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Biomedical subjects

A J Labovitz

Publications and source records attributed to A J Labovitz.

At least 55 records · Page 3Linked to original sources
PubMed1992

Exercise evaluation of prosthetic heart valves by Doppler echocardiography: comparison with catheterization studies.

Although valve replacement remains the cornerstone of treatment for critical heart valve dysfunction, problems including thromboembolism, infection, and primary failure of the prosthesis remain. Resting studies of valve hemodynamics are sometimes insufficient to reveal valve dysfunction. Early studies using cardiac catheterization focused on changes in prosthetic function seen with various types of exercise or drug-induced stress. These studies suffered from an inability to adequately stress catheterized patients and were cumbersome to the patient and the investigator. With the introduction of Doppler echocardiography, however, studies could be performed after significant exercise with low risk and increased ease. Using echocardiography, reports of exercise-induced changes in aortic and mitral valve hemodynamics have appeared. Over 600 patients have been studied using Doppler echocardiography. In the aortic position, all prostheses studied have a mild peak instantaneous gradient (18-26 mmHg) at rest, which increases with exercise (35-63 mmHg). No significant differences between the four models of mechanical prostheses studied are found. The gradients achieved with exercise do not appear to be related to the heart rate achieved or duration of exercise. Smaller prostheses are associated with larger gradients; however, the correlation was not strong. All mitral valve prostheses studied are also mildly stenotic at rest (range of mean gradients 2.3-7.1 mmHg) and become moderately stenotic with exercise (range 5.1-16.5). Although the lowest gradients are seen with St. Jude Medical and Medtronic Hall prostheses, their gradients are not significantly less than with other valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗
PubMed1992

The role of Doppler echocardiography in the assessment of left ventricular diastolic function.

The role of Doppler echocardiography of transmitral filling velocities in the assessment of diastolic function in man has not been adequately defined. It is now appreciated that multiple interacting factors such as loading conditions influence the transmitral velocity profile independent of intrinsic left ventricular diastolic function. Extrapolating the status of diastolic function from the transmitral velocity profile is complicated by these factors. The load dependence of ventricular filling has tempered the initial enthusiasm for the clinical application of the Doppler technique. In the present review, studies examining invasive parameters of diastolic function and Doppler indices of diastolic filling are discussed to gain greater insight and understanding of the role of Doppler echocardiography in the noninvasive assessment of diastolic function. These studies have demonstrated a relatively consistent influence of left ventricular relaxation, chamber stiffness, and left atrial pressure on the transmitral velocity filling profile. Impairment of relaxation impedes early filling and may result in a compensatory increase in atrial contribution to filling. An independent decrease in left atrial pressure from altered loading conditions may also reduce filling in early diastole. Increased left ventricular chamber stiffness (i.e., noncompliant left ventricle) impairs atrial contribution to filling and may enhance early filling. Theoretically, reduced left atrial contractility may decrease atrial contribution to filling. Pulmonic vein flow demonstrating increased retrograde flow during atrial systole helps to exclude impaired left atrial contractility. An increased left atrial pressure from altered loading conditions may also augment early filling. Therefore, an invasive or clinical assessment of left atrial pressure as being increased, decreased, or normal greatly aids in the interpretation of the transmitral filling velocity profile when inferences on the status of diastolic function are being made. Diastolic dysfunction is likely when a given pattern of filling cannot be explained on the basis of left atrial pressure. In situations where reasonable estimates on the status of left atrial pressure cannot be done, striking alterations in the transmitral velocity filling profile may be useful.

Animals↗
PubMed1992

The technique of transesophageal echocardiography. How to procure detailed views of an array of cardiac structures.

Use of transesophageal echocardiography (TEE) is growing in ambulatory, intensive care, and intraoperative settings. Forward flexion or retroflexion of the TEE probe tip at different levels in the esophagus reveals a variety of intracardiac structures; in the basal short-axis view, for example, the aortic valve can be seen, as can the left atrial appendage lateral to the aorta and pulmonary artery. In the four-chamber view, the mitral and tricuspid valves and interatrial septum can be viewed, and the morphology of the mitral valve leaflets and mitral annulus can be assessed. Cross-sectional views of both ventricles can be obtained in the transgastric short-axis view. In addition, the entire thoracic aorta, as well as the proximal ascending and transverse arch, can be visualized with TEE.

Echocardiography, Doppler↗
PubMed1992

Transesophageal echocardiography: expanding indications for ICU use. How TEE can complement--or surpass--transthoracic techniques.

