Search PubMed⌕ Search

Biomedical subjects

John Pepper

Publications and source records attributed to John Pepper.

27 records · Page 2Linked to original sources
PubMed2004

Chronic stable ischaemia protects against myocyte damage during beating heart coronary surgery.

OBJECTIVES: Many patients with coronary artery disease demonstrate chronic resting ischaemic myocardial dysfunction. We have investigated whether this ischaemia influences the myocardial damage caused by the period of coronary occlusion involved in beating heart surgery. METHODS: Thirty-three patients with chronic stable angina and normal left ventricular ejection fraction were studied. To make our model clinically appropriate, we included patients with a wide range of ischaemic times, ages and in a subset of 10 patients a surgical preconditioning protocol. Myocyte injury was assessed from venous Troponin T release measured on days 1, 2, and 3. We used intraoperative transoesophageal M mode echocardiograms and simultaneous high-fidelity left ventricular pressure to assess whether patients were demonstrating the functional effects of ischaemia (asynchronous regional contraction with reduced mechanical function). RESULTS: Patients demonstrated the functional effects of resting ischaemia and 17 did not. Patients with resting ischaemia had lower preoperative values of regional peak power and work and all three variables increased significantly with surgery. Venous Troponin T levels at 48 and 72 h postoperatively were lower in those with preoperative resting ischaemia (median (interquartile range) 0.13 (0.08-0.20) vs 0.21 (0.13-0.69) for 48 h and 0.10 (0.08-0.19) vs 0.26 (0.12-0.51) for 72 h). Stepwise multiple linear regression of total postoperative troponin release (measured as the area under the curve of troponin release) demonstrated two independent determinants (R squared for model 0.40): longer ischaemic time, and increasing values of cycle efficiency. The surgical ischaemic preconditioning protocol and preoperative collaterals were not independent determinants. CONCLUSIONS: In patients with chronic coronary artery disease, stable preoperative ischaemia may thus represent a naturally occurring form of myocardial protection, whose presence reduces Troponin T release after beating heart surgery. This protection is different in nature from classical ischaemic preconditioning.

Aged↗
PubMed2004

Feasibility and cost of treatment with drug eluting stents of surgical candidates with multi-vessel coronary disease.

OBJECTIVE: To determine the feasibility and cost of treatment with drug eluting stents in patients with multi-vessel coronary disease referred currently for surgical revascularisation. METHODS: Two experienced interventional cardiologists reviewed retrospectively the clinical records and pre-operative coronary angiograms of 209 patients who underwent their first coronary bypass operation for multi-vessel disease without other adjunctive surgical procedures at the Royal Brompton Hospital in 2002. They were classified according to the technical feasibility and completeness of percutaneous revascularisation. A cost decision-analysis model with a cost of drug eluting stents of euro 2,100 and simulated 1-year costs was constructed. RESULTS: Mean age was 64.6+/-8.9 years with 54 diabetics (25.8%). Each patient received at least 1 arterial graft and a mean of 3.0+/-0.8 distal anastomoses. Mean post-operative stay was 8.9+/-7.2 days and total cost euro 19,821+/-1,964. Percutaneous revascularisation was judged to be feasible in 158 (76%) cases. The contraindications were at least 1 unfavourable total occlusion subtending viable myocardium in 48 patients (23%) and extreme tortuosity or calcification in 4 patients (2%). Percutaneous revascularisation of grafted major epicardial vessels was anticipated to be complete in 138 (66%) patients and partial but acceptable in 19 (9.1%) patients. Stenting of the left main, of a 'favourable' total occlusion, of bifurcations or in an ostial location would have been required in 32 (20.4%), 60 (38.2%), 77 (49.0%) and 74 (47.1%), respectively, of cases treated. 3.6+/-1.4 drug eluting stents of total length 72.6+/-37.3 mm were required to treat 3.3+/-1.2 lesions per patient at an estimated cost of euro 17,266+/-2,850. When one year repeat revascularisation was modelled at a rate of 15% in the stent group there was no significant cost saving from stenting. CONCLUSIONS: Although percutaneous revascularisation is feasible in 76% of patients currently undergoing coronary artery bypass grafting for multi-vessel disease, such an approach will involve frequent treatment of complex lesions for which no long term results are available and is unlikely to provide appreciable economic savings.

Aged↗
PubMed2004

Electromechanical left ventricular resynchronisation by coronary artery bypass surgery.

