590
Journal of the Royal Society of Medicine Volume 84 October 1991
Open
exercise electrocardiography: a service to improve management of ischaemic heart disease by general practitioners access
A N Sulke DM MnRCP' A D C Norris FRCP3
V E Paul MB MRcP2 C J Taylor BSc3 R H Roberts MB BS MRCP3 'Guy's Hospital, St Thomas' Street, London SEl 9RT; 2St George's Hospital, Blackshaw Road, London SW17 OQT; and 3William Harvey Hospital, Ashford, Kent Keywords: exercise tests; open access; general practice
Summary An initial study of the use of open access exercise electrocardiography by general practitioners (GPs) in South East Kent showed that patient selection and interpretation of test results was frequently incorrect. After issuing guidelines, modifying the request form and instituting registrar review of all requests, significant improvements in both referral pattern, result interpretation and patient management have resulted. Forty-nine GPs requested 110 exercise tests during 1988/89. Twelve per cent were not undertaken after discussion with the referring practitioner. Eighty-four per cent of those tested would have been referred to the district general hospital cardiology outpatient department in the absence of open access exercise electrocardiography service. Six per cent of patients were referred directly for invasive investigation. Thirty-five per cent were referred to the district general hospital cardiology outpatient department, whilst 42% were spared hospital referral based on the result of the investigation. Better use of the modified service was suggested by: referral of fewer patients with non-cardiac chest pains (P=0.002); more patients with a moderate pre-test probability of ischaemic heart disease (P< 0.05); fewer inappropriate requests (P< 0.01); and fewer inappropriately undertaken tests (P< 0.001) than in the previous study. All patients with strongly positive test results were appropriately managed. Open access exercise electrocardiography in the format investigated is potentially a cost-effective and useful tool to improve diagnosis and management of heart disease by GPs. Introduction Exercise electrocardiography is widely used in the diagnosis and management of ischaemic heart disease and exercise-related arrhythmias. Following extensive comparison with the accepted 'gold standard' of coronary angiographyl2, the sensitivity and specificity of the test is well defined. Most cardiologists agree that the use of exercise electrocardiography in diagnosis of ischaemic heart disease is best in patients with a moderate probability of the disease3. The test is also of prognostic value in the assessment of patients with known ischaemic heart disease46. It is, however, of little use in the screening of asymptomatic patients for suspected ischaemic heart disease7. By allowing general practitioners (GPs) open access to this investigation it was hoped that fewer inappropriate referrals to the district general hospital cardiology outpatient department would
result and that patients with severe ischaemic heart disease would be directly referred to tertiary cardiac centres expediting their invasive investigation and management. Following a previous study of the use of open access exercise electrocardiography in South East Kent8 we have modified the service. In the present study we have investigated the effects of these modifications on the use and interpretation of exercise electrocardiography as well as its influence on management of ischaemic heart disease by GPs in the South East Kent health district. Methods All South East Kent GPs were circulated with the results and conclusions of the initial study of the use of open access exercise electrocardiography8 as well as a 1000 word review of guidelines for use of exercise electrocardiography and its place in conventional management of ischaemic heart disease. A resting 12-lead electrocardiograph was performed in all patients accepted for exercise electrocardiography. Open access exercise electrocardiograph request forms required information on each patient's cardiovascular status, including signs and symptoms, family history, smoking history, drugs prescribed, and the reason(s) for the request which consisted of five options. These were: (1) Screening for ischaemic heart disease, (2) diagnosis of ischaemic heart disease, (3) prognosis of known ischaemic heart disease, (4) arrhythmia assessment, and (5) reassurance. The study questionnaire then assessed the GPs estimation of risk of ischaemic heart disease in the patient (mild, moderate, or severe) and whether the patient would have been referred to the district general hospital cardiology service, to a tertiary cardiac centre, or managed without further referral in the absence of the open access service. The electrocardiograph and request form were reviewed by the cardiology registrar (RHR). In the absence of contraindications and if requests conformed to the accepted guidelines for use of exercise electrocardiography9"10, it was undertaken as soon as possible. If inappropriate, the request was further discussed with the referring GP. No patient was refused the test (unless contraindicated) ifthe GP still felt that it was necessary. All patients were classified, after clinical assessment by the supervising clinician, into CASS symptom categories (typical angina, atypical angina, noncardiac chest pain, asymptomatic)l". All patients undertook a symptom-limited graded exercise treadmill test using the Bruce Protocol'2. The 12-lead
0141-0768/91/
100590-05/$02.00/0 © 1991
The Royal Society of Medicine
Journal of the Royal Society of Medicine Volume 84 October 1991
