Probability Of Acute Myocardial Infarction Research Articles

Does medical audit lead to explicit standards? Experience with thrombolysis in four UK hospitals.

The setting of explicit standards against specific criteria is a recognized part of the medical audit cycle, but often in practice it has been neglected, implicit judgements being used instead. The conduct of a study to evaluate audit among physicians in four UK district general hospitals provided an opportunity to encourage the setting of explicit standards and observe the results. The subject chosen for audit by the participating physicians was the extent of use of intravenous thrombolysis in patients with suspected acute myocardial infarction (AMI). Standard setting was requested at initial peer review meetings held to review baseline results. This was followed up by a written request to lead consultants and subsequent telephone calls. Two out of the four participating hospitals set technical standards, which excluded patients with contra-indications from the denominator. The other two hospitals set population standards as requested, one with considerable reluctance and scepticism. Each hospital set separate standards for definite AMIs and for probable AMIs. Six out of the eight standards set were achieved in at least one of four audits conducted in each hospital. Time trends were difficult to interpret because of small numbers. The amount of discussion between the lead consultant and colleagues about standards was highly variable, but there was no clear relationship between the process for agreeing standards in a particular hospital and subsequent attainment.

Cost-effectiveness of a Coronary Care Unit Versus an Intermediate Care Unit for Emergency Department Patients With Chest Pain

Guidelines are not available for which patients with acute chest pain should be admitted to the coronary care unit and which patients can be reasonably triaged to monitored beds in lower levels of care. Clinical and resource utilization data from 12 139 emergency department patients with acute chest pain were used in a decision-analytic model to identify cost-effective guidelines for the admission to a coronary care unit versus an intermediate care unit for initially uncomplicated patients without other indications for intensive care. The probability of clinical complications and death were derived from data on age-specific subsets of the population. Resource utilization estimates were based on cost data from a subset of 901 patients and length of stay data for the entire cohort. The survival benefit associated with initial triage to the coronary care unit instead of an intermediate care unit was assumed to be 15%. In the baseline analysis for 55- to 64-year-old patients, the probability of acute myocardial infarction (AMI) at which the coronary care unit had an incremental cost-effectiveness below $50 000 per year-of-life-saved was 29%. Triage to the coronary care unit was somewhat more cost-effective in elderly patients because their higher early complication rate more than offset their shorter life expectancy. This analysis indicates that the coronary care unit usually should be reserved for patients with a moderate (21% or more, depending on the patient's age) probability of AMI unless patients need intensive care for other reasons. Clinical data suggest that only patients with ECG changes of ischemia or infarction not known to be old have a probability of AMI this high. Intermediate care units are appropriate for patients whose risks are not high enough for a coronary care unit to be cost-effective but too high for other alternatives to be recommended for safety and effectiveness.

Prognosis and gender differences in chest pain patients discharged from an ED.

A large proportion of patients evaluated for chest pain in the emergency department (ED) will be sent home because the probability of acute myocardial infarction, unstable angina, or other severe disease processes is determined to be sufficiently low. Patients who came to the ED at Sahlgrenska Hospital, Göteborg during a 21-month period because of chest pain were registered and followed up for one year. Survivors after one year were asked to complete a mailed questionnaire regarding different kinds of symptoms. Of 5,362 patients evaluated in the ED, 2,175 were sent home on their first visit. Fifty-four percent were men and 46% were women. The one-year mortality rate was 3% in men and 3% in women. Recurrent chest pain, dyspnea, and psychological symptoms were more frequently reported by patients with known cardiac disease than by patients without cardiac disease. Female patients with and without cardiac disease reported significantly more frequent recurrent chest pain, dyspnea, and psychological and psychosomatic complaints than male patients with and without cardiac disease. These data suggest that there are specific gender differences between men and women who are discharged from the ED after being evaluated for chest pain. In particular, psychological gender differences may exist and need to be addressed when evaluating patients with chest pain.

