The Hong Kong Heart Attack Survey

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					                                                                                                              The Hong Kong Heart Attack Survey: 411008

                 The Hong Kong Heart Attack Survey
Clinical Audit and Registry of Acute Myocardial Infarction in Hong Kong:
1995 – 1996

Woo KS, Hung YT, Wong SP, Chan WK, Li SK, Lau CP, Tse KF, Ko P
Hong Kong AMI Registry Task Force, Hong Kong College of Cardiology

INTRODUCTION                                                   RESULTS
Coronary artery disease, in particular acute myocardial        Demographic characteristics
infarction (heart attack, AMI), is a leading cause of death.   There were 3373 AMI patients registered in the period
AMI in Chinese is a serious condition, with higher             1995-96 (67.3% males; male:female ratio of 2.1:1). In
complication rates and mortality compared with western         1996, 1789 patients, were admitted. Their mean age
countries. To improve the care of AMI patients in              was 67.6±11.6 years and 45.2% of patients were >70
Hong Kong, the need for a well organised health care           years of age. AMI affected few (1.5%) subjects <40
plan with well defined priorities is obvious. In this          years of age (Fig.1). These age ranges were similar to
context, a territory-wide registry and audit of AMI will       those obtained from IPAS. The majority (96.5%) of
reliably assess the size of this problem and the actual        AMI patients in Hong Kong were admitted into the 18
demand for resources, and document the application and         public hospitals. Most patients (64.7%) arrived at the
outcome of these treatments.           We carried out a        A&E department of hospitals within 4 hours of onset,
prospective study, through the joint effort of all             and 81.0% arrived within 10 hours after onset of chest
cardiologists and physicians in both private and public        pain (Fig.2). Typical precordial pain was present as the
sectors, to monitor carefully all AMI patients admitted        diagnostic criterion in 84.7% of patients.
into hospitals, the treatments they received and their

SUBJECTS AND METHODS                                                                                    40
                                                                                % of Distribution

All patients with AMI admitted into coronary care units                                                 30
or general wards of all acute public or private hospitals                                               20

in Hong Kong from January 1995 to December 1996                                                         10
were studied. The patient data, hospital mortality and                                                  <40          4 0 -4 9          5 0 -5 9            6 0 -6 9         7 0 -7 9         >80
other outcome information were monitored and                                                                                              A g e in Y e a r s

registered in the data forms, using uniform registration
guidelines and predefined diagnostic criteria. The data                ig u re 1 – D i tr b u t o   of A ge n 3373
                                                                FigureF1. Distributionsof iAge iinn3373 AMI iPatients A M I                                                        P a t ie n ts

sheets were rescreened by a research nurse at the
coordination centre. The research nurse randomly
visited the collaborative centre and made random audits
of the reported information from patients’ case notes.
The audit and registry was centrally coordinated by the                                         60
                                                                % of Patients

AMI Task Force of the Hong Kong College of                                                      50

Cardiology. Quality control for coverage and validity                                           40

of the project were ascertained by counterchecking with                                         30

the Hospital Authority In-patient Access System (IPAS)                                          20

data on 2407 AMI admissions (ICD-9: 410.1) during the                                           10

period July 1996 to June 1997.                                                                      0
                                                                                                              1 -4              4 -6              6 -1 0              >10
                                                                                                                 T im e A f t e r P a in O n s e t ( H o u r s )

                                                                    F i u re 2      A r r v a l Pain A f t e
                                                                Figureg2. Arrival- Time iAfter T i m e Onset r                                              P a in O n s e t

                                                                                                              The Hong Kong Heart Attack Survey: 411008

Risk factors and presenting features in AMI                                                       35
                                                                                                           (p<0.001)                        (p<0.001)
Cigarette smoking, hypertension and diabetes mellitus
were the common atherosclerosis risk factors, and 11.8%                                           30

of patients had history of hypercholesterolaemia (Fig.3).                                                                                                     (p>0.05)

                                                                         Hospital Mortality (%)
Information on blood lipid profiles were available in 1967
patients (58.3%), of whom 44.7% had total cholesterol                                             20
>5.2mmol/L.          Mean      total    cholesterol    was
5.3±2.6mmol/L. Previous angina history was present in
only 32.3% of patients and old myocardial infarction in                                           10
13.0% of patients (n=3264). Q-wave infarcts were
observed in 67-69% of patients, whilst 32.1% had non-Q                                             5

wave infarcts.

