Lesions of the target vessel during minimally invasive myocardial revascularization

Localizing factors in atherosclerosis

Atherosclerotic vascular disease is the leading cause of death worldwide. Although the entire vascular bed is constantly exposed to the same risk factors, atheromatous lesions present a distinct intra-individual pattern of localization and progression, being consistently more frequent in specific segments of the arterial vascular bed. This peculiar distribution may be related to selective sensitivity of such locations to the influence of risk factors or to histopathological and flow differences, and has relevant clinical implications, as the prognosis of the disease varies according to localization. We here review the theories that have been formulated to explain such preferential locations, as its understanding can be useful to pursue diagnostic screening strategies and focused preventive measures.

Intracoronary shunt versus bulldog clamp in off-pump bypass surgery. Endothelial trauma: shunt versus clamp

BACKGROUND

During off-pump coronary bypass grafting, local vascular control of the target vessel and a bloodless field are crucial. The aim of this study is to asses the histopathological outcomes of intracoronary shunts and bulldog clamping on the beating heart in a canine model.

METHODS

Twelve healthy adult mongrel dogs weighing between 15 to 25 kg were included in the study. Following left thoracotomy, proximal left anterior descending artery segment 1 cm to distal of diagonal branch was marked. Arteriotomy at this site was performed and a shunt was inserted for 10 min in the shunt group. The bulldog clamp was applied 3 cm distal to the mark for 10 min after heparinization in the bulldog group. Thirty days after the procedure, the specimens of left anterior descending artery from both regions were collected and were examined. Vascular damage, presence of intimal hyperplasia, and denudation were noted.

RESULTS

Only intimal denudation was found significantly higher in the shunt group (P < 0.05). In this group, only one case had grade 0 endothelial damage. In the bulldog group, all cases had endothelial damage of various grades.

CONCLUSION

The proven advantages of temporary intracoronary shunts are well-known, e.g., preserving the ventricular functions. Despite these advantages, our study revealed an ultimate bad result for an off-pump coronary by pass patient: intimal denudation. We conclude that further studies with a larger number of subjects are needed to decide whether routine shunt insertion into coronary arteries during off-pump coronary bypass surgery is appropriate or not.

Controversies in the Use of Intraluminal Shunts During Off-Pump Coronary Artery Bypass Grafting Surgery

Technical advances have made the performance of multivessel off-pump coronary artery bypass feasible. Snaring and intraluminal shunts are the techniques used for vascular control. Snaring provides a bloodless surgical field, is usually well tolerated by the patient, and is supported by years of clinical experience. Intraluminal shunts aim to achieve hemostasis at the arteriotomy site and to allow antegrade flow to provide myocardial protection. There are unresolved issues regarding whether shunts have a clinical benefit, do provide adequate flow to provide myocardial protection, and whether they cause significant endothelial damage. In this article, we have reviewed the literature to lend perspective to these issues.

Chronic ultrastructural effects of temporary intraluminal shunts in a porcine off-pump model

BACKGROUND

Temporary intraluminal shunts (TILS) are routinely used in off-pump revascularization to facilitate the anastomosis while maintaining myocardial blood supply. Whereas tourniquet-occlusion can cause vessel wall trauma, potentially adverse chronic effects of TILS on the coronary intima have not been evaluated yet. This chronic large animal study investigated ultrastructural effects of TILS on the vessel wall.

METHODS

Four groups of acute and chronic pigs with either tourniquet-occlusion (TOUR) or TILS (40 kg; acute, n = 12; chronic, n = 20) were analyzed. Animals underwent median sternotomy, heparin (150 U/kg) administration, and left anterior descending coronary artery exposure. In groups with TOUR the left anterior descending coronary artery was temporarily occluded (10 minutes) with a tourniquet. In groups with TILS a silicone shunt (1.5 mm diameter, 12 mm length) was placed in the left anterior descending coronary artery more than 10 minutes and then removed, and the insertion was repaired. Thirty minutes after reperfusion all acute animals were sacrificed whereas chronic animals were extubated, maintained for 3 months, and then sacrificed. The left anterior descending coronary artery regions of occlusion or placement of the TILS silicone bulbs were examined histopathologically by scanning and transmission electron microscopy by a blinded pathologist.

