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D S Bach

Publications and source records attributed to D S Bach.

66 records · Page 4Linked to original sources
PubMed1993

Paradoxic hypotension during dobutamine stress echocardiography: clinical and diagnostic implications.

OBJECTIVES: The purpose of this study was to elucidate the prevalence, magnitude and clinical implications of a hypotensive response during dobutamine stress echocardiography. BACKGROUND: Dobutamine stress echocardiography is an accurate noninvasive method for detecting coronary artery disease. It has been associated with unexpected hypotension in a proportion of patients. Hypotension occurring during exercise testing has been associated with an increased prevalence of multivessel coronary artery disease and a poor prognosis. The clinical significance of hypotension when seen during dobutamine infusion for diagnostic testing is unknown. METHODS: Clinical characteristics, coronary artery anatomy (n = 41), ventricular function at rest and during dobutamine infusion and prognosis were evaluated in 115 patients experiencing hypotension during dobutamine stress echocardiography and compared with data in 59 nonhypotensive catheterized patients for comparison of coronary anatomy and in 239 nonhypotensive patients for prognostic purposes. RESULTS: Hypotension occurred in 115 (20%) of 568 consecutive patients studied with dobutamine stress echocardiography. It was gradual in 73 and precipitous in 42 patients. There were no statistical differences among the hypotensive groups and the index group in prevalence or severity of coronary disease or in prognosis during 15 months compared with findings in nonhypotensive patients. CONCLUSIONS: Hypotension occurs commonly during dobutamine stress echocardiography, and patients with dobutamine-induced hypotension constitute a heterogeneous group. Unlike hypotension occurring with exercise testing, dopamine-induced hypotension is not invariably associated with advanced coronary disease or an adverse prognosis.

Adult↗
PubMed1992

Shock-wave thrombus ablation, a new method for noninvasive mechanical thrombolysis.

Successful experimental and clinical experience with thrombus ablation has been attained with high-power acoustic energy delivered in a catheter. The goal of this study was to investigate the feasibility of noninvasive thrombus ablation by focused high-power acoustic energy. The source for high-power acoustic energy was a shock-wave generator in a water tank equipped with an acoustic lens with a fixed focal point at 22.5 cm. Thrombus was prepared in vitro, weighed (0.24 +/- 0.08 g), and inserted in excised human femoral artery segments. The arterial segments wer ligated, positioned at the focal point and then randomized into either test (n = 8) or control (n = 7). An x-ray system verified the 3-dimensional positioning of the arterial segment at the focal point. A 5 MHz ultrasound imaging system continuously visualized the arterial segment at the focal point before, during and after each experiment. The test segments were exposed to shock waves (1,000 shocks/24 kv). The arterial segment content was then flushed and the residual thrombus weighed. The arterial segment and thrombus were fixed and submitted to histologic examination. The test group achieved a significant ablation of thrombus mass (0.25 +/- 0.15 vs 0.07 +/- 0.003 g; p = 0.0001) after application of shock waves. Arterial segments showed no gross or microscopic damage. Ultrasound imaging revealed a localized (1.9 +/- 0.5 cm2), transient (744 +/- 733 ms), cavitation field at the focal point at the time of application of focused shock waves. Thus, focused high-power acoustic energy can effect noninvasive thrombus ablation without apparent damage to the arterial wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Femoral Artery↗
PubMed1992

Dobutamine stress echocardiography.

Two-dimensional echocardiography is a versatile, accurate, and readily available method for the assessment of cardiac anatomy and function, and extensive experience has been gained in the analysis of left ventricular wall motion. Using modern imaging techniques, regional as well as global wall motion analysis can be performed. Echocardiography can be used in conjunction with a protocol for either exercise or pharmacologic cardiovascular stress in order to identify the distribution and severity of coronary artery disease, with the induction of a regional wall motion abnormality being a sign of myocardial ischemia. The use of dobutamine infusion to accomplish stress echocardiography is a safe, accurate, and practical method for the diagnosis of coronary artery disease in patients unable to exercise. In addition to the evaluation of inducible ischemia, preliminary work is being performed with dobutamine stress echocardiography for the assessment of risk and patient prognosis following acute myocardial infarction and as an indication of tissue viability for myocardium that remains dysfunctional at rest following thrombolytic therapy.

Coronary Disease↗
PubMed1986

Prognostic significance of vegetations detected by two-dimensional echocardiography in infective endocarditis.

Although 2DE is considered the most sensitive method for detecting vegetations in infective endocarditis, the independent clinical significance of these vegetations continues to be debated. To further examine this, we identified 74 patients who were diagnosed as having infective endocarditis over a 54-month period. The 50 patients who underwent 2DE examination form the basis of this report. Definite vegetations were present in 21 (42%) patients and measured 1.2 +/- 0.2 cm2. The vegetation was localized to the aortic valve in 10 patients, the mitral valve in eight, and the tricuspid valve in three. A major complication, defined as death, new-onset congestive heart failure, major arterial embolus, or valve surgery occurred in 86% of the vegetative endocarditis patients compared to 62% of those without vegetations. Among those patients with vegetations, death occurred in 24%, heart failure in 38%, arterial embolus in 48%, and surgery in 43%. This compared to 7%, 21%, 21%, and 24%, respectively, in those patients without vegetations. These data support the concept that 2DE detection of a vegetation defines a high-risk subgroup of patients with infective endocarditis in whom careful monitoring and aggressive management are warranted.

Adult↗
PubMed1984

Biochemical characterization of human eosinophil Charcot-Leyden crystal protein (lysophospholipase).

Lysophospholipase from human eosinophils is a protein previously considered based upon antigenic, enzymatic, and electrophoretic similarities to be the single component of Charcot-Leyden crystals, which are formed in vivo in association with eosinophilic diseases. The identity of eosinophil lysophospholipase and solubilized Charcot-Leyden crystal protein is now established by biochemical criteria, and a basis for the ease of aggregation and crystallization of the protein is identified in its prominent hydrophobicity. Chromatographically purified enzyme and Charcot-Leyden crystal protein formed in vitro functioned as lysophospholipases with identical Michaelis constants (Km approximately equal to 22 microM) for the substrate lysopalmitoylphosphatidylcholine and had blocked amino-terminal residues and almost identical amino acid compositions. The propensity of lysophospholipase to aggregate was not due to extensive intermolecular disulfide bonding because it contained a single cysteine residue as assessed by amino acid analyses and incorporated 0.986 mol of p-chloromercuribenzoic acid/mol of native enzyme or 0.958 mol of iodoacetic acid/mol of reduced and denatured enzyme. By equilibrium dialysis, lysophospholipase bound 3.820 g of detergent/g of protein in 1% sodium dodecyl sulfate and 0.506 g of detergent/g of protein in 10 mM sodium deoxycholate. In addition, monomeric protein demonstrated enhanced binding of detergent as evidenced by its aberrantly rapid electrophoretic mobility in 1%, but not 0.1%, sodium dodecyl sulfate. The hydrophobic nature of this protein, which accounts for 10% of the protein of the eosinophil, may contribute to its unique propensity for crystallization in vivo.

Amino Acids↗
PubMedDate not supplied

Stress echocardiography for evaluation of hemodynamics: valvular heart disease, prosthetic valve function, and pulmonary hypertension.

A broad variety of diseases can affect dynamic cardiac function and contribute to exertional symptoms. Although hemodynamic data at rest may be sufficient to guide therapy in some patients with cardiovascular disease, medical and surgical decisions may be impacted by the cardiac response to stress and the ability to associate exertional symptoms with cardiac hemodynamic response. Stress echocardiography/ Doppler provides a unique noninvasive means to evaluate cardiovascular function and ehmodynamic responses during increased cardiac work. Specifically, stress echocardiographic/Doppler imaging allows assessment of the response to exercise of left and right ventricular function, transvalvular and prosthetic valve gradients, and right ventricular systolic pressure. It has substantial clinical use in the evaluation of patients with equivocal evidence of mitral stenosis, suspicion of dynamic mitral insufficiency or prosthetic valve dysfunction, aortic stenosis and impaired left ventricular systolic function, diseases associated with pulmonary hypertension or cor pulmonale, and among patients with dyspnea of unknown origin. The dynamic nature of cardiovascular disease and the broad spectrum of diseases that affect cardiac function make exercise echocardiography/Doppler an ideal tool ideal for the noninvasive assessment of patients with symptoms of exertional dyspnea.

Echocardiography↗
PubMedDate not supplied

Management of specific medical conditions in the perioperative period.

Patients with a variety of medical conditions known to increase cardiovascular risk may require noncardiac surgery. After a preoperative assessment of risk, specific attention to medical therapy may be indicated in the perioperative period. The perioperative period begins before surgery when routine medical therapy may be interrupted, and continues through the surgical procedure and convalescence. During these times, the surgical patient is exposed to increased risks related to the underlying disease process prompting surgery, stresses associated with anesthesia, surgical intervention and postoperative discomfort, and alterations in usual medical therapy. With careful attention to risks specific to an underlying medical condition, patient monitoring and medical management in the perioperative period can be modified to prevent or minimize the impact of an adverse cardiac event.

Heart Diseases↗
PubMedDate not supplied

Intracoronary and aortic root myocardial contrast echocardiography: the effect of route, dose, and pharmacologic coronary vasodilation.

Myocardial contrast echocardiography is useful for the assessment of myocardial perfusion but has required direct intracoronary injections. Aortic root myocardial contrast echocardiography has the potential advantage of allowing simultaneous assessment of multiple perfusion beds, as well as evaluating competitive and collateral flows. This study assessed the safety and efficacy of intracoronary and aortic root injections of sonicated 5% human serum albumin (Albunex) with and without concomitant coronary vasodilation. Without vasodilation, 72% of intracoronary injections had optimal myocardial enhancement, compared with 21% of aortic root injections. For individual patients, significant dose-response relationships existed for both intracoronary and aortic root injections, although contrast intensity for a given dose varied between patients. Pharmacologic vasodilation resulted in significant increases in contrast intensity and in the incidence of optimal myocardial contrast after aortic root injections. Aortic root myocardial contrast echocardiography potentially allows the simultaneous assessment of multiple perfusion beds through a route somewhat less invasive than that of direct intracoronary injections.

Adult↗
PubMedDate not supplied

Impact of B-mode color encoding on rapid detection of ultrasound targets: an in vitro study.

The purpose of this study was to assess the impact that new B-Mode color encoding schemes have on an observer's ability to rapidly detect ultrasound targets in an in vitro system. Four phantoms were created with five-, six-, or seven-tissue-density objects. Each phantom was scanned in routine grey scale (256 grey levels) and in three different color encoding algorithms. A test tape containing 3- and 5-second exposures, in random order, to the different phantoms recorded in grey and B-mode color was then prepared and viewed by 21 observers. Results were tabulated as the mean number of absolute errors in object recognition, per observer, per scan, for both the 3- and 5-second exposures. Each color scheme reduced observer detection error rates compared with error rates with grey scale recordings when viewed for 3 seconds. There was no reduction in error rates when 5-second exposures were viewed. We conclude that in an in vitro system, new B-mode color encoding schemes may facilitate rapid and accurate detection of soft-tissue targets.

Adipose Tissue↗
PubMedDate not supplied

Spectrum of acute dissection of the ascending aorta: a transesophageal echocardiographic study.

Transesophageal echocardiography is an accurate tool for the immediate diagnosis of acute aortic dissection. In addition to establishing the diagnosis of dissection, transesophageal echocardiography provides determination of its extent and detection of complications. The purpose of this study was to delineate the full spectrum of abnormalities present in acute dissection of the ascending aorta as assessed by transesophageal echocardiography. Forty consecutive patients with acute ascending aortic dissection were evaluated. Specific attention was paid to complications of aortic valve insufficiency, pericardial effusion, and left ventricular wall motion abnormalities. The aortic arch and the descending aorta were also evaluated for involvement. Quantitative data included measurement of the aorta at the anulus, sinuses, and tubular portion, as well as the proximal and distal descending aortas. An intimal flap was identified in all patients. This was a simple linear tear in 22 patients (55%) and circumferential in eight (20%). A complex tear was noted in 10 patients (25%). The majority of patients (n = 30; 75%) had extension of the dissection into the descending thoracic aorta. At least one communication between the true and false lumens ("entrance point") was identified in 31 patients (78%). Pericardial effusions were noted in 19 patients (48%), only two of whom had a moderate-size effusion. Moderate or severe aortic insufficiency was seen in 18 patients (45%) and regional wall motion abnormalities in six patients. We conclude that acute dissection of the ascending aorta results in a complex or convoluted flap rather than a simple linear tear in many patients. The complication of clinically significant pericardial effusion was rare. Aortic insufficiency is common and can be attributed to multiple mechanisms.

Acute Disease↗