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Biomedical subjects

L T Sheffield

Publications and source records attributed to L T Sheffield.

At least 19 recordsLinked to original sources
PubMed1991

Significance of silent myocardial ischemia during exercise testing in patients with diabetes mellitus: a report from the Coronary Artery Surgery Study (CASS) Registry.

To evaluate the significance of ischemic ST depression without anginal chest pain during exercise testing among patients with diabetes mellitus, the data on 45 such patients from the Coronary Artery Surgery Study registry were analyzed. These patients (group 1, silent ischemia) were compared with 37 diabetic patients with both ischemic ST depression and chest pain (group 2, symptomatic ischemia), with 31 diabetic patients without ischemic ST depression or chest pain (group 3, no ischemia), and with 429 patients without diabetes who had silent ischemia during exercise testing. All patients had documented coronary artery disease (CAD) (greater than 70% diameter narrowing). The 6-year survival among patients with silent ischemia was worse in diabetic than nondiabetic patients (59 vs 82%, respectively, p less than 0.001). By contrast, the 6-year survival among patients without ischemia was similar among diabetic and nondiabetic patients (93 vs 85%, respectively, p = 0.476). Among diabetic patients, survival at 6 years with medical treatment was 59% for group 1, 66% for group 2 and 93% for group 3 (p = 0.008). Survival among subsets of patients with diabetes and silent ischemia (group 1) based on the extent of CAD and left ventricular function ranged from 100 to 32% (p = 0.093). The survival of the 45 patients with diabetes mellitus and silent ischemia (group 1) treated medically was compared with that of 28 patients receiving coronary artery graft bypass surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Bypass↗
PubMed1991

Prevalence and prognostic significance of silent and symptomatic ischemia after coronary bypass surgery: a report from the Coronary Artery Surgery Study (CASS) randomized population.

The prevalence and prognostic significance of postoperative myocardial ischemia, as detected by exercise testing, were prospectively assessed in 174 patients from the Coronary Artery Surgery Study (CASS) randomized surgical population who had exercise testing before and 6 months after coronary artery bypass graft surgery. Whereas the prevalence of symptomatic ischemia significantly decreased postoperatively (52% vs. 6%, p less than 0.001), the frequency of silent myocardial ischemia did not change (30% vs. 29%). Survival at 12 years after bypass surgery based on the 6-month postoperative exercise test results was significantly better for the 112 patients with no ischemia (80%) than for the 51 patients with silent ischemia (68%) or the 11 patients with symptomatic ischemia (45%). These data show that coronary artery bypass graft surgery diminishes the overall prevalence of symptomatic but not silent ischemia and that both silent and symptomatic ischemia adversely affect the postoperative prognosis of these patients.

Coronary Artery Bypass↗
PubMed1990

Ten-year follow-up of quality of life in patients randomized to receive medical therapy or coronary artery bypass graft surgery. The Coronary Artery Surgery Study (CASS)

Quality of life indexes were assessed in 780 patients 10 years after randomization to medical therapy (n = 390) or coronary artery bypass graft surgery (n = 390) in the Coronary Artery Surgery Study. At 10 years, mortality was 21.8% in the medical group and 19.2% in the surgical group (p = NS), and 144 (37%) of the medical group had undergone surgery because of increasing chest pain. At study entry, 22% of medical and surgical patients were angina free; at 1 and 5 years after entry, the frequency of asymptomatic patients was 66% and 63% in the surgical group and 30% and 38% in the medical group. However, by 10 years after entry, the proportion of patients free of angina had fallen to 47% in the surgical group and to 42% in the medical group. Activity limitation and use of beta-blockers and long-acting nitrates were less in the surgical than the medical group at 1 and 5 years after entry but little different from the medical group at 10 years after entry. Throughout follow-up, recreational status, employment status, frequency of heart failure, use of other medications, and hospitalization frequency were similar between the two groups. Thus, indexes of quality of life such as angina relief, increased activity, and reduction in use of antianginal medications initially appear superior in patients with stable manifestations of ischemic heart disease assigned to surgery, but by 10 years after entry, these advantages are much less apparent. Although the observed similarities of the medically and surgically assigned groups at 10 years reflect return of symptoms in the surgical group to some extent, a more important explanation is the performance of late surgery in a large proportion of the medically assigned patients, rendering them asymptomatic.

