Mitral valve repair for ischemic mitral regurgitation in dilated cardiomyopathy

Ischemic mitral regurgitation contributes to poor survival in patients with heart failure. The intermediate-term outcome of mitral reconstruction in 15 patients who had ischemic dilated cardiomyopathy with mitral regurgitation requiring surgical intervention was studied. They underwent mitral valve repair along with coronary artery bypass surgery. The mitral valve coaptation depth was considered an important parameter in deciding on repair. Ages ranged from 43 to 72 years. Left ventricular ejection fractions were 15-38% (mean, 26.5% +/- 4.3%). The operative technique in all 15 patients was posterior annuloplasty using Dacron felt. At a mean follow-up of 4.6 +/- 1.2 months (1-8 months), postoperative transesophageal echocardiography revealed mild mitral regurgitation in 2 patients and none in 13. There was a significant improvement in New York Heart Association functional class from 3.9 +/- 1.1 to 1.9 +/- 0.3. Mitral valve repair by posterior felt annuloplasty provides favorable results in the intermediate-term in selected patients with ischemic cardiomyopathy and severe left ventricular dysfunction.

Post-operative outcome of ventricular reshaping by septal exclusion in patients with severe left ventricular dysfunction

BACKGROUND

Post-myocardial infarction, anteroseptal dysfunction or akinesia is treated by septal reshaping to improve the surgical outcome in patients with severe left ventricular dysfunction.

METHODS AND RESULTS

Between February 2003 to December 2003, 30 consecutive patients with previous anterior wall myocardial infarction and severe ventricular dysfunction underwent septal reshaping. All the dyskinetic and akinetic septal areas were excluded using an oval dacron patch which was sutured from the healthy septal area to the anterior wall, resulting in formation of a new apex. There were two mortalities in the group. After a mean follow-up of 4.2 +/- 1.6 months (1-7 months) it was seen that this procedure resulted in significant reduction of ventricular volume, increase in ejection fraction, an improvement in New York Heart Association class from 2.9 +/- 1.1 to 1.7 +/- 0.3, and a better apical geometry.

CONCLUSIONS

In selected patients with left anterior descending artery occlusion resulting in anteroseptal dyskinesia or akinesia, septal exclusion technique provides good clinical and morphological results with significant improvement in left ventricular function.

Concomitant Carotid Endarterectomy and Coronary Bypass Surgery: Outcome of On-Pump and Off-Pump Techniques

BACKGROUND

There continues to be a dilemma regarding the best means of surgical management of significant carotid artery disease in patients requiring coronary artery bypass surgery. A combined approach of coronary artery bypass and carotid endarterectomy has shown good results in patients with concomitant carotid and coronary artery disease. We reviewed our results of coronary artery surgery using conventional cardiopulmonary bypass or off-pump techniques and carotid endarterectomy done as a combined procedure.

METHODS

Between January 1996 and June 2002, 358 patients underwent concomitant coronary artery bypass and carotid endarterectomy. There were 140 males (84.3%) and 26 females (15.7%) in group I. Group II consisted of 158 males (82.3%) and 34 females (17.7%). One hundred sixty-six patients (group I) were done off pump whereas in 192 patients (group II), the procedure was done using conventional cardiopulmonary bypass. Carotid endarterectomy was performed before coronary artery bypass surgery in both groups.

RESULTS

The average number of grafts were 3.4 +/- 0.8 with average operative time of 4.2 +/- 0.4 hours in group I, and 3.3 +/- 0.8 graft with operative time of 5.3 +/- 1.2 hours in group II (p = 0.239 and p < 0.001, respectively). There were 2 deaths (1.2%) in group I and 3 deaths (1.6%) in group II (p = 0.870). No patient from group I and 1 patient (0.5%) from group II had postoperative stroke (p = 0.941). Mean hospital stay was 9.0 +/- 1.2 days in group I and 11.2 +/- 1.7 days in group II (p < 0.001). At mean follow-up of 2.8 +/- 0.9 years in group I, 2 patients (1.2%) had late death due to cardiac failure and contralateral carotid endarterectomy was done in 2 patients (1.2%). Group II had mean follow-up of 2.4 +/- 0.6 years, during which 4 patients (2.1%) had late death and contralateral carotid endarterectomy was done in 3 patients (1.6%). Late stroke was seen in 1 patient (0.6%) from group I and 2 patients (1.0%) from group II.

