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Biomedical subjects

S B Feinstein

Publications and source records attributed to S B Feinstein.

At least 19 recordsLinked to original sources
PubMed1995

Safety and feasibility of renal blood flow determination during kidney transplant surgery with perfusion ultrasonography.

Contrast-enhanced perfusion patterns of newly transplanted kidneys were determined in 10 patients. Albumin-stabilized sonicated microspheres were injected into the iliac-renal artery of the transplanted kidney while continuous two-dimensional ultrasound images were recorded. Doppler derived resistance index (RI) of the transplanted kidney's blood flow before injection of contrast (0.68 +/- 0.8) did not differ significantly from RI measured immediately after injection (0.72 +/- 0.13) or RI 24 h after surgery (0.69 +/- 0.11). Heart rate, mean arterial pressure, central venous pressure, and electrocardiogram (ECG) signs for ischemia did not change during contrast injections. Renal scintigraphy and renal biopsy revealed acute tubular necrosis and/or rejection in two patients at 24-48 h. Videodensitometry was used to assess the ratio of inner to outer peak pixel intensity from the recorded tomographic images in six patients. In both patients with acute rejection, the inner to outer cortex peak pixel intensity was greater than 1, whereas it was less than 1 in the remaining four patients with normal postoperative renal function. Visual scores (0-3) of contrast enhancement for three doses of Albunex were evaluated (0.5 mL, 1.0 mL, 2.0 mL). Two milliliters always enabled perfusion assessment. In seven patients the identical dose of Albunex was injected immediately before and 30 s after 2 mg of verapamil was injected directly into the renal artery at the time of surgery. The contrast enhancement score before verapamil (1.4 +/- 0.6) was significantly less than the enhancement score after (2.1 +/- 0.6), implying greater renal blood flow after verapamil.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Evaluation of changes in skeletal muscle blood flow in the dog with contrast ultrasonography.

Intraoperative methods to assess skeletal muscle blood flow or muscle-flap perfusion during vascular reconstructive surgery are limited. At present, techniques enable only anatomic identification of the degree of patency of large vessels. We report here the first use of ultrasonography to assess dynamic changes in skeletal muscle perfusion. Baseline blood flow in the adductor muscle group of the hindlimbs of seven dogs was measured with an electromagnetic flow probe and with contrast ultrasound using the contrast agent Albunex. Blood flow was manipulated in each dog pharmacologically with random administration of intraarterial injections of Neo-Synephrine and papaverine. After each change in blood flow detected by electromagnetic flow probe, flow also was assessed qualitatively by four independent observers who graded video-recorded contrast enhancement in the muscle group on a 0 to 4 scale. Videodensitometry also was used to generate time versus intensity curves in the adductor muscle region of interest. Peak pixel intensity was determined during each flow condition. A total of 21 flow measurements were made with each assessment scheme (electromagnetic flow probe, video enhancement, videodensitometry) for each condition (7 control, 7 papaverine, 7 Neo-Synephrine). Changes in blood flow assessed by video enhancement scores and changes in peak pixel intensity correlated with changes measured by electromagnetic flow probe (r = 0.84 and 0.66, respectively). We conclude that contrast ultrasound may be used to detect changes in skeletal muscle perfusion intraoperatively. Measures of muscle perfused by visual inspection of contrast enhancement and videodensitometric data were in agreement with direct measurements of changes in skeletal muscle blood flow.

Animals↗
PubMed1994

Contrast echocardiography.

Myocardial contrast echocardiography (MCE) is an ultrasound imaging technique which promises to provide a safe, noninvasive means of assessing myocardial perfusion. A contrast agent, consisting of a suspension of air-filled microspheres, serves as an ultrasound tracer. When these microspheres are injected intravascularly, the acoustic interface created between the blood and the microspheres enhances the reflected ultrasound signals. Thus, the flow pattern of the microspheres represent the actual blood flow patterns. This paper will review the field of contrast echocardiography, its background and history, the development of ultrasound contrast agents, and a variety of experimental as well as clinical uses. Contrast echocardiography has been utilized in the cardiac catheterization laboratory for the assessment of "risk area," assessment of collateral blood flow and assessment of coronary blood reserve. In the operating room, contrast echo is utilized for the determination of cardioplegic perfusion, assessment of graft patency and evaluation of valvular regurgitation. In the future, with the technical advancement in ultrasound imaging and the active interest and growth in the field of myocardial perfusion imaging using contrast echocardiography, the ability to provide routine real-time perfusion imaging may become a reality.

