The choice of strategy for percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI) is crucial. The key is to open the infarct-related artery as early as possible and as soon as possible to maximize the salvage of the dying myocardium. To synthesize the US 2009 guidelines for ST-segment elevation myocardial infarction and the 2008 ESC guidelines for PCI and the 2009 Chinese guidelines for PCI and the 2010 ESC guidelines for cardiac revascularization for emergency PCI for acute ST-segment elevation myocardial infarction (STEMI).
Emergency PCI: The 2007 and 2009 ACC/AHA/SCAI and 2010 ESC Cardiac Revascularization Guidelines on Acute ST-segment elevation myocardial infarction (STEMI) recommend that it is important to make every effort to minimize time delays, especially in patients within 2 hours of the onset of illness.
For STEMI patients seen in a hospital with PCI, direct PCI should be the preferred strategy (Class I/A), requiring a time between presentation and balloon dilation (door-balloon) of <90 min; for STEMI patients seen in a hospital without PCI, if the time delay is less than 120 min from patient presentation to completion of PCI balloon dilation, do not thrombolyze, but Immediately transport the patient to a hospital or emergency center with 24-hour access to emergency PCI.
Patients younger than 75 years with recent anterior wall myocardial infarction with a time delay greater than 2 hours or greater than 90 min should receive thrombolysis (Class I/B) within 30 min of presentation, unless contraindicated, and then be transferred to a hospital with PCI availability and should undergo angiography and PCI between 3 and 24 hours. Patients seen after should be transferred immediately to a facility equipped for emergency PCI. Low-risk patients should also be considered for transfer after thrombolysis, especially those with persistent symptoms and suspected thrombolysis failure.
The concepts of easy PCI and remedial PCI are now no longer advocated. If a high-risk STEMI patient is seen in a hospital where direct PCI is not feasible, the patient can be transferred to a hospital where PCI is feasible or to a hospital with experienced interventionalists who can provide local resuscitation, including interventional equipment, as soon as possible while thrombolysis or antithrombotic therapy is performed. Emergency PCI is required immediately after failure of thrombolysis. easy PCI is a treatment strategy to improve the coronary opening rate in STEMI patients by giving thrombolytic drugs and/or GP IIb/IIIa receptor antagonists prior to the proposed direct PCI.
The 2007 ACC/AHA/SCAI STEMI guidelines recommend an easy PCI strategy (Class IIb/C) for high-risk STEMI patients with low bleeding risk who cannot undergo immediate PCI. The TRANSFER-AMI study randomized 1,030 high-risk STEMI patients after thrombolysis into a transfer PCI group (who were transferred to PCI regardless of successful thrombolysis) and a conservative treatment group (who underwent remedial PCI if thrombolysis failed).
The results showed that the composite endpoint of 30-day death, recurrent myocardial infarction, heart failure, recurrent angina, or shock was significantly lower in the transfer PCI group than in the conservative treatment group (10.6% vs. 16.6%, P=0.0013). the same conclusion was obtained at 1-year follow-up of the CARESS-AMI study presented at the ESC meeting in 2008. the CARESS-AMI study is a randomized controlled trial conducted in Europe (Italy, Poland and France) comparing immediate post-thrombolytic transfer PCI with conservative treatment after thrombolysis.
Six hundred patients with STEMI treated with half doses of thrombolytic drugs (ralteplase), aspirin, heparin, and abciximab were randomized to transfer PCI (299 patients) and conservative treatment (301 patients), where transfer PCI was performed if there was persistent ST-segment elevation, chest pain, or hemodynamic instability after 90 min of thrombolysis in the conservative treatment group (finally, 35.7% of patients in the conservative treatment group). 35.7% of the patients underwent transport PCI).
The 1-year follow-up showed a trend toward lower rates of the composite endpoint events of death, recurrent myocardial infarction, hospitalization for heart failure, stroke, and intractable angina in the transport PCI group compared with the conservative treatment group (12.1% versus 17.3%; P=0.08); if target vessel revascularization (TVR) was added to the composite events, the rate of the composite endpoint events was significantly lower in the transport PCI group than in the conservative treatment group (21.1% versus 17.3%; P=0.08). conservative treatment group (21.1% versus 49.0%; P<0.000001).
It has been suggested that, unlike the ASSENT-4 and FINESSE studies, which evaluated the advantages and disadvantages of easy PCI versus direct PCI, the TRANSFER-AMI and CARESS-AMI studies did not have a direct PCI group and their results only showed a clear benefit of early transfer PCI in STEMI patients receiving thrombolytic therapy for any reason. Therefore, the 2008 ESC guidelines for PCI recommend routine coronary angiography and PCI (with or without angina/myocardial ischemia, I/A) within 24 h of successful thrombolysis, a strategy that significantly reduces the rate of reinfarction after successful thrombolysis.
