Coronary No-Reflow after Primary Percutaneous Coronary Intervention-Current Knowledge on Pathophysiology, Diagnosis, Clinical Impact and Therapy

Coronary no-reflow (CNR) is a frequent phenomenon that develops in patients with ST-segment elevation myocardial infarction (STEMI) following reperfusion therapy. CNR is highly dynamic, develops gradually (over hours) and persists for days to weeks after reperfusion. Microvascular obstruction (MVO) developing as a consequence of myocardial ischemia, distal embolization and reperfusion-related injury is the main pathophysiological mechanism of CNR. The frequency of CNR or MVO after primary PCI differs widely depending on the sensitivity of the tools used for diagnosis and timing of examination. Coronary angiography is readily available and most convenient to diagnose CNR but it is highly conservative and underestimates the true frequency of CNR. Cardiac magnetic resonance (CMR) imaging is the most sensitive method to diagnose MVO and CNR that provides information on the presence, localization and extent of MVO. CMR imaging detects intramyocardial hemorrhage and accurately estimates the infarct size. MVO and CNR markedly negate the benefits of reperfusion therapy and contribute to poor clinical outcomes including adverse remodeling of left ventricle, worsening or new congestive heart failure and reduced survival. Despite extensive research and the use of therapies that target almost all known pathophysiological mechanisms of CNR, no therapy has been found that prevents or reverses CNR and provides consistent clinical benefit in patients with STEMI undergoing reperfusion. Currently, the prevention or alleviation of MVO and CNR remain unmet goals in the therapy of STEMI that continue to be under intense research.

Angiographic outcome in patients treated with deferred stenting after ST-segment elevation myocardial infarction-results from DANAMI-3-DEFER

AIMS

Stent implantation during primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI) occasionally results in flow disturbances and distal embolization, which may cause adverse clinical outcomes. Deferred stent implantation seems to reduce the impairment on myocardial function, although the mechanisms have not been clarified. We sought to evaluate whether deferred stenting could reduce flow disturbance in patients treated with primary PCI.

METHODS AND RESULTS

Patients with STEMI included in the DANAMI-3-DEFER trial were randomized to deferred versus immediate stent implantation. The primary and secondary outcomes of this substudy were the incidences of slow/no reflow and distal embolization. A total of 1205 patients were included. Deferred stenting (n = 594) resulted in lower incidences of distal embolization [odds ratio (OR) 0.67, 95% confidence interval (CI) 0.46-0.98, P = 0.040] and slow/no reflow (OR 0.60, 95%CI 0.37-0.97, P = 0.039). In high-risk subgroups, the protective effect was greatest in patients >65 years of age (slow/no reflow: OR 0.36, 95% CI 0.17-0.72, P = 0.004 and distal embolization: OR 0.34, 95% CI 0.18-0.63, P = 0.001), in patients presenting with occluded culprit artery at admission (slow/no reflow: OR 0.33, 95% CI 0.16-0.65, P = 0.001 and distal embolization: OR 0.54, 95% CI 0.31-0.96, P = 0.036) and in patients with thrombus grade >3 (slow/no reflow: OR 0.37, 95% CI 0.20-0.67, P = 0.001 and distal embolization: OR 0.39, 95% CI 0.24-0.64, P < 0.001) with a significant P for interaction for all.

CONCLUSION

Deferred stent implantation reduces the incidences of slow/no reflow and distal embolization, especially in older patients and in those with total coronary occlusion or high level of thrombus burden.

Intracoronary artery retrograde thrombolysis combined with percutaneous coronary interventions for ST-segment elevation myocardial infarction complicated with diabetes mellitus: A case report and literature review

Background

The management of a large thrombus burden in patients with acute myocardial infarction and diabetes is still a worldwide problem.

Case presentation

A 74-year-old Chinese woman presented with ST-segment elevation myocardial infarction (STEMI) complicated with diabetes mellitus and hypertension. Angiography revealed massive thrombus formation in the mid-segment of the right coronary artery leading to vascular occlusion. The sheared balloon was placed far from the occlusion segment and urokinase (100,000 u) was administered for intracoronary artery retrograde thrombolysis, and thrombolysis in myocardial infarction (TIMI) grade 3 blood flow was restored within 7 min. At last, one stent was accurately implanted into the culprit’s vessel. No-reflow, coronary slow flow, and reperfusion arrhythmia were not observed during this process.

Conclusion

Intracoronary artery retrograde thrombolysis (ICART) can be effectively and safely used in patients with STEMI along with diabetes mellitus and hypertension, even if the myocardial infarction exceeds 12 h (REST or named ICART ClinicalTrials.gov number, ChiCTR1900023849).

