Integrated Medical-Surgical Care in Acute Coronary Artery Disease Adv. Cardiol., vol. 15, pp. 48-58 (Karger, Basel 1975)
Indications for Surgery in the Patient with 'Impending Myocardial Infarction' (Unstable Angina Pectoris/ JOHN S. SCHROEDER, THEODORE B. BERNDT and DONALD C. HARRISON Cardiology Division, Stanford University School of Medicine, Stanford, Calif.
Introduction
Renewed interest in defining patients with 'impending myocardial infarction', or unstable angina pectoris, and the pathophysiology associated with it has become apparent for 3 reasons: (1) the current success of coronary bypass surgery, with a low mortality, in alleviating disability resulting from stable angina pectoris; (2) recent emphasis on reports suggesting prehospital mortality of 40-50 % and in-hospital mortality of 10-200/0 after a myocardial infarction occurs, and (3) the belief that application of coronary bypass surgery preinfarction could prevent this morbidity and mortality, with a similarly low operative risk to the patient. In this report, we outline our current impressions of the clinical syndrome of 'impending myocardial infarction', or unstable angina pectoris, including its definition, diagnosis, initial treatment, indications and complications of coronary arteriography, indications and complications of coronary bypass surgery and follow-up of patients undergoing these procedures.
Background
1 This work was supported in part by NIH Grant No. HL-5866 and Program Project Grant No. NIH I-POI-HL-lS833-01.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
In the 1950s there was a surge of interest in the syndrome of 'preinfarction angina' when it was thought that anticoagulation might avert the actual infarction. Uncontrolled studies reported myocardial infarction
SCHROEDER/BERNDT/HARRISON
49
rates as high as 40 Ofo within 3 months after onset of the 'preinfarction' syndrome. Interest then waned when it became apparent that anticoagulation would not have a major impact on altering the natural history of a patient with unstable angina. Over the last 5 years, as it became apparent that aorto-coronary bypass surgery could be performed with a surgical mortality of less than 5 Ofo, with over 75 Ofo of patients achieving good or complete relief of their angina pectoris, and in uncomplicated cases with a mortality of 10f0 (and 85 Ofo relief of angina), attention has again turned to the 'preinfarction angina' patient. Several papers in medical literature demonstrate that patients can come to surgery on an urgent or emergency basis for their 'impending myocardial infarctions' [3,5]. Morbidity and mortality figures vary greatly, as do the indications for surgery and treatment. The experience at Stanford University Hospital over the past 3 years with the syndrome, its course, and immediate and long-term results of the surgery in 81 patients form the basis for this report.
Although the terms 'impending myocardial infarction', and 'preinfarction angina' are generally used, this diagnosis must obviously be made retrospectively, since all patients do not progress to infarction. Other terms such as 'coronary insufficiency', 'intermediate syndrome' and 'rest angina' have been variously applied. We have chosen the term 'unstable angina pectoris' to reflect the unpredictable and highly variable, yet potentially serious outcome of this state. This term has also been accepted by the Cooperative Study Group sponsored by the National Heart and Lung Institute to investigate medical and surgical therapies for the syndrome. The patient with unstable angina pectoris seems to be precariously balanced, with episodes of ischemic pain during minimal provocation. These clinical data suggest that viable myocardium is on the edge of not receiving adequate coronary circulation and oxygen delivery and could advance to infarction with minimal further change. It is this physiologic concept on which the coronary bypass surgery and its concomitant delivery of blood past occluded areas is based. Our current definition of 'preinfarction angina' includes the following. 1. Onset of new angina in a previously asymptomatic patient, particularly if of crescendo nature.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Definition and Classification
SCHROEDER/BERNDT/HARRISON
50
2. Recent change (less than 4 weeks) in the character of the angina, with increasing severity and frequency and decreasing responsiveness to vasodilators. 3. Onset of one or more episodes of prolonged chest pain (greater than 15 min) requiring hospitalization, but not progressing to frank infarction on the basis of serial electrocardiogram and enzymes. 4. Those patients with continuing rest pain after the first 24 h of hospitalization. In our opinion, these patients have a more severe and life-threatening form of the unstable angina state.
