This single-center retrospective survey included all patients with STEMI admitted to our medical center from January 22, 2020 (the start time of modified CPC operating process implementation) to April 30, 2020 (after lifting the lockdown in Wuhan), and patients who were diagnosed with STEMI and underwent PPCI in our hub during the corresponding time period of previous year (January 22 to April 30, 2020) were enrolled as a control group. Patients included in this analysis met the following criteria: ① patients who were clinical diagnosed as acute myocardial infarction with persistent ST-segment arch-like elevation in at least two contiguous electrocardiogram (ECG) leads or new bundle branch blocks (ischaemic repolarization patterns), together with rise of cardiac troponin (cTn) values with at least one above the 99th percentile of the upper reference limit [12]; ② all those STEMI patients with complete clinical records and follow-up data who received PPCI in our medical center (including percutaneous coronary balloon dilation, thrombus aspiration and stent implantation). The exclusion criterions were set as follows: ① patients with incomplete clinical data; ② non-ST segment elevation acute coronary syndrome (NSTE-ACS); ③ Infarct-related artery (IRA) recanalization or with a functional collateral supply, or triple-vessel disease requiring bypass surgery.

This research was approved by the Medical Ethics Committee of General Hospital of Central Theater Command and followed the principles of Declaration of Helsinki. Informed consent was obtained from all registered patients before discharge to access their anonymous clinical data.

To minimize the possible nosocomial cross-infection of SARS-COV-2, we formulated and implemented a detailed protocol for CPC as summarized in Fig. 1. For patients visiting during the outbreak, screening for COVID-19 was conducted upon arrival at the CPC including epidemiological history tracing, body temperature monitoring, and chest imaging examination. In addition, SARS-COV-2 nucleic acid testing was required as soon as possible except for patients in need of emergent reperfusion therapy, and all patients with emergent diseases were managed as suspected COVID-19 cases in our hub (isolated in a single-bed unit) until the reporting of nucleic acid detection results. All confirmed patients with COVID-19 were transferred to the dedicated quarantine ward with negative-pressure ventilation. During COVID-19 outbreak, the overall principles of our CPC were epidemic prevention and control as top priorities, and all efforts should be taken to ensure timely reperfusion for STEMI patients. PPCI remained the preferred reperfusion strategy if feasible for STEMI patients with uncertain or negative COVID-19 status (without suspected symptoms and close contact history). If the patient with STEMI was confirmed or suspected SARS-COV-2 infectious pneumonia and fibrinolysis was not contraindicated (within the time window of 12 hours), thrombolytic therapy then became the first-line strategy, except for those with high risks of bleeding or disseminated intravascular coagulation (DIC). For SARS-COV-2 positive high-risk patients with hemodynamic instability or fatal arrhythmias associated with STEMI, PPCI remained the first-line choice.

Fig. 1.

During the COVID-19 outbreak, primary percutaneous coronary intervention was performed under third-grade protection in the negative-pressure catheter lab of our center for patients with confirmed or uncertain status of SARS-COV-2 infection.

All health-care workers who engaged in the interventional (or other aerosol-generating) procedures should be totally protected under the third-grade PPE (including disposable cap, work clothes, double gloves, single-use protective clothing, N95 or better particulate protective masks or powered air filter respirator, protective facial screens or goggles, protective boots, water-proof disposable gown and shoe covers, quick-drying hand disinfectant) [13]. Medical staff who generally contacted with confirmed or suspected patients such as transferring or conservative treatment were protected under grade 2 PPE (including disposable cap and gloves, work clothes, single-use protective clothing, N95 respirator, protective facial screens or goggles, disposable shoe covers, quick-drying hand disinfectant). Grade 1 protection (including disposable cap and gloves, surgical mask or N95 respirator, work clothes) applied to staff in clean or transition zone of emergency department. All associated staff completed pre-training on the correct and appropriate use of PPE to mitigate the risk of nosocomial cross-infection (as shown in Fig. 1).

