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July 2007, Volume 57, Issue 7

Original Article

Aspiration of Thrombus in ST Segment Elevation Myocardial Infarction

Tariq Ashraf  ( Catheterization Laboratory, National Institute of Cardiovascular Diseases, Karachi. )
Syed Ishtiaq Rasool  ( Catheterization Laboratory, National Institute of Cardiovascular Diseases, Karachi. )
Tahir Saghir  ( Catheterization Laboratory, National Institute of Cardiovascular Diseases, Karachi. )
Syed Nadeem Hassan Rizvi  ( Catheterization Laboratory, National Institute of Cardiovascular Diseases, Karachi. )
Nadeem Qamar  ( Catheterization Laboratory, National Institute of Cardiovascular Diseases, Karachi. )
Khan Shah Zaman  ( Catheterization Laboratory, National Institute of Cardiovascular Diseases, Karachi. )
Mohammad Ishaque  ( Catheterization Laboratory, National Institute of Cardiovascular Diseases, Karachi. )
Asadullah Kundi   ( Catheterization Laboratory, National Institute of Cardiovascular Diseases, Karachi. )

Abstract

 Objective:To evaluate the impact of Export Aspiration Catheter with restoration of ECG changes, arterial flowand myocardial perfusion in patients with ST segment elevation Myocardial Infarction undergoing Percutaneous Coronary Intervention (PCI).Methods:Atotal of 40 consecutive patients with STSegment Elevation Myocardial Infarction (STEMI) wereselected. They underwent treatment according to the surgeon’s discretion to either standard PCI or PCI with thrombus aspiration Catheter. Primary end points of the study were STSegment resolution (STR) > 70% and myocardial blush grade (MBG) > 2.Results:The base line clinical and procedural characteristics were same for both the groups.  In the post intervention comparison the thrombus aspiration group was found to have significantly better outcomes ascompared to the standard PCI group with regards to TIMI flow grade (p = 0.009) and myocardial blush grade (p= 0.001).  Considering the criteria for MBG and STR together, the thrombus aspiration was found to have significantly better outcome than the standard PCI group (p = 0.017).Conclusion:This non-randomized study shows that Export Aspiration Catheter group with STEMI undergoing primary PCI is feasible and results in better angiographic ECG and myocardial perfusion rates compared with standard PCI. Role of export catheter in rescue PCI and thrombus Sapheneous Venous Graft (SVG) as primary PCI is questionable and needs larger randomized studies to prove its efficacy

Introduction

 In the United States coronary heart disease is the leading cause of death with myocardial infarction as one ofits presentation. In 2006, 1.2 million Americans sustained amyocardial infarction with one quarter to one third with ST-Segment Elevation.1Thrombus formation after plaque rupture causesvessel closure in acute myocardial infarction and contributes to compromised flow in unstable angina.Percutaneous transluminal coronary angioplasty and stenting are options for managing acute coronary syndrome and are associated with higher patency rates of coronaryarteries than medical therapy in patients with ST-elevationmyocardial infarction (STEMI).2The primary goal of primary angioplasty is immediate restoration of normalflow in the infarcted artery.  Although thrombolysis in MI(TIMI) grade 3 flow is necessary it is not sufficient toensure myocardial salvage.  The microcirculation isaffected during acute MI by both ischaemic death and micro-embolization from ruptured plaque andaccompanying platelet and fibrin thrombus demonstrated when embolic protection devices are used.3Data from different groups4,5have suggested that thrombus aspirating devices might reduce the culpritcoronary lesion, thrombus burden and facilitate myocardialperfusion. We have performed single centre study to evaluate the benefit of export aspiration catheter during primary percutaneous coronary intervention (PCI) rescuePCI and PCI in saphenous venous graft (SVG) in the setting of STsegment elevation MI to see if it decreases clotburden, improves TIMI 3 flow, myocardial blush grade andST-Segment resolution in ECG.

