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D Baumgart

Publications and source records attributed to D Baumgart.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Laser angioplasty and recanalization].

Percutaneous transluminal coronary balloon angioplasty (PTCA) still is the most frequently applied interventional technique for treatment of coronary artery disease. Plastic deformation of the obstructive plaque with creation of splits, intimal tears and dissections is the main mechanism of PTCA for lumen widening. As a result, acute complications due to flow limiting dissections and acute vessel closure can unpredictably occur resulting in myocardial infarction, urgent bypass surgery and death. Furthermore, long-term success of PTCA is limited by restenosis. In order to overcome these limitations of PTCA, alternative interventional techniques were developed, which instead of deforming the obstructive plaque ablate this tissue. These techniques include high and low speed rotational angioplasty, directional atherectomy, the transluminal extraction catheter, ultrasound angioplasty and laser (Light Amplification by Stimulated Emission of Radiation) angioplasty. 308 nm XeCl excimer laser angioplasty today is the laser technique of choice for clinical application. This pulsed laser requires direct contact to the obstructive plaque. It creates fast (< 200 microseconds) expanding gas bubbles which induce plaque ablation. Main indications for 308 nm XeCl excimer laser angioplasty are diffuse and long coronary lesions and total coronary occlusions. Despite promising initial results this technique showed no better acute and long-term results in comparison to PTCA for the treatment of these types of lesions ("Amsterdam-Rotterdam" Study, "Excimer Rotational Balloon Angioplasty Comparison" Study). As a result, this interventional technique was rarely applied for patient treatment. More recently, the concept of plaque ablation by 308 nm XeCl excimer laser angioplasty was renewed for the treatment of in-stent restenosis. This indication is being investigated in the "Laser Angioplasty of Restenosed Stents" trial. First results document the practicability and safety of this approach. Long-term results are awaited. With ongoing miniaturization, laser guidewires were developed for the recanalization of chronic total occlusions. The randomized multicenter "Total Occlusion Trial with Angioplasty assisted by Laser guidewire "Study documented a success rate of laser wire recanalization in up to 66% in contrast to 47.5% for mechanical wires only. Long-term results are still awaited. Technical and procedural progress including saline flush during laser application, homogeneous light distribution and the concept of smooth laser ablation is pushed foreward to make excimer laser angioplasty safer, more predictable and more effective.

Angioplasty, Balloon, Coronary↗
PubMed1997

[Intravascular irradiation in the combined therapy and prevention of restenosis. Overview].

Despite numerous efforts in catheter technology and procedural approaches the problem of restenosis in interventional cardiology persists. Although the implantation of coronary stents has significantly reduced restenosis rates based on the inhibition of elastic recoil, intimal proliferation as the second major mechanism for postinterventional restenosis could not effectively be suppressed. Intimal proliferation is the response to vessel injury following interventional procedure, e.g. balloon angioplasty. It results in the adhesion of mono- and lymphocytes which themselves trigger the colonisation of myofibroblasts. Intracoronary irradiation seeks to prevent this proliferative process as it destroys or irreversibly alters DNA structures of cells at the site of balloon injury. The antiproliferative effect depends on the irradiation dosis, the timing and the cell cycle phase. Mainly beta- and gamma-radiation is used for intracoronary irradiation. Beta-emitters are characterized by a sharp decline of dose rate within millimeters from the actual source. The exposure to surrounding tissue as well the catheter staff can be kept to a minimum. The high intensity of beta-emitters allow a short treatment period of minutes to gain an effective radiation dose to the target. In contrast, gamma-emitters have a low radial dose distribution resulting in high dosage even centimeters away from the source. These emitters require additional shielding in the catheter laboratory and lead to excessive whole body doses. To achieve a sufficient dose in the target tissue, irradiation times of more than 20 minutes are necessary which prolongs the interventional procedure substantially. At present, catheter based systems or radioactive implantable stents are available to deliver the required dose. Catheter based systems seem more flexible in a number of considerations. On the other hand they require a substantial amount of hardware. Beta-emitting stents are implanted via a conventional stent delivery system with small shielding modifications. However, stents emit an inhomogeneous radiation profile due to the mesh-like structure. In addition, not every lesion can be reached by a stent nor does every lesion require a stent solely to deliver radiation. External irradiation is presently not recommended due to its ineffectiveness and the high rate of side effects. In the experimental setting the porcine model comes closest to the clinical situation in man. Animal experiments have demonstrated the effective reduction of intimal proliferation using beta- and gamma-sources in a wide dose range of 3 to 56 Gy. Although the initial and early results are convincing little is know about the long term results. Only few studies have been and are currently performed in patients. Some of these investigations demonstrate a significant reduction of restenosis rate after 6 months. Again, information on long-term results are lacking. It has to be considered that perivascular fibrosis, which may occur with a delay of 5 to 10 years depending on the dosage, could curtail the initial success. Intracoronary irradiation is a promising method for the prevention of restenosis. The dose finding with respect to the dose effect relation, the determination of the therapeutic window and the timing of irradiation have to be further defined in the clinical setting. Nevertheless, intracoronary irradiation remains high on the priority list in fighting restenosis.

Animals↗
PubMed1997

[New developments in parameter-oriented roentgen densitometry perfusion analysis within the scope of heart catheter studies].

X-ray densitometric evaluation of digital subtraction coronary arteriograms allows a qualitative and quantitative detection of contrast medium propagation through the epicardial coronary arteries, the capillary system and the coronary venous system. So-called "time-density-curves" (TDCs) can be generated following Lambert-Beer's law similar to indicator dilution curves by using contrast medium as the indicator. Several time and density parameters can be derived from these TDCs, which are related to local myocardial perfusion. Different animal validation studies have shown the applicability of this concept for in-vivo evaluation of coronary blood flow and myocardial perfusion. Nevertheless, absolute measurement of volumetric coronary blood flow or myocardial perfusion failed. Therefore, relative changes in coronary blood flow or myocardial perfusion in response to pharmacologically induced maximum hyperemia were measured and coronary or myocardial perfusion reserve was calculated as the ratio of hyperemic flow or perfusion divided by baseline values. Despite theoretical attractions for an application during routine cardiac catheterization, this densitometric approach did not get a wide acceptance. Primary reason for this limited use in specialized centers was the time consuming process of densitometric evaluation of the subtraction coronary arteriograms, which require digital cine angiography and necessitates enormous computer hard ware. This main limitation has been overcome since more powerful computer hard ware (processor speed, hard disk space, digitization boards) has become rapidly available during the last years at more moderate pricing and digital techniques today are state of the art in cardiac catheterization laboratories. In addition, soft ware program packages allowed an automatization of the digitization and densitometric evaluation process. These programs include ECG triggered cine image digitization with improved temporal resolution, semiautomatic definition of regions-of-interest including definition of reference regions-of-interest for the detection of background density changes and quality-controlled densitometric parameter analysis. This progress made an application during routine cardiac catheterization feasible. In animal validation studies this improved X-ray densitometric approach for evaluation of local myocardial perfusion was validated versus colour-coded microsphere techniques. The time parameter "rise time", defined as the time from the start of local contrast medium induced density change to its maximum revealed a close correlation (r2 = 0.965) to the results of the microsphere technique over a wide range of perfusion. We have applied this technique before and after coronary interventions such as balloon angioplasty and stenting. Results documented an improvement of poststenotic myocardial perfusion reserve immediately after coronary balloon angioplasty and an additional improvement after adjunct coronary stenting. Only after stenting but usually not after coronary balloon angioplasty alone poststenotic myocardial perfusion reserve gained the intraindividual reference level, measured in a perfusion bed supplied by an epicardial coronary artery without stenoses. These results documented the functional benefit of coronary stenting on poststenotic myocardial perfusion in addition to the well known morphologic benefit with the creation of a larger and more circular conduit.

Absorptiometry, Photon↗
PubMed1997

Comparison of electron beam computed tomography with intracoronary ultrasound and coronary angiography for detection of coronary atherosclerosis.

OBJECTIVES: This analysis compared the results of electron beam computed tomography (EBCT) with those of coronary angiography and intracoronary ultrasound (ICUS) for the in vivo detection of coronary atherosclerotic plaques. BACKGROUND: EBCT is a new imaging modality for identification of coronary calcifications. Coronary angiography depicts advanced changes in coronary morphology, whereas ICUS is an established diagnostic tool that detects the early stages of coronary artery disease. METHODS: In 57 patients (54 +/- 9 years old), 267 coronary segments were analyzed with EBCT (3-mm slices, acquisition time 100 ms, threshold definition of coronary calcification at 130 Hounsfield units in an area > or = 1 mm2, Agatston calcium score), coronary angiography and ICUS. The analysis was based on the number and extent of coronary calcifications on EBCT, coronary lumen reduction on coronary angiography and plaque formation with and without ultrasound signs of calcifications on ICUS. RESULTS: Compared with coronary angiography, EBCT yielded a sensitivity of 66%, a specificity of 78%, a positive predictive value of 39% and a negative predictive value of 91%. Compared with ICUS, EBCT yielded an overall sensitivity of 66%, a specificity of 88% and an overall accuracy of 81%. For plaques with and without ultrasound signs of calcifications, the sensitivity of EBCT was 97% and 47%, specificity 80% and 75% and overall accuracy 82% and 69%, respectively. CONCLUSIONS: This in vivo correlation between ICUS and EBCT demonstrates that EBCT is a noninvasive method that helps to visualize the atherosclerotic process by localization and quantification of coronary artery calcifications. EBCT detects calcified plaques with high accuracy. Plaques without ultrasound signs of calcifications can be detected by EBCT but with lower sensitivity but equivalent specificity.

Adult↗
PubMed1996

Comparison of myocardial perfusion reserve before and after coronary balloon predilatation and after stent implantation in patients with postangioplasty restenosis.

BACKGROUND: Stents provide a scaffold for coronary arteries after angioplasty and inhibit elastic recoil. METHODS AND RESULTS: In 25 patients with postangioplasty restenosis of the left anterior descending artery, ECG-gated digital subtraction coronary angiograms were recorded at baseline and during hyperemia (12 mg papaverine IC) before and after balloon predilatation (PTCA), after implantation of a Palmaz-Schatz stent, and after 6 months. Densitometric evaluation revealed different time and density parameters to calculate two definitions of myocardial perfusion reserve (MPR1 and MPR2) and maximum flow ratio (MaxFR). Poststenotic MPR1 increased from 1.57 +/- 0.14 to 2.59 +/- 0.86 after PTCA and to 3.10 +/- 0.41 after stenting, with 2.90 +/- 0.65 at follow-up (ANOVA, P < .05), while reference MPR1 remained unchanged at 3.10 +/- 0.40. Poststenotic MPR2 increased from 1.36 +/- 0.28 to 2.50 +/- 1.20 and to 3.40 +/- 0.58, respectively, with 3.20 +/- 0.92 at follow-up (ANOVA, P < .05), while reference MPR2 remained unchanged at 3.40 +/- 0.60. MaxFR was 2.13 +/- 0.53 after PTCA, elasticity 2.83 +/- 0.35 after stenting, and 2.73 +/- 0.58 at follow-up (ANOVA, P < .05). A good correlation was found between minimal stenotic luminal diameter and MPR1 or MPR2 (r = .87 and r = .94) and between luminal gain and MaxFR (r = .75). A negative correlation was measured between recoil and MPR1, MPR2, and MaxFR (r = -.80, r = -.86, and r = -.83). At follow-up, a steeper correlation was found between MPR and minimal stenosis diameter (MPR1: slope, 0.52 versus 0.91; MPR2: slope, 1.48 versus 1.95) and between MaxFR and net lumen gain (slope, 0.78 versus 1.27). CONCLUSIONS: Coronary stent implantation in patients with postangioplasty restenosis normalized poststenotic myocardial perfusion immediately as a result of a larger postprocedural lumen and a more pronounced inhibition of elastic recoil. After 6 months this benefit was sustained despite progressive lumen loss.

Absorptiometry, Photon↗
PubMed1996

Equipment configuration and procedures: preferences for interventional microtherapy.

Magnetic resonance imaging (MRI), computed tomography, and electron beam tomography scanners are built for radiologic diagnosis. With increasing frequency they are being used in the field of interventional Microtherapy to permit transparent visualization of the therapeutic field. Each of these scanners can be combined with endoscopy, fluoroscopy/digital subtraction angiography, and ultrasound units for hybrid imaging techniques as well as with therapeutic systems like lasers or radiofrequency. MRI affords 3D localization without x-ray exposure. Open access and keyhole imaging allow nearly real time guidance of instruments. Minimally invasive techniques using endoscopes and hybrid tomographic guidance result in improved tip tracking of microinstruments and reduced complications. This safer access into the body will lead to interdisciplinary cooperation with the potential for large cost reductions. This report summarizes our experience regarding which of the hybrid imaging suites is best suited for procedures including among others drug instillations, prosthesis (stent) implantation, or microoperations (endoscopic diskectomy/sequestrectomy), and physiological measurements simultaneously.

Diagnostic Imaging↗
PubMed1996

Non-invasive assessment of coronary Palmaz-Schatz stents by contrast enhanced electron beam computed tomography.

UNLABELLED: The aim of the study was the evaluation of electron beam computed tomography as a non-invasive method to localize coronary stents and to document patency in stented vessel segments. METHODS: Twenty-two patients (16m/6f, 58 +/- 7.8 years) with coronary Palmaz-Schatz stents were examined. Contrast enhanced electron beam computed tomography using an Evolution scanner (Siemens) and coronary angiography were carried out within 7 days of each other. Stent localization was performed using the single-slice mode of the electron beam computed tomography scanner. Patency of the coronary target segment was assessed using the multi-slice mode after peripheral venous injection of a 40 ml bolus of contrast medium (Ultravist 370). Qualitative image analysis of a cine loop of 10 consecutive frames and quantitative analysis of densitometric curves in a region of interest distal to the stented vessel segment were performed. RESULTS: All stented vessel segments were identified. In 20 patients (91%), qualitative assessment of contrast enhancement patterns enabled stent patency to be evaluated. In 18 patients (90%), contrast medium was visualized distal to the stent. Quantitative coronary angiography confirmed that the stented vessel segments were not stenosed. Densitometric curves obtained in 16 of these 18 patients yielded contrast enhancement distal to the stented vessel segment of 63 +/- 6% compared to the aorta. In one patient, qualitative and quantitative analysis showed prolonged contrast enhancement of reduced density, which hinted at a stenosis related to the stented vessel segment. Coronary angiography revealed subtotal occlusion of the stented vessel directly distal to the stent. In another patient, no contrast visualization of the vessel distal to the stent was achieved. Coronary angiography revealed complete stent occlusion in this case. CONCLUSION: Electron beam computed tomography can reliably localize coronary stents and may become a useful tool for providing information on stented vessel segment patency.

Adult↗
PubMed1996

Non-invasive visualization of coronary arteries with and without calcification by electron beam computed tomography.

Coronary artery disease (CAD) is one of the leading causes of mortality and morbidity in the western industrialized countries. Recent studies demonstrate the feasability of successful primary and secondary prevention. However, the detection of early stages of coronary artery disease is an unresolved issue. Whereas sensitivity and specificity of traditional risk factor assessment and stress tests are limited, the analysis of coronary calcification allows to obtain a direct sign of coronary atherosclerosis. This concept has been applied using fluoroscopy and conventional computed tomography (CT). However, the exact localization and quantification of coronary calcification only became possible with the advent of electron beam CT (EBCT). This new method showed a high prevalence of coronary calcification in the asymptomatic population. With the definition of a standardized "calcium score" the normal age-specific distribution and amount of coronary calcification was investigated. EBCT proved to be more sensitive in the diagnosis of both non-obstructive and obstructive coronary artery disease than risk factor analysis and stress testing, respectively. Obstructive coronary artery disease, however, cannot yet be predicted with high enough accuracy. A close correlation of EBCT coronary calcification was found to a) the total coronary plaque volume defined by histo-pathology, b) intracoronary ultrasound findings, c) the number of coronary risk factors, d) the coronary prognosis. Using EBCT, a reliable non-invasive identification of persons at risk was obtained for the first time. Guidelines for the use of EBCT in the early diagnosis and treatment of coronary artery disease are being developed.

Adult↗
PubMed1996

[Normalization of myocardial perfusion reserve after coronary stent implantation in comparison with balloon angioplasty alone].

Stents scaffold coronary arteries after angioplastic treatment and inhibit elastic recoil resulting in a larger and more circular focal lumen. In 25 patients with significant stenoses of the left anterior descending coronary artery, presenting no collaterals or myocardial infarction, EKG-gated digital subtraction angiograms were recorded at baseline and during hyperemia induced by intracoronary injection of 12 mg papaverine before and after balloon angioplasty, and after adjunct implantation of a single Palmaz-Schatz stent. Densitometric evaluation revealed the time parameters contrast medium appearance time (MCAT) rise time (RT) and mean transit time (MTT) and maximum intensity (Imax). Myocardial perfusion reserve (MPR1) was calculated as the ratio of baseline MCAT and hyperemic MCAT multiplied by the ratio of hyperemic Imax and baseline Imax while MPR2 was calculated as the ratio of baseline RT and hyperemic RT. Maximum flow ratio (MaxFR) was calculated as the ratio of preprocedural hyperemic MTT and postprocedural hyperemic MTT. Post-stenotic MPR1 increased from 1.36 +/- 0.28 to 2.50 +/- 1.20 and to 3.40 +/- 0.58 (ANOVA p < 0.05), while reference MPR1 remained unchanged with 3.40 +/- 0.60. Post-stenotic MPR2 increased from 1.57 +/- 0.14 to 2.59 +/- 0.86 after balloon angioplasty and to 3.10 +/- 0.41 after stenting (ANOVA p < 0.05), while reference MPR2 remained unchanged with 3.10 +/- 0.40. MaxFR was 2.13 +/- 0.53 after balloon angioplasty and 2.83 +/- 0.35 after stenting (p < 0.05). A good correlation was found between minimal stenosis diameter and MPR1 or MPR2 (MPR1: r = 0.94; MPR2: r = 0.87) and between luminal gain and MaxFR (r = 0.75). A negative correlation was measured between recoil, defined as the difference between inflated balloon diameter and resulting minimal stenosis diameter, and MPR1 and MPR2 and MaxFR (MPR1: r = -0.86; MPR2 r = -0.80; MaxFR r = -0.83). In conclusion, adjunct coronary stent implantation normalized post-stenotic myocardial perfusion immediately in contrast to balloon angioplasty alone resulting from a larger postprocedural lumen and a more pronounced inhibition of elastic recoil.

Adult↗
PubMed1996

[Effect of high insufflation pressures on elastic recoil forces and vascular resistance after balloon dilatation].

In this study, we examined whether percutaneous coronary angioplasty (PTCA) of native coronary arteries with high inflation pressure can improve the immediate postinterventional result in comparison to PTCA with nominal inflation pressure. Using quantitative coronary angiography, we analyzed the coronary angiograms of 24 patients who underwent PTCA with nominal inflation pressure (< 10 atm; group 1) and of 20 patients who underwent PTCA with high inflation pressure (> or = 10 atm; group 2). Only balloon catheters with little compliance were used. The following variables were recorded: 1) minimal luminal diameter (MLD), reference diameter and percent diameter stenosis before and after PTCA, 2) average balloon diameter during PTCA, 3) balloon/artery diameter ratio, 4) acute luminal gain (difference between MLD before and after PTCA), 5) nominal elastic recoil (difference between nominal balloon diameter and MLD after PTCA), 6) actual elastic recoil (difference between average balloon diameter during PTCA and MLD after PTCA). Nominal balloon diameter, reference diameter before and after PTCA and the balloon/artery diameter ratio were similar in both groups. Application of high inflation pressure resulted in a greater average balloon diameter. In group 2 (high inflation pressure), average balloon diameter amounted to 94 +/- 12% of nominal balloon diameter, whereas in group 1 (nominal inflation pressure), it reached only 84 +/- 9% of nominal balloon diameter. Actual elastic recoil was not different between the two groups. Nominal elastic recoil, however, was greater in the cohort which received PTCA with nominal inflation pressure (1.13 +/- 0.35 mm vs. 0.83 +/- 0.28 mm; p < 0.02). After use of high inflation pressure, acute postinterventional luminal gain was significantly increased (1.04 +/- 0.25 mm vs. 0.77 +/- 0.34 mm; p < 0.02) and the postinterventional percent diameter stenosis was significantly lower (12 +/- 10% vs. 24 +/- 13%; p < 0.05). Application of high inflation pressure improves the postinterventional result after PTCA because of a greater acute luminal gain. The stenotic coronary artery is expanded to a greater degree, and actual elastic recoil remains unchanged.

