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Biomedical subjects

A S Most

Publications and source records attributed to A S Most.

At least 19 recordsLinked to original sources
PubMed1998

Economic effects of community versus hospital-based faculty pneumonia care.

To compare the length of stay and charges for patients with pneumonia admitted in 1995 to the teaching and nonteaching services of a Northeastern teaching hospital, we reviewed the charts of 237 patients. Patients cared for by hospital-based generalists working with housestaff (teaching service) were discharged more quickly and with lower or equivalent charges than patients cared for by community-based attending physicians working either with housestaff (private teaching service) or alone (nonteaching service). Academic teaching services staffed by general medicine faculty may provide efficient inpatient pneumonia care.

Adult↗
PubMed1997

Presence of a critical coronary artery stenosis does not abolish the protective effect of ischemic preconditioning.

BACKGROUND: Episodic, severe coronary artery flow restriction preconditions the myocardium much like brief occlusions. The necessity for full reperfusion after a preconditioning intervention to elicit the preconditioning response is unclear. This study investigated in closed-chest swine the effect of a persistent critical coronary stenosis with moderate flow reduction on ischemic preconditioning. METHODS AND RESULTS: Farm pigs (n = 23) assigned to one of four groups--(1) control, (2) stenosis, (3) preconditioned (PC), or (4) preconditioned plus stenosis (PC/S)--underwent percutaneous instrumentation with a percutaneous transluminal coronary angioplasty catheter advanced to the mid-left anterior descending coronary artery. An artificial coronary stenosis (82% diameter reduction) was mounted on the catheter just proximal to the balloon in the two stenosis groups. Preconditioning stimulus consisted of two 10-minute balloon occlusions followed by 15 minutes of reperfusion. All groups subsequently underwent 45 minutes of occlusion followed by 120 minutes of reperfusion. Baseline regional myocardial blood flow in the area at risk (AAR), measured with colored microspheres, was lowest in the stenosis groups, with flow expressed as a percentage of normal zone flow. Infarct size (percent of AAR), determined by staining slices of the heart with triphenyltetrazolium, was significantly reduced in PC compared with control pigs (15.1 +/- 5.9% versus 66.8 +/- 6.4%, respectively; P < .001). Infarct size in PC/S pigs was also significantly reduced (29.7 +/- 7.1%, P = .004 versus control) but was not different in degree from PC pigs (P = .6). The stenosis by itself conferred no preconditioning benefit (percent of AAR = 69.0 +/- 5.4%). CONCLUSIONS: A moderate flow-limiting stenosis did not prevent preconditioning but may have attenuated the effect. This may be analogous to the clinical scenario in which intermittent coronary occlusion and reperfusion superimposed on a critical stenosis precede a prolonged occlusion treated with thrombolysis.

Analysis of Variance↗
PubMed1991

Unsuccessful emergency medical resuscitation--are continued efforts in the emergency department justified?

BACKGROUND: The majority of attempts to resuscitate victims of prehospital cardiopulmonary arrest are unsuccessful, and patients are frequently transported to the emergency department for further resuscitation efforts. We evaluated the efficacy and costs of continued hospital resuscitation for patients in whom resuscitation efforts outside the hospital have failed. METHODS: We reviewed the records of 185 patients presenting to our emergency department after an initially unsuccessful, but ongoing, resuscitation for a prehospital arrest (cardiac, respiratory, or both) by an emergency medical team. Prehospital and hospital characteristics of treatment for the arrest were identified, and the patients' outcomes in the emergency room were ascertained. The hospital course and the hospital costs for the patients who were revived were determined. RESULTS: Over a 19-month period, only 16 of the 185 patients (9 percent) were successfully resuscitated in the emergency department and admitted to the hospital. A shorter duration of prehospital resuscitation was the only characteristic of the resuscitation associated with an improved outcome in the emergency department. No patient survived until hospital discharge, and all but one were comatose throughout hospitalization. The mean stay in the hospital was 12.6 days (range, 1 to 132), with an average of 2.3 days (range, 1 to 11) in an intensive care unit. The total hospital cost for the 16 patients admitted was $180,908 (range per patient, $1,984 to $95,144). CONCLUSIONS: In general, continued resuscitation efforts in the emergency department for victims of cardiopulmonary arrest in whom prehospital resuscitation has failed are not worthwhile, and they consume precious institutional and economic resources without gain.