959-103 A Systematic Approach to the Evaluation of Chest Pain in the Emergency Department: A Prospective Risk Assessment and Treatment Protocol Based on Patient Presentation, ECG and Rest Technetium 99m-Sestamibi

Ideal treatment of acute myocardial infarction (AMI) and unstable angina (UA) require rapid evaluation and triage in the ED. Appropriate patient triage and disposition can reduce admissions and optimize resource utilization including reduced CCU length of stay (LOS). Historically less than 20 percent of patients admitted with chest pain (CP) rule in for AMI. However, all patients must be initially evaluated in the same fashion until the risk of AMI or UA can be determined and appropriate treatment initiated. Given the diagnostic limitation of the presenting symptoms and initial ECG, we designed and are prospectively testing a systemic protocol to evaluate all patients who present to the ED with CP. All patients are assigned to one of five levels based on risk and probability of AMI and of ischemia: 1. AMI; 2. Probable AMI/UA; 3. Possible AMI/UA; 4. Possible UA; and 5. Non-cardiac CP. In the absence of a diagnostic ECG needed for assignment to level l, (ST elevation), or level 2, (ST depression), immediate injection of Tc99m-sestamibi in the ED is used to further stratify patients in levels 3 and 4. If the evaluation of any given patient becomes positive, the assigned level is increased to one of higher risk with appropriate changes in therapy. Since January 1994, 560 patients with potential cardiac chest pain have been enrolled into levels 1–4. Level 5 patients were treated for obvious non-cardiac causes. Predicted risk of AMI with distribution of patients and actual incidence of AMI is as follows: Level Predicted Risk of AMI % Patients AMI (%) CCU LOS 1 >95% 4% 100% 2.9 days 2 50-95% 31% 21% 1.7 days 3 5-50% 23% 3% 21 hrs 4 <5% 42% 0% 0 There were no in-hospital deaths in any of these patients. This protocol appears safe, can be systematically applied to include all patients who present with CP, and will thus help maximize resource utilization by appropriately triaging patients and reducing LOS.

Cost-effectiveness of a new short-stay unit to “rule out” acute myocardial infarction in low risk patients

Objectives. This study attempted to determine the safety and costs of a new short-stay unit for low risk patients who may be admitted to a hospital to rule out myocardial infarction or ischemia.Background. One strategy to reduce the costs of ruling out acute myocardial infarction in low risk patients is to develop alternatives to coronary care units.Methods. The short-term and 6-month clinical outcomes and costs for 592 patients admitted to a short-stay coronary observation unit at Brigham and Women's Hospital with a low (≤ 10%) probability of acute myocardial infarction were compared with those for 924 consecutive comparison patients who were eligible for the same unit but were admitted to other hospital settings or discharged home. Actual costs were calculated using detailed cost-accounting methods that incorporated nursing intensity weights.Results. The rate of major complications, recurrent myocardial infarction or cardiac death during 6 months after the initial presentation of the 592 patients admitted to the coronary observation unit was similar to that of the 924 comparison patients before and after adjustment for clinical factors influencing triage and initial diagnoses (adjusted relative risk 0.86, 95% confidence interval 0.49 to 1.53). Their median total costs (25th, 75th percentile) at 6 months ($1,927; 1,455, 3,650) were significantly lower than for comparison patients admitted to the wards ($4,712; 1,868, 11,187), to stepdown or intermediate care units ($4,031; 2,069, 9,169) or to the coronary care unit ($9,201; 3,171, 20,011) but were higher than for comparison patients discharged home from the emergency department ($403; 403, 927) before and after the same adjustments (all adjusted p < 0.0001).Conclusions. These data suggest that the coronary observation unit may be a safe and cost-saving alternative to current triage strategies for patients with a low risk of acute myocardial infarction admitted from the emergency department. Its replication in other hospitals should be tested.

Long‐term prognostic value of a normal dipyridamole thallium‐201 perfusion scan

In a 4-year period, 84 patients who were referred for a dipyridamole thallium-201 stress test to rule out significant coronary artery disease had normal scans. A dipyridamole study was recommended instead of exercise because of arthritis, severe obesity, peripheral vascular disease, pulmonary disease, other chronic illnesses, or combinations of these problems. All patients had three-view (i.e., anterior, shallow left anterior oblique, and steep left anterior oblique) planar thallium-201 imaging 10 minutes and 3.5 hours after administration of 0.6 mg/kg of intravenous dipyridamole. The patients were followed for 42 +/- 13 (range 1-58) months to document the cardiac event rate. Of the 84 patients with normal results, 14 died during the follow-up period from noncardiac causes. Three other patients died 29-51 months after the test due to an acute myocardial infarction, a probable acute myocardial infarction, and sudden cardiac death, respectively. Of the survivors, 5 suffered an acute myocardial infarction 28-50 months after the dipyridamole thallium scan and 1 had coronary artery bypass grafting due to increasing angina pectoris 58 months after the scan (overall cardiac event rate of 0.4% per year). Of the remaining 61 patients, 39 (64%) were asymptomatic, 20 (33%) had the same symptoms they had at the time of testing without significant deterioration, while 2 patients (3%) had deterioration of their chest pains but no cardiac complication. Thus, in this group of patients, a normal dipyridamole thallium-201 perfusion scan predicted a good cardiovascular outcome for at least 24 months following the test.

