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Biomedical subjects

H R Zerkowski

Publications and source records attributed to H R Zerkowski.

At least 55 records · Page 3Linked to original sources
PubMed1998

Influence of transducer frequency on Doppler microemboli signals in an in vivo model.

The purpose of this study was the comparison between 1 MHz and 2 MHz transducers in the detection of Doppler microembolic signals (MES). Intraoperative monitoring was performed over the arterial tubing of the extracorporal circulation circuit in 10 patients undergoing coronary artery bypass surgery, using a pulsed ultrasound machine (DWL X-4). 1 MHz and 2 MHz probes were mounted to insonate sequential tubing segments and all monitoring sessions saved on digital audio tapes (DAT). MES counts and intensity as detected by each probe were subsequently evaluated. Specific interobserver agreement was assessed using Cohen's kappa-statistic. Time delay in the appearance of MES between the transducers was minimal (0-0.1 msec). A total of 5293 (64%) MES were detected by both probes, 2796 (33.8%) only with the 1 MHz and 181 (2.2%) only with the 2 MHz probe. Significant differences in MES intensity were evident when comparing the 1 MHz to the 2 MHz transducer (16.4 +/- 0.1 and 11 +/- 0.1 dB with the 1 MHz and 2 MHz transducers respectively, p < 0.0001). Specific interobserver agreement was satisfactory (k = 0.78). Use of 1 MHz instead of 2 MHz transducers increases the yield of embolus detection in vitro. Evaluation of the applicability and performance of this transducer in clinical settings is warranted.

Catheters, Indwelling↗
PubMed1998

Diminished responsiveness of Gs-coupled receptors in severely failing human hearts: no difference in dilated versus ischemic cardiomyopathy.

In end-stage heart failure, cardiac beta-adrenoceptors are decreased and cardiac Gi protein is increased. We assessed beta-adrenoceptors, G proteins, and effects of several beta-adrenoceptor agonists, histamine, and 5-HT on adenylyl cyclase activity in right and left atria and left ventricles and on left ventricular contractility in six potential heart transplant donors (nonfailing hearts; NFHs) and in nine patients with end-stage dilated cardiomyopathy (DCM) and 11 patients with end-stage ischemic cardiomyopathy (ICM) to establish whether the functional responsiveness of all cardiac Gs-coupled receptors is reduced. Beta-adrenoceptors were reduced in all three tissues; in DCM, beta1-adrenoceptors were more markedly downregulated; in ICM, both beta1- and beta2-adrenoceptors were diminished. In all three tissues, isoprenaline-, terbutaline-, histamine- and 5-HT-induced adenylyl cyclase activation was reduced similarly in DCM and ICM. Moreover, in DCM and ICM, guanosine triphosphate (GTP)- (involving Gs and Gi) activated adenylyl cyclase was significantly diminished, whereas NaF-activated (involving only Gs) and Mn2+-activated (acting at the catalytic unit of the enzyme) adenylyl cyclase was unaltered. Left ventricular positive inotropic responses to beta1- (noradrenaline, dopamine, and dobutamine), beta2- (terbutaline), and beta1- and beta2-adrenoceptors (isoprenaline, adrenaline, and epinine), as well as H2-receptor (histamine) stimulation were significantly reduced. The extent of reduction was not different for each agonist in ICM and DCM. We conclude that in DCM and ICM, functional responsiveness of all cardiac Gs-coupled receptors is similarly reduced.

Adenylyl Cyclases↗
PubMed1998

Automated intraoperative detection of Doppler microembolic signals using the bigate approach.

