Time delays in instituting thrombolysis in acute myocardial infarction - a Singapore perspective

Transcription

1 Hong Kong Journal of Emergency Medicine Time delays in instituting thrombolysis in acute myocardial infarction - a Singapore perspective M Tiru and SH Goh The reduction of mortality from acute myocardial infarction has been achieved mainly through the use of thrombolysis. In large scale studies, mortality and the extent of myocardial salvage are directly related to how early thrombolysis or reperfusion is instituted. This study was done to highlight the factors resulting in time delays that need to be targeted for change: (a Pre-hospital delays (recognition of symptoms suggesting an acute myocardial infarction and the presentation to the A&E Department; (b Delays that occur within the A&E Department; and (c Delays after leaving the Accident & Emergency Department. We identified the areas contributing to significant delays in each of these areas with a view of proposing that a subgroup of these patients may be identified for a fast track approach in initiating thrombolysis within the Accident & Emergency Department. (Hong Kong j. emerg.med. 2000;7: Keywords: Delays, myocardial infarction, thrombolysis, pre-hospital, Accident & Emergency Introduction The reduction of mortality from acute myocardial infarction has been achieved mainly through the use of aspirin, beta blockers, angiotension converting enzyme (ACE inhibitors, primary angioplasty, and thrombolysis. 1 In significant large scale clinical studies, 2-7 mortality and the extent of myocardial salvage are directly related to how early thrombolysis or reperfusion is instituted. The American National Heart Attack Alert Program has highlighted 3 areas of delays that need to be targeted for change. (a Patient delays, that is, patient recognition of and the action related to symptoms of unstable angina pectoris/myocardial infarction, (b prehospital delays, that is, delays between recognition and hospital arrival, (c inhospital delays, that is, once the patients arrive in Correspondence to: Mohan Tiru, Registrar Changi General Hospital, Accident & Emergency Department, 2 Simei Street 3, Singapore mohant@mbox3.singnet.com.sg SH Goh, Consultant hospital. The American Heart Association has recommended that patients attending to the Accident & Emergency (A&E Department with symptoms suggestive of an acute myocardial infarction (AMI, together with characteristic hyperacute ST elevation on 12 lead electrocardiogram (ECG be administered intravenous (IV thrombolysis within 30 minutes of arrival in hospital, after the exclusion of contraindications. In Singapore, we have been slow in adopting the strategy of thrombolysis at the A&E Department. Thrombolytics are only being administered after admission to the Coronary Care Unit (CCU. As such, patients do not benefit as much from thrombolysis as they potentially could. Our aim was to identify the number of patients that may have benefited from a fast track approach in instituting thrombolytic therapy at the A&E Department. We studied the time factors contributing to delay in thrombolysis at all three levels at a 800 bedded acute teaching hospital serving a population of

2 12 Hong Kong j. emerg. med. n Vol. 7(1 n Jan ,000 in the Eastern sector of Singapore, over a three month period from December 1997 to March Methods A clinical quality improvement audit based on a prospective observational study was carried out for the period of December 1997 to March 1998, collecting information on patients that presented with obvious uncomplicated acute myocardial infarction as defined by a combination of the following: Typical chest pain lasting >20 minutes Onset of major symptoms within 12 hours Characteristic ECG changes showing ST segment elevation of more than 2 mm in two consecutive precordial leads (not V1, or more than 1 mm in two standard limb leads Inclusion criteria did not impose an age or gender limit. Exclusion criteria included those with: suspected aortic dissection active bleeding recent surgery or major trauma (less than two months recent head injury or CVA (even with complete recovery prolonged cardiopulmonary resuscitation (greater than 15 minutes systolic blood pressure of greater than 180 mmhg previous allergic reaction to thrombolytics use of anticoagulants or a known bleeding diathesis active peptic ulcer disease abdominal aneurysm possible pregnancy proliferative or haemorrhagic diabetic retinopathy cardiogenic shock uncertainty of diagnosis non-q AMI A standardised form was devised to collect the demographic details and the required data. The following times were tabulated. (A Prehospital duration (t 1 : Time from onset of severe chest pain to presentation at the A&E Department (B Time spent at the A&E Department (t 2 (C Time from leaving the A&E Department to the administration of intravenous thrombolysis (t 3 The details required in the forms were entered by both the emergency doctors/nurses as well as the intensive care nurses, documenting the time of admission to the A&E Department, the time of admission to the coronary care unit (CCU and the time of initiation of thrombolytics. The completed forms were returned to the A&E Department for entry and analysis. All cases that satisfied the inclusion criteria were analysed and those with any of the exclusion criteria were omitted. Results A total of 142 patients presented to the hospital with acute myocardial infarction, of which 104 satisfied the inclusion criteria. Ten patients died either at the A&E Department or in the CCU on admission, 12 were excluded because of non-q infarcts, 6 had uncontrolled blood pressure (as a result were administered thrombolytics late and another 10 patients were excluded because of delay in arriving at the diagnosis. The results were from data on the 104 patients who presented with acute myocardial infarction with inclusion criteria as defined above and were administered either intravenous streptokinase or recombinant tissue-type plasminogen activator in the CCU. The majority of patients were men (63.46%. The mean age of females was higher (70.13 ± SD8.73 than that of males (55.59 ± Fewer patients (both male and female arrived at the A& E Department using the ambulance service than by their own means. (Table 1 There were