CONCLUSIONS

Concomitant carotid endarterectomy and coronary artery bypass is a safe and effective procedure in patients with significant coronary and carotid artery disease. Equally good results can be reproduced using cardiopulmonary bypass or off-pump techniques for coronary artery surgery, with low morbidity, mortality, and good long-term results.

GATE: a simulation toolkit for PET and SPECT

Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. This paper gives a detailed description of the design and development of GATE by the OpenGATE collaboration, whose continuing objective is to improve, document and validate GATE by simulating commercially available imaging systems for PET and SPECT. Large effort is also invested in the ability and the flexibility to model novel detection systems or systems still under design. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at http:/www-lphe.epfl.ch/GATE/. Two benchmarks developed for PET and SPECT to test the installation of GATE and to serve as a tutorial for the users are presented. Extensive validation of the GATE simulation platform has been started, comparing simulations and measurements on commercially available acquisition systems. References to those results are listed. The future prospects towards the gridification of GATE and its extension to other domains such as dosimetry are also discussed.

GATE: a simulation toolkit for PET and SPECT

Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. This paper gives a detailed description of the design and development of GATE by the OpenGATE collaboration, whose continuing objective is to improve, document and validate GATE by simulating commercially available imaging systems for PET and SPECT. Large effort is also invested in the ability and the flexibility to model novel detection systems or systems still under design. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at http:/www-lphe.epfl.ch/GATE/. Two benchmarks developed for PET and SPECT to test the installation of GATE and to serve as a tutorial for the users are presented. Extensive validation of the GATE simulation platform has been started, comparing simulations and measurements on commercially available acquisition systems. References to those results are listed. The future prospects towards the gridification of GATE and its extension to other domains such as dosimetry are also discussed.

Multivessel off-pump coronary artery bypass: analysis of 4953 cases

BACKGROUND

To avoid the harmful effects of cardiopulmonary bypass (CPB), cardiac surgeons are using off-pump coronary artery bypass (OPCAB) as an effective alternative to conventional coronary artery bypass grafting (CABG). In the present study, we analyze our results with OPCAB in patients with multivessel coronary artery disease and compare them with those achieved in patients who underwent operations on CPB.

METHODS

Between January 1997 and April 2002, 4953 patients underwent CABG without CPB (OPCAB group). These patients were compared with 7133 patients who underwent conventional on-pump CABG (CCAB group) during the same period. All patients were operated on through a median sternotomy. The Octopus was used as the mechanical stabilizer, and intracoronary shunts were used in most patients. Transesophageal echocardiography was used in all patients, and epiaortic scanning was used in selected patients.

RESULTS

The mean patient age was 59 +/- 8.9 years in the OPCAB group and 57.4 +/- 8.9 years in the CCAB group (P <.001). There were more women in the OPCAB group (11.7% versus 10.4%; P =.023), and 2.8% of the patients required conversion to CPB. The mean numbers of grafts were 3.0 +/- 0.7 and 3.2 +/- 0.8 in the OPCAB and the CCAB groups, respectively (P <.001). More patients in the CCAB group received grafts to the circumflex territory. Intubation times (19 +/- 4 hours versus 25 +/- 6 hours; P <.001), blood losses (350 +/- 41 mL versus 598 +/- 74 mL; P <.001), requirements for blood and blood products (30.8% versus 45.3%; P <.001), the frequency of reopening for bleeding (0.6% versus 2.8%; P <.001), requirements for postoperative intra-aortic balloon pump (1.3% versus 2.6%; P <.001), the frequency of atrial fibrillation OPCAB group. The mortality rate was 0.97% and 1.86% in the OPCAB and the CCAB groups, respectively (P <.001). Intensive care unit stays (23 +/- 6 hours versus 34 +/- 8 hours; P <.001) and hospital stays (5 +/- 2 days versus 8 +/- 3 days; P <.001) were significantly shorter in the OPCAB group.

CONCLUSION

OPCAB is a safe and effective procedure for patients with multivessel coronary artery disease and is associated with reduced morbidity and mortality. However, large randomized studies with long-term follow-up may show the real benefits of OPCAB compared with CABG on CPB.

Surgical treatment of post infarction left ventricular aneurysms: our experience with double breasting and Dor's repair

BACKGROUND

This is a retrospective study of left ventricle (LV) aneurysm repair done at the Escorts Heart Institute and Research Centre, New Delhi, since October 1988. Two methods of LV aneurysm repair are practiced: double breasting (DB) and Dor's repair. The method varies with location, size, and extent of aneurysm and quality of the fibrotic wall of the aneurysm.

