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Biomedical subjects

F W Hehrlein

Publications and source records attributed to F W Hehrlein.

At least 91 records · Page 5Linked to original sources
PubMed1981

Hemodynamic properties of St. Jude medical and Björk-Shiley valvular prostheses in mitral position in the pulse duplicator.

A general lack of standardization of the pre-clinical testing of artificial valves leads to an actual comparison of different prosthetic models at the time of a first clinical trial, frequently with contradictory results. Therefore, a pulse duplicator was developed in order to compare different valves of comparable size under identical standardized conditions in aortic and mitral positions. Comparison of Björk-Shiley and St. Jude medical prostheses in the duplicator revealed a linear relationship between pump setting and stroke volume delivered (r less than or equal to 0.9) for both valves. Pressure loss across the mitral valves showed a linear relationship to stroke volume (less than or equal to 0.9) and frequency (less than or equal to 0.9). The gradient, expressed per milliliter stroke volume, for identical frequencies appeared as the simplest and most suitable parameter for comparison of the hydraulic function of different valves. Using this parameter, the valves showed individual differences over a wide physiological range of testing. The differences, however, are of a magnitude that can hardly be detected under clinical testing conditions.

Aortic Valve↗
PubMed1981

Comparative long-term results of patients with carotid artery stenosis.

Of 78 patients with an internal carotid artery stenosis a thrombendarterectomy was performed in 46 patients whereas 32 patients were treated by conservative methods. The clinical follow-up over a period of 10 years was investigated. The percentage of patients who received drugs for anticoagulation was equal in both groups. Operated patients acquired a permanent neurologic deficit in 3% and nonoperated patients in 69%. The physical capacity improved in 92% of the operated and in 64% of patients treated conservatively. At the time of reexamination 78% of the operated and 34% of the nonoperated patients were living. The cause of death was cardiac in 42% of both groups and cerebral in 11% of the operated and in 32% of the nonoperated patients.

Actuarial Analysis↗
PubMed1980

Continuous peritoneal dialysis (CPD)--an alternative to hemodialysis in acute renal failure after cardiovascular operations.

In our experience hemodialysis proved to be unsatisfactory in the treatment of acute renal failure after cardiovascular surgical intervention because of its negative influence on the often critical hemodynamic situation of the patients. In 21 cases we performed a continuous peritoneal dialysis (CPD) for 1 to 29 (mean 9.2) days by using a Tenckhoff catheter (16). Treatment was started when anuria occurred or when serum nonprotein nitrogen increased. Satisfactory volume equilibration was established by this treatment. A pathological increase of serum electrolytes could be prevented; serum potassium, in particular, did not exceed 5.6 mVal/l. No dysfunctions in acid-base balance occurred. The serum levels of nonprotein nitrogen decreased: Serum carbamid was diminished from 229 +/- 14 mg% to 160 +/- 10 mg% and serum creatinine from 7.7 +/- 0.6 mg% to 6.0 +/- 0.8 mg% (p < 0.05). Disturbances of hemodynamic and respiratory functions could be avoided by CPD. Peritoneal reactions were noted in 5 cases. In our opinion continuous peritoneal dialysis seems to be a suitable alternative to hemodialysis in the treatment of acute renal failure after open heart surgery.

Acute Kidney Injury↗
PubMed1980

Ultrastructural evaluation of the effects of global ischemia and reperfusion on human myocardium.

During open-heart surgery, myocardial biopsies were taken from 31 patients undergoing aortic valve replacement on total cardiopulmonary bypass. The first needle biopsy was taken before the induction of cardiac arrest (Kirsch cardioplegia), the second at the end of global ischemia, and the third during the reperfusion period. The tissue was investigated by electron microscopy using a semiquantitative scoring system for changes in both myocytes and blood vessels. Mitochondrial volume and surface density were determined by morphometry. Reversible ischemic injury of moderate to severe degree occurred in cardiac cells and in small blood vessels. On reperfusion, signs of damage regressed earlier in myocardial than in vascular tissue. Morphometry revealed significant mitochondrial swelling during the reperfusion phase, but this was not present after ischemia alone. It is concluded that Kirsch cardioplegia as applied here, is unable to protect the heart from ischemic cellular damage.

Biopsy↗
PubMed1979

[Replacement of mitral and aortic valve of a 12 years old boy (author's transl)].

Report of the case of a 12 years old boy, who because of acquired mitral valve insufficiency (grades II--III), after an illness of virus-carditis, became, in the first instance, a Bjoerk-Shiley-Ventil M27 prosthetic valvular replacement, and after 3 months, in one sitting, correction of a paravalvular leakage and prosthetic valvular replacement of the insufficient aortic valve with a Bjoerk-Shiley A23. The boy was well rehabilitated one year after the last operation. This is supported by the similar results of the echocardiographic, the ergometric and the pulmonary function tests carried out. The size of the replaced prosthetic valve makes the long time prognosis favourable. Double-valvular prosthetic replacement in children was hitherto carried out predominantly as a result of rheumatic diseases. The rheumatic process as well as congenital valvular malformation could surely be excluded in our patient so that the virus-process seems to be the most likely cause of the valvular defect.

Aortic Valve↗
PubMed1979

Recovery of the heart after normothermic ischemia. Part I: Ultrastructural findings during postischemic reperfusion.

The influence of controlled ischemia on myocardial ultrastructure was investigated in isolated, metabolically supported canine hearts. Recovery of functionally normal tissue as indicated by the reversibility of morphological alterations was observed up to 60 minutes of anoxia. It was shown that prolonged reperfusion of the empty beating heart supports the recovery of normal cellular ultrastructure. Severe ischemic damage of mitochondria due to ischemia of 60 minutes was almost completely reversible after a reperfusion period of 50 minutes.