Clinical Profile
The profile of the first 81 patients studied and operated on for unstable angina pectoris is outlined in table I. Approximately 50 Ofo had had previously documented myocardial infarction and the majority had one or more coronary artery disease risk factors. The duration of stable angina varied from 2 weeks to 13 years, with a mean of 34 months. Physical examination was not helpful in establishing the diagnosis and was usually normal in regard to the cardiovascular system.
The most common abnormalities are ST segment changes, primarily ST depression which is transitory. Rarely, a patient will show ST elevation consistent with Prinzmetal's variant angina. Residual abnormalities include flat or inverted T waves during and after pain episodes, which may resolve over several pain-free days. Normal electrocardiograms are not uncommon; however, lack of ST-T wave changes during the actual pain episode would suggest an etiology other than myocardial ischemia for the chest pain. The appearance of new Q waves indicates a transmural infarction, even without serial enzyme changes. Figure 1 demonstrates serial electrocardiographic changes in a 48-yearold woman who appeared at the emergency room several times over a period of 10 days with severe chest pain, each time refusing hospital admission. She was finally admitted with an acute anterior myocardial infarction and died in cardiogenic shock 2 days later.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Electrocardiographic Findings
Impending Myocardial Infarction
51
Table I. Clinical profile Number Total patients (men/women) Mean age, years (range) Coronary artery disease risk factors 1 (average per patient) Duration of stable angina pectoris, mean, months (range) Previous myocardial infarction
81 (66/15) 53 (36-71) 2.1 34 (0.5-16.0) 42
1 Hypertension, cigarette-smoking, abnormal lipids, family history of premature coronary artery disease.
Table II. Associated hemodynamic abnormalities in unstable angina pectoris Triple product changes
Group I Group II
pain-free
during spontaneous pain
during pacinginduced angina
normal normal
increased no change
increased slight increase only
We have performed chronic hemodynamic monitoring with pulmonary and arterial catheters for 24-72 h in 60 patients with unstable angina. Resting pain-free hemodynamics are consistently normal. At the onset of angina, there are several hemodynamic groups. One group has preceding rises in systolic blood pressure and heart rate, finally culminating in angina, secondary to increased left ventricular work. Another group has no demonstrable alterations in left ventricular work, as measured by systolic blood pressure, heart rate, and ejection times (table II). Changes in coronary circulation may be responsible for the rest angina in this patient group. Studies of pacing-induced angina episodes in our laboratory have also demonstrated wide variations in triple product from rest angina episodes, again indicating that the unstable anginal state may reflect an unstable coronary circulation in some patients.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Hemodynamic Abnormalities
52
SCHROEDER/BERNDT/HARRISON
~ II
~ III
~
~ AVL
~
AVF
~
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V
~
ttftt+~ a
~
~
"'
~
~ .
V2
friftvt
~
~
~
~ Vs
~ ~
~
Fig.I. Serial electrocardiograms showing ST depression V2 - 4 on 26.1.1973 (a); symmetrically inverted T waves V2 - 4 on 29. 1. 1973 (b); partial resolution of T wave abnormalities by 3. 2.1974 (c); frank anteroseptal infarction on 6. 2.1973 (d).