Adult↗
PubMed1996

[High frequency rotational angioplasty].

High-speed rotational coronary atherectomy is an alternative method to treat complex, especially calcified coronary stenoses. A rotating burr tip removes the occlusive plaque tissue. The applied rotating frequency is between 160 000 to 190 000 rpm. The primary technical success-rate for high frequency rotational atherectomy alone yields between 50 to 60% on average. Associated with consecutive additional balloon angioplasty, the success rate is between 80 and 95% when treating complex type B II or C stenoses. Today, the usage of a single burr tip size with adjunctive balloon angioplasty has become a standard procedure. The occurrence of serious complications such as extensive dissections or thrombotic vessel occlusion is a rare phenomenon after high-speed rotational atherectomy compared to coronary balloon angioplasty, whereas coronary spasm is more common after high-speed rotational atherectomy. According to the actual results, high-speed rotational angioplasty did not lower the rate of long-term restenosis, compared to the results achieved by balloon angioplasty alone. The rate of long-term restenosis is reported to be between 40 to 50% after highspeed rotational angioplasty with or without adjunctive balloon angioplasty.

Atherectomy, Coronary↗
PubMed1995

[Electron beam tomography in coronary disease. Prevalence and distribution of coronary calcifications and their relationship with coronary risk factors in 650 patients].

OBJECTIVE: The extent of coronary calcification demonstrated by electron beam tomography was correlated with the individual cardiac risk profile. PATIENTS AND METHODS: The possible presence of coronary calcifications was studied by electron beam tomography (EBT) in 650 patients (526 men, 124 women; mean age 54 +/- 10 [28-81] years) with known or suspected coronary heart disease. Depending on the degree of density and the size of the lesion a score was calculated according to an international standard. RESULTS: No calcification was shown to be present in 202 patients (score of 0). A score of more than 0 was calculated in 73.8% of men and 48.4% of women. The average score was 227.8 +/- 24.8 in men, compared with 65.3 +/- 26.5 in women (P < 0.001). There were significantly more calcifications in older patients: Men aged 71-75 years had the highest score, 859.4, while the lowest, 9.6, was in those aged 36 to 40 years. The most important variables for the presence of calcification were age (relative risk per age group: 1.6), male sex (relative risk: 4.3), hypertension (relative risk: 2.4) and nicotine consumption (relative risk: 1.8). The median point score in patients without known risk factors was 1.3, with one known factor it was 7.2, and with three it was 48.0. The vessel segment most affected with calcification was the anterior interventricular branch with an average score of 84. CONCLUSION: Together with an evaluation of the risk profile EBT provided a better assessment of individual risk than conventional examination.

Adult↗
PubMed1995

Intravascular ultrasound approach to the diagnosis of coronary artery aneurysms.

Coronary artery aneurysms are usually diagnosed by contrast coronary angiography, which portrays the silhouette of the lumen but cannot distinguish true and false aneurysms. To differentiate true and false aneurysms and to study the morphologic changes of the vessel wall, intravascular ultrasound (IVUS) was performed in patients with angiographic signs of coronary artery aneurysms. We used a 4.8F or 3.5F, 20 MHz IVUS catheter for ultrasound examination. Fourteen patients (12 men and two women ranging in age from 43 to 73 years) with angiographic signs of coronary aneurysm were enrolled. IVUS imaging was optimally obtained in all patients. The vessel area, lumen area, and plaque area of the aneurysm segment and of the proximal and distal segments were determined. IVUS showed that both the proximal and distal reference segments were severely affected by atherosclerotic lesions in all the patients and by calcium deposits in six patients. The percent stenoses were 63.0% +/- 13.7% and 60.9% +/- 17.8% in the proximal and distal reference segments, respectively. In nine patients the walls of the aneurysms showed signs of atherosclerosis. Three angiographically indicated aneurysms were found to be plaque ruptures. Although the lumen and the vessel areas of the aneurysm segments were larger than those of the proximal and distal segments (p < 0.01 and (p < 0.001), no significant differences in plaque area and plaque composition were found between the aneurysm segment and adjacent vessel segments (p > 0.05). In conclusion, IVUS allows detailed characterization of coronary aneurysms. Atherosclerosis seems to play an important role in the formation of acquired coronary aneurysms.

Adult↗