Postoperative ST-segment elevation in coronary artery bypass surgery

Pharmacological activation of soluble guanylate cyclase improves vascular graft function

OBJECTIVES

Ischaemia-reperfusion injury impairs the nitric oxide/soluble guanylate cyclase/cyclic guanosine monophosphate (cGMP) signalling pathway and leads to vascular dysfunction. We assessed the hypothesis that the soluble guanylate cyclase activator cinaciguat would protect the vascular graft against ischaemia-reperfusion injury.

METHODS

In the treatment groups, rats (n = 8/group) were pretreated with either intravenous saline or intravenous cinaciguat (10 mg/kg) 2 h before an aortic transplant. Aortic grafts were stored for 2 h in saline and transplanted into the abdominal aorta of the recipients. Two hours after the transplant, the grafts were harvested and mounted in an organ bath. Vascular function of the grafts was investigated in the organ bath. Terminal deoxynucleotidyl transferase dUTP nick end labelling, cluster of differentiation 31, caspase-3, endothelial nitric oxide synthase, cGMP, nitrotyrosine and vascular cell adhesion molecule 1 immunochemical reactions were also investigated.

RESULTS

Pretreatment with cinaciguat significantly improved endothelium-dependent maximal relaxation 2 h after reperfusion compared with the saline group (maximal relaxation control: 96.5 ± 1%, saline: 40.4 ± 3% vs cinaciguat: 54.7 ± 2%; P < 0.05). Pretreatment with cinaciguat significantly reduced DNA fragmentation and nitro-oxidative stress; decreased the caspase-3 and vascular cell adhesion molecule 1 scores; and increased endothelial nitric oxide synthase, cGMP and cluster of differentiation 31 scores.

CONCLUSIONS

Our results demonstrated that enhancement of cGMP signalling by pharmacological activation of the soluble guanylate cyclase activator cinaciguat might represent a beneficial therapy for treating endothelial dysfunction of arterial bypass graft during cardiac surgery.

Massive coronary spasm of the native coronary system after coronary artery bypass grafting: Two patients with different outcomes

We report the cases of two patients who developed a massive spasm of the native coronary system in the immediate postoperative period, following a coronary artery bypass grafting operation with different outcomes. The first patient was hemodynamic stable and it was manifested as ischemic electrocardiographic changes in different leads (ST elevation or depression). He was treated with intracoronary and intravenous administration of nitroglycerin and calcium channel blocker and had a favorable outcome. The second patient died due to multiorgan failure and hemorrhagic shock, after the implantation of a central venoarterial extracorporeal membrane oxygenation.

Different vasoreactivity of arterial bypass grafts versus native coronary arteries in response to acetylcholine

BACKGROUND

Coronary angiography is often performed in patients with recurrent angina after successful coronary artery bypass grafting (CABG) in search of the progression of atherosclerosis. However, in many of these patients, no relevant stenosis can be detected. We speculate that coronary spasm may be associated with angina in these patients.

METHODS

From 2307 patients with unobstructed coronaries who underwent intracoronary acetylcholine spasm provocation testing (ACh-test) between 2012 and 2016, 54 consecutive patients who fulfilled the following inclusion criteria were included in this cohort study: previous left internal thoracic artery (LITA) bypass on the left anterior descending (LAD) coronary artery, ongoing/recurrent angina pectoris, no significant (< 50%) coronary artery or bypass stenosis. In all participants, the ACh-test was performed via the LITA bypass.

RESULTS

In 14 patients (26%) the ACh-test elicited epicardial spasm of the LAD distal to the anastomosis (≥ 90% diameter reduction with reproduction of the patient's symptoms and ischemic ECG shifts). Microvascular spasm (reproduction of symptoms and ischemic ECG-changes but no epicardial spasm) was seen in 30 patients (55%). The ACh-test was normal in the remaining 10 patients (19%). ACh-testing did not elicit any relevant vasoconstriction in the LITA bypasses in contrast to the LAD on quantitative coronary analyses (4.89 ± 7.36% vs. 52.43 ± 36.07%, p < 0.01).

