M-Guard Stent in Stemi Patients with High Thrombus Burden Lesions: A Prospective, Single Arm Study

Introduction

There are various mechanisms underlying this phenomenon but distal embolization of thrombi and/or fragile atheromatous debri due to PCI, the "no-reflow phenomenon", seems to have the leading role (13-16).

Researchers use different thrombectomy and Protective Emboli Devices (PEDs) and various pharmacological agents to improve post procedural myocardial reperfusion in STEMI patients with conflicting reported results (17-23). M-guard stent is a mesh covered stent which prevents plaque fragmentation and distal embolization during stent implantation (24-26). Several trials have shown that among STEMI patients having undergone primary PCI, compared to Bare Metal Stents (BMS), M-guard stents result in higher rates of epicardial perfusion and complete ST resolution (24, 27, 28).

However, there is rare evidence suggestive for M-guard stenting in culprit vessels with a large thrombus bulk with or without primary mechanical aspiration (24). In the present study patients with acute STEMI who had a large bulk of thrombus in their angiogram, underwent M-Guard stenting and acute and long term outcomes were evaluated.

Materials and Methods

Study design: All patients with acute STEMI admitted to the Cardiac Emergency Unit of Imam Reza Hospital, Mashhad, Iran from July 2011 to November 2012 who underwent angiography and had a large thrombus bulk in their angiogram were considered as eligible for further evaluations. This was a prospective, single case group study in which the inclusion criteria was as follows:

1. Acute STEMI (persistent chest pain more than 30 minutes and less than 12 hours and ≥ 2mm ST-segment elevation in V1 –V3 leads or ≥1mm in at least 2 other contiguous electrocardiographic leads).

2. Evidence of a large thrombus bulk on coronary angiogram (TIMI thrombus grade 4-5)

3. No severe tortuosity or heavy calcification in the culprit vessel.

4. Vessel size estimated visually ≥ 3 mm and ≤ 4 mm in diameter.

The study protocol was approved by the Medical Ethics Committee of Mashhad University of Medical Sciences and a written informed consent was obtained from each patient prior to study entrance.

Study device: The M-guard stent is a recent innovation for the prevention of distal embolization of thrombi or plaque debri during stent implantation. It 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 stainless steel, and the mesh is of polyethylene terephthalate microfiber. Stents of three to four mm in diameter and 19 to 39 mm in length were used during this study.

Procedure:Immediately after confirming the diagnosis of Acute STEMI by ECG, the patients were administered 300 mg Aspirin, 600 mg Clopidogrel as well as Beta Blockers, Statins and Nitrates. With a time of Door to Balloon less than 90 minutes, selected patients for primary PCI underwent angiography, and those with a high burden of thrombus (TIMI grade four-five) were selected for primary angioplasty using M-guarded stents. 60 to 90 minutes after the procedure, a control ECG was taken. IIb-IIIa inhibitors (Eptifibatide) were used in only three patients. All patients were prescribed at least five types of medications on their discharge order including: Aspirin, Clopidogrel, Statins, Angiotensin Converting Enzyme (ACE) inhibitors and Beta blockers. All patients were visited monthly by a single cardiologist, and at six months of clinical follow- up, they were contacted by telephone to ask for cardiac symptoms and find out whether they required re-angioplasty on their stent.

Results

This study investigated 23 patients with acute STEMI admitted to the Cardiac Emergency Unit of Imam Reza Hospital, Mashhad from July 2011 to November 2012 who underwent Percutaneous Coronary Intervention (PCI) with Mesh Guard stent.

Demographic data of the patients is shown in Table1.

63.9% of the patients had lesions in their LAD artery, and in 39.1%, the RCA was involved. In every patient, only one lesion was treated. After angiography and primary thrombus aspiration (in 20 patients), 87% of patients still had no flow in their culprit vessel (TIMI thrombus grade five and TIMI flow grade zero-one).

Stent implantation was done successfully in all patients, and there was no dislodgement or peripheral stent embolization during stenting. Stents with a length of 19 to 39 mm (mean: 28.78 mm) and a diameter of three to four mm (mean: 3.22 mm) were deployed.

High-pressure stent inflation (at least 14 atm) was performed in every patient (Table-1). In three patients, post dilatation with noncompliant balloon was done due to obvious non-expanded stents. TIMI flow grade three was attained in 87% of patients after stenting. Among the 78.28% of patients with primary TIMI thrombus grade 5, 65. 22% achieved TIMI flow grade three, and 13.04% reached TIMI flow grade two after M-guard stent deployment. All patients with a smaller thrombus bulk experienced complete reperfusion after stent implantation. The rate of transient "no-reflow" phenomenon was 21.7%. One patient died after successful stenting due to cardiogenic shock at the time of admission.  There was one case of diffuse in-stent restenosis five months after primary PCI in ostioproximal LAD in a 49-year-old diabetic male.

After six months, only 15 out of 22 patients were accessible by telephone. They all mentioned monthly visits by a non-faculty cardiologist. None of them experienced secondary angioplasty during the six months of follow-up.

Discussion