Activities of Daily Living↗
PubMed1979

Interventricular septal thickness and left ventricular hypertrophy. An echocardiographic study.

Septal and left ventricular posterior wall (LVPW) thicknesses and their ratios were studied at the left ventricular outflow tract and left ventricular cavity in 66 patients with echocardiographically diagnosed left ventricular concentric hypertrophy, 20 with idiopathic hypertrophic subaortic stenosis (IHSS), and 34 normal subjects. Concentric hypertrophy was due to hypertension in 41 subjects and to valvular disease in 15 subjects. Septal thickness in normal subjects was related to body surface area (p less than 0.02). In 12% of normal subjects, 39% of patients with concentric hypertrophy and 95% with IHSS, the septal/LVPW ratio was greater than or equal to 1.3. Thirty-two percent of patients with hypertension, 78% with aortic stenosis, and 60% with aortic insufficiency had septal/LVPW ratios greater than or equal to 1.3 at left ventricular midcavity level. In conclusion, a septal/LVPW thickness ratio of greater than or equal to 1.3 is common in patients with concentric left ventricular hypertrophy and may also occur in normal subjects. A ratio greater than or equal to 1.5 may be more specific for genetically determined asymmetric septal hypertrophy.

Adult↗
PubMed1979

The echocardiogram after pericardiectomy.

Many factors may affect the interventricular septal motion. This study measures the effect of pericardiectomy on septal motion in 9 patients who were evaluated 1 week to 58 months after pericardiectomy. Echocardiography was performed with the patient in recumbent position with the special care to record motion of the muscular septum and not that of the aorta. No patient had left bundle branch block, angina, myocardial infarction, pericardial effusion or right ventricular volume overload. Septal motion was paradoxical in 7, normal in 1 and could not be evaluated 1 patient. The mean value of the right ventricular internal dimension was normal. Two of 9 patients had technically satisfactory echocardiograms preoperatively. Septal motion was normal in both, and both developed paradoxical septal motion postoperatively. We conclude that paradoxical septal motion pericardiectomy, but in contrast with other causes of this finding right ventricular internal dimension remains normal.

Adult↗
PubMed1978

A quantitative technical quality assay method for electrocardiograms.

A method is presented for quantitative assessment of ECG technical quality to permit sensitive detection of performance trends of individual technicians or entire ECG laboratories. The common flaws in ECG recording technic are those which introduce ultra-low frequency artifact or baseline shift, powerline artifact, myographic and intermediate frequency artifact, clipping of waveforms, disconnection or reversal of electrodes and general faults of protocol adherence. Procedures for quantitating these attributes are presented and explained in order to arrive at a mean figure of merit for each ECG recording. Use of such a method can aid ECG technicians' understanding of the important features of tracing quality and provide an objective basis for the recognition of outstanding performance, on one hand, or the need for remedial training, on the other.

Electrocardiography↗
PubMed1978

A controlled study of a new ECG electrode system.

A newly marketed resting ECG electrode system was compared with conventional metal suction and plate electrodes, electrode cream and patient cable. Two experienced technicians were given special training in the use of the new electrode, electrolyte and patient cable system and alternated daily in using new and conventional equipment. Nearly equal numbers of perfect-scoring ECGs were recorded with each system, attesting to the impartiality of the technicians. A total of 1,062 ECGs were evaluated, 554 with the new system and 508 with the conventional one. ECG tracings were evaluated by electrocardiographers unaware of which system was used for each. A quantitative scoring system was used to measure the technical quality of each tracing in terms of baseline drift, powerline artifact and myographic plus miscellaneous artifacts. The new system received mean scores of 2.33, 3.08, and 2.72, respectively, while the conventional electrodes received scores of 2.56, 3.03 and 2.79. We concluded that the two types of electrodes produced ECGs of essentially equal quality.

Electrocardiography↗
PubMed1978

Interesting approaches to the diagnosis of angina pectoris.

