An Implantable Carotid Sinus Baroreflex Activating System: Surgical Technique and Short-Term Outcome from a Multi-Center Feasibility Trial for the Treatment of Resistant Hypertension

OBJECTIVES

To assess perioperative outcomes and blood pressure (BP) responses to an implantable carotid sinus baroreflex activating system being investigated for the treatment of resistant hypertension.

METHODS

We report on the first seventeen patients enrolled in a multicenter study. Bilateral perivascular carotid sinus electrodes (CSL) and a pulse generator (IPG) are permanently implanted. Optimal placement of the CSL is determined by intraoperative BP responses to test activations. Acute BP responses were tested postoperatively and during the first four months of follow-up.

RESULTS

Prior to implant, BP was 189.6+/-27.5/110.7+/-15.3 mmHg despite stable therapy (5.2+/-1.8 antihypertensive drugs). The mean procedure time was 202+/-43 minutes. No perioperative strokes or deaths occurred. System tests performed 1 or up to 3 days postoperatively resulted in significant (all p < or = 0.0001) mean maximum reduction, with standard deviations and 95% confidence limits for systolic BP, diastolic BP and heart rate of 28+/-22 (17, 39) mmHg, 16+/-11 (10, 22) mmHg and 8+/-4 (6, 11) BPM, respectively. Repeated testing during 3 months of therapeutic electrical activation demonstrated a durable response.

CONCLUSIONS

These preliminary data suggest an acceptable safety of the procedure with a low rate of adverse events and support further clinical development of baroreflex activation as a new concept to treat resistant hypertension.

Thorakale Aorten-Stentgraftimplantation

BACKGROUND AND OBJECTIVE

Endovascular stent-graft placement is emerging as a novel therapeutic option in patients with disease of the descending thoracic aorta. Quality standards for performing stent-graft procedures as well as for pre- and postoperative patient management are lacking, so far. It was the aim of this present survey to assess the current therapeutic standard of thoracic aortic stent-graft placement in Germany.

METHODS

In a nationwide survey, a total of 206 vascular surgical, radiologic, cardiologic, and cardiothoracic surgical departments were contacted. Data concerning preoperative procedure planning, logistics, practical/technical issues of stent-graft placement, and postoperative patient management were evaluated using a standardized questionnaire comprising 29 items. Data analysis was performed using univariate analysis.

RESULTS

184 (89.3 %) of the 206 departments participated in the survey. Of these, 71 centers reported intending to perform or having performed thoracic aortic stent-graft placement. The survey overall represents 2267 endovascular stent-graft procedures performed in Germany between 1997/98 and 2003. On average, 7.4 stent-graft procedures/year were performed by each center, with half the centers performing fewer than 5 procedures/year. Thoracic aortic aneurysms was the main indication for endovascular stent-graft placement, followed by aortic dissection. There were significant differences between the different medical specialties which perform stent-graft procedures with respect to indications, choice of preoperative and intraoperative imaging methods, and technical equipment. There was strong agreement between the different centers concerning the necessity of a life-long follow-up after stent-graft placement, with computed tomography being the preferred imaging technique (90 % of centers).

CONCLUSION

The present survey documents an increasing use of endovascular stent-graft placement in patients with disease of the descending thoracic aorta. There were differences regarding the technical execution of this procedures between specialties with respect to indication, procedure planning, and practical-technical aspects of stent-graft placement.

Severe left ventricular failure after double lung transplantation: pathophysiology and management

Patients undergoing bilateral lung transplantation for end-stage pulmonary hypertension may experience various complications. We describe a patient who underwent transplantation for chronic pigeon breeder's disease, who had secondary pulmonary hypertension and deteriorated right heart function, and who developed severe left heart failure during the weaning phase after successful double lung transplantation. The patient was stabilized with catecholamines and an intra-aortic balloon pump. Left heart function increased within 7 days and normalized at Day 18. Otherwise, the post-operative course was uneventful.