Emergency PCI: drug-eluting stent (DES) or bare stent (BMS)? There is no doubt that DES significantly reduces restenosis and re-PCI rates compared to BMS, and the publication of the results of the 2008 ACC Massachusetts study provides compelling evidence for the use of DES in emergency PCI in patients with AMI. The study retrospectively analyzed data from AMI patients at non-federally owned hospitals in Massachusetts between April 2003 and September 2004 and divided the patients into DES and BMS groups based on their PCI data (excluding patients with both stents), with the final 5258 patients completing the 2-year follow-up.
The results showed a significantly lower TVR rate in the DES group compared to the BMS group, without an increase in the rate of recurrent myocardial infarction or mortality. the HORIZONS-AMI study, reported at the 2008 TCT meeting, is the largest randomized controlled trial comparing the advantages and disadvantages of DES versus BMS in patients with STEMI. Three hundred and sixty-six STEMI patients were enrolled and randomized in a 3:1 ratio to the DES group (Taxus stent) and the BMS group (Express stent).
The 1-year follow-up showed that the TVR rate (4.5% versus 7.5%, P=0.002) and restenosis rate (10.0% versus 22.9%, P<0.0001) were significantly lower in the DES group than in the BMS group, while the incidence of MACE (8.1% versus 8.0%) and in-stent thrombosis (3.1% versus 3.4%) was similar in both groups. Although the results of the Massachusetts study and the HORIZONS-AMI study have shown the advantages of DES application in AMI patients, interventionalists should fully evaluate the benefits and risks of DES and apply it selectively.
Attention should be paid to the standardized operation during DES implantation to reduce the occurrence of increased in-stent thrombosis due to poor stent apposition, and to focus on dual antiplatelet therapy.
In addition, in response to the shortcomings of DES that excessively inhibit endothelial repair and increase thrombosis, various new stents that promote endothelial healing have been applied in clinical practice, including endothelial progenitor cell capture stents (EPC capture stents), biodegradable stents and Conor stents with double-sided laser microporous technology, etc. EPC capture stents are coated with antibodies that can capture endothelial progenitor cells in their own circulation to promote endothelial healing and prevent thrombosis. The EPC capture stent is coated with antibodies that can capture endothelial progenitor cells in the circulation, promote endothelial healing, prevent thrombosis and reduce restenosis.
A clinical study on the use of EPC capture stents in STEMI patients undergoing direct PCI was reported at the 2008 TCT meeting. The results of the 1-year follow-up showed that the incidence of in-stent thrombosis, MACE, recurrent myocardial infarction, TVR, and mortality were 0.9%, 13.1%, 3.7%, 5%, and 7.5%, respectively, suggesting that EPC capture stents have a good clinical prognosis and The need for dual antiplatelet therapy is shorter, especially for patients who cannot tolerate long-term dual antiplatelet therapy.
The persistence of DES polymer carriers is one of the main causes of late in-stent thrombosis. the BIOMATRIX stent is a new DES coated with a biodegradable polymer (polylactic acid) and the drug Biolimus A9, a derivative of rapamycin. the 2008 ESC meeting reported that the 9-month follow-up results of the LEADERS study showed that the BIOMATRIX There was no significant difference in the incidence of the primary endpoint events of cardiac death, recurrent myocardial infarction, and TVR between the stent group and the CYPHER stent group, and the ability of the BIOMATRIX stent to reduce the incidence of late late thrombosis remains to be seen at further follow-up.
The TAPAS study reported at the 2008 EuroPCR meeting was the first study to demonstrate that thrombus aspiration significantly improves myocardial perfusion and prognosis in patients with STEMI. randomized controlled study. A total of 1071 STEMI patients with onset <12 h were randomized to the thrombus aspiration group (535 patients) and the PCI-only group (536 patients) before coronary angiography.
There was no significant difference in the baseline data (including clinical and imaging characteristics) between the two groups. The results showed that thrombus aspiration was successfully completed in nearly 90% of cases in the thrombus aspiration group, with no thrombus aspiration-related complications.
Compared with the thrombus aspiration group alone, patients in the thrombus aspiration group had significantly improved myocardial perfusion after PCI, significantly lower rates of myocardial blush grade 0 and 1 (17% versus 26%, P<0.001), and significantly higher rates of complete ST-segment regression (STR) on ECG (57% versus 44%, P<0.001); at 1 year follow-up, compared with the thrombus aspiration group alone, the all-cause Mortality (4.7% versus 7.6%, P=0.042) and cardiac mortality (3.6% versus 6.7%, P=0.02) were significantly lower in the thrombus aspiration group compared with the PCI-only group, and there was a trend toward a lower rate of recurrent myocardial infarction (2.2% versus 4.3%, P=0.05).
The TAPAS study suggests to us that thrombus aspiration followed by PCI significantly improves myocardial perfusion and reduces mortality in STEMI patients regardless of baseline status (thrombus-rich or not). In STEMI patients, especially those with coronary angiography suggestive of a “criminal lesion” rich in thrombus (e.g., truncated occluded segment, thrombus >5 mm in length at the occlusion site, floating thrombus with persistent contrast retention distal to the lesion or incomplete occlusion with accumulation of thrombus more than three times the diameter of the reference vessel, etc.), thrombus must be aspirated first with a thrombus The thrombus must be extracted with an aspiration catheter before balloon dilation and/or stenting.
