Randomized study to assess the effect of thrombus aspiration on flow area in patients with ST-elevation myocardial infarction: an optical frequency domain imaging study—TROFI trial

With full interest, we read the article "Randomized study to assess the effect of thrombus aspiration on flow area in patients with ST- elevation myocardial infarction: an optical frequency domain imaging study --TROFI trial" by Onuma Y, et al [1]. In fact, the authors are to be congratulated for presenting such a piece of research that further expands the role of optical frequency-domain imaging (OFDI) in the evaluation of the immediate outcome of primary percutaneous coronary intervention (PPCI) in the setting of ST-segment-elevation myocardial infarction. The authors concluded that "no significant difference in flow area was found between PPCI with thrombectomy (TB) and PPCI without TB. The potential impact of OFDI guidance needs to be further elucidated in future studies." [1].

Yet, I have the following concerns about the design, methodology, and results of the study. First, the theme of measuring the minimal flow area inside the stent as a surrogate of epicardial coronary flow remains unclear. A larger minimal flow area does not necessarily correspond to a better epicardial coronary Thrombolysis In Myocardial Infarction (TIMI) flow grade, and is certainly far from reflecting myocardial tissue perfusion. During the process of stent deployment, a thrombus overlying the ruptured plaque might be displaced longitudinally along the length of the artery, or become emolized distally to cause microvascular obstruction - and no-reflow - without affecting the stent minimal flow area in either case. The prime value of TB is believed to be the improvement of myocardial tissue perfusion [2-5], improvement of left ventricular function and reduction of remodeling [4], and eventually, improvement of clinical outcome [5,6]. Second, the difference in minimal flow area between the two groups was 0.57 mm2. Since the study was 80% powered to detect a difference of 0.72 mm2, it was clearly underpowered to detect statistical significance of the observed difference of 0.58 mm2. Third, enrollment of 141 patients in 5 centers over a period of 10 months implies of an enrollment rate of 2.7 patients/center/month, which speaks of selection bias. No wonder that the incidence of in-hospital death or re- infarction in either group was 0%. Forth, although the minimal flow area was not significantly different between the two groups, the mean flow area (more representative of the whole stent length) was larger in the TB group compared with the non-TB group, with a trend toward statistical significance (8.71 ? 2.28 versus 8.04 ? 2.13 mm2, respectively, p=0.09) [1]. Fifth, the post-procedural minimal lumen diameter by quantitative coronary analysis was significantly greater, and the minimal stent area by OFDI was numerically higher in the TB compared with the non-TB group (p=0.01 and 0.16, respectively) [1]. Finally, in the subgroup with a heavy thrombus burden (pre-procedural thrombus grade 4 or 5), the minimal flow area by OFDI was significantly higher in the TB compared with the non-TB group (7.54 ? 2.3 versus 6.52 ? 1.97 mm2, respectively, p=0.043) [1]. It is in this subgroup that TB is more strongly indicated as an adjuvant to PPCI in patients presenting with ST-segment-elevation myocardial infarction.

References

1. Onuma Y, Thuesen L, van Geuns RJ, van der Ent M, Desch S, Fajadet J, Christiansen E, Smits P, Ramsing Holm N, Regar E, van Mieghem N, Borovicanin V, Paunovic D, Senshu K, van Es GA, Muramatsu T, Lee IS, Schuler G, Zijlstra F, Garcia-Garcia HM, Serruys PW; TROFI Investigators. Randomized study to assess the effect of thrombus aspiration on flow area in patients with ST-elevation myocardial infarction: an optical frequency domain imaging study--TROFI trial. Eur Heart J. 2013;34(14):1050-60.

2. Svilaas T, Vlaar PJ, van der Horst IC, Diercks GF, de Smet BJ, van den Heuvel AF, Anthonio RL, Jessurun GA, Tan ES, Suurmeijer AJ, Zijlstra F. Thrombus aspiration during primary percutaneous coronary intervention. N Engl J Med. 2008;358(6):557-67.

3. Burzotta F, Trani C, Romagnoli E, Mazzari MA, Rebuzzi AG, De Vita M, Garramone B, Giannico F, Niccoli G, Biondi-Zoccai GG, Schiavoni G, Mongiardo R, Crea F. Manual thrombus-aspiration improves myocardial reperfusion: the randomized evaluation of the effect of mechanical reduction of distal embolization by thrombus-aspiration in primary and rescue angioplasty (REMEDIA) trial. J Am Coll Cardiol. 2005;46(2):371-6.

4. Liistro F, Grotti S, Angioli P, Falsini G, Ducci K, Baldassarre S, Sabini A, Brandini R, Capati E, Bolognese L. Impact of thrombus aspiration on myocardial tissue reperfusion and left ventricular functional recovery and remodeling after primary angioplasty. Circ Cardiovasc Interv. 2009;2(5):376-83.

5. Mangiacapra F, Wijns W, De Luca G, Muller O, Trana C, Ntalianis A, Heyndrickx G, Vanderheyden M, Bartunek J, De Bruyne B, Barbato E. Thrombus aspiration in primary percutaneous coronary intervention in high-risk patients with ST-elevation myocardial infarction: a real-world registry. Catheter Cardiovasc Interv. 2010;76(1):70-6.

6. Vlaar PJ, Svilaas T, van der Horst IC, Diercks GF, Fokkema ML, de Smet BJ, van den Heuvel AF, Anthonio RL, Jessurun GA, Tan ES, Suurmeijer AJ, Zijlstra F. 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(9628):1915-20.

Conflict of Interest:

None declared