Twelve different approaches to laboratory diagnosis of angina pectoris are reviewed here. They employ no fewer than seven different means of intentionally provoking a disparity between myocardial requirement and supply: dynamic exercise, hypoxia, prandial stress, raised systemic vascular resistance, paced tachycardia, mental stress, and exposure to normal environment. Of these, only dynamic exercise and the diverse combinations of stresses in the normal environment are capable of altering the heart's oxygen requirement-supply ratio threefold or more, accounting for the successful results from tests using these means of stress. The reviewed tests use three different means of detecting myocardial ischemia provoked by stress: electrocardiography to indicate impaired ventricular repolarization, indirect graphic records sensitive to impairment of mechanical ventricular function, and detection of insufficient myocardial perfusion patterns by radioactive tracer. The latter approach is particularly appealing because it directly reflects the pathophysiologic anomaly of interest. It should be remembered, however, that the basic differences in these methods of detecting ischemia make them complementary to each other and encourage their use in combination for improved diagnostic sensitivity.

Angina Pectoris↗
PubMed1978

Maximal heart rate and treadmill performance of healthy women in relation to age.

Maximal treadmill exercise heart rate, work capacity and electrocardiographic response were studied in 95 asymptomatic, predominantly sedentary women between the ages of 19 and 69 years. Average maximal heart rate (MHR) was found inversely related to age, such that MHR = 216 -0.88 (years of age) +/- 10 beats/min (X +/- 1 SD). Treadmill exercise endurance was 7.64 min +/- 1.99. The reduction of treadmill endurance with advancing age was not statistically significant. Asymptomatic ST-segment depression occurred in 6% of subjects. In 5% the ST segment sloped upward, and in 1% it was flat. Mean age of women with ST depression was 52 years, compared with 39 years mean age of all subjects. Premature beats during exercise were found in 20 of 95 subjects, and were not related to age. Graded exercise testing of women employing target heart rates should use heart rate tablets developed especially for women. These tables do not require correction for athletically trained for sedentary life-style.

Adult↗
PubMed1976

Stress testing with ST-segment depression at rest. An angiographic correlation.

Near maximal graded exercise tests and coronary angiograms were compared in 37 patients with a history of chest pain and with ST segment depression at rest, who were free of obvious nonischemic causes of ST depression. Additional ST depression of 0.1 mV or more occurred with exercise in 26 patients and 23 of these had obstruction of one or more coronary arteries (sensitivity = 0.92). Eleven patients showed no additional ST-segment depression with exercise, and nine of these had normal coronary angiograms (specificity = 0.75). Patients with no increase in ST depression on exercise developed the highest heart rates; those with asymptomatic additional ST depression achieved intermediate rates; and those with anginal attacks during testing demonstrated the least heart rate acceleration. Those with less coronary obstruction exercised longer on the treadmill than those with more obstruction. Those showing added ST depression were predominantly men (18 of 26) and were older (mean 54 years) than those who did not (mean 44 years). No test complications were encountered. This study suggests that safe and effective stress testing may be accomplished not only in persons with normal resting ECGs but also in selected patients who have abnormal ST segments at rest.

Adult↗
PubMed1975

Ischemic myocardial injury following aorto-coronary bypass surgery.

To assess the incidence of acute myocardial injury following aorto-coronary bypass surgery 151 patients (136 men and 15 women) were evaluated by studying serial preoperative and postoperative ECGs and SGOT, LDH and CPK levels. The mean age of men was 49.1 and of women, 53.1 years. Following surgery 15 patients (group I, 9.9 percent) developed new myocardial infarction as judged by Q wave criteria, 33 patients (group II, 22.5 percent) developed significant ST-T changes, and 103 patients (group III, 68 percent) had no significant ECG change. Mean postoperative SGOT values were: group I,126.2; group II, 100.6; and group III, 72.8. Only the difference in SGOT values between group I and III was significant (P less than 0.01). There was no correlation between type and site of surgery and the incidence of myocardial infarction. There were five deaths (3.3 percent). The combination of death and diagnosed myocardial infarction amounted to 12.6 percent of patients for this widely used elective procedure.

Adult↗
PubMed1975

Paradoxical septal motion in a patient with pulmonic stenosis.

This case will demonstrate abnormal (paradoxical) septal motion in a 31-year-old woman with an isolated pulmonary valvular stenosis. The right ventricular volume overload was exluded by the shunt series, special angiographic studies and at surgery. The echocardiographic abnormality persisted during a restudy three months after surgery.

Adult↗