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Original article
An analysis of the door-to-balloon time in STEMI patients in an underdeveloped area of China: a single-centre analysis
  1. Zi-Xiang Yu1,2,
  2. Xin Shen1,2,
  3. Yi-Tong Ma1,2,
  4. Yi-Ning Yang1,2,
  5. Xiang Ma1,2,
  6. Xiang Xie1,2
  1. 1First Department of Coronary Heart Disease, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, China
  2. 2Xinjiang Key Laboratory of Cardiovascular Disease Research, Urumqi, Xinjiang, China
  1. Correspondence to Professor Yi-Tong Ma, First Department of Coronary Heart Disease, First Affiliated Hospital of Xinjiang Medical University, No.1 Li-Yu-Shan Road, Urumqi, Xinjiang 830054, China; myt-xj{at}163.com

Abstract

Objectives This study was conducted to break the door-to-balloon time (DTBT) into constituent elements, and compared which components prolonged markedly. We identified the factors that significantly prolonged the DTBT in an underdeveloped area of China.

Methods The patients were included from January 2008 to December 2010 in 301 consecutive patients presenting with STEMI in our hospital. We analysed the components of total DTB times, such as ‘Diagnosis time’, ‘Cardiologist consultation time’, ‘Explain the patient's condition time’, ‘Transferring time’, ‘Preparation of the catheterisation laboratory (CL) time’, and determined which factors significantly prolonged the DTBT potentially.

Results The median DTBT of all patients was 134 (98–186) min. The group was divided by the DTBT into two: ≤120 min and >120 min. In the ≤120 min group, more patients (68.1%) presented to our hospital during working hours (p=0.000), whereas in the >120 min group, more patients (63.2%) presented out of hours (p=0.000). More patients (49.3%) presented when the interventionist was on site (p=0.000) in the ≤120 min group. In the >120 min group, the times for consultation by the cardiologist and explaining the patient's condition to the family prolonged markedly, as compared to the ≤120 min group (p=0.000) when the interventionist was off-duty (OR=4.050, p=0.000) and presentation during non-working hours (OR=3.334, p=0.000) were significant predictors of >120 min DTB times.

Conclusions In our centre, the time of consultation by the cardiologists and explaining the patient's condition to the family accounted for most of the delay in reperfusion. A lack of interventionists usually resulted in a delay during non-working hours in the CL. Several measures should be taken involving asking emergency department physicians to awake CL directly, sending the patients’ information to the cardiologists, popularising medical knowledge to the citizens, and increasing the numbers of interventionists qualified to carry out primary percutaneous coronary intervention, should be developed to shorten the DTBT.

  • acute coronary syndrome
  • cardiac care, acute coronary syndrome
  • cardiac care, treatment

https://doi.org/10.1136/emermed-2012-201707

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    Introduction

    Door-to-balloon time (DTBT; defined as the time from when the patient arrives at the hospital and the first inflation of an angioplasty balloon in the occluded coronary artery) is a critical determinant for the treatment of ST-elevation myocardial infarction (STEMI). Current guidelines from the American College of Cardiology/American Heart Association (ACC/AHA) recommend a goal of ≤90 min for the DTBT.1 Nevertheless, many hospitals have a DTBT >90 min.2–,4 Before creating strategies for reducing the DTBT in acute myocardial infarction (AMI), existing problems should be identified. Studies3 have shown that hospitals in different countries have implemented several strategies to reduce the DTBT, with varying levels of success.5–8

    We collected the data to break DTBTs into constituent elements, and determined which components prolonged so markedly that the total DTBTs prolonged correspondingly, making a comprehensive analysis of the impact factors of DTBT in our hospital.

    Materials and methods

    The study protocol was approved by the ethics committee of the First Affiliated Hospital, Xinjiang Medical University (Urumqi, Xinjiang, China). All subjects provided written informed consent to be included in the study.

