Effects of intracoronary shunts on coronary endothelial coating in the human beating heart

Outcomes of off-pump versus on-pump coronary artery bypass graft surgery in patients with severely dilated left ventricle

BACKGROUND

Currently, off-pump coronary artery bypass (OPCAB) grafting has been the standard procedure for surgical revascularization in patients with coronary artery disease (CAD). This study aimed to examine the safety and applicability of OPCAB compared with on-pump coronary artery bypass (ONCAB) in patients with severely dilated left ventricle.

METHODS

A retrospective study of giant left ventricle patients [left ventricular end diastolic diameter (LVEDD) ≥ VE mm] undergoing coronary bypass grafting from 2009 through 2015 at a single center was conducted. Preoperative and intraoperative risk factors, and postoperative outcomes were analyzed. Survival analysis was carried to analyze survival rate during follow-up.

RESULTS

A total of 24 patients underwent ONCAB, and 26 underwent OPCAB. Both groups had similar preoperative profiles. Two cases from each group died during in-hospital time. In comparison to OPCAB, there was longer operation and post-surgery intubation time and more renal dysfunction in ONCAB group (P<0.05). One-year survival between OPCAB and ONCAB were not significantly different (87.5% vs. 92.3%, P>0.05).

CONCLUSIONS

OPCAB is a safe and feasible alternative for CAD patients with giant left ventricle, offering a significant advantage over ONCAB with regards to renal function, operation duration and length of ventilation.

Coronary artery spasm following off-pump coronary artery bypass surgery

Coronary artery spasm after coronary artery bypass surgery may result in life-threatening arrhythmias, circulatory collapse, or death. We report two cases of coronary artery spasm after coronary artery bypass surgery, one of which developed ventricular fibrillation requiring extracorporeal membrane oxygenation support. Both patients were discharged in good condition and are currently followed as outpatients. Unexpected sudden hemodynamic compromise could be due to coronary vasospasm, and this should be considered as one of the possible differential diagnoses. We were able to prevent the lethal consequences seen with coronary artery spasm by early diagnosis and management.

A novel coronary active perfusion system using a conventional intra-aortic balloon pump for off-pump coronary artery bypass grafting

OBJECTIVE

It is important for coronary active perfusion systems to avoid myocardial ischemia during off-pump coronary artery bypass grafting. We have developed a new concept for a perfusion system to pump blood based on changes in helium gas volume. This system uses a conventional intra-aortic balloon pump to activate the perfusion pump. Our study used basic and animal experiments to investigate the most suitable system for coronary perfusion using this new concept.

METHODS

A conventional intra-aortic balloon pump was used to supply power. A device for perfusion was developed with a balloon placed inside a stiff syringe barrel. The device was connected to the helium gas line of the intra-aortic balloon pump. Changes in flow with changes in augmentation level were noted when volumes outside and within the balloon were changed. Six pigs with occlusion of the left anterior descending artery were used for system validation, with monitoring to identify changes in hemodynamics and cardiac enzyme levels.

RESULTS

In the basic experiment, an 80-mL outside volume and 3.0-mL inner volume resulted in the greatest percentage change in flow rate with respect to changes in augmentation. In the animal experiment, the new coronary active perfusion system prevented myocardial ischemia during coronary occlusion.

CONCLUSIONS

We clarified the most suitable method for our new coronary active perfusion system. Using this system, safe anastomosis was consistently performed in animal experiments. Clinically, off-pump coronary artery bypass may potentially be performed more safely and easily using this new system.

Safe introduction and quality control of new methods in coronary surgery

Introduction:

The first part of the paper analyses off pump coronary bypass surgery (OPCAB), which is compared with traditional on-pump procedures (ONCAB). Furthermore ,the paper evaluates the use of a new automatic device for performance of the proximal anastomosis and finally the effect of intracoronary shunt on myocardial ischemia during OPCAB. The main goal of the paper is to demonstrate the importance of careful clinical studies during introduction of the new techniques in cardiac surgery.

