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Biomedical subjects

M Bobbio

Publications and source records attributed to M Bobbio.

At least 19 recordsLinked to original sources
PubMed1992

Development and validation of a logistic regression-derived algorithm for estimating the incremental probability of coronary artery disease before and after exercise testing.

OBJECTIVES: Our goals were to develop and validate a multivariate algorithm for estimating the incremental probability of the presence of coronary artery disease. BACKGROUND: Multivariate methods, including logistic regression analysis, have been extensively applied to diagnostic exercise testing. However, few previous studies have included both an incremental design and external validation. METHODS: A retrospective collection of clinical, exercise test and catheterization data was performed involving four U.S. referral medical centers. All patients had no prior history of coronary disease and had undergone coronary angiography < or = 3 months after exercise stress testing. An algorithm was developed in one center (590 patients with a 41% prevalence of coronary artery disease) with the use of logistic regression analysis and was validated in the other three centers (1,234 patients, 70% prevalence). The algorithm incorporated pretest variables (age, gender, symptoms, diabetes, cholesterol), exercise electrocardiographic (ECG) variables (mm of ST segment depression, ST slope, peak heart rate, metabolic equivalents [METs], exercise angina) and one thallium variable. Discrimination was measured with receiver operating characteristic curve analysis. Calibration (that is, reliability) was assessed from a comparison of probability estimates and the actual prevalence of disease. RESULTS: The overall incremental receiver operating characteristic curve areas for the validation group were pretest, -0.738 +/- 0.016; postexercise ECG, 0.78 (SE 0.017); and postthallium, 0.82 (SE 0.016); p < 0.01 for both increments. Within the three validation institutions, the institution with a disease prevalence closest to that of the derivation institution had the best incremental receiver operating characteristic curve areas. There was a stepwise incremental improvement in calibration especially from exercise ECG to thallium testing. CONCLUSIONS: An incremental multivariate algorithm derived in one center reliably estimated disease probability in patients from three other centers. The incremental value of testing was best demonstrated when the derivation and validation groups had a similar disease prevalence. This algorithm may be useful in decision making that relates to the diagnosis of coronary disease.

Algorithms↗
PubMed1992

Effects of exercise test results on physician perceptions of coronary artery disease probability using a threshold analysis.

The incremental diagnostic value of exercise electrocardiographic testing compared with clinical data alone in the diagnosis of coronary artery disease (CAD) was found to be of limited value in a previous study. That study used a computer algorithm for diagnosing disease. Thus, the strict use of the results apply only to computerized disease diagnosis rather than physicians' diagnoses. The aim of the present study was to determine whether exercise test data improve a physician's ability to detect the presence or absence of CAD and 3-vessel or left main CAD, and whether the data effect the decision to perform angiography. The study sample comprised a data base of 312 patients whose clinical data, exercise test results and coronary anatomy were known. Individual cases were presented to 8 cardiologists with and without exercise data. The cardiologists provided estimates of disease probability and were asked whether they would request coronary angiography. Receiver-operating characteristic curves and goodness-of-fit analysis showed better discrimination and calibration of the estimates for the presence of CAD and 3-vessel/left main CAD after exercise test results were known. Individualized probability thresholds for deciding whether to request angiography were determined for each physician. Forty-three percent of patients crossed greater than or equal to 1 threshold, with 64% of the crossings in the correct direction. For estimating the presence of any CAD, 84% of crossings from below to above a threshold were correct, whereas only 36% from above to below were correct. For 3-vessel/left main CAD, 36% of crossings from below to above a threshold were correct, whereas 88% from above to below were correct.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1992

Computer probability estimates of angiographic coronary artery disease: transportability and comparison with cardiologists' estimates.

A computer algorithm for estimating probabilities of any significant coronary obstruction and triple vessel/left main obstructions was derived, validated, and compared with the assessments of cardiac clinician angiographers. The algorithm performed at least as well as the clinicians when the latter knew the identity of the patients whose angiograms they had decided to perform. The clinicians were more accurate when they did not know the identity of the subjects but worked from tabulated objective data. Referral and value induced bias may affect physician judgment in assessing disease probability. Application of computer aids or consultation with cardiologists not directly involved with patient management may assist in more rational assessments and decision making.

Adult↗
PubMed1992

Comparison of logistic regression and Bayesian-based algorithms to estimate posttest probability in patients with suspected coronary artery disease undergoing exercise ECG.

Two multivariate methods, a logistic regression-derived algorithm and a Bayesian independence-assuming method (CADENZA), were compared concerning their abilities to estimate posttest probability of coronary disease in patients with suspected coronary disease. All patients underwent exercise testing within 3 months prior to coronary angiography. Coronary disease was defined as the presence of one or more vessels with greater than or equal to 50% luminal diameter narrowing. A group of 300 patients (disease prevalence = 37%) was used to derive the algorithm. Another group of 950 patients was used to validate the algorithm and compare it to CADENZA. Seven variables (age, sex, symptoms, diabetes, mm ST depression, ST slope, and peak heart rate) were used to generate posttest probabilities for each method. The receiver operating characteristic curve area for the logistic regression method (0.81 +/- 0.01) was significantly higher than CADENZA (0.75 +/- 0.01; p less than 0.05). There was, however, no difference in the calibration of the two methods. When given equivalent variable information, the logistic regression algorithm had better discrimination than CADENZA for estimating the probability of coronary disease following exercise electrocardiography.