Outcome of patients who were admitted to a new short-stay unit to “rule-out” myocardial infarction

For emergency room patients with a low probability of acute myocardial infarction, we established a new short-stay coronary observation unit, a 2-bed nonintensive care unit with telemetry monitoring adjacent to the emergency room. Of 512 consecutive admissions to the coronary observation unit, 425 (83%) were discharged home without evidence of acute myocardial infarction or serious complications (mean length of stay, 1.2 days; median length of stay, 1 day); 87 (17%) were transferred to other hospital beds. The rate of acute myocardial infarction was 3%. No deaths and only 1 serious complication occurred in the coronary observation unit. At 6 month follow-up, the cardiac survival rate was 99% for patients sent home directly from this unit. It is concluded that the coronary observation unit is safe and adequate for ruling out acute myocardial infarction in a defined subset of patients. Short-stay units, however, encourage early discharges which, when premature, may miss patients who are at risk of having complications shortly thereafter. Strategies such as mandatory but expeditious predischarge stress testing to encourage early but not premature discharge may augment the efficiency of coronary observation units.

Neural Network Analysis of Serial Cardiac Enzyme Data A Clinical Application of Artificial Machine Intelligence

There has been a recent resurgence of interest in the study and application of computerized neural networks within the broad field of artificial intelligence. These "intelligent machines" are modeled after biological nervous systems and are fundamentally different from the many computerized expert systems that previously have been introduced as clinical decision-making aids. The authors describe a neural network designed and trained to predict the probability of acute myocardial infarction (AMI) based on the analysis of paired sets of cardiac enzymes. The neural network predicted 24 of 24 (100%) AMIs and 27 of 29 (93%) No-AMIs when compared with a pathologist's interpretation of the patient's laboratory data (P less than 0.000001). The authors attempted to validate the network's diagnoses by two independent methods. When compared with echocardiogram and EKG for diagnosis of AMI, the neural network agreed with the cardiologist's interpretation in 12 of 14 (86%) AMIs and 1 of 3 (33%) No-AMIs, but the correlation was not statistically significant. Using autopsy outcome for validation, the neural network agreed with the anatomic evidence in 24 of 26 (92%) AMIs and 4 of 6 (67%) No-AMIs (P = 0.001). The authors conclude that neural networks can be successfully applied to the analysis of cardiac enzyme data and suggest that broader applications exist within the domain of clinical decision support.

Gemfibrozil Cost-Benefit Study

This cost-benefit analysis attempts to translate the clinical findings of the Helsinki Heart Study (HHS) and published results regarding additional cardiovascular conditions into economic terms meaningful to US managed care providers. The study has the following 3 key objectives: to define the cost effectiveness of gemfibrozil in the prevention of coronary heart disease (CHD); to assess the net impact of gemfibrozil on total treatment costs for CHD; and to identify those patient groups for whom gemfibrozil therapy is most cost effective. In order to reach these findings a cost-effectiveness model was constructed based on original clinical data provided by the HHS, published findings for CHD risk and cost of treatment in the US, expert opinion and extension of HHS to other cardiovascular conditions, and documented costs and treatment protocols of US Medicaid and privately managed health care programmes. The model was applied to the California Medicaid (Medi-Cal) programme to estimate costs of hyperlipidaemia therapy using gemfibrozil. In parallel, savings to Medi-Cal from averted coronary events were estimated. From these data, the net expected savings to Medi-Cal were calculated. The probability of experiencing CHD varies with cholesterol level, age, sex and risk factors such as smoking, hypertension and diabetes. Therefore, it is possible to use risk-factor profiles to define groups of individuals with low, moderate or high risk of experiencing acute myocardial infarction (AMI) or sudden cardiac death. The probability of a cardiac event within 5 years ranges from 1.1% in a 45-year-old low risk male to over 36% in a 55-year-old high risk male. The average total cost of CHD care was found to be US$22,271 within 5 years. Using the probability of a CHD event to calculate the expected 5-year cost of CHD care produces a range from US$242 in the 45-year-old low risk male to US$8084 in the 55-year-old high risk male. Treatment with gemfibrozil reduces the probability of AMI and sudden cardiac death events by 34%, as demonstrated in the HHS. Therefore, the corresponding probability ranges are reduced to 0.7% in the 45-year-old low risk male and 27.3% in the 55-year-old high risk male after treatment with gemfibrozil. The expected cost of a coronary event is reduced by US$82 and US$1997, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Clinical characteristics and outcome of acute myocardial infarction in patients with initially normal or nonspecific electrocardiograms (a report from the Multicenter Chest Pain Study)

