|Year : 2021 | Volume
| Issue : 2 | Page : 58-61
Post CABG myocardial ischemia and infarction – A review
I Sathyamurthy1, K Jayanthi2
1 Senior Interventional Cardiologist, Apollo Main Hospitals, Chennai, Tamil Nadu, India
2 Senior Consultant – Cardiology, Formerly Apollo Hospitals, Chennai Presently SIMS Hospital, Vadapalani, Chennai, Tamil Nadu, India
|Date of Submission||10-Feb-2020|
|Date of Decision||11-May-2020|
|Date of Acceptance||18-Jun-2020|
|Date of Web Publication||03-May-2021|
Dr. I Sathyamurthy
Apollo Main Hospitals, Greams Lane Off Greams Road, Chennai - 600 026, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Coronary artery bypass graft (CABG) surgery is recommended for patients with obstructive coronary artery disease to improve survival and quality of life. Patients receive arterial and venous grafts as conduits to improve coronary circulation. There are factors that can lead to periprocedural myocardial necrosis, and there are factors resulting in late recurrent angina after CABG. In this article, an attempt has been made to review these details.
Keywords: Coronary artery bypass graft, periprocedural myocardial necrosis, late recurrent angina
|How to cite this article:|
Sathyamurthy I, Jayanthi K. Post CABG myocardial ischemia and infarction – A review. J Indian coll cardiol 2021;11:58-61
| Introduction|| |
As the population is aging, so is the case with prior coronary artery bypass graft (CABG) surgery population. A number of patients presenting with acute coronary syndromes (ACSs) are also on the rise. These patients are older, have multiple comorbidities, and often have impaired renal functions. Increased ischemia time is commonly noticed and door to balloon time of ≤90 min is often not achieved in them. Prior CABG patients with ST-elevation myocardial infarction (STEMI) are less likely to achieve successful reperfusion with lytic therapy. When they present to the emergency room quite often, graft details are not available, and electrocardiographic changes may not be definitive, often left ventricular ejection fraction (LVEF) is low. Lesion complexity and arterial access difficulties can add to this. ACS in this population can be due to saphenous vein graft (SVG), arterial graft disease, or progression of native coronary artery disease (CAD).
| Early Presentation of Symptoms Postcoronary Artery Bypass Graft|| |
Within 30 days after CABG, 10% grafts can be occluded due to endothelial damage during harvesting of the vein or arterial conduits, improper graft lengths either excessive lengths or short conduits causing tenting of coronaries, kinks in the grafts, poor quality of venous conduits, poor quality of distal target arteries, inaccessible intramyocardial course of the target vessels. Post-CABG surgery patients with the reappearance of symptoms soon after surgery are commonly due to incomplete revascularization. Other risk factors for recurrence of symptoms reported were elderly age, male sex, comorbities such as diabetes, systemic hypertension, dyslipidemia, smoking, and obesity. ASCERT study revealed that major determining factors for the reappearance of symptoms were the emergency status of surgery, shock, redo CABG surgery, insulin-dependent diabetes, current smoking, and dialysis dependence. In a study of 3000 patients from 100 high volume US hospitals, venous graft failure (VGF) was noticed in 40%–50%. In PRAGUE – 4 trial, angiographic follow-up revealed 40% of SVG s and 9% of left internal mammary artery (LIMA) grafts were occluded at 1 year.
| Intermediate Presentation|| |
1–3 years after CABG surgery pathophysiology includes platelet aggregation, intimal hyperplasia, and decreased fibrinolytic activity. Graft failure rates were reported to be up to 25% during the first 1½ years. In PREVENT IV Trial VGF was noticed in 43% of cases. Quite often, VGF can be silent. In Emory experience of the 34 patients with distal anastomotic stenosis, 25 (74%) presented within 1 year after surgery.
| Late Presentation|| |
Usually observed 3 years after CABG and it is due to neoatherosclerosis of native coronaries or grafts. VGF occurs approximately in 1% of grafts per year and gradually raises to 4%–5% per year as years pass. Post-CABG trial showed that late graft stenosis depends on the time interval after surgery, prior myocardial infarction (MI), low LVEF, male sex, current smoking, abnormal lipids, and distal run-off. Surprisingly BARI trial showed that diabetes did not affect SVG patency rates at 4 years. The use of SVG conduits for multiple anastomoses was found to be associated with significantly high rates of VGF at 1 year. Beyond 5 years, degenerated vein grafts exhibit a lot of thrombus burden, low LVEF. Azotemia was found more commonly, and this can be an added risk factor for the outcomes.
| Arterial Grafts|| |
Long-term graft patency was noted to be much higher with arterial grafts than vein grafts. Commonly LIMA grafts are used as a conduit for large vessels like a left anterior descending artery or ramus intermedius. Early arterial graft failure occurs due to surgical technique, distal vessel diameter, distal runoff, and anastomosis to a noncritical block in the target vessel. Long-term benefits from single arterial grafts led to the practice of multiple arterial grafts such as bilateral IMAs, radial artery conduits, and gastroepiploic artery leading to the practice of total arterial revascularization. In randomized trials, it was shown that radial artery conduits had much higher angiographic patency rates compared to SVGs.,
| Off Pump versus On Pump Coronary Artery Bypass Graft Surgery|| |
Available literature revealed disadvantages of off-Pump CABG surgery compared to On Pump CABG as regards SVG patency rates; however, no deleterious effect was observed on arterial graft patency. Recently published 5 years outcomes regarding On-pump versus Off-pump CABG surgery revealed that 1104 patients who underwent off-pump CABG when compared to 1099 onpump, STEMI was observed in 12.1% versus 9.6%, respectively (P = 0.05). In the veteran's affairs, randomized on- versus off-pump CABG showed that 23% of SVGs and 11% of IMA grafts failed in the Off-pump group. Presently, many centers are adopting off-pump CABG, and this may result in an increased number of postoperative graft failures.
| Presentation|| |
Prior CABG patients can present with chronic stable angina or ACS.
