Study participants
Consecutive patients with STEMI undergoing primary percutaneous coronary intervention (PCI) using PCLeB within 12 h of symptom onset at our hospital from March 2014 to July 2020 were included in this study. STEMI was defined as prolonged chest pain (duration > 30 min) and ST-segment elevation > 1 mm in ≥ 2 adjacent leads. We excluded patients with (1) an infarct-related coronary artery with a thrombolysis in myocardial infarction (TIMI) flow grade of II or III, (2) grade III collateral circulation, (3) occlusion of the left main trunk, (4) serum creatinine levels ≥ 2.0 mg/dL, and (5) cancer as well as those who had undergone reperfusion using technically flawed PCLeB procedures (most often by undertrained operators).
Postconditioning protocol
Figure 1 depicts an overview of the PCLeB protocol. The duration of each brief reperfusion was extended from 10 to 60 s in a stepwise manner. At the end of each brief reperfusion, lactated Ringer’s solution (Lactec Injection; Otsuka Pharmaceutical, Tokyo, Japan) containing 28 mM lactate was injected into the culprit coronary artery (20 mL for the right coronary artery, 30 mL for the left coronary artery). To trap the lactate within the ischemic myocardium, a balloon was quickly inflated with low pressure at the site of the lesion. Each ischemic period lasted 60 s. After seven cycles of balloon inflation and deflation, full reperfusion was performed; subsequently, stenting was performed, thus completing the PCI.
Measurements
Serum creatine kinase and creatine kinase-MB levels were measured at 4-h intervals after reperfusion until they peaked. Serum C-reactive protein (CRP) levels were measured daily, and the peak value during the first 7 days after admission was recorded. Data from the patients with concomitant extracardiac inflammatory disorders were excluded from the analysis. Corrected TIMI frame counts in the culprit coronary arteries were measured after PCI completion in all patients.
We retrospectively collected chronic phase data for NT-proBNP levels from medical records. Although we excluded patients with serum creatinine levels ≥ 2.0 mg/dL, aged patients may also have masked renal insufficiency that affects NT-proBNP levels. We therefore excluded the NT-proBNP data of 14 patients aged ≥ 80 years from the analysis. Additionally, two patients aged < 80 years had not undergone measurement of NT-proBNP levels after discharge. Therefore, the analyses were performed after excluding these 16 patients. Since the timing of the measurements during follow-up visits was arbitrary, we tried to select data as close as possible to one year after STEMI, resulting in data acquisition dates ranging from six to 18 months (mean ± SD, 11.0 ± 2.8 months) after STEMI.
Outcomes
In-hospital and one-year mortality and re-hospitalization rates for heart failure within one year were evaluated.
This single center, interventional, uncontrolled study was approved by the ethics review boards of the Saitama Municipal Hospital, and all study patients provided written informed consent. All data are expressed as means ± SD.