    Local conditions and hospital setup

    The Xinjiang Uyghur Autonomous Region is in western China. It is a large, underdeveloped area, spanning over 1.6 million km2 and taking up one-sixth of the territory of China. The First Affiliated Hospital of Xinjiang Medical University is a tertiary-care general hospital with ≈2 000 beds, which is one of the largest hospital in the west of China. Our hospital has four catheterisation suites. These suites can provide angiography for ≈5,000 cases and primary percutaneous coronary intervention (PPCI) for ≥210 cases per year. However, we have only five experienced cardiac interventionists.

    Patients and indications for PPCI

    A total of 301 consecutive STEMI patients who underwent PPCI between Jan 2008 and Dec 2010 in our hospital were identified. Patients were included in the study if they satisfied the diagnostic criteria of STEMI set by the ACC/AHA1; cases who did not were excluded. All patients accepted insertion of drug eluting stents. We did PPCI on the patients with symptom less than 12 h. If a patient complaining of chest pain presented to our hospital, a physician from the emergency department (ED) made the primary diagnosis and asked for assistance from a cardiologist. The cardiologist contacted the catheterisation laboratory (CL) after confirming the diagnosis. After obtaining written informed consent, a loading dose of aspirin (300 mg) and clopidogrel (300 mg) was given. The patient was then transferred to the treatment centre as soon as possible (figure 1).

    Figure 1
    Figure 1

    Process of presentation of patients with STEMI for PPCI in our hospital. The five major components of the door-to-balloon time during the process are shown. ED, emergency department; CL, catheterization laboratory; PPCI, primary percutaneous coronary intervention.

    Data collection

    The patients were registered by a designated resident or nurse who then recorded the baseline data, and another doctors analysed the components of DTBT. The basic data were: age; sex; body mass index; heart rate; cardiovascular risk factors (hypertension, diabetes mellitus, cholesterol level, smoking, percutaneous coronary intervention, coronary artery bypass grafting); comorbidities (myocardial infarction, chronic renal dysfunction); slight chest pain; creatine kinase myocardial isoenzyme MB (CK-MB) value; and in-hospital mortality. The DTBT comprised five components, that is, the time of (1) diagnosis in the ED (the time of the primary diagnosis by ED physicians; (2) consultation by the cardiologist (from when the cardiologist had the consultation to making the final diagnosis; (3) explaining the patient's condition to the family (from when the cardiologist explained the condition to the family until the family agreed to have PPCI and signed the consent form; (4) transfer to the CL in hospital; (5) preparation of the CL during working hours and non-working hours. We also analysed other variables that influenced DTBT, that is, patients presenting to hospital during working hours; patients presenting to hospital out of hours; interventionist qualified to carry out PPCI on site.

    Each component was recorded by a designated resident or nurse. The time when the patients presented to our hospital was also recorded. All data were summarised and put into the database after quality control by two specially assigned resident physicians with 3 years experience of such work in our hospital.

    Statistical analysis

    SPSS V.16.0 was used for statistical analyses (SPSS, Chicago, Illinois, USA). Categorical data are percentages and compared using the Pearson χ2 test. Continuous data are the mean±SD or median±IQR, comparisons between groups were performed using independent t test or Mann–Whitney U test for continuous variables. The data binary logistic regression of DTBT were used with significant univariate variables to determine factors that prolonged the DTBT.

    Results

    Clinical characteristics

    The present study involved 301 patients with a mean age of 62±12 years (±SD). The mean age was 61.7±12.1 years (±SD) in the ≤120 min group and 60.6±11.5 years (±SD) in the >120 min group. History was similar in the two groups. Other baseline characteristics are listed in table 1. At presentation, five patients (3.6%) in the ≤120 min group had slight chest pain, whereas 34 patients (20.9%) in the >120 min group had the same complaint (p=0.000). Ten patients (3.3%) died before discharge from hospital.

