PubMed Health⌕ Search

Biomedical subjects

A G Wallace

Publications and source records attributed to A G Wallace.

At least 19 recordsLinked to original sources
PubMed1990

Resource use and cost of initial coronary revascularization. Coronary angioplasty versus coronary bypass surgery.

Although there is intense interest in the cost-saving potential of therapeutic alternatives, most studies have analyzed hospital charges rather than actual economic costs. To analyze cost differences rigorously, we studied 115 patients undergoing initial elective angioplasty (percutaneous transluminal coronary angioplasty, PTCA) and 274 patients undergoing initial elective surgery (coronary artery bypass graft surgery, CABG). Detailed resource consumption profiles were constructed and used to estimate the cost savings from switching a patient from CABG to PTCA. Four cost-accounting methods were used in the analysis; each method made different assumptions about the costs that would vary and the costs that would be fixed according to the number of procedures performed. The variable costs in the four methods were the 1) cost of supplies, 2) cost of personnel and supplies, 3) average direct costs, and 4) average direct costs plus allocated hospital overhead. The mean hospital charges for CABG patients were $19,644 versus $9,556 for PTCA patients (p less than 0.0001). The estimated cost difference between CABG and PTCA was substantially less than the $10,088 difference in charges, however, with net savings of 19%, 46%, 53%, and 78% of charges using cost-accounting methods 1-4, respectively. Thus, although the initial hospital charges for PTCA are significantly less than for CABG, the actual economic cost savings may be significantly overestimated by the use of hospital charge data.

Accounting↗
PubMed1989

Effect of daily charge feedback on inpatient charges and physician knowledge and behavior.

Concurrent charge feedback has gained widespread acceptance as a method of minimizing hospitals' losses under the Medicare prospective payment system despite the fact that its effect on patient outcomes, physician behavior, or charges has not been studied in depth. In a controlled trial on two medical wards in an academic medical center, the effect of daily charge feedback on charges was studied. Sixty-eight house staff and 16 teaching attending physicians participated during a 35-week period, taking care of 1057 eligible patients. No significant differences in charges were seen when all patients were included. Since 45% of patients had planned protocol admissions (diagnostic workups or protocol treatment) on which the house staff had little change to impact, a subgroup analysis was performed, excluding these patients. In the remaining patients, a highly significant reduction in mean total charges (17%), length of stay (18%), room charges (18%), and diagnostic testing (20%) was found. In-hospital mortality and preventable readmission within 30 days were similar on the two wards. It was concluded that charge feedback alone is effective in a teaching hospital for decreasing charges.

Attitude of Health Personnel↗
PubMed1986

Career choices of 135 cardiology trainees at Duke University Medical Center from 1970 to 1984.

Alarm has been expressed at recently presented evidence showing that diminishing numbers of physicians are entering academic careers. The experience of the cardiology training program at a university medical center between 1970 and 1984 was reviewed to determine the career paths chosen by its trainees. During the study period, 135 physicians received training. Between 1970 and 1978 the percentage of trainees making academic medicine their initial career choice fluctuated considerably. Beginning in 1978, the percentage entering academic medicine steadily increased; in the most recent class, 8 of 9 trainees accepted academic faculty positions. Among 72 former trainees who joined an academic faculty after finishing training, approximately 7% per year left academic medicine for clinical practice. The median length of an academic career was 10 years. Individual institutions may be able to reverse the national trend of trainees making clinical practice their initial career choice. However, physicians who leave academic medicine for clinical practice may continue to deplete faculty ranks.

Academic Medical Centers↗
PubMed1980

The sock electrode array: a tool for determining global epicardial activation during unstable arrhythmias.

The conventional technique for mapping the sequence of epicardial activation uses a hand-held electrode moved over the heart to record from a number of epicardial sites one at a time, and requires 5-15 minutes to record from 50 or more sites distributed over the entire ventricular epicardium. This method is inadequate for arrhythmias that are transient or vary from beat to beat. To overcome these limitations the "sock electrode array," a contour-fitting sock containing 26 or 52 electrodes, has been developed. The nylon mesh sock is pulled over the heart and permits simultaneous recording of potentials from electrodes distributed over the entire ventricular epicardium. The electrograms are recorded and converted to digital form for computer generation of isochronous maps. Most of the epicardial activation sequence derived from the sock electrode were compared to those obtained by the hand-held electrode in six normal dogs during sinus rhythm and ventricular pacing. The sequence of local activation times acquired by both methods showed similar areas of early and late activation and comparable isochronous maps. The hand-held electrode technique required 10-15 minutes for data acquisition and another 15-30 minutes for analysis. The sock electrode array allowed electrograms from 26 epicardial electrodes to be recorded simultaneously during one cardiac cycle and computer generated isochronous maps could be displayed within 10 minutes. This method allows rapid recording and analysis of epicardial electrical phenomena and should meet the time constraints imposed during the intraoperative study of ventricular tachyarrhythmias in patients.

