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Biomedical subjects

D S Sheps

Publications and source records attributed to D S Sheps.

70 records · Page 4Linked to original sources
PubMed1979

Effect of a physical conditioning program upon left ventricular ejection fractions determined serially by a noninvasive technique.

6 clinically normal subjects underwent a 3-month physical conditioning program with the ejection fractions determined before and after physical conditioning using a scintillation probe. All subjects achieved a conditioning effect as evidenced by increased treadmill test duration after conditioning (mean duration before conditioning: 658 vs. 715 sec after conditioning; p less than 0.02). All 6 subjects increased resting ejection fractions after conditioning (mean ejection fraction before conditioning: 54.5 +/- 5.4%; mean ejection fraction after conditioning: 67.0 +/- 9.0%; p less than 0.01). Thus, an aerobic physical conditioning program appears to increase resting ejection fractions in normal subjects.

Adult↗
PubMed1979

Antiarrhythmic drug therapy in survivors of prehospital cardiac arrest: comparison of effects on chronic ventricular arrhythmias and recurrent cardiac arrest.

We studied the long-term effects of membrane-active antiarrhythmic agents on chronic ventricular arrhythmias in patients who have survived prehospital cardiac arrest. Among 16 patients treated with a dose-adjusted, plasma level-monitored antiarrhythmic regimen, eight have survived for longer than 12 months and eight have had recurrent cardiac arrests (RCAs). Monthly Holter monitor tapes (HM) recorded during the 4 months before the eight RCAs were compared with monthly HM tapes matched for time of entry and duration of follow-up in the eight patients who did not have RCAs. Transient or persistent complex ventricular ectopic depolarizations (VEDs) have been recorded on 47 of the 63 monthly HM tapes (75%). The difference between VEDs in the RCA patients (mean 153 VEDs/hr, median 19 VEDs/hr) and VEDs in the patients who have not had RCA (mean 122 VEDs/hr, median 8 VEDs/hr) was not significant (p less than 0.2); nor was there a predictable relationship between therapeutic plasma levels of antiarrhythmic agents and the frequency and complexity of chronic asymptomatic VEDs (therapeutic levels--mean 104 VEDs/hr, median 6 VEDs/hr; subtherapeutic levels--mean 184 VEDs/hr, median 21 VEDs/hr). Differences were not significant (p greater than 0.1). In contrast, all eight RCA patients had unstable plasma levels (21 of 31 determinations subtherapeutic) while six of the eight patients who have not had RCA had consistently therapeutic levels (p less than 0.01). Thus, adequate plasma levels of antiarrhythmic agents may protect against RCA, despite failure to suppress VEDs predictably. The apparent dissociation between predictable suppression of chronic VEDs and protection against RCA suggests that clinical effectiveness of these agents may not be best measured by their effect on chronic VEDs.

Adult↗
PubMed1977

Altered hemoglobin-oxygen affinity with long-term propranolol therapy in patients with coronary artery disease.

Pharmacologic agents that alter hemoglobin affinity for oxygen may affect systemic or myocardial oxygen delivery. In vitro, and in normal man propranolol shifts the oxyhemoglobin equilibrium curve to the right, thus increasing the partial pressure of oxygen at which hemoglobin is 50% saturated (P50) and enhancing oxygen delivery. The effect of propranolol on hemoglobin P50 was evaluated in 12 patients with angina pectoris and documented coronary artery disease. Determinations were made during oral propranolol therapy (mean daily dose 152 mg) of at least 3 months' duration and after administration of propranolol had been discontinued for at least 4 days. Hemoglobin P50 and erythrocyte 2,3-diphosphoglycerate (DPG) were measured. Data in 12 patients were: the mean P50 after discontinuation of propranolol was 28.2 mm Hg+/-0.9 (standard error of the mean) and during propranolol therapy 31.7+/-0.7; P less than 0.001; red blood cell 2,3-DPG did not change to explain the increase in P50. This demonstrated shift could increase systemic oxygen delivery and thus benefit marginally perfused myocardium while sparing coronary flow. Propranolol, in addition to its negative chronotropic and inotropic effects, may increase tissue oxygen delivery in patients with the anginal syndrome.

Coronary Disease↗
PubMed1977

Decreased frequency of exercise-induced ventricular ectopic activity in the second of two consecutive treadmill tests.

