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Biomedical subjects

F M Baer

Publications and source records attributed to F M Baer.

At least 19 recordsLinked to original sources
PubMed2005

[Early diagnosis of the functional relevance of coronary heart disease].

In cases of stable or to a large extent symptom-free coronary heart disease (CHD) and atypical symptomatology, the indication for diagnostic cardiac catheterization is first confirmed by noninvasive diagnostics of ischemia. This can be carried out either with ergometric stress tests or imaging procedures in combination with ergometric or pharmacological stress. Myocardial scintigraphy and stress echocardiography are established techniques and to an increasing extent stress magnetic resonance imaging (MRI). In addition to sensitivity in providing evidence for ischemia, technical improvements in computed tomography (CT) and MRI have opened up new possibilities for visualizing coronary vessels and vascular wall morphology. While CT coronary angiography with its high spatial resolution is on the threshold of clinical application for selected patients, MRI has the potential for furnishing information on wall movement analysis, perfusion, coronary flow measurement, and plaque characterization to become the future cardiovascular "all-round examination".

Coronary Artery Disease↗
PubMed2004

[Is endothelial dysfunction of practical relevance?].

Endothelial dysfunction is a "systemic disease" and a predictor of preclinical atherosclerosis. A relatively simple-to-perform and reliable diagnostic method of evaluating endothelial function is the measurement of the forearm blood flow (FBF). Unremarkable vasoreactivity of the brachial artery on performing FBF measurement is a prognostically favorable sign. This applies equally to patients with cardiovascular risk factors such as hypertension, hyperlipidemia or diabetes mellitus, and to patients with angina pectoris. A number of investigations suggest that cardiovascular endpoints can be significantly diminished by reducing the risk factors.

Acetylcholine↗
PubMed2004

[IKOP-Infection control in the operating theatreConsensus on the theme "Barrier measures during operations and invasive procedures"].

Postoperative surgical site infections remain frequent despite intensive control programs. With rising numbers of operations and invasive procedures in the outpatient setting and in immunocompromised patients, the prevention of wound infections presents a rapidly growing challenge to the medical community. Barrier measures including drapes and surgical gowns to prevent wound contamination, have clearly reduced the rate of wound infections. The optimal material characteristics for operating gowns and drapes are well defined, but there is still a long running controversy on the use of single-use versus reusable materials. We review the efficacy and ecological impacts of these different approaches. Currently no superiority of any of these approaches with regard to either efficacy or ecological impact can be found. The European Union has recently published a series of mandatory standards to specify material characteristics of barrier materials used in operating theatres (EN 13795). Their scope include production standards of these materials as well as specific processes in auditing their characteristics. The implementation of these norms will clearly present a challenge to European hospitals but will lead to better material characteristics in the end.

Europe↗
PubMed2004

Minimally invasive direct coronary artery bypass grafting: a systematic review.

AIM: Recently minimally invasive direct coronary artery bypass grafting (MIDCAB) has become an interesting alternative to conventional coronary artery bypass grafting, especially in patients with a high-grade left anterior descending coronary artery (LAD) stenosis unsuitable for balloon angioplasty. Although MIDCAB offers several advantages such as the avoidance of sternotomy and cardiopulmonary bypass, concerns have been raised about the technical accuracy of the anastomoses that can be performed on a beating heart. Therefore, clinical and angiographic outcomes after MIDCAB are the subject of current controversy. METHODS: A literature search for all published outcome studies of MIDCAB grafting was performed for the period from January 1995 through April 2003. Sixteen articles were enrolled in this review. The data presented in the studies was analysed with regard to clinical outcome and angiographic results. RESULTS: Early mortality ranged from 0% to 4.9% and late mortality (>30 days after MIDCAB) ranged from 0.3% to 12.6%. Infarct rates (non-fatal myocardial infarction) ranged between 0% and 3.1%. Intra- and postoperative complications (wound infections, reoperation for management of bleeding, arrhythmias, stroke, etc.) occurred in 1.6-40%. The conversion rate to sternotomy/cardiopulmonary bypass ranged between 0% and 6.2%. Reinterventions due to graft failure were necessary in up to 8.9% of patients (surgical revision or percutaneous transluminal coronary angioplasty, PTCA). Short-term and mid-term angiographic outcomes are given in Table I. CONCLUSION: Clinical outcomes and immediate graft patency after MIDCAB are acceptable. However, long-term follow-up results and further randomized prospective clinical trials comparing this new technique with standard revascularization procedures are needed.