[Surgical treatment of infective endocarditis: the Essen experiences]

BACKGROUND

Instead of immediate diagnosis and effective antibiotic treatment morbidity and mortality in infective endocarditis remains high. If the infection cannot be controlled or the disease progresses irreversible destruction of cardiac structures results.

SURGICAL THERAPY

In this case surgical therapy should be considered immediately. The outcome of surgical repair is not depending on the implanted prosthesis, but solely on timing of the operation.

[Experiences with a new transvenous electrode for left ventricular stimulation]

BACKGROUND

Left ventricular and biventricular pacing has recently been introduced as a new therapy for chronic heart failure in selected patients. We report our initial experience with a new electrode for transvenous left epicardial pacing via tributaries of the coronary sinus.

PATIENTS AND METHOD

Inclusion criteria were: chronic heart failure NYHA > or = II, QRS-duration > 120 ms, left ventricular ejection fraction < 35%. Dual chamber pacemakers (CPI Contak TR) or defibrillators (CPI Contak CD) designed for atrial triggered biventricular stimulation were implanted in conjunction with the CPI Easytrak-lead for left ventricular pacing in a coronary vein. Lead placement was achieved via a subclavian vein access and a preformed guiding catheter for coronary sinus insertion.

RESULTS

In 13 of 16 patients (81%) the left ventricular lead was implanted successfully in a mid to distal posterior or anterolateral vein. Lead insertion could not be achieved in 2 patients with significant cardiomegaly and right atrial enlargement (12.5%), while 1 patient with a history of myocardial infarction and small anterior ventricular aneurysm had inacceptable high left ventricular pacing thresholds intraoperatively. The implantation was well tolerated by all patients without complications. There was no case of lead dysfunction (mean follow-up time: 142 +/- 126 days). Intraoperative electrode measurements and chronic parameters (> or = 3 months, n = 8) are given in Table 1.

CONCLUSION

In the past left ventricular pacing has mainly been achieved by epicardially placed electrodes after thoracotomy with conventional electrodes. This new approach for chronic left ventricular pacing uses the familiar transvenous over-the-wire technique in combination with a newly developed guiding catheter and electrode for pacing in left epicardial veins. Lead placement was shown to be safe and success rate was higher than in previous reports with standard electrodes. We conclude that left epicardial lead placement with the over-the-wire technique and a preformed guiding catheter for coronary sinus access presents as a safe and maybe more efficient method for left ventricular pacing.

Disruption of the silver and non-silver coated sewing cuff of a new generation bileaflet valve prosthesis during aortic valve replacement: report on four cases

OBJECTIVES

New generation bileaflet valve prostheses with a silver-coated sewing cuff like the St Jude Medical (SJM((R)) Regent) model are designed to offer a larger valvular orifice as well as a better resistance to postoperative prosthetic endocarditis, at the expense of a smaller sewing cuff.

METHODS AND RESULTS

We report on four cases of aortic valve replacement where during the implantation procedure the fixation cuff disrupted, leading to the exchange of all four valve prostheses. This happened three times with silver- coated sewing cuffs and after withdrawal of the silver- coated cuff prostheses from the market, once with a non silver- coated sewing cuff. This was due to the arbitrary cutting of the cuff fixation suture at the ventricular side of the prosthesis, although the implantation was performed according to the recommendations of the company. This problem didn't occur previously, using other models of the same manufacturer, although the sewing cuff had been fixed in the same technique.

CONCLUSION

Fixation of smaller sewing cuffs of mechanical valve prostheses with a critically exposed fixation suture at the ventricular side of the prosthesis represents a significant risk for disruption during the implantation process through cut off by chance. We recommend meticulous inspection of the sewing cuff for signs of disruption before seating the valve into position. During follow-up particular attention should be paid to valve dislodgement and leakage. The company was informed and advised by us to modify the fixation of the prosthetic annulus of the SJM((R)) Regent valve, which has led to an alternative cuff design, called the SJM Flex cuff.