RESULTS

In both acute and chronic investigations animals in the TILS group exhibited significantly less morphologic damage than animals in the TOUR group. In the acute phase significantly more loss of cell junction (p = 0.037), loss of endothelium (p = 0.032), and intimal edema (p = 0.037) in the TOUR group than in the TILS group was observed. Three months later, characteristic features with a changed pattern were detected: vacuolization of the cell (p = 0.03), loss of cell junction (p = 0.042), and removal of basal membrane (p = 0.046) as well as extensive loss of endothelium (p = 0.003) in the TOUR group compared with the TILS group.

CONCLUSIONS

Intimal lesions occur with both maneuvers early and late. However, animals in the TOUR group exhibited injuries significantly more often and more severely. Therefore, acute and chronic intimal integrity of the coronary vessel may be better preserved using TILS and may thus have a positive impact on the extent of de novo stenosis and long-term prognosis of the revascularized region.

Intraoperative ischemia and long-term events after minimally invasive coronary surgery

BACKGROUND

Concern has been raised about the effects of prolonged left anterior descending (LAD) artery occlusion during minimally invasive direct coronary artery bypass graft surgery (MIDCABG). We sought to assess the impact of myocardial dysfunction during MIDCABG on long-term outcome and the protective role of collateral circulation on myocardial ischemia.

METHODS

Myocardial function was evaluated in 92 patients by intraoperative transesophageal echocardiography during MIDCABG.

RESULTS

Wall motion score index increased during LAD occlusion (p < 0.00l) and reverted after LAD reopening (p < 0.001 versus occlusion and p = not significant versus baseline). The change in wall motion score index (occlusion versus baseline) was higher in patients with multivessel disease (p < 0.05) and in patients with LAD Thrombolysis in Myocardial Infarction study classification flow grade 2 or less without collateral circulation (p < 0.05). Myocardial stunning was documented in 12 patients (13%). The 5-year adverse event rate (including death, myocardial infarction, and revascularization) was 12%. By multivariate Cox regression analysis, multivessel disease, but not perioperative ischemia or stunning, was the only predictor of event-free survival.

CONCLUSIONS

During MIDCABG anterior wall dysfunction is transient, with prompt recovery after completion of the anastamosis in most cases; myocardial stunning can be documented in a minority of patients. Flow either antegrade or retrograde in the LAD territory plays a protective role against the development of ischemia. Multivessel disease, but not perioperative ischemia or stunning, predicts long-term event-free survival.

Evolution of OPCAB surgery in a single institution

Off-pump coronary artery bypass (OPCAB) grafting is becoming popular worldwide. The development of exposure and stabilization techniques have made this surgery a simple, safe, and routine procedure. The evolution of OPCAB surgery at our institution is presented and discussed.

Coronary endothelial injury after local occlusion on the human beating heart

BACKGROUND

Occlusion of coronary arteries during beating heart surgery bears the potential for mechanical trauma to the arterial wall with consequent endothelial injury. The aim of this study was to elucidate the effects of local occlusion on the beating heart in human coronary arteries.

METHODS

Coronary arteries of patients with dilated cardiomyopathy (n = 7) or ischemic heart disease (n = 10) undergoing heart transplantation were locally occluded after starting cardiopulmonary bypass. Immediately after excision of the diseased heart, the vessels were fixed. Unoccluded segments served as controls. Integrity of endothelial lining was observed with scanning electron microscopy.

RESULTS

Scanning electron microscopy revealed significantly more severe endothelial injury in the area of occlusion than in the adjacent, not manipulated control segments. In the region of local occlusion, plaque rupture was noted in three of 34 atherosclerotic vessel specimens, injury to side branches was evident in two of 44, and local microthrombus formation was evident in six of 44 samples.

CONCLUSIONS

Local occlusion of human coronary arteries during beating heart coronary surgery may cause focal endothelial denudation, local microthrombosis, atherosclerotic plaque rupture, and injury to target vessel side branches.

Surgical myocardial revascularization without cardiopulmonary bypass

BACKGROUND

Though coronary artery bypass grafting (CABG) without cardiopulmonary bypass is being performed with increasing frequency, in the absence of adequate angiographic follow-up, safety, reproducibility, and efficacy of the procedure remain doubtful. In this prospective study, we report the results obtained by 100% angiographic follow-up of 96 consecutive patients.

METHODS

A total of 96 patients (age range 33 to 76 years) underwent CABG without cardiopulmonary bypass. Single vessel disease was present in 46 (47.9%) patients, double vessel disease in 31 (32.3%), and triple vessel disease in 19 (19.8%) patients. All patients were operated through a standard midsternotomy and an optimal combination of pharmacological and mechanical methods were used to restrict cardiac movements during anastomosis. All patients underwent coronary angiography before discharge from the hospital.

