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Biomedical subjects

G Fenchel

Publications and source records attributed to G Fenchel.

At least 19 recordsLinked to original sources
PubMed1995

[Improvement of perioperative hemodynamics and gas exchange by inhalation of nitric oxide in children with congenital cardiopulmonary defects].

OBJECTIVES: In critically ill infants and children before or after surgery for congenital cardiopulmonary disease it was evaluated whether continuous NO inhalation can reduce pulmonary artery pressure (PAP) and improve arterial oxygen saturation (SaO2). METHODS: All patients (n = 24; age 1 day-6.5 years) were intubated and artificially ventilated. They had either secondary pulmonary hypertension (n = 16), acute respiratory distress syndrome (n = 3), or reduced SaO2 (n = 5) due to pulmonary hypoperfusion. NO was introduced into the afferent limb of the ventilator circuit close to the endotracheal tube, while continuously measuring the inspired NO and O2 concentrations. The initially applied concentration of NO was 20 +/- 2.0 ppm. RESULTS: The hemodynamic condition and/or oxygen saturation was significantly improved by NO in 23 patients (95%). Mean PAP declined significantly from 45 +/- 7 to 28 +/- 3.7 mm Hg, while mean systemic arterial pressure remained constant (56 +/- 2.1 vs. 58 +/- 2.5 mm Hg). This was related to a selective reduction in pulmonary vascular resistance by 48 +/- 8.5%. SaO2 increased significantly (p < 0.05) from 83 +/- 2.5% to 93 +/- 1.5% due to a decreased intrapulmonary right-to-left shunt. NO therapy was applied with a median of 6 days (range 1.5-36 days). During NO inhalation methemoglobin concentration was significantly increased (0.77 +/- 0.05% vs. 1.46 +/- 0.15%), but neither was oxygen transport capacity affected, nor was any evidence for accumulation observed. Using a model ventilatory circuit, a nitric dioxide (NO2) formation of 1.14 +/- 0.11% of the applied NO concentration was measured, i.e. approximately 0.5 ppm NO2 at 40 ppm NO. This amount of NO2 in the inspired gas is well below toxicologically relevant concentrations. CONCLUSIONS: Low-dose NO inhalation selectively reduces PAP and improves SaO2 in children with congenital cardiopulmonary disease during perioperative intensive care. It is expected that the overall hemodynamic improvement is related to a reduced afterload of the subpulmonary ventricle without changes in coronary perfusion pressure, as is often observed with other vasodilators applied intravenously. We recommend an upper dose limit of 40 ppm NO for continuous NO inhalation to avoid possible toxicologically relevant NO2 concentrations.

Administration, Inhalation↗
PubMed1994

[Transvenous sonography of the peripheral arterial vessels. The initial clinical results].

Intravascular ultrasound with 20 MHz/6.2-French transducer systems was used for arterial imaging via a transvenous approach. In 20 patients suffering from chronic arterial occlusive disease, 15 iliac arteries were evaluated during diagnostic angiography and 5 femoropopliteal arteries during balloon angioplasty (n = 3) and laser-assisted angioplasty (n = 2), respectively. Transvenous sonography did not allow differentiation of arterial wall layers and determination of vessel diameters as is usually possible during intraarterial sonography. Visualisation of iliac arteries was incomplete. In femoropopliteal vessels, guide wires could be detected within the arterial lumen but not in complete occlusions. Delivery of pulsed laser energy induced bright echoes near the catheter tip within a distance of 1-2 cm. Transvenous sonography is insufficient for monitoring of peripheral angioplasty; however, improved imaging quality might be possible at lower frequencies.

Aged↗
PubMed1991

Intraoperative valvuloplasty in calcific aortic stenosis: a study comparing the mechanism of a novel expandable device with conventional balloon dilatation.