CONCLUSION

Epicardial and microvascular coronary artery spasm are frequent findings in patients with ongoing or recurrent angina after CABG but no relevant stenosis. Vasoreactivity to acetylcholine is markedly different between LITA bypasses and native LAD arteries with vasoconstriction almost exclusively occurring in the LAD.

TiProtec preserves endothelial function in a rat model

BACKGROUND

Coronary artery bypass surgery provides excellent patency rates; however, the early and/or late graft failure reduces the long-term benefit of myocardial revascularization. We investigated the effectiveness of generally used saline, Custodiol solutions and a new solution (TiProtec) at preserving endothelium after cold ischemia and warm reperfusion injury.

MATERIALS AND METHODS

Aortic transplantations were performed in Lewis rats. Aortic arches were stored in saline, Custodiol, and TiProtec solutions for 2 h then were transplanted into the abdominal aorta. Two, 24 hours and 1 week after transplantation, the implanted grafts were harvested. Endothelium-dependent and -independent vasorelaxations were investigated in organ bath. DNA strand breaks were assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-method, messenger RNA expressions by quantitative real-time polymerase chain reaction, and the expression of CD-31 and alpha smooth muscle actin by immunochemistry.

RESULTS

Severely impaired endothelial function and integrity of implanted aortic grafts were shown after 2 h in the saline, Custodiol group (maximal vasorelaxation to acetylcholine: control: 91 ± 2%, saline: 26 ± 5%, Custodiol: 24 ± 5%, CD-31-positive area control: 96 ± 2%, saline: 35 ± 13% Custodiol: 54 ± 5%, P < 0.05, respectively); however, a preserved endothelial function was observed in the TiProtec group when compared with the saline and Custodiol group (maximal vasorelaxation: 46 ± 7%, CD-31-positive area: 54 ± 10%, P < 0.05). After 1 wk, endothelial function was partially recovered in all groups; however, it was significantly better in the TiProtec group (maximal vasorelaxation to acetylcholine: saline: 42 ± 3%, Custodiol: 48 ± 3%, TiProtec: 56 ± 3%, CD-31-positive area: saline: 56 ± 5%, Custodiol: 54 ± 4%; TiProtec: 83 ± 6%, P < 0.05, respectively). In addition, messenger RNA levels of Bax, B-cell lymphoma-2, endothelial NOS, vascular endothelial growth factor 2, and caspase-3 were significantly altered in both groups.

CONCLUSIONS

TiProtec appears to be superior for the preservation of endothelial- and smooth muscle cells of bypass graft after cold storage and warm reperfusion in our murine model.

Endothelial dysfunction of bypass graft: direct comparison of in vitro and in vivo models of ischemia-reperfusion injury

Background

Although, ischemia/reperfusion induced vascular dysfunction has been widely described, no comparative study of in vivo- and in vitro-models exist. In this study, we provide a direct comparison between models (A) ischemic storage and in-vitro reoxygenation (B) ischemic storage and in vitro reperfusion (C) ischemic storage and in-vivo reperfusion.

Methods and Results

Aortic arches from rats were stored for 2 hours in saline. Arches were then (A) in vitro reoxygenated (B) in vitro incubated in hypochlorite for 30 minutes (C) in vivo reperfused after heterotransplantation (2, 24 hours and 7 days reperfusion). Endothelium-dependent and independent vasorelaxations were assessed in organ bath. DNA strand breaks were assessed by TUNEL-method, mRNA expressions (caspase-3, bax, bcl-2, eNOS) by quantitative real-time PCR, proteins by Western blot analysis and the expression of CD-31 by immunochemistry. Endothelium-dependent maximal relaxation was drastically reduced in the in-vivo models compared to ischemic storage and in-vitro reperfusion group, and no difference showed between ischemic storage and control group. CD31-staining showed significantly lower endothelium surface ratio in-vivo, which correlated with TUNEL-positive ratio. Increased mRNA and protein levels of pro- and anti-apoptotic gens indicated a significantly higher damage in the in-vivo models.