                                                                                                        <70          >70              M          F      CCU        GW

                  Hypertension                                                                         [Age (yrs)]                   [Gender]           [W ards]
                                                                                                                               Patient Group

                                                                                                  Figure 4       -    Hospital Mortality in 3373 AMI Patients
                                                                       Figure 4. Hospital Mortality in 3373 AMI Patients

           IHD Family History

                                                                       Table 1. Clinical Complications in 2816 AMI Patients

                                                                                                                                                1995       1996          Overall
              Diabetes Mellitus
                                                                       Heart Failure                                                            35.4%     36.4%               35.9%

                                  0   10   20    30      40     50     Cardiogenic Shock                                                        13.4%     12.2%               12.8%

                                                                       Bundle Branch Block                                                      3.9%      5.0%                4.4%

Figure 3. Figure 3 - Atherosclerosis in 3290 AMIin 3290 AMI Patients
          Atherosclerosis Risk Factor Risk Factor Patients             High Grade A-V Block                                                     8.5%      6.7%                7.6%
           (According to History)
                             (According to History)
                                                                       Atrial Fibrillation / Flutter                                            8.9%      11.5%               10.1%

                                                                       VT                                                                       12.0%     14.5%               13.1%
Clinical complications
                                                                       VF                                                                       8.6%      9.9%                9.2%
The hospital course of patients was complicated by heart
failure (35.9%), cardiogenic shock (12.8%), bundle                     Stroke                                                                   0.7%      0.9%                0.8%
branch block (4.4%), high grade A-V block (7.6%), atrial
fibrillation or flutter (10.1%), ventricular tachycardia               VT / VF: Ventricular Tachycardia or Fibrillation
(13.1%) and ventricular fibrillation (9.2%), while stroke
was documented in 0.8% of patients (Table 1). During
hospitalisation, 22.9% died (14.0% in those <70 years and                                              P u m p F a i lu r e
                                                                                                           (3 7 .7 % )                                   N o n -C a rd ia c
33.8% in patients >70 years, mostly female) (Fig.4), due                                                                                                    (11 .8 % )

to pump failure in 37.7% and sudden death or documented
primary arrhythmias in 50.5% (Fig.5). Compared with
IPAS data, the case fatality in coronary care units (CCU)
was similar (21.7% vs. 21.5%) but the overall case fatality
was slightly lower (22.9% vs. 28.4%, p<0.05).

                                                                                                       P r im a r y A r r h y t h m i a s
                                                                                                                 (11 .9 % )                                S u d d e n D e a th
                                                                                                                                                                (3 8 .6 % )

                                                                                                   F i g u r e 5 - C a u s e s o f D e a t h i n 7 2 1 A M I P a t ie n t s
                                                                       Figure 5. Causes of Death in 721 AMI Patients