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
b
Impending Myocardial Infarction
53
I
~ II
~
AVR
~ AVL ---J
,I
-l
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~
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c
I
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~ AVL " ~ ~ III
AVF
~ ~
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d
~ V5
~
~ Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
~ ~
V4
SCHROEDER/BERNDT/HAluusON
54
Medical Treatment
In our experience, approximately 75 Ofo of patients admitted to a coronary care unit with unstable angina will 'cool down', or stabilize, within 24-48 h. On admission, particular attention should be given to factors which might have precipitated the unstable state: (1) emotional tension; (2) anxiety; (3) hypertension; (4) congestive heart failure; (5) occult aortic stenosis, and (6) anemia. These associated factors should be treated intensively, if present, and their resolution may return the patient to a stable course. In general, treatment consists of the same care as for a patient with an acute myocardial infarction: rest, quiet, sedation and pain relief with vasodilators with and without narcotics (table III). After initial hospitalization, evaluation and stabilization, a decision can be made concerning coronary arteriography and coronary bypass surgery. In the patients who continue to have rest angina in the coronary care unit, consideration should be given to treatment with propranolol (40-240 mg/day), particularly if they continue to have resting hypertension or tachycardia. In view of their serious prognosis, this group should also be considered for urgent coronary arteriography and early bypass surgery.
Although initial reports have suggested that as many as 20 Ofo of unstable angina patients might have normal coronary arteries at the time of study, typical ischemic chest pain, particularly if associated with transient ST-T wave changes, makes this finding unlikely. It is our impression that there is no increased risk to arteriography if the patient has been pain-free for at least 24 h prior to study. In the small patient group with continuing pain, there is probably a slightly increased risk of infarction or death from the study. Table IV indicates the findings on coronary arteriography and left ventricular angiography in our patients. The majority of patients had 2- or 3-vessel disease, and most of these patients had associated abnormalities of contraction on angiography. We have been unable to demonstrate a difference between the anatomy of these patients and those with stable angina pectoris.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Coronary Arteriography
Impending Myocardial Infarction
55
Table III. Initial medical treatment of unstable angina General treatment 1. Rest 2. Sedation 3. Pain relief (a) Nitroglycerin (b) Narcotics 4. Oxygen 5. Anticoagulation optional 6. p-blockade optional Specific treatment 1. Hypertension 2. Heart failure 3. Anemia 5. Arrhythmias, particularly atrial fibrillation or atrial flutter 6. Evaluation for associated valvular disease
Table IVa. Coronary arteriographic anatomy of unstable angina pectoris (total patients, 81) Vessels with> 70 Ofo occlusion
Number of patients
1
2
3
12
48
21
Table IVb. Coronary arteriographic anatomy of unstable angina pectoris (total patients, 81)
Number of patients
normal
hypokinesia akinesia
dyskinesia
25
12
14
26
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Left ventricular angiogram
SCHROEDER/BERNDT/HARRISON
56
Table V. Factors increasing operative risk in unstable angina pectoris
Continuing pain Congestive heart failure Ejection fraction < 50 % Hypotension Pump time Female sex Number of atherosclerotic risk factors
Immediate or emergency coronary bypass surgery is being practiced or advocated by many institutions at the present time. Mortality figures are undoubtedly higher in the unstable angina patient, generally reported as 5-10 Ofo. Recently it has been our experience that mortality can approach that of stable angina in the patients who cool down and are pain-free at the time of study and surgery. In the last 35 patients with unstable angina pectoris operated on at Stanford University Hospital there have been no deaths. Despite this, it is the smaller patient group with progressive and recurrent pain who are probably at highest risk of progressing to a myocardial infarction or death, and in whom bypass surgery may have a true prophylactic effect on survival. Data are not available at present, however, to prove this point. Our current indications for surgery include: (1) severe 2- or 3-vessel occlusive disease; (2) continuing rest angina with 1-, 2- or 3-vessel disease; (3) main left occlusive disease of > 50 Ofo; (4) proximal left anterior descending lesion of > 70 Ofo; (5) occlusive disease of the right coronary artery alone is optional and indications relate primarily to relief of angina rather than prophylaxis, and (6) continuing disability from stable angina after resolution of the unstable state. Table V outlines proven or suspected factors in increasing the risk of surgery in stable angina patients. Most of these factors also apply to the unstable angina patient. The incidence of perioperative myocardial infarction was 16 Ofo in the first 81 patients operated upon. Criteria for intraoperative infarction included appearance of new Q waves and serum glutamic oxalo-acetic transaminase (SGOT) rises over 100 U. This infarction rate is similar to other reports in the medical literature.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Indications for Surgery
Impending Myocardial Infarction
57
Two cooperative studies are currently under way comparing the results of medical versus surgical therapies in randomized patients with unstable angina. Long-term follow-up will be required to determine the effect of surgery on the mortality of this disease state.
