Biomedical subjects

R D Levy

Publications and source records attributed to R D Levy.

At least 109 records · Page 6Linked to original sources

PubMed1989

Regional pulmonary perfusion following human heart-lung transplantation.

Ventilation and perfusion scans were obtained in six subjects who had undergone heart-lung transplantation with consequent denervation of the cardiopulmonary axis. Two of the subjects had developed obliterative bronchiolitis, which is believed to be a form of chronic rejection. Their pulmonary function tests demonstrated airflow obstruction and their scintigraphic studies were abnormal. In the remaining four subjects without obstructive airways disease, ventilation and planar perfusion scans were normal. Single photon emission computed tomography imaging of pulmonary perfusion in these patients revealed a layered distribution of blood flow indistinguishable from that of normal individuals. It is concluded that neurogenic mechanisms have little influence on the pattern of local pulmonary blood flow at rest.

Adult↗

PubMed1987

Choice of therapy in chronic ischemic heart disease.

The choice of therapy in chronic ischemic heart disease depends on identifying the underlying mechanism. Ambulatory monitoring provides a means of identifying those patients in whom increased myocardial oxygen demand is the most important mechanism and who will respond to a beta blocker. In contrast, those patients with coronary spasm are best treated with a calcium antagonist. The history of angina pectoris and the time of onset may, in itself, be misleading. Detailed ambulatory monitoring studies show that nocturnal angina is frequently due to increased myocardial oxygen demand and in such circumstances should be treated by careful control of the heart rate using a beta blocker without intrinsic sympathomimetic activity. Other factors that will influence the choice of medical therapy must be considered. Smoking is particularly important because it not only acts detrimentally in terms of increased myocardial oxygen demand, but may also interfere with the metabolism of those antianginal agents that are metabolized in the liver. The importance of silent myocardial ischemia has been emphasized recently, and studies using ambulatory pulmonary artery monitoring have shown that silent ischemic episodes have the same significance in terms of hemodynamic effects as painful ischemic episodes. The therapeutic and prognostic implications of these findings need to be explored.

Adrenergic beta-Antagonists↗

PubMed1987

Diurnal variation in left ventricular function: a study of patients with myocardial ischaemia, syndrome X, and of normal controls.

Angina can occur in the early morning. The mechanism of this is unclear and both haemodynamic changes and coronary artery spasm may be important. The purpose of this study was to investigate the diurnal variation in pulmonary artery diastolic pressure (an indirect measure of left ventricular filling pressure) in six normal subjects, 18 patients with coronary artery disease, five with variant angina, and six with syndrome X. A transducer tipped catheter and a simple recording system were used to record ambulatory pulmonary artery diastolic pressure for 24 hours. Variation in pulmonary artery diastolic pressure was related to the timing of episodes of ST segment depression and elevation by simultaneously recording a frequency modulated electrocardiogram. Episodes of ST segment change occurred predominantly in the early morning (midnight to 6 am) in variant angina (eight out of 14 episodes) whereas in syndrome X all episodes were recorded during the day. In coronary artery disease both painful and painless episodes were distributed throughout the day, with 10 out of 67 episodes occurring between midnight and 6 am. A similar diurnal variation in pulmonary artery diastolic pressure was seen in the groups--that is, values were low during the day and higher at night, with the maximum values between midnight and 6 am. The 24 hour median pulmonary artery diastolic pressure was higher in patients with coronary artery disease than in the control group and those with syndrome X. The finding that pulmonary artery diastolic pressure, and therefore left ventricular end diastolic pressure, is greatest in the early morning may represent the background haemodynamic state in which other factors lead to myocardial ischaemia during these hours.

Adult↗

PubMed1987

Should we treat silent ischaemic?

24-hour ambulatory monitoring of the ST segment in patients with angina has shown that ST segment depression may be accompanied by angina pectoris, but it occurs equally often without any symptoms. Approximately half of all episodes of ST segment depression are accompanied by chest pain. Doubt has been expressed as to the significance of ST segment changes that occur in the absence of chest pain, but haemodynamic studies and nuclear imaging have shown that such changes are accompanied by alterations in left ventricular filling pressure. Ambulatory pulmonary artery monitoring has also shown that silent ST segment depression is accompanied by a significant increase in pulmonary artery diastolic pressure, and this does not differ from painful episodes of ST segment depression. Studies using ambulatory monitoring have shown that antianginal drugs are capable of reducing the frequency of ST segment depression accompanied by pain. We have recently performed studies investigating the use of antianginal medications; i.e. beta-blocking drugs with and without sympathomimetic activity, alpha-beta-blocking drugs, calcium antagonists and nitrates in the treatment of both painful and painless ST segment depression. These studies have shown that the effect of these drugs on painless episodes is similar to their effect on painful episodes of myocardial ischaemia. Although the prognostic implications of silent ischaemia and the importance of these therapeutic findings are unknown, it is well known that approximately one-quarter of all myocardial infarctions occur without chest pain. Moreover, recent investigations in unstable angina show that silent myocardial ischaemia is an important predictor of future coronary events.