                                                                                          The Hong Kong Heart Attack Survey: 411008

Hospital treatment                                                          female proportion (i.e. weaker male dominance) in Hong
Of 2821 patients studied, 64.4% were admitted into CCU                      Kong AMI, compared with many western reports3,4.
while 35.6% were admitted to general wards (61.4% into                      However, ascertainment bias of potential confounding
CCU and 38.6% in general wards in IPAS data).                               factors, such as differences in age, gender and case-mix
Thrombolytic therapies were administered in 48.9% (in                       may be present. AMI was the first clinical manifestation
60.4% of patients admitted within 10 hours after pain                       of coronary artery disease in 54.7% of patients. Subjects
onset), aspirin in 85.2%, heparin in 21.9% and                              with higher risk for developing AMI should be more alert
ACE-inhibitors in 66.2%, but only 46.1% of patients                         to the emergence of AMI symptoms and seek medical care
received β-blockers in hospitals. Lipid-lowering agents                     at once. Only two-thirds of AMI patients were managed
were started or continued in 13.2% of patients in hospitals                 in intensive CCU and one-third in general wards during
(Fig.6).    Investigations for risk stratification were                     the acute stage, an observation highlighting an inadequacy
performed or booked on discharge, including                                 of CCU beds in many public hospitals in Hong Kong.
echocardiography (53.9%), ambulatory ECG (14.0%),                           More resources should be allocated to public hospitals,
treadmill exercise test (33.1%), exercise radionuclide                      and measures for faster turn-over and more cost-effective
cardiac imaging (11.3%) and coronary angiography                            utilisation of existing CCU beds should be implemented.
(23.7%) (n=2816).
                                                                            Cigarette smoking was the dominant risk factor and
                                                                            history of hypertension, diabetes mellitus and
       PTCA                                                                 hyperlipidaemia, were present in one-third, one-fifth and
                                                                            one-tenth of AMI patients, respectively. The present
            Lipid-Lowering Agents
                                                                            registry was not designed to specifically study the risk
                                                 ACE-Inhibitors             factors of AMI in Hong Kong, for which a properly
                                                                            conducted case-control study is reqired. The mean
                   Heparin (Intravenous)
                                                                            cholesterol (5.3±2.6mmol/L), however, was not
                             Beta-blockers                                  significantly different from that of normal control subjects
                                                                            in Hong Kong or southern China5. Therefore, there is a
                                                                            need to identify other emerging novel risk factors. The
                                      Thrombolytics                         hospital and 30-day mortality of AMI patients
                                                                            (22.6-22.9%) was higher than many western reports, but
   0   10     20    30     40    50        60   70    80   90               showed a slight improvement compared with those in
                      Percentage of Patients                                1970s (24-26%)2-4. The relatively higher AMI in Hong
                                                                            Kong is attributable to the older ages of patients, relatively
                                                                            high numbers of females, densely populated community
   Figure 6 - Treatment for 2821 for Patients
Figure 6. MedicalMedical Treatment AMI2821 AMI Patients
                                                                            with easy access to hospitals, and prevalence of
                                                                            undiagnosed diabetes mellitus among the community.
                                                                            Mortality has improved significantly in the past two
DISCUSSION                                                                  decades in both young (≤59 years) and older ages (>70
The present AMI registry is the first in Hong Kong. The
similar demographic profiles and case fatality (in CCU at
least) in the two AMI databases indicate the good
                                                                            In auditing the utilisation of key treatments proven to be
coverage of this registry. Based on a registry of 3373
                                                                            useful (i.e.     evidence-based), intravenous heparin,
AMI over 2 years, the AMI admission incidence was at
                                                                            thrombolytics, β-blockers, lipid-lowering agents and
least 26 per 100,000 population per year in Hong Kong.
                                                                            angioplasty have been under-utilised in management of
This is slightly higher than the incidence reported in the
                                                                            AMI in Hong Kong.              Thrombolytic therapy has
1970s and 1980s (14-22 per 100,000 population), and is
                                                                            revolutionised AMI treatment. In the present registry,
only one-tenth to one-fourth of those in western developed
                                                                            patients were admitted at a median delay of 2.6 hours after
countries, but similar to those in Japan and many cities in
                                                                            pain onset, and over 60% of patients were within the
northern mainland China1.
                                                                            12-hour therapeutic window of thrombolytic treatment,
                                                                            but their thrombolytic eligibility has not been studied.
The demographic and clinical features of AMI conform to
                                                                            Early reperfusion with thrombolytics or coronary
the classical pattern of AMI reported in the 1970s and
                                                                            angioplasty, nevertheless, is important to achieve a better
1980s, in respect of sex and age distribution, clinical
                                                                            therapeutic result. Better public education and patient
presentation, characters of infarcts and prevalence of
                                                                            counselling for early recognition of onset of AMI
complications2. AMI still predominantly affects people
                                                                            symptoms, and hence early hospital admission, is needed.
>60 years, with the mean age of AMI patients in Hong
Kong 10 years older than those in western literature.
                                                                            No comparison between individual collaborating hospitals
This aging factor would also explain the relatively higher
                                                                            has been performed, and data must be interpreted with