Long-term Follow-up Results
Follow-up of our 76 survivors of coronary bypass surgery has indicated complete or good relief of angina in over 800f0 [1]. The majority of patients have returned to work. Objective testing by treadmill stress testing in 56 of the 76 survivors demonstrated a definite ischemic response in 49 Ofo of the patients. This high rate of positive treadmill test results may reflect the general severity of the patient's atherosclerosis, or may suggest that there are other significant reasons for pain relief than increased coronary blood flow. The mean follow-up of this surgical group has been 20 months. There have been 12 late myocardial infarctions (16 Ofo) and 2 late deaths in the 74 operative survivors.
Although the natural history of unstable angina pectoris is still poorly understood, there is a definite increased risk of infarction and death in the first 3-6 months, compared to stable angina [2,4]. Patients should be treated intensively in the hospital when they present with crescendo or rest angina. Over 75 % of patients 'cool down', at which time elective coronary bypass surgery can be undertaken with potentially small increase of risk to the patient. Urgent study and consideration of surgery is indicated in the patient with continuing rest pain, but at a higher risk of complications or death. Bypass surgery should be considered in those patients with 2- or 3-vessel occlusive disease, proximal left anterior descending coronary artery or main left coronary artery involvement. Bypass surgery for single right coronary artery disease is optional and should be decided on the basis of disability from angina. Operative mortality is 5-10 Ofo or less, with increased risk associated with continuing pain, congestive heart failure and increased age. Long-term results indicate an excellent pain relief, but a 15-percent incidence of infarction in the first 18-20 months and low
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Conclusion
SCHROEDER/BERNDT/HARRISON
58
« 3 Ofo) mortality. Treadmill exercise testing shows an ischemic response in 50 0/0 of survivors and may reflect the general severity of the coronary atherosclerosis in these patients. References
2
3 4
5
BERNDT, T. B.; MILLER, D. c.; SILVERMAN, J. F.; STINSON, E. B.; HARRISON, D. C., and SCHROEDER, 1. S.: Coronary bypass surgery for unstable angina pectoris. Clinical follow-up and results of postoperative treadmill ECG's. Amer. J. Med. (in press). GAZES, P. C.; MOBLEY, E. M.; FARIS, H. M., jr.; DUNCAN, R. C., and HUMPHRIES, G. B.: Preinfarctional (unstable) angina. A prospective study ten year follow-up. Circulation 48: 331-337 (1974). HARRISON, D. C. and SHUMWAY, N. E.: Evaluation and surgery for impending myocardial infarction. Hosp. Pract. 7: 53-58 (1972). LOPES, M. G.; SPIVACK, A. P.; HARRISON, D. C., and SCHROEDER, J. S.: Prognosis in coronary care unit non-infarction cases. J. amer. med. Ass. 228; 1558-1562 (1974). MILLER, D. C.; CANNOM, D. S.; FOGARTY, T. J.; SCHROEDER, J. S.; DAILY, P.O., and HARRISON, D. C.: Saphenous vein coronary artery bypass in patients with 'pre-infarction angina'. Circulation 47: 234-241 (1973).
Author's address: Dr. JOHN S. SCHROEDER, M.D., Cardiology Division, Stanford University School of Medicine, Stanford, CA 94305 (USA)
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1
Indications for Surgery in the Patient with 'Impending Myocardial Infarction' (Unstable Angina Pectoris/ JOHN S. SCHROEDER, THEODORE B. BERNDT and DONALD C. HARRISON Cardiology Division, Stanford University School of Medicine, Stanford, Calif.
