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Biomedical subjects

A M Ross

Publications and source records attributed to A M Ross.

At least 73 records · Page 4Linked to original sources
PubMed1991

The role of coronary angioplasty in the management of unstable angina pectoris.

Using percutaneous transluminal coronary angioplasty (PTCA) as primary therapy for unstable angina is quite common. Unstable angina appears to be the indication for the procedure in approximately one third of all PTCA attempts. Considering the unstable nature of the plaque in this type of angina, and the increased risk of abrupt occlusion due to frequent intraluminal thrombus, the generally reported rate of success, approximately 85%, is highly respectable. The evidence supporting a period of pretreatment with aspirin and heparin is strong. Less certain is the value of concomitantly administering plasminogen activators. Pending data should produce important further guidelines for effective therapy. Major trials, some using fibrinolytics as well as taking an overall aggressive, interventional approach (like that taken by UNSA, TIMI-III, and others), are reaching the recruitment-completion and promulgation stages.

Angina, Unstable↗
PubMed1991

Late potentials and their relation to ventricular function in human immunodeficiency virus infection.

Signal-averaged electrocardiograms were performed in 225 patients with serologic evidence of human immunodeficiency virus infection as part of a prospective longitudinal study of patients with HIV-associated heart disease and 12 seronegative control subjects. The duration of signal-averaged QRS vector, root-mean-square voltage of the terminal 40 ms of the vector magnitude and the duration of the low-amplitude (less than 40 microV) signal were determined during serial visits at 4-month intervals. One or more of these variables was abnormal on initial visit in 59 of patients (26%); QRS duration was greater than 114 ms in 9 patients (4%), root-mean-square voltage less than 20 microV in 55 patients (24%) and low-amplitude signal duration greater than 39 ms in 43 (19%). In contrast, none of the seronegative control subjects had any abnormal variables (p less than 0.03). During follow-up (mean 10 +/- 8 months), 26 patients with initially normal studies developed abnormal variables and 24 with abnormal signal-averaged electrocardiograms reverted to normal. Left ventricular contractility was assessed by echocardiography using the rate-corrected velocity of fiber shortening-end-diastolic wall stress relation. Late potentials were not related to contractile abnormalities. Clinical arrhythmias were rare and did not appear more frequent among patients with late potentials. Thus, late potentials were both common and evanescent in patients infected with human immunodeficiency virus.

Adult↗
PubMed1990

A comparison between heparin and low-dose aspirin as adjunctive therapy with tissue plasminogen activator for acute myocardial infarction. Heparin-Aspirin Reperfusion Trial (HART) Investigators.

BACKGROUND: We report the results of the Heparin-Aspirin Reperfusion Trial, a collaborative study comparing early intravenous heparin with oral aspirin as adjunctive treatment when recombinant tissue plasminogen activator (rt-PA) is used for coronary thrombolysis during acute myocardial infarction. METHODS: Two hundred five patients were randomly assigned to receive either immediate and then continuous intravenous heparin (starting with a 5000-unit bolus; n = 106) or immediate and then daily oral aspirin (80 mg; n = 99) together with rt-PA (100 mg intravenously over a six-hour period) initiated within six hours of the onset of symptoms. We evaluated the patency of the infarct-related artery by angiography 7 to 24 hours after beginning rt-PA infusion, the frequency of reocclusion of the artery by repeat angiography on day 7, and ischemic or hemorrhagic complications during the hospital stay. RESULTS: At the time of the first angiogram, 82 percent of the infarct-related arteries in the patients assigned to heparin were patent, as compared with only 52 percent in the aspirin group (P less than 0.0001). Of the initially patent vessels, 88 percent remained patent after seven days in the heparin group, as compared with 95 percent in the aspirin group (P not significant). The numbers of hemorrhagic events (18 in the heparin and 15 in the aspirin group) and recurrent ischemic events (8 in the heparin and 2 in the aspirin group) were similar in the two groups. CONCLUSIONS: Coronary patency rates associated with rt-PA are higher with early concomitant systemic heparin treatment than with concomitant low-dose oral aspirin. This observation has important implications for clinical practice and should be considered in the design and interpretation of clinical trials involving coronary thrombolytic therapy.

Administration, Oral↗
PubMed1990

Nested polymerase chain reaction assay for the detection of cytomegalovirus overcomes false positives caused by contamination with fragmented DNA.

