Time-Dependent Detrimental Effects of Distal Embolization on Myocardium and Microvasculature During Primary Percutaneous Coronary Intervention

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.

Stable Low-Dose Oxygen Release Using H2O2/Perfluoropentane Phase-Change Nanoparticles with Low-Intensity Focused Ultrasound for Coronary Thrombolysis

After the onset of myocardial infarction, extensive coronary thrombus and oxygen supply insufficiency lead to severe myocardial damage and heart failure. Recently, ultrasound-irradiated phase-change nanoparticles have been recognized for their cardiovascular thrombolysis potential. Therefore, we sought to establish a novel treatment method using hydrogen peroxide (H₂O₂)/perfluoropentane (PFP) phase-change nanoparticles with low-intensity focused ultrasound (LIFU) for the simulation of acute coronary thrombolysis and myocardial preservation. There were three groups in our study: Group A consisted of phosphate-buffered saline (PBS) as the blank control, group B consisted of SonoVue microbubbles and group C consisted of H₂O₂/PFP phase-change nanoparticles. The H₂O₂/PFP phase-change nanoparticles were prepared using a double-emulsification process. The in vitro experiments were conducted in an artificial circulatory system connected to an LIFU system and dissolved oxygen detector. Thrombolysis efficiency and oxygen release efficiency were compared among the groups. H₂O₂/PFP nanoparticles with 3% H₂O₂ (average size: 456.7 ± 31.2 nm, charge: -37.5 ± 5.22 mV) was the optimal selection in group C because of the stable loading capacity and stable low-dose oxygen release efficiency in the in vitro experiments. Thrombolytic weight loss and loss rates in group C (322.0 ± 40.8 mg, 54.8 ± 5.7%) were significantly higher than those in group A (36.2 ± 18.1 mg, 5.5 ± 2.5%) and group B (91.0 ± 11.9 mg, 14.3 ± 2.4%) (p < 0.01). The innovative method using H₂O₂/PFP phase-change nanoparticles with LIFU exhibited high thrombolytic efficiency and stable low-flow oxygen supply in the artificial circulatory system, providing a solid experimental foundation for the establishment of a novel treatment method for acute myocardial infarction.

Predictors of angiographically visible distal embolization in STEMI

BACKGROUND

Distal embolization during primary percutaneous coronary intervention (p-PCI) in the treatment of ST-segment elevation myocardial infarction (STEMI) is associated with a poor prognosis. In this situation, thrombectomy is performed to prevent distal embolization and to restore myocardial reperfusion. The aim of our study was to determine angiographic predictors of angiographically visible distal embolization (AVDE) in patients with STEMI treated by p‑PCI with thrombectomy.

PATIENTS AND METHODS

This prospective study included all consecutive patients who underwent p‑PCI with thrombectomy for STEMI at our institution between October 2011 and December 2014 AVDE was defined as a distal filling defect with an abrupt cut-off in one of the peripheral coronary branches of the infarct-related artery, distal to the angioplasty site. Thrombectomy was considered positive when it removed thrombi, and successful when it improved coronary flow.

RESULTS

Among the 346 patients included, 59 (17%) developed AVDE during p‑PCI. In multivariate analysis, the infarct-related right coronary artery (OR: 2.48, 95% CI: 1.36-4.52; p = 0.003) and a culprit lesion diameter of >3 mm (OR : 1.90, 95% CI: 1.01-3.56; p = 0.048) were identified as independent factors associated with AVDE during p‑PCI with thrombectomy for STEMI. The success of thrombectomy and the Syntax score were not associated with AVDE.

CONCLUSION

AVDE complicating p‑PCI with thrombectomy in STEMI is frequent (17%) and a successful thrombectomy does not rule out AVDE.

Thrombus aspiration during primary percutaneous coronary intervention associated with reduced platelet activation

Objectives:

To determine the effect of thrombectomy on platelet function in patients undergoing primary percutaneous coronary intervention (PPCI) for ST segment elevation myocardial infarction (STEMI).

Methods:

This retrospective study included 413 consecutive STEMI patients who underwent PPCI between March 2012 and September 2013 at Kartal Kosuyolu High Specialty Education and Research Hospital, Istanbul, Turkey that were assigned to the thrombus aspiration (TA) group or the non-TA group. Platelet count and mean platelet volume (MPV) were obtained at baseline and 24 hours (h), 48 h, and 72 h post PPCI.