Cardiopulmonary Resuscitation↗
PubMed1989

Tissue acidosis: role in sustained arteriolar dilatation distal to a coronary stenosis.

This study tested the hypothesis that myocardial tissue acidosis is responsible for maintenance of reduced arteriolar tone distal to a severe coronary arterial stenosis. Domestic swine (n = 10) were instrumented with a coronary arterial stenosis that reduced vessel diameter 80%. Measurements of hemodynamic indexes were made 1) before stenosis, 2) at 5, 20, and 60 minutes after stenosis placement, and 3) after each of three, 20-minute NaOH infusions (0.05 M, 0.1 M, and 0.5 M) distal to the stenosis (group 1). Intracellular pH at the end of 30 minutes of 0.5 M NaOH infusion distal to the stenosis was measured in a second group (n = 6) of swine (group 2). After stenosis placement in group 1, endocardial blood flow declined significantly, and evidence of regional acidosis (increased coronary venous Pco2 and decreased coronary venous pH) and ischemia (lactate production) developed. One hour later, evidence of acidosis persisted, though to a lesser extent. Myocardial oxygen and lactate metabolism exhibited similar patterns. Infusion of 0.5 M NaOH (0.38 ml/min) reduced (p less than 0.01) distal zone epicardial blood flow but did not change endocardial flow. Regional myocardial oxygen extraction (75 +/- 8%, mean +/- SD) and consumption (8.2 +/- 2.3 ml/min/100 g) also declined significantly (p less than 0.01) in response to 0.5 M NaOH infusion compared with 60 minutes after stenosis (86 +/- 4 and 12.4 +/- 2.8 ml/min/100 g respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1989

Details of coronary stenosis morphology influence its hemodynamic severity and distal flow reserve.

Differences in coronary flow reserve with anatomically similar coronary artery stenoses have been attributed to 1) nonstandard physiologic conditions, 2) inadequacies of measurements of coronary artery stenosis dimension and/or coronary blood flow, and 3) inadequate hyperemic stimulus. Our study tested the hypothesis that details of coronary artery stenosis geometry, which may or may not be apparent on coronary angiograms, also may contribute importantly to such differences. A simple and complex coronary artery stenosis, each of which reduced vessel cross-sectional area by 84%, was introduced in random order into the left anterior descending coronary artery of nine closed-chest, sedated swine. The simple stenosis had a single lumen while the complex stenosis had five small lumena whose combined area equaled that of the single lumen stenosis. Measurements of hemodynamics and regional myocardial blood flow (microspheres) were made at control and after 10 minutes of adenosine infused at 400 micrograms/min and then at 800 micrograms/min distal to each stenosis. Both heart rate and aortic mean pressure were controlled and thus did not change versus initial baseline (129 +/- 4 minutes and 120 +/- 10 mm Hg, mean +/- SD, respectively) during the study. Baseline total flow (ml/sec) distal to the stenosis was similar at each control (1.05 +/- 0.35 vs. 0.92 +/- 0.34, simple versus complex, respectively; p = NS). At maximal adenosine, total flow with the simple stenosis was 3.44 +/- 0.92 versus 2.77 +/- 0.51 for complex (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Coronary angioplasty for patients with multivessel coronary artery disease: follow-up clinical status.