Patients admitted to our CPC outside the COVID-19 pandemic period were treated in accordance with the routine protocol of Chinese Society of Cardiology in which PPCI was recommended as the first-line treatment strategy for STEMI patients [14].

For patients with confirmed or uncertain status of COVID-19 infection receiving emergent PPCI, pre-established protocols to prevent cross-contamination between health-care staff and patients were necessary, which included preoperative preparation, peri-operative management, and postoperative terminal disinfection.

1) Preoperative preparation: ① Notify the staff of CCL receiving patients with confirmed/suspected COVID-19 infection. ② Open the dedicated pathway for the movement of possible COVID-19 positive patients and close the remaining channels on both sides of the CCL. ③ Turn on the negative-pressure ventilation device of CCL. ④ Provide double-layer disposable sterile cover for all the equipment used during the interventional procedure such as C-arm angiographic system and operative bed, etc. ⑤ Remind the patients without dyspnea to wear a surgical mask during the seamless transport, and only the staff involving in the operation remained in the CCL and equipped with third-grade PPE.

2) Peri-operative management: ① Keep all the gates of CCL closed and post COVID-19 signage to prevent the entry of unrelated staff. ② Ensure adequate supplies and equipment in the dedicated counter for COVID-19 and avoid staff entering or leaving the CCL during the operation (before changing PPE). ③ The operation should be as simple and gentle as possible to prevent blood or other body fluids from splashing and causing cross-contamination, whilst maintaining the best clinical outcome for STEMI patients.

3) Postoperative management and terminal disinfection: ① The cathlab staff doffed the outermost layer protective clothing and retained the grade 2 PPE to transfer patients to a dedicated isolation care unit for further treatment and SARS-COV-2 nucleic acid testing. If the patients were tested positive after the operation, they would be transferred to quarantine ICU designated for COVID-19 patients, and patients would be treated in the coronary care unit (CCU) or single-bed ward if tested negative. ② Steps for operating staff removing PPE: first take off gloves in the operating room, and then quickly wash hands and wear new gloves. Next, take off goggles or facial screens. After hand disinfection again, take off the protective clothing and foot covers, and placed them in the yellow medical trash collection bags. After entering the buffer (transition) region, doff radio-protective lead clothe and caps into the dedicated container. Replace surgical masks and then enter the clean region where staff could take a shower and change work clothes before leaving the CCL. ③ vTerminal disinfection of CCL and dedicated pathway: the operating room, control room and transfer pathway would be sprayed with hydrogen peroxide (3%) for air disinfection after the interventional operation. The contaminating material on the floor, wall, instruments or other surfaces should be completely removed and wiped with 2000 mg/L effective chlorinated disinfectant solution for 30 minutes before wipe off with clean water. Finally, CCL and dedicated pathways would be sterilized by ultraviolet radiation.

All clinical data were collected by screening the electronic medical system of our hub. The primary objective of this respective study was to evaluate the change in key time points of reperfusion therapy for STEMI patients during the COVID-19 period compared with the control period, including the median time from symptom onset to first medical contact (SO-to-FMC), the median time from first medical contact to entering cardiac catheterization laboratory (FMC-to-CCL), the door to balloon time (D2B), etc. Secondary objectives of the present study included length of hospital stay, PPCI-related data, clinical adverse events and outcomes. In addition, all patients were followed up within a six-month period through the outpatient system, WeChat, telephone, etc. Major adverse cardiovascular events (MACE) within 6 months after discharge was defined as malignant arrhythmia, re-admission due to heart failure, recurrent myocardial infarction or angina, and all-cause death.

Continuous variables were expressed as median and interquartile ranges (1${}^{st}$ and 3${}^{rd}$ quartiles), and compared by Mann-Whitney U test. Categorical variables were expressed as frequencies (percentages), and compared using the Chi-square test or Fisher’s exact test as appropriate. A two-tailed P value less than 0.05 was considered as statistically significant. All statistical analyses were performed using SPSS (version 26.0 for Windows; SPSS Inc., Chicago, Illinois, USA).

