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Biomedical subjects

E Wellnhofer

Publications and source records attributed to E Wellnhofer.

At least 37 records · Page 2Linked to original sources
PubMed1999

Coronary artery bypass grafting after orthotopic heart transplantation.

OBJECTIVE: Graft coronary disease (GCD) remains the major determinant of long-term survival after heart transplantation. Therapeutic strategies for the prevention or retardation of GCD in the cardiac allograft are limited, and palliative surgical coronary revascularization has been attempted. The aim of this report was to retrospectively analyze our results of coronary artery bypass grafting after cardiac transplantation. This paper correlates the outcome of patients with the pathohistological and angiographic type of lesion in order to identify transplant recipients who may profit from surgical myocardial revascularization. METHODS: Seven patients with a mean age of 55 years (range 45-61 years) underwent coronary artery bypass grafting as a result of GCD at a mean of 67 months (range 6-128 months) after cardiac transplantation. By the inclusion of the clinical history and the angiographic pattern of GCD lesions, the primary indications for surgical revascularization, operative results, pathohistological studies and follow-ups were examined. RESULTS: Elective surgery was performed in two patients with proximal, severe triple vessel disease (Type A lesion) and in one patient in whom the primary reason for cardiac surgery was severe tricuspid regurgitation. This patient electively received a tricuspid valve replacement and concomitant single vessel bypass surgery for proximal GCD (Type A lesion). Emergency surgery was performed in four patients: preoperatively three patients post-infarction developed worsening congestive heart failure, which resulted in low cardiac output syndrome. One patient with combined Types A and B/C lesions required emergency surgery for dissection of the right coronary artery (RCA) after an angioplasty procedure. Angiographically all these patients showed diffuse, distal arteriopathy (combined Type B/C lesions). The electively operated patients (n = 3) and the patient with dissection of the RCA (n = 1) had successful operations and survived beyond hospital discharge (overall survival for coronary artery bypass graft (CABG) in GCD patients 4 out of 7; 57%). All three patients with distal arteriopathy, who underwent emergency surgery, died in hospital from left ventricular failure (43%). The four patients discharged from hospital with a mean follow-up of 10 months (range 2-32 months) are all in good clinical condition. CONCLUSIONS: Coronary artery bypass grafting can be successfully performed in a subgroup of cardiac transplant patients with Type A lesions. However, the state of diffusely diseased distal arteries (Type B/C lesions), which is prevalent in this group of patients, limits the use of bypass surgery.

Biopsy↗
PubMed1999

Validation of an accurate method for three-dimensional reconstruction and quantitative assessment of volumes, lengths and diameters of coronary vascular branches and segments from biplane angiographic projections.

UNLABELLED: The goal of the study was the validation of an accurate method for three-dimensional reconstruction and quantitative assessment of volumes, lengths and diameters of coronary vascular branches and segments from biplane angiographic projections. METHODS: The accuracy was tested in a complex phantom. In vivo, inter- and intraobserver agreement were assessed by analysis of routine angiograms. The sensitivity was evaluated using angiograms of patients having diagnostic vasoactive pharmacological intervention. Two-dimensional quantitative coronary angiography (2-D QCA) and 3-D QCA were compared concerning the accuracy of diameter evaluation. RESULTS: 3-D QCA yields accurate results (< 3% error) even based on nonorthogonal views, provided that projections parallel to the object are avoided. The inter- and intraobserver variability is < or = 5%. Significant (p < 0.01) changes of the volume (36-39%) and the diameter (19-21%) are detected following pharmacological intervention. 2-D QCA and 3-D QCA agree in short matched segments without foreshortening. 2-D QCA is rather sensitive to foreshortening and not suitable for evaluation of diameters of longer branches or total coronaries. CONCLUSION: 3-D QCA permits an accurate, reproducible and sensitive comprehensive three-dimensional geometric analysis of the coronaries and is superior to 2-D QCA with respect to extended diameter evaluation.