Methods:

Statistical analysis was performed on a large clinical database from Buffalo, NY, USA comparing OPCAB and ONCAB. Subsequently, a sequential controlled clinical study compared patients operated with a new automatic connector device to patients operated with classic suture technique. Finally a randomized study was performed to evaluate the effect of the use of an intracoronary shunt during construction of distal anastomosis.

Results:

The studies from Buffalo demonstrated reduced complications rates in high risk patients when OPCAB techniques were used. The use of connector devices in saphenous venous anastomosis was clearly inferior to standard technique. Intracoronary shunt was found to be beneficial by preventing ischemia.

Discussion:

Numerous studies have studied the results of OPCAB vs ONCAB and although results are variable it seems that OPCAB is advantageous in high risk patients, while in low risk patients there are much less if any benefit. The results of the studies of connector devices caused the product to be taken off the market. The value of shunt in OPCAB was clearly demonstrated by the randomized studies.

Conclusion:

The investigations presented in this paper clearly demonstrates the importance of well-designed studies when new surgical methods are introduced. In the present period of rapid technological development, carefully controlled, un-biased clinical trials are crucial to preserve patient safety and avoid unjustified societal cost.

Prolonged indwelling time of temporary vascular shunts is associated with increased endothelial injury in the porcine mesenteric artery

BACKGROUND

Temporary intravascular shunts (TIVS) have been used as a damage control surgery (DCS) adjuncts in superior mesenteric artery (SMA) injuries, both experimentally and clinically. However, no study to date has evaluated the relationship between shunt indwelling time and resultant endothelial cell (EC) injury. We hypothesized that prolonged use of TIVS in SMA injuries would jeopardize EC integrity.

METHOD

After laparotomy, the SMA was clamped and transected while pigs were hemorrhaged to 40 mm Hg for 30 minutes. A TIVS was inserted between transected ends of the SMA without systemic anticoagulation. Totally, 24 animals were resuscitated and randomized to different shunt indwelling time groups: A, 3 hours; B, 6 hours; C, 9 hours; and D, 12 hours. Patency of shunts was monitored and recorded. Continuous wave Doppler was used as a determinant of adequacy of flow through the shunts. Transmural SMA biopsies from areas of TIVS placement were examined with electron microscopy for histopathologic injury after staining with hematoxylin and eosin and immunofluorescence using a validated histopathologic injury score (minimum-maximum score: 0-4).

RESULTS

Severity of endothelial injury was observed to be directly related to shunt indwell time. SMA transmural biopsies harvested from group D animals showed the most profound injury, demonstrating extensive EC denudations and marked intimal rupture (injury grade, 3.4 ± 0.2). Sections from group A animals revealed the mildest EC injury (1.3 ± 0.3 vs. group D p < 0.01). No significant difference was detected between group A and B. EC injury grade in group C (2.7 ± 0.6) was higher than that in group B (1.8 ± 0.6) but did not reach statistical significance (p = 0.58).

CONCLUSION

When possible, vascular reconstruction following use of shunts should include an interposition graft after debridement of the arterial edges having interfaced with the shunt. Finally, to minimize intimal injury to the native vessel, this model suggests that indwell times of shunts should be <9 hours.

Which is first: left anterior descending artery anastomosis or right coronary artery anastomosis in off-pump coronary artery bypass grafting?

OBJECTIVES

The sequence of the distal anastomosis for revascularization in off-pump coronary artery bypass grafting (OPCABG) surgery is under debate. The hypothesis in this study was that an analysis of cardiac markers would reveal that anastomosing the left anterior descending coronary artery (LAD) before the right coronary artery (RCA) would decrease myocardial damage in OPCABG surgery for 2-vessel disease.

