Beta-blocker dosages and mortality after myocardial infarction: data from a large health maintenance organization.

BACKGROUND: Although long-term beta-blocker therapy has been found beneficial in patients after an acute myocardial infarction, these drugs are greatly underused by clinicians. Moreover, the dosages of beta-blockers used in randomized controlled trials appear to be much larger than those routinely prescribed. OBJECTIVE: To determine whether an association exists between the dosage of beta-blockers prescribed after a myocardial infarction and cardiac mortality. METHODS: We performed a retrospective cohort study of 1165 patients who survived an acute myocardial infarction from January 1, 1990, through December 31, 1992. These patients represent a subgroup of the 6851 patients hospitalized at northern California Kaiser Permanente hospitals. RESULTS: Of the 37.7% of patients prescribed beta-blocker therapy, 48.1% were treated with dosages less than 50% of the dosage found to be effective in preventing cardiac death in large randomized clinical trials (lower-dosage therapy). Compared with patients not receiving beta-blockers, those treated with lower-dosage therapy appeared to have a greater reduction in cardiovascular mortality (hazard ratio, 0.33; P=.009) than patients treated with a higher dosage (hazard ratio, 0.82; P=0.51), after adjustment for age, sex, race, disease severity, and comorbidities. CONCLUSIONS: The dosages of beta-blockers shown to be effective in randomized trials are not commonly used in clinical practice, and treatment with lower dosages of beta-blockers was associated with at least as great a reduction in mortality as treatment with higher dosages. This suggests that physicians who are reluctant to prescribe beta-blockers because of the relatively large dosages used in the large prospective clinical trials should be encouraged to prescribe smaller dosages.

Predictors of survival after coronary bypass grafting in patients with total occlusion of the left main coronary artery.

Twenty-three patients with angiographically documented total occlusion of the left main coronary artery were retrospectively identified. Statistical analysis suggests that poor right-to-left collaterals and the presence of concurrent significant right coronary artery disease were weakly associated with decreased survival after bypass surgery.

Projected cost-effectiveness of primary angioplasty for acute myocardial infarction.

OBJECTIVES: This study sought to evaluate the cost-effectiveness of primary angioplasty for acute myocardial infarction under varying assumptions about effectiveness, existing facilities and staffing and volume of services. BACKGROUND: Primary angioplasty for acute myocardial infarction has reduced mortality in some studies, but its actual effectiveness may vary, and most U.S. hospitals do not have cardiac catheterization laboratories. Projections of cost-effectiveness in various settings are needed for decisions about adoption. METHODS: We created a decision analytic model to compare three policies: primary angioplasty, intravenous thrombolysis and no intervention. Probabilities of health outcomes were taken from randomized trials (base case efficacy assumptions) and community-based studies (effectiveness assumptions). The base case analysis assumed that a hospital with an existing laboratory with night/weekend staffing coverage admitted 200 patients with a myocardial infarction annually. In alternative scenarios, a new laboratory was built, and its capacity for elective procedures was either 1) needed or 2) redundant with existing laboratories. RESULTS: Under base case efficacy assumptions, primary angioplasty resulted in cost savings compared with thrombolysis and had a cost of $12,000/quality-adjusted life-year (QALY) saved compared with no intervention. In sensitivity analyses, when there was an existing cardiac catheterization laboratory at a hospital with > or = 200 patients with a myocardial infarction annually, primary angioplasty had a cost of < $30,000/QALY saved under a wide range of assumptions. However, the cost/QALY saved increased sharply under effectiveness assumptions when the hospital had < 150 patients with a myocardial infarction annually or when a redundant laboratory was built. CONCLUSIONS: At hospitals with an existing cardiac catheterization laboratory, primary angioplasty for acute myocardial infarction would be cost-effective relative to other medical interventions under a wide range of assumptions. The procedure's relative cost-ineffectiveness at low volumes or redundant laboratories supports regionalization of cardiac services in urban areas. However, approaches to overcoming competitive barriers and close monitoring of outcomes and costs will be needed.

Effect of beta-adrenergic blocking agents on mortality rate in patients not revascularized after myocardial infarction: data from a large HMO.

We investigated whether patients who do not undergo coronary angiography and therefore any form of revascularization after a myocardial infarction derive greater benefit from chronic beta-blocker therapy than patients who undergo coronary angiography. With multivariate analyses, treatment with beta-blockers was a much stronger predictor of survival in patients who did not undergo coronary angiography (relative risk = 0.38, p = 0.005) than in those patients who did undergo catheterization (p < 0.05 for interaction). Our findings provide direct support for the recommendation by the American College of Cardiology/American Heart Association task force that beta-blocker therapy should be initiated for all infarct survivors who do not undergo revascularization and who have no contraindications.

Variation among hospitals in coronary-angiography practices and outcomes after myocardial infarction in a large health maintenance organization.

