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Biomedical subjects

D Cooke

Publications and source records attributed to D Cooke.

At least 19 recordsLinked to original sources
PubMed2001

Efficacy and safety of bimatoprost in patients with elevated intraocular pressure: a 30-day comparison with latanoprost.

PURPOSE: To compare the safety and efficacy of bimatoprost and latanoprost in patients with primary open-angle glaucoma or ocular hypertension. METHODS: This was a 30-day, multicenter, double-masked, randomized, clinical trial. Patients (n = 64) diagnosed with primary open-angle glaucoma or ocular hypertension were randomly assigned to receive bimatoprost 0.03%, latanoprost 0.005%, or vehicle topically in both eyes once daily, in the evening, for 29 days. The primary endpoint was the reduction in IOP from baseline on day 14 and day 29. Secondary outcome measures included eye examinations and safety parameters. RESULTS: Bimatoprost and latanoprost significantly lowered IOP from baseline (p <.001). Bimatoprost lowered IOP more than latanoprost at every timepoint measured (bimatoprost: 25-34% reduction, 5.9-8.9 mm Hg; latanoprost: 20-31% reduction, 4.4-7.9 mm Hg), although the between-group differences did not reach statistical significance. Over the 12-hour course of IOP measurements on day 29, bimatoprost provided better diurnal IOP control than latanoprost (p =.0378, area under the curve of diurnal IOP reductions, 1-way ANOVA with pairwise t-test). Both treatment regimens were safe and well tolerated, with no significant between-group differences in reports of specific adverse events. The most common side effect was conjunctival hyperemia, which was similarly apparent in the bimatoprost and latanoprost treatment groups. CONCLUSIONS: At the end of this 30-day trial, once-daily bimatoprost 0.03% provided better diurnal IOP control than latanoprost and was safe and well tolerated in patients with ocular hypertension and glaucoma.

Administration, Topical↗
PubMed2000

Linkage and LOH studies in 19 cylindromatosis families show no evidence of genetic heterogeneity and refine the CYLD locus on chromosome 16q12-q13.

Familial cylindromatosis is an autosomal dominant predisposition to multiple neoplasms of the skin appendages. The susceptibility gene has previously been mapped to chromosome 16q12-q13 and has features of a recessive oncogene/tumour suppressor gene. We have now evaluated 19 families with this disease by a combination of genetic linkage analysis and loss of heterozygosity in cylindromas from affected individuals. All 15 informative families show linkage to this locus, providing no evidence for genetic heterogeneity. Recombinant mapping has placed the gene in an interval of approximately 1 Mb. There is no evidence, between families, of haplotype sharing that might be indicative of common founder mutations.

Carcinoma, Adenoid Cystic↗
PubMed2000

Echocardiographic validation of gated SPECT ventricular function measurements.

UNLABELLED: Left ventricular (LV) volumes are valuable prognostic indicators in the management of coronary artery disease and traditionally have been obtained by x-ray contrast angiography or echocardiography. There now are several scintigraphic methods to compute volumes that are based on different LV modeling assumptions. Both the reasons that calculations from different nuclear techniques can disagree with one another and the relationship of these values to the more conventional echocardiographic measurements must be investigated thoroughly for calculations to be interpretable for individual patients. METHODS: Echocardiographic volumes were determined in 33 retrospective subjects with coronary artery disease (mean age, 61 +/- 12 y; 42% men; 70% with abnormal perfusion and 58% with abnormal segmental wall motion) using the modified Simpson's rule technique applied to digitized apical 4-chamber and apical 2-chamber views of 4 averaged heartbeats. These volumes were compared with those from 3 gated SPECT methods based on Simpson's rule LV modeling similar to standard echocardiographic algorithms (SPECT EF from St. Luke's-Roosevelt Hospital) (method 1), Gaussian myocardial count profile curve fitting (QGS from Cedars-Sinai Medical Center) (method 2), and an endocardial model based on perfusion sampling and count-based thickening (Cardiac Toolbox from Emory University) (method 3). RESULTS: By ANOVA, there were no significant differences among ejection fractions (EFs), but there were for volumes. Paired t test analysis showed volumes from methods 2 and 3 to be significantly larger than echocardiographic volumes and larger than those of method 1. Linear regression analysis comparing gated SPECT and echocardiographic volumes showed a nearly identical strong correlation (r = 0.92; P < 0.000001) for all 3 methods. Excellent correlation also was found among gated SPECT volumes from the 3 methods (r = 0.94). Bland-Altman analysis and t tests showed that method 1 volumes (70 +/- 61 mL) were the same as for echocardiography (77 +/- 55 mL), but volumes were overestimated by method 2 (105 +/- 74 mL) and method 3 (127 +/- 92 mL), particularly for larger volumes. Pearson coefficients for EFs compared with echocardiography were r = 0.82, 0.75, and 0.72 for methods 1-3, respectively. EFs correlated strongly among the 3 gated SPECT methods (r = 0.86-0.92). The Fisher z test showed no differences among these methods for any of the volume or EF linear correlation analyses. CONCLUSION: All gated SPECT parameters correlated well with echocardiographic values. However, the gated SPECT method for which underlying assumptions most closely resembled those commonly used in echocardiography produced mean volume values closest in agreement with echocardiographic measurements.