Transesophageal echocardiography (TEE) is a Doppler technique that uses the esophagus as an acoustic window. In critically ill patients (particularly ventilated patients), TEE may be used to assess left ventricular function, valvular disease, endocarditis, and prosthetic valve dysfunction. It is also helpful in elucidating the cause of hypotension after cardiac surgery, and can detect chronic aortic dissection and transection, valve rupture, and myocardial contusion in trauma victims. TEE is superior to transthoracic echocardiography in evaluating a cardiac source of embolism. Contraindications to TEE include esophageal disorders and an uncorrected bleeding diathesis; a large hiatal hernia may cause suboptimal transgastric images.

Critical Care↗
PubMed1992

Anterior wall left ventricular aneurysm repair. A comparison of linear versus circular closure.

To determine the efficacy of ventricular closure techniques, we reviewed our experience with 62 patients who survived the repair of aneurysms of the anterior wall of the left ventricular from 1984 through 1989. Forty of these patients underwent aneurysm repair by standard linear closure and 22 by a circular closure technique. After a mean follow-up interval of 3 years, there were no demonstrable differences in angina class, New York Heart Association functional classification, or survival. In 41 surviving patients, postoperative left ventricular dimensions and function were satisfactorily evaluated by standard echocardiographic measurements. No significant differences were found in postoperative long-axis left ventricular systolic diameter or in short-axis systolic or diastolic areas. There was a significantly larger long-axis diastolic diameter in the circular closure group; however, there was no difference in this parameter when the ratios of postoperative to preoperative lengths were compared. Further intragroup comparisons demonstrated an increase in short-axis areas postoperatively within the circular closure group in contrast to a decrease in patients in the linear closure group; these changes were not statistically significant. There was no significant difference in postoperative ejection fraction between the two closure groups, although minor reductions were found in the circular closure group. These data demonstrate no significant difference between the linear and circular closure techniques with respect to standard echocardiographic parameters, functional classification, and survival.

Actuarial Analysis↗
PubMed1991

Comparison of transthoracic and transesophageal echocardiography for assessment of left-sided valvular regurgitation.

To compare transthoracic and transesophageal echocardiography in the clinical assessment of left-sided valvular regurgitation, 118 patients who underwent both transesophageal and transthoracic echocardiographic studies within a 24-hour period were included in this study. Presence or absence of aortic regurgitation was identified concordantly by both techniques in 93 patients (79%). Complete agreement between both techniques was found in 88 patients (75%). Presence or absence of mitral regurgitation was identified concordantly by both techniques in 89 patients (75%). Complete agreement in grade was found in only 74 patients (63%). Twenty-nine patients (25%) had mitral regurgitation detected by transesophageal echocardiography, but not by transthoracic echocardiography. Four of these patients (14%) had significant (2 to 3+) mitral regurgitation. Differences between transesophageal and transthoracic echocardiography do not appear to be clinically important in patients with aortic regurgitation. In mitral regurgitation, significant differences exist between these 2 techniques, with transesophageal echocardiography being much more sensitive.

Aortic Valve↗
PubMed1991

Atrial septal aneurysm and stroke: a transesophageal echocardiographic study.

The prevalence and morphologic characteristics of atrial septal aneurysms identified by transesophageal echocardiography in 410 consecutive patients are described. Two groups of patients were compared: Group I consisted of 133 patients referred for evaluation of the potential source of an embolus and Group II consisted of 277 patients referred for other reasons. An atrial septal aneurysm was diagnosed by transesophageal echocardiography in 32 (8%) of the 410 patients. Surface echocardiography identified only 12 of these aneurysms. Atrial septal aneurysm was significantly more common in patients with stroke (20 [15%] of 133 vs. 12 [4%] of 277) (p less than 0.05); right to left shunting at the atrial level was demonstrated in 70% of patients in Group I and 75% of patients in Group II by saline contrast echocardiography. Four patients in Group I had an atrial septal defect with additional left to right flow. There was no difference between the two groups in aneurysm base width, total excursion or left atrial or right atrial excursion. However, Group I patients had a thinner atrial septal aneurysm than did Group II patients. It is concluded that an atrial septal aneurysm occurs commonly in patients with unexplained stroke, is more frequently detected by transesophageal echocardiography than by surface echocardiography and is usually associated with right to left atrial shunting. Treatment (anticoagulant therapy vs. surgery) of atrial septal aneurysm identified in stroke patients can be determined only by long-term follow-up studies.

Adult↗
PubMed1991

Attenuation of myocardial ischemia during coronary occlusion by ultrashort-acting beta adrenergic blockade.