BACKGROUND AND PURPOSE: We undertook this study to evaluate the performance of an automated detection software in the detection of Doppler microembolic signals (MES) during cardiac surgery. METHODS: Intraoperative monitoring was performed over two spatially separated vessel segments of each middle cerebral artery in 18 patients undergoing coronary artery bypass surgery (n= 16) or cardiac valve replacement (n=2). All monitoring sessions were saved on digital audiotape and subsequently played back to the same ultrasound machine, set up to automatically detect MES by evaluating the temporary delay in their appearance between the two segments, in the presence of an experienced examiner. Software sensitivity and specificity in MES detection were then evaluated, with the results of the human observer considered the gold standard. RESULTS: A total of 44,933 high-intensity signals (artifacts and MES) were evaluated. Overall sensitivity and specificity of the software, with the human observer considered the gold standard, were 64% and 78.5%, respectively, ranging from 54% to 96% and from 74% to 90% in individual patients. When the overall results of the software were compared with those of the human observer, kappa was 0.72. CONCLUSIONS: The tested software displayed a satisfactory specificity. Provided that the sensitivity is further improved, it could provide a valuable tool in intraoperative monitoring.

Artifacts↗
PubMed1998

[Primary liposarcomas of the mediastinum].

Primary liposarcomas of the mediastinum are rare neoplasms comprising less than 1% of mediastinal tumors. While in early stages often asymptomatic they may grow to an enormous size and then exhibit various clinical symptoms mimicking lung or heart disease by compression of adjacent intrathoracic organs. Intention of surgical treatment is to relieve the symptoms and to establish the histological diagnosis. Surgery alone may be curative in some cases. The role of additional radio- and chemotherapy remains questionable. We report two cases of primary mediastinal liposarcomas that were treated surgically in our institution.

Aged↗
PubMed1998

[Prognostic factors and subsequent indications for surgery in pulmonary metastasis of renal cell carcinoma].

Between 1975-1996, 39 patients underwent resection of pulmonary metastases from renal cell carcinoma. Multivariate analysis (COX model) for survival of preoperative risk factors showed that time of diagnosis (syn-/metachronous) of the metastases (p = 0.05) and the number of metastases (p = 0.01) were of prognostic significance. It is concluded that metastasectomy in patients with not more than six metachronous metastases after renal cell carcinoma has significant benefit and in cases of synchronous metastases or more than 6 pulmonary metastases indication for resection should be restricted.

Adult↗
PubMed1998

[Significance of the heart-lung machine for the concept of minimal invasive heart surgery].

Proinflammatory cytokines have been implicated in mediating myocardial dysfunction in a systemic inflammatory reaction following open heart surgery with extracorporeal circulation (ECC). The present study aimed to distinguish the surgical impact on cytokine release from the influence of ECC in a model of supported angioplasty. The extracorporeal circulation and not surgical trauma was found to be the main trigger of the systemic inflammatory response.

Adult↗
PubMed1998

Alloplastic sternal replacement in malignant sternal tumors. Case report and review of the literature.

Although not seldom as a palliative procedure, the preferred treatment of locally recurrent breast cancer or chest wall involvement by metastases is full-thickness chest wall resection. For closure and coverage of the defect various techniques are described. Autoplastic reconstruction is indicated for smaller defects, while larger defects usually require alloplastic materials, especially in case of chest instability after resection. We report the case of a 55-year-old female who developed a locally recurrent breast cancer with infiltration of the sternum 4 years after left sided ablation. En bloc resection of the chest wall including the complete sternum was followed by replacement with a computer-aided custom made polyethylene sternal prosthesis. With this procedure we stabilized the chest wall with protection of the underlying organs, avoided prolonged postoperative ventilation and achieved a satisfying cosmetic result.

Biocompatible Materials↗
PubMed1997

Alternative splicing of the primary Fas transcript generating soluble Fas antagonists is suppressed in the failing human ventricular myocardium.