                                                                                          The Hong Kong Heart Attack Survey: 411008

care, due to confounding factors related to differences in                REFERENCES
age, gender and case-mix, which could not be ascertained                  1. Woo KS & Donnan SPB.               Epidemiology of
with our simple project design.                                              coronary arterial disease in the Chinese. Intern J
                                                                             Cardiol 1989;24:83-93.
SUMMARY                                                                   2. Woo KS, Pun CO, Wang RYC, Ma H, Huang ZZ,
The present registry matches fairly well the basic                           Dai RH, Huang DJ, Vallance-Owen J. Validation
demographic and case-fatality features of the IPAS                           of a coronary prognostic index for the Chinese: A
data. The incidence of AMI admissions in Hong                                tale of three cities.           Intern J Cardiol
Kong is increasing, with 96.7% of patients treated in                        1989;23:173-178.
public hospitals. AMI in Hong Kong follows classical                      3. Goldberg RJ, Yarzebski J, Lessard D, Gore JM. A
                                                                             two-decades (1975-1995) long experience in the
patterns. It affects relatively older patients and more
                                                                             incidence, in-hospital and long-term case-fatality
females than males. Cigarette smoking is the dominant
                                                                             rates of acute myocardial infarction:            A
risk factor. There is a high prevalence of Q-wave infarct,
                                                                             community-wide perspective. J Am Coll Cardiol
heart failure, cardiogenic shock complications, and a high
case-fatality rate (22.9%). Over 81% of patients arrived
                                                                          4. Barron HV, Michaels AD, Maynard C, Every NR.
at hospitals within the therapeutic time-window (<12
                                                                             For The National Registry of Myocardium. Use of
hours after onset) for thrombolytic therapies. Certain
                                                                             angiotensin-converting enzyme inhibitors at
acute AMI treatments currently proven to be useful were
                                                                             discharge in patients with acute myocardial
under-utilised, including thrombolytic therapies in some
                                                                             infarction in the United States: Data from the
hospitals (<40%), β-blockers (46.1%), intravenous
                                                                             National Registry of Myocardial Infarction 2. J Am
heparin (21.9%) and lipid-lowering drugs (13.2%).
                                                                             Coll Cardiol 1998;32:360-7.
                                                                          5. Woo KS, lMcCrohon JA, Chook P, Adams MR,
                                                                             Robinson JTC, McCredie RJ, Lam CWK, Feng JZ,
                                                                             Celermajer DS. Chinese adults are less susceptible
                                                                             than whites to age-related endothelial dysfunction.
                                                                             J Am Coll Cardiol 1997;30:113-118.

                                                           Key Messages
  1.     More health education, counselling and mass campaigns for patients and public to recognise the early
         symptoms of AMI and seek earlier hospital admission and medical treatments are required.
  2.     More efficient triage for suspected acute coronary syndrome, more funding to CCU establishment, and more
         in-service training of nurses and medical staff in emergency department and CCU of hospitals is needed.
  3.     Thrombolytic therapies, β-blockers, intravenous heparin (or other specific anti-thrombin), ACE-inhibitors and
         primary coronary angioplasty should be used more widely.
  4.     Better promotion of cardiac rehabilitation programmes, including screening for lipid profile and starting
         lipid-lowering regimens before discharge is recommended.
  5.     Health providers should further audit the quality of coronary service in Hong Kong.
  6.     Individual hospitals should perform further audits, to compare the outcome of AMI patients with overall
         benchmarks, and correlate with treatment utilised and index of clinical severity, for improved quality

 Research funded by the HSRC may be published and disseminated as an HSRC Report. The aim of these reports is to increase the availability and
 awareness of research outcomes to healthcare practitioners.
 Research Fund Secretariat, Health, Welfare and Food Bureau, 18/F, Murray Building, Garden Road, Central, Hong Kong
 Tel: 3150 8986; Fax: 3150 8993; E-mail:
 Editors: Dr Janice Johnston, Dr Richard A. Collins

 HSRC project number: 411008                  HRSC funding approved: 25 July 1994                      Final report accepted: 28 October 2003


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