Aged↗
PubMed2002

[Acute aortic syndrome. A thoracic emergency--unfortunately with a large selection of symptoms].

Acute aortic arch syndrome is a medical emergency associated with a high mortality rate. In view of the great variation in symptomatology, this condition can readily be overlooked. A carefully obtained history (pain!), a thorough physical examination (differences in pulse and blood pressure) may be suspicious for acute aortic arch syndrome, which today can be reliably and rapidly diagnosed by noninvasive imaging (CT, TEE). Confirmation of the suspected diagnosis must be followed by further intensive medical surveillance (Stanford B) or, in the event of involvement of the ascending aorta or aortic arch (Stanford A), referral without delay to a cardiosurgical center. Apart from a further shortening of the time lapse between diagnosis establishment and emergency surgery, new therapeutic (e.g. stenting) and surgical procedures may improve the prognosis of the syndrome. Maybe new diagnostic tools (monoclonal antibodies against aortic myosin and radio-immunoscintigraphy) will help to recognize the aortic syndrome more rapidly.

Acute Disease↗
PubMed2001

[Angiographically unexplained myocardial ischemia in high grade coronary stenosis with main stem involvement in intravascular ultrasound].

HISTORY AND ADMISSION FINDINGS: For seven weeks a 57-year-old man had been complaining of recurrent non-radiating retrosternal pain and pressure on slightest exertion. Admission physical examination was unremarkable except for evidence of peripheral vascular disease. Cardiovascular risk factors were hypertension, hyperlipoproteinaemia and obesity. INVESTIGATIONS: The resting ECG was unremarkable. Objective signs of myocardial ischaemia were produced in the exercise ECG (angina at 100 Watt, negative T waves in V2 to V6 and borderline S-T depression in V4). Myocardial scintigraphy showed reversible reduced perfusion of the anterior wall near the apex and also of the apex and septum. Left ventricular (LV) angiography demonstrated a normally contracting LV, while selective coronary angiogram revealed a 20% reduction in caliber of the proximal branch of the anterior interventricular branch (AIVB), with otherwise normal coronary arteries. Subsequent intravascular ultrasound (IVUS) showed a circular echo-poor 80% stenosis at the origin of the AIVB with extension to the main stem. TREATMENT AND COURSE: A bypass from the internal mammary artery to the AIVB and an aortocoronary venous bypass to the intermediate branch were performed. The patient was free of symptoms postoperatively. CONCLUSION: If cases where there is a discrepancy between clinical and coronary angiographic findings--the latter being unclear or inconsistent, especially in the area of the left main stem, bifurcations or vessel origin--IVUS may contribute decisively to demonstrating coronary anatomy or pathology, and to indicating the type of revascularizing measures.

Coronary Angiography↗
PubMed2001

Non-Q-wave myocardial infarction: impaired myocardial energy metabolism in regions with reduced 99mTc-MIBI accumulation.

Reduced regional technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) accumulation in patients with chronic non-Q-wave infarction (NQWI) but without significant coronary artery stenosis indicates non-transmural damage of the myocardial wall. The aim of this study was to characterise cardiac energy metabolism after NQWI using phosphorus-31 magnetic resonance spectroscopy (31P-MRS) and to compare the biochemical remodelling with changes in regional 99mTc-MIBI uptake and with morphological and functional parameters assessed by magnetic resonance imaging (MRI). Fifteen patients with a history of NQWI, exclusion of significant coronary artery stenosis (<50% diameter stenosis) and hypokinesia of the anterior wall (group A) were examined with 31P-MRS to study the effects of NQWI on myocardial energy metabolism. Spectroscopic measurements were performed in the infarct-related myocardial region. Corresponding gradient-echo MR images and myocardial 99mTc-MIBI single-photon emission tomography images were acquired for exact localisation of the infarct region. All examinations were performed at rest under anti-ischaemic medication. Data were compared with those of patients in whom coronary artery disease had been excluded by angiography (group B, n=10). All patients of group A displayed anterior wall hypokinesia in the infarcted area on both ventriculography and MRI, with a reduced myocardial accumulation of 99mTc-MIBI (66.3%+/-11.8% vs 95.6%+/-2.2% in group B). The mean wall thickness during the complete cardiac cycle (9.5+/-1.8 mm vs 13.1+/-1.1 mm in group B, P<0.001), the systolic wall thickening (2.6+/-1.4 mm vs 5.8+/-1.5 mm in group B, P<0.01) and the phosphocreatine/adenosine triphosphate ratio (1.12+/-0.22 vs 1.74+/-0.23 in group B, P<0.01) in the hypokinetic area were all significantly reduced. It is concluded that persisting hypokinetic myocardium after NQWI combined with reduced myocellular uptake of 99mTc-MIBI displays a reduced PCr/ATP ratio. Our results indicate that morphological remodelling after NQWI is accompanied by fundamental changes in cardiac energy metabolism.