To determine the prevalence and characteristics of acute myocardial infarction (AMI) patients who present to emergency departments with normal or nonspecific electrocardiograms (ECGs), data were analyzed from 7,115 consecutive patients in the Multicenter Chest Pain Study. AMI patients with normal or nonspecific initial ECGs (n = 107) were less likely to have a past history of coronary artery disease or to be diaphoretic on presentation (p < 0.01) than AMI patients with initial ECGs highly suggestive of AMI (n = 811). The overall probability of AMI among patients with chest pain and initially normal or nonspecific ECGs was 3%, but ranged from <1 to 17% depending on the patient's age and sex and whether the patient had pressuretype pain or pain radiating to the shoulder, neck or arms. Among initially admitted patients, the time elapsed between onset of pain and presentation was similar in both groups. However, the time between onset of pain and definitive diagnosis of AMI by enzymes or clinical course was longer in patients with initially normal or nonspecific electrocardiograms (8.3 vs 7.5 hours, p < 0.05), their peak creatine kinase levels were lower (mean 643 vs 1,032 mg/dl, p < 0.001) and their mortality was slightly tower (6 vs 12%, p = 0.10). These findings suggest that AMI patients with initially normal or nonspecific ECGs may have a less severe shortterm clinical outcome.

How many myocardial infarctions should we rule out?

We used computer simulation to estimate the consequences of four admitting strategies (coronary care unit, intermediate care unit, routine ward care, or outpatient follow-up) on cost, outcome, admission threshold probabilities, and false-positive admission rates for patients with acute myocardial infarction. At virtually any probability of acute myocardial infarction, replacing more intensive by less intensive strategies saved money but increased mortality and decreased life expectancy. Therefore, choices among strategies may be made by using the most effective strategy for progressively lower and lower risk patients until the additional cost per additional life saved reaches a cutoff value; then, a less expensive strategy is selected. With sample cutoff values of $1 and $2 million per life saved, the marginal threshold admission probabilities were: (table; see text) These results imply that the acceptable proportion of false-positive admissions may be as high as 70% to 80%; lower rates could indicate excessively restrictive admitting policies. Clinicians may be operating closer to the optimal decision point than has previously been asserted.

Origin of the right from the left main coronary artery (single coronary ostium in aorta)

Origin of both the right and left main (LM) coronary arteries from the aortic wall of the right sinus of Valsalva frequently is a lethal anomaly. 1 Origin of both the right and LM coronary arteries from the aortic wall of the left sinus of Valsalva, in contrast, usually is a benign anomaly. 2 Although many studies have described origin of both LM and right coronary arteries from the aortic wall of the same sinus of Valsalva, few 1,2 have described origin of the right coronary artery from the LM. Husaini et al 3 described angiographic features of this anomaly in a 52-year-old man who underwent selective coronary angiography after probable acute myocardial infarction. Muus and McManus 4 described this anomaly in a fullterm stillborn infant who also had a bicuspid aortic valve. Whether the coronary anomaly played a role in the stillbirth is uncertain. In both of these previously described patients, the anomalously arising right coronary artery coursed between aorta posteriorly and the pulmonary trunk anteriorly.

Care of patients with a low probability of acute myocardial infarction. Cost effectiveness of alternatives to coronary-care-unit admission.

We conducted a cost-effectiveness analysis to examine the clinical and economic consequences of alternatives to admission to a coronary-care unit for patients who have a relatively low probability of acute myocardial infarction. Despite the fact that all our assumptions were slanted to favor the current standard policy of admission to a coronary-care unit, our analysis shows that admission to an intermediate-care unit providing resuscitative facilities and prophylactic lidocaine is highly cost effective. For patients with about a 5 per cent probability of infarction, admission to a coronary-care unit would cost $2.04 million per life saved and $139,000 per year of life saved, as compared with intermediate care. For the expected number of such patients annually in the United States, the cost would be $297 million to save 145 lives. At probabilities of infarction up to about 20 per cent, the incremental cost to save a year of life by choosing a coronary-care unit over an intermediate-care unit would be higher than the estimated cost of saving a year of life by treating a 40-year-old man with mild hypertension. Our results suggest that many patients who have a low risk of acute myocardial infarction would be appropriate candidates for admission to an intermediate-care unit.