BACKGROUND: Wide geographic variation in the use of coronary angiography after myocardial infarction has been documented internationally and within the United States. An associated variation in clinical outcomes has not been consistently demonstrated. METHODS: We assessed the risk of death from heart disease and of any heart disease event (death, reinfarction, or rehospitalization) over a follow-up period of one to four years in 6851 patients hospitalized with acute myocardial infarction at 16 Kaiser Permanente hospitals from 1990 through 1992. The percentage of patients who underwent angiography within three months after infarction ranged from 30 to 77 percent. We selected a subcohort of 1109 patients from three hospitals with higher rates of angiography and four with lower rates for a record review to assess the severity of infarction, the number of coexisting conditions, treatments received, and the appropriateness and necessity of angiography, using established criteria. RESULTS: The rates of angiography were inversely related to the risk of death from heart disease (P= 0.03) and the risk of heart disease events (P<0.001) among the 16 hospitals after adjustment for age, sex, race, coexisting conditions, and the location of the infarction (subendocardial vs. transmural). In the subcohort, 440 patients met criteria indicating that angiography was necessary and 669 did not. Among the former, patients treated at hospitals with higher rates of angiography had a lower risk of death and of any heart disease event than those treated at hospitals with lower rates (hazard ratios, 0.67 and 0.72, respectively). Among the latter, the apparent benefits of being treated at hospitals with higher angiography rates were smaller (hazard ratios, 0.85 to 0.90 for death and any heart disease event, respectively). CONCLUSIONS: During the one to four years after myocardial infarction, patients treated at hospitals with higher rates of angiography had more favorable outcomes than those treated at hospitals with lower rates. This association was stronger among patients for whom published criteria indicated that angiography was necessary.

Initial cost of primary angioplasty for acute myocardial infarction.

OBJECTIVES: We sought to evaluate the initial economic cost of primary angioplasty for acute myocardial infarction under varying assumptions about whether a cardiac catheterization laboratory exists, whether services are provided during night and weekend hours and how cardiovascular surgical backup is arranged. BACKGROUND: Primary angioplasty for acute myocardial infarction has resulted in clinical outcomes superior or equal to those obtained with thrombolysis in recent studies, but its future implementation depends greatly on its cost and cost-effectiveness. There is a gap in knowledge about the true economic costs of this procedure, and understanding costs under a variety of hypothetic scenarios is important in planning whether and how the procedure should be offered to broad groups of patients. METHODS: A generalizable spreadsheet model was constructed to calculate the cost of primary angioplasty at a single hospital with assumptions based on data from a large nonprofit health maintenance organization (Kaiser Permanente). The following baseline assumptions were made: 1) A total of 200 patients with myocardial infarction presented to the hospital each year; 2) primary angioplasty was offered for 10 years; 3) the hospital had a cardiac catheterization laboratory; 4) costs of night call for technical personnel and cardiovascular surgical backup were already covered. Other scenarios were modeled to represent different assumptions about existing resources. RESULTS: Under the baseline assumptions, primary angioplasty cost $1,597/procedure. If night call for technical personnel were a new expense, the average cost would be > or = $3,206. If a new cardiac catheterization laboratory needed to be built, costs would range from $3,866 to $14,339/procedure, depending on how cardiovascular surgical backup was provided. Results were sensitive to assumptions about the annual volume of myocardial infarctions, the number of years the procedure was offered and the costs of labor, construction and equipment. CONCLUSIONS: The initial cost of providing primary angioplasty for acute myocardial infarction varies greatly, depending on the setting in which it is provided. To provide information for clinical policy decisions, a cost-effectiveness model is needed that combines these initial costs with data on survival, quality of life and rates and costs of subsequent cardiac procedures.

Primary angioplasty and thrombolysis for acute myocardial infarction: an evidence summary.

Coronary angioplasty is being increasingly used as the primary treatment for patients with acute myocardial infarction, but controversy remains over its potential adoption in preference to thrombolysis as standard care. This report summarizes the published evidence on health outcomes after primary angioplasty compared with thrombolysis or no intervention for patients with acute myocardial infarction. The data tables presented provide the scientific groundwork to assist physicians and other policy-makers in deciding which interventions to provide for broad populations of patients.

MCAT--a multimedia cardiac angiogram tool.

In this article, we present the prototype of the Multimedia Cardiac Angiogram Tool (MCAT). The MCAT provides capabilities for reviewing angiograms recorded at a cardiac catheterization laboratory. A doctor can use MCAT to annotate angiograms with audio, text, and graphics. He/she can selectively package the annotated multimedia angiograms into a document, save it as the record for the visit or use it for case presentations, or send it to another doctor over a network. MCAT streamlines data collection at a cath lab and is intended to improve the efficiency of communication and collaboration between doctors. This paper describes the design, implementation, and future directions of the prototype.

Responses of mechanoreceptive afferent units in the glabrous skin of the human hand to vibration.

The impulse response to vibration (0.5-400 Hz, 0.001-1.0 mm) was recorded from single mechanoreceptive afferents innervating the glabrous skin of the human hand. Needle electrodes inserted into the median nerve were used for the recording. The four types of mechanoreceptive afferents (FA I, FA II, SA I, and SA II) exhibited different response characteristics. Fast adapting units were the most easily excited at frequencies between about 5 to 50 Hz (FA I) and above about 50 Hz (FA II). The sensitivity of the slowly adapting units (SA I and SA II) was greatest at lower frequencies. Unit thresholds at 2, 20, and 200 Hz were measured before and after 2 min of powerful vibration exposure. Corresponding psychophysical thresholds were also measured during the recording of responses from single units. An acute but temporary depression in sensitivity occurred in the FA I, FA II, and SA I units as a consequence of the exposure. The magnitude and the time courses of the recovery of the encountered unit threshold shifts were approximately the same as those for the corresponding psychophysical threshold shifts. It was concluded that acute impairments of the tactile sensibility caused by vibration exposure, as observed in psychophysical studies, can probably be explained by an influence on the excitability of the tactile units.