To the Editor: I do not agree with Svilaas and colleagues (Feb.7 issue)1 that thrombus aspiration during percutaneous coronaryintervention (PCI) in patients who have myocardial infarctionwith ST-segment elevation improves clinical outcomes. In theirintention-to-treat analysis, neither the incidence of death,reinfarction, or target-vessel revascularization nor a combinationof these events was significantly different between the groupwith and the group without aspiration.
The authors' implication that aspiration thrombectomy is applicable"in a large majority" of patients who have myocardial infarctionwith ST-segment elevation is misleading. They suggest that sincematerial was aspirated in almost three fourths of the patients,the myocardial blush grade and clinical outcomes were correlatedacross groups, and the blush grade was higher in the aspirationgroup than in the conventional-PCI group, then, ipso facto,aspiration is widely applicable for the improvement of clinicaloutcomes. A recent meta-analysis of randomized trials showedthat distal-protection devices with PCI in patients who havemyocardial infarction with ST-segment elevation improved theblush grade without improving the rate of death at 30 days.2The current study results are consistent with these data. Thus,I would suggest caution in recommending the use of aspirationthrombectomy without first showing improvement in clinical outcomes.
Barry F. Uretsky, M.D. Sparks Health System Fort Smith, AR 72901 buretsky{at}sparks.org
References
Svilaas T, Vlaar PJ, van der Horst IC, et al. Thrombus aspiration during primary percutaneous coronary intervention. N Engl J Med 2008;358:557-567. [Free Full Text]
De Luca G, Suryapranata H, Stone GW, Antoniucci D, Neumann F-J, Chiariello M. Adjunctive mechanical devices to prevent distal embolization in patients undergoing mechanical revascularization for acute myocardial infarction: a meta-analysis of randomized trials. Am Heart J 2007;153:343-353. [CrossRef][Medline]
To the Editor: Svilaas and colleagues report on a large, randomized,controlled trial of thrombectomy in acute myocardial infarction.This single-center trial showed improvement in markers of myocardialreperfusion with thrombectomy. Meta-analyses of previous studieshave reached the same conclusions.1,2,3 Thus, we are concernedabout the conclusion that thrombectomy improved clinical outcomesin the Thrombus Aspiration during Percutaneous Coronary Interventionin Acute Myocardial Infarction Study (TAPAS) trial. At 30 days,the confidence interval crossed the unity line for all studiedoutcomes — namely, death, reinfarction, target-vesselrevascularization, and major adverse cardiac events. The authorsshow a gradient of improvement in clinical outcomes, with betterindexes of myocardial reperfusion in a pooled analysis of datafrom patients in both the thrombectomy group and the controlgroup. However, in the article, it is clear that there wereno significant differences in clinical outcomes between thegroups. The take-home message would be that improved reperfusiondoes not translate into fewer clinical events. Insufficientpower to show a clinical benefit may explain this finding.
François-Pierre Mongeon, M.D. Centre Hospitalier de l'Université de Montréal Montreal, QC H2W 1T7, Canada
Mark J. Eisenberg, M.D., M.P.H. Jewish General Hospital Montreal, QC H3T 1E2, Canada
Stéphane Rinfret, M.D., M.Sc. Centre Hospitalier de l'Université de Montréal Montreal, QC H2W 1T7, Canada s.rinfret{at}umontreal.ca
References
Kunadian B, Dunning J, Vijayalakshmi K, Thornley AR, de Belder MA. Meta-analysis of randomized trials comparing anti-embolic devices with standard PCI for improving myocardial reperfusion in patients with acute myocardial infarction. Catheter Cardiovasc Interv 2007;69:488-496. [CrossRef][Web of Science][Medline]
De Luca G, Suryapranata H, Stone GW, Antoniucci D, Neumann FJ, Chiariello M. Adjunctive mechanical devices to prevent distal embolization in patients undergoing mechanical revascularization for acute myocardial infarction: a meta-analysis of randomized trials. Am Heart J 2007;153:343-353. [CrossRef][Medline]
Burzotta F, Testa L, Giannico F, et al. Adjunctive devices in primary or rescue PCI: a meta-analysis of randomized trials. Int J Cardiol 2008;123:313-321. [CrossRef][Web of Science][Medline]
To the Editor: Svilaas et al. show that thrombus aspiration during primary PCI results in significantly better ST-segmentresolution and myocardial blush grades than conventional PCI.Such improvements in myocardial reperfusion with thrombus aspiration,as indicated by these end points, were also reported earlier,1,2but whether these results correspond to smaller infarcts orbetter outcomes has not been clarified.1,2,3,4 Myocardial infarctsize as evaluated by means of radionuclide myocardial imagingwas not reduced by thrombus aspiration.3,4 Similarly, the leftventricular ejection fraction, assessed by echocardiographyor radionuclide imaging, was not improved.2,3,4 Thus, as faras thrombus aspiration in acute myocardial infarction is concerned,improvements in ST-segment resolution and myocardial blush gradeare not directly connected to smaller infarct size and betterleft ventricular function. We are not treating electrocardiogramsor angiograms; we are treating patients. Whatever the resultsof ST-segment resolution or the myocardial blush grade mightbe, without direct proof of reduction of infarct size and improvementin left ventricular function, we should not routinely use thrombusaspiration, which requires additional time and cost.
