Improved Outcome with AngioJet Thrombectomy During Primary Stenting in Acute Myocardial Infarction Patients with High-Grade Thro

Percutaneous coronary interventions (PCI) involving balloon angioplasty and stenting are effective in the treatment of acute coronary syndromes (ACS) including myocardial infarction (MI), but reduced coronary flow and distal embolization frequently complicate interventions when thrombus is present. Moreover, PCI in thrombus-containing lesions represents a clinical challenge to the interventionalist since thrombus is a predictor of adverse outcomes.^1,2 Distal embolization of thrombus, fibrin content and other atherosclerotic particulate matter can lead to a varying degree of consequences ranging from asymptomatic cardiac enzyme leak to flow-limiting microvascular obstruction, which may result in no reflow, abrupt occlusion, periprocedural MI, emergent coronary artery bypass graft (CABG) surgery and death.
The optimal treatment for thrombus-containing lesions has yet to be defined. Pharmacotherapy with anticoagulants and antiplatelet agents like glycoprotein (GP) IIb/IIIa antagonists has proven to be ineffective in the presence of angiographically evident thrombus.
New devices to treat thrombus-containing lesions include distal protection devices, such as the fixed-wire filter devices (FilterWire EZ™, Boston Scientific Inc, Natick, Massachusetts), the balloon-tipped wire of the PercuSurge system (GuardWire^®, Medtronic Inc, Minneapolis, Minnesota), and thrombectomy devices (AngioJet Rheolytic™ Thrombectomy device, Possis Medical, Inc., Minneapolis, Minnesota; X-sizer^® thrombectomy system, ev3 Medical Inc, Minneapolis, Minnesota.) and other manual aspiration devices.
The AngioJet rheolytic thrombectomy device is a catheter-based system for the removal of thrombus (Figure 1). It is a relatively novel thrombectomy device, specially designed to remove intravascular thrombus from coronary and peripheral arteries, by applying Bernoulli’s principle relating to a low-pressure zone in the region of a high-velocity jet.^3–9 The catheter is attached to a drive unit with a piston pump that generates a high-pressure pulsed flow rate of 10,000 psi at 60 cc/min through a hypotube. The hypotube ejects its saline at a loop in the catheter tip. The jets of high-velocity saline are directed back into an exhaust lumen. This creates a vortex (Bernoulli effect) that fragments the thrombus and aspirates the resulting microparticles through the same catheter, removing them from the body.

Methods

We studied all acute MI consecutive patients with ST-segment elevation within 24 hours who underwent PCI of the native coronary vessels at Mount Sinai Hospital from February 2002 to December 2003 (n = 233). Of these patients, those with cardiogenic shock (n = 13), thrombus grade 1–2 (n = 98) or no thrombus (n = 27) were excluded from the analysis. All remaining patients (n = 95) included in the study had angiographic thrombus grade between 3–5 (Table 1). AngioJet thrombectomy prior to stenting was done in 52 patients, while the remaining 43 patients underwent conventional stenting without AngioJet. Few of these patients were transferred from the outside institutions after failed thrombolysis.
Data collection. Demographic, procedural and follow-up mortality data were collected. Primary medical physicians were called and hospital records were analyzed. Mortality data were confirmed through social security death index.
Statistical analysis. Categorical data are expressed as number plus percentage and continuous values are expressed as mean ± standard deviation. Kaplan-Meier curves and log-rank tests were used to evaluate cumulative survival. Univariate and multivariate Cox regression models were used to identify independent predictors of survival. A p-value < 0.05 was considered significant. Analysis was performed using JMP 5.0 (SAS Inc, Cary, North Carolina).

Definitions

Procedural success. Residual diameter stenosis < 30% and thrombolysis in MI (TIMI) flow 2 after final treatment. Slow-flow or no flow. Delayed distal clearance of the dye in the absence of spasm, dissection or obstruction of the epicardial coronary artery. Spasm. Focal reversible narrowing.
Thromboembolism. Abrupt distal cutoff of a vessel or branch. Dissection. Intimal dissection zone graded according to NHLBI class from A to F. Thrombus grade. Defined from 1 to 6 as per TIMI criteria (Table 1).