3 Tiru et al./time delays in instituting thrombolysis in acute myocardial infarction 13 Table 1. Sex distribution of mode of transport used Mode of transport Ambulance Own Male 48.48% 51.52% Female 47.37% 52.63% 48.48% of males utilising the ambulance service as compared to 47.37% of females. Using z-test, there was no significant difference between the percentage of males and females that utilised the ambulance services or came on their own. The initial ECG done on arrival demonstrated acute characteristic ST elevation in all the patients as part of the inclusion criteria. Prehospital delays Males presented earlier with 46.97% within 1 hour of onset of severe chest pain, 21.21% between 1 and 2 hours, 21.21% between 2 and 6 hours, and 10.61% more than 6 hours later. Females presented later with 23.68% within 1 hour of onset of symptoms, 23.68% between 1 and 2 hours, 34.21% between 2 and 6 hours, and 18.42% more than 6 hours later. (Table 2 and Chart 1 However when comparing the means there was no statistical difference in prehospital delays between the two sexes (males ± SD14.06, females ± SD13.01, p=0.34. Hospital delays The time delay at the A&E Department was calculated from the time of admission to the time the patient left the department. As for the time spent at the A&E Department, the mean time for males was (SD ± minutes while that for females was (SD ± minutes (p=0.34. (Table 3 There is no statistical significance between the two. The time delay in initiating thrombolysis upon leaving the A&E Department was (SD ± minutes for males and (SD ± minutes for females. (Table 3 At the level of the A&E Department, the mean door to ECG time for cases conveyed by ambulance was 5.3 minutes and those that came using their own transport was 12.4 minutes. The mean time for the Table 2. Distribution of prehospital time between sexes Number Percentage males females %males %females t 1 <1hr % 23.68% 1hr. <t 1 <2hr % 23.68% 2hr. <t 1 <6hr % 34.21% t 1 >6hr % 18.42% % number of total male or female population 50% 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% T1 < 1hr. 1hr. < T1 < 2hr. 2hr. < T1 < 6hr. t1 > 6hr. males females Chart 1. Comparison of time of onset of chest pain and presentation to the A&E Dept distribution between males & females Table 3. Time distribution of time spent in A&E Dept (t 2 and delay in thrombolysis after leaving A&E Dept (t 3 Time (mins Mean t 2 (SD Mean t 3 (SD Male ( (29.84 Female ( (25.11 performance of a chest radiograph was 6.8 minutes. The mean time to contact the admitting cardiologist/medical team and arranging for a coronary care bed was 16.3 minutes (the longest being 89 minutes and the shortest being 5 minutes. Transporting the patient from the A&E Department to the Intensive Care Unit took an average of 7.2 minutes. (Table 5 There was overlap in the time spent in each of the procedure which explained the fact that the total time did not equate to the mean time spent. At the Medical Intensive Care Unit it took the medical registrar on call an average of 15.2 minutes (after normal office hours and the cardiologist 20.3 minutes (during office hours to review the case. (Table 6

4 14 Hong Kong j. emerg. med. n Vol. 7(1 n Jan 2000 Table 4. Mean total time elapsed from onset of symptoms to thrombolysis Sex Time (minutes Male Female Table 5. Mean time delays in A&E Department Time (minutes Door to ECG time (ambulance 5.3 Door to ECG time (own 12.4 CXR 6.8 Obtaining ICU bed 10.3 Transport of patient to MICU 7.2 Table 6. Time delays in the Medical Intensive Care Unit Time (minutes Review by Cardiologist (during 20.3 office hours Review by Medical Registrar on-call 15.2 (after office hours Time between ordering thrombolytics 8.3 and instituting it Total time from onset of severe typical chest pain to thrombolysis was minutes in males and minutes in females. (Table 4 Discussion In this study, a significant proportion of patients presented to hospital late, women presenting even later than men, as in some other studies The postulated reasons include atypical initial symptoms, patients living alone at the time of the event. We did not differentiate whether the prehospital delay was due to delay in calling for help (patient delay or delay in the delivery of ambulance. Delays at the prehospital level include lack of awareness of symptoms of unstable angina or acute myocardial infarction and therefore attributing their symptoms to other causes. This implies a possible lack of health education knowledge. Due to the high workload and slow moving traffic during peak hours, the time taken for the arrival of the ambulance service is another factor causing delay. Moreover, in Singapore intravenous thrombolysis is not initiated by the primary referring physician even when they diagnose an acute myocardial infarction. Time delays at the A&E Department included time taken to triage and obtaining the initial electrocardiogram as evidenced by a mean door to ECG time of 5.3 minutes in ambulance cases and 12.4 minutes for non-ambulance cases. Some reasons for these delays included time required for administrative matters (e.g. registration, selfreferrals and waiting to be triaged (this was especially so during busy periods. In this study only patients with clear acute ST elevations were audited, hence there was no delay in diagnosis as all electrocardiograms were reviewed immediately by a doctor. Other factors that contributed to time delay in the A&E Department included administration of other medications (such as aspirin, morphine, nitrates and oxygen, obtaining a chest radiograph before the initiation of thrombolysis as specified by the clinical pathway devised by the hospital, contacting the on duty medical/cardiology registrar and arranging for intensive care admission. Therefore there is much room for improvement in these aspects within the A&E Department. Thrombolytic therapy should be administered as first line therapy, once the relevant contraindications have been excluded. Cardiac consultation was a major cause for delay in our study. This is clinically indicated in patients suspected of having an unstable ischaemic syndrome but with unclear symptoms, questions relating to ECG findings, or possible contraindications. Consultation as a routine practice or part of a medical policy and not clinically indicated is not justified when it causes delay given the compelling time-dependant relationship between reperfusion and outcome in patients with AMI. Reduction in "decision to drug" time may be achieved by having the thrombolytic agent available in the emergency department as opposed to having to obtain the drug from the pharmacy, having relatives present during the clinical assessment and decision making process. In our setting, many patients consult their relatives before giving consent to thrombolytics.