Conclusion

Even short-period of ischemia induces severe endothelial damage (in-vivo reperfusion model). In-vitro models of ischemia-reperfusion injury can be limitedly suited for reliable investigations. Time course of endothelial stunning is also described.

The effect of nebivolol on internal mammary artery blood flow during coronary artery bypass graft surgery

Background:

During coronary artery bypass grafting (CABG), one of the most important complications related to the internal mammary artery (IMA) is perioperative spasm. Nebivolol causes endothelium-dependent vascular relaxation by increasing nitric oxide (NO) release and prevents endothelial dysfunction in long-term use. In our study, we measured the effect of a third generation beta blocker, nebivolol, on the flow dynamics of IMA grafts.

Methods:

We recruited 90 hypertensive patients undergoing isolated CABG operation, who were divided into three groups and each group included 30 patients: Group 1 patients were under antihypertensive treatment other than beta-blockers (angiontensin-converting enzyme [ACE] inhibitors, calcium channel blockers or diuretics; monotherapy or combination therapy), Group 2 received metoprolol (50 mg/day) and Group 3 received nebivolol (5 mg/day). These antihypertensive therapies were given for at least one week before the operation and continued thereafter. IMA blood flow volume was measured for one minute just before cardiopulmonary bypass (measurement A) and before left internal mammary artery (LIMA)-left anterior descending (LAD) artery anastomosis (measurement B) in the three groups. Cardiac output measurements were also achieved simultaneously.

Results:

The measurement A results were 56.3 ± 36.2, 54.6 ± 28.1 and 66.8 ± 34.2 mL/min in Groups 1, 2 and 3, respectively (p<0.05). The measurement B results were 78.3 ± 29.6, 80 ± 28.8 and 91.1 ± 40.8 mL/min in Groups 1, 2 and 3 (p<0.05), respectively. There were no differences in cardiac outputs among the groups; 5.2 ± 1.4, 5.0 ± 1.6 and 5.3 ± 1.1 L/min (p>0.05). While the cardiac outputs were similar within the three groups, the IMA free flow volume was higher in the nebivolol group after local papaverine use.

Conclusion:

Nebivolol might represent a good choice in hypertensive patients undergoing cardiac surgery by preventing perioperative myocardial hypoperfusion which increases early morbidity and mortality.

Native coronary artery and grafted artery spasm just after coronary artery bypass grafting: a case report

Native coronary artery spasm after coronary artery bypass grafting (CABG) is scarce. It frequently causes disastrous circulatory collapse. We report a 72-yr-old male, who experienced native coronary artery spasm and grafted artery spasm following CABG, which was successfully treated with coronary angiography and intracoronary injection of nitroglycerine.

Vascular changes after cardiopulmonary bypass and ischemic cardiac arrest: roles of nitric oxide synthase and cyclooxygenase

Cardiac surgery involving ischemic arrest and extracorporeal circulation is often associated with alterations in vascular reactivity and permeability due to changes in the expression and activity of isoforms of nitric oxide synthase and cyclooxygenase. These inflammatory changes may manifest as systemic hypotension, coronary spasm or contraction, myocardial failure, and dysfunction of the lungs, gut, brain and other organs. In addition, endothelial dysfunction may increase the occurrence of late cardiac events such as graft thrombosis and myocardial infarction. These vascular changes may lead to increased mortality and morbidity and markedly lengthen the time of hospitalization and cost of cardiac surgery. Developing a better understanding of the vascular changes operating through nitric oxide synthase and cyclooxygenase may improve the care and help decrease the cost of cardiovascular operations.