Analysis of Variance↗
PubMed1999

Comparison of the tetrazolium salt assay for succinate dehydrogenase with the cytosensor microphysiometer in the assessment of compound toxicities.

The cytosensor microphysiometer (a biosensing instrument for detecting cellular metabolism) was compared to the established tetrazolium salt assay as a chemosensitivity test. Two coumarin compounds, 7-hydroxycoumarin and esculetin, were examined to determine their effect on the cellular metabolism of A431 cells over a 24-h exposure period. In the tetrazolium salt assay, 7-hydroxycoumarin caused suppression of the succinate dehydrogenase activity at concentrations greater than 10 microg/ml. Esculetin exerted a more serious effect on succinate dehydrogenase, with decreases in activity observed at greater than 1 microg/ml. The observed effect was dose-dependent for both compounds examined. The metabolic activities of cells exposed to 100 microg/ml of drug were 90.37 +/- 2.8 and 71.62 +/- 2.96 (n = 3), of control values, for 7-hydroxycoumarin and esculetin, respectively. Using the cytosensor microphysiometer to assess metabolic activities, a similar pattern of inhibition was observed, with esculetin more detrimental to cellular metabolism than 7-hydroxycoumarin. The effect was dose- and time-dependent for both compounds. 7-Hydroxycoumarin (100 microg/ml) caused the cellular metabolic rate to drop to 44.21 +/- 5.34% (n = 4) of the control metabolic rate, while 100 microg/ml esculetin caused the metabolic rate to fall to 21.5 +/- 4.54% (n = 4) of the control rate. The cytosensor method proved to be superior to the tetrazolium salt assay for a number of reasons, which are discussed in this paper.

Antioxidants↗
PubMed1999

Mechanical properties of medical grade expanded polytetrafluoroethylene: the effects of internodal distance, density, and displacement rate.

Expanded polytetrafluoroethylene (e-PTFE) is used successfully in a multitude of biomedical and clinical applications. The success of this biomaterial is due to its microporous structure that allows biointegration for fixation, as well as overall mechanical integrity. The mechanical properties and degree of tissue ingrowth depend on the microstructure of the expanded polymer foam, yet little is known about the correlation of the internodal distance and other microstructural features with the monotonic tensile properties. Complete structure-property correlation can be used to provide invaluable knowledge for the design of biomedical devices. The purpose of this study was to investigate the monotonic tensile properties of e-PTFE over a range of medically relevant microstructural features and manufacturing parameters. The microstructural and manufacturing parameters considered were internodal distance, linear density, volumetric density, and reduction ratio. Additionally, the effect of displacement rate on mechanical properties was studied. We found that the ultimate stress and strain increased linearly with linear density (R2 = 0.88 and 0.67, respectively). Surprisingly, elastic modulus did not correlate with any parameter measured and only weak correlations were found between all properties and internodal distance. The yield and ultimate stresses increased with increasing displacement rate (R2 = 0.88 and 0.57, respectively). The findings from this study indicate that linear density is a better predictor of mechanical properties than internodal distance and may be the preferred parameter to control when specifying a material for implantation in load bearing situations.

Biocompatible Materials↗
PubMed1999

Repression at a distance by the global regulator KorB of promiscuous IncP plasmids.