To determine the value of percutaneous transluminal coronary angioplasty (PTCA) for patients with multivessel coronary artery disease, we reviewed follow-up data of 92 consecutive multivessel disease patients in whom PCTA had been successful and in whom at least 6 months had elapsed. Clinical outcome of multivessel disease patients was compared to that of 189 patients with single-vessel disease who experienced successful PTCA. Eighty percent of multivessel disease patients noted clinical improvement at follow-up. More single-vessel disease patients, however, were free of angina (77% vs 63%, p = 0.02), were not taking long-acting antianginal medicationS (46% vs 27%, p less than 0.001), and had repeat PTCA less often (5% vs 12%, p = 0.05) than multivessel disease patients. The incidence of late clinical events such as myocardial infarction, coronary artery bypass surgery, and death was low in both single- and multivessel disease patients. To determine whether the degree of revascularization achieved accounted for differences between single- and multivessel disease outcome, PTCA for multivessel disease was classified as either complete or incomplete revascularization. Those patients classified as having incomplete revascularization, although they had multivessel coronary artery disease, had only one significant ischemic zone and this was successfully revascularized by PTCA. There was no significant difference in anginal status or incidence of myocardial infarction, coronary artery bypass surgery, or death between the two multivessel disease subgroups. Thus, PTCA is of clinical value for selected patients with multivessel coronary artery disease, even in those who are incompletely revascularized by design.

Adult↗
PubMed1988

Objective assessment of coronary angioplasty for multivessel disease: results of exercise stress testing.

The efficacy of coronary angioplasty in multivessel coronary artery disease was evaluated in a series of 145 consecutive patients in whom angioplasty had been successful and in whom a follow-up exercise stress test was performed within 2 months. Exercise stress test results of these patients with multivessel disease were compared with those of 177 patients with single vessel disease after successful coronary angioplasty. The postangioplasty exercise test showed ischemia in 13% of patients with single vessel and 29% of those with multivessel disease, although only 7 and 13%, respectively, experienced angina. The mean exercise duration was comparable for patients with multivessel disease (453 +/- 174 s) and single vessel disease (476 +/- 166 s). To assess the impact of the degree of revascularization in patients with multivessel disease on the results of exercise testing, 48 patients with completely revascularized vessels and 97 with incompletely revascularized vessels were evaluated. The mean exercise duration (459 +/- 178 versus 450 +/- 173 s), mean maximal heart rate (132 +/- 31 versus 136 +/- 25 beats/min) and mean systolic blood pressure (174 +/- 25 versus 170 +/- 26 mm Hg) were similar in completely and incompletely revascularized groups. Exercise-induced angina occurred in 13% of both groups. Ischemic ST segments were more common in the incompletely revascularized group (34 versus 19%, p = 0.06). Thus, exercise stress testing provides evidence that successful angioplasty can relieve electrocardiographic manifestations of ischemia as well as anginal symptoms in the majority of patients with either single or multivessel coronary artery disease who are suitable candidates for the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Role of endogenous prostacyclin in myocardial blood flow regulation distal to a severe coronary stenosis.

To test the hypothesis that endogenous prostacyclin is required to maintain reduced arteriolar tone distal to a severe coronary arterial stenosis under basal conditions and during challenge with a vasoconstrictor eicosanoid such as thromboxane A2 10 closed chest, domestic swine were prepared with an artificial stenosis, which reduced the luminal diameter of the left anterior descending coronary artery by 80%. Haemodynamic variables, regional myocardial blood flow (microsphere method), and lactate metabolism were measured at control (1); after infusion of U46619 (thromboxane A2 mimetic) distal to the stenosis at 1 microgram.min-1 for 10 min and 5 micrograms.min-1 for 10 min; at control (2); after indomethacin infusion distal to the stenosis; and after repeat infusion of U46619. At the end of the study the animal hearts were removed and their coronary vessels harvested for in vitro determination of prostacyclin (PGI2) production. Regional myocardial blood flow in all layers of the heart distal to the stenosis did not change compared with control during the initial 1 microgram.min-1 dose of U46619 but was reduced significantly after the 5 micrograms.min-1 dose (approximately 20% vs control). Distal zone flow (all layers) returned to baseline at control (2) and remained unchanged after indomethacin infusion. Although distal zone flows were reduced significantly in response to the second 5 micrograms.min-1 dose, the reduction in each layer after indomethacin was comparable to that observed with the 5 micrograms.min-1 dose before indomethacin infusion. Finally, the in vitro production of PGI2 by coronary vessels was considerably impaired by indomethacin infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1988

Effect of pressure-controlled intermittent coronary sinus occlusion on pacing-induced myocardial ischemia in domestic swine.

