M-Guard stent in STEMI patients with high thrombus burden lesions Mahmoud Shabestari Baktash Bayani Ali Eshraghi Bahram Shahri Mashhad University of Medical Sciences

Emergent percutaneous coronary intervention (PCI) is the preferred modality to restore blood perfusion in ST-segment elevation myocardial infarction (STEMI) patients. This method is highly effective in the restoration of infarct related artery. However, despite the effectiveness of stent implantation during primary PCI for epicardial reflow , myocardial perfusion is often lower than optimum which is confined by low Myocardial Blush Grade (MBG) and poor resolution of ST-segment elevation in near two third of patients undergone emergent PCI.

Impaired myocardial reperfusion leads to increase the size of infracted area, left sided heart failure and finally increasing the mortality in both short term and long term follow up. There are various mechanisms underlying this phenomenon but distal embolization of thrombi and/or fragile atheromatous debri due to PCI, "no-reflow phenomenon", seems to be the leading role.

Researchers use different thrombectomy and protective emboli devices (PEDs) and various pharmacologic agents to improve post procedural myocardial reperfusion in STEMI patients which cause conflicting results. M-guard stent is a mesh covered stent which prevent plaque fragmentation and distal embolization during the implantation of stent. Trials have shown that among STEMI patients undergone emergent PCI, compare to Bare Metal Stents (BMS), M-guard stents result in higher rates of epicardial perfusion and complete ST resolution. However, there is low evidence suggestive for M-guard stenting in culprit vessels with large thrombus bulk with or without primary mechanical aspiration.

Methods and Materials

Study design All patients with acute STEMI admitted at cardiac emergency ward of Imam Reza hospital in Mashhad from July 13th 2011 to November 17th 2012 whom went under angiography and had large bulk of thrombus in their angiogram were eligible for next evaluations.

The study was designed single case group and prospective. The patients were met criteria for study on condition that: They had acute STEMI (persistent chest pain more than 30 minutes and less than 12 hours and ≥2 mm ST-segment elevation in V1 –V3 leads or ≥1mm in at least 2 other contiguous electrocardiographic leads. Evidence of large thrombus bulk was seen on coronary angiogram (TIMI thrombus grade 4-5) The culprit vessel had no severe tortuosity or heavy calcification. Vessel was estimated visually ≥ 3 mm and ≤4mm in diameter.

Study device The M-guard stent is a recently innovation prevent distal embolization of thrombi or plaque debri during stent implantation and is made of a bared metal stent, covered with a tiny (in micron level) mesh. The bare metal stent is an expandable balloon made of cobalt-Chromium alloy and the mesh is polyethylene terephthalate microfiber. Stents of 2.5 to 4.0 mm in diameter and 19 to 39 mm in length were used during this study.

Procedure Immediately after confirmation of Acute STEMI diagnosis with ECG, patients were administered 300 mg Aspirin, 600 mg Clopidogrel as well as high dose Beta Blockers, Statins and Nitrates. With the time of Door to Balloon less than 90 minutes, intended patients for primary PCI were undergone angiography and those with a high burden of thrombus (TIMI grade 4-5) selected for primary angioplasty using M-guarded stents. In 60 to 90 minutes after procedure, a control ECG was taken. All patients were visited monthly by extra hospital cardiologist, and at 6 months clinical follow up a telephone contact was done to supervise cardiac symptoms and weather they had angioplasty again.

Result All 23 patients aged between 34 and 84 (mean ± SD; 63.48 ±14.60), 65.2% male, were gone under PCI, mechanical thrombus aspiration and M-Guard stenting. LAD artery (63.9%) and RCA (39.1%) were involved. 78.2% of patients had primary TIMI 5 Thrombus grade ,13.1% TIMI 4 thrombus grade and 8.9% TIMI 3 thrombus grade. Among them 86.9% achieved TIMI 3 Flow grade and 13.04% TIMI 2 Flow grade.

The rate of transient "no-reflow" phenomenon was 21%. One patient died at the same course of admission due to cardiogenic shock. Of 15 accessible patients after 6 months, no one experienced second angioplasty or ischemic symptoms.

CULPRIT VESSEL

STENT DIAMETER

STENT LENGHT

TIMI FLOW B

TIMI F A

TIMI F A

TIMI T B

TIMI T A

Conclusion Using M-Guard stents in Acute STEMI patients undergone primary PCI and had high thrombus burden is probably associated with lower rates of "no-reflow" phenomenon and improved vessel reperfusion. Extended controlled trials will be a matter of benefit.