The thrombectomy catheter is usually large (e.g., Diver catheter 4.7F OD), and if the “offender lesion” itself or its proximal end has a severe stenosis, it is often difficult for the thrombectomy catheter to pass through the lesion and complete thrombus aspiration. It is recommended to pre-dilate with a small balloon at low pressure before using a thrombus aspiration catheter to remove the thrombus. Direct pre-dilation with larger balloons or higher pressures may cause massive thrombus dislodgement and embolization of the distal vascular bed, resulting in no recurrent flow.
It has been reported that 68% of AMI patients have “criminal lesions” with less than 50% stenosis. After thrombus aspiration of such lesions, direct stenting is used to save costs and avoid repeated balloon pre-dilatation that can cause thrombus and plaque debris to dislodge, resulting in slow and no flow.
The following points should be noted when using thrombus aspiration catheter for thrombus aspiration.
①, negative pressure suction should be started when the head end of the suction catheter is close to the occluded segment;
②. Thrombus aspiration should be performed not only in the occluded segment, but also in the distal segment of the vessel;
③, thrombus aspiration should be patient enough, repeatedly and carefully aspirated, and the effect of thrombus aspiration in the “criminal vessel” can be checked by intermittent imaging;
④, thrombus aspiration process, such as stopping the return of blood or slow return of blood, often indicates that there may be a large thrombus obstruction suction catheter, need to withdraw the catheter under negative pressure, heparin saline flushing and then thrombus aspiration;
⑤. When withdrawing the suction catheter, the negative pressure should be maintained to avoid the dislodgement of the thrombus in the suction catheter to the proximal end of the occluded vascular segment, which may even cause other vascular embolism;
⑥.After withdrawing the suction catheter, the blood in the guide catheter should be sucked back (sometimes small bubbles or thrombus will be sucked back) to avoid possible gas or thromboembolism;
(7) After thrombus aspiration, nitroglycerin needs to be injected into the coronary artery to relieve vasospasm.
Not all emergency PCI cases are suitable for and benefit from thrombus aspiration. Preoperative assessment of the thrombus load of the “criminal lesion” should be based on the coronary angiography results. If the “offender lesion” is an occlusion based on a chronic high stenosis with minimal thrombus load, thrombus aspiration is not necessary and the thrombus aspiration catheter is difficult to pass through such a lesion.
The TAPAS study showed that 54 of the STEMI patients in the thrombus aspiration group were converted to PCI alone, so an adequate assessment of the lesion characteristics, such as thrombus load and stenosis, of the “offender vessel” in AMI patients after angiography, before deciding whether to perform thrombus aspiration strategy, would provide greater benefit to AMI patients and improve the success of the procedure. The Proxis system is a recently developed technology that can be used to improve the efficiency of the procedure.
The Proxis System is a recently developed proximal blocking thrombus protection device that works by expanding a balloon proximal to the lesion to close off the flow, then aspirating the thrombus or other broken plaque after the PCI operation is completed, and then aspirating the balloon to restore antegrade flow. The results of the study. 284 STEMI patients with onset <6 hours were randomized to direct PCI combined with the Proxis system (141 patients) and direct PCI alone (143 patients).
The results showed that the study’s primary endpoint of complete STR rate (immediate STR rate: 66% vs. 50%, P=0.009; 30 min STR rate: 75% vs. 66%, P=0.17; 60 min STR rate: 80% vs. 72%, P=0.14) and secondary endpoint of TIMI class 3 flow rate (93% vs. 87%, P=0.06) were significantly higher in the proximal protection device group than in the control group. significantly higher than in the control group, while there was also a trend toward lower rates of composite endpoint events including death, infarction, stroke, TVR and major adverse cardiovascular and cerebrovascular events (MACCE) (4% vs. 7%).
The PREPARE study demonstrated that placement of the Proxis system in STEMI patients is safe and feasible to effectively capture thrombotic debris within the diseased vessel and achieve better microcirculatory perfusion. Limitations of the study include the inappropriateness of the Proxis system for proximal coronary lesions and the relatively small sample size of the study.
The new definition of elective PCI refers to angiography and, if necessary, PCI within 3-24 h after thrombolytic therapy, with the aim of timely lysis of thrombus, fastest opening of the coronary artery, improvement of left ventricular remodeling, improvement of blood flow to the dormant or hibernating myocardium, prevention of infarct expansion and extension, and reduction of infarct size. Recent findings and a recent meta-analysis suggest that the benefit of PCI within 24 hours of thrombolysis is greater than that of thrombolysis alone, with no increased risk. The optimal time window for PCI after thrombolytic therapy should be 2-24 h after thrombolysis, preferably about 6 h after thrombolysis.