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Biomedical subjects

T Feldman

Publications and source records attributed to T Feldman.

At least 19 recordsLinked to original sources
PubMed1992

ST segment alternans during coronary angioplasty.

Four patients with severe proximal or mid-LAD stenosis were noted to have ST alternans during balloon angioplasty. Neither mechanical alternans nor increased ventricular ectopy were noted. In contrast to prior descriptions in animals or patients with variant angina, ST alternans did not occur following a premature ventricular contraction. Frequent use of calcium channel blockers during PTCA may interfere with the mechanism leading to electrical alternans and its consequences as seen in animal studies, accounting for the low frequency with which this phenomenon is noted during PTCA.

Adult↗
PubMed1992

Plasma lipoprotein (a) protein concentration and coronary artery disease in black patients compared with white patients.

PURPOSE: This study examines the relation between lipoprotein (a) protein levels and other lipid parameters and coronary artery disease in white and black patients. PATIENTS AND METHODS: Plasma lipoprotein (a) protein levels were measured prior to coronary angiography in a population of 127 white and 111 black patients. Each angiogram was given a total coronary artery disease score based on the number and severity of atherosclerotic coronary lesions. RESULTS: White and black patients exhibited no differences in total plasma cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides. Black patients had higher lipoprotein (a) protein levels than white patients (8.6 versus 4.0 mg/dL; p < 0.0001). The extent and severity of coronary artery disease was the same in white and black patients. White and black patients with coronary artery disease had higher lipoprotein (a) levels than patients without coronary lesions (4.37 versus 1.99 mg/dL, p = 0.027 for white; 9.23 versus 6.87 mg/dL, p = 0.072 for black). In both groups of patients, there was a weak but significant positive correlation between lipoprotein (a) protein levels and coronary artery disease score. CONCLUSION: Lipoprotein (a) is higher in patients with coronary artery disease. Black patients have higher plasma lipoprotein (a) protein levels than white patients and a comparable degree of coronary artery disease. It follows that the cardiovascular pathogenicity of lipoprotein (a) is not significantly greater in black patients despite higher lipoprotein (a) levels.

Black or African American↗
PubMed1992

Effect of valve deformity on results and mitral regurgitation after Inoue balloon commissurotomy.

BACKGROUND: The effect of valve deformity and patient age adversely affect the results of percutaneous transvenous mitral commissurotomy (PTMC) with conventional balloons. METHODS AND RESULTS: These factors were characterized after PTMC with the Inoue balloon. The increases in mitral valve area and mitral regurgitation after the procedure were evaluated comparing echocardiographic score of 8 or less versus more than 8, age of less than 60 versus age of 60 years or more, and age of less than 70 versus age of 70 years or more. One hundred sixty-two patients (mean age, 52 +/- 14 years) were studied. For the entire group, mitral valve area increased from 1.0 to 1.8 cm2 (p less than 0.001). Valve area increased from 1.0 +/- 0.3 to 1.8 +/- 0.6 cm2 in patients with echocardiographic score of 8 or less (n = 102) and from 1.0 +/- 0.3 to 1.7 +/- 0.5 cm2 with echocardiographic score of more than 8 (n = 44). Patients less than 60 years old (n = 104) had increases in valve area from 1.0 +/- 0.3 to 1.8 +/- 0.6 cm2 versus 1.0 +/- 0.4 to 1.8 +/- 0.6 cm2 for those 60 years old or older (n = 50) (p = NS). There was no significant difference in resultant valve area when the age division was increased to less than 70 versus 70 years or more. Similarly, the percentage of patients with 2+ or greater increase in mitral regurgitation was not different for those with higher than for those with lower echocardiographic scores (4% versus 12%, p = NS), age of less than 60 versus age of 60 years or more (10% versus 10%, p = NS), or age of less than 70 versus age of 70 or more years (9% versus 18%, p = NS). Valve replacement for mitral regurgitation was performed in four patients (one emergency), all with echocardiographic scores of less than 8. CONCLUSIONS: Age and extent of valve deformity do not have significant effects on acute results of PTMC using the Inoue balloon. Unique balloon geometry or the controlled, stepwise balloon sizing may explain these acceptable acute results in patients with more-deformed valves.