Apoptosis of cardiomyocytes has been proposed as a factor contributing to severe heart failure. Since the trigger for apoptotic cellular suicide in nonischemic myocardium is unknown, we analyzed in human myocardial tissue the expression of the apoptosis-inducing membrane receptor Fas/APO-1 and of its alternatively spliced soluble isoforms which antagonize Fas by binding of the Fas ligand. Using reverse transcription polymerase chain reaction (RT-PCR) we found mRNA for Fas and 5 isoforms in nonfailing left ventricles, whereas Fas and only one isoform (FasExo6Del) were detectable in failing left ventricles. Standard calibrated, competitive RT-PCR revealed no significant increase of Fas mRNA in failing compared to nonfailing ventricles. However, the mRNA for FasExo6Del, expressed nearly on the same level as Fas in nonfailing ventricles, was decreased about 3-fold in failing ventricles. We propose that this altered expression of the Fas system renders the myocardium more susceptible for Fas-mediated apoptosis in end-stage heart failure.

Alternative Splicing↗
PubMed1997

Identification of Doppler microembolic signals with a bigate probe in patients with prosthetic heart valves.

BACKGROUND AND PURPOSE: The applicability of a bigate probe, simultaneously harvesting two spatially separated vessel segments, in the identification of Doppler microembolic signals (MES) was evaluated. METHODS: One hundred and ninety-seven patients with artificial heart valves were bilaterally monitored over two segments of each middle cerebral artery, with a minimal distance of 5 mm between them, using 2 MHz probes. Time delay in the appearance of high intensity transients between the two segments was calculated off-line, using dedicated software, integrated in the Doppler device. RESULTS: Bigate monitoring was feasible in 96% of patients. MES prevalence and counts were 37% and 26 (18-44) respectively. All but 8.8% of the 2932 MES signals recorded appeared in both Doppler channels, with a time delay of 4.4 (4.2-4.7) msec (range between 0 and 34 msec). Time delay in 97% of artifact signals was under 1 msec. Application of 1 msec as low and 20 msec as high cut-off point between MES and artifacts resulted in the correct identification of 97% of artifacts and 89.6% of MES. CONCLUSIONS: The multigate approach is a reliable method for identification of Doppler microembolic signals in patients with prosthetic heart valves. The value of this technique in other patient groups remains to be evaluated.

Aortic Valve↗
PubMed1997

[Systemic inflammatory reactions to extracorporeal therapy measures (II): Cardiopulmonary bypass].

About 65,000 cardiac patients undergo surgery annually in Germany with the assistance of cardiopulmonary bypass. The "post pump inflammatory response" (the systemic and myocardial inflammatory response syndrome post cardiac surgery), triggered at least in part by the cardiopulmonary bypass, contributes substantially towards morbidity (e.g., myocardial depression) and mortality in these patients. The main mechanisms underlying this inflammatory response are the complement cascade, the activation of blood cells, the release of cytokines and the induction to nitric oxide synthesis. The relative importance of each individual factor, however, is still a matter of debate. Scoring systems and measurements of tumor necrosis factor-alpha, as well as soluble tumor necrosis factor receptors, allow the early detection of an "escalating inflammatory response" in 2-10% of all patients, which is associated with a worse prognosis. Therapeutic attempts to suppress these systemic and myocardial inflammatory reactions focus on blockade of the complement system, coating of CPB membranes with heparin, leucocyte depletion and attenuation of leucocyte function, elimination of toxins and mediators by means of hemofiltration, as well as on the administration of antiproteases, antioxidants, oxygen radical scavengers and also of immune globulins.

Cardiopulmonary Bypass↗
PubMed1997

Single-lung transplantation in a patient with cystic fibrosis and an asymmetric thorax.

We report metachronous single-lung transplantation for cystic fibrosis after contralateral pneumonectomy. Kyphoscoliosis and mediastinal shift required careful donor-lung sizing with computed tomography and was not dependent on typical parameters. Severe reperfusion injury was treated with nitric oxide, C1-esterase inhibitor, and continuous venovenous hemodialysis. The patient was extubated on the fifth postoperative day and is alive and well. We conclude that single-lung transplantation after contralateral pneumonectomy for patients with cystic fibrosis and an asymmetric chest and evident lung volume mismatch may be an acceptable functional therapeutic option.