Blood Pressure↗

PubMed1987

Hypertension and the ischaemic myocardium.

Hypertension and ischaemic heart disease often co-exist. Recent studies, using ambulatory ST-segment and haemodynamic monitoring, have shown that myocardial ischaemia may not necessarily be accompanied by angina pectoris. Unless transient myocardial ischaemia is actively sought it may, therefore, be missed and this may have important prognostic and therapeutic implications. Studies investigating the use of beta-blockers, calcium antagonists and nitrates in angina pectoris have shown that these agents have an equal effect on painless as opposed to painful myocardial ischaemia. While there are no currently completed studies demonstrating the prognostic implication of silent ischaemia in stable angina, it is well known that approximately one-quarter of all myocardial infarctions occur without chest pain. Recent investigation in unstable angina showed that silent ischaemia was an important predictor of future coronary events.

Coronary Disease↗

PubMed1987

Haemodynamic changes during silent myocardial ischaemia.

The haemodynamic significance of asymptomatic ST segment depression has been assessed in patients with coronary artery disease by direct measurement of left ventricular end-diastolic pressure (LVEDP) or pulmonary artery end-diastolic pressure (PADP). Both techniques have demonstrated a rise in pressure during such episodes of ST segment depression recorded in the Coronary Care Unit, cardiac catheter and exercise laboratories or during ambulant activity. Thus silent or asymptomatic ST segment depression is associated with similar haemodynamic changes to that seen during angina pectoris and has considerable therapeutic implications.

Angina Pectoris↗

PubMed1986

Importance of "reciprocal" electrocardiographic changes during occlusion of left anterior descending coronary artery. Studies during percutaneous transluminal coronary angioplasty.

ST-segment depression remote from the region of acute myocardial infarction was investigated in three groups of patients undergoing left anterior descending coronary angioplasty. Ten patients had single-vessel disease, nine concomitant stenoses in one or more other major coronary arteries, and two myocardial infarction after occlusion during angioplasty. Continuous surface electrocardiograms were recorded from leads I, II, III, v2, and v5, before, during, and after coronary angioplasty and ST-segment changes were measured to 0.1 mm. All ten patients with single-vessel disease had ST-segment elevation in lead v2 and nine also had changes in lead III. All nine patients with multivessel disease had ST-segment changes in lead v2; eight of them had concomitant changes in lead III. Both patients with myocardial infarction had elevation in lead v2 and depression in lead III. ST-segment changes began simultaneously in all leads where they occurred. Most (70%) patients with single-vessel disease who had inferior ST-segment depression had a right-dominant coronary circulation. Therefore, the presence of inferior ST-segment depression during left anterior descending coronary artery occlusion does not indicate the presence or absence of multivessel disease. Furthermore, it is unlikely that this change always represents ischaemia remote from the site of infarction; it is merely an electrical phenomenon.

Aged↗

PubMed1986

The incidence and morphology of ischaemic ventricular tachycardia.

Ventricular arrhythmias are a frequent cause of sudden death in patients with coronary artery disease. The incidence and relationship of ventricular tachycardia to periods of myocardial ischaemia in these patients has not been fully investigated. Ambulatory ST-segment monitoring was performed in 100 consecutive patients with chest pain, of whom 74 had significant coronary artery disease. Recordings were analysed for ST-segment changes and episodes of ventricular tachycardia (greater than 3 beats, rate greater than 100 beats min-1). None of the 26 patients with normal coronary arteries, one of the 22 patients (4.5%) with single vessel disease, one of the 22 patients (4.5%) with double vessel disease and four of the 30 patients (13%) with triple vessel disease, had episodes of non-sustained ventricular tachycardia. Four of these six patients had episodes of reversible ST-segment change but ventricular tachycardia was related to these episodes in only two patients. These two patients had multiple episodes of tachycardia which occurred after the onset of ST-segment change and terminated before the ST-segment returned to baseline; they occurred in clusters with a mean of 12 episodes in each cluster. ST-segment change did not follow episodes of ventricular tachycardia in any patient. The number of ventricular complexes in each episode varied between three and 24 beats and were uniform in three of the six patients. The mean heart rate before the onset of tachycardia was 79 +/- 8 beats per minute and the rate of tachycardia had a mean of 170 +/- 34 beats a minute. Less than 10% of the episodes had a prematurity index of less than 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗

PubMed1986

Continuous ambulatory pulmonary artery pressure monitoring. A new method using a transducer tipped catheter and a simple recording system.

A transducer tipped catheter and simple recording system were used for the continuous measurement of ambulatory pulmonary artery pressure. The pulmonary artery pressure was recorded on a miniaturised tape recorder and replayed via an optical writer. Pulmonary arterial systolic and diastolic pressures can be analysed on a beat to beat basis. Continuous ambulatory monitoring was performed for a total 288 hours in 13 patients who were undergoing routine investigation for coronary artery disease. There was less than 1% zero drift and 0.25% linearity error per full scale pressure. The frequency response of the entire system was flat to 8 Hz with a linear phase delay. The transducer tipped catheter and a conventional fluid-filled system were used to measure left ventricular and pulmonary artery end diastolic pressures in eight patients. The correlation between the results obtained by the two methods was excellent. This method could be used at any centre equipped for ambulatory electrocardiographic monitoring.

Adult↗

PubMed1986

Haemodynamic response to myocardial ischaemia during unrestricted activity, exercise testing, and atrial pacing assessed by ambulatory pulmonary artery pressure monitoring.

Ambulatory pulmonary artery pressure monitoring by means of a transducer tipped catheter with a simultaneous frequency modulated electrocardiogram and a miniaturised tape recorder was used to study the haemodynamic implications of ST segment depression in patients with coronary artery disease. Nineteen male patients (mean (SD) age 58 (11) years) with clinical and angiographic evidence of coronary artery disease were studied together with six controls. Changes in the ST segment and pulmonary artery diastolic pressure during treadmill exercise, atrial pacing, and unrestricted ambulant activity were analysed. During exercise, pulmonary artery diastolic pressure rose significantly in patients with coronary artery disease but not in the controls. One patient with ST depression greater than 1 mm did not have a rise in pulmonary artery diastolic pressure on exercise; two had a rise in pulmonary artery diastolic pressure with no ST segment change despite severe angina. The pulmonary artery diastolic pressure tended to rise before or simultaneously with the onset of ST segment depression. The haemodynamic response to atrial pacing was similar in normal controls and patients with coronary artery disease. During ambulatory monitoring there were 29 episodes of ST segment depression all of which were associated with a rise in pulmonary artery diastolic pressure and chest pain. The onset of ST segment depression occurred before a rise in pulmonary artery diastolic pressure in 11 episodes, was simultaneous with it in 11, and followed it in seven episodes. During exercise and ambulatory monitoring there was a correlation between the magnitude of ST segment depression and the rise in pulmonary artery diastolic pressure. Pain was a late feature during exercise, atrial pacing, and anginal episodes. This technique for the first time allows the relation between ST segment changes and haemodynamic alterations in left ventricular function to be assessed in ambulant patients with coronary artery disease.

Aged↗

PubMed1986

Syndrome X: the haemodynamic significance of ST segment depression.

The relation between chest pain, ST segment depression, and changes in left ventricular function was assessed in six patients with angina, a positive exercise test, and normal coronary arteries as assessed by arteriography (syndrome X). In the six patients with syndrome X and in six controls there was no significant rise in pulmonary artery diastolic pressure during treadmill exercise, although there was ST segment depression (range 1-4.5 mm) in the patients with syndrome X. In 19 patients with coronary artery disease, however, the pulmonary artery diastolic pressure increased by a median 5 mm Hg (range 0-13.6 mm Hg) on treadmill exercise. In only one patient with coronary artery disease, who showed 1 mm ST segment depression, was there no rise in pulmonary artery diastolic pressure. During ambulatory monitoring in patients with syndrome X there were 12 episodes of ST segment depression (greater than 1 mm) (4 painful, 8 painless) in which there was no change in pulmonary artery diastolic pressure. In the patients with coronary artery disease there were 29 episodes of angina during ambulatory monitoring and during all of them pulmonary artery diastolic pressure rose by a median 7.5 mm Hg (range 1.8-19.7 mm Hg). Unlike the haemodynamic changes that usually occur during myocardial ischaemia in coronary artery disease, chest pain and ST segment changes in patients with syndrome X are not associated with impaired left ventricular function as assessed by ambulatory pulmonary artery pressure monitoring.