Results

Baseline characteristics are shown in Table 2 and were not different between the two groups. The mean age of the patients was 64 ± 15 years, approximately 30% of the patients had diabetes mellitus, 75% had hypercholesterolemia, approximately 25% of the patients had a previous MI, and 40% had multivessel disease. GP IIb/IIIa inhibitor use was at the discretion of the interventionalist (was used in approximately 86% of cases).
Table 3 summarizes angiographic characteristics with longer lesions and higher pre-procedure stenosis and post-procedure TIMI flow in the AngioJet group. Procedural characteristics are shown in Table 4. Procedural success was attained in 96% of cases using AngioJet and 91% of conventional stenting (p = 0.31). Drug-eluting stents (DES) were used equally in both groups. Major complications, defined as death, re-MI or urgent CABG/re-PCI, were 2% in the AngioJet group and 9% in the conventional stenting arm. There was no urgent CABG in either treatment group. The AngioJet group showed a trend toward lower slowflow. The AngioJet group had significantly better TIMI myocardial perfusion (TMP) grade (mean), TMP 2/3, cTFC and post-procedure TIMI flow compared to conventional group. Follow-up results are shown in Table 5. Thirty-day MACE was 6% in the AngioJet group and 11% in the conventional stenting group (p = 0.12). At 1-year follow up, 5% patients in the conventional group required CABG vs. no need for CABG in the AngioJet group. Cumulative death and re-MI at 1-year follow up was twice higher in the conventional group compared to the AngioJet group (death 16% compared to 6%; p = 0.08; re-MI 9% compared to 4%; p = 0.32). Event-free survival was 89% in the AngioJet group and 72% in the conventional stenting group (p = 0.04) (Figure 2).

Discussion

In the current study, similar to prior published results, AngioJet thrombectomy appears to be safe and effective for the treatment of patients with acute MI in the presence of large thrombus burden or in-stent thrombosis.^10—13 However, AngioJet thrombectomy has come under recent scrutiny since the unexpected adverse outcomes associated with its use in the AngioJet Rheolytic Thrombectomy in Patients Undergoing Primary Angioplasty for Acute Myocardial Infarction (AiMI) trial.¹⁴ This trial is a multi-center, randomized, prospective trial comparing AngioJet thrombectomy followed by immediate definitive treatment (n = 240) with immediate definitive treatment in patients undergoing primary angioplasty (n = 240).
The primary endpoint is the final infarct size as assessed by single photon emission computed tomography (SPECT) imaging with 99 mTc Sestamibi at 14 days following the index procedure. The secondary endpoints include TIMI grade flow and frame count, TIMI myocardial perfusion blush grade, procedural complications, MACE and ST- segment resolution. Mortality rates were higher in the thrombectomy group (4.6% vs. 0.8%; p < 0.02), the infarct size was greater in those receiving thrombectomy (12.5 ± 12.1% vs. 9.8 ± 10.9%; p = 0.02) and the all-cause MACE rate was higher in those undergoing thrombectomy (6.7% vs. 1.7%; p < 0.01).
Among thrombectomy proponents, major barriers to the use of AngioJet include increased procedural time, the need to obtain venous access to insert a temporary pacemaker (when used in the right coronary or dominant left circumflex arteries due to the frequent occurrence of high-grade, hemodynamically significant heart block) and the absence of convincing data regarding benefits of thrombectomy.
In contrast to the AiMI data, our study showed favorable results for AngioJet, both at 30 days follow-up and at 1-year follow-up. This difference between our data and that from the AiMI trial could be explained by the thrombus size in the patients selected for both studies. While the AiMI trial enrolled patients with thrombotic burden of any size, with < 25% incidence of large thrombus (≥ 3 TIMI grade classification), patients enrolled in our study had only large thrombus (≥ 3). Therefore, it is reasonable to conclude that AngioJet thrombectomy is valuable in the setting of MI with large thrombus, but should not be used in cases with small or no thrombotic burden, possibly because it may cause distal embolization of small, non-visible, adherent thrombus and may add to procedural time.

Conclusion

AngioJet thrombectomy in the setting of acute MI complicated by a large thrombotic burden represents an important adjunctive technique allowing for rapid resolution of thrombus with quick reconstitution of flow and a decrease in the incidence of the no- or slow-reflow phenomenon. Our study proved that AngioJet thrombectomy for large thrombotic lesions in acute MI improved the infarct-related artery flow as measured by the cTFC, TMP blush grade and TIMI flow. This beneficial effect was translated into a trend toward lower 1-year mortality and higher event-free survival at 1 year.

References

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