Haruo Tomoda, M.D., Ph.D. Tokyo Heart Institute Tokyo 195-0061, Japan tokyoheart{at}abelia.ocn.ne.jp
Silva-Orrego P, Colombo P, Bigi R, et al. Thrombus aspiration before primary angioplasty improves myocardial reperfusion in acute myocardial infarction: the DEAR-MI (Dethrombosis to Enhance Acute Reperfusion in Myocardial Infarction) study. J Am Coll Cardiol 2006;48:1552-1559. [Free Full Text]
Napodano M, Pasquetto G, Saccà S, et al. Intracoronary thrombectomy improves myocardial reperfusion in patients undergoing direct angioplasty for acute myocardial infarction. J Am Coll Cardiol 2003;42:1395-1402. [Free Full Text]
Ali A, Cox D, Dib N, et al. Rheolytic thrombectomy with percutaneous coronary intervention for infarct size reduction in acute myocardial infarction: 30-day results from a multicenter randomized study. J Am Coll Cardiol 2006;48:244-252. [Free Full Text]
Kaltoft A, Bøttcher M, Nielsen SS, et al. Routine thrombectomy in percutaneous coronary intervention for acute ST-segment-elevation myocardial infarction: a randomized, controlled trial. Circulation 2006;114:40-47. [Free Full Text]
To the Editor: Svilaas and colleagues found that thrombus aspirationin the setting of myocardial infarction with ST-segment elevationreduces the risk of poor reperfusion from 26.3% to 17.1% (asmanifested by a myocardial blush grade of 0 or 1). Aspirationof thrombus improves reperfusion ostensibly by removing materialthat would otherwise embolize distally and cause microvascularobstruction. Although the principle of removing thrombus isintuitively appealing, it is difficult to understand how a catheterwith a lumen cross-sectional area of only 2.5 mm2 can extracta sufficient amount of thrombus from a large vessel (a 4-mmvessel has a cross-sectional area of 12.6 mm2). Did the authorsnotice that there was less benefit in larger vessels? If thebenefit was similar in large vessels, this might imply thatthrombus aspiration improves reperfusion by clearing a channelto facilitate direct stenting, which traps thrombus againstthe wall instead of removing it. This information would be usefulin devising strategies to further reduce poor reperfusion.
James L. Amato, Jr., M.D. Fayez E. Shamoon, M.D. Jacob I. Haft, M.D. Saint Michael's Medical Center Newark, NJ 07102 jlamatojr{at}yahoo.com
The authors reply: Our trial was designed to evaluate the effectof thrombus aspiration on myocardial reperfusion with the useof myocardial blush grade as the primary end point. The resultsshow beyond any reasonable doubt that thrombus aspiration improvesmyocardial reperfusion as assessed by blush grade and also byresolution of ST-segment elevation. The concern expressed bythe correspondents in the first three letters with respect toextrapolation of these results to clinical outcomes has beenaddressed, since the power of our study with respect to a surrogateprimary end point is a clearly stated limitation. We found animprovement in the clinical outcome, although it was not significantat 30 days. We observed that myocardial and electrocardiographicmeasures of reperfusion are strong predictors of the clinicaloutcome at 30 days; the relationship between these values suggestsa better clinical outcome with thrombus aspiration than withconventional PCI. The benefits of restoration of myocardialreperfusion might be seen in terms of a positive effect on leftventricular remodeling, with a significant effect on the lateclinical outcome rather than on the early outcome.1 Recent dataon 1-year mortality and reinfarction did show a significantbenefit with thrombus aspiration; these data provide supportfor our hypothesis.2
We are aware of meta-analyses evaluating embolic protectiondevices.3,4 Although an effort has been made to use strict selectioncriteria in these analyses, caution is needed in the interpretationof the results because of the heterogeneity documented. Thetrials included in these meta-analyses evaluated different typesof catheters, and inclusion criteria and the definition of variables,as well as antithrombotic regimens, varied markedly. In addition,bias may occur in pooling data from many small trials.5 Ourtrial is of value not only because of our results but also froma methodologic point of view. The device used in the study,a manual-aspiration catheter, is relatively simple, flexible,and nontraumatic, and its use does not require additional timeor cost. Furthermore, the study size and design — in particular,randomization before angiography, with few exclusion criteriaand with adjunctive pharmacologic treatment according to currentguidelines — make our data generalizable to a contemporarypopulation of patients with myocardial infarction with ST-segmentelevation.