This study tested the hypothesis that pressure-controlled intermittent coronary sinus occlusion (PICSO) would be useful in ameliorating myocardial ischemia under conditions characterized by preserved, but reduced (relative to demand), myocardial blood flow. Studies were conducted in closed-chest, sedated domestic swine prepared with an artificial stenosis that reduced luminal diameter of the animal's left anterior descending coronary artery by 80%. Measurements of hemodynamics, regional myocardial blood flow, and oxygen, lactate, and nucleoside metabolism were obtained in 10 animals (1) before placement of stenosis, (2) 30 min after insertion of stenosis, (3) after 30 and 60 min of PICSO, and (4) 30 min after discontinuation of PICSO. Two groups of control animals were studied to observe the natural history of metabolic markers of ischemia. Control group I consisted of four animals studied concurrently and subjected to the same protocol except for the fact that PICSO was not applied. Control group II consisted of eight additional animals studied as a group. A specially designed balloon-tipped catheter positioned in the proximal portion of the animal's great cardiac vein was used to provide PICSO. Heart rate was controlled by atrial pacing (rate, 145 beats/min) through the study. After placement of the stenosis, flow in endocardial and transmural layers distal to the stenosis declined significantly (p less than .01) vs control. Application of PICSO failed to increase arterial inflow distal to the stenosis in any myocardial layer. Myocardial aerobic metabolism was adversely affected by stenosis and changed from consumption of lactate, inosine, and hypoxanthine before stenosis to production at 30 min after stenosis. Although PICSO was associated with reduced production and a return toward consumption of lactate, inosine, and hypoxanthine, a similar pattern of changes in lactate, inosine, and hypoxanthine metabolism was observed in control animals over a comparable period of time. In addition, regional myocardial oxygen extraction and consumption were not changed vs poststenosis levels by PICSO. However, in comparison with controls, PICSO did accelerate the rate of resolution of myocardial ischemia as assessed by lactate metabolism. At 30 min of PICSO (or sham) the change vs poststenosis was +33.6 +/- 25.0 mumol/min/100 g in the PICSO but only +6.7 +/- 29.7 in the control group (p = .05). We conclude, therefore, that even though PICSO did not alter the final level of myocardial ischemia under conditions modeled in this study it did accelerate its rate of resolution, an effect that may be beneficial clinically.

Animals↗
PubMed1988

Metabolic response to prolonged reduction of myocardial blood flow distal to a severe coronary artery stenosis.

Limited data are available concerning the effects of mild-to-moderate, sustained reductions of coronary blood flow on myocardial aerobic metabolism. This study tested the hypothesis that a sustained flow reduction distal to a severe coronary artery stenosis may be well tolerated (after the initial insult is passed) because of gradual improvement in the balance between myocardial oxygen supply and demand. Studies were performed in eight sedated, closed-chest domestic swine that were instrumented with an artificial coronary arterial stenosis (80% diameter reduction). Hemodynamics, regional myocardial blood flow and oxygen, lactate, acid, and base metabolism were measured before stenosis and at 5, 20, 60, 120, and 180 minutes after stenosis insertion. Regional myocardial function (ultrasonic length sensors) was measured serially during 2 hours in three additional swine. After stenosis placement, endocardial and transmural flows declined (p less than 0.05) compared with flows before stenosis (from 1.54 +/- 0.37 to 0.73 +/- 0.24 ml/min/g [mean +/- SD] and from 1.44 +/- 0.31 to 1.19 +/- 0.25 ml/min/g, respectively). Thereafter, flows remained unchanged for the duration of the study. Similarly, prestenosis heart rate (135 +/- 7 beats/min), aortic mean pressure (113 +/- 17 mm Hg), and tension time index (27.1 +/- 3.6 mm Hg.sec) remained constant for the duration of the study. In contrast, regional coronary venous pH declined (p less than 0.05) compared with prestenosis levels (7.35 +/- 0.02) 5 minutes after stenosis (7.28 +/- 0.04), but it returned to prestenosis levels during the next hour. Regional coronary venous PCO2 exhibited a similar pattern (i.e., acute increase during poststenosis with gradual return to prestenosis levels).(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1988