Algorithms↗
PubMed1999

High fidelity correction of pressure signals from fluid-filled systems by harmonic analysis.

UNLABELLED: Fluid-filled systems are generally used for invasive pressure measurements in cardiology, anesthesiology and intensive care medicine. Wave reflection and attenuation cause considerable signal distortion. METHODS: The transducer signal is amplified (no filtering) and sampled (rate 1 kHz) using an autocorrelation based algorithm to detect instantaneous cycle length. A digital Fourier transformation (DFT) for each heart cycle is performed. Amplitude and phase distortion are corrected using data matrices determined in in vitro experiments or calibration measurements for each fluid-filled system to be used. As a measure for accuracy the maximum of the difference of reference and corrected pressures (DIFF) was selected. 960 analyses were performed to assess the impact of correction, used system, mean pressure, time and A/D sampling rate on the agreement with reference pressure. Clinical examples are presented. RESULTS: Mean pressure was correlated with DIFF (r = 0.83). The correction algorithm achieves a significant (p < 0.001) reduction of DIFF from 20-30 mm Hg to 0-5 mm Hg in the high pressure range and from 1-3 mm Hg to 0-1.5 mm Hg in the low pressure system in in vitro experiments and in clinical pressure recordings. Sampling frequency < 1 kHz reduces accuracy. CONCLUSIONS: High fidelity correction of pressure signals from fluid-filled systems by harmonic analysis is feasible.

Algorithms↗
PubMed1998

Coronary angioplasty, bypass surgery, and retransplantation in cardiac transplant patients with graft coronary disease.

BACKGROUND: Graft coronary disease (GCD) remains the single greatest limitation to long-term survival of heart transplant recipients. Therapeutic strategies for the prevention or retardation of GCD in the cardiac allograft are limited; palliative coronary revascularization has been attempted. Because of the high mortality rate associated with advanced forms of GCD our institution offers the option of retransplantation in selected cases. The aim of this study was by analyzing retrospectively the outcomes of angioplasty, coronary bypass grafting, and retransplantation in cardiac transplant patients to attempt to identify subgroups of transplant recipients with graft coronary disease who may profit from myocardial revascularization. METHODS: Of the 989 patients undergoing 1016 heart transplantations (HTx) at our institution between 10/86 and 12/97, all were screened for the development of GCD. Analyzing routinely annual angiography, intracoronary ultrasound in defined study patients, and autopsy findings, GCD was diagnosed in 124 patients (110 male, 14 female) 2 to 107 months after HTx (mean 30 months). RESULTS: PTCA: Fourty-six out of 124 patients underwent 76 angioplasties at a mean of 50 +/- 30 months (range 4-91 mo) following cardiac transplantation. The primary success rate was 96% (73/76). The reason for the unsuccessful angioplasty attempts (n = 3) was failure to completely penetrate a stenosis of LAD in 2 patients and severe dissection of RCA, which required emergency surgery, in one. Angiographic restenosis occurred in 42% (31 of 76 lesions) and was diagnosed 11 +/- 11 months after the first angioplasty. There was no procedure-related death. CABG: Seven patients underwent bypass surgery at a mean of 67 months (range 6-128 months) after HTx. Elective surgery was performed in 2 patients with proximal severe triple-vessel disease (Type A lesion) and in 1 patient with severe tricuspid regurgitation who received a tricuspid valve replacement and concomitant single-vessel bypass surgery for proximal GCD (Type A lesion). One patient with combined Type A and B/C lesions required emergency surgery for dissection of RCA after an angioplasty procedure. Three patients with post-infarction unstable angina developed worsening congestive heart failure which required emergency surgery. Angiographically all these patients showed diffuse, distal arteriopathy (combined Type B/C lesions). The electively operated patients and the patient with dissection of RCA were successfully treated and survived beyond hospital discharge (overall survival for CABG in GCD patients 4/7 = 57%). After a mean follow-up of 10 months (range 2-32 months) all are in good clinical condition. All 3 patients with distal arteriopathy and emergency surgery died in hospital of left-ventricular failure (43%). Retransplantation: Eight patients underwent retransplantation at a mean of 54 months (range 6-96 months) after HTx. Six of 8 patients had successful operations and survived beyond hospital discharge with a one-year-survival rate of 75%. In a mean follow-up of 31 months (5-68 months) 3 of 6 retransplant recipients developed a recurrence of GCD. CONCLUSION: The presence of angiographic distal arteriopathy should be considered a significant factor in patient selection for coronary revascularization procedure. Coronary angioplasty is to be considered as a method of treatment for severe, local stenoses (Type A lesion). PTCA may be applied in these selected cardiac transplant recipients with primary success and complication rates comparable to routine angioplasty but with an increased rate of restenosis especially in small vessels (diameter < 2.5 mm). The distinction between Type A lesions in large (diameter > or = 2.5 mm) and small vessels may be important not only with respect to restenosis but also with respect to long-term benefit. The overall survival did not differ between GCD patients with and without PTCA, suggesting this treatment to be largely palliative. (ABSTR