Sepsis and catecholamine support are the major risk factors for critical illness polyneuropathy after open heart surgery'

BACKGROUND

Critical illness polyneuropathy (CIP) remains a problem after open heart surgery. Recently, we reported about a retrospectively performed study pointing out that sepsis, the application of higher amounts of catecholamines and intervention such as chronic venovenous hemodiafiltration may be involved in the onset of CIP. A prospectively performed study is presented in order to evaluate the significance of risk factors initially after open heart surgery.

METHODS

From June 1997 until September 1998, patients undergoing open heart surgery and being ventilated beyond 3 days were prospectively enrolled in the study and underwent a standard protocol of electromyographic investigation in order to determine CIP. Several items were recorded: amount of catecholamines, serum levels of urea, creatinine, albumin, and glucose. The duration of sepsis and chronic venovenous hemodiafiltration were reevaluated. Additionally the age, the left ventricular end-diastolic pressure prior to the operation, the time of ICU stay and the time of ventilatory support were compared.

RESULTS

Within the observation period, 37 adult patients could be enrolled in the study, whereas 12 patients did develop CIP and 7 patients did not. Patients developing CIP required significantly different amounts of epinephrine (0.17 +/- 0.02 vs. 0.09 +/- 0.01 mg/kg/day, p < 0.05, t-test) higher amounts of norepinephrine (0.06 +/- 0.02 vs. 0.02 +/- 0.01 mg/kg/day, p<0.05, t-test), and lesser dosages of dobutamine (2.2 +/- 0.5 vs. 4.9 +/- 0.7, p<0.05, t-test). After cardiac surgery, the plasma levels of urea was initially significantly elevated in patients developing CIP (127.4 +/- 10.5 vs 97.3 +/- 18.5, p<0.05, t-test) Patients suffering from CIP stayed significantly longer in the ICU (40.3 +/- 11.7 vs. 19.6 +/- 11.3 days, p < 0.05 t-test) with an extended time of ventilator support. (769.6 +/- 05.0 vs 295.0 +/- 134.0 hours, p<0.05, t-test). Patients of the CIP group were suffering significant longer from sepsis than patients without CIP.

CONCLUSIONS

Sepsis and catecholamine support and an increased level of urea were associated with the development of CIP. The prevention of sepsis and a modulation of the catecholamine support in order to improve microcirculatory flow may reduce the onset of CIP in patients undergoing open heart surgery.

Interruption of bronchial circulation leads to a severe decrease in peribronchial oxygen tension in standard lung transplantation technique

OBJECTIVE

In clinical practice lung transplantation is the only procedure where the transplanted organ is left without its own arterial perfusion. With the interruption of the bronchial arteries the nutritive support is dependent on collateral flow by the pulmonary artery and the oxygen tension of desaturated central venous blood, representing an abnormal physiology.

METHODS

To analyze this problem systematically, we used a standard single left lung transplantation model in the pig (n = 12). In accordance with the clinical standard, lung preservation was performed with modified Euro-Collins solution with addition of prostacycline. The duration of ischemia was set to 4 h. Before and after single left lung transplantation tissue oxygen tension in the peribronchial tissue was measured with Licox tissue pO2 microprobes. For validation, the myocardial tissue oxygen tension was recorded simultaneously. The hemodynamic assessment included continuous flow measurement of the left and right pulmonary artery using Transsonic ultrasound flow probes. After transplantation the animals were observed for 4 h. For hypothetic augmentation of collateral blood flow to the peribronchial tissue we administered Nitric oxide (10 ppm) to the ventilation in six pigs (group B). Six pigs (group A) served as a control without the addition of nitric oxide (NO). All pigs were ventilated with a FiO2 of 0.5 resulting in paO2 values between 160 and 200 mmHg.