    View this table:
    Table 1

    Baseline characteristics of patients

    The values and components of the DTBT

    The median DTBT for 301 patients was 134 (IQR from 98 to 186) min. The median DTBT in the ≤120 min group was 96 (60 to 108) min, as compared with 178 (149 to 243) min in the >120 min group. Table 2 and figure 2 show the main components of the DTBT in the two groups. In the >120 min group, the time for consultation with the cardiologist (p=0.000) and the time in explaining the patient's condition to the family (p=0.000) were significantly prolonged. There were no significant differences in the time of diagnosis in the ED and the time of transfer to the CL between the two groups (p>0.05).

    View this table:
    Table 2

    Components of the door-to-balloon time in minutes

    Figure 2
    Figure 2

    Components of the door-to-balloon time in minutes.

    Factors influencing the DTBT

    Table 3 shows the proportions of patients presenting at different times between the two groups. In the ≤120 min group, more patients (68.1%) presented to our hospital during working hours, whereas in the >120 min group more patients (63.2%) presented during non-working hours. Presentation during working hours could significantly shorten the DTBT (p=0.000). Also, more patients (49.3%) presented to our hospital when the interventionist qualified to carry out PPCI was on site in the ≤120 min group, whereas fewer patients (19.6%) presented if the qualified interventionist was not on site in the >120 min group. That is, having an interventionist qualified to carry out PPCI on site usually shortened the DTBT (p=0.000).

    View this table:
    Table 3

    Proportions of patients with different variables between the two groups

    Using binary logistic regression analyses(DTBT≤120 min or >120 min) with significant univariate variables showed that typical symptom (OR=0.124, 95% CI 0.043 to 0.358, p=0.000), if an interventionist qualified to carry out PPCI was not on site (OR=4.050, 95% CI 2.285 to 7.177, p=0.000), and presentation during non-working hours (OR=3.334, 95% CI 1.973 to 5.635, p=0.000) were significant predictors of a DTBT >120 min (table 4).

    View this table:
    Table 4

    Binary logistic regression analyses of >120 min door-to-balloon time

    Discussion

    The DTBT is an important index of quality of PPCI in subjects with STEMI. Very poor outcomes are usually associated with a long delay in the DTBT.9 ,10 The ACC/AHA recommend a goal of ≤90 min for the DTBT because patients with STEMI can derive the most benefits from PPCI at this time.11 ,12 However, recent data have shown that this time is achieved in fewer than 50% patients with STEMI.2 Whether in China or abroad, there is considerable disparity between treatment guidelines and clinical practice. According to a recent report in a multicentre study in China, the median DTBT time was 135 min.13 Our hospital is one of the largest tertiary care centres in the Xinjiang Uyghur Autonomous Region. The economy and culture are not balanced in the area. However, the present study showed that the median DTBT in our hospital was 134 min. Too much time was spent for the consultation with the cardiologist as well as for explaining the patient's condition to the family. Physicians in our hospital might not be sufficiently aware of the importance of the DTBT in PPCI. Another possible reason was that one cardiology doctor attended to the whole hospital consultation (including ordinary and emergency). The doctor was busy going from one department to another, spending a lot of time on the road. In the >120 min group, the median time for the cardiologist to consult was 45 min, because most of the time the cardiologist was too busy to arrive at the ED promptly. Recent studies have shown that if ED physicians determined a patient had STEMI and directly contacted the CL without involvement of a cardiologist for consultation with the patient then the DTBT could be significantly reduced.14–18 Therefore, ED physicians could bypass the cardiologist for consultation and directly contact the CL to dramatically reduce the DTBT time. A survey of 365 hospitals in the USA showed that only 23% of hospitals during the weekdays and 27% of hospitals at night or on weekends used this strategy.3 However, most hospitals in China (including ours) involve a cardiologist in the decision to contact the CL, however, this measure might lead to more false positive diagnoses and an increase in time potentially. An alternative would be to contact CL and the cardiologist in parallel. Another good way was to send the patients’ information, such as history, level of CKMB and ECG to the cardiologist as mobile phone messages, the cardiologist could decide whether to do PPCI or not quickly.