Albumins↗
PubMed1994

The relationship between immediate outcome after cardiac surgery, homogeneous cardioplegia delivery, and ejection fraction.

BACKGROUND: Optimal myocardial protection during cardiac surgery with ischemic arrest is predicated on among other variables, homogeneous cardioplegia distribution. Contrast echocardiography has been shown to provide information regarding the intramyocardial distribution of cardioplegia solution. To test the hypothesis that information regarding cardioplegia distribution derived from contrast echocardiography may be associated with immediate clinical outcome after cardiac surgery, data from 21 patients were examined retrospectively. METHODS: Contrast-enhanced cardioplegia distribution patterns of the left ventricle short axis view obtained with transesophageal echocardiography were examined off-line by four observers blinded to clinical outcome. Contrast effect was scored for eight equally divided myocardial segments (0 = no contrast, 1 = nonuniform contrast, 2 = uniform contrast, 3 = excessive contrast). The scores were then averaged between segments and between observers to generate an antegrade, a retrograde, and a combined global contrast score for each patient. RESULTS: Seventeen patients were separated from bypass without difficulty (group A) and 4 patients required sustained inotropic therapy or an intra-aortic balloon pump to facilitate separation from bypass (group B). As would be expected, group A patients had a higher average preoperative ejection fraction than did group B patients (60 percent +/- 14 vs 31 percent +/- 7, p < 0.01). In group A, however, for 4 of 17 patients (23 percent), low preoperative ejection fraction was not predictive of postoperative exogenous circulatory support requirements. Group A patients also had significantly higher antegrade (1.6 vs 1.2, p < 0.02), retrograde (1.7 vs 1.1, p < 0.02), and combined global contrast scores (1.7 vs 1.1, p < 0.01) than did group B patients. All patients with low preoperative ejection fraction and low intraoperative contrast scores required exogenous support to separate from cardiopulmonary bypass. CONCLUSION: Contrast echocardiography makes possible an evaluation of the intensity and distribution of contrast-enhanced cardioplegia delivery and we believe the efficacy of intraoperative myocardial protection. Although low preoperative ejection fraction is a known predictor of poor immediate postoperative outcome following cardiac surgery, not all patients with low preoperative ejection fractions require inotropic support postoperatively. Our results suggest that monitoring cardioplegia distribution with contrast echocardiography may offer insight for better patient stratification based on intraoperative myocardial protection in patients with low ejection fraction. We believe a more extensive evaluation of this relationship should be pursued in a prospective manner.

Aged↗
PubMed1992

Myocardial perfusion: contrast echocardiography perspectives.

Contrast echocardiography may become a useful means of quantifying transmural regional myocardial perfusion patterns, experimentally and clinically, in a variety of settings. Contrast echocardiography has already been used in the operating room to study perfusion during coronary artery bypass graft (CABG) surgery. Other recent studies have demonstrated the ability of contrast echocardiography to predict wall motion improvement following acute myocardial infarction and therapeutic intervention. This is significant in the light of the discrepancy that has recently been shown between epicardial coronary vessel diameter and coronary flow. Studies suggest that both tissue and blood flow and volume may be quantitatively evaluated using contrast echocardiography, and these parameters ultimately may be used to assess tissue viability or vascular reserve. Contrast echocardiography techniques have been shown to be safe and reliable, and provide a high degree of spatial and temporal resolution.

Coronary Circulation↗
PubMed1992

A comparison of methods for the detection of myocardial ischemia during noncardiac surgery: automated ST-segment analysis systems, electrocardiography, and transesophageal echocardiography.

