We thank Drs. Lou and Zhou for their comments (1) regarding our NHLBI-sponsored trial of postconditioning (PostC) (2). In our study, we observed that patients with ST-elevation myocardial infarction (STEMI) randomized to PostC at the time of primary percutaneous coronary intervention (PCI) experienced improved left-ventricular (LV) remodeling when evaluated at 12 months by cardiac magnetic resonance imaging (MRI) and that those patients had less microvascular obstruction (MVO) in the infarct zone compared to the Control group. However, these favorable effects on remodeling were not observed at the 3-month time point. The authors questioned whether the disparity in aspiration thrombectomy that favored the Control group (24 (42%) vs. 15 (23%) subjects; p= 0.034) was responsible for our failure to observe a similar improvement in remodeling at the 3-month time point.
The authors cited several trials demonstrating a benefit of aspiration thrombectomy on LV volumes (3) or MVO (4,5) during STEMI. Kondo et al. (3) compared 109 consecutive STEMI patients undergoing aspiration thrombectomy and PTCA to a historical control group of 86 patients undergoing primary PTCA. They observed that adverse LV remodeling defined as a > 20% increase in LV end-diastolic volume index, occurred significantly more frequently in the Control group.
In the EXPIRA Trial (4), 175 subjects with STEMI were randomized to aspiration thrombectomy followed by direct stenting vs. conventional PCI. A subgroup of patients (n=75) underwent cMRI at baseline and at 3 months. Subjects randomized to thrombectomy had similar infarct size and LV function but reduced MVO at baseline (3.7 vs. 1.9 g). At 3 months, those patients experienced a greater decrease in infarct size compared to Control. The MUSTELA Trial (5) randomized 208 STEMI patients to thrombectomy or standard PCI. At 3 months, there was no difference in infarct size between the two groups by MRI, but significantly fewer patients had MVO in the thrombectomy group (9 vs 20; p = 0.02). Similar to our findings, they observed no difference in LV volumes or function at 3 months. Unfortunately, they did not perform cMRI measurements at one year. Both of these studies are notable for aspiration thrombectomy being the initial intervention to establish reperfusion whereas in our trial, thrombectomy was mandated to occur after reperfusion with the PostC intervention.
To determine if our failure to demonstrate improved remodeling at 3 months was due to the reduced use of thrombectomy in the PostC group, we performed regression analysis to assess for any difference in the 3-month measurements for LV ejection fraction, LV end-diastolic volume, LV end- systolic volume, and infarct size (Table 1). All measurements were adjusted for the use of thrombectomy which was significantly higher in the control group. After adjustment, we found no significant differences in the 3-month measurements between the post condition and control groups.
Table.
Regression Analysis
| 3 Month Measurements |
Coefficient (SE) | P Value |
|---|---|---|
| LVEF | −0.428 (2.390) | 0.86 |
| LVEDV | −8.068 (9.522) | 0.40 |
| LVESV | −2.695 (6.877) | 0.70 |
| Infarct Size | 2.514 (3.440) | 0.47 |
LVEDV indicates left ventricular end-diastolic volume; LVEF, left ventricular ejection fraction; and LVESV, left ventricular end-systolic volume.
In conclusion, we failed to demonstrate a benefit of PostC on LV remodeling at 3 months even after accounting for the significant difference in aspiration thrombectomy between the PostC and Control groups. However, given that only 30% of our cohort underwent aspiration thrombectomy, it may not have been possible to demonstrate a benefit of this intervention. However, overall, the use of aspiration thrombectomy has plummeted (6) in the setting of STEMI as larger trials (7) and meta-analyses (8) have failed to show a short or long-term benefit of this therapy in the setting of STEMI.
Acknowledgments
Sources of Funding: NHLBI RO1-HL103927
Footnotes
Disclosures: None
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