The no-reflow phenomenon in coronary arteries

Periprocedural Myocardial Infarction in Contemporary Practice

"Periprocedural myocardial infarction (MI) occurs infrequently in the current era of percutaneous coronary interventions (PCI) and is associated with an increased risk of mortality and morbidity. Periprocedural MI can occur due to acute side branch occlusion, distal embolization, slow flow or no reflow phenomenon, abrupt vessel closure, and nonidentifiable mechanical processes. Therapeutic strategies to reduce the risk of periprocedural MI include dual antiplatelet therapy, intravenous cangrelor in the periprocedural setting, intravenous glycoprotein IIb/IIIa inhibitor in high-risk patients, anticoagulation with unfractionated heparin, low-molecular-weight heparin or bivalirudin, and embolic protection devices during saphenous vein graft interventions."

Use and impact of thrombectomy in primary percutaneous coronary intervention for acute myocardial infarction with persistent ST-segment elevation: results of the prospective ALKK PCI-registry

BACKGROUND

Data about the impact of thrombectomy in primary percutaneous coronary intervention (PCI) are inconsistent. The aim of our study was an evaluation of both the real-world use of thrombectomy and the impact of thrombectomy on outcome in unselected patients treated with primary PCI for ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

We used the data of the prospective ALKK PCI-registry of 35 hospitals from January 2010 to December 2013. A total of 10,755 patients receiving single-vessel primary PCI for acute STEMI were included. In 2176 patients (20.2 %) thrombectomy was performed. There was a wide range of use of thrombectomy in the different ALKK hospitals from 1.1 to 61.7 % (median 18.6 %, quartiles 6.0 and 40.3 %) with a general increase of use over the first years of the study period. In patients with and without thrombectomy there was TIMI 0 flow present before PCI in 6010 patients, TIMI 1 in 1338, TIMI 2 in 2002, and TIMI 3 in 1405. Patients with acute heart failure or cardiogenic shock received significantly more often thrombectomy. Fluoroscopy time (8.1 vs. 7.3 min, p < 0.0001) and dose area product (5373 cGy × cm(2) vs. 4802 cGy × cm(2), p < 0.0001) were significantly higher in patients treated with thrombectomy. The subgroup of patients with TIMI 0 flow before PCI had significantly higher rates of TIMI 3 flow after PCI when treated with thrombectomy (87.1 vs. 84.1 %, p < 0.01), while there was no difference in post-PCI TIMI 3 flow in patients with TIMI 1, 2 or 3 flow before PCI. Rates of major adverse cardiac and cerebrovascular events were similar in both groups in general and in all subgroups of TIMI flow.

CONCLUSIONS

The use of thrombectomy in patients with STEMI is heterogenous between hospitals. Overall, there was no impact of thrombectomy on TIMI 3 patency or mortality after PCI. In the subgroup of STEMI patients with TIMI 0 flow before PCI individualized thrombectomy had a positive impact on restoration of normal blood flow.

Relationship between retrograde coronary blood flow and the extent of no-reflow and infarct size in a porcine ischemia-reperfusion model

Recanalization of an infarct-related artery does not predictably reflect tissue reperfusion. We examined the relationship between coronary blood flow (CBF) pattern during reperfusion and infarcted (IA) and no-reflow (NR) area in a porcine ischemia-reperfusion model. The mid-left anterior descending artery of 18 pigs was occluded for 1 h and reperfused for 2 h. CBF during reperfusion was measured with a transit-time ultrasound flowmeter, while systemic arterial and left atrial pressures were monitored. IA and NR were measured with triphenyl tetrazolium chloride and thioflavin staining, respectively. In 13 pigs, early systolic retrograde CBF developed within the first 30 min and persisted throughout reperfusion. No retrograde CBF was observed in five pigs. Mean retrograde CBF at 2 h of reperfusion predicted a larger IA (r = 0.71; p = 0.001). Time-to-development of retrograde CBF was inversely related to IA (r = -0.55; p = 0.019) and NR (r = -0.62; p = 0.006). A larger IA (OR 1.12, 95% CI 1.01-1.24, p = 0.037) and NR (OR 1.09, 95% CI 1.01-1.18, p = 0.037) predicted the presence of retrograde CBF. Retrograde CBF during recanalization of the infarct-related artery predicts IA and NR and might be used as an index of successful reperfusion at the tissue level.