In selected patients with calcific aortic stenosis, balloon valvuloplasty is an intermediate alternative to surgery. The effect of balloon valvuloplasty to increase valve area, however, is limited and the restenosis rate is high during follow-up. To improve the results and reduce the complication rate, a new device for valvuloplasty of calcific aortic stenosis was developed. This system consists of three expandable prongs mounted on a freely movable catheter tip. To evaluate the efficacy of this new device, valvuloplasty was performed in 10 patients with severe aortic stenosis intraoperatively just prior to valve replacement. Comparison was made with the results of conventional balloon dilatation performed in an additional 20 patients during surgery. Using the new device, the relative orifice area increased from 10 +/- 3% before to 20 +/- 6% following intervention. However, in only one patient was a considerable increase of static valve area (greater than 15%) found. The results were comparable to the effect of conventional balloon dilatation, which led to an increase of orifice area from 12 +/- 7% to 24 +/- 10%. With both systems, the best results were achieved in patients with aortic stenosis and significant commissural fusion. In contrast, in bicuspid or tricuspid valves without fused commissures the effect of the intervention was limited. Because complete obstruction of the aortic valve does not occur during dilatation, this new device might be superior to conventional balloon dilatation. Preselection of patients according to the morphology of the valve seems mandatory to improve the success and reduce the complication rate of valvuloplasty in aortic stenosis.

Aged↗
PubMed1991

Early and late results of the modified Waterston shunt with PTFE grafts for palliation of complex congenital cyanotic heart disease in neonates.

During a 12 year period from 1978 to 1989, 35 infants under 4 weeks of age underwent palliative surgery for complex congenital cyanotic heart disease with a short (1-1.5 cm) PTFE graft between the ascending aorta and the right pulmonary artery (modified Waterston shunt). Twenty-three infants had pulmonary atresia and 14 had severe pulmonary stenosis. Underlying cardiac lesions were tetralogy of Fallot (n = 11), single ventricle (n = 7), transposition complexes (n = 6), and intact ventricular septum and hypoplastic right heart syndrome (n = 13). There were 4 early deaths (10.7%) in the entire series, 2 of which were shunt related. Three of the 4 occurred during our initial experience with this shunt in 1978 and 1979. They led to the modified Waterston shunt being abandoned for 3 years in favor of other shunt procedures. Since 1983 one early death occurred in 28 infants (3.5% mortality) with no death in the latest 26 patients. All patients were followed up between 6 and 108 months. There were 4 late deaths, one of which was shunt related. We observed a significant difference in the shunt patency rate between 4 and 5 mm grafts: palliation was adequate after 2 years in 52% of the patients when a 4 mm graft was used and in 89% of the 5 mm graft group (p less than 0.005). Reshunting was necessary in 7 infants between 5 and 60 months after primary surgery. Recatheterization was performed in 17 infants for suspected shunt failure (n = 6) or diagnostic reasons (n = 11).(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1990

[Results of emergency aortocoronary venous bypass surgery after failed percutaneous transluminal coronary angioplasty in patients with unstable angina pectoris].

During a 4-year period from January 1985 to December 1988 140 patients underwent percutaneous transluminal coronary angioplasty (PTCA) of the culprit-vessel for unstable angina. Seventeen patients (12%) needed emergency aorta coronary bypass surgery (ACVB) for failed angioplasty. In 15 cases the culprit-vessel was the LAD and in 2 cases a dominant right coronary artery. Only in 2 cases a history of myocardial infarction was present. Twelve patients were in hemodynamic stable condition after arriving in the operating-room. Five patients were hemodynamic unstable, 4 of them were in cardiogenic shock. Four patients died representing an operative mortality rate of 23%. Three patients died from pump failure despite intraaortic balloon counterpulsation in 2 cases. One patient died from cerebral damage 12 day after surgery. All patients who died were in cardiogenic shock preoperatively. Two patients who survived suffered an extensive myocardial infarction. Thus including the patients who died from pump failure the perioperative infarction rate was 30%. From these results it is concluded that emergency ACVB after failed PTCA of the culprit-vessel in patients with unstable angina results in a significant higher mortality and morbidity as compared with patients who had primary surgery for unstable angina. The prognosis of patients after failed PTCA for unstable angina depends on the hemodynamic situation thereafter and becomes worse in patients with cardiogenic shock.