RESULTS

A total of 160 grafts were placed (range 1 to 4 grafts per patient, average 1.7+/-0.3 grafts per patient). A single graft was placed in 46 patients, double grafts in 38, triple grafts in 10, and quadruple grafts in 2 patients. Various grafts included pedicled left internal mammary artery (LIMA) (n = 95), free LIMA (n = 1), right internal mammary artery (n = 14), radial artery (n = 24), right gastroepiploic artery (n = 5), and saphenous vein grafts (n = 21). Operative mortality was 1.0% (1 of 96). Two patients required reoperation for excessive bleeding. Mean hospital stay was 5.7+/-1.2 days. Overall angiographic patency was 95.0% with LIMA patency of 97.9% (93 of 95). One patient with block in midsegment of LIMA was reoperated using cardiopulmonary bypass. Follow-up ranged from 4 to 17 months (mean 8.2+/-3.1 months). Two patients (one with narrowed LIMA to left anterior descending artery anastomosis, and one with patent anastomosis) had residual angina.

CONCLUSIONS

Coronary artery bypass grafting without cardiopulmonary bypass is a reproducible, effective, and safe option in selected group of patients. A conscientious approach in patient selection and route of operation is required.

Pseudoaneurysm of a septal perforator in beating heart coronary bypass grafting

A 46-year-old man with unstable angina underwent beating heart coronary bypass grafting for a left anterior descending coronary artery. Postoperative angiography showed intramuscular extravasation (6 x 8 mm) distal to the anastomosis, which was most likely the result of a needle injury caused by a snare during the operation. Follow-up angiography 2 weeks later revealed no extravasation.

Early and follow-up angiography in minimally invasive coronary bypass without mechanical stabilization

BACKGROUND

This study was undertaken to assess the early and late outcome of coronary anastomosis constructed on a beating heart without the help of mechanical stabilization.

METHODS

All consecutive patients (51) from January 1996 to September 1997 who had bypass done by one surgeon using a left minithoracotomy (39) or median sternotomy (12) on a beating heart with occlusive local snares without mechanical stabilization underwent follow-up angiography early (100%) (within 6 hours) and late (63.5%) at a mean of 9.6+/-4.48 months (range, 3.3 to 19.1 months).

RESULTS

The cumulative late patency was 95.4% (83 of 87 patients), with two early and two late occlusions. There was no early or late mortality or perioperative myocardial infarction. Two patients (3.9%) developed recurrent angina. Four anastomotic irregularities (4 of 32 patients, 12.6%) have cleared up on follow-up angiography. There was no evidence of late stenosis at the snare sites used for local occlusion.

CONCLUSIONS

Minimally invasive coronary bypass is safe and effective. Early angiographic abnormalities should be interpreted with caution and we could not demonstrate any long-term deleterious effects of local snaring.

Septal branch right ventricular fistula: a complication in coronary artery snaring

We report a septal branch right ventricular fistula complicated after coronary snaring in coronary artery bypass surgery without aortic cross-clamping. The tip of the needle of the snaring suture is made blunt in order to decrease the risk of mechanical injury, but trauma to the septal branch is possible. This rare complication of snaring should be taken into consideration in performing aortic nonclamping coronary artery bypass surgery.

Procoagulant activity after off-pump coronary operation: is the current anticoagulation adequate?

BACKGROUND

Hemostasis is preserved after off-pump coronary operations compared with conventional coronary procedures. However, this preserved hemostasis may result in a procoagulant activity.

METHODS

We prospectively studied coagulation in 22 patients who underwent off-pump coronary operation either through a midline sternotomy (n = 14) or with minimally invasive anterolateral thoracotomy (n = 8).

RESULTS

Procoagulant activity, represented by prothrombin factor 1 and 2, remained at baseline levels during operation but increased significantly on postoperative day 1. Factor VII remained at baseline levels during the operation but decreased significantly on postoperative day 1. Fibrinolysis was increased as indicated by the fibrin degradation products on postoperative day 1. A promoted hemostasis attributable to endothelial activation was indicated by the increase in von Willebrand factor on postoperative day 1. Platelets counts and platelet activation (beta-thromboglobulin) remained at baseline levels after the operation. No adverse clinical events occurred.