Child↗
PubMed1997

Results of cardiac operations in five kidney transplant patients.

Because of the paucity of literature reports about cardiac operations in renal-transplant patients we performed a retrospective study encompassing all such patients operated upon in our institution in 1993 and 1994. During this time 5 renal transplant patients underwent cardiac surgical procedures between 1 and 9 years after transplantation: in 4 patients coronary artery bypass grafting (CABG) was carried out and in one patient aortic valve replacement. We analyzed pre-, peri-, and postoperative data. Late results were obtained by questionnaire from the patients' primary physicians. Short- and long-term results were excellent. Mortality was 0%. At late follow-up (8-23 months) all patients were in NYHA class II or better. Postoperatively all patients experienced a clear improvement of their cardiac symptoms. None of the transplanted kidneys deteriorated. One patient who had to undergo intermittent hemodialysis preoperatively improved so much that she did not require any dialysis postoperatively. Although the total number of patients in this study is limited we believe it can be stated that renal transplant patients can undergo cardiac operations with generally good results.

Adult↗
PubMed1997

Functional role of beta2-adrenoceptors in the transplanted human heart.

In the transplanted human heart, beta-adrenoceptor subtypes change with time after transplantation: beta1-adrenoceptors tend to decline, whereas beta2-adrenoceptors are upregulated. The aim of this study was to determine whether, in the transplanted human heart, stimulation of beta2-adrenoceptors can induce heart-rate increases. For this purpose, we assessed in eight heart-transplant recipients (mean posttransplant time: 932 days) the effects of infusion of graded doses of isoprenaline (3.5-35 ng/kg/min) 120 min after pretreatment with the beta1-adrenoceptor antagonist bisoprolol (10 mg p.o.; beta1-adrenoceptor occupancy approximately 80%; beta2-adrenoceptor occupancy <5%) on heart rate in the recipient's native (innervated) and transplanted (denervated) sinus nodes. Isoprenaline, acting under these conditions predominantly at beta2-adrenoceptors, increased heart rate both in the recipient's transplanted and native sinus nodes in a dose-dependent manner; at each dose, increases were significantly higher in the transplanted than in the native sinus node. ED20 values (dose to increase heart rate by 20 beats/min) in the transplanted sinus node were 22.2 +/- 1.8 ng/kg/min, and in the native, >35 ng/kg/min (p < 0.01). We conclude that in the transplanted human heart, beta2-adrenoceptor stimulation does evoke increases in heart rate. The enhanced response to isoprenaline in the transplanted sinus node could be caused by the upregulated beta2-adrenoceptors or by the fact that during isoprenaline infusion, vagal activity increases, thus blunting the response in the native (innervated) but not in the transplanted (denervated) sinus node.

Adrenergic beta-Agonists↗
PubMed1997

Influence of oxygen ventilation on Doppler microemboli signals in patients with artificial heart valves.

BACKGROUND AND PURPOSE: The purpose of this study was to evaluate the influence of inhalation of 100% oxygen on microembolic signal (MES) counts in patients with artificial cardiac valves. METHODS: A total of 134 outpatients were examined. Transcranial Doppler baseline monitoring (45-minute duration) was performed in all patients under resting conditions. The first 30 patients subsequently underwent transcranial Doppler monitoring for at least 20 minutes under noninvasive positive pressure ventilation with 100% oxygen and for an additional 30 minutes under resting conditions. The same protocol was applied to all following patients with a baseline MES count > or = 10, while the examination was discontinued in the remaining patients. RESULTS: Baseline MES counts < 10, which remained unchanged during oxygen inhalation and the subsequent resting period, were observed in 26 of 30 initial patients. A total of 46 patients with MES counts > or = 10 were identified. Oxygen application was feasible in 43 patients. An exponential MES decrease was noted in 42 patients during oxygen inhalation (statistically significant in 38 patients), followed by a subsequent increase in 38 of 43 patients (statistically significant in 25 patients) under resting conditions. CONCLUSIONS: The exponential reduction of MES counts observed in this study corresponds to blood denitrogenation, thus strongly arguing for nitrogen bubbles as underlying embolic material in prosthetic valve carriers.