KorB protein (358 amino acids) binds to 12 highly conserved sequences on the RK2 genome and co-ordinates the expression of at least five operons encoding genes for stable inheritance and plasmid transfer. KorB represses the trfA, korA and klaA promoters where it binds 4 bp upstream of the -35 region (class I KorB operators, OB). We show here that KorB on its own can also repress the trbA, trbB, kfrA and kleA promoters where OB is between 80 and 189 bp away from the transcription start point (class II operator). A C-terminal deletion of 17 amino acids resulted in the loss of KorB's ability to repress through class II operator but not through class I operator. This deletion reduced multimerization of His6-tailed KorB protein in vitro and greatly reduced binding specificity for fragments containing OB sequences. At the trbBp region, where OB9 lies 189 bp upstream of the transcription start point, mutagenesis of a proposed secondary binding site overlapping the trbBp -35 region had no effect on the ability of KorB to repress trbBp. Nevertheless, gel retardation analysis showed that KorB binding is promoted by sequences upstream and downstream of OB9 and that KorB can form higher order complexes on DNA. However, DNase I footprinting suggested that RNA polymerase may interact directly with KorB bound at OB9 and implied that contacts between these proteins could be responsible for the action of KorB at a distance.

Bacterial Proteins↗
PubMed1998

ST segment elevation and the prediction of hospital life-threatening complications: the role of right ventricular and posterior leads.

UNLABELLED: Accurate prognosis in suspected acute myocardial infarction (AMI) is essential for appropriate use of thrombolytic therapy and primary angioplasty. However, previous models may be limited because the 12-lead electrocardiogram (ECG) does not examine the right ventricular (RV) and posterior myocardium. We evaluated ST segment elevation (STSE) in posterior (V7-V9) and RV (V4R-V6R) leads to determine their predictive value for hospital life-threatening complications (HLTCs). METHOD AND RESULTS: This prospective trial of seven Midwestern hospital emergency departments (EDs) had inclusion criteria of age 35 years, chest pain suggestive of ischemia, and coronary care unit (CCU) admission. ECG leads were test positive if STSE was > 0.1 mV. Patients were positive for HLTCs if ED or inpatient hospital course included: ventricular fibrillation or tachycardia, second- or third-degree block, shock, arrest, or death. Univariate and multivariate analyses were performed to test each lead's association with HLTCs. Of 533 patients, 64.7% (345/533) had AMI and 15.8% (85/533) had HLTCs. The sensitivity of 18 leads for HLTCS was increased by 5.8%, but specificity decreased by 8.2%. ECG subgroups by STSE were associated with the following HLTC rates: inferior/+RV (32.4%); anterior (29.5%), lateral (23.1%), inferior RV (17.9%), and posterior (16.2%). V1 (odds = 3.2) and V6R (odds = 3.1) were statistically significant independent predictors. CONCLUSION: Posterior and RV leads did not increase the ECG's overall prognostic value, but in the presence of inferior STSE, were associated with low and high complication rates, respectively. Right and left precordial leads were the best predictors of HTLCs.

Adult↗
PubMed1998

Definition of the potentially fertile period from urinary steroid excretion rates. Part II. A threshold value for pregnanediol glucuronide as a marker for the end of the potentially fertile period in the human menstrual cycle.

Application of time series analysis to a database containing serial pregnanediol data from 113 complete ovulatory menstrual cycles contributed by 83 women of proven fertility and 68 cycles for which pregnanediol values were available over the ovulatory period, detected the first statistically significant risk in pregnanediol excretion for all cycles for which a baseline was available (n = 170). However, even at the 99% confidence level, for 22% of cycles a rise was observed before the presumed day of ovulation. Therefore, a threshold value for pregnanediol was sought from the database as a better marker for the end of fertility. A value of 1.4 mg per 24 h was not reached before day 2 after the pre-ovulatory estrogen peak day for 96% of the cycles. In the remaining 4% of cycles it was reached one day after the total estrogen peak day. The validity of this threshold was confirmed in extensive studies using the Ovarian Monitor where the equivalent is 6.3 mumol per 24 h of pregnanediol glucuronide and measurements are performed on timed urine specimens with a minimum collection time of three hours. These studies were as follows: 1) a World Health Organization study on the use of the Ovarian Monitor as a fertility self test in the home (108 cycles), 2) a multicenter study on returning fertility during breast feeding conducted by Family Health International (73 women), and 3) the general application of the Ovarian Monitor for pregnancy achievement and avoidance during the past ten years (over 250,000 PdG assays performed in ten countries). With rare exceptions, the use of these threshold values is applicable for all women provided correction is made for urine volume.

Biomarkers↗
PubMed1998

Evaluation of expanded polytetrafluoroethylene as a soft-tissue filling substance: an analysis of design-related implant behavior using the porcine skin model.

