vein bypass grafts were assessed for patency, anastomosis quality, distal and proximal runoff, and correct placement. RESULTS: All of the saphenous vein-to-coronary artery anastomoses were widely patent, although two patients (8%) required revision of their LIMA grafts on the basis of angiographic findings. CONCLUSION: Intraoperative angiography permits the surgeon to immediately appraise the CABG and to revise, if necessary, any graft abnormality, thus potentially eliminating the need for early repeated surgery. The practice of routine intraoperative angiography is likely to improve the outcome of CABG surgery on the beating heart.     

Nonangiographic assessment of coronary artery bypass graft patency

Coronary artery bypass graft patency can be assessed using the indirect techniques of evaluating patients' symptoms and exercise tolerance, changes in stress electrocardiogram, radioisotope regional perfusion, and myocardial wall contraction. The direct techniques assess graft patency directly by visualizing grafts using conventional computed tomography (CT), ultrafast CT, magnetic resonance imaging, digital subtraction angiography, and echocardiography. The advantages and disadvantages of each of these modalities are reviewed. At the present time, ultrafast CT and possibly magnetic resonance imaging and Doppler appear to be the only techniques besides angiography that can consistently evaluate bypass graft patency. Although they have the advantage of being minimally invasive, they cannot show graft stenosis or sequential graft patency. These techniques are best used in following patients after coronary bypass graft surgery and ruling out graft closure as the source of chest pain.     

Improved graft patency in patients treated with platelet-inhibiting therapy after coronary bypass surgery

One hundred forty-seven consecutive coronary bypass patients were enrolled in a randomized, double-blind, risk-stratified, placebo-controlled prospective trial evaluating the effect on graft patency of 325 mg tid aspirin (ASA) plus 75 mg tid dipyridamole (DP) or ASA alone. One hundred twenty-seven patients (399 total grafts) underwent surgery, initiation of drug therapy 67 +/- 27 (SD) hr postoperatively, five clinic visits, and repeat angiography at 1 year. A logistic regression statistical model was used to determine the effects of 28 different measured variables on graft patency and to adjust for these effects in determining the relationship between antiplatelet therapy and graft occlusion. No patient-specific variable contributed significantly to the prediction of occlusion in either the placebo or the treated group. Six graft-specific variables (arterial diameter, severity of stenosis, graft flow, reactive hyperemia, presence or absence of collaterals, and graft type) did contribute and were included in the model. Twenty-one percent of placebo-treated grafts became occluded. Compared with placebo, the relative risk of graft occlusion with ASA was 0.47 (p = .04); with ASA + DP, it was 0.50 (p = .04). This benefit was principally due to reduction of occlusion in the most common and presumably most important groups of grafts, those in which flow exceeded 40 ml/min, or supplying arteries having luminal diameters greater than 1.5 mm. Grafts lacking reactive hyperemia had a 32% occlusion frequency in placebo-treated patients; relative risk of their occlusion averaged 0.26 (p less than .01) with platelet-inhibiting therapy.(ABSTRACT TRUNCATED AT 250 WORDS)     

体外循环与非体外循环下冠脉旁路移植术后的血管桥通畅比较

目的：比较非体外循环下冠状动脉旁路移植术（OPCABG）与常规冠状动脉旁路移植术（CCABG）术后3-4年时血管桥的通畅率。方法：2003年1月-2004年12月间40例单独行冠状动脉旁路移植术（CABG）的患者资料回顾性地被分为OPCABG组和CCABG组。OPCABG组通过胸骨正中切口,在非体外循环心脏不停跳下完成CABG;CCABG组建立常规体外循环,心脏停搏下完成CABG。两组术前的一般情况无明显区别。利用多层螺旋CT（multislice spiral CT,MSCT）造影检查及CT图像后处理,研究两种术式各条血管桥的通畅情况。结果：CCABG及OPCABG组在左乳内动脉（LI MA）到前降支（LAD）的通畅率分别达到94.1%,94.4%,后降支（PDA）为88.2%,91.6%,钝缘支（包括对角支）的通畅率分别为88.9%,90.9%,静脉桥的通畅率为87.8%,88.0%,动脉桥的通畅率为85.7%,91.3%。各组间统计差别均无显著性。结论：OPCABG旁路血管桥的3-4年通畅率可以和CCABG相媲美.OPCAB治疗冠心病的初期结果显示可以减少术后并发症、减少患者术后呼吸机辅助时间和ICU留观时间、住院时间,降低住院费用,它的普及势在必然。     