Adolescent↗
PubMed1997

Intracranial microembolic signals in 500 patients with potential cardiac or carotid embolic source and in normal controls.

BACKGROUND AND PURPOSE: We undertook this study to evaluate the prevalence and clinical correlations of Doppler microembolic signals (MES) in stroke-prone patients. METHODS: Patients with potential cardiac (n = 300) or carotid (n = 100) embolic source and control subjects (n = 100) were monitored with transcranial Doppler sonography for MES. Transthoracic (n = 192) and/or transesophageal (n = 134) echocardiography and carotid studies (continuous-wave Doppler, n = 181; color-coded duplex, n = 47) were performed in all patients with potential native cardioembolic source. Carotid disease was evaluated by means of continuous-wave Doppler (n = 87), color-coded duplex (n = 70), or intra-arterial angiography (n = 24) in patients with potential carotid embolic source. RESULTS: Overall MES prevalence was 23% in patients with potential native cardioembolic source (infective endocarditis [n = 7] 43%, left ventricular aneurysm [n = 38] 34%, intracardiac thrombus [n = 23] 26%, dilative cardiomyopathy [n = 39] 26%, nonvalvular atrial fibrillation [n = 24] 21%, valvular disease [n = 80] 15%), 55% in patients with prosthetic cardiac valves (mechanical [n = 77] 58%, porcine [n = 7] 43%, homografts [n = 5] 20%), 28% in patients with carotid disease (symptomatic [n = 46] 52%, asymptomatic [n = 54] 7%; P < .01), and 5% in control subjects. No relationship between MES counts and patients' age, sex, or actual medication was noted. The sensitivity and specificity of MES detection in identifying patients with potential embolic sources were 31% and 95%, respectively. CONCLUSIONS: Our study confirmed the reported clinical significance of MES in patients with carotid disease and the high specificity of this technique. The demonstrated low sensitivity of MES detection could be due to short monitoring duration or application of antihemostatic treatment. Prospective large-scale studies are needed to determine the definitive value of MES detection as a diagnostic method in patients with potential cardioembolic source.

Adult↗
PubMed1997

Doppler microembolic signals in children with prosthetic cardiac valves.

BACKGROUND AND PURPOSE: The aim of this study was the evaluation of the prevalence and counts of Doppler microembolic signals (MES) in children with prosthetic cardiac valves and their comparison to those obtained in corresponding adult patients. PATIENTS AND METHODS: Nine children and 43 adults with ATS valves implanted in the aortic position were monitored over both middle cerebral arteries with transcranial Doppler ultrasound. MES were identified on-line according to standard criteria. Heart rate and rhythm, valve type, size and duration, patients' height, International Normalized Ratio, and prevalence of neurological complications were obtained from all study participants. RESULTS: MES prevalence and counts were significantly higher in children compared with adult patients (100% versus 25.5% and 58 [18.5 to 115.5] versus 55 [2 to 10.5], median, 95% CI, respectively). No corresponding differences in valve duration of valve implant were evident, but children has heart rates and were significantly smaller compared with adults. A positive correlation between patients' size, heart rate, and MES counts was noted. CONCLUSIONS: MES counts in children with mechanical prosthetic valves are significantly higher compared with those in corresponding adults. We hypothesize that this is due to (1) the shorter distance between aortic valve and middle cerebral artery, since cavitation bubbles have a short life span and are bound to dissolve with time, and (2) the faster heart rate in children, resulting in a higher number of valve closures per minute.

Adolescent↗