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Biomedical subjects

C A Nienaber

Publications and source records attributed to C A Nienaber.

At least 19 recordsLinked to original sources
PubMed2003

[Percutaneous stents for the treatment of stenosis of descending aorta].

Stenotic processes of the descending aorta lead to a transstenotic gradient with either risk of proximal hypertension especially affecting the cerebral circulation combined with the risk of distal malperfusion. This article describes the technique of percutaneous stenting of suprarenal aortic stenosis in two patients with different genesis of aortic obstruction in whom operative correction was refused due to elevated surgical risk. The first patient (female, 38 years) suffered from aortic stenosis at the thoracoabdominal level revealing a residual lumen of 3 mm. The second patient (male, 71 years) had a chronic type B aortic dissection and developed dynamic compression of true lumen and thus peripheral malperfusion. Both patients were treated successfully with percutaneous implantation of self-expanding stents. During the follow-up of 6 and 10 months, respectively, both patients were free of any symptoms. The technique of percutaneous stenting of static and dynamic stenotic processes of the aorta led to excellent mid-term results. Long-term results of large patient cohorts are not available yet; however, all patients subjected to such a palliative procedure should be followed in structured registries in an effort to standardize the concept and develop therapeutic recommendations.

Adult↗
PubMed2003

Randomized comparison of direct and provisional stenting in de novo coronary artery lesions: the RADICAL study.

BACKGROUND: Although preliminary reports have demonstrated excellent primary success and improved economics with direct stenting, a clinically relevant reduction of restenosis rate has not been documented yet. AIMS: Aims of the study were the comparison of restenosis rate (primary endpoint), procedural success, fluoroscopy time, amount of contrast dye and clinical outcome (secondary endpoints). METHODS AND RESULTS: Between January and December 1999, 250 patients were randomly assigned either to direct stent implantation without predilatation (DS; 125 patients) or provisional stenting (PB; 125 patients) and followed for 7.9+/-2.7 (6-9) months. Angiographic follow-up was available in 92.0% of patients. Procedural success rate was 92.8% in DS and 100% in PB (n.s.), while radiation exposure was lower (4.7+/-4.3 versus 5.1+/-1.8 min; p<0.0001) with DS. Conversely, the amount of contrast dye (131+/-62 versus 139+/-36 ml; n.s.) was not different between DS and PB. Direct stenting leads to a 25.0% reduction in binary restenosis rate (15.7% in DS versus 20.9% in PB), indicating an advantageous trend, missing however the level of statistical significance. Similarly, there was a trend to fewer major cardiac events with DS (DS 16.8%, PB 21.6%). CONCLUSIONS: We conclude that direct stenting is at least as safe and efficacious as balloon dilatation followed by provisional stent implantation, but failed to reduce restenosis rate or improve outcome within 6 months. Larger prospective randomized trials are required to assess the potential of direct stenting to reduce restenosis rate and improve clinical outcome in subgroups of patients.

Aged↗
PubMed2003

Induced arterial hypotension for interventional thoracic aortic stent-graft placement: impact on intracranial haemodynamics and cognitive function.

BACKGROUND AND OBJECTIVE: The study investigated the impact of induced arterial hypotension for the facilitation of endovascular stent-graft placement in patients with thoracic aortic aneurysm on cerebral blood flow velocity and neurological/neurocognitive outcome. METHODS: In 27 ASA III patients, cerebral blood flow velocity was recorded during induced arterial hypotension for endovascular stent-graft placement using transcranial Doppler sonography and the Folstein Mini Mental State Examination and the National Institute of Health Stroke Scale were performed before and after the intervention. RESULTS: Mean arterial pressure was decreased <50 mmHg, and in 22 patients it was <40 mmHg. Diastolic cerebral blood flow velocity decreased by 59%. Postoperatively, six of 21 patients exhibited changes in the Folstein Mini Mental State Examination and four of these six patients in the National Institute of Health Stroke Scale as indices of new-found neurocognitive dysfunction, but there were no signs of stroke. Loss of the diastolic blood flow profile was detected in two of six patients with new-found neurocognitive dysfunctions and in 18 of 21 patients with no new-found neurocognitive dysfunction. Changes in the Folstein Mini Mental State Examination on postoperative day 1 were correlated to the pre-procedural Folstein Mini Mental State Examination, but not to the time spent with a mean arterial pressure <50 mmHg, <40 mmHg or with a loss of diastolic blood flow profile. CONCLUSIONS: Transcranial Doppler sonography visualizes the individual effect of induced hypotension and the period of intracranial circulatory arrest during aortic stent-graft placement. However, transient new-found neurocognitive dysfunctions occur independently of the transcranial Doppler data, and are in close correlation to the neurocognitive state before the procedure. The results suggest that induced arterial hypotension is not the major factor for postoperative new-found neurocognitive dysfunction.