To assess the effect of the ultrashort-acting beta blocker esmolol on ischemia induced by acute coronary occlusion, we studied 16 patients undergoing coronary angioplasty. Doppler echocardiography and ECG monitoring were performed continuously before, during, and after balloon occlusion in the drug-free state and during esmolol infusion. Fourteen of the 16 patients had ST segment elevation during balloon inflation. However, maximal ST segment elevation (2.1 +/- 1.5 mm vs 1.7 +/- 1.3 mm, p less than 0.001) and duration of ST segment elevation (68 +/- 20 seconds vs 54 +/- 19 seconds, p less than 0.05) were both significantly reduced during esmolol infusion. Furthermore, the decrease in ejection fraction seen during drug-free balloon occlusions was significantly blunted during esmolol infusion. In the baseline state ejection fraction decreased from 55% to 38% (p less than 0.05) during coronary occlusion compared with a decrease from 52% to 49% (p = NS) during esmolol infusion. In addition, esmolol appeared to delay the onset of segmental wall motion abnormalities after coronary occlusion, occurring at a mean of 40 seconds after balloon inflation versus a mean of 31 seconds in the absence of beta blockade (p less than 0.05). Thus the use of ultrashort-acting beta blockade appears to diminish the extent and delay the onset of myocardial ischemia during acute coronary occlusion.

Adrenergic beta-Antagonists↗
PubMed1991

Ultra short-acting intravenous beta-adrenergic blockade as add-on therapy in acute unstable angina.

To assess the efficacy and safety of the ultra short-acting beta-blocking agent, esmolol, in acute unstable angina, we administered esmolol to 21 patients who had persistent angina despite conventional medical therapy. Following a baseline Doppler echocardiographic examination, esmolol was titrated to reduce the rate-pressure product by at least 20%. Once the patients had been receiving a maintenance dosage for 30 minutes, Doppler echocardiographic studies were repeated. Mean esmolol dose at target response was 17 +/- 16 mg/min, with the dosage range of 8 to 24 mg/min. Esmolol was effective in alleviating anginal chest pain in 18 of the 21 patients. Seven patients eventually underwent percutaneous transluminal coronary angioplasty (PTCA) and eight had coronary bypass surgery. The remainder were discharged receiving medical therapy including oral beta-blockade. During esmolol therapy, heart rate and blood pressure decreased significantly (86 +/- 14 to 68 +/- 12 beats/min and 125 +/- 16 to 103 +/- 20 mm Hg, both p less than 0.001). Cardiac output decreased from 5.4 +/- 1.3 to 4.5 +/- 1.1 L/min (p less than 0.001) secondary to a decrease in heart rate as stroke volume remained unchanged. Left ventricular ejection fraction increased from 47 +/- 12 to 49 +/- 13 with esmolol therapy, although this change was not statistically significant. Both the one third filling fraction as well as E/A ratio (ratio of early-to-late diastolic filling velocities) increased with esmolol therapy (35 +/- 8% to 38 +/- 8% and 0.73 +/- 0.2 to 0.85 +/- 0.23, both p less than 0.005), indicating improvement in left ventricular diastolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1991

The effects of high (sodium meglumine diatrizoate, Renografin-76) and low osmolar (sodium meglumine ioxaglate, Hexabrix) radiographic contrast media on diastolic function during left ventriculography in patients.

Although a majority of studies indicate superior hemodynamic and clinical profiles of low osmolar compared with high osmolar contrast media, the effect of these agents on diastolic left ventricular function has not been examined. We prospectively examined hemodynamic, electrocardiographic, and echocardiographic indices of left ventricular function in patients undergoing contrast ventriculography with a high osmolar, ionic, monomeric contrast, diatrizoate (Renografin-76) compared with a low osmolar, ionic, dimeric contrast, ioxaglate (Hexabrix). Thirty patients were randomized to each group. There were no clinical differences between the two groups. The decrease in systemic pressures was significantly greater with diatrizoate after left ventriculography (-38.5 +/- 3.5 versus -18.2 +/- 2.3, p less than 0.001) and selective left coronary angiography (-29.5 +/- 2.4 versus -17.4 +/- 2.6, p less than 0.001). In addition, left ventricular end-diastolic pressure increased significantly more with diatrizoate (7.3 +/- 0.9 versus 2.7 +/- 0.8 mm Hg for ioxaglate, p less than 0.001). QT interval prolongation occurred in both patient groups. Diatrizoate decreased systemic vascular resistance, and increased cardiac output and left ventricular ejection fraction more than ioxaglate, while simultaneously increasing left ventricular end-diastolic volume and altering the peak atrial filling velocity. Negative dp/dt (p less than 0.05), but not Tau, computed by the logarithmic or derivative methods, was reduced by diatrizoate. These data indicate that significant alteration of diastolic filling patterns occurs with high osmolar compared with low osmolar contrast agents. Although the clinical significance of this observation is currently unknown, these data further support the reported hemodynamic superiority of the low osmolar, dimeric contrast agent ioxaglate during contrast angiography.