Patients and Methods

 All patients with STEMI within 12 hours of chestpain referred for primary or rescue PCI were taken to our catheterization laboratory in coordination with emergency room of our institution between January 2005 and November 2005.  Non affording patients were excluded from the study and given thrombolytic therapy.  Selection ofcases for standard PCI and with export aspiration catheterwas made on surgeon's discretion.Export Aspiration Catheter (Medtronic) is 6 Frenchc ompatible and 145 cm in length.  Distal port has twolumen, one for 0.014" exchange guide wire at its tip havinga lumen of 0.042" (1mm) and a spade like crater proximalto wire lumen marked by a radio opaque marker.  The aspiration system consist of 20cc syringe connected to the proximal hub for thrombus aspiration with aspiration rate of1cc / sec.All patients were given Clopidrogrel loading dose600 mg and Dispirin 300 mg in Emergency room before shifting to Cath. Lab.  Heparin was given as 10,000U incases where GPIIa IIIb receptor blockade was not used and3000 to 5000U of heparin in cases where aggrastat(tirofiban) was used as initial bolus of 10ug / kg over 3minutes. This was followed by maintenance infusion of 0.15ug/kg/min. in primary PCI and PCI in SVG and on operators discretion in cases of rescue PCI.In patients receiving standard PCI, after crossing with the guide wire, either the lesion was pre-dilated with aballoon before stent implantation or direct stentimplantation was done.Clinical data were collected in the emergency roomby a senior cardiologist. Pre and post intervention Electrocardiograms were analyzed.  STsegment elevationwas measured 20 milliseconds after the end of QRScomplex in lead I, avl and V1 to V6 for Anterior and lead II,III, avf, V5 and V6 for non-anterior MI.  ECG was defined as:1.Normalized if no residual STsegment elevation.2.Improved if residual STsegment elevation <70%.3.Unchanged if residual STSegment elevation >70% ofthat on first ECG4Ante grade coronary flow was rated using thrombolysis in Myocardial Infarction (TIMI) criteria.6Myocardial Blush Grade (MBG) was evaluated accordingto Vant Hof et al.7The primary end points of the study were STsegment resolution > 70% and MBG > 2 between patients selected for standard PCI and those to aspiration thrombus Export Catheter.  In post hoc analysis, a combination ofMBG > 2 and STR > 70% was used to compare the rate of patients with optimal reperfusion. Secondary end pointswere TIMI flow grade 3 and slow flow TIMI flow grade 2.The data was collected on a standardized data extraction form which recorded all the relevant variables forthe research objectives.  The data was edited and then entered on MS Excel program and analyzed using Epi-infoV6 .04b software.The numerical variables such as age, symptom toangiography time, procedure time and stent length was compared using the student's t-test.  The categorical variables such as gender, risk factors, site of MI, severity of stenosis, vessels involved and angiographic success, were confirmed using that of proportions or chi - square testwhere appropriate.  The TIMI flow grades, MBG and STsegment resolution variables were compared using the Chi-Square test.  In all the statistical tests, p-value of less than0.05 was considered to be statistically significant.

Results

Forty patients were selected for the study, 20 were assigned to the thrombus aspiration (TA) group and 20 tothe standard PCI (SPCI) group.  In the final analysis three cases were excluded from the TA group (two cases of saphenous venous graft and one case of rescue angioplasty).The baseline characteristics of the two groups are shown in Table 1.  The two groups were similar with regard sto age, gender, risk factors, site of MI, severity of the stenosis and vessels involved.  The pre-intervention TIMI flow grade was the same in both groups with all the patient shaving 0 or 1 TIMI flow grade.  The post-intervention TIMIflow grade was significantly improved for the thrombus aspiration group (p = 0.009), 13 out of 17 in the TA grouphad improved TIMI flow grade of 3 while only 6 out of 20in the SPCI group had improved flow grade of 3.Table 2 shows that the procedural characteristics regarding angiographic success, procedure time, number ofstents and total stent length were the same for both thegroups.  The MBG was the same for both the groups at pre-intervention, while was significantly improved for the TA group after intervention (p = 0.001), 13 (75%) out of 17 had

Table 1. Clinical Characteristics of Patients Undergoing Standard PCI and PCI with Thrombus Aspiration Export Catheter.

Variable

Thrombus

Aspiration

(n=17)

Standard PCI

(n=20)

p-value

Age (Years)

50+5.3

50.3+5.6

0.87

Gender:

     

Males

13(76%)

16(80%)

 

Females

4(24%)

4(20%)

0.89

Risk Factors:

     

Hypertension

9(53%)

8(40%)

0.43

Diabetes

4(53%)

4(20%)

0.89

Hypercholesterolemia

11 (65%)

14(70%)

0.73

Family History of IHD

6(35%)

7(35%)

0.99

Catheter.