Adult↗
PubMed1988

Relationship between the high-energy phosphate content and various left ventricular functional parameters of the normal and hypertrophied heart after global ischemia and reperfusion.

Using an isolated rat heart preparation (Langendorff perfusion, perfusion pressure 100 cm H2O) the correlation between the high-energy phosphate content and various left ventricular (lv) functional parameters of the hypertrophied heart (spontaneous hypertensive rats lv/body weight ratio 3.6 +/- 0.5 x 10(-3) was determined after normo- (30 min) and hypothermic (25 degrees C, 120 min) cardioplegic arrest and reperfusion, and compared with normal hearts (Wistar rats lv/body weight ratio 2.0 +/- 0.3 x 10(-3). St. Thomas Hospital solution was used as the cardioplegic agent. Before ischemia hypertrophied hearts had a significantly higher developed left ventricular pressure, pressure rate product and dp/dtmax, but a significantly lower ATP and total adenine nucleotide content. Irrespective of the mode and temperature of cardiac arrest there was a strong correlation both for normal and for hypertrophied hearts between the high-energy phosphate content expressed as ATP, total adenine nucleotides or the "energy charge" and the left ventricular functional parameters pressure rate product and dp/dtmax. The correlation coefficient ranged from 0.80 to 0.89 and was highest when the ATP content was plotted against pressure rate product (r = 0.89). There was a different slope for normal and hypertrophied hearts with a steeper decline of the left ventricular function in hypertrophied hearts for any given reduction of the myocardial adenine nucleotide content. Our results indicate that a similar reduction of the ATP or total adenine nucleotide content in both the normal and hypertrophied heart reduces left ventricular function to a greater degree in the hypertrophied heart.

Adenosine Diphosphate↗
PubMed1987

[Percutaneous transluminal coronary angioplasty and aortocoronary bypass surgery in unstable angina pectoris and coronary multivessel disease].

In 113 patients demonstrating the clinical syndrome of unstable angina, acute-stage coronary angiography revealed multivessel disease. Acute PTCA of the ischaemia-related coronary artery or bypass grafting was performed depending on angiographic criteria. Of the total of 68 patients in whom PTCA was performed, 45 had two-vessel disease (2 vd) and 23 three-vessel disease (3 vd). 12 of the 45 patients with bypass operation had a left main stem stenosis, whereas 33 had three-vessel disease. The primary success rate of PTCA was 81%, 89% in patients with 2 vd and 70% in patients with 3 vd. Acute post-PTCA bypass grafting was necessary in 2 patients having 2 vd and in 5 patients suffering from 3 vd. 5 of the 68 patients treated with PTCA developed a transmural myocardial infarct and one patient died after PTCA and emergency bypass surgery. 8 of the 45 operated patients had a perioperative or postoperative myocardial infarct and 5 patients died intraoperatively or postoperatively. The overall morbidity was 11.5%, and the mortality of hospitalised patients was 5.3% (6/113). Combination of PTCA with emergency bypass grafting offers a new and effective treatment with an acceptable risk even in multivessel disease patients and in those having unstable angina pectoris. The additional use of PTCA definitely improves therapeutic management in this high-risk population.

Angina Pectoris↗
PubMed1986

Function and energy-rich phosphate content of the hypertrophied ventricle after global ischemia and reperfusion.