Ambulatory Care↗

PubMed1986

The haemodynamic response to myocardial ischaemia in ambulant patients with variant angina.

The haemodynamic response to myocardial ischaemia in patients with variant angina during ambulatory activity is unknown. Ambulatory pulmonary artery pressure monitoring with a transducer tipped catheter and simultaneous frequency modulated electrocardiograms was used to assess changes in left ventricular function in five male patients (mean age 51.8 years) during variant angina; four patients had coronary artery stenosis and one had normal coronary arteries. Two hundred and seventy hours of ambulatory recordings were analysed. Twenty episodes (12 painful, 8 silent) of ST segment change greater than 1 mm occurred. Episodes tended to occur more frequently in the early morning hours. Six episodes of painful ST elevation were associated with a rise in pulmonary artery diastolic pressure. In the remaining episodes ST segment elevation was of shorter duration and there was no rise in pulmonary artery diastolic pressure. Pain was usually a late feature. Silent ST segment elevation occurred at rest and pulmonary artery diastolic pressure increased in all but one episode. Silent exertional ST segment depression was associated with a greater increase in pulmonary artery diastolic pressure than that seen during ST segment elevation. ST segment depression preceded or followed ST segment elevation in two episodes. The onset of ST segment elevation nearly always preceded the onset of a rise in pulmonary artery diastolic pressure. Ergometrine maleate provocation produced a rise in pulmonary artery diastolic pressure in three patients. In one there was no response to 1000 micrograms but spontaneous episodes of ST segment elevation were recorded during ambulatory monitoring. Treadmill exercise resulted in both ST segment elevation and depression with a similar haemodynamic response during both types of electrocardiographic change. When there is important coronary artery disease in two or more vessels ST segment changes may occur in different territories during treadmill exercise and during spontaneous episodes. Ambulatory pulmonary artery diastolic pressure monitoring is a useful technique for the investigation of variant angina.

Adult↗

PubMed1986

The haemodynamic significance of asymptomatic ST segment depression assessed by ambulatory pulmonary artery pressure monitoring.

A transducer-tipped catheter with simultaneous frequency modulated electrocardiograms and a miniaturised tape recorder was used to record ambulatory pulmonary artery pressure for 24-48 hours in 19 men (mean age 57.7) with clinical and angiographic evidence of coronary artery disease. Sixty seven episodes of ST segment depression (greater than 1 mm) were recorded. Thirty five were accompanied by pain of which six occurred at night; in 34 pulmonary artery diastolic pressure rose significantly. In all but two of the 32 episodes of painless ST segment depression (four of which were at night) there was a significant rise in pulmonary artery diastolic pressure. No such rise was found in six normal subjects during exertion. ST segment changes tended to occur before (24 episodes) or at the same time (27 episodes) as changes in pulmonary artery diastolic pressure. ST segment depression followed an increase in pulmonary artery diastolic pressure in only 13 episodes. The times to maximum ST depression and maximum pulmonary artery diastolic pressure rise were similar. Painful and painless ST segment depression could not be distinguished on the basis of the configuration of the ST segment or in terms of the changes in the pulmonary artery diastolic pressure.

Aged↗

PubMed1985

A study of erythrocyte membrane proteins and urinary polypeptides in conga drumming haemoglobinuria.

The erythrocyte membrane proteins and glycoproteins and urinary polypeptides have been examined in a patient exhibiting intermittent pigmenturia associated with conga drumming. Significant excretion of haemoglobin, albumin and probably erythrocyte carbonic anhydrase but not myoglobin occurred during the acute phase of the conga drumming-induced pigmenturia. This usually ceased within 24-48 h. We found no evidence of aberrant erythrocyte membrane components on electrophoresis with either protein staining or a range of 125I-labelled lectins used for detection.

Adult↗

PubMed1985

Ventilatory muscle function during exercise in air and oxygen in patients with chronic air-flow limitation.