Algorithms↗
PubMed1992

Value of exercise stress test, radionuclide angiography and coronary angiography in predicting new coronary events in asymptomatic patients after a first episode of myocardial infarction.

One-hundred-and-fifty-five consecutive symptom-free patients underwent maximal treadmill exercise testing, rest and stress radionuclide angiography at least two months after an uncomplicated acute myocardial infarction; of these, 90 underwent coronary angiography. All patients were followed-up for a mean of 32 +/- 13 months regarding the prediction of hard (death and reinfarction) and soft (angina and coronary surgery) coronary events. The specificity, sensitivity, positive and negative predictive value of exercise stress test were 47%, 76% and 41% for any coronary events; none of the patients who incurred a hard coronary event showed ischemia during electrocardiographic exercise tests. Sensitivity, specificity and positive predictive value for failure to increase the ejection fraction of at least 5% were 60%, 45% and 30% for any coronary event and 25%, 49% and 2% for any hard coronary event. The presence of multivessel disease at coronary angiography showed a sensitivity of 62% for any coronary event and of 67% for hard coronary events; specificities were 66% and 57%, and predictive values were 52% and 10%, respectively. It is concluded that electrocardiographic exercise testing, radionuclide angiography and coronary angiography are not helpful two months after an episode of uncomplicated myocardial infarction in order to identify patients who will suffer a new coronary event.

Adult↗
PubMed1992

Exercise-induced ST depression and ST/heart rate index to predict triple-vessel or left main coronary disease: a multicenter analysis.

The aim of this investigation was to determine the difference in accuracy between two frequently published noninvasive indicators of severity of coronary artery disease (exercise-induced ST segment depression and heart rate-adjusted ST depression [ST/HR index]). The study was designed as a survey of consecutive patients undergoing exercise electrocardiography and coronary angiography. There were a total of 2,270 patients without prior myocardial infarction or cardiac valvular disease referred for angiography from eight institutions in three countries; 401 of these patients had triple-vessel or left main coronary artery disease. The sensitivities of ST depression and ST/HR index in detecting triple-vessel or left main coronary artery disease were, respectively, 75% and 78% (p = 0.08) at cut point values where their specificities were equal (64%). This small increase in the accuracy of the ST/HR index was evident only at peak exercise heart rates below the median value of 132 beats/min, where the sensitivities of ST depression and ST/HR index were 73% and 76% (p = 0.03), respectively, at cut point values corresponding to a specificity of 60%. These results were consistent at all eight participating institutions. The increase in accuracy achieved by dividing exercise-induced ST depression by heart rate is small and confined exclusively to a low exercise heart rate. This lack of superiority cannot be generalized to all methods of heart rate adjustment.

Bias↗
PubMed1992

Preoperative evaluation in non-cardiac surgery: cardiac risk assessment.

Nine hundred and ninety patients, ages 20 years or older, undergoing non-cardiac elective surgery were prospectively studied to identify high cardiac risk preoperative factors in a case-mix population and to assess cardiological risk. The prevalence of major cardiac complications was 2.3%, including 0.8% mortality. Univariate analysis showed that: age; history of chest pain; dyspnea; hypertension; presence of systolic murmur and third sound; diastolic pressure greater than 95 mmHg; electrocardiogram left ventricular hypertrophy; cardiothoracic ratio greater than 0.5 and valvular calcifications are associated with cardiac complications (p = 0.001-0.02), with low sensitivity (range: 14-38%) and high specificity (range: 85-98%). Cardiological referral was required for 169 patients (17%) that showed a higher prevalence of cardiovascular diseases (85%) and of cardiac complications (5.3%). Cardiologists required further tests for 13 patients (7.7%) and modified therapy for 93 (55%). High cardiac risk patients are identified preoperatively in current practice and cardiological referral is frequent; further studies are mandatory to evaluate the most effective and efficacious procedures.

Adolescent↗
PubMed1991

A lesson from the controversy about heart rate adjustment of ST segment depression.

To summarize the literature review, the heart rate adjustment appears to be able to perfectly discriminate patients with different numbers of diseased coronary vessels in one center, to increase the diagnostic accuracy of three-vessel or left main disease in eight centers, and unable to improve accuracy in seven centers. To explain those differences, several methodological and statistical biases have been considered. However, a recent report regarding the application of the method in eight centers and a meticulous literature review could not explain the superior performance in some laboratories.

Coronary Disease↗
PubMed1991

[Heart rate adjustment of ST segment depression: a good idea, but what results?].