Adult↗
PubMed1992

Sex-associated differences in left ventricular function in aortic stenosis of the elderly.

BACKGROUND: In aortic stenosis, the response of the left ventricle to pressure overload varies from compensated hypertrophy to overt heart failure. The determinants of left ventricular adaptation are poorly understood. METHODS AND RESULTS: Left ventricular function was compared to assess the role of sex in 34 women and 29 men 60 years or older with both hemodynamic and echocardiographic data characteristic of severe aortic stenosis and no important coronary artery disease. Despite a similar degree of left ventricular outflow obstruction in women versus men (aortic valve area 0.54 +/- 0.20 versus 0.59 +/- 0.19 cm2, NS), the left ventricle of women had a greater fractional shortening (37 +/- 12 versus 25 +/- 12%, p = 0.001), achieved a smaller end-systolic chamber size (1.82 +/- 0.64 versus 2.17 +/- 0.65 cm/m2, p = 0.04), and generated more pressure (210 +/- 35 versus 182 +/- 29 mm Hg, p = 0.001) with a greater maximum positive dP/dt (2.153 +/- 794 versus 1,595 +/- 384 mm Hg/sec, p = 0.02). The men had a lower cardiac index (2.12 +/- 0.59 versus 2.49 +/- 0.63 l/min/m2, p = 0.02), higher mean pulmonary artery pressure (35 +/- 13 versus 27 +/- 10 mm Hg, p = 0.01), and shorter ejection period (340 +/- 40 versus 370 +/- 40 msec, p = 0.02). Women and men were equally symptomatic. Supernormal left ventricular ejection performance was present in 41% of the women and only 14% of the men (p = 0.002). This subgroup of women had a small, thick-walled chamber (end-diastolic radius to thickness ratio, 1.58 +/- 0.52 versus 2.45 +/- 0.51 in control women, p = 0.01) with low end-systolic wall stress. Subnormal ejection performance was present in 64% of the men and only 18% of the women (p = 0.002). This subgroup of men had an increased chamber size and high end-systolic wall stress compared with control men. Greater left ventricular mass was present in men compared with women (211 +/- 55 versus 179 +/- 55 g/m2, p = 0.03). CONCLUSIONS: Sex is a factor in left ventricular adaptation to valvular aortic stenosis in adults 60 years or older.

Aged↗
PubMed1992

Changes in valvular resistance, power dissipation and myocardial reserve with aortic valvuloplasty.

Balloon aortic valvuloplasty results in small changes in valve area with great symptomatic improvement in some patients, while others have little relief with greater increases in valve area. Alternative indices to valve area may help explain this clinical discrepancy. A calculation of valve area does not provide a means of assessing the load imposed by a stenotic valve, while the complementary index valve resistance, defined as the quotient of mean pressure difference divided by flow, allows many other hemodynamic calculations and may provide an additional measure of the hemodynamic importance of valvular obstructions. To assess the value of these calculations, we studied hemodynamic changes in thirty elderly patients undergoing valvuloplasty for aortic stenosis. The valve area, as calculated by the Gorlin formula, increased by an average 67% (0.59 cm2 to 0.95 cm2), while hemodynamic resistance decreased by an average 52% (453 to 207 dyne.sec.cm5). The values of resistance were used to predict pressure gradients and work loads at different cardiac outputs. The increase in myocardial reserve with valvuloplasty was calculated as the increase in cardiac output that could be achieved at the pre-valvuloplasty value of either total ventricular pressure or ventricular work. These calculations assumed that valvular resistance did not change with cardiac output and that peripheral resistance varied inversely to cardiac output so as to maintain a constant aortic (systemic) pressure. The increase in myocardial reserve was 18% when ventricular work rate was the limiting factor, and 103% when pressure was limiting. The increase in reserve may be closer to the higher value since the myocardial work rate is probably not limited by myocardial energy in the absence of coronary artery disease. Four patients who did not do well clinically were characterized by small increases in reserve, either because of inadequate dilatation of the valve or because the original stenosis was not severe. Valve resistance, myocardial reserve, and ventricular work may be calculated using standard hemodynamic measurements. In conjunction with aortic valve area, these indices provide significant complimentary information and may further elucidate the hemodynamic consequences of valvular obstruction.