Two exercise tests were performed with an intervening rest period of 45 minutes in a group of 13 subjects with previously identified exercise-induced ventricular arrhythmias and no resting arrhythmias. Both normal subjects and patients with heart disease were included in the group. The level of stresss was equal in both tests as judged by similar rate-pressure products at peak exercise. There was a significant decrease (P less than 0.05) in the number of VPCs induced by exercise during and after the second test. When the number of VPCs on test I and test II in the same patients were compared, a regression line fitted the data well (r = 0.92). Analysis of the recovery periods revealed significant (P less than 0.01) decreases in systolic blood pressure at one and three minutes post exercise, comparing the second to the first test. The underlying mechanism may be decreased myocardial oxygen demand during the second test as the lowered rate-pressure products during recovery (P less than 0.01) reflect. The results of this study indicate that tests of effectiveness of an antiarrhythmic drug should not be based solely on a decrease in the amount of severity of ventricular irritability between two successive exercise tests, one immediately before and the other following administration of the drug.

Adult↗
PubMed1977

Primary ventricular fibrillation. Some unusual features.

A 47-year-old man experienced ventricular fibrillation three times during a 3 1/2-year period. Each episode was preceded by an auditory aura, and no ventricular irritability was identified between episodes. The results of coronary arteriographic, hemodynamic, and intracardiac electrophysiologic studies were all normal. Hypokalemia and abnormal oxyhemoglobin dissociation were present. The possible relationships of these unusual features to the patient's disturbances in rhythm are discussed.

Diphosphoglyceric Acids↗
PubMedDate not supplied

Lack of effect of low levels of carboxyhemoglobin on cardiovascular function in patients with ischemic heart disease.

We studied 30 patients 38-75 yr of age who had ischemic heart disease to assess the effect of acute elevation of carboxyhemoglobin (COHb) concentration. Patients were nonsmokers with ischemia defined by exercise-induced ST depression (ST decreases)--25/30, angina--23/30, or abnormal ejection fraction (EF) response--18/30. After an initial familiarization and exercise session patients were exposed to air (carboxyhemoglobin [COHb] = 1.5 +/- 0.05%) and to carbon monoxide (CO) (100 ppm-COHb-average = 3.8 +/- 0.1%) on successive days in a double blind, randomized fashion. There was no significant difference in time to onset of angina (air = 312 sec, CO = 306 sec), maximal exercise time (air = 711 sec, CO = 702 sec), maximal ST decreases (1.5 mm for both), or time to significant ST decreases (air = 474 sec, CO = 475 sec). Double product at ST decreases and maximal double products were similar for both conditions. Resting ejection fraction was slightly but nonsignificantly higher after CO exposure (air = 53.9%, CO = 55.2%). Maximal ejection fraction was similar for both conditions (air = 57.4%, CO = 57.1%). Change in ejection fraction was slightly lower for CO exposure (air = 3.5%, CO = 2%), p = .049. In conclusion, there is no clinically significant effect of 3.8% COHb (representing a 2.2% increase from resting values) on the cardiovascular system in this study.

Administration, Inhalation↗
PubMedDate not supplied

Effects of low-level carbon monoxide exposure on resting and exercise-induced ventricular arrhythmias in patients with coronary artery disease and no baseline ectopy.

The effects of acute elevation of carboxyhemoglobin (COHb) concentrations on resting and exercise-induced ventricular arrhythmias were evaluated in 10 patients who had ischemic heart disease and in whom no ectopy during baseline monitoring was noted. After an initial training session, patients were exposed to air, 100 ppm carbon monoxide (CO), or 200 ppm CO on successive days in a randomized, double-blind, cross-over fashion. After exposure to 100 and 200 ppm CO, venous COHb levels averaged 4% and 6%, respectively. Symptom-limited supine exercise was performed after exposure. Eight of the 10 patients had evidence of exercise-induced ischemia--either angina, 1.0 mm ST depression, or abnormal ejection fraction response--during 1 or more exposure days. Ambulatory electrocardiograms were obtained on each day and analyzed for arrhythmia frequency and severity. On air and CO exposure days, each patient had only 0-1 ventricular premature beat/h in the 2 h prior to exposure, during the exposure period, during the subsequent exercise test, and in the 5 h following exercise. In conclusion, low-level CO exposure is not arrhythmogenic in patients with coronary artery disease and no ventricular ectopy at baseline.

Aged↗
PubMedDate not supplied

Depression and type A behavior pattern in patients with coronary artery disease: relationships to painful versus silent myocardial ischemia and beta-endorphin responses during exercise.