Adenosine Triphosphate↗
PubMed2001

Vascular remodeling in atherosclerotic coronary arteries is affected by plaque composition.

BACKGROUND: Narrowing of lumen in atherosclerotic lesions is determined not solely by accumulation of plaque but also by constrictive or expansive vascular remodeling. Underlying mechanisms and determinants of these bidirectional processes are not known. OBJECTIVES: To elucidate the response of vascular remodeling to progressive atherosclerosis by analyzing its potential association with composition of plaque. METHODS: Seventy patients with 77 de-novo coronary artery lesions underwent intravascular ultrasound imaging before coronary intervention. Target lesions were defined as soft, fibrous/mixed, and calcified plaques. Quantitative measurements of area of lumen (A(L)), total area of vessel (A(TV)) and area of plaque (A(P) = A(TV)-A(L)) were performed at the lesion site and at the proximal and distal reference sites. Remodeling was determined by using a remodeling index [I(R) = (stenosis of A(TV)/mean reference A(TV)) x 100]. RESULTS: Overall vascular remodeling was balanced with a mean remodeling index of 100.2+/-19.3% and a high interlesion range (60.2-152.4%). The remodeling index for soft lesions was significantly higher than those for fibrous/mixed and calcified lesions (110+/-18.8 versus 96.2+/-14.4 and 85.9+/-15.1%, P < 0.01). Calcified lesions exhibited lower remodeling indexes than did uncalcified lesions (85.9+/-15.1 versus 104.6+/-18.4%, P < 0.01). CONCLUSIONS: Processes involved in vascular remodeling are affected by composition of plaque insofar as there is a higher prevalence of constrictive remodeling among calcified plaques and a higher prevalence of expansive remodeling among soft lesions. These findings indicate that constrictive remodeling is a late manifestation in atherogenesis. Future studies are warranted in order to enhance the understanding of progression of atherosclerosis, and of mechanisms of vascular remodeling and their impacts on interventional therapy.

Coronary Artery Disease↗
PubMed2001

Identification of hemodynamically significant restenosis after percutaneous transluminal coronary angioplasty in acute myocardial infarction by transesophageal dobutamine stress echocardiography and comparison with myocardial single photon emission computed tomography.

BACKGROUND: Beside thrombolysis, percutaneous transluminal coronary angioplasty (PTCA) has become a well-established treatment for acute myocardial infarction. However, restenosis occurs in approximately 15%-40% of patients. Despite a frequently occurring infarct-related regional systolic dysfunction at rest, the identification of hemodynamically relevant restenosis seems important in terms of risk stratification, adequate treatment, and possible improvement of prognosis in these patients. This study was designed to assess the role of transesophageal dobutamine stress echocardiography and myocardial scintigraphy for identification of hemodynamically significant restenosis after PTCA for acute myocardial infarction. METHODS: Multiplane transesophageal stress echocardiography (dobutamine 5, 10, 20, 30, and 40 micrograms/kg per min) studies and myocardial single photon emission computed tomography (SPECT) studies were performed in 40 patients, all of whom underwent PTCA in the setting of acute myocardial infarction > or = 4 months prior to the test. Repeated coronary angiography was performed in all study patients who showed stress-induced perfusion defects or wall-motion abnormalities, or both. RESULTS: Significant restenosis (> or = 50%) was angiographically found in 15 (37.5%) of 40 patients. Of these 15 patients, transesophageal dobutamine stress echocardiography identified restenosis in 12 (80%) and myocardial SPECT in 14 (93%), yielding diagnostic agreement in 70% of patients. Echocardiographic detection of restenosis was based mainly on a biphasic response to increasing doses of dobutamine. Sensitivity and specificity for identification of hemodynamically relevant restenosis in individual patients was 80% and 92%, respectively for dobutamine stress echocardiography versus 93% and 68% for myocardial SPECT. CONCLUSIONS: Both transesophageal dobutamine stress echocardiography and myocardial SPECT were highly sensitive in identifying significant restenosis after PTCA for acute myocardial infarction. Therefore, either test, as a single diagnostic tool or especially if performed together, are clinically valuable alternatives to coronary angiography for the detection of restenosis after PTCA for acute myocardial infarction.

