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Biomedical subjects

F Schwarz

Publications and source records attributed to F Schwarz.

At least 181 records · Page 10Linked to original sources
PubMed1979

Determinants of restricted aorta-coronary bypass graft flow.

Several causes of restricted graft flow in a series of 99 patients could be identified by intraoperative measurements of aorta-coronary graft flow and poststenotic pressure. Mechanical stenosis as well as functional restriction of graft flow caused by competition between vein and native artery flow were noted in cases with a mildly stenotic artery or in cases with multiple coronary stenoses grafted to the same vessel. Also, analysis of regional wall motion showed that graft flow may be restricted when supplying areas with reduced wall motion. Knowledge of preoperative coronary anatomy and left ventricular function and careful intraoperative measurement of graft haemodynamics may aid in distinguishing between technical, functional, and myocardial factors of low graft flow.

Constriction, Pathologic↗
PubMed1979

Failure of aneurysmectomy to improve left ventricular function.

Biplane left ventricular angiography was performed in 22 patients with isolated obstructive disease of the anterior descending branch of the left coronary artery and with an anterior aneurysm following transmural myocardial infarction. Six patients were restudied between 6 and 10 months after aneurysmectomy. Left ventricular reserve was estimated by analysis of a spontaneous postextrasystolic beat. Using angiographic techniques a contractile section, a transitional section, and a noncontractile section were identified. From the surgical patients the excised aneurysm and a transmural needle biopsy of the transitional section were investigated by light microscopy. With increasing volumes of noncontractile and transitional sections, total end-diastolic volume (r = 0.81, P less than 0.001) and end-systolic volume (r = 0.94, P less than 0.001) increased linearly, while the ejection fraction decreased (r = 0.70, P less than 0.001). No relation was found between the combined volumes of the noncontractile and transitional sections on the one hand, and the end-diastolic volume, the end-systolic volume, or the ejection fraction of the contractile section on the other hand. After aneurysmectomy a significant decrease was found in end-diastolic volume (194 to 133 ml/m2, P less than 0.001) and end-systolic volume (124 to 83 ml/m2, P less than 0.001) but no change occurred in ejection fraction (35 to 37%) and left ventricular end-diastolic pressure (23 to 25 mmHg). Surgical resection included part of the transitional section, which before surgery had an average ejection fraction of 27 per cent during a normal beat, rising to 41 per cent in a postextrasystolic beat. The transitional section after surgery now formed a large akinetic area of the anterior wall. We conclude that aneurysmectomy in isolated left anterior descending artery disease with anterior aneurysm fails to improve left ventricular function because the effect of reduction of left ventricular volumes is offset by the destruction of contractile behaviour in the transitional section.

Adult↗
PubMed1979

Impaired left ventricular function in chronic aortic valve disease: survival and function after replacement by Björk-Shiley prosthesis.

Postoperative survival and left ventricular function were studied in 128 patients who underwent isolated aortic valve replacement by the Björk-Shiley valve between 1973 and 1977. The average follow-up was 2.1 years. Patients with associated coronary artery disease or mitral valve disease were excluded. Preoperative ejection fraction ranged from 15-84%. Forty-two patients were restudied by cardiac catheterization 9.1 +/- 1.1 months (mean +/- SEM) after valve replacement. The hospital mortality was 11%. Preoperative type of valve lesion, functional class, cardiothoracic ratio, and ejection fraction (EF) had no significant effect on postoperative survival up to 4 years. After operation, left ventricular mass (LVMI) and peak systolic wall stress (PSWS) fell significantly, while EF and mean normalized systolic ejection rate (MNSER) increased in aortic stenosis and in aortic insufficiency. Neither in aortic stenosis nor in aortic insufficiency was there a significant relation between preoperative ejection fraction and postoperative LVMI, EF, MNSER and PSWS. We attributed this to a marked improvement of left ventricular function in patients with preoperative impaired ventricular function. Six patients with paravalvular leak to restudy has a significantly lower EF and MNSER, and a higher PSWS than patients without leak. Patients without leak had normal EF, MNSER and PSWS when compared with 10 normal persons, but LVMI remained moderately elevated. Postoperative transprosthetic gradient was 11.9 mm Hg (range 0-64 mm Hg). We conclude that impaired cardiac function is completely restored after aortic valve replacement by Björk-Shiley valve, if valve function is good. Patients with impaired cardiac function preoperatively did not have a poorer prognosis after operation than patients with normal function.

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

[Abolition of pacing induced akinesia after aorto-coronary bypass grafting in patients with stable angina (author's transl)].

Hemodynamic studies were performed in 6 normal individuals, 8 patients with severe obstruction (more than 85% stenosis) of the left anterior descending coronary artery (LAD), 10 patients with patent LAD grafts and 4 patients with stenosed or occluded LAD grafts. All patients were suffering from stable angina before operation. Monoplane ventriculograms and left ventricular pressure determinations were carried out at rest and immediately after ventricular pacing (170/min.). Anterior wall motion was determined from half-diameter shortening and ejection fraction was calculated using the area-length method. Heart rate and left ventricular systolic pressure were comparable in all 4 groups at rest and after pacing. Normal individuals and patients with patent grafts to the LAD showed no significant change of anterior wall motion, ejection fraction and left ventricular enddiastolic pressure after pacing as compared to rest. Patients with LAD stenosis showed a significant decrease of anterior wall motion, of ejection fraction and an increase of left ventricular end-diastolic pressure. Patients with graft failure revealed a drastic though not significant decrease of anterior wall motion. Decrease of ejection fraction and increase of left ventricular end-diastolic pressure were significant. Thus, in patients with stable angina and severe coronary stenosis regional and total left ventricular function may well be maintained at rest but become severely impaired after pacing. Successful revascularization abolishes this ischemic response.

Angina Pectoris↗
PubMed1978

Recovery from myocardial failure after aortic valve replacement.

Left ventricular hypertrophy and function were studied in 27 consecutive patients with chronic aortic valve disease before and 6.4 +/- 2.2 (S.D.) months after aortic valve replacement with Björk-Shiley prostheses. Four patients were excluded because of postoperative paravalvular regurgitation. Five patients had aortic stenosis (AS), seven patients AS plus insufficiency (AS-AI), and 11 patients aortic insufficiency (AI). Left ventricular muscle mass (LVMI), ejection fraction (EF), mean circumferential fiber shortening rate (VCF), mean normalized systolic ejection rate (MNSER), and peak systolic wall stress (PSWS) were determined angiographically. LVMI fell significantly after corrective surgery, whereas EF, VCF, and MNSER increased. PSWS decreased after the operation. Comparison of stress ventriculograms before and after surgery in six patients with predominant AS (isoproterenol infusion, 0.3 microgram per kilogram of body weight per minute) showed an increase of EF, VCF, and MNSER and a decrease of PSWS. We conclude that hypertrophy in chronic aortic valve disease regresses after aortic valve replacement, and thereby depressed cardiac function and reserve recover.

Adult↗