METHODS

Between October 1988 and May 2001, 129 patients underwent LV aneurysm repair using one of the two techniques; 78 patients had Dor's repair while 51 patients had DB repair.

RESULTS

Overall mortality was 2.3% (three patients). One patient died in the DB group, and two patients died in the Dor's repair group. Mean preoperative ejection fraction (EF) after surgery in DB was 31% while in Dor's repair it was 29.2%. EF showed improvement after surgery to 48.5% in DB and 46.6% in Dor's repair. Decrease in end-diastolic volume (EDV) in DB was from 146 to 91.4 cm3/m2, and in Dor's repair it was from 156 cm3/m2 to 88.6 cm3/m2. Decrease in end-systolic volume was from 101 cm3/m2 to 60.2 cm3/m2 in DB and from 109 cm3/m2 to 64.5 cm3/m2 in Dor's group. All of these values showed statistically significant improvement. At six months postoperatively, 83 patients (74.1%) out of 112 patients who were preoperatively in New York Heart Association (NYHA) Functional Classes III and IV improved to class II while 7 patients (6.3%) improved to class I.

CONCLUSION

In our experience Dor's repair is indicated for anteroseptal and apical isolated posterior aneurysm to restore LV volume and geometry while DB is indicated for apical, anterolateral, and lateral aneurysms where septal involvement is less. These two techniques have definite indications and advantages with good results.

Predictors of early outcome after coronary artery surgery in patients with severe left ventricular dysfunction

BACKGROUND

The surgical survival in patients with severe myocardial dysfunction is critically dependent on the selection of patients. The present study was undertaken to identify the prognostic factors in such patients.

METHODS

We analyzed the data of 176 consecutive patients (161 men, 15 women), aged 29 to 88 years (mean 58.43), with a left ventricular ejection fraction (LVEF) < 30% who underwent isolated coronary artery bypass grafting. The LVEF ranged from 15% to 30% (mean 27.18%). Preoperatively, 33% had angina, 19.9% had recent myocardial infarction, and 21.6% had congestive heart failure. The mean number of grafts was 2.5/patient. The intra-aortic balloon was used prophylactically in 20.5% of patients and therapeutically in 4.0% of patients.

RESULTS

The hospital mortality was 2.3%. The complications occurred as follows: perioperative myocardial infarction in two (1.1%), intractable ventricular arrhythmias in two (1.1%), prolonged ventilation in four (2.3%) and peritoneal dialysis in 1 (0.6%). The mean ICU and hospital stay were 2.46 +/- 0.76 and 7.57 +/- 2.24 days, respectively. The predictors of survival on univariate analysis were New York Heart Association (NYHA) class (x2 = 14.458, p < 0.001), recent myocardial infarction (x2 = 5.852, p = 0.016), congestive heart failure (CHF) (x2 = 5.526, p = 0.019), and left ventricular end-systolic volume index (LVESVI) (x2 = 25.833, p < 0.001). However, on multivariate analysis, left ventricular end-systolic volume index was the only independent left ventricular function measurement predictive of survival (x2 = 10.228, p = 0.001).

CONCLUSION

Left ventricular end-systolic volume index is the most important predictor of survival after coronary artery bypass surgery in patients with severe myocardial dysfunction.

Off-pump multivessel coronary artery surgery in high-risk patients

BACKGROUND

Coronary artery bypass surgery on cardiopulmonary bypass is associated with significant morbidity and mortality, which may be more marked in high-risk patients. We evaluated our results of off-pump coronary artery bypass (OPCAB) in high-risk patients with multivessel coronary artery disease and compared them with results in similar patients who underwent operation on cardiopulmonary bypass.

METHODS

A total of 1,075 patients who underwent OPCAB between October 1996 and June 2001 and who had one or more of the following risk factors were included in the study: poor left ventricular function (EF < or = 30%), advanced age (> 70 years), left main stenosis, acute myocardial infarction, and redo coronary artery surgery. These patients were compared with 2,312 similar patients who underwent coronary artery bypass grafting on cardiopulmonary bypass during the same period. Preoperative risk factors, intraoperative variables, and postoperative results were analyzed and compared between two groups.