Clinicians often fail to detect intraoperative ischemic electrocardiographic (ECG) changes when viewing oscilloscopes. Automated ST-segment monitors promise to increase the detection of such ECG changes. We investigated the capacity of two commercially available ST-segment monitors to detect intraoperative myocardial ischemia in patients at high risk for developing intraoperative myocardial ischemia during vascular and other noncardiac procedures. The ST-segment monitors were compared with two reference monitors: (a) printed eight-lead ECGs, as interpreted by a cardiologist, and (b) the presence of segmental wall motion abnormalities and thickening abnormalities detected by transesophageal echocardiography (TEE). We also examined the capacity of the printed ECG to diagnose myocardial ischemia when compared with TEE. We studied 44 patients who underwent TEE, printed multilead ECG, oscilloscope monitoring of leads V5 and II, and measurement of ST-segment deviation from the baseline using an automated Hewlett Packard ST-segment device. The sensitivities for the Hewlett Packard system were 40% for TEE-diagnosed myocardial ischemia and 75% for ECG-diagnosed ischemia. Comparison of the printed ECG with TEE revealed that ST-segment changes in the printed ECG, as analyzed by a cardiologist, were 25% sensitive and 62% specific for the detection of TEE-diagnosed myocardial ischemia. When T-wave inversions were added to ST-segment depression as a criterion for the diagnosis of myocardial ischemia by the printed ECG, the sensitivity of ECG for the detection of intraoperative myocardial ischemia, as determined by TEE, was 40% and specificity was 58%. Twenty-three of the 44 patients were simultaneously monitored in leads I, II, and V5 with an automated Marquette ST-segment monitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Assessment of retrograde cardioplegia distribution using contrast echocardiography.

Retrograde cardioplegia has gained popularity in coronary and noncoronary cardiac operations. We have used contrast echocardiography in the open-chest canine model to compare the distribution of cardioplegia delivered antegrade in the aortic root versus retrograde through the coronary sinus, and to determine the effect of coronary occlusion on that delivery. With no coronary occlusion, antegrade cardioplegia was distributed to the entire left ventricle and septum whereas retrograde cardioplegia was distributed to the left ventricular free wall but had inconsistent delivery to the septum. Acute occlusion of the left circumflex coronary artery resulted in 57.06% +/- 9.52% of the left ventricle not being perfused by antegrade cardioplegia and occlusion of both the left circumflex and anterior descending coronary arteries caused a 65.46% +/- 18.5% reduction in perfusion by antegrade cardioplegia. Acute coronary occlusion had no effect on retrograde cardioplegia distribution. We conclude that retrograde cardioplegia is less homogeneous than antegrade cardioplegia in the intact coronary circulation but that retrograde cardioplegia preserves cardioplegia distal to acutely occluded coronary arteries. Furthermore, contrast echocardiography is a useful method of assessing myocardial perfusion and may have useful clinical applications.

Albumins↗
PubMed1991

Assessment of myocardial perfusion during CABG surgery with two-dimensional transesophageal contrast echocardiography.

No reliable, quantifiable index of tissue perfusion is currently available to assess the efforts of coronary artery bypass graft (CABG) surgery. We used two-dimensional transesophageal contrast echocardiography with sonicated Renografin-76 microbubbles to determine the distribution of myocardial blood flow during coronary artery bypass graft surgery in 15 patients. Sonicated Renografin-76 contrast agent was injected into the aortic root of all patients after institution of cardiopulmonary bypass and application of the aortic occlusive clamp. Eight patients had contrast agent injected directly into the free proximal end of the vein-CABG anastomosis. All patients again received aortic root injections during reperfusion after anastomosis of the proximal aortovein and distal coronary artery. Echocardiographic images of the left ventricle short axis at the level of the papillary muscles were obtained in real time and analyzed retrospectively from videotape. Injection of contrast provided information about the magnitude and geometric distribution of coronary artery-vein bypass run-off and enabled identification of poorly perfused myocardial regions. When predicted myocardial perfusion patterns, based on preoperative evaluation of epicardial vessel distribution derived from coronary angiography, were compared to actual perfusion patterns assessed with intraoperative echocardiography, contrast regional myocardial perfusion patterns were predicted 84% of the time (71-97%, 95% confidence limit). Regional myocardial perfusion deficits detected after coronary bypass grafting were associated with regional wall motion abnormalities detected after separation from cardiopulmonary bypass. Our technique makes possible on-line visualization of changes in regional blood flow in the heart before, during, and after CABG.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Safety and efficacy of a new transpulmonary ultrasound contrast agent: initial multicenter clinical results.