Results:

Baseline MPV was similar in both groups, whereas the baseline platelet count was higher in the TA group (p=0.42 and p=0.002). The platelet count was higher in the TA group 24 h post PPCI (p=0.02), but was similar in both groups 48 h and 72 h post PPCI (p=0.18 and p=0.07). The MPV 48 h and 72 h post PPCI was higher in the non-TA group than in the TA group (8.4 ± 1.3 fL versus 8.7 ± 1.6 fL [p=0.04] and 8.5 ± 1.1 fL versus 8.9 ± 1.5 fL [p=0.04]).

Conclusion:

Thrombectomy reduced platelet activity via removal of thrombi from the coronary arteries in patients undergoing PPCI for STEMI.

Development and Validation of a Distal Embolization Risk Score During Primary Angioplasty in ST-Elevation Myocardial Infarction

This study aims to develop and validate a new angiographic risk score to predict the risk of distal embolization (DE) during primary percutaneous coronary intervention (p-PCI) for ST-elevation myocardial infarction. Study included data from 1,200 patients who underwent p-PCI. The cohort was randomly split into a derivation cohort (n = 814) and a validation cohort (n = 386). Logistic regression was used to examine the relation between risk factors and the occurrence of DE. To each covariate in the model was assigned an integer score based on the regression coefficients. Variables included in the risk score, according to multivariable analysis, were occlusion pattern of infarct-related artery, Thrombolysis In Myocardial Infarction Thrombus Score 2 to 4, reference vessel diameter ≥3.5 mm, and lesion length >20 mm. To each variable was assigned a 0- to +2-point score according to the strength of the statistical association. Rates of DE in low-, intermediate-, and high-risk groups were 5.6%, 15.8%, and 40% in the derivation cohort (p for trend <0.0001; C-statistic 0.70) and 7.5%, 12.1%, and 37.9% in the validation cohort (p for trend <0.0001; C-statistic 0.62), respectively. In conclusion, the individual risk of DE in patients who underwent p-PCI can be predicted using a simple 4-variables model based on angiographic features.

Coronary microvascular obstruction in acute myocardial infarction

The success of a primary percutaneous intervention (PCI) in the setting of ST elevation myocardial infarction depends on the functional and structural integrity of coronary microcirculation. Coronary microvascular dysfunction and obstruction (CMVO) occurs in up to half of patients submitted to apparently successful primary PCI and is associated to a much worse outcome. The current review summarizes the complex mechanisms responsible for CMVO, including pre-existing coronary microvascular dysfunction, and highlights the current limitations in the assessment of microvascular function. More importantly, at the light of the substantial failure of trials hitherto published on the treatment of CMVO, this review proposes a novel integrated therapeutic approach, which should overcome the limitations of previous studies.

How does coronary stent implantation impact on the status of the microcirculation during primary percutaneous coronary intervention in patients with ST-elevation myocardial infarction?

AIMS

Primary percutaneous coronary intervention (PPCI) is the optimal treatment for patients presenting with ST-elevation myocardial infarction (STEMI). An elevated index of microcirculatory resistance (IMR) reflects microvascular function and when measured after PPCI, it can predict an adverse clinical outcome. We measured coronary microvascular function in STEMI patients and compared sequential changes before and after stent implantation.

METHODS AND RESULTS

In 85 STEMI patients, fractional flow reserve, coronary flow reserve, and IMR were measured using a pressure wire (Certus, St Jude Medical, St Paul, MN, USA) immediately before and after stent implantation. Stenting significantly improved all of the measured parameters of coronary physiology including IMR from 67.7 [interquartile range (IQR): 56.2-95.8] to 36.7 (IQR: 22.7-59.5), P < 0.001. However, after stenting, IMR remained elevated (>40) in 28 (32.9%) patients. In 15 of these patients (17.6% of the cohort), only a partial reduction in IMR occurred and these patients were more likely to be late presenters (pain to wire time >6 h). The extent of jeopardized myocardium [standardized beta: -0.26 (IMR unit/Bypass Angioplasty Revascularization Investigation score unit), P: 0.009] and pre-stenting IMR [standardized beta: -0.34 (IMR unit), P: 0.001] predicted a reduction in IMR after stenting (ΔIMR = post-stenting IMR - pre-stenting IMR), whereas thrombotic burden [standardized beta: 0.24 (IMR unit/thrombus score unit), P: 0.01] and deployed stent volume [standardized beta: 0.26 (IMR unit/mm(3) of stent), P: 0.01] were associated with a potentially deleterious increase in IMR.