Endothelial cell injury in cardiovascular surgery: the pathophysiology of vasomotor dysfunction

Impaired vasomotor function has been suggested as playing a role in the pathophysiology of hypertension, diabetes, hypercholesterolemia, and atherosclerosis, all of which are common in cardiovascular surgery patients. In addition to chronic vasomotor dysfunction, alterations in vasomotor tone can result in acute arterial spasm, microcirculatory ischemia, and wide variations in systemic blood pressure. Changes in the health of the vascular endothelium may also impact the late patency of coronary artery bypass grafts, the progression of atherosclerosis in the native coronary circulation, and the long-term success of cardiac transplants. In the resting state the endothelium produces several substances that promote vascular relaxation and inhibition of platelet function, thus assuring the unhindered flow of blood through the capillaries. In response to injury, the endothelium loses some capacity to relax and also releases powerful vasoconstrictive agents. Attempting to understand the contributions that these substances play in the vasomotor dysfunction seen after cardiothoracic surgery is an area of active investigation.

Electrocardiography and postextrasystolic potentiation: utilization of the two methods to predict postrevascularization segmental myocardial function

We previously reported that postextrasystolic potentiation (PESP) is a useful predictor of changes in systolic wall function (SWF) following coronary revascularization. In the current study we analyzed ECG changes related to corresponding myocardial segments to determine their correlation with PESP and SWF. We found: (1) The PESP response in a jeopardized segment was a valid predictor of improved SWF even when Q waves, ST-segment changes, or T-wave changes were present. (2) However, when Q waves were present in two or more of the corresponding leads, positive PESP was less likely to be observed. (3) Thus Q waves in two leads predicted the least postrevascularization improvement. (4) Segments with no corresponding Q-wave postrevascularization usually improved SWF. (5) Furthermore, a continuum of responsiveness to PESP was found, ranging from T-wave changes, ST-segment changes to Q-wave changes, indicating dissociation between electrical and mechanical events. In conclusion, the ECG together with PESP provide good predictive information relative to the efficacy of revascularization. PESP is a more valuable predictive indicator. ECG alone may be of value in that the occurrence of Q waves in two or more corresponding leads predicts a low probability of improved SWF. Further studies are indicated to investigate the dissociation between electrical and mechanical events.

Nifedipine reduces the incidence of myocardial infarction and transient ischemia in patients undergoing coronary bypass grafting

A randomized study was performed on 104 patients undergoing elective coronary artery bypass grafting to examine whether the infusion of nifedipine (n = 53) reduces the incidence of perioperative myocardial ischemia and necrosis in the early postoperative period. Continuous hemodynamic and three-channel Holter monitoring was performed for 24 hours and serial assessment of serum enzymes and 12-lead electrocardiography were performed for 36 hours postoperatively. Nifedipine (minimum dose, 10 micrograms/kg/hr for 24 hours) was applied from the onset of extracorporal circulation. The control group (n = 51) received nitroglycerin (minimum dose, 1 micrograms/kg/min for 24 hours). Using the combined analyses of electrocardiography and Holter recordings, myocardial ischemia was defined as being either a transient ischemic event (TIE), transient coronary spasm (TCS), or myocardial infarction (MI). The two groups did not differ with respect to preoperative New York Heart Association classification, age, history of myocardial infarction, extracorporal circulation and aortic cross-clamp time, number of distal anastomoses, or systemic and pulmonary hemodynamics. The incidence of perioperative myocardial ischemia was substantially lower in the nifedipine than in the nitroglycerin group [TIE: three of 53 patients (6%) versus nine of 50 patients (18%), p less than 0.001; MI: two of 53 patients (4%) versus six of 50 patients (12%), p less than 0.001; and TCS: none of 53 patients (0%) versus two of 50 patients (4%), p = NS].(ABSTRACT TRUNCATED AT 250 WORDS)

Acute impairment of endothelium-dependent relaxations to aggregating platelets following reperfusion injury in canine coronary arteries