electrocardiograph was presented using the Marquette Case 2 System. Blood pressure was measured at rest, 2 min into each stage, and at one minute intervals during the recovery phase. The test was terminated prematurely if there were adverse electrocardiograph changes (ST depression of >3 mm, ST elevation of > 0.1 mV or arrhythmias), or an atypical pressor response (falling or static blood pressure despite increasing work load after the initial adjustment period, or excessive blood pressure rise to >250 systolic, or > 130 diastolic). The exercise test was then reported on independently by three cardiology registrars (ANS, VEP, RHR) and by a consultant cardiologist (ADN) if disagreement arose. The report described the resting 12-lead electrocardiograph, exercise duration, signs and symptoms during the test, the reason for termination of the test, maximum heart rate achieved (as a percentage of the target heart rate, taken as 220 minus the patient's age), pulse and pressor response during exercise and recovery phases, as well as electrocardiograph morphology and rhythm changes. The result was classified into one of six categories. (1) Mildly positive, if ST segment depression occurred at greater than 90% of target heart rate, was between 1 mm and 2 mm and resolved within 2 min of the recovery period. (2) Moderately positive, if ST depression occurred at less than 90% of the target heart rate, was between 2 mm and 3 mm, or persisted longer than 2 mm into the recovery period. (3) Strongly positive, if ST segment depression or elevation occurred during the first two stages of the test protocol, at heart rates less than 80o of the target value or if greater than 3 mm planar ST depression at any heart rate. (4) Negative, if the test showed normal pulse and pressor response and no electrocardiographic morphology or rhythm changes despite attaining at least 80% of the target heart rate. (5) Equivocal, if a test showed any changes not fitting any of the above criteria. (6) Inadequate or nondiagnostic, if the patient failed to achieve 80% of the target heart rate with no abnormal electrocardiograph, pulse or pressor changes. On receipt of the test results the GPs were again asked to categorize their patient's risk of ischaemic heart disease as mild, moderate, or severe, and to outline their proposed further management. All patients were ascribed a pre-test probability of risk of ischaemic heart disease on the basis of their age and sex and character of their chest pain.
% OF TOTAL POPULATION REFERRED C9
40
o30
20 10
0
ATYPICAL ."" NON-COARAC ASN YMPTOMATIC
TYPICAkL
CLASSIFIqATION OF SYMPTOMS _ FIRST STUDY
_ SECOND STUDY
Figure 1. Hospital classification of symptoms according to the CASS criteria
This probability was derived from the tables constructed by Diamond and Forrester from CASS registry data'3. The post-test probability of ischaemic heart disease was also calculated from these tables. Statistical analysis Comparisons between the two studies were made using unpaired Student's t-tests for continuous variables and chi-squared tests for discontinuous variables. A value of P
Journal of the Royal Society of Medicine Volume 84 October 1991
Open
exercise electrocardiography: a service to improve management of ischaemic heart disease by general practitioners access
A N Sulke DM MnRCP' A D C Norris FRCP3
V E Paul MB MRcP2 C J Taylor BSc3 R H Roberts MB BS MRCP3 'Guy's Hospital, St Thomas' Street, London SEl 9RT; 2St George's Hospital, Blackshaw Road, London SW17 OQT; and 3William Harvey Hospital, Ashford, Kent Keywords: exercise tests; open access; general practice
Summary An initial study of the use of open access exercise electrocardiography by general practitioners (GPs) in South East Kent showed that patient selection and interpretation of test results was frequently incorrect. After issuing guidelines, modifying the request form and instituting registrar review of all requests, significant improvements in both referral pattern, result interpretation and patient management have resulted. Forty-nine GPs requested 110 exercise tests during 1988/89. Twelve per cent were not undertaken after discussion with the referring practitioner. Eighty-four per cent of those tested would have been referred to the district general hospital cardiology outpatient department in the absence of open access exercise electrocardiography service. Six per cent of patients were referred directly for invasive investigation. Thirty-five per cent were referred to the district general hospital cardiology outpatient department, whilst 42% were spared hospital referral based on the result of the investigation. Better use of the modified service was suggested by: referral of fewer patients with non-cardiac chest pains (P=0.002); more patients with a moderate pre-test probability of ischaemic heart disease (P< 0.05); fewer inappropriate requests (P< 0.01); and fewer inappropriately undertaken tests (P< 0.001) than in the previous study. All patients with strongly positive test results were appropriately managed. Open access exercise electrocardiography in the format investigated is potentially a cost-effective and useful tool to improve diagnosis and management of heart disease by GPs. Introduction Exercise electrocardiography is widely used in the diagnosis and management of ischaemic heart disease and exercise-related arrhythmias. Following extensive comparison with the accepted 'gold standard' of coronary angiographyl2, the sensitivity and specificity of the test is well defined. Most cardiologists agree that the use of exercise electrocardiography in diagnosis of ischaemic heart disease is best in patients with a moderate probability of the disease3. The test is also of prognostic value in the assessment of patients with known ischaemic heart disease46. It is, however, of little use in the screening of asymptomatic patients for suspected ischaemic heart disease7. By allowing general practitioners (GPs) open access to this investigation it was hoped that fewer inappropriate referrals to the district general hospital cardiology outpatient department would