Soft-tissue augmentation using the synthetic nonfluid biomaterial expanded polytetrafluoroethylene (ePTFE) has been supported by number of recent reports citing the favorable characteristics of biocompatibility, soft and natural feel, ease of use, and permanent augmentation. Concern has been expressed about this application for ePTFE material because of the proximity of the implants to the skin surface and potential problems with infection and extrusion. We evaluated the behavior of a series of specific ePTFE implant designs using a long-term subcutaneous augmentation model. By using a porcine model, 466 implants of ePTFE in the form of strips, rolls, or tubes were placed using a percutaneous insertion device subcutaneously over the dorsum and face. The animals were divided into three study groups by length of implantation (3 weeks, control; 6 months, intermediate term; and 12 months, long-term) and en-bloc tissue specimens, including skin, implants, and underlying soft tissue, were harvested for gross and histologic examination. Implants were removed at the earliest sign of infection, exposure, or extrusion and the difficulty of removal was ascertained and recorded. These data reveal that ePTFE material elicits acceptable levels of tissue activity with low extrusion rates over the short and long term supporting its use for soft-tissue augmentation. The data show a clear difference, however, in the host response and behavior of the implants for this application based on shape or design. A statistically significant difference in the low, but measurable, extrusion rates was observed amongst these implant designs. ePTFE tubes showed greater stability and predictable augmentation over other implant designs for soft-tissue augmentation and seem to represent a substantial improvement for this application.

Animals↗
PubMed1998

The patient alert system--pilot study of built-in warning systems for pacemakers.

Malfunction of a pacing system can be life-threatening for a pacemaker-dependent patient. It would be desirable for implantable pulse generators to have a built-in automatic warning system capable of alerting the patient as soon as a potentially dangerous disorder is detected. In this study, seven patients (mean age, 72.6 +/- 10.7 years) with slow, chronic atrial fibrillation underwent implantation of a dual-chamber pulse generator with a custom-made "alert electrode" connected to the atrial port of the pulse generator to stimulate the underlying pectoral muscle. The muscle was temporarily stimulated while the pacemaker was in VVIR mode. The lowest amplitude sufficient to alert the patient (perception threshold) was 1.6 +/- 0.58 V at 0.45 ms during implantation and 1.2 +/- 0.5 V at 0.45 ms chronically. In a second phase, alerts outside of the office were issued using a special software routine capable of delivering stimuli at programmable date and time.

Aged↗
PubMed1997

Studies on the cytostatic and cytotoxic effects and mode of action of 8-nitro-7-hydroxycoumarin.

A derivative of coumarin, 8-nitro-7-hydroxycoumarin (8-NO2-7-OHC), was synthesised, purified and characterised. The cytostatic and cytotoxic nature of this compound was determined using both human and animal cell lines grown in vitro for 96 h in the presence of drug (0-500 microM, equivalent to 0-104 microg/ml). 8-NO2-7-OHC was shown to be cytotoxic to three cell lines, but cytostatic to all cell lines tested. With K562 and HL-60 cells, cell death was found to occur by apoptosis. This cytotoxic effect was found to be irreversible, with cell death continuing to occur following a 96 h recovery period. The cytostatic effects were found to be irreversible in four of the five cell lines tested. 8-NO2-7-OHC demonstrated its cytostatic effects within 24 or 48 h, while its cytotoxic effects appeared more gradually. The IC50 of 8-NO2-7-OHC was 475-880 microM, depending on the cell line tested. It was shown to exert its cytostatic effect through an alteration of cell cycle. It also inhibited DNA synthesis. The toxicity of 8-NO2-7-OHC does not appear to be mediated through the multi-drug resistance (MDR) protein since it caused significant cytostatic and cytotoxic effects to CHrC5 cells, which have an increased expression of this protein. This compound was shown to be non-mutagenic in a standard Ames test, both with or without a mammalian enzyme activation system. The applications and mode of actions of coumarins are discussed.

Animals↗
PubMed1997

Value of posterior and right ventricular leads in comparison to the standard 12-lead electrocardiogram in evaluation of ST-segment elevation in suspected acute myocardial infarction.