Variable

Angiographic Success (%) Procedure time (min) (mean + sd) Number of Stents per Lesion Total Stent Length (mm) (mean +sd) Slow flow (%) Myocardial Blush Grade (Pre-Intervention):

0 1 2 3 Myocardial Blush Grade (Post-Intervention):

0 1 2 3 ST Segment Resolution: > 70% (%) < 70% (%)

 [(1)]

I    []Thrombus Aspimdon   •Standard PCI

MBG<2andSTR40% *MBG>20rSTR>70% MBG>2&STR>70%

Figure. Distribution of Patients According to the Combination of MBG and STR Showing Improved Outocme in the Thrombus Aspiration Group. * P-Value = 0.017.

MBG of 2 or more as compared to only 4 out of 20 in the SPCI group. The ST Segment resolution was the same in both groups (p = 0.16).

The outcome criteria were evaluated after combining MBG and ST resolution (STR) for the two groups. MBG > 2 and STR of > 70% were considered to be favourable (Figure 1). It was seen that 8 (47%) out of 17 patients in the TA group had improvements in both MBG and STR as compared to only 2 (10%) of 20 patients in the SPCI group.

Thrombus

Aspiration

(n=17)

Standard PCI

(n=20)

p-value

17(100%)

19 (95%)

0.35

35+ 11

45.5+ 19

0.16

1+0

1.2+0.4

 

16.8±6

20.2±7.9

0.15

1 (6%)

11 (55%)

0.001

11 (65%)

14(70%)

 

6 (35%)

6 (30%)

0.73

0-

0-

-

0-

0-

-

0 -

7(35%)

 

4(23%)

9(45%)

 

12 (65%)

3 (25%)

0.001

1 (35%)

2(5%)

 

8(47%)

5 (25%)

0.16

9(53%)

15 (75%)

 

 

Another 5 (29%) out of 17 patients in the TA group hadimprovement in either MBG or STR as compared to 5(25%) out of 20 patents in the SPCI group. The two criteria combined showed a significantly better outcome for TAgroup (p = 0.017) (Figure).

Discussion

 In patients with acute myocardial infarction restoration of epicardial blood flow has been shown to be the important predictor of clinical and angiographic outcome.8The goal of reperfusion therapy should be to restore not onlyepicardial patency but also improving myocardial tissue perfusion.9Anumber of intracoronary medications havebeen shown to improve myocardial perfusion. Wang et al.10showed that intracoronary administration of propranololprotects the myocardium during PCI reducing the incidence of myocardial infarction and improving short term clinicaloutcomes. Other studies11-13using intracoronary adenosine and verapamil have demonstrated a reduction in reperfusioninjury. These studies do not address intracoronary thrombus burden compared to pharmacological approaches. Previous studies have demonstrated that TIMI3 flow could be achieved in > 85% of patients using mechanical reperfusion strategies.14-16In our study TIMI3 flow in thrombus aspiration group was 75% at the end of PCI procedure. The results of this study showed that thrombus aspiration with export catheter is feasible with STEMI andimproves angiographic and ECG changes.  The rate ofpatients with MBG > 2 increased by 13% and STR > 70%increased by 8% in the aspiration catheter group comparedto standard PCI.Myocardial blush grade is an important predictor of infarct size and survival.7It is also a strong angiographicpredictor of mortality in patients with TIMI3 flow afterangioplasty.7,17There are a number of studies using thrombus extraction devices and distal protection devices demonstrating conflicting results in improving myocardial perfusion and patient outcome.16,18The data is comparable with the results reported byNapo damo et al19and by Francesco Burzotta et al20 but differ with the enhanced myocardial efficacy and recoveryby aspiration of liberated debris in the (EMERALD) trial21which showed that removal of thrombus with PercusurgeGuard Wire (Medtronic Inc.) did not result in improvementof myocardial reperfusion and reduced infarct size.  The distal occlusion protection implies abolition of coronary flow during PCI while thrombus aspiration usually improves ante grade flow and probably low risk of distalembolization.7Regarding composition of aspirated material, it was visualized only in eight patients out of seventeen in export aspiration catheter.  Very early data suggested that lowerfibrin levels are associated with better myocardialre perfusion.22There was failure of aspirated material in two SVGand one case of rescue PCI in our study.  Other data have shown to have significant improvement in myocardial blush grade with Guard Wire.23In the past primary angioplasty achieving a TIMI 3flow was the main objective for which different devices like balloon and stents were used in different centers ofPakistan.2,24Use of thrombus extraction export catheter has shown promising results in addition to TIMI 3 flow and improving myocardial blush grade.The limitation of this study is that it is a, non-randomized single centre study and follow up of these patients were not done for major adverse cardiovascular events (MACE) at 1 month and MACE and target lesion revascularization (TLR) up to 6 months. Large prospectivestudies are needed to observe the long term outcomes.

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