Embolic protection: Limitations of current technology and novel concepts

Distal embolic event is one of the major limitations of coronary and non-coronary vascular interventions. Balloon and filter-based Embolic Protection Devices (EPDs) are a new class of interventional devices, used to prevent consequential morbidity and mortality of the distal embolic events. Data from first generation EPD supply proof of concept and show approximately 40% reduction in mortality and morbidity, when EPDs are used during saphenous vein grafts (SVGs) interventions. Current limitations of all first generation EPD technology taper their penetration. With breakthroughs in embolic protection technology, it is estimated that, in the near future, EPDs will be used with stenting in all high-risk lesions (SVGs, carotid arteries and acute coronary syndromes), become the standard of care and even be used in low risk cases.

Carvedilol reduces myocardial no-reflow by decreasing endothelin-1 via activation of the ATP-sensitive K+ channel

It has been verified that carvedilol can attenuate myocardial no-reflow. However, the effects of carvedilol on adenosine triphosphate-sensitive K+ (KATP) channel and endothelin-1 (ET-1) are unknown. Forty mini-swines were randomized into 5 study groups: 8 control, 8 carvedilol pretreatment, 8 glibenclamide (KATP channel blocker)-treated, 8 carvedilol and glibenclamide-pre-treated and 8 sham-operated. An acute myocardial infarction(AMI) and reperfusion model was created with a three-hour occlusion of the left anterior descending coronary artery followed by one-hour reperfusion. Compared with the control group, carvedilol significantly decreased the area of no-reflow (myocardial contrast echocardiography: from 78.5±4.5% to 24.9±4.1%, pathological means: from 82.3±1.9% to 25.8±4.3% of ligation area, respectively; all p < 0.01) and reduced necrosis size from 98.5±1.3% to 74.4±4.7% of ligation area, p < 0.05). It also decreased plasma ET-1 and myocardial tissue ET-1. However, glibenclamide abrogated the protective effect of carvedilol. The beneficial effect of carvedilol on myocardial no-reflow could be due to its effect on ET-1 via the activation of the KATP channel.

Intracoronary Vasodilators for the No-Reflow Phenomenon

Objective:

To review the literature relating to the use of intracoronary vasodilators to prevent and/or treat the no-reflow phenomenon in patients undergoing percutaneous coronary intervention (PCI).

Data Sources:

A literature search was conducted using MEDLINE (1966–March 2008) and Science Citation Index (1945–March 2008) using the search terms vasodilators, no-reflow, and intracoronary.

Study Selection and Data Extraction:

English-language clinical trials and case series were selected from articles retrieved. References of reviewed articles were examined for additional sources. Studies relating to the use of intracoronary vasodilators in the prevention and/or treatment of no-reflow in PCI were evaluated for safety and efficacy data. Articles relating to agents not available in the US were excluded.

Data Synthesis:

Evidence of intracoronary adenosine's utility in no-reflow treatment is limited. Its use in no-reflow prevention was associated with outcomes ranging from no difference to nearly an 88% reduction in no-reflow development; the drug was generally well tolerated. No-reflow treatment with intracoronary verapamil improved flow in 87–100% of cases. Preventive trials with verapamil failed to demonstrate efficacy. Atrioventricular block requiring treatment was the most commonly reported adverse event with intracoronary verapamil. Literature on intracoronary diltiazem and intracoronary nicardipine is limited. Both agents produced greater than 95% efficacy in no-reflow treatment, while prevention studies found no-reflow developing in less than 4% of patients. Although adverse event reporting was limited, hemodynamic instability was noted in patients receiving diltiazem. Response rates ranged from 73% to 100% when intracoronary nitroprusside was studied as treatment for no-reflow associated with acute myocardial infarction (AMI). Systemic hypotension was noted with nitroprusside administration.