Aorta, Thoracic↗
PubMed2002

Prediction of left ventricular functional recovery by dobutamine echocardiography, F-18 deoxyglucose or 99mTc sestamibi nuclear imaging in patients with chronic myocardial infarction.

BACKGROUND: Currently, several modalities are available to predict viability, however, studies comparing various modalities validated by functional recovery after revascularization are scarce. This study analyzed the relative merits of low-dose dobutamine echocardiography, F-18 deoxyglucose (FDG) positron emission tomography (PET) and (99m)Tc sestamibi single-photon emission computed tomography to predict functional recovery after revascularization in patients with chronic myocardial infarction. METHODS: Patients with chronic coronary occlusion (duration: 3.1 +/- 4.8 years) and impaired left ventricular function (ejection fraction: 42 +/- 13%) underwent low-dose dobutamine echocardiography (20 microg/kg/min), FDG-PET and (99m)Tc sestamibi imaging before revascularization. Revascularization was performed irrespective of any viability data. Follow-up angiography was obtained 4.8 +/- 2.5 months after revascularization. RESULTS: Viability analysis was performed in 34 patients with patent target vessel at follow-up, of whom 9 (27%) exhibited functional recovery on left ventricular angiography. For dobutamine echocardiography, improvement of >/=2 adjacent akinetic segments resulted in improved sensitivity of 89% and specificity of 80% to predict functional recovery. For glucose metabolism, FDG uptake >55% was an optimal threshold yielding a sensitivity of 89% and a specificity of 68%. With respect to perfusion, (99m)Tc sestamibi uptake >60% was the best cutoff resulting in a sensitivity and a specificity of 56 and 88%, respectively. A concordant match of FDG >55% and of (99m)Tc sestamibi >50% resulted in optimized sensitivity (78%) and specificity (80%) with dual imaging. CONCLUSIONS: Recovery of chronically dysfunctional myocardium can be predicted with high accuracy by stimulation of contractile reserve or by concordant match of preserved glucose metabolism and residual perfusion.

Aged↗
PubMed2001

[Clinical diagnosis of acute aortic dissection].

Despite the availability of modern imaging technology, 35% of aortic dissections remain undiagnosed in vivo because clinical criteria for aortic dissection are not available to date. The present study analyzed 250 patients with acute chest and/or back pain, absence of an established differential diagnosis of the pain syndrome and clinical suspicion of acute aortic dissection for presence of 26 clinical variables. Multivariate analysis identified an aortic pain syndrome with immediate onset and/or tearing or ripping character (P < 0.0001), mediastinal and/or aortic widening on chest radiography (P < 0.0002) and pulse- and/or blood pressure differentials (P < 0.0001) as predictors of acute aortic dissection. Probability of dissection was low (7%) with absence of all three variables, intermediate (31 and 39%, respectively) with isolated findings of "aortic pain" or "mediastinal widening", and high (> 83%) with either isolated "pulse- and/or blood pressure differentials" or any combination of the three variables. This model appears useful to improve selection of patients for emergency imaging of the thoracic aorta.

Acute Disease↗
PubMed2001

[Splice site mutations and atherosclerosis: mechanisms and prediction models].

Nucleotide variants in genes of the lipid metabolism influence the risk of premature atherosclerosis. Ten percent of all single nucleotide substitutions in these genes involve splice sites. The effects of these changes on mRNA splicing and phenotypic severity, however, are not inherently obvious from the nucleotide sequence. This review presents various genes of lipid metabolism with splicing mutations known to influence the risk of premature atherosclerosis. Mechanisms of pre-mRNA splicing are illustrated and different models for prediction of the effect of nucleotide substitutions on splice-site function are presented. The role of information theory-based models is emphasized along with its role for prediction of splice-site function and phenotypic severity of atherosclerosis.

Age Factors↗
PubMed2001

[Endovascular stent-graft prosthesis in aortic aneurysm].