RESULTS

In both groups single lung transplantation led to a significant decrease in peribronchial tissue oxygen tension throughout the observation period. Pre-Tx values of peribronchial tissue oxygen tension (38.31 +/- 6.56 mmHg) decreased to 9.72 +/- 2.55 mmHg in group A and 10.3 +/- 3.61 mmHg in group B after 4 h, which could not be altered by a FiO2 of 1.0 (P < 0.0001). The addition of NO in group B led to a significantly augmented flow in the left pulmonary artery (0.63 +/- 0.31 l/min in group B vs. 0.46 +/- 0.26 l/min group A, P < 0.001) representing 67 vs. 49% of the pre-Tx flow in groups B and A, respectively, but the peribronchial tissue oxygen tension was not influenced (P > 0.05). In both groups A and B, the central venous pO2 did not differ in the postoperative period (41.83 +/- 3.27 mmHg group A vs. 43.26 +/- 2.98 mmHg group B) and was kept in a comparable range to the pretransplantation values (45.23 +/- 3.41 mmHg pre-Tx).

CONCLUSIONS

The persistence of a very low peribronchial tissue oxygen tension in the early phase after lung transplantation cannot be influenced by improved pulmonary artery flow and solely relates to the central venous pO2, which cannot be augmented by the addition of NO. This mechanism might be a trigger for anastomotic healing problems, infectious complications and later development of obliterative bronchiolitis (OB).

Critical illness polyneuropathy: a new iatrogenically induced syndrome after cardiac surgery?

OBJECTIVE

Critical illness polyneuropathy (CIP) is a newly described severe complication after open heart surgery leading to tetraplegia for weeks to months. The purpose of the study was to gather further information on critical illness polyneuropathy developing in patients after cardiac surgery and to evaluate the hypothetical risk factors possibly related to the onset of this neurological disorder.

METHODS

From July 1994 to October 1995, 7 out of 1511 patients undergoing open heart surgery developed critical illness polyneuropathy, which was diagnosed on the basis of electromyographic and nerve conduction features. The only common clinical finding was an intensive care unit (ICU) stay beyond seven days, therefore a similar group of 37 patients staying longer than seven days in the intensive care unit during the same period of time was evaluated and retrospectively compared to the 7 patients developing critical illness polyneuropathy. Univariate analysis of several traits was performed to evaluate possible risk factors.

RESULTS

4 Out of 7 patients in the CIP group died, all due to multiple organ failure, in contrast to 3/37 patients in the control group, again due to multiple organ failure. Patients developing CIP were staying significantly longer in the ICU (62+/-3 versus 14+/-8 days, P < 0.01) and had a significantly longer time on ventilator support (50+/-28 versus 7+/-13 days, P < 0.01) The incidence of sepsis was significantly higher in the CIP group than in the control group (85.7 versus 10.8%, P < 0.01). Compared to the control group the proportion of patients receiving corticosteroids (100 versus 10.8%, P < 0.01) and increased dosages of epinephrine and norepinephrine was higher in the CIP group (85.7 versus 35.1%, P < 0.05). Furthermore, the proportion of patients requiring chronic venovenous hemodiafiltration was significantly elevated in the CIP group (85.7 versus 5.4%, P < 0.01).

CONCLUSIONS

CIP, despite it's benign nature due to it's spontaneous remission in patients who survive, is a disturbing complication following cardiac surgery which is associated with high mortality, a prolonged stay in the ICU, as well as an extended time on ventilator support. Interventions like chronic hemodiafiltration, the application of corticosteroids and the administration of high doses of catecholamines are more frequent in patients with CIP. Whether this indicates a causal relationship remains to be elucidated.

"Cardioplegia on the contractile apparatus level": evaluation of a new concept for myocardial preservation in perfused pig hearts

The concept of a reversible desensitization of the myocardial contractile apparatus for calcium by 2,3 Butanedione Monoxime (BDM) as a method to improve the myocardium's tolerance to cold ischemia was evaluated in normal pig hearts (n = 14). The results were compared to those obtained after application of Bretschneider's HTK cardioplegic solution.

METHODS

Series I) After BDM treatment (concentrations: 0-30 mmol/L) the isometric force output and the intracellular calcium transients (measured using the FURA-2 ratio method) of electrically driven (1 Hz) isolated left-ventricular muscle strips excised from beating pig hearts (n = 14) were recorded simultaneously in order to analyse the mode of action of BDM; Series II) The cardioprotective effects of BDM (30 mmol/L) and Bretschneider's cardioplegic solution (HTK) were compared in a large-animal model: after "in situ perfusion" of pig hearts with either 2000 ml ice-cold BDM solution (30 mmol/L) (n = 7) or 2000 ml HTK (n = 7) the hearts were explanted and stored at 4 degrees C in the same solutions for up to 42 h. The contractile properties of muscle fibres, excised after storage periods of 8, 24, and 42 h from these hearts were analyzed in terms of isometric force development and isotonic shortening. 280 muscle fibres from 14 pigs were used for measurements.

RESULTS

Series I) In pig myocardium a dose-dependent reduction of isometric force development was found after BDM application. The shape and the amplitude of the intracellular calcium transient were also affected by BDM. At 30 mmol/L BDM no force development could be elicited despite the presence of an intracellular calcium transient (amplitude < 70% of the control). Series II) Shortening, calcium transient, and force of left-ventricular muscle strips of pig myocardium excised after storage periods for up to 42 h showed complete recovery when BDM was applied. In contrast HTK perfusion allowed complete recovery of these parameters when the storage period did not exceed 6 hours.

CONCLUSION

Under the given experimental conditions reversible desensitization of the contractile apparatus for calcium results in a considerable prolongation of the tolerance to cold ischemia in explanted pig hearts. The present study shows that the protective effects of BDM are not only present when isolate muscle fibres were stored (and the extracellular space is large) but also after storage of complete hearts in a solution in a solution containing BDM. Thus BDM may become a useful agent to enlarge the storage period of donor hearts in heart transplatation considerably.

Increased resistance against shortening in myocardium from recipient hearts of 7 patients transplanted for dilated cardiomyopathy

The contractile behaviour of demembranized atrial and ventricular myocardium of 7 patients transplanted for end-stage heart failure (ESHF) was analyzed. Atrial muscle specimens of patients undergoing coronary artery bypass surgery (n = 9) and pig papillary muscle were used as reference preparations (n = 9). Extreme care was taken for dissection and mounting the muscle fibres (0.3 x 6 mm) in order to keep the passive series compliance small. Calcium sensitivity, cross-bridge cycling rate (estimated by the force-clamping technique and calculation of the shortening velocity at zero load [Vmax]) and isometric force development were measured. Analysis on light- and electronmicroscopic level was carried out.

RESULTS

1) Calcium sensitivity was not altered in ESHF patients; 2) the velocity of the force generating process (cross-bridge cycling rate) was normal in ventricular and reduced in atrial ESHF myocardium, 3) maximum isometric force development was reduced in ventricular, but not in atrial myocardium of ESHF patients, and 4) Vmax was significantly reduced in ventricular and atrial ESHF myocardium (p < 0.0001). Perimysial and endomysial fibrosis was present in ventricular, not in atrial myocardium of ESHF patients.

CONCLUSION

A normal cross-bridge cycling rate in left-ventricular ESHF myocardium combined with a decreased capability of muscle shortening indicates the presence of a resistance against shortening localized either on the cross-bridge level or/and due to intra- and pericellular fibrosis. Left-ventricular contractile dysfunction in patients with end-stage heart failure may be related to a normal contractile apparatus contracting within an abnormal intracellular or interstitial environment.

Contractile behaviour of skinned papillary muscle in mitral valve disease

The contractile behaviour of Triton-X 100 skinned left ventricular papillary muscle from 19 patients undergoing cardiac surgery for mitral valve stenosis: n = 6, mitral valve incompetence: n = 7, or combined mitral valve disease: n = 6 was analyzed. At supramaximal activation the "vibration induced force clamping technique" was used for isometric analysis of time course and extent of isometric postvibration force recovery. Afterloaded contractions were applied for extrapolation of the maximum shortening velocity at zero load (Vmax). The Calcium sensitivity was analysed by variation of the free EGTA-buffered Calcium concentration at a passive resting force of 2 mN at 26 degrees C. In different types of mitral valve disease the characteristics of isometric force development were unaltered in terms of maximum force development, force per square mm, Calcium sensitivity and the time course of isometric contraction after force clamping. However the capability to shorten as expressed by Vmax was reduced in mitral valve incompetence (3.87 +/- 0.37 ML/s) as compared with mitral valve stenosis (5.29 +/- 0.35 ML/s) or combined mitral valve disease (4.83 +/- 0.51 ML/s). The ratio between the inverse value of Vmax and the time constant of isometric force development after force clamping was significantly different in mitral valve incompetence as compared with other types of mitral valve disease (p < 0.0001). These data argue for the presence of different resistances against shortening in various types of mitral valve disease, due to altered cross-bridge cycling characteristics or to morphological factors.

Analyzing contractile responses in demembranized pig papillary muscle fibres: the influence of calcium, resting force, and temperature

The influence of calcium, resting force and temperature on the contractile behaviour in isolated demembranized ("skinned") pig papillary muscle fibers (n = 36) was analysed. Demembranisation excludes the influence of any membrane related processes on the contractile response as the myofilaments are in direct contact with the bathing medium. Resting force (1 mN-9 mN), temperature (22 degrees C or 32 degrees C) and pCa 7.0-4.3 were varied and the contractile response was analyzed by studying the time constant and the extent of post vibration force recovery (PVFR) of the activated preparations (the vibration method). Additional constant-load experiments and detection of sarcomere-length were carried out. There was an inverse-linear relationship between time constants of post vibration force recovery and maximum shortening velocity as estimated by constant load experiments. Resting force affected the extent of force development but not the time constant of post vibration force recovery and modulated the pCa-force relationship without altering the calcium concentration required for half-maximal activation (calcium sensitivity). In contrast lowering the bath temperature from 32 degrees C to 22 degrees C caused a significant leftward shift of the pCa-force relationship potentially due to changes of the contractile filaments' calcium sensitivity. The effect of temperature on the myocardial contractile system is of special interest as hypothermia is frequently used in cardiac surgery. Analysis of alterations of the contractile proteins' calcium sensitivity during the rewarming period of the patient may provide further insight in the pathophysiology of reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

[A preclinical study of the organ distribution and radiation dosage of radioiodinated iodolisuride]

The distribution in rats of 125I-iodo-lisuride was studied. Three rats each were sacrificed at fixed intervals between 5 min and 24 h p.i., and the radioactivity was measured in isolated organs and parts of the body. The organ distribution and biexponential blood disappearance were similar to values for unlabeled lisuride. The radiation dose was estimated for man assuming a 123I label. The resulting doses were comparable to those from other radiopharmaceuticals in clinical use.

Vorklinische Untersuchung zur Organverteilung und Strahlenbelastung von Radiojod-Jodlisurid

The distribution in rats of 125l-iodolisuride was studied. Three rats each were sacrificed at fixed intervals between 5 min and 24 h p. i., and the radioactivity was measured in isolated organs and parts of the body. The organ distribution and biexponential blood disappearance were similar to values for unlabeled lisuride. The radiation dose was estimated for man assuming a 123l label. The resulting doses were comparable to those from other radiopharmaceuticals in clinical use.

[Nuclear magnetic resonance detection of a mediastinal bronchogenic cyst]

A case of mediastinal bronchogenic cyst is discussed. CT showed high absorption values, while in MRI very short T1 values were found. The reasons for these findings are discussed.

Allergoprints in horse allergic children

In order to determine the allergenic activity of five purified horse allergens, 22 children allergic to horses according to history, skin test, and leukocyte histamine release were evaluated. Washed leukocytes from all patients were tested for allergen-induced histamine release utilizing four epidermal horse allergens (Ags 6, 9, 11, and 15) and horse serum albumin. Crossed radioimmunoelectrophoresis was carried out with a standard horse dander extract and serum from each patient. The results showed considerable variation in the individual allergoprints. Ag 11 had the highest mean allergenic activity. Sensitivity to horse serum albumin was demonstrated three times. Our data show that the amount of serum IgE antibodies bound by horse allergens correlates significantly with the capacity of the allergens to induce histamine release from washed leukocytes.