Acute Disease↗
PubMed2001

[Comparison of dobutamine-stress magnetic resonance imaging and dipyridamole-TL-201-SPECT as alternative strategies for the detection of coronary artery dis in patients no suitable for stress echocardiography].

AIM: During the past decade stress-echocardiography has gained increasing popularity for detection of myocardial ischemia in patients with coronary artery disease. However, about 10% to 15% of the patients submitted for stress-echocardiography do not have an adequate acoustic window. The purpose of this study was to compare high-dose dobutamine-stress magnetic resonance imaging (dobutamine-MRI) with dipyridamole-Tl-201-SPECT (dipyridamole-SPECT) as alternative strategies for detection of myocardial ischemia in patients with inadequate image quality by stress-echocardiography. PATIENTS AND METHODS: Of 296 patients which were consecutively submitted to stress-echocardiography 45 patients (15%) had two or more segments that could not be evaluated according to the 16-segment-model of the American Society of Echocardiography. They underwent dobutamine-MRI and dipyridamole-SPECT studies, which were evaluated using a 28-segment modell. Myocardial segments were attributed to perfusion territories of the coronary arteries. The results of ischemia detection were compared to the results of coronary angiography (stenosis > or = 50%). RESULTS: In comparison to coronary angiography dobutamine-MRI yielded a sensitivity of 87%, a specificity of 86%, a positive predictive value of 93%, a negative predictive value of 75% and a diagnostic accuracy of 86%. For dipyridamole-SPECT results were 90%, 86%, 93%, 80% and 89%, respectively. These values were not significantly different. CONCLUSIONS: In patients not suitable for stress-echocardiography, both dobutamine-MRI and dipyridamole-SPECT are reliable strategies for detection of myocardial ischemia. Selection is dependent on the patient criteria, technical considerations, local logistics and experience of the observer.

Adrenergic beta-Agonists↗
PubMed2000

A synergistic approach to optimal stenting: directional coronary atherectomy prior to coronary artery stent implantation--the AtheroLink Registry. AtheroLink Study Group.

OBJECTIVES: The AtheroLink registry sought to observe the effect of plaque burden reduction by directional coronary atherectomy (DCA) prior to stenting on acute lesion success rate, on the clinical success rate and on the incidence of in-stent restenosis six months after intervention. BACKGROUND: Although coronary stenting has reduced restenosis, its effect has been less favorable in complex lesions with a high plaque burden that results from suboptimal stent expansion. Therefore, plaque removal by DCA may improve the results of coronary stenting. METHODS: A total of 167 patients with >60% stenosis in a native coronary artery of 2.8 to 4.0 mm in diameter were enrolled in 10 study centers on an intention-to-treat basis. All patients underwent DCA aimed at an optimal result (residual diameter stenosis <20%) followed by stenting. Angiographic follow-up was performed in 120 (71.8%) patients at 5.3+/-2.8 months. RESULTS: Lesion success was achieved in 164/167 (98.2%) patients, and the clinical success rate was 95.2% (159/167 patients). The overall restenosis rate in the 120 patients with angiographic follow-up was 10.8% (13/120). Incidence of restenosis was lower (8.4%) in patients with optimal stent deployment following DCA compared to patients with a persisting caliber reduction >15% (restenosis rate 15.3.%) and restenosis occurred with a significantly higher frequency (p<0.04) in distal lesions (37.5%) compared to proximal stenoses (9.0%). CONCLUSIONS: This observational multicenter registry points to a potential reduction in restenosis by a synergistic approach of DCA and stenting performed under routinely accessible angiographic guidance. Therefore, multicenter-based randomized clinical trials are clearly warranted to finally clarify the validity of this complex approach versus conventional angioplasty plus stenting.