5 Tiru et al./time delays in instituting thrombolysis in acute myocardial infarction 15 Upon leaving the A&E Department, time delays were encountered in transferring the patient to the intensive care unit, obtaining written consent, performing a repeat (pre-thrombolysis electrocardiogram and preparation of intravenous thrombolysis. Hence all uncomplicated patients who are haemodynamically stable should have thrombolytics administered within the confines of the A&E Department. Thrombolytics should only be withheld in A&E Department for patients who may have relative contraindications, questionable benefit versus risks or those requiring invasive procedures e.g. intra-aortic balloon pumping, central lines, transvenous pacing or urgent percutaneous angioplasty. Health education has not yet developed its full potential in educating the lay public. The public generally derived their medical knowledge from information gathered during consultation with their general practitioner, cardiologist or from television programs intended for entertainment but not for health education. Planned and evaluated public education about cardiac disease, its presenting symptoms and potential life-saving measures remain sporadic. As a society with rising affluence and aging population, the incidence of coronary artery disease will likely to rise and therefore community awareness through prevention, early identification and treatment should be instituted. As demonstrated in other major studies, 9 cardiac consultation is clinically indicated in patients suspected of having an unstable ischaemic syndrome who present with unclear symptoms, questions related to ECG findings, or possible contraindications. However haemodynamically stable patients with criteria that satisfies indications for initiation of thrombolytic therapy will derive greater benefit from the earlier administration of the thrombolytics in the A&E Department given the compelling time-dependant relationship between reperfusion and outcomes in patients with acute myocardial infarction. In light of evidence from this audit, the medical board of this hospital has recently approved the initiating of thrombolysis in a selected group of patients with acute myocardial infarction in the Accident and Emergency Department and this is a move that may encourage other A&E departments to follow. Acknowledgements Ashvin Thambyah, National University of Singapore, for his invaluable input in the statistical analysis of this data. References 1. Fibrinolytic Therapy Trialists' (FTT Collaborative Group. Indications for fibrinolytic therapy in suspected acute myocardial infarction: collaborative overview of early mortality and major morbidity results from all randomised trials of more than 1000 patients. Lancet 1994;343: Reimer KA, Lowe JE, Rasmussen MM, et al. The wavefront phenomenon of ischaemic cell death. 1. Myocardial infarct size vs duration of coronary occlusion in dogs. Circulation. 1977; 56: Bergmann SR, Lerch RA, Fox KAA, et al. Temporal dependence of beneficial effects of coronary thrombolysis characterised by positron tomography. Am J Med 1982;73: Gruppo Italiano per lo Styudio della Streptochinase nell'infarcto miocardio (GISSI. Effectiveness of intravenous thrombolytic treatment in acute myocardial infarction. Lancet 1986;1: ISIS-2 (Second International Study of Infarct Survival Collaborative Group. Randomised trial of intravenous streptokinase, oral aspirin, both or neither among 17,187 cases of suspected acute myocardial infarction: ISIS-2. Lancet 1988;2: Weaver WD, Cerqueira M, Hallstrom AP, et al, for the MITI Project Investigators. Prehospital-initiated vs hospital-initiated thrombolytic therapy. JAMA 1993;270: The GUSTO Investigators. An international randomised trial comparing four thrombolytic strategies for acute myocardial infarction. N Engl J Med 1993;329: National Heart Attack Alert Program Coordinating Committee. 60 Minutes to Treatment Working Group. Emergency department: rapid identification and treatment of patients with acute myocardial infarction. Ann Emerg Med 1994;23: Weaver WD, White HD, Wilcox RG, et al. Comparison of characteristics and outcomes among women and men with acute myocardial infarction treated with thrombolytic therapy. JAMA 1996;275: Lambrew CT, Bowlby LJ, Rogers WJ, et al. Factors Influencing the time to thrombolysis in acute myocardial infarction. Arch Intern Med 1997;157 (22: