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Biomedical subjects

M D Tischler

Publications and source records attributed to M D Tischler.

35 records · Page 2Linked to original sources
PubMed1994

Validation of global and segmental left ventricular contractile function using gated planar technetium-99m sestamibi myocardial perfusion imaging.

OBJECTIVES: The purpose of this study was to test the hypothesis that segmental wall motion analysis determined from gated planar technetium-99m sestamibi myocardial imaging is reproducible and agrees well with echocardiographic data. BACKGROUND: Technetium-99m sestamibi is a new radiopharmaceutical recently approved for myocardial perfusion imaging. Its advantages include a dosimetry that allows use of a dose 10 to 15 times higher than that of thallium-201. As a result, myocardial counts are markedly improved and images can be collected in a gated mode to potentially allow assessment of global and segmental ventricular function. However, the reproducibility and accuracy of technetium-99m sestamibi imaging for measurement of global and segmental left ventricular function have not been evaluated or compared with those of a standard ventricular function technique, such as echocardiography. METHODS: We studied 136 patients referred for clinical technetium-99m sestamibi imaging. One-day rest-stress planar technetium-99m sestamibi protocols were used, gating the stress images. After technetium-99m sestamibi imaging, all patients had standard rest two-dimensional echocardiography. Global and segmental technetium-99m sestamibi and echocardiographic left ventricular contraction was graded qualitatively as normal or abnormal using a four-point grading system. RESULTS: Interobserver and intraobserver agreement was extremely high for global and segmental technetium-99m sestamibi wall motion analysis, with absolute agreements ranging from 0.92 to 1.00 and corresponding kappa values of 0.74 to 1.00 (p < 0.00001). Agreement with global and segmental echocardiographic wall motion was similarly very high, with absolute agreements ranging from 0.93 to 1.00 and corresponding kappa values of 0.75 to 1.00 (p < 0.00001). CONCLUSIONS: Gated technetium-99m sestamibi cardiac imaging provides information with regard to rest global and segmental left ventricular systolic function that is highly reproducible and agrees very well with results of two-dimensional echocardiography.

Adult↗
PubMed1994

Mitral valve replacement versus mitral valve repair. A Doppler and quantitative stress echocardiographic study.

BACKGROUND: Standard mitral valve replacement (MVR) in patients with chronic mitral regurgitation results in consistent reductions in resting postoperative ejection fraction. This has been attributed to removal of the low-impedance ejection pathway into the left atrium or to disruption of the chordal apparatus. Mitral valve repair (MVP) does not reduce ejection fraction at rest. However, whether MVP confers any advantages with regard to dynamic left ventricular performance has not been investigated. The aim of this study was to directly compare standard MVR with MVP and to determine their respective influences on ventricular ejection performance during bicycle exercise. METHODS AND RESULTS: Ten consecutive patients with pure chronic mitral regurgitation who underwent MVP and 10 patients matched for age, sex, and preoperative ejection fraction who underwent standard MVR for pure chronic mitral regurgitation performed symptom-limited, graded upright bicycle exercise with simultaneous Doppler and quantitative two-dimensional echocardiography. Patients with MVP had significantly greater rest (55 +/- 12%) and exercise (63 +/- 11%) ejection fractions than matched patients with MVR (40 +/- 13% [P < .0001] and 42 +/- 17% [P < .005], respectively). End-systolic circumferential wall stress was significantly lower at rest (190 +/- 36 versus 244 +/- 46; P < .03) and at peak exercise (231 +/- 46 versus 300 +/- 52; P < .02) in patients with MVP. At peak exercise, left ventricular shape was significantly more spherical in patients with MVR than those with MVP (1.84 +/- 0.31 versus 2.45 +/- 0.59; P < .02). CONCLUSIONS: MVR with chordal transection resulted in significant reductions in rest and exercise ejection fraction. This was caused in part by a significant increase in end-systolic circumferential wall stress. MVP resulted in improved rest and exercise ejection indexes, primarily due to a marked reduction in end-systolic stress and maintenance of a more ellipsoidal chamber geometry.

Echocardiography, Doppler↗
PubMed1993

Relation between left ventricular shape and exercise capacity in patients with left ventricular dysfunction.

OBJECTIVES: The aim of this study was to identify dynamic predictors of exercise duration in patients with systolic left ventricular dysfunction and to test the hypothesis that left ventricular shape is an independent determinant of exercise duration in these patients. BACKGROUND: Measurements of left ventricular volumes and ejection fraction at rest do not predict exercise capacity in patients with systolic left ventricular dysfunction. Left ventricular shape at rest has been reported to be an independent determinant of exercise duration in these patients. The significance of alterations in left ventricular shape that occur during dynamic exercise has not been investigated. METHODS: Twenty-one patients with a documented ejection fraction < 40% performed symptom-limited graded upright bicycle exercise with simultaneous quantitative two-dimensional echocardiography. End-diastolic volume, end-systolic volume, stroke volume, ejection fraction and sphericity index were measured at rest and peak exercise. RESULTS: Eleven patients exercised beyond stage II (6 min, 50 W), averaging 8.9 +/- 1.9 min; 10 patients were unable to complete stage II, averaging 4.9 +/- 0.9 min. No patient developed clinical evidence of ischemia during the exercise period. Of the echocardiographic variables considered, only end-systolic and end-diastolic sphericity indexes at peak exercise (r = 0.809 and 0.711, respectively) and the change in end-systolic sphericity index during exercise (r = 0.697) were strongly correlated with exercise duration. CONCLUSIONS: Conventional descriptors of left ventricular function are poor predictors of exercise capacity. Dynamic changes in heart shape correlate strongly with exercise duration and may be important determinants of exercise capacity in patients with systolic left ventricular dysfunction.

Adult↗
PubMed1993

Exercise echocardiography in combined mild mitral valve stenosis and regurgitation.

Dynamic mitral regurgitation (MR) is typically associated with either severe systolic left ventricular dysfunction or episodes of acute myocardial ischemia. We report three patients with mild combined mitral stenosis and regurgitation and normal global left ventricular systolic function who presented with severe exertional dyspnea. Upright bicycle exercise echocardiography revealed development of severe dynamic MR in all three cases with Doppler evidence of severe pulmonary hypertension. There was no echocardiographic or electrocardiographic evidence of ischemia. Exercise echocardiography is an established tool for assessing dynamic changes in transvalvar pressure gradients. These results suggest that exercise echocardiography may also be useful for evaluating changes in severity of MR and for the assessment of dynamic changes in pulmonary artery systolic pressures.

Aged↗
PubMed1993

Increased left ventricular mass after thoracotomy and pericardiotomy. A role for relief of pericardial constraint?

BACKGROUND: Myocardial stretch and increased ventricular filling can lead to increased rates of myocardial protein synthesis. In animal studies, left ventricular mass increases after pericardiectomy, suggesting relief of a biologically meaningful restraining role and a resultant stimulus for growth. The present study was designed to test the hypothesis that combined thoracotomy and pericardiotomy leads to left ventricular hypertrophy in patients with normal left ventricular ejection fraction undergoing elective bypass surgery. METHODS AND RESULTS: Twenty-five patients with normal left ventricular ejection fraction without active myocardial ischemia underwent Doppler and quantitative two-dimensional echocardiography 1 day before and 6 weeks and 7 months after elective coronary artery bypass surgery. The pericardium was left widely incised in all patients. Left ventricular end-systolic volume, end-diastolic volume, stroke volume, ejection fraction, end-systolic circumferential wall stress, and mass were measured. Left ventricular end-diastolic volume index increased from 51 +/- 11 mL/m2 to 62 +/- 14 mL/m2 (p < 0.05) at 6 weeks and to 66 +/- 14 mL/m2 (p < 0.05 versus baseline, p = NS versus 6 weeks) at 7 months. Left ventricular mass index increased from 109 +/- 23 g/m2 to 127 +/- 24 g/m2 (p < 0.05) at 6 weeks and to 131 +/- 23 g/m2 (p < 0.05 versus baseline, p = NS versus 6 weeks) at 7 months. There were no changes in systolic or diastolic blood pressures, end-systolic circumferential wall stress, or end-systolic volume. CONCLUSIONS: Patients with normal left ventricular ejection fraction develop increases in left ventricular end-diastolic volume and mass after coronary artery bypass surgery. These findings support the hypothesis that the increase in left ventricular end-diastolic volume associated with thoracotomy and pericardiotomy leads to myocardial growth and an increase in left ventricular mass.

Coronary Artery Bypass↗
PubMed1992

Serial assessment of left ventricular function and mass after orthotopic heart transplantation: a 4-year longitudinal study.

Long-term changes in left ventricular performance and geometry in the transplanted human heart have been incompletely described. Therefore, two-dimensional echocardiograms were performed on 22 recipients of an orthotopic heart transplant at 1 month (32 +/- 20 days), 1 year (11 +/- 3 months) and 4 years (54 +/- 9 months) after transplantation. All studies were performed at a time when the patient had no pathologic evidence of rejection. Ten healthy men served as a normal control group. Over 4 years of follow-up, mean systolic blood pressure in the study patients increased from 121 +/- 12 (p = NS vs. values in the control group) to 139 +/- 11 mm Hg (p less than 0.05 vs. both control values and values at 1 month); mean diastolic blood pressure increased from 72 +/- 7 (p = NS vs. normal values in the control group) to 93 +/- 8 mm Hg (p less than 0.05 vs. both control values and values at 1 month). Left ventricular end-systolic volume increased from 42 +/- 10 (p = NS vs. control values) to 51 +/- 14 ml (p less than 0.05 vs. both control values and values at 1 month) and end-diastolic volume increased from 103 +/- 28 (p = NS vs. control values) to 112 +/- 27 ml (p less than 0.05 vs. control values) over 4 years. Left ventricular mass and ejection fraction did not change significantly within the patient cohort and remained similar to that found in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1991

Effects of percutaneous mitral valvuloplasty on left ventricular mass and volume.

The response of left ventricular (LV) geometry to altered loading conditions after mitral valvuloplasty has been incompletely described. Therefore, 15 patients with rheumatic mitral stenosis were studied using quantitative 2-dimensional echocardiography a mean of 1 +/- 2 months before and 11 +/- 5 months after percutaneous balloon mitral valvuloplasty. Mitral valve area (Gorlin) increased in all patients, from 1.0 +/- 0.3 to 1.9 +/- 0.5 cm2 (p less than 0.01). Mitral regurgitation (1+/4+) developed in 3 patients, and increased by 1 grade in 1 patient as a consequence of mitral valvuloplasty. After valvuloplasty, there were significant increases in LV end-diastolic volume (69 +/- 22 to 82 +/- 26 ml, p less than 0.01), stroke volume (34 +/- 13 to 46 +/- 19 ml, p less than 0.05) and mass (181 +/- 46 to 200 +/- 42 ml, p less than 0.005). LV end-systolic volume and ejection fraction did not change significantly. LV mass-to-volume ratio was unchanged (5.6 +/- 1.5 to 5.8 +/- 1.4 g/ml, p = not significant). Quantitatively similar results were obtained when these changes were indexed to body surface area. Thus, successful mitral valvuloplasty was associated with significant increases in LV end-diastolic volume and mass. These findings suggest that increased preload may be a stimulus to myocardial growth.

Aged↗
PubMed1991

Prediction of major cardiac events after peripheral vascular surgery using dipyridamole echocardiography.

Patients undergoing peripheral vascular surgery are at increased risk of postoperative cardiac complications. To evaluate the role of dipyridamole echocardiography in predicting major cardiac events, 109 unselected patients undergoing elective peripheral vascular surgery were prospectively studied. Preoperative dipyridamole echocardiograms were interpreted by an echocardiographer unaware of all clinical data. Patients were followed up until hospital discharge by research physicians without knowledge of dipyridamole echocardiography results. Outcomes were classified using strict predefined criteria by reviewers unaware of other clinical and echocardiographic data. Of the 109 patients, 9 (8%) had positive studies defined as development of new regional wall motion abnormalities or worsening of preexistent wall motion abnormalities. Of these 9 patients, 7 had postoperative events, including 3 cardiac deaths, 1 nonfatal myocardial infarction, 2 with unstable angina, and 1 with pulmonary edema. Only 1 event occurred among the 100 patients with negative studies. The sensitivity and specificity of dipyridamole echocardiography for predicting cardiac events after vascular surgery were 88 and 98%, respectively; the positive and negative predictive values were 78 and 99%. The relative risk of having a cardiac event if dipyridamole echocardiography was abnormal was 78 (95% confidence interval, 11 to 564; p less than 0.0001). If these results are extended and confirmed by other investigators, preoperative dipyridamole echocardiography may be an important screening test for patients undergoing elective peripheral vascular surgery.

Aged↗
PubMed1990

Clinical, echocardiographic and Doppler correlates of clinical instability with onset of atrial fibrillation.