CONCLUSION

Improved perfusion of the myocardium by stent deployment during PPCI is not universal. The causes of impaired microvascular function at the completion of PPCI treatment are heterogeneous, but can reflect a later clinical presentation and/or the location and extent of the thrombotic burden.

Aspiration Thrombectomy for Treatment of ST-segment Elevation Myocardial Infarction: a Meta-analysis of 26 Randomized Trials in 11,943 Patients

INTRODUCTION AND OBJECTIVES

There is continued debate about the routine use of aspiration thrombectomy in patients with ST-segment elevation myocardial infarction. Our aim was to evaluate clinical and procedural outcomes of aspiration thrombectomy-assisted primary percutaneous coronary intervention compared with conventional primary percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction.

METHODS

We performed a meta-analysis of 26 randomized controlled trials with a total of 11 943 patients. Clinical outcomes were extracted up to maximum follow-up and random effect models were used to assess differences in outcomes.

RESULTS

We observed no difference in the risk of all-cause death (pooled risk ratio = 0.88; 95% confidence interval, 0.74-1.04; P = .124), reinfarction (pooled risk ratio = 0.85; 95% confidence interval, 0.67-1.08; P = .176), target vessel revascularization (pooled risk ratio = 0.86; 95% confidence interval, 0.73-1.00; P = .052), or definite stent thrombosis (pooled risk ratio = 0.76; 95% confidence interval, 0.49-1.16; P = .202) between the 2 groups at a mean weighted follow-up time of 10.4 months. There were significant reductions in failure to reach Thrombolysis In Myocardial Infarction 3 flow (pooled risk ratio = 0.70; 95% confidence interval, 0.60-0.81; P < .001) or myocardial blush grade 3 (pooled risk ratio = 0.76; 95% confidence interval, 0.65-0.89; P = .001), incomplete ST-segment resolution (pooled risk ratio = 0.72; 95% confidence interval, 0.62-0.84; P < .001), and evidence of distal embolization (pooled risk ratio = 0.61; 95% confidence interval, 0.46-0.81; P = .001) with aspiration thrombectomy but estimates were heterogeneous between trials.

CONCLUSIONS

Among unselected patients with ST-segment elevation myocardial infarction, aspiration thrombectomy-assisted primary percutaneous coronary intervention does not improve clinical outcomes, despite improved epicardial and myocardial parameters of reperfusion.

Total ischaemic time and 9-year outcomes in STEMI patients treated with pPCI

BACKGROUND

Prolonged total ischaemic time (TIT) has been shown to independently predict poor myocardial perfusion in STEMI patients and affect in-hospital mortality. We aim to evaluate the influence of TIT on long-term follow-up (F/U) and identify the factors associated with TIT in patients with STEMI treated with pPCI at a high volume centre.

METHODS

In a prospective "all-comer" registry, clinical, angiographic and procedural characteristics, TIT and 9-year mortality were determined in consecutive STEMI patients treated with pPCI. Patients were divided according to TIT into three groups: A) <3, B) 3-6 and C) >6h.

RESULTS

Among 1064 patients, TIT was known in 1002 patients, 5 patients were lost to F/U. For censored observations F/U was 7.2-8.8 years. There were 350, 461, and 186 patients in groups A, B, and C, respectively. Patients in group A compared to B and C were younger, more often males and smokers, less frequently had history of CAD, and more frequently had occluded infarct related artery. However, final TIMI3 was obtained more frequently. Overall 30-day mortality was 4%, one-year mortality 7% and nine-year mortality 27%. Multivariable logistic regression models indicated that longer TIT was associated with a higher risk of 9-year mortality (A-21%, B-28%, C-37%, p<0.0005). TIT>6h was independently associated with advanced age, diabetes mellitus, history of CAD and higher rate of initial TIMI grade flow 3.

CONCLUSIONS

TIT is strongly related with mortality in STEMI patients even after nine years of F/U. This finding reinforces the necessity of shortening the TIT in all STEMI patients.

Association of mean platelet volume with angiographic thrombus burden and short-term mortality in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention

OBJECTIVES

The aim of this study was to evaluate the impact of mean platelet volume (MPV) on the intracoronary thrombus burden and short-term mortality in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

BACKGROUND

Platelets play a crucial role in the pathophysiology of coronary artery disease. MPV has been reported to be an indicator of platelet reactivity.

METHODS

A total of 649 consecutive STEMI patients who underwent primary PCI between January 2008 and December 2013 were enrolled and divided into two groups based on the thrombus burden: the large thrombus burden (LTB) group and the small thrombus burden (STB) group. The primary endpoint was all-cause mortality at 30 days.