Aged↗
PubMed1991

Valve deformity and balloon mechanics in percutaneous transvenous mitral commissurotomy.

Percutaneous transvenous mitral commissurotomy (PTMC) using balloon catheters has emerged as an alternative therapeutic modality for patients with mitral stenosis. When used initially in the United States, a single balloon, designed for peripheral arterial angioplasty, was passed across the intraatrial septum for mitral dilatation. The results were less than ideal, with resultant valve areas between 1.0 and 1.5 cm2. Double balloon dilatation was introduced and yielded valve areas between 1.5 and over 2.0 cm2. However, the double balloon technique is substantially more cumbersome, requires passage of two catheters through the atrial septum with an incidence of atrial septal defect, and results in significant hemodynamic sequelae during the procedure. This report describes a novel single balloon for PTMC. In contrast to the more conventionally used peripheral arterial balloons, this device was specifically designed for mitral stenosis. Results in 25 patients (mean age 60 +/- 5 years; range 29 to 87 years) showed an increase in value area from 0.9 +/- 0.2 cm2 to 1.6 +/- 0.5 cm2 (p less than 0.001). In contrast to the results reported with conventional balloon dilatation, there was no difference in the resultant valve area or in the incidence of complications among patients with more severely deformed valves compared with patients with more "ideal" valves for commissurotomy. An in vitro comparison of the pressure-volume characteristics of the conventional versus the Inoue balloon showed the latter to be more compliant, reaching nominal inflated diameter at 2.0 +/- 0.4 atm versus 3.3 +/- 0.5 atm for conventional balloons (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Left ventricular mechanics in preeclampsia.

Increased systemic vascular resistance and contracted blood volume are characteristic findings in preeclampsia. These alterations in cardiovascular hemodynamics can adversely affect ejection phase indices of left ventricular performance making it difficult to separate abnormalities resulting from changes in load from those caused by depressed myocardial contractility. To address this issue the contractility-sensitive, load-independent relationship between left ventricular end-systolic wall stress and rate-corrected velocity of fiber shortening was assessed in 10 nulliparous patients with preeclampsia. Comparisons were made with data obtained from 10 age-matched normotensive women with uncomplicated pregnancies (control subjects). Studies were performed by means of two-dimensionally targeted M-mode echocardiography and calibrated carotid pulse tracings during early labor, 1 day after delivery, and 4 weeks after delivery. During early labor and 1 day after delivery, patients with preeclampsia had elevated blood pressure and increased total systemic resistance. These parameters returned to normal by 4 weeks after delivery. Before delivery and 24 hours after delivery, the patients with preeclampsia had lower overall left ventricular performance (as measured by cardiac output and rate-corrected velocity of fiber shortening) and higher left ventricular afterload (as measured by left ventricular end-systolic wall stress) when compared with control subjects. These differences were no longer present 4 weeks after delivery. Despite the time-related intergroup differences in hemodynamics, left ventricular contractility was similar between normotensive and preeclamptic subjects at all stages of the study. Thus when load is eliminated as a confounding variable, the decrements in overall left ventricular performance measured in patients with preeclampsia reflect a mechanically appropriate response to increased afterload rather than an abnormality in the ventricular contractile state.

Adult↗
PubMed1991

Determination of pulse wave velocities with computerized algorithms.