Angioplasty, Balloon, Coronary↗
PubMed1997

Improved assessment of intravascular Doppler coronary flow velocity profile.

Easy and safe in-vivo flow velocity studies in small coronary arteries have become feasible using a 0.014 'or 0.018' guidewire with an integrated Doppler probe in its tip (FloWire, Cardiometrics). Assessment of the flow velocity profile by the ratio of diastolic to systolic flow velocity (DSVR) is used as a diagnostic parameter. However, DSVR is a coarse quantifier of the flow velocity profile, and is subject to large physiologic variance and depends crucially on the quality of the Doppler signal. The aim of our study was to test parameters derived from statistical time series analysis for monitoring the quality of the instantaneous peak velocity (IPV) signal. Improvement of quantification of changes in quality and shape of flow velocity profiles by these parameters as compared to DSVR was a second goal. We investigated analog-digital converted IPV-signals and video registrations of corresponding greyscale spectra of intracoronary Doppler flow velocity signals. The signals were analyzed by using the autocorrelation function (ACF) in the time domain and a fast Fourier transform (FFT) in the frequency domain (standard time series statistics). The first minimum of autocorrelation function turned out to be very sensitive to signal quality, and Fisher's g of the periodogram was the parameter of choice for shape analysis. In 11 patients with coronary artery disease, pre and post PTCA, the sensitivity of DSVR and signal to noise ratio to changes in shape and quality of the flow velocity signals was compared to that of the new parameters. Nineteen Doppler flow velocity samples of good quality from measurements in nonstenotic vessels and 7 flow velocity tracings with visible artefacts were used to assess the value of these parameters in monitoring signal quality. By comparison with corresponding parameters in use (SNR and DSVR) a significantly improved performance of the new statistical parameters was observed with respect to sensitivity to changes in signal quality and flow profile. In view of these results and because of the short calculation time of these variables they should be used for on-line quality control and analysis of flow velocity profiles.

Adult↗
PubMed1997

[Value of Doppler blood flow velocity measurements in peripheral percutaneous laser-assisted angioplasties].