In this multicenter prospective trial, we studied posterior (V7 to V9) and right ventricular (V4R to V6R) leads to assess their accuracy compared with standard 12-lead electrocardiograms (ECGs) for the diagnosis of acute myocardial infarction (AMI). Patients aged >34 years with suspected AMI received posterior and right ventricular leads immediately after the initial 12-lead ECG. ST elevation of 0.1 mV in 2 leads was blindly determined and inter-rater reliability estimated. AMI was diagnosed by World Health Organization criteria. The diagnostic value of nonstandard leads was determined when 12-lead ST elevation was absent and present and multivariate stepwise regression analysis was also performed. Of 533 study patients, 64.7% (345 of 533) had AMI and 24.8% received thrombolytic therapy. Posterior and right ventricular leads increased sensitivity for AMI by 8.4% (p = 0.03) but decreased specificity by 7.0% (p = 0.06). The likelihood ratios of a positive test for 12, 12 + posterior, and 12 + right ventricular ECGs were 6.4, 5.6, and 4.5, respectively. Increased AMI rates (positive predictive values) were found when ST elevation was present on 6 nonstandard leads (69.1%), on 12 leads only (88.4%), and on both 6 and 12 leads (96.8%; p <0.001). Treatment rates with thrombolytic therapy increased in parallel with this electrocardiographic gradient. Logistic regression analysis showed that 4 leads were independently predictive of AMI (p <0.001): leads I, II, V3, V5R; V9 approached statistical significance (p = 0.055). The standard ECG is not optimal for detecting ST-segment elevation in AMI, but its accuracy is only modestly improved by the addition of posterior and right ventricular leads.

Aged↗
PubMed1997

Axial lower-limb alignment: comparison of knee geometry in normal volunteers and osteoarthritis patients.

Osteoarthritis of the knee is associated with deformities of the lower limb and malalignment of the limb segments. Pathogenetic relationships between the two are poorly understood. Alignment was studied by standardized radiography in 167 symptomatic Canadian osteoarthritis patients, and compared with 119 healthy adult volunteers. In healthy adults overall alignment (hip-knee-ankle angle) was principally determined by distal femoral valgus (condylar hip angle) and proximal tibial-plateau varus (plateau-ankle angle): the angle between the joint surfaces (condylar plateau) was relatively constant. In osteoarthritis, disease-associated differences included condylar-plateau angles that were divergent: accentuated medial convergence in varus osteoarthritis and lateral convergence in valgus osteoarthritis. This was interpreted as change arising from focal loss of cartilage in the medial (varus osteoarthritis) or lateral (valgus osteoarthritis) compartments of the knee. The changes would contribute to increasing limb malalignment during disease progression. But differences of limb geometry also contributed to malalignment. These were the average trends: in varus osteoarthritis there was abnormal femoral geometry (lesser femoral condylar valgus), but tibial surface geometry was the same. In valgus osteoarthritis, the opposite was true: abnormal tibial geometry (lesser plateau varus), but normal femoral geometry. A possible explanation is that these abnormal knee geometries pre-exist and predispose to osteoarthritis, although it is not impossible that they (like condylar-plateau angle) change as disease progresses. Further approaches to population studies are discussed based on these findings, along with their implications for knee surgery.

Adult↗
PubMed1996

The emergency department electrocardiogram and hospital complications in myocardial infarction patients.

OBJECTIVE: To determine whether acute myocardial infarction (AMI) patients who have negative ECGs on presentation have significantly lower complication rates than do those AMI patients who have positive ECGs on presentation. METHODS: Retrospective, cohort analysis comparing rates of hospital complications (ventricular fibrillation or tachycardia, shock, atrial arrhythmia or bradyarrhythmia with systolic blood pressure < or = 90 mm Hg, pulmonary edema) or interventions among patients with a final hospital diagnosis of AMI and an initially negative vs positive ECG. A negative ECG was normal or had nonspecific ST-segment and/or T-wave abnormalities (upright, flattened T waves; an isolated inverted T wave; ST depression < 0.1 mV; tall T waves with J-point elevation) or minor nonischemic abnormalities. Sample size was adequate to detect a 30% between-group difference in complication rates [alpha = 0.05, 1 - beta (power) = 0.80]. RESULTS: The 27 negative-ECG AMI patients differed from the 38 control patients in (mean +/- SD) age [57 +/- 12 vs 66 +/- 12 years, p < 0.01] but not in gender or history of AMI. The negative- and positive-ECG groups had similar rates of hospital complications [30% (95% CI: 13-47%) vs 42% (95% CI: 26-58%), p = 0.44] and intensive procedures [19% (95% CI: 4-34%) vs 29% (95% CI: 15-43%), p = 0.50], respectively. The negative-ECG patients with hospital complications had ECG evolution precede the event in 83% (95% CI: 69-97%) of cases; persistently negative-ECG patients had no complications [(95% CI: 0-33%), p = 0.06]. CONCLUSIONS: Negative- and positive-ECG AMI patients do not have moderate or large differences in the rates of in-hospital complications. Most negative-ECG patients who suffer complications evolve ECG changes prior to the event and such changes indicate the potential need for a higher level of care.