Animals↗
PubMed1979

Recovery of the heart after normothermic ischemia. Part II: Myocardial function during postischemic reperfusion.

Contraction and relaxation of the canine myocardium were examined during normothermic ischemia in an isolated heart model. Decrease in the development of tension depends on the duration of ischemia. Deficient functional recovery was observed after ischemic periods extending beyond 30 minutes, in spite of reperfusion periods of over 1 hour. A decrease in compliance was observed during the anoxic period, but a persistent defect of relaxation occurred only after 60 minutes of ischemia. After this period there was also a disturbance in the autoregulative mechanisms of coronary perfusion and an uncoupling of O2-consumption and mechanical efficiency. A prolonged reperfusion period of the heart beating empty allowed ultrastructural recovery of the damaged myocardium. In contrast, functional recovery of the myocardium, as determined by several parameters of contraction and relaxation, did not correlate with ultrastructural recovery and was not improved by prolonged reperfusion.

Animals↗
PubMed1979

Heart valve replacement with the St. Jude medical prosthesis -- first clinical results --.

Starting in February 1978 52 St. Jude Medical Prostheses have been implanted in 47 patients (age 13--73 years) in aortic, mitral and tricuspid positions. Perioperative death occurred in 3 cases. Post mortem examination of these patients showed unimpaired valvular function. There were no other complications in an accumulated total valve time of approximately 300 months. Prior to surgery and post-operatively, several hemolytic parameters were analyzed. There was only a mild elevation in Serum LDH (285 +/- 10 iV/L). Fifteen patients underwent recatheterization 3 months postoperatively. The mitral valves did not reveal an enddiastolic gradient at rest, while the aortic valves had a peak to peak gradient of 8 +/- 2.1 mmHg. A standardized stress consisting of an infusion of isoproterenol was used. The results were compared to results obtained in patients with Björk-Shiley prostheses under identical conditions and did not show a significant difference. The preliminary hemodynamic findings correlate with preceding in vitro results and preclinical data, and the first clinical experience is promising.

Adolescent↗
PubMed1978

Intraoperative evaluation of the functional significance of coronary collateral vessels in patients with coronary artery disease.

Coronary hemodynamics were studied intraoperatively in 65 patients undergoing aortocoronary bypass grafting. Poststenotic coronary pressure and graft flow hyperemia were measured. Patients without coronary collateral vessels on arteriography (class A) were compared with patients with collateral vessels (class B). Patients in class A were grouped according to the angiographically determined degree of coronary stenosis. Eight of these patients with moderate coronary stenosis underwent intraoperative studies with transient complete coronary occlusion and were classified in the "acute" occlusion group. In class B all patients had complete coronary occlusion with good retrograde filling of the distal segment. In class A patients there was good correlation between the degree of stenosis and poststenotic pressure or hyperemic response. Stenosis had to be at least 80 percent before it produced a significant pressure gradient or graft flow hyperemia. In class B patients (those with complete "chronic" coronary occlusion), poststenotic pressure was significantly greater than in the class A patients with "acute" occlusion, significantly less than in the class A groups with 71 to 80 percent and 81 to 90% stenosis but not significantly different from values in the class A group with 91 to 99 percent stenosis. The hyperemic response was significantly less than in the "acute" occlusion group of class A, significantly greater than in the class A groups with 71 to 80 percent and 81 to 90 percent stenosis, but not significantly different from values in the class A group with 91 to 99 percent stenosis. It is concluded that (1) under basal conditions a coronary stenosis must be at least 80 percent to be hemodynamically significant, and (2) well developed collateral vessels produce in a completely occluded coronary artery hemodynamic changes that simulate those of a 90 percent coronary stenosis without collateral vessels.

Collateral Circulation↗
PubMed1978

[The influence of postischemic reperfusion on the recovery of ischemic lesions of the left ventricle (author's transl)].

In an isolated dog heart preparation the influence of normothermic ischemic arrest and recovery of the ventricular function during the period of post-ischemic reperfusion were investigated. If ischemic arrest has caused a depression of ventricular function, the functional recovery of the myocardium cannot be improved significantly by a prolonged reperfusion of the empty beating heart.

Animals↗
PubMed1977

[Intraoperative measurements of prognostic value in coronary bypass surgery (author's transl)].

The effect of an aortocoronary bypass graft on coronary hemodynamics was studied experimentally in dogs and during surgery for aortocoronary bypass grafting in man. In the experimental part of this study it was shown that coronary dilatory reserve is unaffected between 0 and 50% coronary narrowing. In the presence of more severe stenosis the dilatory reserve declines rapidly. Competition of flow between an aortocoronary bypass graft and the stenotic segment is related to the degree of coronary stenosis. In 53 patients graft flow was measured during surgery. The relation between hyperemic response (hyperemic/control flow = HR) after short occlusion of the graft and the poststenotic coronary pressure (poststenotic pressure/aortic pressure times 100 = PSPR) could be described by the function HR = a. exp b PSPR (r = 0,87). When the degree of coronary stenosis exceeded 80% narrowing, poststenotic pressure decreased rapidly and hyperemic response appeared. In patients with comparable LAD stenosis a close correlation was found between basal graft flow and anterior wall motion (r = 0,91). It is concluded that graft function can be evaluated by the relation between HR, PSPR and the degree of coronary stenosis. Left ventricular wall motion is shown to be an additional determinant of graft flow.

Animals↗