OBJECTIVE: In patients with coronary artery disease (CAD), the normal electromechanical response to dobutamine stress is deranged: QRS duration lengthens rather than shortens, left ventricular asynchrony develops, post-ejection shortening appears, and total isovolumic time (the time in the cardiac cycle when the ventricle is neither ejecting nor filling) increases rather than falls, all of which blunt the normal rise in cardiac output. We aimed to study the effect of revascularisation on these stress-induced electromechanical abnormalities and their effect on peak cardiac output after coronary artery bypass grafting (CABG). METHOD: 20 unselected patients were studied before and after CABG. Long axis asynchrony was determined by (i) delay in the onset of shortening, (ii) amplitude and (iii) duration of post-ejection shortening. Total isovolumic time (in s/min), calculated as [60-(total ejection time+total filling time)] and cardiac output were measured by Doppler echocardiography. RESULTS: Before CABG: QRS duration broadened with stress (by 7+/-8 ms, P<0.01) and post-ejection shortening increased (amplitude by 1.1+/-0.7 mm, P<0.01, duration by 8+/-9 ms, P<0.01). Total isovolumic time increased (by 3+/-3 s/min, P<0.01) and cardiac output rose (by 2.8+/-1.2 l/min, P<0.01). After CABG: QRS duration shortened with stress (by 5+/-4 ms, P<0.01) post-ejection shortening decreased (amplitude and duration fell by 0.4+/-0.5 mm and 22+/-14 ms, respectively), total isovolumic time shortened (by 3+/-3 s/min) and cardiac output increased (by 5.1+/-1.8 l/min, all P<0.01). Changes in total isovolumic time and duration of post-ejection shortening with stress were independent predictors of the increase in peak cardiac output after revascularisation (total R(2)=0.69). Independent predictors of changes in total isovolumic time with stress were those in QRS duration and the duration of post-ejection shortening (total R(2)=0.75). In turn, changes in the duration of post-ejection shortening were closely associated with alterations in the delay in long axis shortening (r(2)=0.50) which correlated with changes in QRS duration (r(2)=0.59, all P<0.001). CONCLUSIONS: Revascularisation resynchronises left ventricular wall motion by restoring the normal activation response to stress, thereby reducing total isovolumic time and normalising peak cardiac output response to stress.

Aged↗
PubMed2004

Improved recovery after the endoscopic atraumatic coronary artery bypass procedure compared with sternotomy for off-pump bypass of the left internal thoracic artery to the left anterior descending coronary artery: a case-matched study.

OBJECTIVE: The endoscopic atraumatic coronary artery bypass (endo-ACAB) procedure allows single-vessel coronary artery bypass grafting (CABG), avoiding sternotomy or thoracotomy. We set out to define the effect of this surgical approach on postoperative recovery, blood loss, and return to work. METHODS: We performed a case-control comparison of our first 29 endo-ACAB procedures for left anterior descending coronary artery (LAD) disease against 29 control patients, who underwent off-pump beating heart CABG via sternotomy for isolated LAD disease in the same institution. Control pairs were matched for age, sex, and ventricular function. RESULTS: In a matched population, endo-ACAB is associated with shorter postoperative ventilation times (6.2 hours versus 9.0 hours, P = .034) and hospital stays (5.3 nights versus 6.4 nights, P = .04), less blood loss (363.9 mL versus 570.3 mL, P = .017), and lower transfusion requirements. Endo-ACAB patients were more likely to return to employment and did so at a mean of 6.6 weeks earlier than sternotomy patients (P = .019). CONCLUSIONS: Endo-ACAB for grafting of the left internal mammary artery to the LAD is associated with reduced blood loss and faster postoperative recovery. Avoiding sternotomy appears to be a significant factor in recovery after beating heart single-vessel CABG surgery.

Anastomosis, Surgical↗
PubMed2003

Porcine or human stentless valves for aortic valve replacement? Results of a 10-year comparative study.

BACKGROUND AND AIM OF THE STUDY: Stentless porcine valves in the aortic position exhibit similar excellent hemodynamic performance to homografts, but have the advantage of availability. Their performance was compared over a 10-year period in a single-surgeon and single-institution series. METHODS: Demographic, operative and mortality data were obtained retrospectively. Survivors were interviewed by telephone according to a defined protocol. Definitions and analyses were in accordance with joint STS/AATS guidelines. RESULTS: A total of 408 stentless porcine and homograft aortic valve replacements (AVR) was performed between 1991 and 2001. Five patients were excluded due to incomplete data, in addition to 82 patients who underwent AVR with a free-standing root replacement technique. Hence, 321 patients (217 males, 104 females; mean age 67 +/- 12 years) had a subcoronary implant. The median time to follow up was 4.9 years (range: 2.9-6.6 years). No differences were noted between homograft and stentless porcine valves in one- and five-year freedom from structural valve deterioration (99.1 versus 97.2% and 95.7 versus 93.1%; p = 0.10), reoperation (99.2 versus 99.4% and 97.8 versus 96.7%; p = 0.45) and endocarditis (98.3 versus 99.4% and 97.4 versus 99.4%; p = 0.14). Overall one- and five-year survival comparing homograft to stentless porcine valve was 90.4 versus 92.3% and 80.8 versus 73.7%, respectively; p = 0.23. Independent predictors of mortality on multivariate analysis were: ventricular function (p < 0.0001), increasing age (p < 0.001), increasing serum creatinine (p < 0.001) and concomitant coronary surgery (p = 0.05). Treated hypercholesterolemia was independently protective against mortality, with an odds ratio of 0.26 (CI 0.10 to 0.66; p = 0.005). CONCLUSION: The porcine stentless valve, when implanted in the subcoronary position, is an excellent alternative to the homograft and shows excellent clinical performance and durability at mid term.