Descending thoracic and abdominal aortic aneurysms represent a potential life-threatening situation. Resection and graft replacement of the pathologically altered aorta used to be the preferred method of treatment. Although progress has been achieved during the past decades in the management of patients with thoracic aortic aneurysms by new surgical techniques, intraoperative monitoring of somatosensory-evoked potentials, and spinal cord fluid drainage, postoperative morbidity and mortality rates still remain high. The afflicted population is usually of older age and present at the time of operation with various comorbidities such as hypertension, obstructive pulmonary disease, coronary heart disease, all of which with significant impact on surgical outcome. Postoperative complications, such as paraplegia, renal and pulmonary disease, contribute to prolonged hospital stay and higher medical cost. In this review we report on a promising alternative approach to the surgical treatment of thoracic and abdominal aortic aneurysms, namely the currently emerging utilization of the endovascular stent-graft prosthesis in both thoracic and abdominal aneurysm.

Aortic Dissection↗
PubMed2001

Psychiatric conditions in patients with recurrent unexplained syncope.

AIMS: The relationship between syncope and psychiatric disorders is little investigated. This study evaluated the prevalence of psychiatric diseases and prognostic outcome in patients with recurrent unexplained syncope. METHODS AND RESULTS: After an inconclusive standard diagnostic work-up for syncope, including head-up tilt testing, a psychiatric evaluation was offered to 50 consecutive patients with recurrent syncope. The evaluation was accepted by 26 patients (77% females, 36 +/- 16 years) and refused by 24 (63% females, 50 +/- 19 years). A psychiatric disorder was diagnosed in 21 (81%) patients: 12 had depression, four panic attacks, two general anxiety, and three a somatization disorder. Only five patients showed normal psychosocial function. Of the patients with psychiatric disorders four accepted psychiatric care, such as psychotherapy and/or pharmacotherapy; 17 patients refused treatment. During 6 months of follow-up no patient under psychiatric care had syncope, while all patients without psycho- or pharmacotherapy had recurrent syncopal events. In these patients the median of syncopal episodes was three in a 6 months interval before and after clinical assessment. Patients who refused both psychiatric evaluation and therapy continued to experience syncope as before. CONCLUSIONS: In patients with recurrent unexplained syncope psychiatric alteration is common. However, patients seldom accepted a psychiatric evaluation and treatment.

Adolescent↗
PubMed2001

Intravenous coronary angiography using synchrotron radiation: technical description and preliminary results.

BACKGROUND: Standard coronary angiography requires an arterial access and catheters; intravenous coronary angiography may image coronary arteries noninvasively and without catheters. The aim of this study was the assessment of the diagnostic accuracy of intravenous coronary angiography validated by selective coronary angiography. METHODS: Seventy outpatients (80% males, mean age 62 +/- 8 years) underwent both standard and intravenous coronary angiography after a previous coronary intervention. Intravenous coronary angiography was performed within 6 weeks before or after selective coronary angiography. Two different projections were used to obtain 6-8 sequences per patient. Images were taken after injection of the contrast agent into the brachial vein or into the superior vena cava. During image acquisition, patients were moved through the scanning beam on a special chair. Thereafter, images were evaluated and compared to selective coronary angiograms for the following criteria: no stenosis, subsignificant stenosis (< 70%), significant stenosis (> or = 70%), and occlusion. RESULTS: One hundred eighty-seven target vessels were analyzed. In 50 target vessels one or more stents had been implanted. Seventeen target vessels were not analyzable due to inadequate image quality. The sensitivity of intravenous coronary angiography for the detection of lesions was 80% and the specificity was 95%. The sensitivity for the detection of significant lesions in the left anterior descending coronary artery was 84% (specificity 93%), in the left circumflex coronary artery 67% (specificity 90%), in the right coronary artery 85% (specificity 97%), and in bypass grafts 85% (specificity 97%). No complications were observed. CONCLUSIONS: Intravenous coronary angiography is efficacious and safe and allows quantification of lesions of the coronary arteries and of bypass vessels. Further advances in image processing are needed to improve sensitivity especially in the left circumflex coronary artery.

Contrast Media↗
PubMed2001

[Perforated mitral valve aneurysm as a rare course of bacterial endocarditis].

A 65 year old man with a history of mechanical aortic valve replacement acquired Enterococcus faecalis mediated infective endocarditis about 3 years later. Transesophageal echocardiography revealed formation of an aneurysm confined to the anterior mitral valve leaflet. The aortic valve revealed no signs of endocarditis by transesophageal ultrasound. With sudden perforation of the mitral valve aneurysm, subsequent hemodynamic deterioration and pulmonary oedema, the patient underwent emergency mitral and aortic valve replacement. The postoperative course was uneventful.