Using an isolated rat heart preparation (Langendorff perfusion, perfusion pressure 100 cm H2O) the response of the hypertrophied heart (spontaneous hypertensive rats lv/bw ratio 3.6 +/- 0.5) to global normothermic (30 min) and hypothermic (25 degrees C, 120 min) ischemic and cardioplegic arrest and reperfusion (30 min) was examined and compared with normal hearts (Wistar rats lv/bw ratio 2.0 +/- 0.3). St. Thomas solution and verapamil (2 mg/l Ringer solution) were used as cardioplegic agents. Before ischemia hypertrophied hearts had a significantly higher pressure-rate product, a lower myocardial perfusion/g myocardium and a lower myocardial ATP and adenine nucleotide content. Unmodified ischemia reduced myocardial function in the hypertrophied hearts to a greater degree than in normal hearts in both normo- and hypothermia. St. Thomas solution and verapamil protected significantly the myocardial function in the normal and hypertrophied heart after normothermic ischemia in a similar manner (60-70% of the initial value). In the hypertrophied ventricle ATP decay and adenine nucleotide loss was greater in verapamil than in St. Thomas solution treated hearts. In hypothermic ischemia only St. Thomas solution protected left ventricular function and adenine nucleotide loss in both normal and hypertrophied hearts. Verapamil was ineffective in the normal ventricle and protected left ventricular function but not the ATP and adenine nucleotide decay in the hypertrophied heart.

Animals↗
PubMed1985

Relationship between the myofibrillar ATPase activity of human biopsy material and hemodynamic parameters.

The myofibrillar ATPase activity and pyrophosphate gel electrophoretic pattern of native myosin of fresh human left ventricular papillary muscles were examined in 52 cases of mitral valve replacement. The myofibrillar ATPase activity of hypertrophied myocardium did not differ from that of non-hypertrophied myocardium (mean +/- SD, 36.2 +/- 8.7 vs 31.8 +/- 8.6 nmolPi/mg/min, ns) and there was no significant difference in myofibrillar ATPase activity as a function of left ventricular enddiastolic pressure. Pyrophosphate gel electrophoresis of myosin revealed the presence of two components. It is questionable whether the component of higher electrophoretic mobility (approximately 25-35% in concentration) is identical with rat ventricular myosin VM-1 because an increase in this component seems to correlate with a decrease of myofibrillar ATPase activity, its concentration was significantly higher in the hearts with left ventricular hypertrophy, high enddiastolic pressure, high aortic pressure or low cardiac index. From these results, it is not necessarily clear whether hemodynamic overload in valvular heart diseases can alter left ventricular myofibrillar ATPase activity, but it can be said that the overload influences the concentration of the two components of native myosin revealed by pyrophosphate gel electrophoresis.

Adenosine Triphosphatases↗
PubMed1979

Ultrastructural and biochemical changes of human papillary heart muscle during different methods of induced cardiac arrest.

To determine the protective effects of different methods of cardioplegia, studies on ATP/lactate levels and ultrastructure were performed in human papillary muscles obtained during mitral valve replacement. In group I (n = 5), plain ischemic arrest in hypothermia (systemic venous temperature = 24 degrees C) was accomplished. In group II (n =12), the heart was arrested by injection cardioplegia using magnesium-aspartate-procaine at systemic venous and myocardial temperatures of 24 degrees C. In group III (n = 12) Bretschneider infusion cardioplegia at systemic venous and myocardial temperatures of 26 degrees C and 19 degrees C respectively was applied. With regard to ultrastructural changes there were no clearcut differences in the three methods of hypothermic cardiac arrest after 60 minutes of ischemia. Ischemic changes tended to be slightest in group III (infusion cardioplegia). ATP decay and lactate increase were significant in group I and moderate to minimal in groups II and III after the same period of time. It is concluded that for aortic cross-clamp times up to 60 minutes, body hypothermia and injection cardioplegia using magnesium-aspartate-procaine at a myocardial temperature of 24 degrees C provide adequate protection of the myocardium. For ischemia times beyond 70 minutes, profound myocardial hypothermia below 20 degrees C is preferred.

Adenosine Triphosphate↗
PubMed1978

[The protective effect of magnesium-aspartate-procaine cardioplegia on the hypertrophied left ventricle of the mini-pig (author's transl)].

