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Biomedical subjects

L T Sheffield

Publications and source records attributed to L T Sheffield.

At least 37 records · Page 2Linked to original sources
PubMed1986

Predictive value of the exercise tolerance test for mortality in North American men: the Lipid Research Clinics Mortality Follow-up Study.

More than 3600 white men, from 30 to 79 years old and without a history of myocardial infarction, underwent submaximal treadmill exercise tolerance tests as part of their baseline evaluation for the Lipid Research Clinics Mortality Follow-up Study. The exercise test was conducted according to a common protocol and coded centrally; depression of the ST segment by at least 1 mm (visual coding) and/or 10 microV-sec (ST integral, computer coding) signified a positive test. Concurrent measurements of age, blood pressure, history of cigarette smoking, and plasma levels of lipids, lipoproteins, and glucose, as well as other coronary risk factors, were obtained. Cumulative mortality from cardiovascular disease was 11.9% (22/185) over 8.1 years mean follow-up among men with a positive exercise test vs 1.2% (36/2993) over 8.6 years mean follow-up among men with a negative test. Three-quarters (43) of these deaths were due to coronary heart disease. The relative risk for cardiovascular mortality associated with a positive exercise test was 9.3 before and 4.6 after age adjustment. Cardiovascular mortality rates were especially elevated (relative risk 15.6 before and 5.1 after age adjustment) among the 82 men whose exercise tests were adjusted "strongly" positive based on degree and timing of the ischemic electrocardiographic response. A positive exercise test was also moderately associated with noncardiovascular mortality; the relative risk for all-cause mortality was 7.2 before and 3.4 after age adjustment. The relative risk for cardiovascular mortality associated with a positive exercise test was not appreciably altered by covariance adjustment for known coronary risk factors other than age. A positive exercise test was a stronger predictor of cardiovascular death than were high plasma levels of low-density lipoprotein cholesterol, low plasma levels of high-density lipoprotein cholesterol, smoking, hyperglycemia, or hypertension. Its impact on risk of cardiovascular death was equivalent to that of a 17.4 year increment in age.

Adult↗
PubMed1986

Dyslipoproteinemias and manifestations of coronary heart disease. The Lipid Research Clinics Program Prevalence Study.

The Lipid Research Clinics Prevalence Study population underwent a noninvasive evaluation to assess the odds of coronary heart disease (CHD) among individuals with various types of dyslipoproteinemia (DLP) relative to the odds for individuals free of DLP in a nonselected population. The noninvasive evaluation included the Rose questionnaire for angina, a resting electrocardiogram, and a graded treadmill exercise test. The presence of manifestations of CHD was assessed by a combination of these findings. Multiple linear regression and multiple logistic regression analyses were used to evaluate associations between CHD and DLP, with adjustments for the following covariates: age, body mass, systolic blood pressure, alcohol consumption, and cigarette use. There were no consistent associations in women or in men 30 to 49 years old. In men 50 to 69 years old, the mean high-density lipoprotein cholesterol (HDL-C) values and HDL-C/cholesterol ratio were significantly lower in the definite CHD and angina categories, compared with the negative (no evidence of CHD) group. Higher odds ratios for CHD were present in those classified as having type IIa, type IV, and hypoHDL DLPs, relative to those classified as normal by the phenotyping algorithm. These associations were consistent across the several categories of CHD manifestations, but did not reach statistical significance after adjustment for multiple testing. A statistically significant lower odds ratio for CHD was observed in men 50 to 69 classified as having hyperHDL when compared with those without DLPs. The associations between CHD and the various forms of DLP were consistent with those observed between CHD and the plasma lipid and lipoprotein-cholesterol concentrations. The Lipid Research Clinics Prevalence Study confirmed the relationship between elevated low-density lipoprotein cholesterol, decreased HDL-C, and noninvasively determined CHD in a free-living asymptomatic population of older men.

Adult↗
PubMed1985

Exercise testing in the Coronary Artery Surgery Study randomized population.

