Biomedical subjects
R L Bishop
Publications and source records attributed to R L Bishop.
Noninvasive assessment of left ventricular performance in patients with ischemic heart disease: ear densitographic study during uninterrupted treadmill exercise.
Among 738 consecutive patients with chest pain referred for exercise testing, only 17 men fulfilled strict criteria for this pilot study: (1) achievement of at least 90 percent of age-predicted maximal heart rate or electrocardiographic criteria for a positive test; (2) subsequent coronary angiography; (3) exclusion of prior heart disease; and (4) absence of medication. Measurements of systolic time intervals obtained with ear densitography during early exercise differentiated 10 patients with coronary artery disease (Group 1) from 17 men (7 patients plus 10 normal volunteers) with normal coronary arteries (Group 2). Despite nearly identical heart rate and blood pressure responses in both groups, men in Group 1 had a significantly greater reduction of preejection period (PEP) at 1 minute and 4 minutes as well as a greater decrease in PEP/LVET (left ventricular ejection time) ratio. Differences were most significant when expressed as percent change of PEP/LVET ratio from control value (p less than 0.001 at both 1 minute and 4 minutes). After 4 minutes, men in Group 1 had no further decrease in PEP/LVET ratio and in 8 of the 10 men PEP/LVET ratio then increased to peak exercise. By contrast, PEP/LVET ratio continued to decrease to peak exercise in men in Group 2. The early floor in PEP/LVET ratio in Group 1 represents limited functional reserve and the subsequent increase suggests functional deterioration. Thus, densitographic systolic time interval measurements during uninterrupted exercise in unmedicated subjects appear to improve the sensitivity and specificity of the conventional treadmill test.
Midsystolic closure of the aortic valve in primary pulmonary hypertension.
Echocardiographic examination in a patient with primary pulmonary hypertension demonstrated midsystolic closure of the aortic valve, which has often been described in hypertrophic cardiomyopathy with or without obstruction, in discrete subaortic stenosis, and in ruptured aneurysm of the right coronary sinus of Valsalva. A possible mechanism for this finding in primary pulmonary hypertension and differential diagnosis from other diseases are discussed.
Cardiac responses to impulse exercise and recovery: systolic time intervals.
Exercise responses depend on work load and its pattern of delivery. Administering a very brief ("impulse") load aims to elicit significant responses through biologic sensitivity to rate - rather than degree - of change. Electrocardiograms, systolic time intervals (STI) and heart rate (HR) were recorded continuously in 10 normal subjects during and after brief (20-sec) bicycle exercise at 50, 100 and 150 W. The purpose of this protocol was to identify a low load impulse-type exercise challenge which would be optimal in terms of (a) reproduction of the time course of exercise changes produced by longer duration (steady-state) exercise, (b) rapid achievement of quantitative responses reaching some or all of the steady-state changes at comparable work load, and (c) absence of ST changes in normal subjects. The onset of exercise produced the greatest rates of change. Directional changes and time course of all measurements paralleled those of steady-state exercise and recovery at the same loads: HR, ejection time index (ETI) and corrected ejection time (ETc) increased sharply; preejection period (PEP) and PEP/LVET fell sharply. Ejection time (LVET), stable through most of exercise, "paradoxically" decreased for up to 15 sec of recovery despite decreasing heart rates. For all measurements, restitution to control levels was complete by one minute of recovery.
Cardiac response during uninterrupted treadmill exercise and recovery: measurement by systolic time intervals.
In 12 normal subjects, use of ear densitography permitted measurement of systolic time intervals (STI) during uninterrupted treadmill exercise to over 90 percent maximal heart rate on a modified Bruce protocol. Results for control (sitting leads to standing) leads to end-exercise at 18 minutes leads to 10 minutes' sitting recovery were--heart rate (HR): (77 leads to 861 leads to 171 leads to 98 beats per minute; preejection period (PEP): (106 leads to 111) leads to 49 leads to 110 msec; ejection time index (ETI) (351 leads to 330) leads to 380 leads to 366 msec; PEP/LVET (0.42 leads to 0.49) leads to 0.29 leads to 0.45. Heart rate increased steadily to 18 minutes. In contrast, the PEP/LVET decrease was almost complete by three minutes and both ETI and PEP responses were bimodal with respective plateaus between three and six minutes and three and nine minutes. All STI and HR curves showed rapid restitution during early recovery. The changes during treadmill exercise were numerically comparable to those during bicycle exercise at a common heart rate. The results indicate that it is technically feasible to measure systolic time intervals with precision during uninterrupted treadmill exercise; responses to treadmill exercise were in the direction expected and quantitatively comparable to bicycle exercise at comparable stress level. These obervations provide the technical and physiologic bases for applying this method in clinical treadmill exercise testing.
Sodium bicarbonate administration during cardiac arrest. Effect on arterial pH PCO2, and osmolality.
Arterial pH, Pco2, and osmolality were determined serially during cardiac resuscitation in patients and in dogs, with and without administration of sodium bicarbonate. These studies demonstrate that (1) in the absence of preexisting acidosis, severe acidosis can be prevented by adequate ventilation alone; (2) sodium bicarbonate administration results in a significant rise in arterial Pco2, which parallels the rise in pH despite adequate ventilation; (3) during prolonged cardiac and resuscitation, there is a rise in arterial osmolality that is accentuated by sodium bicarbonate. These studies suggest that sodium bicarbonate should not be used during resuscitation (1) in the absence of effective hyperventilation or where carbon dioxide removal is inadequate despite adequate ventilation, (2) in repeated doses, without confirmation of substantial acidosis, or (3) when cardiac arrest has been of brief duration and preexisting acidosis is unlikely. These studies also point to the need for a reappraisal of other buffers that do not elevate the arterial Pco2.
Effects of pH and pCO2 on performance of ischemic myocardium.
Contractile performance of ischemic feline myocardium was evaluated under conditions of selective changes in perfusate in pH and pCO2. A substantial increase in myocardial performance was noted when the pCO2 was lowered at constant pH, and depression of performance was noted when the pCO2 was increased at constant pH. Perfusate acidosis at constant pCO2 resulted in depression of performance and decreased performance only after 20 min of exposure. Alkalosis did not increase performance and decreased performance transiently during mild ischemia. These studies suggest that performance of myocardium during ischemia is closely related to tissue pCO2 and is minimally related to the level of extracellular pH.
RIGIDITY OF POSITIVELY CURVED KAEHLER MANIFOLDS.
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ON CURVATURE AND EULER-POINCARE CHARACTERISTIC.
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Development of an ambulatory systolic time interval monitoring system.
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Measurement of protein biosynthesis in Pneumocystis carinii to investigate the effects of translation-specific inhibitors.
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