PURPOSE: The aim of the study was to establish the prognostic value and clinical implications of blood flow velocity measurements by Doppler guide wires during peripheral laser-assisted percutaneous transluminal angioplasty (PTLA). METHODS: 39 patients presenting with symptomatic peripheral arterial obstructive disease underwent angiography and blood flow velocity assessment by Doppler guide wire (0.018") prior to and following PTLA. Both quantitative angiography (QCA) for measurement of luminal diameters and Doppler assessment of maximum peak velocities (MPV) were performed 2 cm proximal, over and 2 cm distal to stenoses. The results were compared with the following clinical endpoints: 1. Short-term clinical improvement by AHA-criteria during first follow-up examination and 2. criteria for patency suggested by Rutherford [12] within 1 year (1-22 months). RESULTS: Angiography demonstrated initial success of PTLA in all patients. Relative diameter stenosis decreased from 70 +/- 0.04% to 17 +/- 0.05%. Mean clinically category improved from 2.7 +/- 0.1 to 1.2 +/- 0.1 following intervention. Mean grade of clinical improvement was 2.8 +/- 0.1. 22/39 patients demonstrated event-free follow-up examinations. Doppler measurements of MPV post PTLA in the proximal reference segment correlated with clinical outcome. MPV > or = 90 cm/s was associated with good primary success, unlimited walking capacity and event-free follow-up. MPV > or = 70 cm/s predicted an improvement of short-term clinical outcome by 2 grades (predictive value 80%). MPV < 70 cm/s was associated with both minor primary clinical improvement (+/- 0, +1) and increased incidence of restenosis during follow-up. CONCLUSION: Following PTLA, MPV adds information to angiographic success. MPV > or = 90 cm/s in a proximal reference segment following PTLA predicts good clinical outcome, whereas MPV < 70 cm/s is associated with minor primary clinical success and increased rates of restenosis.

Adult↗
PubMed1996

Accuracy and precision of angiographic volumetry methods for left and right ventricle.

We imaged and quantified 60 ventricle casts (30 LV, 30 RV) to evaluate the accuracy and reliability of angiographic ventricle volumetry. We analyzed the seven biplane methods most frequently used in clinical routine: Arcilla, Arvidsson, Dodge, Ferlinz, Simpson (LV + RV) and Wynne. The ventricle contours were defined by (1) manual drawing on the computer screen, (2) manual drawing using a graphical tablet and (3) automatic contour detection. A high inter-class variation in volume accuracy between the different methods was observed (S.D. = 12.7 ml). The volume methods for the LV (mean differences MDLV: [-2.2, +8.5] ml, average MDLV = 1.8 ml) are more accurate than for the RV (MDRV: [-11.4, +33.1] ml, average MDRV = 12.1 ml). The intrinsic error is about the same for all approaches and is very high: average S.D. = 20 ml, RMS = 185 ml. Manual contour definition results in a volume over-estimation (average MDman = +32.8 ml, r = 0.731) compared with automatic contour detection (average MDauto = +6.2 ml, r = 0.810). LV hypertrophy results in a volume under-estimation of the LV (MDLV = -7 ml) and an over-estimation of the RV (MDRV = +6 ml). RV hypertrophy leads to the opposite effect. It was shown that ventricle volumetry and the calculation of derived parameters (ejection fraction) is extremely case dependent and can only be an estimate of the actual value.

Angiography↗
PubMed1996

Intraaneurysmal flow: evaluation with Doppler guidewires.

Flow dynamics in cerebral aneurysms were studied with the use of Doppler guidewires in two patients. In both cases it was possible to reach the aneurysmal sac and to assess intraaneurysmal flow. Torquability and flexibility of the new Doppler guidewires permitted continuous assessment of flow velocity and flow pattern at the dome as well as in the neck area. Flow velocities were higher at the neck than within the aneurysmal sac (88 cm/s > 28 cm/s). Because of the limited area of interrogation (sample volume, 5 mm) it was not possible to investigate the complete intraaneurysmal space.

Adult↗
PubMed1995

Changes of fluid-dynamic parameters in peripheral stenoses with transcutaneous interventions.