Conclusions:

The available data are predominately from case series and retrospective reviews. Prevention of no-reflow with intracoronary vasodilators in elective PCI is not warranted. Nitroprusside should be considered first-line treatment in no-reflow associated with AMI.

Comparison of intracoronary and transendocardial delivery of allogeneic mesenchymal cells in a canine model of acute myocardial infarction

This study assessed safety of transendocardial (TE) electromechanical-guided delivery of bone marrow mesenchymal stem cells (MSCs) after acute myocardial infarction (AMI) and compared intracoronary (IC) delivery with TE delivery. In a canine acute myocardial ischemia model, 100 x 10(6) MSCs were delivered 7 days after AMI via IC and TE routes. Functional assessment was performed by 2D echocardiogram, and detailed histopathologic analyses were performed to assess the impact of cell therapy in vascular density and fibrosis. Patterns of cell distribution in both delivery methods were also compared. There was a statistically significant reduction in the amount of myocardial ischemia in the TE group (P=0.007). Left ventricular ejection fraction (LVEF) increased 13% (mean) in the TE group (21-day follow-up) and was significantly better than that of the controls (P=0.01), but did not improve in the IC-delivery group. Dissimilar patterns of cell distribution were noted between the IC and TE groups. This study suggests that MSC treatment is probably safe and effective after AMI. In the comparison of TE and IC delivery, the TE group showed higher cell retention (clusters even in the injury center of the infarct) with an increased vascularity and greater functional improvement than did the IC group (no clusters; cells at the border of the infarct). The higher local cell density in the TE group may be important for therapeutic effectiveness.

Role of pre-infarction angina and inflammatory status in the extent of microvascular obstruction detected by MRI in myocardial infarction patients treated by PCI

BACKGROUND/OBJECTIVES

The extent of microvascular obstruction (MVO) during myocardial infarction referred to as the "no-reflow phenomenon", may determine myocardial damage. Our study aimed to investigate the incidence and the influencing factors of MVO in patients with ST-elevation myocardial infarction (STEMI) treated by primary percutaneous intervention (PCI).

PATIENTS, METHODS

Using contrast-enhanced MRI, microvascular obstruction was defined as early hypoenhancement. Contrast defects were scored from 0 (no hypoenhancement) to 3 (strong hypoenhancement). 50 patients (56+/-11 years) with STEMI underwent PCI. Contrast-enhanced MRI (6+/-2 days after STEMI) and biochemical parameters were evaluated.

RESULTS

Microvascular obstruction (score 1 to 3) was observed in 90% of the patients and major microvascular obstruction (score 2-3) in 54%. In univariate analysis, leukocytes and CRP levels were associated with MVO, whereas pre-infarction angina and prior medication by aspirin or calcium channel antagonist appeared protective. Microvascular obstruction intensity positively correlated with baseline inflammation status assessed by C-reactive protein and leukocytes (rho=0.43 and rho=0.44; p=0.003), the peak of CK (rho=0.56; p=0.01) or Troponin I (rho=0.59; p=0.01) and negatively correlated with LVEF (rho=-0.44; p=0.002). Multivariate analysis identified the absence of pre-infarction angina as the only independent predictor for microvascular obstruction (odds ratio, 8.35, 95% confidence interval 1.27-54.71; p=0.027).

CONCLUSION

MRI-detected microvascular obstruction has a high incidence in patients with STEMI treated by primary PCI and determines post-MI LVEF even in patients with post PCI TIMI 3 flow score. Pre-infarction angina appears to be an independent determinant of the extent of MVO detected by MRI.

Incidence and Management of "No-Reflow" Following Percutaneous Coronary Interventions

No-reflow is a complex condition associated with inadequate myocardial perfusion of the coronary artery in the absence of epicardial obstruction. It can occur in several settings, including percutaneous coronary intervention, especially in complex thrombotic lesions of native arteries and vein grafts and in primary angioplasty. The causes of no-reflow are not completely understood, and current treatments consist of intracoronary vasodilators, antithrombotic therapies, and mechanical devices (including aspiration thrombectomy catheters and embolic protection devices).