Aged↗
PubMed2000

Clinical prediction of acute aortic dissection.

BACKGROUND: Clinical criteria for aortic dissection are poorly defined. Thus, 35% of aortic dissections remain unsuspected in vivo, and 99% of suspected cases can be refuted. OBJECTIVE: To identify independent predictors of acute aortic dissection and create a prediction model for facilitated estimation of the individual risk of dissection. METHODS: Two hundred fifty patients with acute chest pain, back pain, or both; absence of an established differential diagnosis of the pain syndrome; and clinical suspicion of acute aortic dissection were evaluated for the presence of 26 clinical variables in a prospective, observational study. Multivariate analysis was performed to create a prediction model of aortic dissection. RESULTS: Aortic pain with immediate onset, a tearing or ripping character, or both; mediastinal widening, aortic widening, or both on chest radiography; and pulse differentials, blood pressure differentials, or both (P<.001 for all) were identified as independent predictors of acute aortic dissection. Probability of dissection was low with absence of all 3 variables (7%), intermediate with isolated findings of aortic pain or mediastinal widening (31% and 39%, respectively), and high with isolated pulse or blood pressure differentials or any combination of the 3 variables (> or = 83%). Accordingly, 4% of all dissections were assigned to the low-probability group, 19% to the intermediate-probability group, and 77% to the high-probability group of aortic dissection. CONCLUSIONS: Assessment of 3 clinical variables permitted identification of 96% of the acute aortic dissections and stratification into high-, intermediate-, and low-probability groupings of disease. With better selection for prompt diagnostic imaging, this prediction model can be used as an aid to improve patient care in aortic dissection. Arch Intern Med. 2000;160:2977-2982

Aged↗
PubMed2000

Clustering of mutations associated with mild Marfan-like phenotypes in the 3' region of FBN1 suggests a potential genotype-phenotype correlation.

Mutations in the gene for fibrillin-1 (FBN1) cause Marfan syndrome, a dominantly inherited disorder of connective tissue that primarily involves the cardiovascular, ocular, and skeletal systems. There is a remarkable degree of variability both within and between families with Marfan syndrome, and FBN1 mutations have also been found in a range of other related connective tissue disorders collectively termed type-1 fibrillinopathies. FBN1 mutations have been found in almost all of the 65 exons of the FBN1 gene and for the most part have been unique to one affected patient or family. Aside from the "hot spots" for the neonatal Marfan syndrome in exons 24-27 and 31-32, genotype-phenotype correlations have been slow to emerge. Here we present the results of temperature-gradient gel electrophoresis analysis of FBN1 exons 59-65. Six mutations were identified, only one of which had been previously reported. Two of the six mutations were found in patients with mild phenotypes. Taken together with other published reports, our results suggest that a sizable subset (ca. 40%) of mutations in this region is associated with mild phenotypes characterized by the lack of significant aortic pathology, compared with about 7% in the rest of the gene. In two cases, mutations affecting analogous positions within one of the 43 cbEGF modules of FBN1 are associated with mild phenotypes when found in one of the 6 C-terminal modules (encoded by exons 59-63), but are associated with classic or severe phenotypes when found in cbEGF modules elsewhere in the gene.

Adolescent↗
PubMed2000

The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease.

CONTEXT: Acute aortic dissection is a life-threatening medical emergency associated with high rates of morbidity and mortality. Data are limited regarding the effect of recent imaging and therapeutic advances on patient care and outcomes in this setting. OBJECTIVE: To assess the presentation, management, and outcomes of acute aortic dissection. DESIGN: Case series with patients enrolled between January 1996 and December 1998. Data were collected at presentation and by physician review of hospital records. SETTING: The International Registry of Acute Aortic Dissection, consisting of 12 international referral centers. PARTICIPANTS: A total of 464 patients (mean age, 63 years; 65.3% male), 62.3% of whom had type A dissection. MAIN OUTCOME MEASURES: Presenting history, physical findings, management, and mortality, as assessed by history and physician review of hospital records. RESULTS: While sudden onset of severe sharp pain was the single most common presenting complaint, the clinical presentation was diverse. Classic physical findings such as aortic regurgitation and pulse deficit were noted in only 31.6% and 15.1% of patients, respectively, and initial chest radiograph and electrocardiogram were frequently not helpful (no abnormalities were noted in 12.4% and 31.3% of patients, respectively). Computed tomography was the initial imaging modality used in 61.1%. Overall in-hospital mortality was 27.4%. Mortality of patients with type A dissection managed surgically was 26%; among those not receiving surgery (typically because of advanced age and comorbidity), mortality was 58%. Mortality of patients with type B dissection treated medically was 10.7%. Surgery was performed in 20% of patients with type B dissection; mortality in this group was 31.4%. CONCLUSIONS: Acute aortic dissection presents with a wide range of manifestations, and classic findings are often absent. A high clinical index of suspicion is necessary. Despite recent advances, in-hospital mortality rates remain high. Our data support the need for continued improvement in prevention, diagnosis, and management of acute aortic dissection.