Experiments were designed to determine whether endothelial injury contributes to augmented coronary vascular tone seen during myocardial reperfusion. Canine left anterior descending coronary arteries were exposed to ischemia followed by reperfusion (60 minutes each). Rings (3-4 mm) of the reperfused artery and of normal left circumflex (control) coronary artery segments were prepared. Rings were suspended for isometric force measurement in organ chambers containing modified Krebs' Ringer bicarbonate solution (37 degrees C, 95% O2-5% CO2). Endothelium-independent contractions to KCl and prostaglandin F2 alpha were unaltered after reperfusion. Endothelium-dependent relaxations to nitric oxide, sodium nitroprusside, and isoproterenol were comparable in control and reperfused arteries. However, reperfused coronary arteries contracted with prostaglandin F2 alpha lost the ability to express endothelium-dependent relaxations to aggregating platelets. Reperfused arterial rings also exhibited impaired endothelium-dependent relaxations to acetylcholine, the calcium ionophore A23187, and the platelet-derived compounds ADP and serotonin. Quiescent (noncontracted) reperfused arterial rings exhibited larger contractions than controls when exposed to aggregating platelets. In such quiescent rings, the endothelium-dependent increase in tension to hemoglobin was unaltered after reperfusion. Thus, coronary reperfusion impairs the normal endothelium-dependent relaxations to aggregating platelets and vasoactive drugs. This impairment of platelet-mediated coronary relaxation could help explain the increased vascular tone and tendency toward vasospasm commonly observed after reperfusion of the coronary arteries.

Infusion of nifedipine after coronary artery bypass grafting decreases the incidence of early postoperative myocardial ischemia

We performed a randomized study on patients undergoing elective coronary bypass grafting to examine whether postoperative infusion of nifedipine (n = 25) could reduce the incidence of isolated transient myocardial ischemia, myocardial infarction, or both. The control group (n = 25) received nitroglycerin. Hemodynamic and Holter monitoring and serial assessment of enzymatic and electrocardiographic changes were performed for all patients. Both groups showed comparable preoperative and operative data. The incidence of myocardial infarction was significantly lower in the nifedipine group (n = 1) as compared with the control group (n = 4), whereas the number of patients with isolated transient myocardial ischemia was similar in both groups (nifedipine, 3; control, 4). At the time of peak activity, levels of creatine kinase (350 +/- 129 versus 511 +/- 287 IU/mL), creatine kinase-MB (8.4 +/- 5.4 versus 17.1 +/- 11.0 IU/mL), and glutamate-oxaloacetate-transaminase (30.4 +/- 4.4 versus 41.0 +/- 7.9 IU/mL) were markedly lower in the nifedipine group (p less than 0.05). We conclude that infusion of nifedipine after elective coronary artery bypass grafting effectively decreases the incidence of myocardial infarction and the extent of myocardial necrosis during the early postoperative period.

Coronary artery spasm following coronary artery surgery

Coronary artery spasm during the early postoperative period following cardiopulmonary bypass for coronary artery surgery can be an unrecognized cause of sudden, severe cardiopulmonary collapse. The literature regarding perioperative coronary artery spasm is reviewed, and methods of prevention, diagnosis, and treatment are suggested. Preoperative angina at rest appears to be an important identifying factor in patients who experience postoperative coronary spasm. Anatomically, the presence of a relatively normal, dominant right coronary may also indicate increased risk for early post-coronary bypass spasm. Acute hypotension is often the first sign of coronary artery spasm, and conventional treatment methods may only worsen the vasospastic reaction. Peripheral intravenous nitroglycerin infusion has often been unsuccessful treatment while intragraft or intracoronary nitroglycerin injection or administration of calcium channel-blocking drugs, or both, has proven to be effective in reversing the coronary artery spasm and ventricular dysfunction. Reluctance to use vasodilating agents must be overcome, even in the face of hypotension, when evidence of spasm is present.