Biomedical subjects
A Cameron
Publications and source records attributed to A Cameron.
Duplex ultrasonography of the fetal aorta, umbilical artery, and placental arcuate artery throughout normal human pregnancy.
A cross-sectional duplex study of blood flow in the fetal aorta, umbilical artery, and arcuate arteries of 111 normal subjects was performed once at between 20 and 42 weeks gestation. Peak systolic velocity, end-diastolic velocity, mean velocity, and volume flow were measured in the fetal aorta, and systolic to diastolic (S/D) ratios were measured in all three vessels. Velocities show an inverse exponential (Y = Exp [1/X x B + C]) increase with gestational age, reaching a plateau just before term, while S/D ratios in the aorta and umbilical arteries show a linear decrease. Such findings are at variance with some published data. Our results suggest a reduction in fetal placental resistance at term and provide useful data concerning normal fetal and placental circulations.
Prevalence and significance of atrial fibrillation in coronary artery disease (CASS Registry).
Estimates of the prevalence of atrial fibrillation (AF) in patients with coronary artery disease have varied from "frequent" to less than 2%. Data on 18,343 patients with angiographically demonstrated CAD in the Coronary Artery Surgery Study (CASS) registry were reviewed and AF was found to be present in 116 (0.6%) patients. The presence of AF was positively associated with the following clinical and angiographic variables: older age, sex (male), mitral regurgitation and functional impairment due to congestive heart failure. The number of diseased coronary arteries was negatively related to the presence of AF. Atrial fibrillation was an independent predictor of survival and its presence doubled the estimated risk over those patients without AF.
Chronic bundle branch block and use of temporary transvenous pacemakers during coronary arteriography.
A retrospective analysis of 217 consecutive patients with chronic bundle branch blocks undergoing cardiac catheterization was done to evaluate the need for temporary transvenous pacing during coronary arteriography. In patients without temporary right ventricular pacemakers (n = 185), only one episode of high-grade atrioventricular block occurred during coronary arteriography which required the urgent use of temporary pacing. All other bradyarrhythmias, including five episodes of transient asystole (greater than 3-sec pause) and four episodes of atrioventricular block (second degree or higher) were successfully managed without pacemaker utilization. Patients with prophylactic right ventricular pacemakers (n = 32) had a greater prevalence of ventricular fibrillation than those without pacing electrodes located in the right ventricle (2% vs. 9% respectively; P less than 0.05). These findings suggest that routing prophylactic pacemaker insertion during coronary arteriography in patients with chronic bundle branch block is not warranted and may place the patient at risk for developing iatrogenic ventricular arrhythmias.
Evaluation of fetal cardiac dysrhythmias with two-dimensional, M-mode, and pulsed Doppler ultrasonography.
Forty-three patients with fetal cardiac dysrhythmia were referred to a tertiary ultrasound department for further evaluation. The patients were subdivided according to the type of dysrhythmia diagnosed. All patients with irregular fetal heart rate had a good perinatal outcome. Of the six patients with fetal tachycardia, two required in utero therapy with maternal digoxin, and one of these fetuses had a cardiac tumor. The eleven patients with fetal bradycardia had the worst perinatal outcome, with four deaths occurring. The results suggest that all patients with fetal tachycardia or bradycardia should have a complete fetal cardiac assessment in a center experienced with the management of such cases.
Role of internal mammary artery in reoperations for coronary artery disease.
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Clinical implications of internal mammary artery bypass grafts: the Coronary Artery Surgery Study experience.
From the Coronary Artery Surgery Study Registry, all patients undergoing initial bypass surgery procedures with independent vein grafts were identified. The 950 patients receiving an internal mammary artery bypass graft were compared with the 6027 patients receiving vein graft alone. Improved survival rates with internal mammary artery grafts were noted at hospitals in which these grafts were performed infrequently as well as those in which the internal mammary artery graft was used frequently. The improved survival was noted in patients with normal (p = .004) as well as impaired (p = .004) ventricular function, in men (p = .0001) as well as women (p = .005), in patients over age 65 (p = .01) as well as younger patients (p less than .0001), and in those with (p = .05) or without (p less than .0001) critical stenosis of the left main coronary artery. The internal mammary artery bypass graft was an independent predictor of survival (p = .0004) and reduced the risk of dying by a factor of 0.64. It was concluded that the internal mammary artery graft is the bypass vessel of choice and should not be denied any subgroup.
Reoperation for coronary artery disease. 10 years of clinical follow-up.
From a 15-year follow-up study of 743 patients who underwent initial operation for coronary artery disease, 64 patients required reoperation for recurrence of angina and were followed-up for 15 years or less (mean, 6.2 years). Patients undergoing reoperation tended to be older but not significantly so (50.9 +/- 8.3 years vs. 57.5 +/- 9.7 years), had more left main coronary artery disease (p less than 0.001), and had more triple-vessel disease (p less than 0.001) than those undergoing the initial operation. There were no significant differences in sex, prior myocardial infarctions, or prevalence of abnormal ventriculograms between the two groups. The cumulative survival rate during a 10-year follow-up period after reoperation did not differ from the rate after the initial operations. There was less relief of angina in the first year after reoperation than after initial operation, but thereafter, the annual increases in recurrence of angina were similar. Although there were more myocardial infarctions after reoperation in the first 6 postoperative years, the cumulative incidence after 10 years did not differ between the two groups. We conclude that reoperation yields a similar survival benefit but produces less early relief of angina than initial operation.