METHODS

Forty patients with stable angina who underwent OPCABG surgery and who had LAD and RCA lesions were randomized into 2 groups of 20 patients each. The LAD was revascularized first in group 1, and the RCA was revascularized first in group 2. Cardiac troponin I, creatine kinase (CK), and CK myocardial band (CK-MB) were measured in the 2 groups before surgery and at 8, 24, and 48 hours after surgery.

RESULTS

No mortality occurred in the 2 groups. The groups were similar with respect to sex, age, durations of anastomosis of the left internal thoracic artery to the LAD and of the saphenous vein graft to the RCA, and preoperative CK, CK-MB, and troponin I levels. Postoperative CK-MB levels were significantly higher in group 2 in the eighth and 24th postoperative hours than in group 1 (P = .009 and .041, respectively). Similarly, troponin I levels were significantly higher in group 2 in the eighth, 24th, and 48th hours than in group 1 (P = .003, .003, and .006, respectively).

CONCLUSIONS

Anastomosis to the LAD first in OPCABG surgery led to a slight reduction in myocardial enzyme release against the occlusion of the target vessels during anastomoses in patients with RCA and LAD stenoses.

Influence of intracoronary shunt on myocardial damage: a prospective randomized study

OBJECTIVE

We aimed to evaluate whether surgical intracoronary shunt protects myocardium in patients with moderate left ventricular dysfunction (MLVD).

METHODS

Thirty-nine patients consisted the shunt group and 43 patients consisted the shuntless group. Troponin I, CK, and CK-MB were measured preoperatively, and at 6 and 24h postoperatively. Cardiac enzymes, rate of postoperative atrial fibrillation (AF) and third month ejection fraction (EF) were compared between the groups.

RESULTS

There were no significant differences between the groups for preoperative troponin I, CK, CK-MB, and postoperative CK levels (at 6 and 24h). Postoperative troponin I and CK-MB levels were significantly lower in the shunt group (p<0.001). Although preoperative EF of the patients were not significantly different between groups, the third month EF were significantly increased in both groups, and this increment was significantly higher in the shunt group than the shuntless group. One patient (2.3%) died in the shuntless group whereas there was no death in the shunt group.

CONCLUSION

Intracoronary shunt has protective effects on myocardium in patients with moderate left ventricular dysfunction.

Effect of intracoronary shunt on right ventricular function during off-pump grafting of dominant right coronary artery with poor collateral

Although numerous studies have validated the efficacy of intracoronary shunt on reducing left ventricular dysfunction during off-pump coronary artery bypass surgery (OPCAB), there is lack of evidence supporting its role on right ventricular (RV) function during right coronary artery (RCA) revascularization. Therefore, we studied the effect of intracoronary shunt during grafting of dominant RCA without visible collateral supply on global RV function using thermodilution method. Forty patients scheduled for multivessel OPCAB with right dominant coronary circulation without collateral supply confirmed by angiography were randomized to RCA revascularization either with a shunt (n=20) or soft snare occlusion (n=20). RV ejection fraction (RVEF) was recorded at baseline, during RCA grafting, and 15 min after reperfusion. Corresponding RV stroke work index (RVSWI) was calculated. RVEF and RVSWI decreased significantly during RCA grafting and returned to baseline values after reperfusion in both groups without any significant differences between the groups. Intracoronary shunt did not exert any beneficial effect on global RV function during RCA grafting, even in the absence of visible collateral supply. Regarding the possibility of graft failure by intracoronary shunt-induced endothelial damage, routine use of intracoronary shunt during RCA grafting is not recommended in patients with preserved biventricular function.

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.

CORONARY ARTERY SPASM AFTER OFF-PUMP CORONARY ARTERY BYPASS GRAFTING

BACKGROUND

Coronary artery spasm (CAS) in the immediate postoperative period has been recognized as a possible cause for perioperative myocardial ischaemia after off-pump coronary artery bypass grafting (CABG). It varies in severity and can be associated with circulatory collapse and death. The purpose of this study was to present our experiences on CAS after off-pump CABG and detail its management.