Adult↗
PubMed2000

Aortic diseases--do we need MR techniques?

MR with its various imaging protocols including spin-echo MR-imaging, gradient MR imaging, flow-mapping and MR angiography is the ideal tool for noninvasive assessment of any kind of aortic diseases. The technique allows to image the aorta both in the thoracic cage and in the abdominal aspects better than any other tomographic image modality. With the capability of angiography after intravenous injection of gadolinium even the information previously only obtained from invasive catheter-based studies is now available within minutes after an intravenous injection. The overview manuscript compares various clinical settings of aortic diseases as assessed by various imaging modalities and highlights the capability of MR-imaging for aortic diseases both in the chronic and the acute clinical setting.

Aortic Dissection↗
PubMed2000

Impact of intravascular ultrasound guidance on directional coronary atherectomy.

In contrast to the luminogram of coronary angiography, intravascular ultrasound (IVUS) has proven to accurately assess both coronary lumen and vessel morphology due to its 360 degrees imaging capacity. Directional coronary atherectomy (DCA) improves the coronary lumen by removing plaque mass rather than stretching the vessel and compressing the plaque as with conventional percutaneous transluminal coronary angioplasty. In an attempt to optimize the procedural result of DCA we prospectively investigated the impact of IVUS guidance in a head to head comparison to on-line quantitative coronary angiography (QCA) on the result of DCA. In 16 consecutive patients IVUS demonstrated significant residual plaque mass after DCA irrespective of a satisfactory angiographic result. After a mean of 9 +/- 2 cuts luminal improvement was obtained with an area stenosis by angiography of 39 +/- 17% and by IVUS of 50 +/- 10% (p < 0.05), a diameter stenosis by angiography of 23 +/- 10% and IVUS of 35 +/- 14% (p < 0.05) and finally a minimal lumen diameter (MLD) by angiography of 2.9 +/- 0.5 mm and by IVUS of 2.3 +/- 0.5 mm (p < 0.005). After both on-line QCA and IVUS measurements a second series of 7 +/- 2 cuts were initiated to debulk more atheroma and improve stenosis dimensions. After additional cuts IVUS revealed further luminal improvement with an area stenosis by angiography of 25 +/- 16% and IVUS of 21 +/- 18% (n.s.), a diameter stenosis by angiography of 16 +/- 11% and by IVUS of 13 +/- 19% (n.s.) and finally a MLD by angiography of 3.1 +/- 0.5 mm and by IVUS of 2.8 +/- 0.3 mm (p < 0.05). Intraprocedural use of IVUS is superior to on-line QCA to assess the immediate result of DCA. IVUS-guided DCA results in more effective atheroma debulking than luminographic evaluation. Results of larger follow-up studies are needed to substantiate the intraprocedural advantage of IVUS with DCA.

Adult↗
PubMed2000

[Indirect genotype analysis as a diagnostic procedure in Marfan syndrome].

Marfan syndrome (MFS) is an autosomal dominant disorder of connective tissue characterized by skeletal, ocular and cardiovascular manifestations. The disease is caused by mutations in the FBN1 gene, encoding fibrillin, an important component of elastic fibers. Diagnosis of Marfan syndrome is currently based on detailed clinical examination and/or mutation analysis in the fibrillin gene. Clinical expression varies widely both among and within families, rendering clinical diagnosis extremely difficult. In this study, we performed segregation analysis of allelic DNA polymorphisms to support diagnosis of Marfan syndrome. This type of genotype analysis is a useful, additional diagnostic tool for families with Marfan syndrome and provides incremental information of diagnosis or exclusion of Marfan syndrome based on clinical findings.

Adolescent↗