Since 1977, 30 original reports have been published regarding the heart rate adjustment of the ST segment depression. The aim of the investigators was to find a new criterion more sensitive and more specific than the conventional slope and depression of the ST segment. This is a well known index of ischaemia and it was expected to become more sensitive if adjusted with an index of oxygen demand (the heart rate). In order to have a historical perspective of the debate, all published reports on the ST segment heart rate adjustment were analyzed. The group of Leeds showed no overlap of values between patients without coronary artery disease and patients with one, two, and three vessel disease. The new method, called ST/HR slope, purported to predict the exact number of coronary arteries with critical stenoses. These results have never been duplicated in any other center with the same accuracy. Several authors determined the clinical usefulness of this method and obtained conflicting results. Even now a unanimous agreement has not been reached and the routine utilization of the method in exercise laboratories is still uncommon. From this controversy, it should be learned that a physiological rationale does not always correspond to a relevant clinical result. Only clinical practice can define the real value of a new instrument.

Coronary Disease↗
PubMed1989

Slaves of a test.

Explore the source record for details and available documents.

Research Design↗
PubMed1989

[Long-term variability in unsustained ventricular arrhythmias: pharmacologic and pro-arrhythmic effect].

A 72% reduction in the number of premature ventricular complexes, a 75 and 65% reduction in pairs and repetitive forms, respectively, are commonly accepted criteria for the evaluation of the efficacy of short-term antiarrhythmic treatment. On the other hand, a three-to-ten fold increase in the frequency of premature ventricular complexes is considered as a proarrhythmic effect. The aim of this paper is to verify if these criteria can still be applied on a long-term basis. Twenty-eight subjects without a demonstrable underlying organic heart disease and 21 patients with stable chronic ischaemic heart disease were studied. All patients showed more than 30 premature ventricular complexes per hour during ambulatory electrocardiogram monitoring. The spontaneous long term variability of ventricular arrhythmias was evaluated by comparing the first of three consecutive 24-hour ambulatory ECGs at the beginning of the study with a 24-hour ECG monitoring at the end of a 24-month follow-up period. According to the previous criteria about 50% of patients showed a spontaneous reduction in the number of premature ventricular complexes (greater than 72%) mimicking a therapeutic effect if any drug had been given. The increase in ventricular arrhythmias mimicked a proarrhythmic effect in almost 10% of patients. This trend is substantially the same both in subjects without organic heart disease and in patients with chronic coronary artery disease. The results of this study demonstrate that the initially established criteria used to judge the efficacy or the proarrhythmic effect of a given drug cannot be relied upon on a long-term basis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Does post myocardial infarction rehabilitation prolong survival? A meta-analytic survey.

Cardiac rehabilitation undoubtedly helps post-myocardial infarction patients to feel better; however, it is under consideration whether or not it also prolongs their survival. Since 1972 several published studies have examined the role of physical rehabilitation in relation to patient survival after myocardial infarction. Eight randomized controlled trials were reviewed in order to compare the rate of events (total death, cardiac death, recurrence of non-fatal myocardial infarction) in the trained and untrained patient population. A tendency toward a positive training effect on survival was present in almost all trials; however, in only one study was the number of cardiac deaths shown to be significantly reduced in trained patients. The aim of this study was to use a quantitative analysis based on estimates of individual trials to evaluate the effect of post-myocardial infarction rehabilitation programs on survival. The analysis of pooled data revealed a significant decrease in total mortality (relative risk 0.68 with 95% confidence limits 0.53-0.86; p = 0.002), and cardiac mortality (relative risk 0.62 with 95% confidence limits 0.48-0.82; p less than 0.001). However, there was a non-significant increase in recurrences (relative risk 1.12 with 95% confidence limits 0.84-1.49; p = 0.45). These data are very similar to those found by another meta-analytic survey performed on a different set of published studies, i.e., odds risk for total death 0.76, for cardiac mortality 0.75 and for non-fatal myocardial infarction 1.15.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Comparison between Doppler CW and Duplex-Scanning in the assessment of silent peripheral vascular lesions in a population of ischemic heart disease patients].

A recent ultrasound technique, Duplex Scanning (D-S), endowed with significant sensitivity, specificity and accuracy has been used to screen atherosclerotic disease in subjects at risk. Within the context of a transverse investigation aimed at identifying the multi-district nature of atherosclerotic plaques, the sensitivity and specificity values and the concordance index of Doppler C.W. (D-CW) have been checked using the D-S in carotid districts as a reference test in 205 patients suffering from ischaemic cardiopathy, asymptomatic for carotid vasculopathy, aged between 45 and 55. 170 patients had the D-CW and the D-S in 340 carotid vessels. D-CW revealed atherosclerotic changes in 122 carotids (prevalence 36%) while the D-S in 119 districts (prevalence 35%) revealed plaques greater than simple thickening, of which 89 (26%) with stenosis less than 30% and 30 (9%) with stenosis greater than 30%. Of the latter, 25 were greater than 60% and 5 less than 60%: one of them provoked a stenosis greater than 75%, the limit beyond which the change becomes haemodynamically significant. D-CW showed 46% sensitivity, a specificity of 70% and a concordance percentage of 59% with respect to D-S. D-CW sensitivity proved apparently low as did the concordance percentage between C-CW and D-S. However, considering that the lesions encountered were prevalently all haemodynamically non-significant, these values may become acceptable.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Disease↗