METHODS

The case reports of three patients with similar clinical presentations of ischaemic heart disease who underwent CABG using an off-pump technique are reviewed. Severe manifestations of CAS in the immediate postoperative period with documented angiographic findings are presented.

RESULTS

Three patients (two men and one woman) with angina pectoris were diagnosed with coronary artery disease using coronary angiography. The elective off-pump CABG was uneventful; however, severe manifestation of myocardial ischaemia with abrupt onset developed at the intensive care unit. All three patients underwent immediate coronary angiography to verify the diagnosis of CAS. Apart from intracoronary nitroglycerine infusion and medical support with inotropic agents, extracorporeal membranous oxygenation was carried out because of severe haemodynamic deterioration in one case, while support was required with intraaortic balloon pumping in another. All three patients made a full recovery.

CONCLUSION

Coronary artery spasm can severely complicate the postoperative course for patients undergoing off-pump CABG, leading to myocardial ischaemia or infarction, life-threatening arrhythmias, persistent hypotension and even cardiac arrest. Early awareness and diagnosis of CAS with the establishment of appropriate management strategies may prevent its potentially lethal consequences.

Off-pump CABG with synchronized arterial flow ensuring system

PURPOSE

We developed a synchronized, arterial-flow, ensuring system to perform coronary anastomoses safely without any ischemia-related event.

DESCRIPTION

Arterial blood is removed from the femoral artery. The resulting blood passes a switching valve and is pumped out to a syringe pump. This pump controller provides pulsatile arterial blood flow synchronized with the diastolic phase on an electrocardiogram. The arterial blood is perfused to the coronary artery through a fine flexible cannula during anastomosis.

EVALUATION

From February 1999, 524 consecutive patients were operated on using the synchronized arterial flow ensuring system. Mean duration for each anastomosis was 7.6 +/- 3.3 minutes (range, 4 to 20 min). There were no intraoperative fatal arrhythmias, ventricular arrhythmias, or short-run or hemodynamic deterioration during anastomoses. No hospital death was observed, and postoperative myocardial infarction occurred in 2 patients (0.4%). Postoperative angiography showed a 98.1% patency rate.

CONCLUSIONS

The early clinical and angiographical results for off-pump CABG with the synchronized arterial flow ensuring system were excellent without mortality. We believe that off-pump CABG can be more safely performed using the synchronized arterial flow ensuring system based on our favorable results.

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.

S2 connector versus suture: distal coronary anastomosis remodeling, patency, and function in the pig

BACKGROUND

Anastomotic connectors could be the key to less invasive bypass surgery, including endoscopic procedures, but equivalence to conventional suturing needs to be established. A novel distal coronary connector was tested pre-clinically for safety and efficacy in comparison to conventional suturing.

METHODS AND RESULTS

Left internal thoracic to left anterior descending coronary artery bypasses were constructed off-pump in 35 pigs (73+/-8 kg). An intraluminal metal connector (S2AS) was used in 21 and conventional suturing in 14 animals. S2AS anastomosis construction was easier achieved in one-fourth of the conventional construction time (3.7+/-0.7 versus 16.5+/-2.6 minutes; P<0.001). Acute patency tended to be better (P=0.15). All anastomoses were evaluated intraoperatively, and subgroups at 90 and at 180 days. Patency was 100%. An effective remodeling response was observed in all groups, resulting in unobstructed anastomoses with excellent hemodynamic performance (fractional flow reserve > or = 0.93 at 180 days). At 6 months, the noncompliant connector was covered with stabilized neointima that was thinner than found on the suture line (0.10+/-0.04 versus 0.31+/-0.13 mm; P=0.01). The connector induced less lumen loss (-0.6+/-6.5 versus 21.6+/-19%; P=0.03). The initial side-to-side configuration had remodeled to an end-to-side shape as intended.