To identify clinical and Doppler echocardiographic correlates of instability with the onset of atrial fibrillation (AF), 87 consecutive patients with new-onset AF who had echocardiograms recorded during that hospital admission while in sinus rhythm were studied. Reviewers who were blinded to echocardiographic and Doppler data classified 51 patients (59%) as unstable because of the development of angina, congestive heart failure, syncope or hypotension with the onset of AF. Echocardiographic and Doppler data on transmitral blood flow velocity were analyzed by a single reviewer who was blinded to other clinical data. Multiple logistic regression analysis identified 3 variables as independent predictors of clinical instability with the onset of AF: (1) history of prior myocardial infarction (p less than 0.02); (2) echocardiographic evidence of left ventricular dysfunction (p less than 0.03); and (3) Doppler evidence of increased atrial filling fraction (p less than 0.0001). An atrial filling fraction threshold of 0.40 had a sensitivity for predicting clinical instability of 80% and a specificity of 72%. These data are consistent with the hypothesis that patients who are more dependent on the atrial contribution to ventricular filling are at increased risk of instability with AF due to the loss of atrial systole.

Aged↗
PubMed1983

A visual pathway that mediates fear-conditioned enhancement of acoustic startle.

Eighty rats received 10 light-shock pairings on two successive days. Seventy-two h after the final training session, subjects received lesions directed at the primary visual areas (deep and superficial layers of the superior colliculus, dorsal lateral geniculate nucleus, pretectal nuclei, visual cortex and thalamic reticular nucleus) and at the nuclei of the lateral lemniscus and reticularis pontis caudalis, proposed components of a primary acoustic startle circuit in the rat. Control animals were sham operated. One day later, all animals were tested for startle by presenting noise bursts of 3 different intensities in the presence or absence of the light conditioned stimulus. Potentiated startle (the difference between light-noise vs noise-alone trials) was significantly attenuated or eliminated by lesions directed at the dorsal nucleus of the lateral geniculate, deep layers of the superior colliculus, visual cortex, and the posteroventral region of the nucleus of the lateral lemniscus. Lesions directed at pretectal nuclei, superficial layers of the superior colliculus, thalamic reticular nucleus, nucleus reticularis pontis caudalis or dorsal nucleus of the lateral lemniscus did not attenuate potentiated startle. The results suggest that the visual pathway that mediates potentiated startle goes from the retina to the dorsal lateral geniculate nucleus to visual cortex to deep layers of superior colliculus and down to the postero-ventral region of the lateral lemniscus where acoustic startle is modulated.

Acoustic Stimulation↗
PubMed1982

A primary acoustic startle circuit: lesion and stimulation studies.

The latency of the acoustic startle reflex in the rat is 8 msec, measured from tone onset to the beginning of the electromyographic response in the hindleg. This extremely short latency indicates that only a few synapses could be involved in some primary acoustic startle circuit. Acoustic startle is being used as a model system for studying habituation, sensitization, prepulse inhibition, classical conditioning, fear or anxiety, and drug effects on behavior. The present study attempted to delineate a short latency acoustic startle circuit, since this would provide critical information for further study in all of these areas. Bilateral lesions of the ventral cochlear nucleus, which receives the primary auditory input, abolish acoustic startle. Electrical, single pulse stimulation of the ventral cochlear nucleus elicits startle-like responses with a latency of about 7 msec. Bilateral lesions of the dorsal and ventral nuclei of the lateral lemniscus, which receive direct input from the ventral cochlear nuclei, abolish acoustic startle. Electrical stimulation of these nuclei elicits startle-like responses with a latency of about 6 msec. Bilateral lesions of ventral regions of the nucleus reticularis pontis caudalis, which contain cell bodies that give rise to the reticulospinal tract, abolish acoustic startle. Electrical stimulation of these points elicits startle-like responses with a latency of about 5 msec. Reaction product from horseradish peroxidase iontophoresed into this area is found in the nuclei of the lateral lemniscus. In contrast, lesions of the dorsal cochlear nuclei, vestibular nuclei, nucleus reticularis pontis oralis, nucleus reticularis gigantocellularis, and dorsal regions of the nucleus reticularis pontis caudalis fail to abolish acoustic startle. Also, "startle" cannot be elicited electrically from these areas. The data suggest that a primary acoustic startle circuit in the rat consists of auditory nerve, ventral cochlear nucleus, nuclei of the lateral lemniscus, nucleus reticularis pontis caudalis, spinal interneuron, lower motor neuron, and muscles. Hence, five synapses, plus the neuromuscular junction, are probably involved.

Acoustic Stimulation↗
PubMedDate not supplied

Extraskeletal Ewing's sarcoma of primary cardiac origin.

A 13-year-old boy presented with cardiac tamponade. Echocardiography revealed a large mass extending from the right and left ventricles into a large pericardial effusion. Pathology confirmed the first reported case of a primary cardiac extraskeletal Ewing's sarcoma.

Adolescent↗