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T J Spyt

Publications and source records attributed to T J Spyt.

52 records · Page 3Linked to original sources
PubMed1992

Contraction and relaxation of human internal mammary artery after intraluminal administration of papaverine.

The internal mammary artery has become the conduit of choice for coronary artery bypass grafting. Intraluminal papaverine treatment during operation reduces vasospasm and facilitates anastomosis. However, it has been suggested that papaverine may cause intimal damage, and accordingly we have investigated endothelial damage by comparing the responsiveness of internal mammary arteries before and after intraluminal exposure to papaverine (15 mg/mL). Control and papaverine-treated segments of internal mammary artery were obtained from 13 patients undergoing coronary artery bypass grafting and mounted as ring preparations in an organ bath. Cumulative dose contractions to noradrenaline were performed, and the dose producing a half maximal response was determined. Relaxation studies of submaximally contracted arteries were performed using the endothelium-dependent vasodilators acetylcholine and bradykinin and the endothelium-independent vasodilator sodium nitroprusside. In the human internal mammary artery the use of intraluminal papaverine increased the lumen size by 20% (p less than 0.05), and the contractions elicited by noradrenaline were significantly less in the papaverine group than in the control group (p less than 0.05). Endothelium-dependent relaxation to acetylcholine or bradykinin was not affected by papaverine treatment. Endothelium-independent relaxation was the same in both groups, with almost 100% relaxation achieved by sodium nitroprusside. These results indicate that intraluminal papaverine treatment during coronary artery bypass grafting causes a reduction of smooth muscle contraction and does not impair endothelium-dependent relaxation.

Acetylcholine↗
PubMed1992

Carbomedics and St. Jude Medical bileaflet valves: an in vitro and in vivo comparison.

The hydrodynamic and haemodynamic function of 29 mm mitral and 23 mm aortic St Jude Medical (SJM) and CarboMedics (CM) heart valves have been compared in a pulsatile flow simulator in the laboratory and by doppler ultrasound in vivo. The laboratory studies showed that there was no significant difference in the pressure drop across the valves. The valves also had similar regurgitant volumes. Doppler ultrasound confirmed these results with a mean pressure drop of 12.9 +/- 5.5 mmHg across the CM aortic valves and 12.6 +/- 5.5 mmHg for the SJM aortic valves. The mean mitral diastolic pressure drops were 3.8 +/- 1.8 and 4.6 +/- 1.4 mmHg for the CM and SJM valves, respectively. Mild aortic regurgitation was detected in 5 of 14 patients in the CM group and 1 out of 6 patients in the SJM group, though none of the cases were clinically significant. Both the in vitro and in vivo results show these valves to have acceptable and comparable function.

Aortic Valve↗
PubMed1991

Comparative study of the hydrodynamic function of the CarboMedics valve.

The hydrodynamic function of each size of the CarboMedics valve was assessed in a pulsatile flow simulator. The mean pressure difference with respect to forward flow, regurgitant volumes, and total energy loss across each valve were analyzed. The results for the 23-mm aortic and 29-mm mitral CarboMedics valves were compared with those for the St. Jude Medical and Björk-Shiley Monostrut valves. Results showed good hydrodynamic function for each CarboMedics valve, although the pressure difference and total energy loss across the 19-mm aortic valve was high. The hydrodynamic function of the CarboMedics valve was comparable with that of the St. Jude Medical valve. Both valves showed similar leakage volumes, which were significantly larger than that for the Björk-Shiley Monostrut valve. On account of this the total energy loss in the Björk-Shiley valve was significantly less than that for the bileaflet valves in the aortic position. Concern remains for the continuing presence of high closed-valve regurgitation in the bileaflet valves.

Aortic Valve↗
PubMed1990

Protective influence of pretreatment with allopurinol on myocardial function in patients undergoing coronary artery surgery.

Xanthine oxidase is responsible for the release of free oxygen radicals during myocardial reperfusion. Allopurinol was shown to be an effective inhibitor of this reaction in the laboratory experiments, but not in patients. Thirteen male patients undergoing routine coronary artery bypass graft surgery were treated with allopurinol in doses of 15 mg/kg per day for 4 days before the operation. Haemodynamic function in the early period after cardiopulmonary bypass, ECG, enzyme release and ultrastructural findings in this group were compared with those in a control group of 13 male patients matched for age distribution and stage of coronary disease. Left ventricular stroke work index was higher in the treatment group 10 min (P less than 0.001) and 15 min after termination of cardiopulmonary bypass (P less than 0.01) and also 2 h later (P less than 0.02). In the early post-operative recovery phase fewer episodes of arrhythmia were observed in this group of patients (P less than 0.001). Electron microscopy studies of the myocardium and CK and CK-MB release showed no significant differences between groups. Thus, allopurinol may have a protective effect on the human ischaemic myocardium in the early period of reperfusion.

Allopurinol↗
PubMed1990

Clinical evaluation of the Björk-Shiley disc valve in the tricuspid position. Long-term results.