CONCLUSIONS

In the porcine model, the connector rapidly and consistently produced high-quality anastomoses that fully met current standards on patency and function. Unconventional aspects like a noncompliant intraluminal ring and a side-to-side to end-to-side converted configuration did not interfere with favorable anastomosis remodeling. These findings shed a new light on the anatomical prerequisites for anastomosis patency.

Intracoronary Shunt-Induced Endothelial Cell Damage in Porcine Heart

BACKGROUND

Injury to and dysfunction of the endothelium can compromise the patency of coronary arteries and lead to impaired perfusion of the heart. Such injury can occur after the application of an intravascular shunt and/or a snare to a coronary artery during bypass surgery. In this study, multiphoton microscopy was used to assess the integrity of endothelium in porcine coronary arteries subjected to shunting and snaring during off-pump coronary artery bypass grafting (OPCAB).

MATERIALS AND METHODS

In open chest porcine, the left anterior descending artery was manipulated in different regions using snare and shunt to simulate OPCAB. Sections of left anterior descending artery were labeled with fluorescent dyes to evaluate the viability of the endothelium. The structural integrity of the endothelium was evaluated by calcein- and ethidium homodimer-mediated fluorescence. Endothelial functional viability was assessed by measuring cellular esterase activity, calcium mobilization, and endothelial nitric oxide synthase-mediated generation of nitric oxide using fluorescence dyes and multiphoton microscopy.

RESULTS

Substantial endothelial damage was observed in shunted region of the coronary arteries. In contrast, endothelium remained structurally viable in regions that were snared, similar to control regions of the coronary arteries that were not manipulated. Esterase activity, calcium mobilization, and nitric oxide generation was greater in the control and snared regions of the coronary arteries in comparison to the shunted region.

CONCLUSIONS

The use of intracoronary shunts led to structural damage and attenuation of endothelial function in porcine coronary arteries, whereas snared vessels maintained their viability and integrity, similar to the control sections. The routine use of shunts in OPCABG may lead to endothelial damage and possibly to long-term graft failure.

Predictors of Mid-Term Symptom Recurrence, Adverse Cardiac Events and Mortality in 591 Unselected Off-Pump Coronary Artery Bypass Graft Patients

BACKGROUND

Off-pump coronary artery bypass (OPCAB) grafting is gaining popularity; however, decreased mid-term graft patency and increased coronary reintervention rates are reported.

STUDY DESIGN

Five hundred and ninety-one consecutive unselected patients underwent OPCAB grafting from February 2000 to April 2004 (mean follow-up 38.54 +/- 0.54 months). One hundred and thirteen patients had < or =2 grafts, and four hundred and seventy-eight had > or =3 grafts. At least one radial artery graft was present in 398 patients, 328 received postoperative Clopidogrel, and 391 received postoperative statins. History of at least one percutaneous coronary intervention (PCI) was present in 192 patients.

RESULTS

Twenty-nine patients developed recurrent angina, nine had myocardial infraction, and twenty underwent coronary reintervention. Five patients died of sudden cardiac death. Overall mortality was 4.9% during follow-up (29 patients). Postoperative Clopidogrel and statins as well as intraoperative shunt use significantly decreased symptom recurrence and adverse cardiac events. Diabetes, chronic obstructive pulmonary disease, prior history of PCI, and utilization of radial artery grafts were positive predictors of symptom recurrence and adverse cardiac events. Utilization of radial artery grafts, history of PCI as well as low preoperative ejection fraction increased mortality. Number of bypass grafts, type of conduit, grafted territory, hyperlipidemia, or prior coronary artery bypass graft surgery (CABG) did not influence symptom recurrence, adverse cardiac events or mortality.

CONCLUSIONS

OPCAB grafting can be performed with low symptom recurrence, adverse cardiac events, and mortality rates. Modification of intra- and postoperative management strategies may improve outcomes.