Introduction
Renewed interest in defining patients with 'impending myocardial infarction', or unstable angina pectoris, and the pathophysiology associated with it has become apparent for 3 reasons: (1) the current success of coronary bypass surgery, with a low mortality, in alleviating disability resulting from stable angina pectoris; (2) recent emphasis on reports suggesting prehospital mortality of 40-50 % and in-hospital mortality of 10-200/0 after a myocardial infarction occurs, and (3) the belief that application of coronary bypass surgery preinfarction could prevent this morbidity and mortality, with a similarly low operative risk to the patient. In this report, we outline our current impressions of the clinical syndrome of 'impending myocardial infarction', or unstable angina pectoris, including its definition, diagnosis, initial treatment, indications and complications of coronary arteriography, indications and complications of coronary bypass surgery and follow-up of patients undergoing these procedures.
Background
1 This work was supported in part by NIH Grant No. HL-5866 and Program Project Grant No. NIH I-POI-HL-lS833-01.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
In the 1950s there was a surge of interest in the syndrome of 'preinfarction angina' when it was thought that anticoagulation might avert the actual infarction. Uncontrolled studies reported myocardial infarction
SCHROEDER/BERNDT/HARRISON
49
rates as high as 40 Ofo within 3 months after onset of the 'preinfarction' syndrome. Interest then waned when it became apparent that anticoagulation would not have a major impact on altering the natural history of a patient with unstable angina. Over the last 5 years, as it became apparent that aorto-coronary bypass surgery could be performed with a surgical mortality of less than 5 Ofo, with over 75 Ofo of patients achieving good or complete relief of their angina pectoris, and in uncomplicated cases with a mortality of 10f0 (and 85 Ofo relief of angina), attention has again turned to the 'preinfarction angina' patient. Several papers in medical literature demonstrate that patients can come to surgery on an urgent or emergency basis for their 'impending myocardial infarctions' [3,5]. Morbidity and mortality figures vary greatly, as do the indications for surgery and treatment. The experience at Stanford University Hospital over the past 3 years with the syndrome, its course, and immediate and long-term results of the surgery in 81 patients form the basis for this report.
Although the terms 'impending myocardial infarction', and 'preinfarction angina' are generally used, this diagnosis must obviously be made retrospectively, since all patients do not progress to infarction. Other terms such as 'coronary insufficiency', 'intermediate syndrome' and 'rest angina' have been variously applied. We have chosen the term 'unstable angina pectoris' to reflect the unpredictable and highly variable, yet potentially serious outcome of this state. This term has also been accepted by the Cooperative Study Group sponsored by the National Heart and Lung Institute to investigate medical and surgical therapies for the syndrome. The patient with unstable angina pectoris seems to be precariously balanced, with episodes of ischemic pain during minimal provocation. These clinical data suggest that viable myocardium is on the edge of not receiving adequate coronary circulation and oxygen delivery and could advance to infarction with minimal further change. It is this physiologic concept on which the coronary bypass surgery and its concomitant delivery of blood past occluded areas is based. Our current definition of 'preinfarction angina' includes the following. 1. Onset of new angina in a previously asymptomatic patient, particularly if of crescendo nature.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Definition and Classification
SCHROEDER/BERNDT/HARRISON
50
2. Recent change (less than 4 weeks) in the character of the angina, with increasing severity and frequency and decreasing responsiveness to vasodilators. 3. Onset of one or more episodes of prolonged chest pain (greater than 15 min) requiring hospitalization, but not progressing to frank infarction on the basis of serial electrocardiogram and enzymes. 4. Those patients with continuing rest pain after the first 24 h of hospitalization. In our opinion, these patients have a more severe and life-threatening form of the unstable angina state.