The polymerase chain reaction (PCR) technique offers a promising alternative to tissue culture for the rapid and sensitive detection of cytomegalovirus (CMV) infection. However, high levels of background amplification detected in samples containing water but no DNA make interpretation of borderline positive samples extremely difficult and reduce the sensitivity of the assay. The signal from amplification of water or positive samples can be eliminated by DNase treatment, but not by filtration through anisotropic membrane, autoclaving, or ultraviolet irradiation. A lag time of 10 to 12 cycles is observed before the reactions with water will show product formation by liquid hybridization detection. The use of nested PCR eliminates the background and, in serial dilutions of a positive sample, shows a 500- to 1000-fold increase in sensitivity by liquid hybridization detection. We suggest that the background signal is arising from small fragments of DNA, which may be produced by autoclaving viral culture material. Such fragments would escape filtration, and overlapping fragments of DNA can prime one another to form complete mosaic sequences that will then amplify. Nested PCR, appropriately controlled for the number of cycles at each step, should successfully overcome such false positives caused by fragmented DNA, no matter if the contamination occurs at the collection site, in processing, or at the facility performing the test.

Base Sequence↗
PubMed1990

Implications of the TIMI Trials.

The TIMI Trials consist of three primary studies plus numerous ancillary observations. TIMI I was the direct reperfusion comparison between streptokinase and TPA. The central observations were: Higher reperfusion rates with TPA; Equivalent frequencies of bleeding complications; No differences in clinical outcome parameters; Only early reperfusion produced LV function improvement. TIMI IIA compared routine post-IV lytic therapy (TPA) immediate PTCA with a delayed interventional approach at 18-48 hours post lysis. The study demonstrated: Equivalent outcome LV function; Equivalent mortality rates; More emergency CABG in the "immediate" group; More hemorrhagic complications in the immediate group. TIMI IIB compared delayed but routine interventional post-lytic care (PTCA) with a more conservative strategy. Additionally patients were secondarily randomized to acute administration of IV beta blocker (metoprolol) or delayed administration of beta blocker, starting on Day 6. The primary results of this investigation include: A very low early (2 week) mortality rate with either strategy (about 5%); preserved low mortality at the one year follow up for both groups; no difference (routine intervention versus conservative strategy) in outcome LV function; no difference in comparative mortality rates; less recurrent ischemia in the routine PTCA group; 13% need for PTCA in the conservative group; no difference in LV function based upon beta blockade assignment but some decrease in mortality in acute beta blockade subgroups.

Cohort Studies↗
PubMed1990

Role of angioplasty in myocardial infarction management strategies: a review.

The role of angioplasty in acute myocardial infarction has been extensively studied in the past few years. Although angioplasty in some circumstances can be the primary reperfusion intervention, logistic problems and the excellent results of intravenous thrombolytic therapy have resulted in postlytic angioplasty being the preferred use of this interventional strategy. Clinical trials of this strategy have not supported its routine use, however, and a much more selective application of postthrombolytic coronary artery dilation is advocated at this time.

Angioplasty, Balloon, Coronary↗
PubMed1989

Patient selection for thrombolytic therapy.

Recent studies have shown that the use of thrombolytic therapy in patients with acute myocardial infarction can reduce mortality 20 to 52%. However, patient selection issues remain to be resolved. These issues include the time window for therapy, treatment based on the site of infarction, treatment based on electrocardiographic criteria and treatment of the elderly population.

Aged↗
PubMed1989

Clinical and hemodynamic significance of left ventricular diastolic volume changes by exercise radionuclide ventriculography in coronary artery disease.

Recent studies have suggested that left ventricular (LV) dilatation during exercise radionuclide ventriculography may identify coronary artery disease (CAD). Coronary anatomy and LV end-diastolic pressure at catheterization were compared with results of supine exercise radionuclide ventriculography in 66 patients evaluated for chest pain. Forty-six patients had significant CAD (greater than 75% diameter stenosis) and 20 patients were normal. Radionuclide ventriculography was performed within 18 hours of catheterization, at rest and at peak exercise. Relative LV end-diastolic volumes were extrapolated from end-diastolic counts. LV end-diastolic counts increased during exercise in 19 of 20 normal subjects. In patients with CAD, LV end-diastolic counts increased in 35 (group A) and decreased in 11 (group B). The percent change in LV end-diastolic counts from rest to exercise, rest ejection fraction, exercise ejection fraction and rest LV end-diastolic pressure for each group were 20 +/- 23%, 60 +/- 13%, 67 +/- 13% and 8 +/- 3 mm Hg in normal subjects; 20 +/- 20%, 50 +/- 12%, 47 +/- 13% and 12 +/- 4 mm Hg in group A; and -9 +/- 8%, 54 +/- 21%, 49 +/- 18% and 21 +/- 7 mm Hg in group B (mean +/- standard deviation). An increase in LV end-diastolic counts was unrelated to ejection fraction response or presence of underlying CAD but only correlated to rest LV end-diastolic pressure (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Catheterization↗
PubMed1989