After induction of left ventricular hypertrophy by supravalvar constriction of the ascending aorta in mini pigs (ATP and lactate) were measured under different cardioplegic conditions. In normothermia and plain anoxic arrest ATP decrease and lactate increase were significantly slower in hypertrophied myocardium compared to normal myocardium. Injection cardioplegia using magnesium-aspartate-procaine at 37 degrees C did not influence the ATP decrease and lactate increase in the hypertrophied ventricle, whereas in the normal heart it showed some protection according to these parameters. Optimal ATP preservation and the lowest lactate increase rate were achieved in left ventricular hypertrophy by combined application of magnesium-aspartate-procaine and hypothermia of 25 degrees C. We conclude that normothermic injection cardioplegia has no protective effect on the hypertrophied left ventricle, whereas additional hypothermia can improve magnesium-aspartate-procaine cardioplegia significantly.

Adenosine Triphosphate↗
PubMed1978

[Monitoring myocardial performance after open heart surgery by calculation of diastolic and systolic pressure time index (author's transl)].

In order to determine the incidence of subendocardial ischemia after open heart surgery, subendocardial blood flow was monitored in 171 patients subjected to mitral and/or aortic valve replacement or coronary revascularization by on-line calculation of Diastolic (DPTI) and Systolic Pressure Time Index (TTI). Body hypothermia with an esophageal temperature of 25 degrees C and magnesium-aspartate-procaine cardioplegia were applied for myocardial protection. Ten patients developed low cardiac output state with two early deaths. In the two patients with fatal low cardiac output DPTI/TTI remained below 0.8. In the remaining 8 patients DPTI/TTI rose to 1.4 after a mean recovery time of 36 hours. In 161 patients (94%) no low cardiac output state evolved and DPTI/TTI rose to 1.3 within 60 min. after termination of cardiopulmonary bypass. Our results indicate that body hypothermia of 25 degrees C combined with magnesium-aspartate-procaine cardioplegia can reduce the incidence of subendocardial ischemia, but does not prevent this complication completely after anoxic times beyond 60-70 minutes.

Blood Pressure↗
PubMed1978

[Behaviour of ATP and lactate in human papillary muscle during profound hypothermia and injection cardioplegia with magnesium-asparatate-procaine (author's transl)].

In 53 patients with mitral- or aortic-mitral valve disease, the content of ATP and lactate of the papillary muscles resected at the time of valve replacement was investigated at the beginning of ischemic arrest and at the time of reperfusion. Profound body hypothermia (25 degrees C) and injection cardioplegia using magnesium-aspartate-procaine were applied for myocardial protection. In hypertrophic papillary muscles the myocardial ATP content decreased at a slower rate (ATP decay 12% of the initial value after 60 minutes of ischemia) than in normal papillary muscles obtained from patients with isolated mitral stenosis (ATP decay 33% of the initial value after 40 minutes of ischemia). 20% of the patients required temporary inotropic circulatory support postoperatively for 12 to 88 hours. The ATP content of the papillary muscles of these patients differed only little from those, in who no myocardial failure occurred. However the myocardial lactate levels were higher in patients in whom a low cardiac output state evolved.

Adenosine Triphosphate↗
PubMed1977

[Combined application of magnesium-aspartate-cardioplegia and general hypothermia in aortic valve replacement (author's transl)].

The surgical results of two similar groups of patients are compared in whom aortic valve replacement was performed utilizing magnesium-aspartate-cardioplegia combined with mild (group A = 71 patients) and profound (group B = 69 patients) hypothermia, respectively. Mortality was 5.6% in group A and 4.3% in group B. Two deaths in group A were due to a severe low cardiac output syndrome, three patients required continuous inotropic circulatory support during the early postoperative course. There was no low cardiac output in group B, no patient required inotropic support. Profound body cooling (esophageal temperature 25 degrees C) and hypothermic injection cardioplegia with magnesium-aspartate provide efficient myocardial protection up to 60 minutes of anoxia.

Aortic Valve↗