result and that patients with severe ischaemic heart disease would be directly referred to tertiary cardiac centres expediting their invasive investigation and management. Following a previous study of the use of open access exercise electrocardiography in South East Kent8 we have modified the service. In the present study we have investigated the effects of these modifications on the use and interpretation of exercise electrocardiography as well as its influence on management of ischaemic heart disease by GPs in the South East Kent health district. Methods All South East Kent GPs were circulated with the results and conclusions of the initial study of the use of open access exercise electrocardiography8 as well as a 1000 word review of guidelines for use of exercise electrocardiography and its place in conventional management of ischaemic heart disease. A resting 12-lead electrocardiograph was performed in all patients accepted for exercise electrocardiography. Open access exercise electrocardiograph request forms required information on each patient's cardiovascular status, including signs and symptoms, family history, smoking history, drugs prescribed, and the reason(s) for the request which consisted of five options. These were: (1) Screening for ischaemic heart disease, (2) diagnosis of ischaemic heart disease, (3) prognosis of known ischaemic heart disease, (4) arrhythmia assessment, and (5) reassurance. The study questionnaire then assessed the GPs estimation of risk of ischaemic heart disease in the patient (mild, moderate, or severe) and whether the patient would have been referred to the district general hospital cardiology service, to a tertiary cardiac centre, or managed without further referral in the absence of the open access service. The electrocardiograph and request form were reviewed by the cardiology registrar (RHR). In the absence of contraindications and if requests conformed to the accepted guidelines for use of exercise electrocardiography9"10, it was undertaken as soon as possible. If inappropriate, the request was further discussed with the referring GP. No patient was refused the test (unless contraindicated) ifthe GP still felt that it was necessary. All patients were classified, after clinical assessment by the supervising clinician, into CASS symptom categories (typical angina, atypical angina, noncardiac chest pain, asymptomatic)l". All patients undertook a symptom-limited graded exercise treadmill test using the Bruce Protocol'2. The 12-lead
0141-0768/91/
100590-05/$02.00/0 © 1991
The Royal Society of Medicine
Journal of the Royal Society of Medicine Volume 84 October 1991
electrocardiograph was presented using the Marquette Case 2 System. Blood pressure was measured at rest, 2 min into each stage, and at one minute intervals during the recovery phase. The test was terminated prematurely if there were adverse electrocardiograph changes (ST depression of >3 mm, ST elevation of > 0.1 mV or arrhythmias), or an atypical pressor response (falling or static blood pressure despite increasing work load after the initial adjustment period, or excessive blood pressure rise to >250 systolic, or > 130 diastolic). The exercise test was then reported on independently by three cardiology registrars (ANS, VEP, RHR) and by a consultant cardiologist (ADN) if disagreement arose. The report described the resting 12-lead electrocardiograph, exercise duration, signs and symptoms during the test, the reason for termination of the test, maximum heart rate achieved (as a percentage of the target heart rate, taken as 220 minus the patient's age), pulse and pressor response during exercise and recovery phases, as well as electrocardiograph morphology and rhythm changes. The result was classified into one of six categories. (1) Mildly positive, if ST segment depression occurred at greater than 90% of target heart rate, was between 1 mm and 2 mm and resolved within 2 min of the recovery period. (2) Moderately positive, if ST depression occurred at less than 90% of the target heart rate, was between 2 mm and 3 mm, or persisted longer than 2 mm into the recovery period. (3) Strongly positive, if ST segment depression or elevation occurred during the first two stages of the test protocol, at heart rates less than 80o of the target value or if greater than 3 mm planar ST depression at any heart rate. (4) Negative, if the test showed normal pulse and pressor response and no electrocardiographic morphology or rhythm changes despite attaining at least 80% of the target heart rate. (5) Equivocal, if a test showed any changes not fitting any of the above criteria. (6) Inadequate or nondiagnostic, if the patient failed to achieve 80% of the target heart rate with no abnormal electrocardiograph, pulse or pressor changes. On receipt of the test results the GPs were again asked to categorize their patient's risk of ischaemic heart disease as mild, moderate, or severe, and to outline their proposed further management. All patients were ascribed a pre-test probability of risk of ischaemic heart disease on the basis of their age and sex and character of their chest pain.
% OF TOTAL POPULATION REFERRED C9
40
o30
20 10
0
ATYPICAL ."" NON-COARAC ASN YMPTOMATIC
TYPICAkL
CLASSIFIqATION OF SYMPTOMS _ FIRST STUDY
_ SECOND STUDY
Figure 1. Hospital classification of symptoms according to the CASS criteria
This probability was derived from the tables constructed by Diamond and Forrester from CASS registry data'3. The post-test probability of ischaemic heart disease was also calculated from these tables. Statistical analysis Comparisons between the two studies were made using unpaired Student's t-tests for continuous variables and chi-squared tests for discontinuous variables. A value of P