With regard to the question of Amato et al. regarding vesselsize and treatment effect, in a subanalysis that was not prespecified,there was no difference in the primary end point of a myocardialblush grade of 0 or 1 between larger vessels (3.5 mm) and smallervessels. The blush grade was 0 or 1 in 44 of 209 patients withlarger vessels (21.1%) versus 35 of 257 with smaller vessels(13.6%) in the aspiration group (risk ratio, 0.68; 95% confidenceinterval [CI], 0.49 to 0.94) and in 67 of 216 with larger vessels(31.0%) versus 57 of 244 with smaller vessels (23.4%) in theconventional-angioplasty group (risk ratio, 0.58; 95% CI, 0.40to 0.85) (P=0.83 for heterogeneity). In interpreting this result,one should keep in mind that during continuous aspiration, thecatheter is being moved forward and backward through the infarct-relatedlesion, resulting in the "vacuuming out" of atherothromboticmaterial over a larger area than the internal lumen of the catheter.
In conclusion, we believe our trial provides important supportfor thrombus aspiration as the preferred initial step in angioplastyfor acute myocardial infarction.
Tone Svilaas, M.D. Felix Zijlstra, M.D., Ph.D. University Medical Center Groningen 9700 RB Groningen, the Netherlands t.svilaas{at}thorax.umcg.nl
for the TAPAS Investigators
References
De Luca L, Sardella G, Davidson CJ, et al. Impact of intracoronary aspiration thrombectomy during primary angioplasty on left ventricular remodelling in patients with anterior ST elevation myocardial infarction. Heart 2006;92:951-957. [Free Full Text]
Vlaar PJ, Svilaas T, van der Horst IC, et al. Cardiac death and reinfarction after 1 year in the Thrombus Aspiration during Percutaneous Coronary Intervention in Acute Myocardial Infarction Study (TAPAS): a 1-year follow-up study. Lancet 2008;371:1915-1920. [CrossRef][Web of Science][Medline]
De Luca G, Suryapranata H, Stone GW, Antoniucci D, Neumann FJ, Chiariello M. Adjunctive mechanical devices to prevent distal embolization in patients undergoing mechanical revascularization for acute myocardial infarction: a meta-analysis of randomized trials. Am Heart J 2007;153:343-353. [CrossRef][Medline]
Burzotta F, Testa L, Giannico F, et al. Adjunctive devices in primary or rescue PCI: a meta-analysis of randomized trials. Int J Cardiol 2008;123:313-321. [CrossRef][Web of Science][Medline]
Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ 1997;315:629-634. [Free Full Text]
3.5 mm) and smaller vessels. The blush grade was 0 or 1 in 44 of 209 patients with larger vessels (21.1%) versus 35 of 257 with smaller vessels (13.6%) in the aspiration group (risk ratio, 0.68; 95% confidence interval [CI], 0.49 to 0.94) and in 67 of 216 with larger vessels (31.0%) versus 57 of 244 with smaller vessels (23.4%) in the conventional-angioplasty group (risk ratio, 0.58; 95% CI, 0.40 to 0.85) (P=0.83 for heterogeneity). In interpreting this result, one should keep in mind that during continuous aspiration, the catheter is being moved forward and backward through the infarct-related lesion, resulting in the "vacuuming out" of atherothrombotic material over a larger area than the internal lumen of the catheter. 
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