Myocardial contrast echocardiography has been found to be a safe and useful technique for evaluating relative changes in myocardial perfusion and delineating areas at risk. Although earlier contrast agents required direct delivery into the coronary arteries or aortic root, a new echocardiographic contrast agent, sonicated albumin microspheres (Albunex), has been found to cross the pulmonary circulation in experimental models. To determine the safety and preliminary efficacy of intravenous injections of Albunex in humans, 71 patients at three independent medical institutions underwent two-dimensional echocardiographic examination before, during and after the administration of three intravenous doses of Albunex, ranging from 0.01 to 0.12 ml/kg body weight. All patients provided a complete history and underwent physical and neurologic examination and laboratory and electrocardiographic evaluation before the injections; all evaluations (except for the history) were repeated at 2 h and 3 days after the injections of Albunex. The efficacy of the injections was qualitatively assessed by two independent blinded observers using a grading system of 0 to +3, with 0 indicating an absence of contrast effect and +3 indicating full opacification of the cavities examined. All injections were well tolerated and no serious side effects were noted in any of the patients. Irrespective of dose group, a cavity opacification greater than or equal to +2 was seen in the right ventricle in 212 (88%) of 240 injections and in the left ventricle in 151 (63%) of 240 injections as judged by the independent observers. The degree of ventricular cavity opacification appeared to be dose and concentration related.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Contrast echocardiography: a method to visualize changes in regional myocardial perfusion in the dog model for CABG surgery.

The ability of contrast echocardiography to assess regional myocardial perfusion during cardiopulmonary bypass in a dog model for coronary artery bypass surgery was evaluated. Sonicated Renograffin-76 microbubbles (meglumin diatrigoate and sodium diatrigoate) were injected into an aortic root proximal to an aortic occlusion clamp root while dogs were on cardiopulmonary bypass, with the heart arrested in diastole. Echocardiographic contrast-enhanced regions of myocardial perfusion were easily visualized. Differences in contrast-enhanced myocardial regions depended on coronary artery occlusion or patency. The contrast-enhanced images of myocardial perfusion showed that, for a given myocardial segment of the supplying vessel, the presence or absence of contrast effect reliably predicted vessel occlusion or patency (P less than .01). In the future contrast echocardiography may allow the direct assessment of regional myocardial perfusion in the operating room.

Animals↗
PubMed1989

Contrast echocardiography: effects of microbubbles on coronary blood flow and left ventricular hemodynamics.

Contrast echocardiography is currently being used to define and quantitate myocardial perfusion at the time of cardiac catheterization. Limited and conflicting data exist regarding the physiologic effects of microbubble-containing contrast agents. In the present study, coronary blood flow measured using an electromagnetic flow meter, blood pressure, and heart rate responses were studied in six dogs. An ECG-gated power injector was used to deliver 7 to 9 ml of sonicated and nonsonicated solutions (saline, Renografin-76, dextrose 50% and 70%, and sorbitol 70%) through an intra-aortic catheter placed above the aortic cusps. Paired injections of sonicated and nonsonicated agents were compared to determine whether the presence of microbubbles affected the physiologic response to these agents. Simultaneous recordings of two-dimensional cross-sectional images of the left ventricle were obtained. Data are expressed as percentage of change from preinjection control values. Within 10 seconds of an injection, decreases in coronary blood flow occurred in a range from -1 to -10% compared with preinjection control values. Coronary blood flow increased between 10 and 25 seconds postinjection within a range from +11 to +29%. Systemic blood pressures rose during injections and then declined below control values within 10 seconds. The magnitude of the decline in systolic blood pressure ranged from -5. to -18%. Diastolic blood pressure declined in a range from -13 to -33%. Within 20-30 seconds postinjection, systemic blood pressure rose above control values. The magnitude of the systolic and diastolic blood pressure rise ranged from +4 to +11%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Right heart dysfunction, pulmonary embolism, and paradoxical embolization during liver transplantation. A transesophageal two-dimensional echocardiographic study.