    Another factor that significantly delayed the DTBT was explaining the patient's condition to his/her family. Doctors must obtain the patient's family's permission before doing the operation under the laws of China. In the >120 min group, the median time for explaining the patient's condition to the family was 68 min, it was a long time, that is, we spent a long time explaining the condition to the family. In our remote area, the absence of publicity has resulted in a lack of awareness of the importance of reperfusion in STEMI. The patients and their families did not even know the AMI, and knew less about PPCI. However, such awareness may be better than that in ‘developing’ countries. According to Chinese customs, core family members often make the important decisions. Also, physicians have to wait for the families of patients to sign consent forms under Chinese law. To some extent, the time depended on family members’ education level. Widely popularising the medical knowledge and the benefit of early reperfusion are very important to improve awareness in Chinese citizens.

    More than 1000 hospitals in China are equipped with angiography facilities, but nearly half the hospitals lack operators who are qualified to undertake PPCI independently.19 This problem was very acute in the present study. In the present study, if an interventionist qualified to carry out PPCI was not on site (OR=4.050, p=0.000), and presentation was during non-working hours (OR=3.334, p=0.000), these were significant predictors of a DTBT >120 min. During working hours, we had five interventionists qualified to carry out PPCI, and almost all of them were on site so that patients with STEMI could undergo PPCI. During non-working hours, they were not on site, and cardiologists who were not qualified to carry out PPCI were on duty. This trend was in accordance with the time of preparation of the CL during working/non-working hours because delay was caused by trying to contact or waiting for interventionists qualified to carry out PPCI. Studies outside China have reported that presentation during non-working hours was an independent predictor of the DTBT,20 ,21 and a protocol called ‘Code STEMI’ has been successful in achieving a reduced DTBT during non-working hours.22 In our hospital, increasing the numbers of interventionists qualified to undertake PPCI might change this situation. Atypical symptoms also delayed the DTBT.23 Patients who did not have typical symptoms might not consult with a physician until the symptoms worsened, so they missed the chance of reperfusion and their DTBT increased. Consequently, raising public awareness about presenting to hospital promptly as soon as symptoms occur is very important for successful reperfusion.

    To our great relief, strategies for improving transfer to reduce the DTBT time have been implemented in our hospital. Our hospital has set up a ‘Transfer Centre’ which has specialised staff to transfer patients. Although transfer problems remain,21 ,24 the situation has improved in many hospitals in China.

    Limitations

    This was a single-centre study, and the cohort was small compared with that seen in multicentre studies. This study was in a population in a western China hospital and might not represent the situation in the rest of China.

    Conclusions

    Contacting a cardiologist for consultation with the patient, explaining the patient's condition to the family, and an absence of an interventionist qualified to carry out PPCI were the major causes of delay in the DTBT. Strategies involving asking ED physicians to contact the CL directly, sending the patients’ information to the cardiologist as mobile phone messages, enhancing that attending physicians know the importance of early reperfusion, popularising medical knowledge to the citizens, and increasing the numbers of interventionists qualified to carry out PPCI should be developed to shorten the DTBT.

    Acknowledgments

    The authors acknowledge the support of the staff of the catheterisation lab. We thank the many general practitioners involved in this study who contributed their time and expertise to the care of patients and the collection of data.

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    Footnotes

    • Contributors Conception and design of the study: Y-TM. Acquisition of data: Z-XY, XS, Y-NY. Analysis and interpretation of data: XM, XX. Drafting the article: Z-XY, XS. Revising draft critically for important intellectual contents: Z-XY, XX. Final approval of the manuscript: Y-TM.

    • Funding This work was supported by a grant from the Great Technology Special Item Foundation of Xinjiang, China (grant number 200733146-3).

    • Competing interests None.

    • Ethics approval The study protocol was approved by the Ethics Committee of the First Affiliated Hospital, Xinjiang Medical University (Urumqi, Xinjiang).

    • Provenance and peer review Not commissioned; externally peer reviewed.