Clinical Profile
The profile of the first 81 patients studied and operated on for unstable angina pectoris is outlined in table I. Approximately 50 Ofo had had previously documented myocardial infarction and the majority had one or more coronary artery disease risk factors. The duration of stable angina varied from 2 weeks to 13 years, with a mean of 34 months. Physical examination was not helpful in establishing the diagnosis and was usually normal in regard to the cardiovascular system.
The most common abnormalities are ST segment changes, primarily ST depression which is transitory. Rarely, a patient will show ST elevation consistent with Prinzmetal's variant angina. Residual abnormalities include flat or inverted T waves during and after pain episodes, which may resolve over several pain-free days. Normal electrocardiograms are not uncommon; however, lack of ST-T wave changes during the actual pain episode would suggest an etiology other than myocardial ischemia for the chest pain. The appearance of new Q waves indicates a transmural infarction, even without serial enzyme changes. Figure 1 demonstrates serial electrocardiographic changes in a 48-yearold woman who appeared at the emergency room several times over a period of 10 days with severe chest pain, each time refusing hospital admission. She was finally admitted with an acute anterior myocardial infarction and died in cardiogenic shock 2 days later.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Electrocardiographic Findings
Impending Myocardial Infarction
51
Table I. Clinical profile Number Total patients (men/women) Mean age, years (range) Coronary artery disease risk factors 1 (average per patient) Duration of stable angina pectoris, mean, months (range) Previous myocardial infarction
81 (66/15) 53 (36-71) 2.1 34 (0.5-16.0) 42
1 Hypertension, cigarette-smoking, abnormal lipids, family history of premature coronary artery disease.
Table II. Associated hemodynamic abnormalities in unstable angina pectoris Triple product changes
Group I Group II
pain-free
during spontaneous pain
during pacinginduced angina
normal normal
increased no change
increased slight increase only
We have performed chronic hemodynamic monitoring with pulmonary and arterial catheters for 24-72 h in 60 patients with unstable angina. Resting pain-free hemodynamics are consistently normal. At the onset of angina, there are several hemodynamic groups. One group has preceding rises in systolic blood pressure and heart rate, finally culminating in angina, secondary to increased left ventricular work. Another group has no demonstrable alterations in left ventricular work, as measured by systolic blood pressure, heart rate, and ejection times (table II). Changes in coronary circulation may be responsible for the rest angina in this patient group. Studies of pacing-induced angina episodes in our laboratory have also demonstrated wide variations in triple product from rest angina episodes, again indicating that the unstable anginal state may reflect an unstable coronary circulation in some patients.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Hemodynamic Abnormalities
52
SCHROEDER/BERNDT/HARRISON
~ II
~ III
~
~ AVL
~
AVF
~
tttTn~
ttftH V2
V
~
ttftt+~ a
~
~
"'
~
~ .
V2
friftvt
~
~
~
~ Vs
~ ~
~
Fig.I. Serial electrocardiograms showing ST depression V2 - 4 on 26.1.1973 (a); symmetrically inverted T waves V2 - 4 on 29. 1. 1973 (b); partial resolution of T wave abnormalities by 3. 2.1974 (c); frank anteroseptal infarction on 6. 2.1973 (d).