Adult↗
PubMed1995

Keto/enol epoxy steroids as HIV-1 Tat inhibitors: structure-activity relationships and pharmacophore localization.

Inhibition of the HIV-1 nuclear regulatory protein tat could potentially yield particularly useful drugs because it functions as an activator of transcription. It has no known cellular counterpart, and deletions in the tat gene destroy the ability of HIV-1 to replicate. We recently reported that a structurally unique class of tat inhibitors, 3-keto/enol 4,5-alpha-epoxy steroids bearing electron-withdrawing substituents at position 2, specifically inhibit tat-induced gene expression in virus free transfected SW480 cells. In this paper, we report on additional SAR (structure-activity relationships) for the steroid series and the localization of the pharmacophore to the A-ring functionality. There is a weak enantioselective preference for the natural steroid stereochemistry and hints of additional SAR in the electron-withdrawing group. Compound 34a is of particular interest in that it inhibits HIV replication in H9 cells at a concentration equivalent to its inhibitory level in the primary tat assay.

Cell Line↗
PubMed1995

Variation in orthopedic surgeons' perceptions of the indications for and outcomes of knee replacement.

OBJECTIVE: To determine the agreement among orthopedic surgeons' indications for knee replacement, their perceptions of the usefulness of various treatments for osteoarthritis of the knee and their expected outcomes of knee replacement, and to determine the relation between these opinions and the number of knee replacement procedures performed by individual surgeons. DESIGN: Survey. SETTING: Ontario. PARTICIPANTS: All 392 orthopedic surgeons in the province. Of the 325 practising traceable surgeons 234 (72.0%) responded. OUTCOME MEASURES: Indications for knee replacement, perceived usefulness of treatments for osteoarthritis, perceived outcomes of knee replacement and number of knee replacement procedures performed by individual surgeons. RESULTS: The respondents disagreed on how 20 of 34 patient characteristics affected their decision to perform knee replacement surgery. They also disagreed on the usefulness of seven of eight treatments for arthritis of the knee. The respondents demonstrated variation in their expected outcomes of knee replacement. The surgeons who performed more procedures judged, on average, the outcomes to be better and to have fewer complications than the surgeons who performed fewer procedures. CONCLUSIONS: Orthopedic surgeons demonstrated disagreement about some of the indications for knee replacement, the usefulness of treatments for arthritis of the knee and the perceived outcomes of knee replacement. The areas of greatest disagreement should be the focus of future research and the development of practice guidelines.

Adult↗
PubMed1995

Myocardial infarction with an initially normal electrocardiogram--angiographic findings.

To analyze the paradox of acute myocardial infarction (AMI) with an initially normal electrocardiogram (ECG), we reviewed the records of 732 patients discharged with a final diagnosis of AMI over a 2-year period. Twenty-one patient were identified whose initial ECG was normal and who underwent coronary arteriography during the index hospitalization. According to the ECG evolution, three distinct groups were identified: Group 1: those who subsequently developed ST elevation or Q waves (n = 7), Group 2: those who developed ST depression or T-wave inversion (n = 8), and Group 3: those whose ECG remained normal ( n = 6). Peak creatine kinase (CK), timing of the first ECG change, life-threatening complications, and location of the infarct-related coronary lesion were recorded. Infarct-related coronary lesions were also classified into those in a major coronary trunk versus those in secondary branches. The incidence of AMI with a normal ECG was 3.7%. There was no difference in the frequency of coronary artery involvement in the groups studied: left anterior descending (33%), right coronary artery (38%), and circumflex (28%). All ECG changes developed within the first 48 h of hospitalization; 17 +/- 15 in Group 1, and 24 +/- 12 h in Group 2. All six patients who had a persistently normal ECG (Group 3) had lesions in branch vessels (p < 0.05 when compared with Group 1 plus Group 2). Patients who developed ST elevation or Q waves (Group 1) always had a major artery trunk involved (p < 0.05 when compared with Group 2 plus Group 3). Patients in Group 3 had less myocardial damage and fewer complications compared with the other two groups. Myocardial infarction with an initial normal ECG is uncommon and may result from involvement of any of the three coronary arteries. Electrocardiographic evolution usually occurs within the first 48 h of hospitalization. Patients whose ECGs remain normal appear to have culprit lesions in coronary branches, smaller infarctions, and fewer in-hospital complications.

Coronary Angiography↗