UNLABELLED: Peripheral vessels provide a useful in vivo haemodynamic model allowing evaluation of local intravascular fluid dynamics. Velocity measurements using a 0.018 inch Doppler-tipped angioplasty guidewire, quantitative angiography and laboratory data were gathered from 45 patients with a total of 48 percutaneous transluminal laser assisted angioplasties (PTLA) in the superficial femoral, in the iliac, in the popliteal artery and in the peroneal artery. From these data, blood flow, whole blood viscosity, Reynold's numbers, Womersley numbers and shear stress were calculated, evaluated as to their changes post PTLA and correlated with clinical improvement at early follow-up. The clinical result was quantified as categorial improvement according to the American Heart Association guidelines. The primary angiographic results of angioplasty were satisfactory in all patients. Clinically 17/45 patients showed a marked, 6/45 a moderate, 18/45 a minimal, and 4/45 no improvement. The mean values of maximal peak velocity at stenosis decreased from 235 +/- 28 cms-1 to 84 +/- 8 cms-1 after PTLA (P < 0.01). The minimal intrastenotic cross section increased from 7.7 +/- 0.9 to 21.9 +/- 1.6 mm2 (P < 0.01). Mean trans-stenotic flow increased after intervention by about 50% (P < 0.01) and improved further by 135% after administration of adenosine triphosphosphate i.a. (P < 0.01). Reynold's numbers were elevated intrastenotically (1285 +/- 198) pre-intervention as compared to values proximal (564 +/- 81) and distal (449 +/- 66) to the stenosis and were reduced significantly (P < 0.05) at stenosis by PTLA, whereas values proximally and distally increased significantly (P < 0.01) post PTLA (proximal 829 +/- 84, intra 773 +/- 107, distal 676 +/- 98). Shear stress, reflecting mechanical interaction between flow and vessel wall, was elevated at stenosis pre-intervention to 44 +/- 8.9 Pa and reduced at post-stenoric vessel sites to 2.4 +/- 0.5 Pa. PTLA caused a decrease in stenosis to 6.3 +/- 1 Pa (P < 0.01) and an increase distally to 4.6 +/- 1 Pa (P < 0.01). Whereas in single stenoses removal of the obstruction was associated with a significant (P < 0.05) increase in trans-stenotic flow and shear stress distally, there was only auenuated increase in trans-stenotic flow in multiple lesions despite an angiographically good PTLA result. Shear stress distally remained low in those patients. Velocities and Reynold's numbers were lower in these vessels even pre PTLA. Residual flow, Reynold's number and minimal cross-section pre-intervention correlated significantly with clinical outcome. Pooling cases with no or minimal, as opposed to those with marked or moderate improvement, 81% of patients were correctly classified using the Reynold's numbers pre- and post-PTLA. CONCLUSION: Peak velocity monitoring is feasible and safe during angioplasty. Velocity provides clinically relevant physiological information in addition to angiography. Combining quantitative angiography, velocity measurements and laboratory data allow the calculation of blood flow, Reynold's numbers and shear stress, thereby providing complex fluid dynamic information. Thus the evaluation of haemo-dynamics in single and multiple obstructions before and after intervention is improved. Fluid dynamic parameters pre-and post-PTLA are significantly correlated with clinical short-term result.

Adult↗
PubMed1994

[A new methodologic approach for determining right ventricular volumes from transesophageal echocardiography].

In order to develop a concept of right ventricular volume estimation accounting for variance in positioning of the transesophageal transducer, non-linear scale transformations of suitable measurements of areas and perimeters were used in a new modeling-approach. This type of modeling supposes self-similarity of ventricular dimensions, a mathematical concept generalizing the notion of proportionality. In a study using right ventricular casts, we were able to demonstrate the geometry of right ventricles complies with these assumptions. The resulting multivariate power law volume estimators were developed by non-linear data fitting by learning-analyses based upon angiographic reference volumes and two areas derived from non-orthogonal sections using a monoplane transducer in a first series of studies, and two orthogonal areas with corresponding perimeters using a biplane device in a second series. Correction factors for systolic and diastolic volumes were applied. By prospective test-analyses angiographic and TEE-derived volumes were compared to evaluate our volume estimator and good agreement was found. Trend was evaluated by correlation amounts to r = 0.95 (n = 22) in series 1 with monoplane transducer, and r = 0.9 (n = 20) in series 2 with biplane transducer. This approach is of use in monitoring right ventricular function in cases with unsuitable transthoracical windows, e.g., in cardiac surgery postoperatively.