In 16 adult patients, we performed continuous intraoperative two-dimensional transesophageal echocardiography (2DTEE) to help elucidate the mechanism of myocardial dysfunction that accompanies liver transplantation. In 4 of the 16 patients "paradoxical" motion of the interventricular septum consistent with right ventricular failure was seen. An additional three of the 16 patients showed right atrial enlargement and right-to-left deviation of the interatrial septum. Two patients showed evidence of paradoxical embolization (one of whom had right ventricular and right atrial enlargement), and a third patient (who had right atrial enlargement) embolized a large right atrial thrombus into the pulmonary circulation. Two-dimensional transesophageal echocardiography demonstrated that isolated right ventricular failure might account for some of the hemodynamic instability seen during liver transplantation. Venous, pulmonary, and paradoxical embolization of air and thrombi documented by transesophageal echocardiography likely contribute to right heart failure.

Adolescent↗
PubMed1989

Quantitation of renal blood flow by contrast ultrasonography: preliminary results.

Contrast ultrasonography, employing tracers behaving like red blood cells, is a promising technique to study regional blood flow distribution. Aim of this note is to quantitate renal blood flow in the dog using contrast ultrasonography. Mathematical formulae derived from the classical dye-dilution theory are applied. Ten different renal blood flow levels (ranging from 16 to 125 ml/min) were obtained by means of mechanical (stenosis and reperfusion) and pharmacological interventions (iv infusion of adrenaline, noradrenaline and fenoldopam). Renal blood flow was measured by electromagnetic flow-meter and contemporary calculated by contrast ultrasonography. The correlation coefficient between measured and calculated flow was 0.92 (p less than 0.01). Contrast ultrasonography is a technique capable of measuring renal blood flow at a wide range of different flow levels.

Albumins↗
PubMed1988

Myocardial risk area and peak gray level measurement by contrast echocardiography: effect of microbubble size and concentration, injection rate, and coronary vasodilation.

Contrast agents were injected via the intracoronary route in eight dogs during two-dimensional echocardiographic imaging to determine the influence of microbubble size and concentration, injection rate, and coronary vasodilation on risk area and peak gray level measurement. At an injection rate at 13 cc/sec, the average background-subtracted peak gray level intensity of hand-agitated diatrizoate meglumine/diatrizoate sodium was significantly (p less than 0.01) higher than that of hand-agitated diatrizoate meglumine/diatrizoate sodium + 0.9% saline, sonicated diatrizoate meglumine/diatrizoate sodium, and sonicated 70% sorbitol. These differences were abolished by the use of 38 cc/sec injection rates and intracoronary injection of adenosine. Perfusion area determinations as assessed by planimetry were unaffected by the contrast agent used, the injection rate, or by intracoronary administration of adenosine. We conclude that risk area measurement by the ultrasound contrast technique is not affected by varying contrast agents, injection rates, or vasodilation. However, peak gray level intensity is variable among contrast agents and may result in variability of time-activity curve analysis.

Animals↗
PubMed1988

Contrast echocardiography during coronary arteriography in humans: perfusion and anatomic studies.