Between 1971 and 1981, 1210 Björk-Shiley prostheses were implanted. Of these, 79 were in the tricuspid position, comprising 30 triple valve replacements, 46 mitral plus tricuspid, and 3 isolated tricuspid replacements. The ages ranged from 10-55 years (mean 45 years). Sixty-three patients (80%) were in NYHA grades III or IV preoperatively. Thirteen patients died in hospital after surgery (16.5%). The 66 survivors have been followed for up to 16 years (mean 7.5 years). There have been 37 late deaths (7.5 per patient year). Twelve were valve-related: 4 tricuspid complications, 4 mitral complications, 2 prosthetic endocarditis, 1 aortic leak and 1 anticoagulant-related bleed. Twenty-one late deaths were not valve-related, and 4 causes of death are unknown. Expressed actuarially, survival at 5 years was 68%, and at 10 years, 49.4% +/- 12%. Freedom from valve-related death at 10 years was 80.7% +/- 7%. At last follow-up, 90% of the survivors were in NYHA class 1 or 2 with only modest signs of venous hypertension. The commonest life-threatening complication was obstruction of the tricuspid prosthesis by tissue ingrowth. This occurred in 7 patients (1.4% per patient year) 4 were re-operated upon and survived, 3 died. Doppler echocardiography has been carried out on 27 survivors of whom 5 had abnormal pressure-half times but only 3 of these were symptomatic. This series shows that function of the standard disc Björk-Shiley prosthesis in the tricuspid position compares favourably with other prostheses. The problem of tissue ingrowth can be diagnosed by echo Doppler and reoperation successfully carried out.

Adolescent↗
PubMed1989

Failure and hydrodynamic function testing of explanted pericardial and porcine bioprosthetic valves.

The long-term durability and function of cardiac bioprostheses can be affected by both calcification and mechanical failure of the tissue. The mechanisms of failure and hydrodynamic function of 66 explanted bioprostheses have been studied. The majority of porcine valves were heavily calcified with leaflet tears adjacent to the calcification at the commissures. These tears caused prolapsed leaflets and regurgitation of between 30 and 70 per cent. Only three porcine valves had tissue failure in the absence of calcification. The majority of pericardial valves failed due to leaflet tears at the edge of the frame in the absence of macroscopic calcification. These tears also produced prolapsed leaflets and large regurgitation in hydrodynamic tests. Three pericardial valves were heavily calcified and stenotic without leaflet tears. Leaflet dynamics in the pericardial valves were affected by host tissue ingrowth which produced increased pressure drops across the valves, an asymmetrical open position and leaflet flutter. In the absence of calcification and leaflet tears, there was little change in the function of explanted porcine valves.

Bioprosthesis↗
PubMed1988

Severe haemolysis with the St. Jude Medical prosthesis.

The St. Jude Medical prosthesis has become one of the most widely used mechanical heart valves because of its excellent haemodynamic function. Although subclinical haemolysis has been described with this prosthesis, there has only been a single report of frank haemolysis in the absence of a paravalvular leak. We report the occurrence of severe haemolysis in five patients following St Jude Medical prosthesis implantation, four of whom had combined aortic and mitral valve replacements. In no patient could the haemolysis be attributed either to a paravalvular leak or an obvious valve malfunction.

Aged↗
PubMed1988

Assessment of coronary artery bypass graft flow by intraoperative Doppler ultrasound technique.

A high frequency (10 MHz) Doppler ultrasound pencil probe was used to estimate flow in coronary artery bypass grafts in vitro and during cardiac surgery. In vitro, increasing the angle of the Doppler transducer in relation to flow caused underestimation of the Doppler derived flow, and using the external rather than internal vessel diameter to calculate cross sectional area caused significant overestimation. This overestimation was considerably greater for the internal mammary artery. Accurate flow estimation was obtained in vitro by the Doppler technique, but considerable variation occurred in patients studied during coronary artery bypass surgery. In conclusion, intraoperative Doppler ultrasound provides a qualitative assessment of phasic flow in coronary artery bypass grafts but is less accurate in quantifying absolute flow in these patients.

Adult↗
PubMed1988

Animal evaluation of a new pericardial bioprosthetic heart valve.

Implantation in animals is an essential step in the evaluation of any new prosthetic heart valve before commencing clinical trials. A new three-leaflet pericardial bioprosthesis developed in Glasgow has been implanted in the mitral position in ten sheep and eight dogs. Eleven animals were electively killed after 3 months of observation and explanted valves were in good condition. Hydrodynamic tests of the explanted valves showed small changes in function compared to tests prior to implantation. This was mainly due to host tissue ingrowth over the edge of the leaflets. Histological studies confirmed good preservation of the pericardial tissue in explanted valves.

Animals↗
PubMedDate not supplied

Does simultaneous antegrade and retrograde cardioplegia improve functional recovery and myocardial homeostasis?

BACKGROUND: The purpose of our research was to evaluate the functional recovery and homeostasis of myocardium during simultaneous continuous retrograde and antegrade cardioplegia versus continuous retrograde cardioplegia. METHODS: Forty patients who underwent elective coronary artery bypass grafting (CABG) were prospectively assigned to two clinically matched groups and analyzed in respect to cardioplegia protocol. Group I consisted of 24 patients who received continuous retrograde blood cardioplegia; Group II consisted of 16 patients who received simultaneous continuous ante- and retrograde cardioplegia. Hydrogen ion release, carbon dioxide, lactate concentration oxygen content, and oxygen extraction were measured from coronary sinus effluent and from the arterial line before and after cross-clamping of the aorta. Median changes of these parameters were reported. Cardiac output was measured and left and right ventricle stroke works were calculated. Incidence of low cardiac output, ventricular fibrillation, raised cardiac enzymes, and ischemic changes on electrocardiogram (ECG) were noted. RESULTS: In the simultaneous group, oxygen content and oxygen extraction recovered well after cross-clamping. The same parameters did not recover to the same extent in the retrograde group. These changes were notable between groups. Hydrogen ion, carbon dioxide, and lactate releases were comparable between groups. Trend toward better recovery of left ventricle stroke work index was encountered in the simultaneous group. CONCLUSIONS: Viability of myocardium measured with oxygen utilization and functional recovery is better preserved with simultaneous antegrade and retrograde cardioplegia. However, there is no difference in anaerobic metabolism markers. Thus simultaneous ante- and retrograde cardioplegia is probably advantageous over retrograde alone.

Adult↗