Direct non-invasive techniques for assessing coronary bypass graft patency

Summary Venous digital subtraction angiography (vDSA) and computed tomography (CT) are two non-invasive techniques that allow direct imaging of coronary grafts. Neither of them is 100% accurate when compared to selective angiography.We studied 52 patients with 107 coronary grafts (101 saphenous and 6 mammary artery grafts) by CT and vDSA. Fifty patients had control selective angiography and 2 had control digital arterial aortography. CT correctly diagnosed 88 of the 95 patent grafts and 8 out of the 12 occluded grafts (in 1 patient 3 patent grafts could not be well analyzed owing to artifacts from pacemaker wires). vDSA correctly identified 93 patent grafts and the 12 occluded grafts, allowing the correct diagnosis of the 11 non/or misdiagnosed CT grafts. CT allowed the correct identification of ihe 2 misdiagnosed vDSA grafts.These results show that when there was agreement between CT and vDSA there were no diagnostic errors and that the combination of these two non-invasive techniques may avoid selective angiography for studying coronary bypass graft patency.     

Usefulness of dipyridamole stress echocardiography for predicting graft patency after coronary artery bypass grafting

Noninvasive techniques often provide controversial results in patients who have coronary artery bypass grafts (CABGs). Vasodilator stress echocardiography allows semi-simultaneous imaging of CABG flow and segmental left ventricular wall motion. To assess the comparative and additive value of regional flow and function for noninvasive evaluation of graft patency status, we evaluated 110 consecutive patients who underwent CABG and who were scheduled for coronary angiography. All patients underwent stress echocardiography with dipyridamole (0.84 mg/kg) and atropine (1 mg), including wall motion analysis by 2-dimensional echocardiography and Doppler evaluation of flow reserve of each CABG. Echocardiographic findings were compared with angiographic data. Four patients had inadequate acoustic windows. The remaining 106 patients had 226 grafts performed. Stress echocardiography showed 67% sensitivity, 91% specificity, and 71% accuracy for identification of 50% to 100% stenosis in the graft or in the recipient coronary vessel. There was a fair agreement with angiography (kappa coefficient 0.60). Identification of impaired coronary bypass flow reserve (i.e., <1.9 for internal mammary grafts and <1.6 for saphenous vein grafts) by Doppler had 91% sensitivity, 88% specificity, and 89% accuracy for graft stenosis. There was good agreement with angiographic findings (kappa 0.77). The combination of the 2 techniques achieved 93% sensitivity, 93% specificity, and 93% accuracy, showing a very good agreement with the patency status of the grafts as evaluated at angiography (kappa 0.85). The combined assessment of wall motion and flow reserve in patients who underwent CABG is feasible and provides an accurate estimate of graft patency status by increasing sensitivity of stress echocardiography and specificity of Doppler flow reserve.     

冠状动脉旁路移植术序贯和单一静脉桥通畅率荟萃分析

目的:比较冠状动脉旁路移植术(CABG)后序贯和单一大隐静脉桥通畅率。方法:检索PUBMED、EMBASE、The Cochrane Library及中国生物医学文献数据库。文献纳入标准:两组患者分别行序贯和单一大隐静脉CABG术;前瞻性或回顾性队列研究,须满足非随机研究方法组制定的队列研究特征;运用冠状动脉造影或超高速CT检查旁路移植术至少1个月以后桥血管通畅情况。文献纳入、数据提取和文献质量评定均由两名研究者独立完成。运用Rev Man5.0和Stata10.0软件进行数据处理,合并相对危险度(RR)作为分析统计量,95%可信区间(CI)为判断结果标准。结果:12篇文献纳入本研究。序贯桥梗阻风险低于单一桥(13.56%vs.19.18%,RR=0.67,95%CI:0.60~0.74);序贯桥中侧侧吻合梗阻风险低于端侧吻合(9.58%vs.14.07%,RR=0.52,95%CI:0.34~0.80);序贯桥和单一桥中端侧吻合梗阻风险,差异无统计学意义(14.07%vs.13.61%,RR=0.85,95%CI:0.68~1.06)。结论:CABG后大隐静脉序贯桥中长期通畅率优于单一桥,序贯桥中侧侧吻合口通畅率优于端侧吻合口,序贯桥和单一桥端侧吻合口通畅率无差别。     