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
b
Impending Myocardial Infarction
53
I
~ II
~
AVR
~ AVL ---J
,I
-l
"
AVF ~ V4
J--..l_-.!v~ll .1 ~ -r - -V ~r--rrr V5 I
V2
~
ttttH~ H-f-H~
c
I
~
~ AVL " ~ ~ III
AVF
~ ~
~
d
~ V5
~
~ Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
~ ~
V4
SCHROEDER/BERNDT/HAluusON
54
Medical Treatment
In our experience, approximately 75 Ofo of patients admitted to a coronary care unit with unstable angina will 'cool down', or stabilize, within 24-48 h. On admission, particular attention should be given to factors which might have precipitated the unstable state: (1) emotional tension; (2) anxiety; (3) hypertension; (4) congestive heart failure; (5) occult aortic stenosis, and (6) anemia. These associated factors should be treated intensively, if present, and their resolution may return the patient to a stable course. In general, treatment consists of the same care as for a patient with an acute myocardial infarction: rest, quiet, sedation and pain relief with vasodilators with and without narcotics (table III). After initial hospitalization, evaluation and stabilization, a decision can be made concerning coronary arteriography and coronary bypass surgery. In the patients who continue to have rest angina in the coronary care unit, consideration should be given to treatment with propranolol (40-240 mg/day), particularly if they continue to have resting hypertension or tachycardia. In view of their serious prognosis, this group should also be considered for urgent coronary arteriography and early bypass surgery.
Although initial reports have suggested that as many as 20 Ofo of unstable angina patients might have normal coronary arteries at the time of study, typical ischemic chest pain, particularly if associated with transient ST-T wave changes, makes this finding unlikely. It is our impression that there is no increased risk to arteriography if the patient has been pain-free for at least 24 h prior to study. In the small patient group with continuing pain, there is probably a slightly increased risk of infarction or death from the study. Table IV indicates the findings on coronary arteriography and left ventricular angiography in our patients. The majority of patients had 2- or 3-vessel disease, and most of these patients had associated abnormalities of contraction on angiography. We have been unable to demonstrate a difference between the anatomy of these patients and those with stable angina pectoris.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Coronary Arteriography
Impending Myocardial Infarction
55
Table III. Initial medical treatment of unstable angina General treatment 1. Rest 2. Sedation 3. Pain relief (a) Nitroglycerin (b) Narcotics 4. Oxygen 5. Anticoagulation optional 6. p-blockade optional Specific treatment 1. Hypertension 2. Heart failure 3. Anemia 5. Arrhythmias, particularly atrial fibrillation or atrial flutter 6. Evaluation for associated valvular disease
Table IVa. Coronary arteriographic anatomy of unstable angina pectoris (total patients, 81) Vessels with> 70 Ofo occlusion
Number of patients
1
2
3
12
48
21
Table IVb. Coronary arteriographic anatomy of unstable angina pectoris (total patients, 81)
Number of patients
normal
hypokinesia akinesia
dyskinesia
25
12
14
26
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Left ventricular angiogram
SCHROEDER/BERNDT/HARRISON
56
Table V. Factors increasing operative risk in unstable angina pectoris
Continuing pain Congestive heart failure Ejection fraction < 50 % Hypotension Pump time Female sex Number of atherosclerotic risk factors
Immediate or emergency coronary bypass surgery is being practiced or advocated by many institutions at the present time. Mortality figures are undoubtedly higher in the unstable angina patient, generally reported as 5-10 Ofo. Recently it has been our experience that mortality can approach that of stable angina in the patients who cool down and are pain-free at the time of study and surgery. In the last 35 patients with unstable angina pectoris operated on at Stanford University Hospital there have been no deaths. Despite this, it is the smaller patient group with progressive and recurrent pain who are probably at highest risk of progressing to a myocardial infarction or death, and in whom bypass surgery may have a true prophylactic effect on survival. Data are not available at present, however, to prove this point. Our current indications for surgery include: (1) severe 2- or 3-vessel occlusive disease; (2) continuing rest angina with 1-, 2- or 3-vessel disease; (3) main left occlusive disease of > 50 Ofo; (4) proximal left anterior descending lesion of > 70 Ofo; (5) occlusive disease of the right coronary artery alone is optional and indications relate primarily to relief of angina rather than prophylaxis, and (6) continuing disability from stable angina after resolution of the unstable state. Table V outlines proven or suspected factors in increasing the risk of surgery in stable angina patients. Most of these factors also apply to the unstable angina patient. The incidence of perioperative myocardial infarction was 16 Ofo in the first 81 patients operated upon. Criteria for intraoperative infarction included appearance of new Q waves and serum glutamic oxalo-acetic transaminase (SGOT) rises over 100 U. This infarction rate is similar to other reports in the medical literature.