New Interventional Therapies beyond Stenting to Treat ST-Segment Elevation Acute Myocardial Infarction

Myocardial infarction remains the principal cause of death in Europe. In patients with ST-segment-elevation myocardial infarction (STEMI), a promptly revascularization with primary percutaneous intervention (PCI) has transformed prognosis in the last decades. However, despite increasing successful PCI procedures, mortality has remained unchanged in recent years. Also, due to an unsatisfactory reperfusion, some patients have significant myocardial damage and suffer left ventricular adverse remodeling with reduced function—all that resulting in the onset of heart failure with all its inherent clinical and socioeconomic burden. As a consequence of longer ischemic times, distal thrombotic embolization, ischemia-reperfusion injury and microvascular dysfunction, the resultant myocardial infarct size is the major prognostic determinant in STEMI patients. The improved understanding of all the pathophysiology underlying these events has derived to the development of several novel therapies aiming to reduce infarct size and to improve clinical outcomes in these patients. In this article, based on the mechanisms involved in myocardial infarction prognosis, we review the new interventional strategies beyond stenting that may solve the suboptimal results that STEMI patients still experience.

Aspiration Thrombectomy in Patients with Acute Myocardial Infarction-5-Year Analysis Based on a Large National Registry (ORPKI)

Blood flow restoration after primary percutaneous coronary intervention (pPCI) in patients with acute myocardial infarction (AMI) may not always be achieved and could be complicated by the no-reflow phenomenon (NRP). The aim of the current study was to assess the frequency of thrombus aspirations (TAs) and NRPs in patients with AMI and treated with pPCI based on the data collected during a 5-year period in the national ORPKI registry, as well as the frequency of periprocedural strokes and predictors of TA and NRP. This retrospective analysis was performed on prospectively collected data gathered in the Polish National Registry of Percutaneous Coronary Interventions (ORPKI), which covered the period between January 2014 and December 2018, and included 200,991 patients treated due to AMI out of 535,857 patients treated using PCI. Among them, 16,777 patients underwent TA. TA was mainly used in the STEMI subgroup of 14,207 patients (84.8%). The frequency of NRP among AMI patients in the thrombectomy group was 2.75% and in the non-thrombectomy group 0.82%. Predictors of TA and NRP were also assessed using multivariate analysis. The percentage of patients treated with pPCI and with PCI alone increased significantly in all of the three selected groups of patients from 88.7% to 94.3% in the AMI group (p < 0.001), from 82.3% to 90.3% in the STEMI subgroup (p < 0.001), and from 96.3% to 98.2% in the NSTEMI subgroup (p < 0.001) during the analysed period. NRP occurred more often in the thrombectomy group for the NSTEMI (0.58% vs. 3.07%, p < 0.05) and STEMI (1.06% vs. 2.69%, p < 0.05) subgroups. Periprocedural stroke occurred more often in the thrombectomy group in comparison to the non-thrombectomy group with AMI (0.03% vs. 0.01%, p < 0.05) and the NSTEMI (0.16% vs. 0.02%, p < 0.05). In conclusion, the frequency of TA has been experiencing a steady decline in recent years, regardless of AMI type, among patients treated with pPCI.

Mechanical and Pharmacological Revascularization Strategies for Prevention of Microvascular Dysfunction in ST-Segment Elevation Myocardial Infarction: Analysis from Index of Microcirculatory Resistance Registry Data

Objectives

We aimed to identify mechanical and pharmacological revascularization strategies correlated with the index of microcirculatory resistance (IMR) in ST-elevation myocardial infarction (STEMI) patients.

Background

Microvascular dysfunction (MVD) after STEMI is correlated with infarct size and poor long-term prognosis, and the IMR is a useful analytical method for the quantitative assessment of MVD. However, therapeutic strategies that can reliably reduce MVD remain uncertain.

Methods

Patients with STEMI who underwent primary percutaneous coronary intervention (PCI) were enrolled. The IMR was measured with a pressure sensor/thermistor-tipped guidewire immediately after primary PCI. High IMR was defined as values ≥66^th percentile of IMR in enrolled patients (IMR > 30.9 IU).