CONCLUSIONS

Patients undergoing off-pump coronary operation show an increased procoagulant activity in the first postoperative 24 hours regardless of the surgical approach (midline sternotomy or anterolateral thoracotomy). This procoagulant activity is not mediated by platelet-related factors. Therefore, a specific perioperative prophylactic pharmacologic regimen is advisable.

Early angiographic results after revascularization by minimally invasive direct coronary artery bypass (MIDCAB)

OBJECTIVE

Anastomosing the left anterior descending artery (LAD) by use of the internal mammary artery (IMA) via an anterior minithoracotomy represents the most commonly performed minimally invasive direct coronary artery bypass (MIDCAB). However, little is known about angiographic results beyond patency rates.

METHODS

Therefore, a retrospective analysis of 205 consecutive control angiographies was performed evaluating anastomototic patency as well as the angiographic morphology of the left IMA and the LAD.

RESULTS

The overall anastomotic patency rate was 98.0%. As a result of incomplete IMA preparation (6-15 cm) large side branches (n = 4), or an IMA course under tension (n = 6) were occasionally observed. Despite a tension-free course, the IMA appeared fixed to the chest wall without functional compromise in 21 cases. A restrictive thrombus formation occurred once, IMA dissection was not seen. Two of the grafts developed spasms. A distal IMA stenosis >50% was seen in five cases. Stenosis of the anastomosis (>50%) itself was found once, as well as unexpected malinsertation to diagonal branches (n = 4). Compared with preoperative angiograms, de novo stenoses of the LAD were assessed proximal (14< or =50%, 2>50%) and distal (15< or =50%, 2>50%) to the anastomosis. Elevation of the LAD out of the vascular bed was an additional finding (n = 12) in a few cases.

CONCLUSIONS

The overall patency of MIDCAB-LAD-grafting appears to be equivalent to conventional IMA grafting to the LAD. Particular angiographic findings, however, may be directly associated to the applied surgical technique.

Left anterior descending coronary artery bypass grafting through minimal thoracotomy

BACKGROUND

In recent years, minimally invasive direct coronary artery bypass grafting has emerged as a valid tool for revascularization in a select group of patients with severe lesions of the left anterior descending coronary artery. Here we report the clinical results using two devices designed by us to facilitate the harvesting of the left internal mammary artery up to its origin and to occlude and stabilize the left anterior descending coronary artery while placing the anastomosis.

METHODS

From January 1996 to January 1998, 122 patients underwent minimally invasive direct coronary artery bypass grafting in the Department of Cardiac Surgery, Favaloro Foundation. One hundred twelve patients received a single left internal mammary artery-left anterior descending coronary artery bypass graft, and in 10 patients, an additional bypass graft was performed.

RESULTS

Most patients were discharged on day 2 or 3 after the procedure. Three patients (2.5%) had a perioperative myocardial infarction. The overall hospital mortality rate was 3.3% (4 patients).

CONCLUSIONS

The combination of team experience, more careful dissection of the left internal mammary artery up to its origin, and use of the stabilizer-occluder and interrupted suture technique for the anastomosis has markedly improved our results.

Systematic clinical and angiographic follow-up of patients undergoing minimally invasive coronary artery bypass

OBJECTIVE

We herein analyze the results of the systematic clinical and angiographic control performed in a series of 77 consecutive patients undergoing minimally invasive coronary artery bypass.

METHODS AND RESULTS

From January 1995 to June 1997, 77 patients underwent minimally invasive coronary artery bypass at our institution. There was one inhospital death, one noncardiac late death, and five patients had to be reoperated for graft malfunction. A total of 76 patients underwent postoperative angiographic follow-up. In 66 cases (86.8%) the thoracic artery graft, the target vessel, and the anastomosis were patent and functioning normally. In one case the graft was occluded. In the remaining nine cases the thoracic artery graft was patent but with major anomalies of either the anastomosis, the target vessel, or the course of the thoracic artery. Patients operated using especially designed instruments had angiographic results clearly superior to those of patients operated using conventional instrumentation (perfect patency rate 100% vs 81.8%). At a mean follow-up of 18 months, 98.5% of the surviving patients are asymptomatic with negative myocardial scintigraphy.

CONCLUSIONS

The perfect patency rate of minimally invasive revascularization performed without the use of dedicated instruments is unacceptably low. The use of specific devices is likely to result in a substantial improvement in the angiographic results.