Acute coronary syndromes
Three percent of cases with prior CABG develop STEMI per year. STEMI was classified as type 5 MI as per universal definition. Welsh et al. reported an incidence of STEMI in 2%–14% of cases with prior CABG surgery, and these were associated with the worst outcomes.,,,, National Cardiovascular Registry Data showed that, of the 15,628 patients who have undergone primary percutaneous coronary intervention (PCI), only 6% had prior CABG surgery. In PAMI – 2 trial of 1100 patients with prior CABG surgery, only 5.3% had STEMI. In the National Registry of MI – 2 observational database of 45,925 STEMI patients, 6351 were treated with primary PCI, of which 375 (5.9%) had a history of prior CABG. This shows that STEMI is less common in post-CABG subset.
In most of the primary PCI trials, patients with prior CABG were excluded, and no concrete guidelines were available. The line of therapy has to be decided on an individual basis depending upon the graft status, renal parameters, LV function, etc., Lytic therapy has shown poor success rates in this subset of patients., When the presentation of ACS was very late after CABG surgery, the reperfusion rates were low due to diffusely diseased venous grafts with thrombus burden with less number of patients achieving TIMI III flow. Rafid et al. showed that reperfusion rates after lytic therapy were much lower in those with prior CABG compared to those without (8.8% vs. 29.2%, P = 0.001).
Percutaneous coronary interventions in postcoronary artery bypass graft acute coronary syndromes
When SVG was the culprit vessel, primary PCI results were inferior to those of native vessels. Brodie et al. showed in 2240 consecutive patients with post-CABG STEMI, those who underwent PCI to SVG were sicker with poor LV function, and most of them had three-vessel CAD, compared to those who underwent native vessel PCI. Patients with SVG interventions had lower rates of TIMI grades, higher in-hospital mortality, and worse 10 years survival, and angiographic SVG patency rate was only 64% at 1 year. Similar outcomes were reported by others.,, Primary PCI is currently a Class I indication if it can be done in a timely manner.,, During PCI in the early postoperative period, caution should be exercised to prevent suture line perforations by the guide wires. Sometimes, it may not be possible to identify the culprit's vessel.
Saphenous vein graft interventions
The progression of disease in SVG s is much rapid, and stenting has got better long-term outcomes than medical treatment., Primary PCI in SVG's carries higher mortality and poor long-term outcomes.,, If feasible native vessel intervention is always preferable, even in CTOs, as many centers are routinely performing them. Beyond 3 years CABG, there is usually a large thrombus burden and risk of distal embolization with poor long-term outcomes. There are no reports on added benefits of fractional flow reserve in SVGs.
Internal mammary artery graft interventions
When symptoms occur within 1 year, it is usually due to surgical technique, and the stenosis is usually at the distal anastomotic site. Shaft lesions are rare and occur very late after surgery. In one study of 174 LIMA interventions, 63% were at the distal anastomotic site, and the procedural success was 97% with target vessel revascularization of 7% at 1 year. Complications like spasm, dissection have been reported. There are no large scale studies and long-term outcome data available regarding IMA graft PCI.
Grafts versus native coronary percutaneous coronary intervention
In APEX AMI TRIAL, of the 128 patients with prior CABG surgery, in63 (41%) SVG was the culprit vessel. After PCI, 90 days mortality was 19%, which was significantly higher compared to native vessel PCI. Gaglia et al. in their series of 192 patients, 30-day mortality was 14.3% for SVG interventions compared to 8.4% for native vessel PCI. Kohl et al. had 249 patients of ACS among 3542 who had prior CABG surgery. Culprit vessel was SVG in 34%, the native vessel was 42%, and no culprit could be identified in 24% of cases. This confirms that native vessel PCI is always preferable to SVGs wherever possible.
Percutaneous coronary intervention versus redo coronary artery bypass graft surgery
In Emory University Series during 14 years, 2613 patients underwent PCI and 1561 undergone redo CABG surgery. PCI showed better results as regards to mortality, the occurrence of stroke, cost of the procedure, and average length of stay. Ten-year survival was better in the PCI group compared to redo CABG patients, and survival curves were observed to be better in native vessel PCI compared to SVG's. However, these observations were not confirmed by the Mayo clinic study. In Cleveland clinic series, 1497 patients with prior CABG have undergone reoperation, and 704 underwent PCI. When complete revascularization was achieved, initial outcomes were favorable for PCI as regards 30 days mortality, periprocedural Q-wave infarcts, and strokes, but at 5 years redo CABG surgery showed better survival. The only randomized trial by Morrison et al. compared PCI (67 patients) with redo CABG (75 patients) in prior CABG cases and concluded that there was no advantage of one procedure over the other, and it should be decided on a case to case basis.
| Conclusions|| |
ACS patients with prior CABG are a high-risk population. The presentation as STEMI is uncommon. Response to lytic therapy is poor, and door to balloon times of ≤90 min is rarely achieved. It is always preferable to consider native coronary PCI wherever possible. Poor long-term outcomes noted in SVG interventions. As the CABG population is increasing, the number of PCIs in this subset is also on the rise, and one must be geared to combat this challenge.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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