Animals↗
PubMed1979

Cholesterol metabolism in non-obese women--Failure of physical conditioning to alter levels of high density lipoprotein cholesterol.

The effects of a 6-week program of vigorous exercise were studied in 14 non-obese females aged 22--26. Preceding and following a regimen consisting of 30--45 min of jogging 5 days per week, treadmill performance, body weight, total plasma cholesterol, and plasma high density lipoprotein (HDL) cholesterol were assessed. Aerobic performance improved markedly after training as demonstrated by a reduced heart rate at each submaximal treadmill workload, and by an increase in maximal attainable workload. In the absence of a significant change in body weight, total cholesterol fell significantly after training (171 +/- 6 vs 161 +/- 5 mg/dl, P less than 0.05) whereas HDL cholesterol was not significantly altered (63 +/- 5 vs 58 +/- 3 mg/dl). The ratio of total cholesterol to HDL cholesterol fell insignificantly (2.92 +/- 0.19 vs 2.86 +/- 0.14). Our findings differ from prior reports of elevations of high density lipoprotein levels following physical conditioning in men. We suggest that hormonal or other factors leading to higher baseline levels of HDL in women counteract the expected alterations in lipoprotein metabolism induced by physical training.

Adult↗
PubMed1979

Transfer of coupling of premature ventricular contractions to an ectopic ventricular tachycardia: a mechanism for atypical bidirectional tachycardia.

Bidirectional tachycardia was observed on Holter tracings recorded from a dog three days after the production of a small freeze lesion on the wall of the left ventricle. A bigeminal rhythm with fixed coupling of ventricular premature contractions was interrupted by a burst of ventricular tachycardia of different morphology. The ventricular premature contractions, originally coupled to the sinus beats, became coupled to the new ventricular tachycardia with an identical coupling interval. This resulted in a dibirectional tachycardia, created by the "transfer" of coupling of premature ventricular contractions to a separate ectopic ventricular tachycardia.

Animals↗
PubMed1979

Electrophysiologic effects of disopyramide phosphate on sinus node function in patients with sinus node dysfunction.

The electrophysiologic effects of intravenously administered disopyramide (2 mg/kg) on three parameters of sinus node function were examined in 16 symptomatic patients with sinus node dysfunction. Based on their ECG data before study, patients were subdivided into group A (n = 8), those with sinus pauses and/or sinoatrial (SA) exit block; and group B (n = 8), those with sinus bradycardia. Disopyramide shortened spontaneous cycle length in 10 of 16 patients and lengthened it in six--markedly so (91%) in one patient. Estimated SA conduction time decreased in seven of 14 patients and increased in seven. Two patients developed second degree SA exit block after disopyramide. Maximum sinus node recovery time was prolonged by disopyramide in 11 of 16 patients and markedly so in four. For the group as a whole there was no significant difference in spontaneous cycle length, maximum sinus node recovery time or estimated SA conduction time. P-wave and QRS durations and H-V intervals were significantly lengthened by disopyramide. Marked depression of the three parameters of sinus node function occurred in three group A patients and in one group B patient who had persistent severe sinus bradycardia. These four patients also had secondary pauses after termination of rapid atrial pacing under control conditions. Disopyramide should be administered cautiously to patients with sinus node dysfunction, particularly those with sinus pauses, SA exit block or secondary pauses.

Adult↗
PubMed1979

Reaction of the myocardium to cryosurgery: electrophysiology and arrhythmogenic potential.

The acute and chronic electrophysiological effects of a cryolesion produced in the left ventricle were studied in six dogs. All dogs had frequent ventricular premature beats (VPB) and five of six dogs had ventricular tachycardia during the first 4 days after the cryolesion; only one of the six dogs continued to have VPBs after 1 week, and this dog had identical VPBs before the creation of the cryolesion. Neither control dog had VPBs. Two additional dogs underwent epicardial and transmural mapping studies immediately after production of a cryolesion. VPBs in these animals were shown to originate at the border of the cryolesion. Epicardial activation sequence during normal sinus rhythm was not altered by the chronic cryolesion. The border zone of the chronic cryolesion was sharply demarcated with normal potentials recorded outside of the lesion and "extrinsic" potentials recorded within.