Results

A total of 160 STEMI patients were analyzed (high IMR = 54 patients). Clinical factors for Killip class (P=0.006), delayed hospitalization from symptom onset (P=0.004), peak troponin-I level (P=0.042), and multivessel disease (P=0.003) were associated with high IMR. Achieving final thrombolysis in myocardial infarction myocardial perfusion grade 3 tended to be associated with low IMR (P=0.119), whereas the presence of distal embolization was significantly associated with high IMR (P=0.034). In terms of therapeutic strategies that involved adjusting clinical and angiographic factors associated with IMR, preloading of third-generation P2Y12 inhibitors correlated with reducing IMR value (β = −10.30, P < 0.001). Mechanical therapeutic strategies including stent diameter/length, preballoon dilatation, direct stenting, and thrombectomy were not associated with low IMR value (all P > 0.05), and postballoon dilatation was associated with high IMR (β = 8.30, P=0.020).

Conclusions

In our study, mechanical strategies were suboptimal in achieving myocardial salvage. Preloading of third-generation P2Y12 inhibitors revealed decreased IMR value, indicative of MVD prevention.

Optimal strategy of primary percutaneous coronary intervention for acute myocardial infarction due to unprotected left main coronary artery occlusion (OPTIMAL): study protocol for a randomised controlled trial

BACKGROUND

Primary percutaneous coronary intervention (PCI) for patients presenting with acute myocardial infarction (AMI) caused by left main coronary artery occlusion is associated with significantly higher mortality and risks of major adverse cardiovascular events. Deferred stent implantation may improve prognosis of primary PCI by reducing distal embolization and no-reflow phenomenon. There is no randomized clinical trial focusing on the effect and outcome of deferred stent implantation on primary PCI for left main coronary artery occlusion in contrast with conventional strategy.

METHODS

The Optimal Strategy of Primary Percutaneous Coronary Intervention for Acute Myocardial Infarction due to Unprotected Left Main Coronary Artery Occlusion (OPTIMAL) study (ClinicalTrials.gov Identifier: NCT03282773) is an open-label, randomized, multicenter clinical trial in which 480 patients presenting with AMI caused by left main coronary artery occlusion recruited from 30 hospitals in mainland China will be randomly assigned 1:1 to immediate stenting or deferred stenting (scheduled 4-10 days after primary angioplasty) groups. The primary endpoint is a composite of all-cause mortality or recurrent myocardial infarction at 30 days after randomization. The secondary outcomes include all-cause mortality, cardiac death, recurrent myocardial infarction, and unplanned target vessel revascularization at 30 days, 6 months, and 12 months.

DISCUSSION

The OPTIMAL study is designed to compare the clinical performance of deferred stenting with that of immediate stenting for AMI caused by left main coronary artery occlusion.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03282773 . Registered on 10 September 2017.

Mechanical strategies to enhance myocardial salvage during primary percutaneous coronary intervention in patients with STEMI

Primary percutaneous coronary intervention (PPCI) has become the mainstay of reperfusion therapy in patients with ST-segment elevation myocardial infarction (STEMI). Despite timely reperfusion by PPCI and restoration of epicardial blood flow in up to 95% of patients, tissue reperfusion remains suboptimal in a sizeable proportion of patients with STEMI. Over the years mechanical and pharmacological strategies to enhance myocardial salvage during PPCI have been developed and used in patients with STEMI. The most common mechanical strategies used in the setting of PPCI include: coronary stenting, direct stenting, mesh-covered stents, self-expanding stents, deferred stenting, thrombectomy, distal protection devices, intra-aortic balloon pumping, left ventricular assist devices and ischaemic conditioning. These strategies are thought to enhance myocardial salvage via improving acute procedural success, attenuation of distal embolisation, microvascular obstruction and reperfusion injury, and providing haemodynamic support. Coronary (direct) stenting is almost the default approach of reperfusion during PPCI procedures. Evidence on the use of mesh-covered stents, self-expanding stents, deferred stenting or left ventricular assist devices is scant and their use in the setting of PPCI remains limited. Mechanical thrombectomy, distal protection devices or routine intra-aortic balloon counterpulsation seem to offer no clinical benefit when used in the setting of PPCI. Although manual aspiration may improve indices of tissue reperfusion, recent research showed no clinical benefit of routine use of this strategy in patients with STEMI undergoing PPCI. Ischaemic conditioning, although promising, remains at an investigational stage and needs further research.

Deferred versus conventional stent implantation in patients with ST-segment elevation myocardial infarction (DANAMI 3-DEFER): an open-label, randomised controlled trial

BACKGROUND

Despite successful treatment of the culprit artery lesion by primary percutaneous coronary intervention (PCI) with stent implantation, thrombotic embolisation occurs in some cases, which impairs the prognosis of patients with ST-segment elevation myocardial infarction (STEMI). We aimed to assess the clinical outcomes of deferred stent implantation versus standard PCI in patients with STEMI.