Prevalence of cardiac abnormalities in human immunodeficiency virus infection.

The prevalence of cardiac abnormalities in the spectrum of human immunodeficiency virus (HIV) infection is unknown. Sixty consecutive HIV-infected patients were studied using echocardiograms, electrocardiograms (50 patients) and ambulatory electrocardiographic monitoring (43 patients). Group A (25 patients) were seropositive but pre-AIDS, whereas group B (35 patients) had AIDS and included 24 with an active opportunistic infection (group B1) and 11 without it (group B2). Abnormalities were identified in 32 of 60 patients (53%) and were more frequent in group B (23 of 35, 66%) than in group A (9 of 25, 36%, p less than 0.05) but independent of active opportunistic infection (15 of 24, 62%, in group B1 vs 8 of 11, 73%, in group B2). Echocardiographic abnormalities were identified in 21 of 60 patients (35%), including 7 of 25 (28%) in group A vs 14 of 35 (40%) in group B (difference not significant), and 7 of 24 (29%) in group B1 vs 7 of 11 (64%) in group B2 (difference not significant). Those patients with an absolute CD4 lymphocyte count less than or equal to 100/mm3 had a higher prevalence of echocardiographic abnormalities (12 of 22) than those with CD4 counts greater than 100/mm3 (1 of 14, p less than 0.01). Left ventricular dilation or hypokinesis was identified in 14 of 60 patients (23%), including 4 of 25 (16%) in group A and 10 of 35 (29%) in group B. Electrocardiographic abnormalities were seen in 22 of 50 patients (44%) including 5 of 18 (28%) in group A and 17 of 32 (53%) in group B (difference not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1989

Computer analysis suggests a role for signal sequences in processing polyproteins of enveloped RNA viruses and as a mechanism of viral fusion.

We have used a computer program to scan the entire sequence of viral polyproteins for eucaryotic signal sequences. The method is based on that of von Heijne (1). The program calculates a score for each residue in a polyprotein. The score indicates the resemblance of each residue to that at the cleavage site of a typical N-terminal eucaryotic signal sequence. The program correctly predicts the known N-terminal signal sequence cleavage sites of several cellular and viral proteins. The analysis demonstrates that the polyproteins of enveloped RNA viruses--including the alphaviruses, flaviviruses, and bunyaviruses--contain several internal signal-sequence-like regions. The predicted cleavage site in these internal sequences are often known cleavage sites for processing of the polyprotein and are amongst the highest scoring residues with this algorithm. These results indicate a role for the cellular enzyme signal peptidase in the processing of several viral polyproteins. Not all high-scoring residues are sites of cleavage, suggesting a difference between N-terminal and internal signal sequences. This may reflect the secondary structure of the latter. Signal sequences were also found at the N-termini of the fusion proteins of the paramyxoviruses and the retroviruses. This suggests a mechanism of viral fusion analogous to that by which proteins are translocated through the membranes of the endoplasmic reticulum at synthesis.

Algorithms↗
PubMed1989

Surgical exploration before computed tomography scanning in children with traumatic tentorial herniation.

Seventeen consecutive children with early clinical signs of tentorial herniation after head injury underwent immediate burr-hole exploration before computed tomography scanning. In nine children (53%), a subdural hematoma was discovered and immediately evacuated. In one, a small intracerebral hemorrhage was diagnosed by intraoperative ultrasonography. Postoperative studies showed that no intraaxial or extraaxial hematoma was missed by surgical exploration. Nine children (53%) survived; eight (47%) died. The survival rate was higher among patients with a mass lesion than among those without. Seven children had a good recovery, and two were moderately disabled (mean follow-up, 15.2 months). We conclude that a significant proportion of head-injured children with clinical signs of tentorial herniation have extraaxial hematomas that can be readily identified and evacuated by immediate surgical exploration. The survival rate and extent of recovery in children appear to be better than in similarly injured adults.