Animals↗
PubMed1979

Reentry within the atrioventricular node: surgical cure with preservation of atrioventricular conduction.

Paroxysmal supraventricular tachycardia (PSVT) is commonly caused by reentry within the atrioventricular (AV) node. This arrhythmia was abolished by operative dissection of the AV junction in a patient with disabling tachycardia that was not controlled by drugs. The operation was intended to create complete AV block, but AV conduction persisted after surgery. An electrophysiologic study 1 year after the operation revealed that the operation changed AV conduction in both the antegrade and retrograde directions, which may explain the absence of tachycardia. The patient has been free of arrhythmias for 18 months.

Atrioventricular Node↗
PubMed1979

Epicardial mapping of the onset of ventricular tachycardia initiated by programmed stimulation in the canine heart with chronic infarction.

The initial beats of ventricular tachycardia (VT) induced by programmed stimulation (PS) of the heart have frequently been observed to differ in QRS configuration from the subsequent uniform QRS complexes of tachycardia. The transient nature of these initial beats has made their study difficult during epicardial mapping with conventional, hand-held recording electrodes. Twenty-four dogs were studied with PS 1-10 months after coronary ligation. Twenty-six epicardial electrograms were recorded simultaneously during PS. The data were digitized for computer generation of isochronic maps for any desired beat. Three patterns of initiation were observed in episodes of tachycardia in which the initial beats differed from the subsequent beats of VT (11 of 18 runs of VT). Most frequently, the initial beats of VT originated near the pacing electrode before moving to a stable infarction zone location. Less frequently, the initial beats were due to transient reentry in the bundle branches or a transient shifting of early breakthrough sites in the infarction zone.

Animals↗
PubMed1979

An analysis of the effects of acetylcholine on conduction and refractoriness in the rabbit sinus node.

The effects of acetylcholine (ACh) on sinus node automaticity, atrio-sinus conduction, and refractoriness were studied in 41 isolated rabbit right atrial preparations. Average control rate was 126 beats/min, and ACh 5 x 10(-8) M, 5 x 10(-7) M, and 5 x 10(-6) M significantly decreased heart rate by 7, 15, and 43%, respectively (P less than 0.01, 0.001, and 0.001). Atrio-sinus conduction time at a pacing cycle length of 400 msec did not significantly change during exposure to ACh 5 x 10(-8) and 5 x 10(-7) M. However, the mean effective refractory period (ERP) of the sinus node, at a pacing cycle length of 400 msec, increased from 183 +/- 16 msec to 210 +/- 24 msec during exposure to ACh 5 x 10(-7) M (P less than 0.025). The change in ERP followed the change in action potential duration. In contrast to the lack of effect of ACh 5 x 10(-7) M on atrio-sinus conduction time, ACh 5 x 10(-6) M caused 2:1 atrio-sinus block in 8 of 10 experiments. The site of block was identified using multiple microelectrode impalements, and occurred between the perinodal fibers bordering on the edge of the sinus node and the pacemaker area in the sinus node proper. When the pacing cycle length was increased and 1:1 atrio-sinus conduciton was present, conduction time did not significantly differ from control. At this longer pacing cycle length the mean ERP of the sinus node was 380 msec greater than control and lasted well after repolarization was completed. Thus, atrio-sinus block during exposure to ACh 5 x 10(-6) M resulted from a marked prolongation of refractoriness.

Acetylcholine↗
PubMed1979

Sinus node disease.

Sinus node dysfunction may be clinically asymptomatic or may lead to serious arrhythmias and sudden death. Symptomatology relates to the resulting brady- or tachyarrhythmias. Clinical and electrocardiographic assessements fail to identify the cause in many patients. Ambulatory electrocardiography establishes the diagnosis in a greater percentage of patients and permits the direct correlation of symptoms with rhythm disturbances. Functional electrophysiologic testing which examines the sinus node response to constant atrial pacing and premature atrial stimulation may be performed for further evaluation of these patients. Sensitivity and specificity of sinus node recovery times (SNRT) and sino- atrial conduction time (SACT) derived by functional testing vary markedly in different reports. This variation may relate to differences in patient population, limitations of testing procedures, and the uncertainties as to the normal limits of SNRT and SACT. As a result, the full value of these tests in diagnosis and in furthering our understanding of sinus node disease remains to be established. At present, permanent pacing remains the definitive treatment in symptomatic patients.

Animals↗