Exercise electrocardiographic stress testing was performed in 81% of the 780 patients randomized in the Coronary Artery Surgery Study at entry. The cumulative survival at the end of 7 year follow-up was 90% for those assigned to surgical treatment and 88% for those assigned to medical therapy (p = NS). These survival rates did not differ significantly from either those of the entire randomized cohort or those of the 149 patients who did not have a qualifying exercise test at baseline. No differences in important baseline characteristics existed between those who were exercised and not exercised at entry. Stratification of patients according to the degree of ST segment depression (less than 1 mm, greater than or equal to 1 mm, greater than 2 mm) and final exercise stage achieved during a Bruce protocol treadmill test (final stage less than or equal to 1, stage 2 and greater than or equal to stage 3) failed to show any significant differences in 7 year survival rates between medically and surgically assigned patients. Additionally no differences in survival were noted within either the medical or surgical groups regardless of the degree of ST segment depression or the final stage achieved. The presence of exercise-induced angina, however, identified patients who had a survival advantage if assigned to surgical therapy, with a 7 year survival rate of 94% compared with 87% for medically assigned patients (p = .007).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Prognostic importance of a clinical profile and exercise test in medically treated patients with coronary artery disease.

To identify predictors of mortality in medically treated patients with symptomatic coronary artery disease, 30 variables were analyzed in 4,083 patients. Regression analysis demonstrated that seven variables were independent predictors of survival. A high risk subgroup (annual mortality rate above 5%) was identified, consisting of patients with either a congestive heart failure score of 3 to 4 or 1 mm or greater ST segment depression and final exercise stage of 1 or less. When all 30 variables were analyzed conjointly, the left ventricular contraction pattern (p less than 0.0001) and the number of diseased coronary vessels (p less than 0.003) proved to be the most important predictors of survival. In a subgroup of 572 patients with three vessel coronary disease and preserved left ventricular function, the probability of survival at 4 years ranged from 53% for patients only able to achieve stage 1/2 of exercise to 100% for patients able to exercise into stage 5 (p less than 0.004). Thus, in patients with defined coronary pathoanatomy, clinical and exercise variables primarily relating to the functional state of the left ventricle are helpful in assessing prognosis.

Adult↗
PubMed1984

The value of preoperative exercise testing in predicting long-term survival in patients undergoing aortocoronary bypass surgery.

To determine whether preoperative exercise testing adds important independent prognostic information in patients undergoing coronary bypass surgery, 35 variables were analyzed in 1241 patients enrolled in the Coronary Artery Surgery Study registry. All patients underwent a treadmill exercise test before bypass surgery and were followed for up to 7 years. Survival in this surgical cohort was 90.6% (1124 of 1241). Multivariate stepwise dicriminant analysis identified the left ventricular score and the final exercise stage achieved as the two most important (p less than .001) independent predictors of postoperative survival. In a subgroup of 416 patients with three-vessel coronary disease and preserved left ventricular function, the probability of postoperative survival at 7 years ranged from 95% for those patients able to exercise to stage 4 to 83% for those whose ability was limited to stage 1 of exercise. Thus, the preoperative exercise test, by assessing the functional capacity of the cardiovascular system, is an important independent predictor of postoperative survival.

Coronary Angiography↗
PubMed1983

Enhanced evaluation of treadmill tests by means of scoring based on multivariate analysis and its clinical application: a study of 608 patients.

Six hundred eight patients being evaluated for chest pain who did not have valvular disease, cardiomyopathy, left ventricular hypertrophy or bundle branch block, and were not receiving digitalis, had treadmill tests and coronary angiograms. In 351, various exercise variables were correlated by multivariate analysis to coronary artery disease (CAD). In men, significant variables were: (1) maximal heart rate achieved less than 80% of maximal predicted heart rate (Mx PHR), (2) ST-T change greater than or equal to 1 mm, (3) age greater than or equal to 55 years and (4) treadmill time (TT) less than 8 minutes. These variables rated diagnostic scores of 9, 6, 5, and 3, respectively. A score of greater than or equal to 7 was considered diagnostic of CAD. In a test group of 192 men in which ST-T change was compared with treadmill score, sensitivity was 65 versus 85%, specificity 79 versus 74% and accuracy 69 versus 83%. In women, maximal heart rate less than 90% of Mx PHR and TT of less than 6 minutes were significant, with an accuracy of 75%. Moreover, 89% of incomplete tests and 70% of tests in patients with previous myocardial infarction were also correctly diagnosed. This method allows convenient use of significant exercise variables for clinical purposes with improved results.

Adult↗
PubMed1983

A quantitative relationship of electrocardiographic criteria of left ventricular hypertrophy with echocardiographic left ventricular mass: a multivariate approach.