Adult↗
PubMed1982

[Contribution to the problem of preventing recurrences of oxalate and phosphate urinary caluli: active modification of citrate excretion and Ca++-binding capacity in the urine of Wistar rats].

Citric acid may well be, quantitatively and in terms of complex chemistry, the most important of the organic acids capable of binding Ca++ in urine. Since the quantitative determination of citrates in urine became a routine method in many research-orientated urological laboratories thanks to the introduction of standardized enzymatic tests, reports of a reduced excretion of citrates in patients with (recurrent) (oxalate) calculi have become frequent. During our long-term study of patients with recurrent formation of calculi we also observed a clear deficit of citrates in their morning, midday and evening urine. The conspicuous incidence of calculi when there is a concurrence of hypocitraturia and alkaline urine (RTA, in animal experiments: acetazolamide) clearly suggests the lithoprotective significance of citric acid. By quantitatively testing a large number of organic compounds which are interesting both structurally and in terms of complex chemistry, it has been possible to find some substances which restrict crystallization, raise the level of citrates and bind Ca++. A few have also found to restrict the excretion of oxalate in Wistar rats.

Animals↗
PubMed1982

[Search for a new rinsing solution for the local lysis of calcium-containing urinary calculi].

Due to improved rinsing techniques local chemolitholysis is again becoming more important. Good result good results in the local chemolysis of phosphate calculi (calculi caused by remains of Struvit) with Renacidin and other rinsing solutions (Fam, Rossier, Gittes, Jacobs, Smith, Royle, Nemoy, Stamey) have led to a revival chemolitholysis (Alken) in the last 4--5 years, however only in the case of phosphate calculi, which account for 60--80%, cannot be dissolved by Renacidin, as is explicitly pointed out by the manufacturer. The experiments carried out by the group headed by Kallistratos and Timmermann in the 60's using rinsing solutions based on EDTA were discontinued, probably because of physiological reservations concerning the chemicals used and the long duration of treatment at physiologically tolerable concentrations and pH values. In order to extend the range of rinsing solutions to be tested, we tested new substances, including some which complex not only the anion (oxalate) but also the cation (Ca). Alternating treatment with oxalate binding and Ca binding rinsing solutions has been found to give particularly good results.

Calcium Oxalate↗
PubMed1981

[In vitro and first in vivo experiments for the dissolution of calcium-containing urinary calculi (author's transl)].

There are numerous reports dealing with the significantly reduced citrate secretion in (recurrent) tone formers. The critical values of the Ca/citrate ratio in the nocturnal urine of (oxalate) stone formers has also been reported, emphasizing the need of medicaments being capable to increase the citrate secretion and to raise the basal citrate level of the nocturnal urine in these patients. In our in vitro experiments, we tested quantitatively the inhibitory activity of some new substances on crystal growth. In Wistar rats we measured the Ca2+-binding capacity as well as the citrate and oxalate excretion before and after oral application of a great number of new compounds. Some of them were highly efficacious in the reduction of the Ca-oxalate activity product, as can be derived from the increased Ca2+-binding capacity and/or the decreased oxalate secretion in urine.

Acetates↗
PubMed1981

[Detection of urinary organic acids by gradual titration of pH 2,0-7,4. Significance for the assessment of the litho-protective characteristic of the examined urine].

The role of organic acids in urine is not sufficiently known until today. From our detailed in vitro studies it can be concluded that some of them are highly efficacious in the inhibition of Ca-oxalate and Ca-phosphate crystal growth. Moreover, some of them showed, as acids and as salts, a strong lytic effect on stone-forming crystals and native stone-material. By the oral application to rats, concentrations preventing any precipitation out of meta- and instable Ca-oxalate solutions could be achieved. The renal excretion was controlled by the stepwise titration of preacidified urinary samples from pH 2.0 to 7.4 and the lithoprotective character of urine estimated by the Ca2+-binding capacity.

Animals↗