Contrast Media↗
PubMed1991

Effects of aging on left ventricular structure and function.

To better characterize the cardiac structural and functional changes that are associated with aging, Doppler-echocardiography was performed on 23 young (mean age, 25 years) and 30 old (mean age, 70 years) healthy normotensive subjects. Left ventricular cavity dimensions and wall thickness were determined and left ventricular mass index was calculated from M-mode echocardiograms. Stroke volume was calculated from Doppler-measured aortic flow. Diastolic filling was evaluated by pulsed Doppler echocardiography of mitral inflow. Posterior wall thickness (1.0 vs 0.8 cm, p less than 0.05) and relative wall thickness (0.42 vs 0.35, p less than .05) were significantly greater in the elderly subjects compared with the younger subjects. Left ventricular mass index increased on average 0.25 gm/m2/yr but was not significantly increased in the elderly compared with the younger subjects (89 vs 77 gm/m2). Shortening fraction and stroke volume did not differ between the two groups. Diastolic filling was dramatically altered with aging, and the elderly subjects demonstrated a doubling of percent atrial contribution (37% vs 19%, p less than 0.0001) and halving of peak early-to-peak atrial velocity ratio (0.85 vs 1.77, p less than .01).

Adult↗
PubMed1991

Effects of electrophysiologic testing of the automatic implantable cardioverter-defibrillator on left ventricular systolic function and diastolic filling.

We investigated the effects of electrophysiologic testing of the automatic implantable cardioverter-defibrillator (AICD) on left ventricular systolic function and diastolic filling in 12 patients. Ventricular tachycardia or ventricular fibrillation was induced by programmed electrical stimulation and alternating-current, respectively. Patients were studied before and immediately after, 10 minutes after, and 1 hour after defibrillation by the AICD using M-mode, two-dimensional, and pulsed Doppler echocardiography. Immediately after defibrillation, increases were found in the peak early filling velocity (70 +/- 10 cm/sec to 84 +/- 24 cm/sec, p less than 0.01), peak early-to-atrial filling velocity ratio (1.05 +/- 0.21 to 1.29 +/- 0.26, p less than 0.005), and maximum rate of diastolic chamber enlargement (82 +/- 26 mm/sec to 102 +/- 44 mm/sec, p less than 0.05). These changes were not evident at 10 minutes and 1 hour. Cardiac output and ejection fraction were unchanged after defibrillation. Heart rate and diastolic filling time were unchanged. We conclude that electrophysiologic testing of the AICD does not impair left ventricular function in the immediate to 1-hour period after defibrillation. Left ventricular systolic function is unchanged and diastolic filling is enhanced.

Cardiac Pacing, Artificial↗
PubMed1991

Pathophysiology of isolated systolic hypertension in elderly patients: Doppler echocardiographic insights.

Systemic hemodynamics were evaluated with aortic pulsed wave Doppler echocardiography in 79 elderly subjects with isolated systolic hypertension participating in the Systolic Hypertension in the Elderly Program (SHEP) and were compared with the values in 39 normal age-matched subjects. Cardiac output was elevated (4.50 +/- 1.13 L/min versus 3.94 +/- 1.12 L/min, p less than 0.05) in patients with isolated systolic hypertension in comparison with values in normal elderly subjects. Systemic vascular resistance did not differ between both groups (2140 +/- 536 dyn.sec/cm-5 versus 2011 +/- 553 dyn.sec/cm-5, p = NS). The mean acceleration of blood during left ventricular ejection was similar in patients with isolated systolic hypertension in comparison with normals (12.6 +/- 5.6 m/sec2 versus 11.5 +/- 3.5 m/sec2, p = NS). Patients with isolated systolic hypertension had significantly decreased arterial compliance, as measured by the stroke volume-to-pulse pressure ratio (0.77 +/- 0.26 cm3/mm Hg versus 1.11 +/- 0.30 cm3/mm Hg, p less than 0.0001). The prevalence of aortic and mitral regurgitation as well as valvular and annular calcification did not differ between analyzed groups. Isolated systolic hypertension in elderly patients appears to be multifactorial, with reduced arterial compliance and increased cardiac output both playing a role.

Aged↗