A total of 62 patients with the diagnosis of STEMI receiving PPCI in our hub were included in this study. Among them, 21 patients visited during the COVID-19 outbreak period and none of them tested positive for SARS-COV-2. In the same period of 2019, 41 patients presented to our hub underwent PPCI for STEMI in our hospital. As expected, the number of patients receiving PPCI significantly reduced during the study period as compared to control period. Age, gender, sites of infracted lesions on electrocardiogram (ECG), cardiovascular risk factors, and route of hospital admission were similar between the COVID-19 era group and the control group (P $>$ 0.05). Baseline demographic and clinical characteristics of included patients are summarized in Table 1.

As shown in Table 2, the median time from symptom onset to first medical contact (SO-to-FMC) in the COVID-19 era group was nominally longer as compared to the control group (4.35 h vs. 2.58 h, P = 0.258), and the proportion of patients with SO-to-FMC time $>$ 6 h was significantly higher in the COVID-19 era group than the ratio observed in 2019 (47.6% vs. 22.0%, P = 0.038). The median time from first medical contact to entering cardiac catheterization laboratory (FMC-to-CCL), time from entering cardiac catheterization laboratory to puncture (CCL-to-P) and the door to balloon time (D2B) in the COVID-19 era group were significantly longer compared with the control group (65.0 min vs. 49.0 min, P = 0.020; 10.0 min vs. 8.0 min, P = 0.016; 87.0 min vs. 70.0 min, P = 0.016, respectively), which were possibly related to the reorganization of CPC operating procedures. No significant differences in other key time nodes were observed between the two groups.

The characteristics of PPCI were shown in Table 3. There were no significant differences in puncture approach, infarct-related artery (IRA), Thrombolysis in Myocardial Infarction (TIMI) flow grade before and after the procedure, and stent type between the two groups (P $>$ 0.05). A final TIMI flow grade III was achieved in all patients (62/62, 100%) of the two groups after the interventional procedures, which indicated that reorganization of CPC had no significant impact on the opportunity for STEMI patients to receive effective reperfusion therapy.

The in-hospital adverse events and related indicators were shown in Table 4. There was no significant difference in the proportion of heart failure (Killip classification $\ge$ II) and arrhythmia during hospitalization between the two groups (P $>$ 0.05). However, the ratio of cardiogenic shock was significantly higher in the COVID-19 era group (47.6% vs. 19.5%, P = 0.021), which may be due to delayed reperfusion. The ratio of thromboembolic events was numerically higher in the COVID-19 era group compared with control group, which did not reach statistical significance (14.3% vs. 2.4%, P = 0.108). Transthoracic echocardiographic findings during hospitalization were similar between two groups (partial parameters were not measured in some patients as shown in Table 4), and the median levels of serum N-terminal prohormone of B-type natriuretic peptide (NT-proBNP), Creatine kinase-MB (CK-MB), and cardiac troponin T (cTnT) were numerically higher in the COVID-19 era group, but no statistically significant differences were observed (all P values $>$ 0.05). No patient died during the initial hospitalization and the length of hospital stay was similar between both groups (median 12 days, P = 0.863).

There was no patient loss to follow-up during 6-month postoperative period. Patients admitted in 2020 had a numerically higher proportion of overall MACE after discharge as compared to control group (14.3% vs. 2.4%), but no statistically significant differences were observed (P = 0.211). During the COVID-19 era period, 3 patients (14.3%, 3/21) were re-admitted with persistent ventricular tachycardia, recurrent heart failure and unstable angina respectively. In the control group, 1 patient (2.4%, 1/41) was re-admitted for recurrent unstable angina by 3 months after discharge. All readmitted patients recovered after further conservative treatment and there were no disease-related mortalities during the follow-up period. MACE data after discharge were shown in Table 5.

All relevant medical staff and STEMI patients were tested negative for the nucleic acid of SARS-COV-2 via reverse transcription-polymerase chain reaction (RT-PCR) during the study period. There was no in-hospital cross-infection of COVID-19 after the reorganization of our hub.