Age Factors↗
PubMed2003

Evidence for rheumatic valve disease in patients with severe tricuspid regurgitation long after mitral valve surgery: the role of 3D echo reconstruction.

BACKGROUND AND AIM OF THE STUDY: Although severe tricuspid regurgitation (TR) is a well-recognized, long-term complication of rheumatic mitral valve replacement that impairs the functional results of surgery, its exact basis remains unclear and its management is unsatisfactory. The study aim was to obtain a detailed assessment of tricuspid valve morphology and function using 2D transesophageal echocardiography (TEE) with 3D reconstruction, and to determine long-term clinical outcome in patients after surgery for rheumatic mitral valve disease. METHODS: A total of 42 patients (mean age 50 +/- 10 years) was followed up; 39 patients had mitral replacement and three had valvotomy. Thirty patients had developed impaired exercise tolerance, fluid retention and echocardiographic evidence of severe TR at 8.2 +/- 2.6 years after surgery; the remainder had mild regurgitation. RESULTS: Follow up showed greater mortality in the severe TR group, with approximately 50% survival at 60 months after diagnosis compared with mild TR. None of the patients with severe TR had a dysfunctional mitral prosthesis. In these patients, transthoracic echo-Doppler showed enlarged right atrium and right ventricle, a mean transtricuspid retrograde pressure drop of 15 +/- 4 mmHg and apparently normal leaflet anatomy. Twenty patients (15 with severe TR) underwent a TEE and 3D reconstruction study for further evaluation. Abnormal leaflet anatomy was demonstrated in all patients with severe TR, with restricted leaflet motion in 10, leaflet shortening and thickening in the remainder, and dilatation of tricuspid valve annular insertion suggestive of rheumatic involvement. Although diastolic transtricuspid velocities were increased (peak flow 0.8 +/- 0.1 m/s) in these patients due to increased stroke volume, significant tricuspid stenosis was present in only two cases (mean gradient 4 and 3 mmHg respectively). Histopathology confirmed the presence of leaflet vascularization and extensive fibrosis in two patients who underwent tricuspid valve replacement. CONCLUSION: Rheumatic leaflet involvement contributes to severe TR occurring long after mitral valve replacement, though overt stenosis is uncommon. Knowledge of the structural basis of this condition may thus improve its long-term management, possibly with early tricuspid valve repair.

Adult↗
PubMed2002

The histology of viable and hibernating myocardium in relation to imaging characteristics.

OBJECTIVES: This study characterizes the histology of myocardium predicted to be hibernating using three different imaging techniques to explain the discordance among them. BACKGROUND: Both radionuclide and functional imaging techniques were used to assess myocardial hibernation. The former have high sensitivity and the latter high specificity for predicting functional recovery. METHODS: Nineteen patients underwent thallium-201 and 99m-technetium tetrofosmin myocardial perfusion imaging, and dobutamine magnetic resonance imaging (MRI), prior to coronary bypass grafting. Criteria for predicted hibernation for each technique were defined before operation. Postoperative criteria for scar and true hibernation were also defined. Biopsies were analyzed for myocyte volume fraction (MVF), glycogen deposition and pathologic cell features. RESULTS: Thallium was most sensitive in predicting hibernation (88%) and MRI most specific (84%); and, although there was good agreement between thallium and tetrofosmin (85%), agreement between MRI and thallium (59%) or tetrofosmin (59%) was poor. For each technique, MVF was higher in segments predicted to be hibernating rather than scar (p < 0.05). The MVF was higher where both thallium and MRI predicted hibernation (0.77+/-0.07) than in segments predicted by thallium alone (0.69+/-0.13, p < 0.05). Proven hibernating segments had a higher MVF than scar (0.72+/-0.11 vs. 0.6+/-0.26, p < 0.05). CONCLUSIONS: Preservation of myocyte fraction is an important determinant of functional recovery after revascularization. A higher myocyte fraction is required to maintain contractile reserve than to achieve significant tracer uptake. This explains the higher sensitivity of radionuclide imaging compared with dobutamine MRI in the identification of myocardial hibernation.

Adult↗