METHODS

We did this open-label, randomised controlled trial at four primary PCI centres in Denmark. Eligible patients (aged >18 years) had acute onset symptoms lasting 12 h or less, and ST-segment elevation of 0·1 mV or more in at least two or more contiguous electrocardiographic leads or newly developed left bundle branch block. Patients were randomly assigned (1:1), via an electronic web-based system with permuted block sizes of two to six, to receive either standard primary PCI with immediate stent implantation or deferred stent implantation 48 h after the index procedure if a stabilised flow could be obtained in the infarct-related artery. The primary endpoint was a composite of all-cause mortality, hospital admission for heart failure, recurrent infarction, and any unplanned revascularisation of the target vessel within 2 years' follow-up. Patients, investigators, and treating clinicians were not masked to treatment allocation. We did analysis by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01435408.

FINDINGS

Between March 1, 2011, and Feb 28, 2014, we randomly assigned 1215 patients to receive either standard PCI (n=612) or deferred stent implantation (n=603). Median follow-up time was 42 months (IQR 33-49). Events comprising the primary endpoint occurred in 109 (18%) patients who had standard PCI and in 105 (17%) patients who had deferred stent implantation (hazard ratio 0·99, 95% CI 0·76-1·29; p=0·92). Procedure-related myocardial infarction, bleeding requiring transfusion or surgery, contrast-induced nephopathy, or stroke occurred in 28 (5%) patients in the conventional PCI group versus 27 (4%) patients in the deferred stent implantation group, with no significant differences between groups.

INTERPRETATION

In patients with STEMI, routine deferred stent implantation did not reduce the occurrence of death, heart failure, myocardial infarction, or repeat revascularisation compared with conventional PCI. Results from ongoing randomised trials might shed further light on the concept of deferred stenting in this patient population.

FUNDING

Danish Agency for Science, Technology and Innovation, and Danish Council for Strategic Research.

Treatment of Myocardial Ischemia/Reperfusion Injury by Ischemic and Pharmacological Postconditioning

Timely reperfusion is the only way to salvage ischemic myocardium from impending infarction. However, reperfusion also adds a further component to myocardial injury such that the ultimate infarct size is the result of both ischemia- and reperfusion-induced injury. Modification of reperfusion can attenuate reperfusion injury and thus reduce infarct size. Ischemic postconditioning is a maneuver of repeated brief interruption of reperfusion by short-lasting coronary occlusions which results in reduced infarct size. Cardioprotection by ischemic postconditioning is mediated through delayed reversal of acidosis and the activation of a complex signal transduction cascade, including triggers such as adenosine, bradykinin, and opioids, mediators such as protein kinases and, notably, mitochondrial function as effector. Inhibition of the mitochondrial permeability transition pore appears to be a final signaling step of ischemic postconditioning. Several drugs which recruit in part such signaling steps of ischemic postconditioning can induce cardioprotection, even when the drug is only administered at reperfusion, that is, there is also pharmacological postconditioning. Ischemic and pharmacological postconditioning have been translated to patients with acute myocardial infarction in proof-of-concept studies, but further mechanistic insight is needed to optimize the conditions and algorithms of cardioprotection by postconditioning.

Morphological predictors for no reflow phenomenon after primary percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction caused by plaque rupture

AIMS

Myocardial no reflow after percutaneous coronary intervention (PCI) is associated with poor outcome. Patients with ST-segment elevation myocardial infarction (STEMI) caused by plaque rupture are at high risk for no reflow. However, specific morphologic characteristics associated with no reflow are unknown in this population. The aim of this study is to identify the morphological characteristics of culprit plaques associated with no reflow in patients with STEMI caused by plaque rupture using both optical coherence tomography (OCT) and intravascular ultrasound (IVUS).

METHODS AND RESULTS

We enrolled 145 patients with STEMI who underwent both OCT and IVUS within 12 h of symptom onset. Among these patients, we excluded those with plaque erosion and calcified nodule and included 72 patients who had plaque rupture as an underlying mechanism for STEMI. Myocardial no reflow, defined as Thrombolysis in Myocardial Infarction flow grade 0-2 and/or myocardial blush grade 0-1 after PCI, was observed in 28 patients (38.9%). Onset to recanalization time was similar between the groups with and without no reflow. Receiver-operating curve analysis revealed OCT-derived lipid index > 3500 [area under curve (AUC) 0.77, P < 0.001] and IVUS-derived plaque burden > 81.5% (AUC 0.70, P = 0.002) were the best discriminators for myocardial no reflow.

CONCLUSION

No reflow occurred in nearly 40% of patients with STEMI caused by plaque rupture. Large lipid index and plaque burden were critical morphological discriminators between no reflow and normal flow.