Influence of serotonin on myocardial blood flow in the presence and absence of a coronary arterial stenosis: observations in domestic swine.

This study tested the hypothesis that 5-HT may impair coronary flow regulation by inappropriately increasing arteriolar tone in the coronary circulation. Ten closed chest, domestic swine were studied both in the presence and in the absence of a severe artificial intraluminal coronary stenosis. A 5-French micromanometer catheter with fluid lumen was placed in the left anterior descending coronary artery and used to record pressure and infuse 5-HT (40 and 100 micrograms/min) into the coronary circulation. For the stenosis phase of the protocol the catheter was embedded in the artificial stenosis. Hemodynamics, regional myocardial blood flow (microsphere technique), coronary vascular resistance, lactate consumption, and oxygen metabolism were measured at control and at 5 min of each 5-HT dose. In the absence of coronary artery stenosis (i.e., full vasodilatory reserve), there was no change in regional myocardial blood flow or coronary vascular resistance during 5-HT infusion. In the presence of a severe coronary stenosis (i.e., limited vasodilator reserve) 5-HT produced a significant (P less than 0.05) decrease versus control in the distal left anterior descending: circumflex zone endocardial blood flow ratio (0.63 +/- 0.19, mean +/- 1 SD, to 0.55 +/- 0.15) and a significant (P less than 0.05) increase versus control in endocardial (50.6 +/- 16.6 to 61.2 +/- 19.8 mm Hg/ml/min/g) and transmural (49.9 +/- 9.5 to 57.2 +/- 12.8) coronary vascular resistance. Thus, 5-HT does not impair coronary flow regulation when full vasodilatory reserve is present. When coronary vasodilatory reserve is impaired by the presence of a severe proximal stenosis, 5-HT causes modest impairment of endocardial flow regulation.

Animals↗
PubMed1987

Angiographic findings when chest pain recurs after successful percutaneous transluminal coronary angioplasty.

Angiographic and clinical characteristics of 102 consecutive patients who underwent coronary cineangiography for assessment of recurrent angina pectoris after successful percutaneous transluminal coronary angioplasty (PTCA) were reviewed. Based on angiographic findings, patients were classified as having restenosis (n = 63), development of new, significant coronary stenosis (n = 15), incomplete revascularization (n = 9) or no significant coronary artery disease (n = 15). Eighteen clinical and technical characteristics of the study group were analyzed as predictors of angiographic outcome. The groups did not differ in terms of age, gender, number of inflations performed, peak inflation pressure or in the pre- or post-PTCA stenosis or gradient. The time from PTCA to onset of recurrent angina was the most powerful predictor of angiographic outcome. Patients in whom symptoms developed within 1 month of PTCA usually had incomplete revascularization or no coronary narrowing. Restenosis was the most common explanation for chest pain 1 to 6 months after PTCA. Angina recurring more than 6 months after PTCA was usually due to development of new, significant coronary artery narrowings.

Angina Pectoris↗
PubMed1987

Assessment of coronary flow reserve using digital angiography before and after successful percutaneous transluminal coronary angioplasty.