RESULT

The LTB group had significantly higher admission MPV compared with the STB group (10.77 ± 1.22 vs. 9.95 ± 1.03, P < 0.001). The cumulative 30-day all-cause mortality rate was significantly higher in the groups with high MPV and LTB (9.8% vs. 2.5%, P < 0.001, 8.6% vs. 4.1%, P = 0.036, respectively). In a receiver operating characteristics analysis, MPV ≥ 10.2 predicted LTB with 73.5% sensitivity and 68.9% specificity. Multivariate logistic regression analysis demonstrated MPV was an independent predictor of large intracoronary thrombus burden (OR 1.794, 95% CI 1.533 to 2.100, P < 0.001) and 30-day all-cause mortality (HR 1.408, 95% CI 1.040 to 1.906, P = 0.027).

CONCLUSIONS

Increased MPV at admission is an independent predictor of large intracoronary thrombus burden and short-term mortality. It may be a useful biomarker for risk stratification in patients with STEMI undergoing primary PCI. © 2015 Wiley Periodicals, Inc.

Efficacy of an Embolic Protection Stent as a Function of Delay to Reperfusion in ST-Segment Elevation Myocardial Infarction (from the MASTER Trial)

The ability of stent implantation to improve indexes of reperfusion may depend on the time to reperfusion in acute ST-segment elevation myocardial infarction (STEMI) and may also vary with stent type. The purpose of this prespecified analysis from the randomized MGUARD for Acute ST Elevation Reperfusion trial was to evaluate the impact of delay to reperfusion on outcomes in patients with STEMI undergoing primary percutaneous coronary intervention with the MGuard embolic protection stent or standard metallic stents. A total of 431 patients were divided according to symptom-onset-to-balloon time (SBT) into 2 groups: SBT ≤3 hours (167 patients; 39%) and SBT >3 hours (264 patients; 61%). Complete ST-segment resolution (STR) after percutaneous coronary intervention was more often achieved in patients with shorter SBT (58.6% vs 47%, p = 0.02). At 1 year, the all-cause mortality rate was lower in patients with shorter SBT (0% vs 3.5%, p = 0.02). STR was achieved in 58% of MGuard patients and in 45% of the control stent patients (p = 0.008). STR was 57% in the MGuard group versus 38% in the control group (p = 0.002 for SBT >3 hours) and 60% versus 57% (p = 0.72), respectively, for SBT ≤3 hours (p for interaction = 0.11). In conclusion, longer delay to mechanical reperfusion remains an important factor negatively influencing outcomes in patients with STEMI. Use of the MGuard embolic protection stent compared with conventional metallic stents resulted in superior rates of complete STR, even in patients with longer delays to reperfusion.

Thrombus burden and myocardial damage during primary percutaneous coronary intervention

Large thrombus burden (LTB) lesions in the context of primary percutaneous coronary intervention (p-PCI) have been related to unsuccessful angiographic reperfusion and unfavorable clinical outcomes. However, the hazard of LTB treatment on myocardial damage has not been evaluated. We investigated the impact of LTB on myocardial damage using contrast-enhanced cardiac magnetic resonance (CE-CMR) in the setting of p-PCI. In 327 patients, who underwent p-PCI without thrombus aspiration within 12 hours from symptom onset, we prospectively assessed the impact of LTB on infarct size and microvascular damage using CE-CMR. LTB was defined by the presence of Thrombolysis In Myocardial Infarction thrombus score ≥3 in patent infarct-related artery (IRA); or by "cut-off" occlusion pattern and/or large reference vessel diameter (≥3.5 mm) in occluded IRA. One hundred ninety-seven patients (60.2%) showed LTB and 130 (39.8%) did not. Distal embolization occurred in 18.8% patients with versus 6.9% without LTB (p = 0.003). At CE-CMR, patients with LTB had larger infarct size index (27.5 ± 11.1 vs 22.1 ± 17.5, p = 0.009) and more often transmural necrosis (70.5% vs 55.4%, p = 0.008) compared with patients without LTB. Excluding patients with distal embolization, patients with LTB still had larger necrosis. At multivariate analysis, occluded (IRA) at baseline, anterior infarction, and presence of LTB predicted transmural necrosis. In conclusion, LTB in the setting of p-PCI is related to larger myocardial damage as detected by CE-CMR, regardless of angiographic detectable distal embolization.