Careful determination of pulse wave velocity is important in the study of arterial viscoelastic properties, wave reflections, and ventricular-arterial interactions. In spite of its increasingly widespread use, there is as yet no standardized method for its determination. Most studies have manually identified the transit time of the pressure wave front as it travels over a known distance in the arterial system, but the issues of accuracy and reproducibility have not been addressed. This study was designed to investigate the efficacy of four computerized algorithms in the determination of pulse wave velocities in invasive as well as in noninvasive pressure determinations. The four methods were the identification of: (1) the point of minimum diastolic pressure, (2) the point at which the first derivative of pressure is maximum, (3) the point at which the second derivative of pressure is maximum, and (4) the point yielded by the intersection of a line tangent to the initial systolic upstroke of the pressure tracing and a horizontal line through the minimum point. High-fidelity aortic pressure recordings were obtained in 26 patients with a multi-sensor micromanometer catheter. Noninvasive brachial and radial pressure waveforms were recorded in 11 volunteers with external piezoelectric transducers. The results show that the first derivative method consistently provided results that were different from the other methods for both the invasive and noninvasive methods because of changes in the structure of the upstroke as the arterial pulse propagates distally. Although the minimum method worked well for the invasive determinations, it was erratic with the noninvasive determinations, probably because of the higher amount of noise and reflection in the latter. Among the four algorithms, the second derivative and the intersecting tangents methods worked well with both invasive and noninvasive determinations with mean variation coefficients of less than 7% and correlation coefficients between the methods of greater than 0.90 for all data. In conclusion, computerized algorithms allow accurate determination of pulse wave velocity in invasively and noninvasively measured arterial pressure waveforms.

Adult↗
PubMed1990

[Peritoneal equilibration test].

7 men and 3 women (mean age 62 +/- 11 years) with end-stage renal disease, who were on continuous ambulatory peritoneal dialysis, underwent a peritoneal equilibration test to determine the rate of peritoneal ultrafiltration and creatinine transfer. The test is based on glucose absorption into the plasma from the peritoneal solution and the diffusion of creatinine into the peritoneal fluid after 2-4 hours. Patients with rapid absorption of glucose have low drain water ultrafiltration volumes but higher creatinine clearances, and therefore need adjustment of the therapy plan or else should be on hemodialysis. No correlation was found between the time the patients were on treatment and glucose absorption or creatinine diffusion.

Aged↗
PubMed1990

Cardiac catheterization in the patient with history of allergy to local anesthetics.

Patients with a history of allergic reactions to local anesthetic drugs present a difficult problem during evaluation for cardiac catheterization procedures. In the worst cases the procedure may be deferred, or even performed without local anesthesia. In the vast majority of patients an acceptable agent for safe local anesthetic use can be found. Skin testing beginning with very dilute solutions of preservative-free local anesthetic agent may be administered easily. This report describes the practical aspects of skin testing and local anesthetic agent selection in patients with a history of allergic reaction to local anesthetic drugs.

Adult↗
PubMed1990

Time delays in the diagnosis and treatment of acute myocardial infarction: a tale of eight cities. Report from the Pre-hospital Study Group and the Cincinnati Heart Project.

To establish the magnitude of prehospital and hospital delays in initiating thrombolytic therapy for acute myocardial infarction, the time from telephone 911 emergency medical system (EMS) activation to treatment and its components were analyzed from eight separate ongoing trials. This included estimates of ambulance response time, prehospital evaluation and treatment time, and time from admission to the hospital to initiation of thrombolytic therapy. The average time from EMS activation to patient arrival at the hospital was prospectively determined to be 46.1 +/- 8.2 minutes in 3715 patients from eight centers. The time from admission to the hospital to initiation of thrombolytic therapy was retrospectively determined to be 83.8 +/- 55.0 minutes in a separate group of 730 patients from six centers. Both the prehospital and hospital time delays were much longer than those perceived by paramedics and emergency department directors. Shorter hospital time delays were observed in patients in whom a prehospital ECG was obtained as part of a protocol-driven prehospital diagnostic strategy and a diagnosis of acute infarction made before arrival at the hospital (36.3 +/- 11.3 minutes in 13 patients). These results show that the magnitude of time required to evaluate, transport, and initiate thrombolytic therapy will preclude initiation of treatment to most patients within the first hour of symptoms. Implementation of a protocol-driven prehospital diagnostic strategy may be associated with a reduction in time to thrombolytic therapy.

Electrocardiography↗
PubMed1990

Hemodynamic resistance as a measure of functional impairment in aortic valvular stenosis.