Temporary pacemaker use during coronary arteriography.
The risk of life-threatening ventricular arrhythmias complicating coronary angiography is reportedly increased in patients in whom temporary righ ventricular pacemakers are used. Placement of the temporary pacing electrode in the right atrium or vena cava during angiography theoretically removes from the vulnerable ventricle a source of mechanically or electrically induced ventricular arrhythmias. This hypothesis was evaluated in 7,648 consecutive patients who underwent cardiac catheterization with selective coronary angiography, including 103 with life-threatening ventricular arrhythmic complications. The prevalence of ventricular arrhythmias was 6.4 times greater in patients with temporary pacemakers than in those without (7% vs 1.1%, respectively, p less than 0.001). Analysis of 369 cardiac catheterizations concurrently using temporary pacemakers revealed a greater than 4-fold decrease in the frequency of ventricular arrhythmias when the pacing electrodes were located in the right atrium or vena cava rather than the right ventricle (2% vs 9%, respectively, p less than 0.01). No significant difference in indications for temporary pacing could be distinguished between the groups based on location of the pacing electrode or occurrence of ventricular arrhythmias. These findings confirm that there is an increased risk of ionic contrast agent-induced ventricular arrhythmias in patients with chronic underlying conduction disturbances undergoing coronary angiography with concurrent right ventricular temporary pacemakers. This risk can be significantly decreased by placing the pacing electrode in the right atrium or vena cava.
Dinamap arm and thigh arterial pressure measurement.
Two automatic arterial pressure monitors (Model 1846 P) were used in 30 patients to measure arterial pressures and heart rates in the thigh and arm. Significant differences were found in thigh-arm systolic (p less than 0.001) and diastolic pressures (p less than 0.05). Arm pressures could be predicted from leg pressures and correction factors are suggested. Mean pressures in the thigh approximated more closely to the calculated mean pressures than in the arm. These differences were of little clinical importance.
Platelet studies in normal pregnancy and pregnancy-induced hypertension.
The platelet count does not appear to change during normal pregnancy but a rise in the mean platelet volume (MPV) and platelet distribution width was found in the third trimester in this study of 208 healthy pregnant women. Alteration of all three platelet parameters was seen following delivery in 40 women studied sequentially. Moderately severe pregnancy-induced hypertension (PIH) was associated with no alteration of platelet parameters when compared with gestation-matched controls. Platelet abnormalities in severe PIH appeared to be related to the time of presentation and may be a reflection of the rate of progression of the underlying condition.
Bypass surgery with the internal mammary artery graft: 15 year follow-up.
We performed a 15 year follow-up of 748 patients undergoing bypass surgery, comparing 532 patients with one or two internal mammary artery grafts with or without additional saphenous vein grafts to 216 patients with saphenous vein grafts alone. During the 15 years of follow-up the 532 patients with at least one internal mammary artery bypass graft had better cumulative survival (p less than .01), less early recurrence of angina (p less than .01), fewer myocardial infarctions (p less than .02), fewer reoperations (p less than .001), and better cumulative event-free survival (p less than .01) than the 216 patients with vein grafts alone. Patients who developed angina postoperatively had a better cumulative survival (p less than .01) in the presence of an internal mammary graft than with vein grafts alone. The 38 patients with double internal mammary grafts had the best survival rates, with lowest recurrence of angina and rate of late myocardial infarction and no need for reoperation. We conclude the internal mammary graft gives better protection against the clinical manifestations of coronary artery disease than does the saphenous vein graft.
Primary suture or T-tube drainage after choledochotomy.
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Health care data bases: the "top ten".
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At the scene of an RTA.
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The forensic pediatrician as a child advocate.
This paper focuses on the medicolegal activities of a group of six pediatricians from the Winnipeg Children's Hospital. Increasing legal demands resulted in 93 court appearances for the group, during a 12-month period ending in December 1982. The educational processes and the individual court room issues confronted by both the courts and the six pediatricians, dealing with problems of child protection, are described. Major pediatric roles and principles of advocacy resulting from these experiences are delineated. Society's accountability is discussed with specific reference to the pediatrician's role.
Increased risk of ventricular fibrillation associated with temporary pacemaker use during coronary arteriography.
Each injection of angiographic contrast dye during coronary arteriography represents a "natural experiment" in which the human ventricular fibrillation threshold is transiently reduced. Few factors, however, have been identified which favor the actual occurrence of ventricular fibrillation in this setting. Of 3906 consecutive patients undergoing selective coronary arteriography with sodium meglumine diatrizoate, 66 (1.7 percent) experienced dye-induced ventricular fibrillation, from which all were successfully defibrillated. Analysis of these cases revealed, unexpectedly, that patients in whom temporary right ventricular pacemakers were employed had an incidence of ventricular fibrillation nearly six times that found in the entire group undergoing arteriography (10 percent vs. 1.7 percent, respectively; P less than .001). Those individuals receiving pacemakers were distinguished from other studied patients only by a higher prevalence of conduction abnormalities. Although there is normally a low probability that mechanical stimulation by a pacing catheter can induce ventricular fibrillation, it is postulated that such an occurrence may be more likely after ventricular vulnerability has been increased by contrast dye.