In humans, the physiologic relation between myocardial blood flow and epicardial coronary artery anatomy remains poorly defined. With the recent development of sonicated microbubble contrast agents, it is now possible to use contrast echocardiography to assess myocardial perfusion and to correlate blood flow with angiographically identified coronary artery anatomy. The purpose of the current study was to determine myocardial perfusion patterns in patients without significant coronary artery disease. The results may be used as a reference to analyze myocardial blood flow in patients with coronary artery disease. Sonicated meglumine sodium diatrizoate solution (Renografin-76), which contains microbubbles measuring 4.5 +/- 2.8 micrograms in diameter by laser analysis, was used as the echocardiographic contrast agent during elective coronary arterriography in 14 patients without significant coronary artery disease. Patients received intracoronary injections of 1.5 to 2 ml of sonicated Renografin-76 without complications. Perfusion characteristics were studied by visual assessment of the two-dimensional echocardiographic images obtained after individual injections. In patients found to be free of significant coronary artery disease by arteriography, the left coronary system always supplied the anteroseptal, anterior, anterolateral and posterior regions of the left ventricle at the mid-papillary, cross-sectional level. The right coronary artery system perfused the inferior and inferoseptal regions in 89% of the patients identified with a right dominant system. The anterolateral papillary muscle was perfused from the left coronary system in all cases. The posteromedial papillary muscle was perfused from the left coronary system in 58% of the patients and from the right system in 42% of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1987

Effect of intracoronary injections of sonicated microbubbles on left ventricular contractility.

Despite the recent interest in contrast-enhanced echocardiography as a means of defining myocardial perfusion, the effects of echo contrast agents on left ventricular (LV) contractility in humans remains poorly defined. This is particularly relevant because intracoronary injection of contrast agents used for angiographic visualization of coronary arteries produces significant alterations in LV hemodynamics. The relation of LV end-systolic wall stress (sigma es) to rate-corrected velocity of fiber shortening (Vcfc), a load-independent index of contractility, was studied in 7 patients undergoing elective coronary arteriography. Two-dimensional and targeted M-mode echocardiographic and central aortic pressure tracings were recorded during injections of standard volumes of angiographic (7 to 9 ml of nonsonicated Renografin-76) and echocardiographic (1.5 to 2.0 ml of sonicated Renografin-76) contrast agents into the left main coronary artery. The order in which agents were injected was randomly determined. Myocardial contractility was assessed under control conditions and 5 and 15 seconds after injection. Alterations in contractility relative to control were measured as the change in Vcfc after elimination of afterload (sigma es) as a confounding variable. An injection of Renografin-76 adequate for angiographic imaging of coronary artery anatomy resulted in a significant depression of LV contractility (p less than 0.001) in conjunction with a tendency toward increased afterload (p = 0.12); recovery occurred by 15 seconds after injection. The smaller amounts of sonicated Renografin-76 required to give adequate contrast enhancement of the myocardium did not alter LV contractile state or afterload.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Successful left ventricular opacification following peripheral venous injection of sonicated contrast agent: an experimental evaluation.

A new agent for use in contrast echocardiography that is capable of passing through the pulmonary circulation and opacifying the left ventricular cavity after intravenous injection was evaluated in a canine model. Air-filled albumin microbubbles were produced by sonication. A Coulter counter was used to size and count the resultant microbubbles in vitro. The microbubbles had diameters sufficiently small (less than 9 micron) to permit transpulmonary passage. A total of 72 injections were made into the forepaw vein of five closed-chest dogs. Simultaneous two-dimensional echocardiographic images of the right ventricle and the left ventricle were recorded and digitized on an off-line computer. Of the 72 injections, 59 (82%) were suitable for digitization. Forty of the 59 digitized injections (68%) demonstrated left ventricular contrast enhancement. Indicator-dilution curves were generated from plots of intraventricular gray level VS time, and the curve widths and areas under the curves were determined. The ratio of total indicator curve area for left to right ventricular cavity was 0.39 for the 40 successful injections, indicating transpulmonary transmission of 39% of the contrast effect. Injection of bubbles with mean size less than 6 microns resulted in a larger median left ventricular curve area than those with bubbles averaging from 6 to 9 microns. Injections demonstrating successful left ventricular contrast opacification had larger right ventricular curve areas than those that were not successful. Blood pressure, heart rate, and arterial blood gases were not significantly altered by repeated intravascular contrast injections. Postmortem examination of hearts, lungs, livers, and kidneys revealed no histologic changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