Important alterations of coronary blood flow and coronary flow reserve occur during percutaneous transluminal coronary angioplasty (PTCA). This study evaluated these alterations using digital subtraction angiography. Coronary flow reserve was determined before and after successful PTCA in 20 patients with 1-vessel coronary artery disease (CAD). Ten other patients with angiographically normal coronary arteries, normal exercise electrocardiographic responses and normal cardiac structure also were evaluated. Coronary flow reserve was calculated as the ratio of papavarine-induced hyperemic flow to basal flow. Flow reserve for the stenotic artery in patients who underwent PTCA was 1.6 +/- 0.2 (mean +/- standard error of the mean) (range 0.9 to 3.9, n = 20). After successful PTCA, flow reserve for this artery increased to 3.1 +/- 0.2 (range 1.7 to 5.2, n = 20) (p less than 0.0001 vs before PTCA). Flow reserve for adjacent nonstenotic, nondilated arteries was 2.6 +/- 0.2 (range 1.4 to 4.5, n = 13). Coronary flow reserve in the stenotic arteries before PTCA was far below normal. In addition, both successfully dilated arteries and nondilated, nonstenotic arteries in these patients with CAD had flow reserve values smaller than those in the patients with normal arteries (4.8 +/- 0.6, range 2.3 to 12.6, n =22) (p less than 0.01). These findings suggest that digital angiographic determinations of coronary flow reserve can reveal important alterations of individual artery vasodilatory capacity. The data suggest that although an epicardial coronary in a patient with CAD may appear angiographically normal, flow reserve remains impaired due to abnormalities as yet undefined.

Adult↗
PubMed1987

Thrombolytic therapy for prosthetic cardiac valve thrombosis.

To determine the efficacy and safety of thrombolytic therapy for prosthetic valve thrombosis, a composite series of 41 patients who received either streptokinase or urokinase intravenously for this disorder were analyzed. The series comprised 3 patients treated at Rhode Island Hospital and 38 previously reported on. Short-term success was achieved in 32 patients (78%). Prosthetic valve thrombosis recurred in seven (22%) of the successfully treated patients, four of whom were retreated with thrombolytic therapy. A favorable clinical outcome was observed in each. Fever and venipuncture bleeding were the most frequent side effects. Systemic embolization occurred in 4 (15%) of 26 patients with either aortic or mitral prosthetic valve thrombosis. None of these latter patients experienced a permanent neurologic or circulatory deficit. It is concluded that thrombolytic therapy is of value in the treatment of prosthetic valve thrombosis.

Adult↗
PubMed1987

Role of adenosine in mediating the coronary vasodilative response to acute hypoxia.

To test the hypothesis that adenosine is required to mediate the coronary vasodilative response to acute hypoxia haemodynamic indices, regional myocardial blood flow, and oxygen and lactate metabolism were measured in nine closed chest anaesthetised domestic swine at control, after 3-5 min of 100% nitrogen inhalation, at second control, and after 3-5 min of 100% nitrogen inhalation plus adenosine deaminase infusion in the left anterior descending coronary artery. Cardiac lymph adenosine deaminase concentration was also measured in a separate group of four animals previously reported on. Heart rate was held constant by atrial pacing during the study. Aortic mean pressure did not change. Changes in arterial and anterior interventricular vein pH, PO2, PCO2, and oxygen content were similar for each intervention. Transmural left anterior descending artery zone flow increased significantly (p less than 0.01) compared with control (1.22(0.23) ml.min-1.g-1; mean(SD)) in response to hypoxia (2.73(0.92)). Intracoronary adenosine deaminase infusion (167 nmol.s-1), however, failed to blunt the flow response to hypoxia (1.33(0.30) to 2.79(1.32); second control to hypoxia plus adenosine deaminase respectively, p less than 0.01). Mean adenosine deaminase activity (nmol.s-1) in cardiac lymph was 105(85) at the end of 10 min of intracoronary infusion (167 nmol.s-1) and 203 (148) nmol.s-1 at the end of 15 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