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Indications for Surgery
Impending Myocardial Infarction
57
Two cooperative studies are currently under way comparing the results of medical versus surgical therapies in randomized patients with unstable angina. Long-term follow-up will be required to determine the effect of surgery on the mortality of this disease state.
Long-term Follow-up Results
Follow-up of our 76 survivors of coronary bypass surgery has indicated complete or good relief of angina in over 800f0 [1]. The majority of patients have returned to work. Objective testing by treadmill stress testing in 56 of the 76 survivors demonstrated a definite ischemic response in 49 Ofo of the patients. This high rate of positive treadmill test results may reflect the general severity of the patient's atherosclerosis, or may suggest that there are other significant reasons for pain relief than increased coronary blood flow. The mean follow-up of this surgical group has been 20 months. There have been 12 late myocardial infarctions (16 Ofo) and 2 late deaths in the 74 operative survivors.
Although the natural history of unstable angina pectoris is still poorly understood, there is a definite increased risk of infarction and death in the first 3-6 months, compared to stable angina [2,4]. Patients should be treated intensively in the hospital when they present with crescendo or rest angina. Over 75 % of patients 'cool down', at which time elective coronary bypass surgery can be undertaken with potentially small increase of risk to the patient. Urgent study and consideration of surgery is indicated in the patient with continuing rest pain, but at a higher risk of complications or death. Bypass surgery should be considered in those patients with 2- or 3-vessel occlusive disease, proximal left anterior descending coronary artery or main left coronary artery involvement. Bypass surgery for single right coronary artery disease is optional and should be decided on the basis of disability from angina. Operative mortality is 5-10 Ofo or less, with increased risk associated with continuing pain, congestive heart failure and increased age. Long-term results indicate an excellent pain relief, but a 15-percent incidence of infarction in the first 18-20 months and low
Downloaded by: University of Cambridge 131.111.164.128 - 1/31/2019 4:32:20 PM
Conclusion
SCHROEDER/BERNDT/HARRISON
58
« 3 Ofo) mortality. Treadmill exercise testing shows an ischemic response in 50 0/0 of survivors and may reflect the general severity of the coronary atherosclerosis in these patients. References
2
3 4
5
BERNDT, T. B.; MILLER, D. c.; SILVERMAN, J. F.; STINSON, E. B.; HARRISON, D. C., and SCHROEDER, 1. S.: Coronary bypass surgery for unstable angina pectoris. Clinical follow-up and results of postoperative treadmill ECG's. Amer. J. Med. (in press). GAZES, P. C.; MOBLEY, E. M.; FARIS, H. M., jr.; DUNCAN, R. C., and HUMPHRIES, G. B.: Preinfarctional (unstable) angina. A prospective study ten year follow-up. Circulation 48: 331-337 (1974). HARRISON, D. C. and SHUMWAY, N. E.: Evaluation and surgery for impending myocardial infarction. Hosp. Pract. 7: 53-58 (1972). LOPES, M. G.; SPIVACK, A. P.; HARRISON, D. C., and SCHROEDER, J. S.: Prognosis in coronary care unit non-infarction cases. J. amer. med. Ass. 228; 1558-1562 (1974). MILLER, D. C.; CANNOM, D. S.; FOGARTY, T. J.; SCHROEDER, J. S.; DAILY, P.O., and HARRISON, D. C.: Saphenous vein coronary artery bypass in patients with 'pre-infarction angina'. Circulation 47: 234-241 (1973).
Author's address: Dr. JOHN S. SCHROEDER, M.D., Cardiology Division, Stanford University School of Medicine, Stanford, CA 94305 (USA)
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