Serial myocardial scintigraphy after a single dose of thallium-201 in men after acute myocardial infarction

Serial myocardial scintigraphy after a single dose of thallium-201 in the period immediately after myocardial infarction may demonstrate redistribution of thallium-201 into perfusion defects that were evident in the initial scan. This study tested the hypothesis that evaluation of this redistribution, available within hours of infarction, could provide a more accurate estimate of the eventual perfusion defect than a single thallium-201 Image obtained immediately after infarction. The study group comprised 14 patients with a diagnosis on admission of probable acute myocardial infarction. The patients received thallium-201 a mean of 1.3 hours after admission to the coronary care unit. Imaging began 10 minutes after the thallium injection and was repeated 4 to 8 hours later. Eight patients with acute myocardial infarction had a definite reduction in one or more perfusion defects on serial scintigraphy, possibly indicating reperfusion of transiently Ischemic zones. Two patients with acute infarction had an increase in perfusion defects in a second study performed 6 hours after the initial scintigram. In the interval between scans, one patient had a cardiac arrest with clinical evidence of infarct extension after successful resuscitation; the other sustained a lateral extension of the infarct. One patient with acute aortic dissection had normal scans on both studies. All three patients with unstable angina had an abnormal initial scan; on repeat scan, the thallium-201 defect was unchanged in one patient, increased in one and decreased in the third. In the patients with myocardial infarction, repeat thallium-201 scans corresponded more nearly than the initial scans to the extent of technetilum-99m stannous pyrophosphate uptake by the heart. These data suggest that serial myocardial imaging with thallium-201 immediately after myocardial infarction can overcome some of the limitations of a single thallium-201 scintigram and may be useful in delineating ischemic from infarcted myocardium in the postinfarction period.

The early posthospital phase of myocardial infarction. Prognostic stratification.

Prognostic stratification was carried out on 518 patients less than or equal to 65 years of age who were discharged from the hospital following a definite or probable acute myocardial infarction and followed for four months. The total population was made up of 272 patients hospitalzed in 1973 and 246 patients hospitalized in 1974; one hundred and forty-two variables were collected on each patient. The clinical characteristics of the 1973 and 1974 populations were remarkably similar, and both groups had a four-month posthospital cardiac mortality rate of 4%. Two prognostic stratification schemes were developed on the 1973 population which identified low and high risk groups with meaningfully different four-month cardiac death rates. Both stratification schemes were tested on the 1974 population, and one of the two schemes was validated as identifying a significantly increased cardiac mortality rate in the high as opposed to the low risk group. The four-month posthospital cardiac mortality rate was 3% in the low and 14% in the high risk group (Z = 2.70, P less than 0.003). The high risk group was characterized by two or more of the following characteristics: 1) history of angina at ordinary levels of activity or at rest; 2) CCU hypotension and/or congestive heart failure; 3) ventricular premature beat frequency greater than or equal to 20/hr on a six-hour electrocardiographic tape recording. The low risk group had none or only one of the above characteristcis. The prognostic power of this stratification scheme is such that sixteen percent of the posthospital population can be identified as high risk, and this subgroup contains forty-six percent of the patients who die of cardiac cause in the four-month posthospital interval.

Ventricular arrhythmias 3 weeks after acute myocardial infarction.

Abstract One hundred patients who were convalescing from a definite or probable acute myocardial infarction had a 6-hour ECG rhythm tape recording made just before contemplated discharge from the h...

Delay in hospitalization during the acute coronary period

Sixty-four patients with definite or probable acute myocardial infarction admitted to a coronary care unit were interviewed with regard to the time intervals and time delays during the pre-hospital period of their acute illness. The average time interval between the onset of symptoms and the patient's arrival in the hospital emergency department was 306 min., and this time was fractionated in a decision time of 200 min., 77 min. of unaccounted for time and 29 min. of transportation time. The decision time was longer in those patients who arrived by car rather than by ambulance, increased progressively with age and was twice as long for women as for men. It was three times longer when the symptom occurred on a weekend as opposed to a weekday, and it was generally longer when the symptom occurred during daylight hours than when it occurred at night. The significance of this prolonged pre-hospital delay during the acute phase of a potentially fatal illness is discussed.