Aged↗
PubMed2000

[Dobutamine-induced changes in the myocardial blood flow in patients with coronary heart diseases. A quantitative analysis using [15O] H2O positron emission tomography].

BACKGROUND AND OBJECTIVE: Although dobutamine is currently widely used for stress testing, only little is known about the effects of dobutamine on myocardial blood flow. The purpose of the present study was therefore to analyze quantitatively the regional changes in myocardial blood flow during rest and stress. PATIENTS AND METHODS: In order to assess these effects 17 patients (12 men, five women, mean age 57 +/- 8 years) with symptomatic single vessel coronary artery disease (> 70% stenosis) scheduled for coronary angioplasty underwent dobutamine stress testing with a maximum dose of 40 micrograms/kg/min. Myocardial blood flow was measured using 15O H2O position emission tomography at rest and during maximum stress in ischemic and non-ischemic myocardial regions. RESULTS: Dobutamine stress (median dose 30 micrograms/kg/min) increased the rate pressure product significantly (from rest 8697 [95% confidence interval 7959-9435] to stress 16,512 [15,208-17,815] mmHg/min (p < 0.001). Myocardial blood flow during rest was similar in non-ischaemic and ischaemic regions (0.91 [0.93; 0.83-1.28] vs. 1.10 [1.23; 0.91-1.28] ml/min/g, n.s.). During dobutamine stress myocardial blood flow increased in non-ischaemic regions to 2.17 (2.15; 1.77-2.57) ml/min/g, while myocardial blood flow did not increase in ischaemic regions (1.06 [0.97; 0.83-1.28], p < 0.001). Accordingly, dobutamine coronary reserve was 2.42 (2.55; 2.10-2.74) for non-ischaemic regions and 0.98 (1.05; 0.84-1.13) for ischemic regions (p < 0.001). Rate pressure product and myocardial blood flow were significantly correlated (r = 0.79, p < 0.001). CONCLUSION: A dobutamine-induced increase in rate pressure product was proportional to an increase in myocardial blood flow in non-ischaemic regions. In contrast, myocardial blood flow did not increase in myocardial regions supplied by a severely stenosed coronary artery.

Blood Flow Velocity↗
PubMed2000

Magnetic resonance pharmacological stress for detecting coronary disease. Comparison with echocardiography.

Stress testing is the cornerstone in the diagnosis of patients with suspected coronary artery disease (CAD). Although exercise ECG remains the primary approach for the detection of ischemia in patients with chest pain syndromes, its sensitivity and specificity is limited and exercise ECG does not provide detailed information about the localisation and extent of CAD. Stress echocardiography has been used for the detection of ischemia for more than a decade and has become an increasingly popular noninvasive method for the detection of CAD. In experienced hands wall motion analysis based on stress echocardiography has proved to be as sensitive and specific for the detection of myocardial ischemia as scintigraphic techniques. Recent technical improvements, namely the availability of ultrafast imaging sequences with a significant reduction of imaging time have initiated several studies which examined the combination of pharmacological stress and magnetic resonance imaging (MRI) for the detection of suspected CAD. The most well developed stress-MRI technique is wall motion imaging during dobutamine stress. This technique is analogous to stress echocardiography, but MRI has the inherent advantages of better resolution, higher reproducibility and true long and short axis imaging with contiguous parallel slices. However, the clinical impact of MRI for the diagnosis of CAD is still low. Further technical developments including real time imaging and a reliable automated quantitative analysis of left ventricular function are required before stress-MRI becomes a serious challenge to stress-echocardiography in the clinical arena. Currently, only a few MRI facilities and physicians are dedicated to pharmacological stress testing with MRI and the future clinical impact of this promising technique will depend on its potential to provide information beyond myocardial function including perfusion, metabolism and coronary anatomy in form of a "one-stop"-shop for the cardiac patient.

Cardiotonic Agents↗