Myocardial perfusion scintigraphy with thallium-201 for prediction of graft patency early after internal mammary artery graft surgery

Myocardial perfusion scintigraphy with thallium-201 was performed in fifty-four patients after internal mammary artery (IMA) graft to the left descending coronary artery to determine the influence of the flow rate in the IMA on myocardial perfusion after the procedure. The flow rate in the IMA was 40 to 200 ml/minute (mean 103 +/- 26.6 ml/min). Myocardial perfusion after IMA surgery was good in 44 patients (82%). There was a correlation between IMA flow rate and surgical results. Only 53% of patients with IMA flow rates below 100 ml/min to atmosphere showed good myocardial perfusion.     

Metabolic syndrome negatively impacts early patency of saphenous vein grafts

BACKGROUND: Coronary artery bypass grafting has been performed for a long period utilizing saphenous vein grafts, the fate of which might be crucial to prognosis following the operation. Metabolic syndrome, on the other hand, has become an increasingly important part of cardiovascular practice. We examined whether there was any negative effect of metabolic syndrome on saphenous vein graft patency in a relatively short term (< or =5 years). METHODS: Coronary angiograms of 314 consecutive patients (mean age 62.6+/-8.5 years), having at least one saphenous vein bypass graft within the last 5 years, were evaluated. RESULTS: One hundred and twenty-one patients (group 1) had either an occluded saphenous vein graft or a saphenous vein graft with a significant lesion, and 193 patients (group 2) had patent saphenous vein grafts. Metabolic syndrome was present in 46.2% of all patients (n=145), in 57% of patients in group 1 and in 39.4% of patients in group 2 (P=0.002). Having metabolic syndrome increased the risk of saphenous vein graft occlusion or having a significant lesion on saphenous vein grafts by 2.04-folds. In multivariable logistic regression, smoking (P=0.015, odds ratio=1.88), metabolic syndrome (P=0.019, odds ratio=1.81) and diabetes mellitus (P=0.048, odds ratio=1.36) were found to be associated with poor venous graft fate in the relatively short-term period after bypass. CONCLUSION: Metabolic syndrome seems to impact saphenous vein graft patency negatively in the relatively short term.     

201- Thallium imaging as an indicator of graft patency after coronary artery bypass surgery

In a prospective study, forty one patients underwent myocardialimaging using 201 thallium (²⁰¹ Tl) scmtigraphy before and 6months after coronary artery bypass grafting (CABG). The resultswere compared with the findings at coronary arleriography performedat the same time. ²⁰¹ Tl was injected at peak exercise level performing an exercisescintigram. A thallium image equivalent to a redistributionscan was obtained at rest approximately 4 h after the injectionof²⁰¹ Tl. The overall angiographic patency rate was 0.77. Postoperativemyocardial perfusion was improved in 26 patients (88%) having72 of 83 grafts patent (patency rate 0.87). New perfusion defectsor unchanged ischaemic patterns were found in 5 patients, whohad 2 of 13 grafts patent (graft patency 0.15). Estimation ofthe graft status by ²⁰¹ Tl-scinligraphy showed a sensitivity,specificity, and predictive value of a positive and negativeresult of 0.71, 0.94, 0.79 and 0.91, respectively, using angiographicfindings as a reference. It is concluded, that comparison between preoperative and postoperative²⁰¹ Tl imaging of the myocardium at exercise and rest providesuseful information on graft patency after CABG. The procedureis superior to graft patency estimation based on resting orpostoperative scintigrams only.     

Evaluation of coronary bypass graft patency by ultrafast computed tomography

A noninvasive technique for determining bypass graft patency is greatly needed. To determine if bypass graft patency could be accurately assessed with ultrafast computed tomography (CT) following an intravenous contrast injection, ten patients with 21 coronary bypass grafts were studied. All patients had cardiac catheterization and ultrafast computed tomographic studies within one month of each other. The sensitivity of detecting angiographically open grafts with ultrafast CT was 94.1% (16/17), specificity of detecting angiographically closed grafts was 100% (4/4), and accuracy was 95.2% (20/21). These preliminary results in a small clinical series indicate that ultrafast CT may be a useful, minimally invasive technique for evaluating coronary bypass graft patency.