Adolescent↗
PubMed1989

DNA typing and forensic science.

With new typing techniques forensic scientists can characterise individuals at the fundamental level of their DNA. Variation between individuals at this level can be used to discriminate between them. Why this is so and how it is achieved is described in relatively simple terms for legal and medical practitioners who have no formal training in genetics.

Base Sequence↗
PubMed1989

Brain shift, level of consciousness, and restoration of consciousness in patients with acute intracranial hematoma.

Recently, Ropper reported that horizontal brain shift caused by acute unilateral mass lesions correlated closely with consciousness, and suggested that recovery of consciousness was unlikely to occur after surgical evacuation if the shift was insufficient to explain the observed diminution of consciousness. The authors have sought to confirm the correlation of pineal shift with level of consciousness and to assess the prognostic value of brain shift measurements in a prospective study. Forty-six patients (19 with subdural hematoma, 14 with intracerebral hematoma, and 13 with epidural hematoma) were accrued to the study group consecutively. A correlation was found between a decrease in the level of consciousness and a significant increase in the mean lateral brain displacement at the pineal gland (from 3.8 to 7.0 mm) and septum (5.4 to 12.2 mm). When outcome was examined in patients who were stuporous or comatose on admission, a significant increase in septal shift was found among patients with a poor outcome, but there was no significant relationship between outcome and degree of pineal or aqueductal shift. A poor outcome was more likely with effacement of both perimesencephalic cisterns or the ipsilateral cistern, but not the contralateral cistern, although this difference did not reach statistical significance. These results do not substantiate the value of brain shift as an independent prognostic factor after evacuation of an acute unilateral mass lesion. The decision to operate and the determination of prognosis should be based rather on established criteria such as the clinical examination, age of the patient, and the mechanism of injury.

Acute Disease↗
PubMed1989

Thrombolytic therapy for acute myocardial infarction.

This decade has witnessed the establishment of thrombolysis, the most widely available therapeutic intervention that specifically treats the direct cause of myocardial infarction and leads to biologically and clinically compelling patient outcome benefits. The next series of investigational tasks will refine issues such as patient and drug selection and optimal postlysis strategies.

Clinical Trials as Topic↗
PubMed1989

Myocardial infarction: rationale for therapy in 1989.

The rationale for the therapy of acute myocardial infarction is logically based upon recognition of the etiologic role of acute thrombosis; hence the primary therapeutic goal is to restore coronary artery patency (and subsequently to preserve that patency). Multiple thrombolytic drugs are variably successful in accomplishing that objective as, in special circumstances, are acute mechanical interventions. After reperfusion, additional strategies are advocated both to preserve patency and to enhance the benefit of reperfusion. The state of our current understanding has been achieved through a productive combination of individual observations and inventiveness as well as painstaking clinical trials. While the major questions now appear to have satisfactory answers, numerous secondary questions have been generated in an effort to further refine the therapeutic algorithms as well as possibly expand the indications to a wider cohort of patients than have been traditionally treated and/or studied to date.

Angioplasty, Balloon, Coronary↗
PubMed1988

The uncertain role of thrombolytic angioplasty within the treatment strategy for myocardial infarction.

The logical hypothesis that early angioplasty after lytic therapy would be of considerable clinical value flows from the recognized shortcomings of pharmacologic reperfusion efforts. These shortcomings are: (1) failure to lyse some thrombotic occlusions; (2) limited quantifiable salvage relative to risk area, possibly related to low magnitude or reperfusion coronary flow through a tight residual stenosis; (3) frequent early postlytic reocclusion and reinfarction; and (4) common postinfarction angina after lysis and some degree of salvage. Recently however, important controlled clinical trials of percutaneous transluminal coronary angioplasty (PTCA) after lytic therapy (most notably Thrombolysis and Angioplasty in Myocardial Infarction study group, Thrombolysis in Myocardial Infarction trial and the European Cooperative trial) have not confirmed this hypothesis. Very early PTCA after intravenous lytic therapy has not produced a favorable short-term outcome compared with delayed PTCA or a more conservative approach. Where is the flaw? Is it the hypothesis, the patient selection criteria or the specifics of therapeutic algorithms? While these issues are further investigated, current prudent clinical recommendations are best modified downward from enthusiastic rapid postlytic dilatation.

Angioplasty, Balloon↗