A sample of 45 patients with a history of coronary heart disease and documented myocardial ischemia during exercise testing were evaluated in an investigation of the possible relationships between psychological factors (depression and Type A behavior pattern), plasma beta-endorphin response and pain experience during maximal exercise-induced ischemia. Depression was assessed using the MMPI-D subscale, while Type A was evaluated using the Structured Interview. All patients developed ischemia during exercise as defined by ST-segment depression; however, only 18 patients reported anginal pain. Patients with high depression scores (MMPI-D greater than or equal to 70; n = 13) showed lesser increases in plasma beta-endorphin levels, tended more often to report anginal pain and rated pain as more severe during exercise than patients with low depression scores (MMPI-D less than 60; n = 18). Hemodynamic responses and severity of ischemia (assessed by ejection fraction changes and wall-motion abnormalities) did not differ between depression groups. Even after adjustment for group differences in exercise duration, depression was significantly associated with a lesser beta-endorphin response in the sample as a whole and, among patients reporting angina, with earlier pain onset and greater pain duration and severity. In contrast, when Type A versus B/X subgroups were compared, no differences in pain experience, beta-endorphin response or measures of ischemia were obtained. These findings suggest that in patients with ischemic heart disease, there may be a relationship between depression and anginal pain which may in part involve a blunted or absent beta-endorphin response.

Aged↗
PubMedDate not supplied

Heart rate variability in patients with coronary artery disease: differences in patients with higher and lower depression scores.

OBJECTIVE: This study tested the hypothesis that coronary artery disease patients with higher depression scores have lower heart rate variability during daily life. METHOD: Thirty-three men and nine women, ranging in age from 46 to 79, with coronary artery disease and exercise-induced ischemia were studied. The standard deviation of normal R-R intervals (SDNN) and average heart rate were obtained from 24-hour ambulatory electrocardiographic monitoring. Patients were grouped by a median split of the Minnesota Multiphasic Personality Inventory (MMPI-D) score. RESULTS: SDNN was lower (p = .009) and average heart rate was higher (p = .003) in patients with higher depression scores. These relationships remained substantially unaltered after statistically adjusting for the only demographic/clinical factor that varied between the groups: gender. CONCLUSIONS: In comparison to the lower depression score group, those with higher depression scores had lower heart rate variability during daily life. These findings may be related to the reported relationship between depression and survival risk in patients with coronary artery disease.

Arousal↗
PubMedDate not supplied

Ischemic but not thermal pain sensitivity varies across the menstrual cycle.

OBJECTIVE AND METHOD: Findings from both animal and human research suggest that pain sensitivity changes across the menstrual cycle; however, among humans the nature of these menstrual cycle effects remains unclear. The present study used a repeated-measures design to evaluate changes in thermal and ischemic pain responses during three phases of the menstrual cycle, midfollicular (postmenstrual), ovulatory, and mid-to-late luteal (premenstrual), in 11 healthy women. The cycle phase during which subjects began their participation was determined randomly. Plasma levels of estrogen, progesterone, luteinizing hormone (LH), testosterone, and beta-endorphin were determined at each experimental session. Participants also completed a daily diary of physical and emotional symptoms for two complete menstrual cycles before the experimental sessions. RESULTS: The results indicated that women showed less ischemic pain sensitivity during the midfollicular compared with the ovulatory and mid-to-late luteal phases, but thermal pain responses did not vary significantly across menstrual cycle phases. Physical and emotional symptoms were minimal and did not change significantly across the menstrual cycle. CONCLUSIONS: These findings indicate greater ischemic but not thermal pain sensitivity among women after the midcycle LH surge. The practical relevance and potential mechanisms of these findings are discussed.

Adult↗
PubMedDate not supplied

The Psychophysiological Investigations of Myocardial Ischemia (PIMI) study: objective, methods, and variability of measures.