The purpose of this study was to evaluate the sensitivity of various electrocardiographic (EKG) criteria of left ventricular hypertrophy (LVH) in relation to echocardiographic left ventricular mass (LVME) and to assess the relative strength of various EKG variables used in the diagnosis of LVH by multivariate analysis. An attempt was also made to determine if a new combination of precordial and T-wave voltage could improve the sensitivity of EKG. In 89 patients, M-mode echocardiograms and standard EKGs were studied. Correlation of Romhilt-Estes point-score system with LVME was r = 0.621, sensitivity and specificity was 57 and 81%, respectively. Other voltage criteria had lower sensitivity. Various combinations of precordial and T-wave voltage were not superior. The quantitative relationship of individual EKG variable, QRS duration, S V1-3, R V4-6, strain T wave, left atrial abnormality, intrinsicoid deflection and axis, with LVM was, r = 0.661, 0.595, 0.429, 0.42, 0.347, and 0.225, respectively. By multivariate analysis, QRS duration, S V1-3, T-wave and R V4-6 voltage had F-value (relative strength) of 27.95, 27.15, 22.02, and 4.03, respectively, other variables were statistically insignificant. In conclusion, the most important EKG variables predictive of LVH are QRS duration, S V1-3, strain T-wave and lateral voltage in decreasing value. Rescoring these variables in accordance to their correlation to LVM may improve EKG sensitivity for the diagnosis of LVH.

Cardiomegaly↗
PubMed1983

Use of survival analysis to determine the clinical significance of new Q waves after coronary bypass surgery.

There are few data on the long-term effects of new Q waves on survival and morbidity after coronary bypass graft surgery (CABG). We followed 1340 patients who underwent CABG in 1978 at 10 hospitals participating in the Coronary Artery Surgery Study (CASS). The incidence of perioperative Q-wave infarction was 4.76% (range 0.0-10.3% by hospital). The rate of infarction was higher in patients who had an increased left ventricular end-diastolic pressure or cardiomegaly on the preoperative chest radiograph. Patients who received more grafts or who had longer cardiopulmonary bypass time were also at higher risk of infarction. In a stepwise discriminant analysis of 44 clinical, angiographic and surgical variables, cardiopulmonary bypass time, topical cardiac hypothermia and cardiomegaly entered the stepwise selection of variables. Long-term survival was adversely affected by the appearance of new postoperative Q waves. The hospital mortality was 9.7% in the 62 patients who had new postoperative Q waves and 1.0% in the 1278 patients who did not (p less than 0.001); the 3-year cumulative survival rates were 85% and 95%, respectively (p less than 0.001). In patients who survived to hospital discharge, the presence of new postoperative Q waves did not adversely affect 3-year survival (94% and 96%, respectively). The survival rates were worse in patients who had a history of infarction or who had impaired left ventricular function preoperatively. The number of readmissions to hospital after CABG among the patients who had a transmural perioperative infarction was similar to to that among patients who did not. We conclude that the appearance of new Q waves after CABG adversely affects survival. The major impact on mortality occurs before hospital discharge. Patients who are destined to have a perioperative infarct cannot be predicted from commonly measured preoperative and angiographic variables.

Adult↗
PubMed1981

Limited exercise testing soon after myocardial infarction. Correlation with early coronary and left ventricular angiography.

Forty-eight patients within 3 weeks of myocardial infarction underwent both limited treadmill graded exercise testing and coronary and left ventricular angiography. Nineteen (90%) of 21 patients with positive exercise tests (greater than or equal to 1 mm ST depression, angina, or both) had multivessel coronary artery disease. In the 27 patients with negative exercise test results, 15 (55%) had multivessel disease, 11 (41%) had single-vessel disease, and one (4%) had no coronary stenosis. Exercise-induced ST segment elevation occurred in 24 patients and predicted a significantly lower ejection fraction and higher angiographic abnormally contracting segment size. Patients experiencing angina during or after exercise had a significantly shorter 2-year survival (54% +/- 21%) than patients without exercise-induced angina (97% +/- 3%) (p less than 0.03). Thus limited exercise testing postinfarction is useful in evaluating the presence of multivessel coronary artery disease and left ventricular dysfunction and predicting long-term survival.

Adult↗