Calculated valve area depicts anatomical stenosis but does not quantify hemodynamic impairment. We propose that hemodynamic resistance, defined as the mean pressure gradient across the valve divided by mean flow rate during systolic ejection, gives a better indication of hemodynamic obstruction. This index was compared with Gorlin valve area in 40 patients with aortic stenosis. Calculated area ranged from 0.22 to 1.26 cm2, and mean transvalvular resistance ranged from 117 to 1,244 dyne.sec.cm-5. In general, resistance varied inversely with calculated area, but there was substantial variation about the mean relation. All of the variation could be accounted for by variations in the pressure gradients at each value of calculated area. Resistance was higher in proportion to area when flow and pressure gradient were high. Analysis of five published studies of a total of 83 valves showed that calculated area changed at least three times more than resistance when pressure gradient was varied. The utility of resistance as an index of stenosis is demonstrated by example calculations that show how during exercise a stenotic valve increases the ventricular work rate out of proportion to the work done on the peripheral resistance. These calculations are possible because hemodynamic resistance defines functional impairment in units commonly used for quantification of opposition to flow. Furthermore, resistance appears to be less dependent than area on conditions of measurement and does not require an empirical constant.

Aortic Valve↗
PubMed1989

Informed consent in emergency research. Prehospital thrombolytic therapy for acute myocardial infarction.

Can the conscious patient in the midst of a medical emergency provide adequate informed consent for a clinical research protocol? Adequate consent is crucial to the ethical conduct of clinical trials, including those performed in emergency settings. We examine the problem of emergency informed consent. As an illustrative case, we discuss a pilot trial of prehospital thrombolytic therapy for myocardial infarction. Federal regulations for clinical research do not provide clear guidelines on emergency research in the conscious patient. Clinical investigators currently approach emergency consent in four ways: (1) avoid such research, (2) omit the consent process, (3) obtain deferred consent, or (4) obtain customary consent. We suggest a fifth alternative, two-step consent, which permits the conduct of emergency research while protecting the rights of the emergency research subjects. Such a process may serve as an alternative solution for future studies faced with the problem of informed consent in emergencies.

Emergencies↗
PubMed1989

An improved catheter design for crossing stenosed aortic valves.

Retrograde catheterization of the left ventricle in patients with aortic valve stenosis is commonly performed using a pigtail or coronary arterial catheter. This approach, although usually ultimately successful, may be highly tedious. To overcome the limitations of these conventional catheter shapes, we have designed a catheter specifically for crossing stenotic aortic valves. In a group of 17 patients, mean aortic valve area 0.75 cm2, the average time to cross the aortic valve was 2 minutes 45 seconds and the median time 30-40 seconds. Once the proper size catheter was selected, the average time to cross was 59 seconds. The success of this catheter is based on the operator's ability to "scan" or interrogate the surface of the valve thoroughly by manipulating the catheter and a moveable core straight tip guidewire.

Aged↗
PubMed1989

Evaluation of patients for the need of thrombolytic therapy in the prehospital setting.

Maximum benefit from thrombolytic therapy in acute myocardial infarction is obtained with early therapy. The earliest possible time to treat is during the initial evaluation of the patient in the home or ambulance, which requires accurate diagnosis of acute myocardial infarction in the prehospital setting. In our study, paramedics evaluated patients who had chest pain with a 12-lead ECG transmitted by cellular telephone and a checklist for inclusion and exclusion criteria for thrombolytic therapy. This information was transmitted to a hospital-based telemetry physician who diagnosed or excluded acute myocardial infarction and made a mock decision to withhold or administer a thrombolytic agent. Forty-eight patients with chest pain were evaluated. Six were diagnosed as having overt acute myocardial infarction by the hospital-based telemetry physician. All six patients had the diagnosis substantiated by both ECG and enzyme studies on hospital admission. Based on the data supplied by paramedics, two of these six patients were considered eligible for thrombolytic therapy by the physician. Hospital evaluation confirmed the prehospital decision to treat with a thrombolytic agent. In addition, all other patients were appropriately diagnosed as ineligible. Prehospital ECG diagnosis resulted in two patients going directly to the catheterization lab, thereby bypassing the emergency department. Overt acute myocardial infarction can be accurately identified by a prehospital-acquired 12-lead ECG transmitted to a hospital-based physician. Our study demonstrates that in conjunction with specially trained paramedics, the hospital physician can decide whether to administer thrombolytic therapy to such patients in the prehospital setting.

Adult↗