OBJECTIVE: This study evaluated physiological, neuroendocrine, and psychological status and functioning of patients with coronary artery disease in order to clarify their role in the expression of symptoms during myocardial ischemia (MI), and to establish repeatability of responses to mental stress. Design and methods of the study are presented. METHODS: One hundred ninety-six coronary artery disease patients were examined during physical and mental stress tests in four hospitals. Eligibility criteria included narrowing of at least 50% in the diameter of at least one major coronary artery or verified history of myocardial infarction, and evidence of ischemia on an exercise treadmill test. Psychological, biochemical, and autonomic function data were obtained before, during, and after exposure to mental and exercise stressors during 2 or 3 half-days of testing. Ventricular function was assessed by radionuclide ventriculography, and daily ischemia by ambulatory electrocardiography. Sixty patients returned for a short-term mental stress repeatability study. Twenty-nine individuals presumed to be free of coronary disease were also examined to establish reference values for cardiac responses to mental stress. RESULTS: Study participants were 41 to 80 years of age; 83 (42%) had a history of MI, 6 (3%) of congestive heart failure, and 163 (83%) of chest pain; 170 (87%) were men; and 90 (46%) had ischemia accompanied by angina during exercise treadmill testing. Ischemia during ambulatory monitoring was found in 35 of 90 (39%) patients with and 48 of 106 (45%) patients without angina during exercise-provoked ischemia. Intraobserver variability of ejection fraction changes during bicycle exercise and two mental stress tests (Speech and Stroop) was good (kappa = 1.0, .90, and .76, respectively; percent agreement = 100, 97.5, and 93.8%, respectively). Variability of assessed wall motion abnormalities during bicycle exercise was better (kappa, agreement = 85%) than during Speech or Stroop kappa and .57, percent agreement = 70% and 82.5%, respectively). CONCLUSIONS: Study design, quality control data, and baseline characteristics of patients enrolled for a clinical study of symptomatic and asymptomatic myocardial ischemia are described. Lower repeatability of reading wall motion abnormalities during mental stress than during exercise may be due to smaller effects on wall motion and lack of an indicator for peak mental stress.

Adult↗
PubMedDate not supplied

Reproducibility of mental stress-induced myocardial ischemia in the Psychophysiological Investigations of Myocardial Ischemia (PIMI).

OBJECTIVE: Many patients with coronary artery disease (CAD) develop myocardial ischemia in response to mental stress. This has been documented both in the natural environment and in the laboratory. However, the reproducibility of laboratory mental stress-induced ischemia has not been investigated. METHOD: Sixty patients with documented CAD and a positive exercise stress test discontinued cardiac medications and underwent two standardized mental stress tests (a timed Stroop Color-Word test and a public speaking task) in a nuclear cardiology laboratory (Visit 1), and repeated this procedure between 2 and 8 weeks later (Visit 2). Measurements of cardiovascular function and neurohormonal responses were obtained throughout testing, and mood state was assessed before and after testing. RESULTS: Sixty-eight percent of the 56 patients with detailed radionuclide data from both visits had consistent responses (ie, ischemia either present during both sessions or absent during both) to the Stroop task (kappa = .29, p = .03), 61% had consistent responses to the speech task (kappa = .20, p = .12), and 60% had consistent responses when ischemia was considered present if it occurred during either the Stroop test, the speech task, or both, and absent if it did not occur during either task (kappa = .22, p = .07). Hemodynamic and neuroendocrine responses to the tests were moderately reproducible. CONCLUSIONS: We conclude that two popular laboratory tests for mental stress-induced myocardial ischemia are modestly reproducible. The relatively low reproducibility is probably influenced by uncertainties in detecting relatively small changes in wall motion, habituation of the patient to repeated exposure to psychological stressors, and physiological differences in threshold for ischemia on different days of testing.

Adult↗
PubMedDate not supplied

Race and sex differences in cutaneous pain perception.

OBJECTIVE: The purpose of this study was to determine race and sex differences in cutaneous pain perception. METHODS: Pain perception was measured using a suprathreshold evaluation of pain intensity and pain unpleasantness to a series of thermal stimuli in 27 whites (14 men and 13 women) and 24 African Americans (12 men and 12 women). Blood pressure, depressive symptoms, anxiety state levels, and negative mood were assessed before pain testing to examine whether they might account for any sex or race differences in pain perception that emerged. RESULTS: African Americans rated the stimuli as more unpleasant and showed a tendency to rate it as more intense than whites. Women showed a tendency to rate the stimuli as more unpleasant and more intense than men. In addition, systolic blood pressure was inversely related to pain intensity. After statistically adjusting for systolic blood pressure, sex differences in pain unpleasantness were reduced and sex differences in pain intensity were abolished; race differences were unaltered. CONCLUSIONS: These differences in pain perception may be associated with different pain mechanisms: in the ease of sex, differences in opioid activity and baroreceptor-regulated pain systems; in the case of race, unmeasured psychological characteristics are suggested by the larger differences in ratings of pain unpleasantness than pain intensity.

Adult↗