Ventilatory muscle function was examined at rest and during exercise on a cycle ergometer in 8 patients with moderate to severe chronic air-flow limitation (FEV1, 32 +/- 4% predicted) in air and in oxygen. The diaphragmatic electromyogram (EMG) was measured using an esophageal electrode. In addition, measurements of esophageal (Pes), gastric (Pga), and transdiaphragmatic (Pdi) pressures and abdominal wall movements were made. Patients exercised to exhaustion at a constant submaximal workload (80% of maximal power output) inspiring air or 40% O2 in random order on separate days. At end-exercise in air, tidal inspiratory Pes swings were 36 +/- 4% of static maximal inspiratory Pes, and inspiratory Pdi swings were 45 +/- 7% of the static maximal Pdi. Arterial oxygen saturation decreased from 91 +/- 2% at rest to 80 +/- 5% at end-exercise in air. During exercise in air, 5 patients demonstrated a persistent and greater than 20% fall in the ratio of high frequency (150 to 350 Hz) to low frequency (20 to 46 Hz) power (H/L) of the diaphragmatic EMG, indicating impending diaphragmatic fatigue, and 2 patients had paradoxical motion of the abdominal wall. Exercise time at the same constant work load increased from 3.0 +/- 0.6 min in air to 6.4 +/- 1.2 min in O2 (p less than 0.005). At the comparable time during exercise in O2 to end-exercise in air, minute ventilation was less by 13% (p less than 0.005), which was entirely attributable to a lower frequency of breathing. Mean inspiratory and expiratory flows and heart rate were all significantly lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗

PubMed1984

The neuromuscular features of acromegaly: a clinical and pathological study.

A study of the neuromuscular features of acromegaly was performed in six patients. Clinical assessment was supplemented by quadriceps force measurements, plasma creatine kinase (CK) activities, electromyography (EMG) and nerve conduction studies. Muscle mass was measured by urinary creatinine/height indices (CHI) and cross sectional area (CSA) of thighs and calves on computed tomography. Quadriceps force/unit cross sectional area was derived. Needle biopsies of vastus lateralis were studied by histochemical and ultrastructural methods. Mean fibre area (MFA) and fibre type proportions were measured. Most of the subjects studied had muscle pain and proximal muscle weakness confirmed by quadriceps force measurements. This occurred in the absence of muscle wasting, as shown by cross sectional area measurements and normal or raised creatinine/height indices. "Myopathic" features were demonstrated by needle biopsy in half the patients and occasionally by electromyography and raised plasma creatine kinase activity. Abnormalities on needle biopsy included variation in fibre size, type 2 fibre atrophy and large type 1 MFA relative to type 2 MFA. Electronmicroscopy showed the non-specific findings of increased glycogen accumulation, excess lipofuscin pigment and myofilament loss.

Acromegaly↗

PubMed1984

Relaxation rate of mouth pressure with sniffs at rest and with inspiratory muscle fatigue.

The relaxation rate of transdiaphragmatic pressure (Pdi) after voluntary contractions of the diaphragm slows with fatigue. We determined a range of values for the relaxation rate of mouth pressure (Pm) after voluntary contractions of the inspiratory muscles in 27 normal men and women at various lung volumes at rest. Values were similar for both sexes. The relaxation rates were similar at functional residual capacity (FRC) and below FRC, but were greater above FRC (p less than 0.05). In addition, we studied the effect of diaphragmatic fatigue induced by inspiratory resistive loading on the relaxation rates of Pdi and Pm with voluntary contractions of the inspiratory muscles in 6 subjects. With fatigue, the relaxation rates of Pdi and Pm both decreased by similar amounts, indicating that a decrease in the relaxation rate of Pm is as useful a predictor of inspiratory muscle fatigue as a decrease in the relaxation rate of Pdi has been shown to be for the diaphragm. The relaxation rate of Pm varies widely in normal subjects at rest, so isolated values do not indicate whether fatigue is present or developing. However, this may be predicted if relaxation rate decreases with serial measurements.

Adult↗

PubMed1984

Unsuspected caffeine toxicity complicating theophylline therapy.

A 58-year-old man with a history of alcoholic liver disease and chronic airflow obstruction presented with heart failure and acute bronchitis. Plasma methylxanthines were estimated as a guide to further theophylline therapy and serious caffeine accumulation was noted in the presence of a subtherapeutic concentration of theophylline. After 3 weeks on a caffeine-free diet theophylline and caffeine challenge tests were performed which demonstrated the ease with which caffeine could accumulate. The importance of caffeine accumulation during theophylline therapy is discussed.

Bronchitis↗