RESULTS

The average number of grafts was 3.0 +/- 0.4 and 3.2 +/- 0.3 in the off-pump (OPCAB) and on-pump (CCAB) groups, respectively. Hospital mortality was 3.2% and 4.5% in OPCAB and CCAB groups respectively (p = 0.109). Perioperative myocardial infarction, requirement of inotropic agents, stroke, and renal dysfunction were comparable in two groups. Intubation time (19 +/- 5 vs 24 +/- 6 hours, p < 0.001), mean blood loss (362 +/- 53 vs 580 +/- 66 mL, p < 0.001), atrial fibrillation (14.3 vs 19.7%, p < 0.001), and prolonged ventilation (4.6 vs 7.6%, p = 0.002) were less in OPCAB group. Intensive care unit stay (20 +/- 8 hours) and hospital stay (6 +/- 3 days) were significantly less in the OPCAB group (p < 0.001).

CONCLUSIONS

Off-pump coronary artery surgery can be safely performed in high-risk patients with multivessel coronary artery disease. Operative mortality is comparable to that associated with on-pump surgery, and avoidance of cardiopulmonary bypass is associated with reduced postoperative morbidity in these patients.

Beating heart versus conventional reoperative coronary artery bypass surgery

BACKGROUND

The incidence of reoperative coronary artery bypass grafting is increasing with an increase in the number of patients undergoing coronary artery bypass surgery. The clinical outcome of redo coronary artery bypass grafting without cardiopulmonary bypass and conventional coronary artery bypass grafting using cardiopulmonary bypass are different.

METHODS AND RESULTS

We compared clinical parameters in patients who underwent off-pump (n=156) versus on-pump (n=194) redo coronary artery bypass grafting performed between January 1995 and December 2001 in our institute, to determine if off-pump surgery has improved the surgical outcome of redo coronary artery bypass grafting and emerged as an ideal technique. Patients who underwent on-pump redo surgery required more postoperative blood transfusion (86.53% on-pump v. 12.82% off-pump. p=0.001), prolonged ventilatory support (>24 hours) (16.49% on-pump v. 7.7% off-pump, p=0.021) and higher inotropic support (23.71% on-pump v. 10.89% off-pump, p=0.003). On-pump redo coronary artery bypass grafting was also associated with a prolonged stay in the intensive care unit (40+/-6.2 hours on-pump v. 20+/-4.1 hours off-pump, p=0.001) and longer hospital stay (9+/-4.2 days on-pump v. 5+/-3.4 days off-pump, p=0.001). In-hospital mortality was higher in on-pump patients than in off-pump ones (7.7% v. 3.2%); however, this was not statistically significant (p=0.114).

CONCLUSIONS

Off-pump redo coronary artery bypass grafting is a safe method of myocardial revascularization with lower operative morbidity and mortality, less requirement of blood products and early hospital discharge, compared with conventional on-pump redo coronary artery bypass grafting.

Comparison of ministernotomy with minithoracotomy regarding postoperative pain and internal mammary artery characteristics

PURPOSE

This prospective clinical study focuses on postoperative pain and internal mammary artery (IMA) characteristics after ministernotomy versus left anterior minithoracotomy.

METHOD

Patients were studied in two groups. Group A consisted of 267 consecutive single vessel (IMA to left anterior descending artery (LAD)) minimally invasive direct coronary artery bypass (MIDCAB) patients using ministernotomy from the tip of the xiphoid to the fourth intercostal space. Group B consisted of the same number of MIDCAB patients operated on through anterolateral minithoracotomy. Pain was graduated using the visual analog scale (VAS). Internal mammary artery (IMA) characteristics were compared in both the groups.

RESULTS

Postoperative pain was not significant statistically on postop day (POD) 1 in either of the groups (p = 0.07). From POD 2 onwards Group A patients had less pain than Group B patients (p < 0.05), and the pain medication requirement from POD 2 onwards was less in Group A than in Group B. Length of harvested IMA was 15.6 +/- 2.1 cm in Group A as compared to 10.4 +/- 2.2 cm in Group B (p < 0.05). Free flow of IMA in group A was 56 +/- 16 ml/min., whereas in Group B the flow was 50 +/- 14 ml/min. (p = 0.04).

CONCLUSION

Compared to patients undergoing MIDCAB using ministernotomy, anterolateral minithoracotomy patients suffer more pain from POD 2 onwards and their postoperative pain medication requirement is also higher. Length and free flow of IMA is better in patients operated on for MIDCAB using ministernotomy. Thus, ministernotomy is a better approach than minithoracotomy in terms of postoperative pain and IMA characteristics for single-vessel MIDCAB patients.

Calmodulin binding to the C-terminus of the small-conductance Ca2+-activated K+ channel hSK1 is affected by alternative splicing

We identified three splice variants of hSK1 whose C-terminal structures are determined by the independent deletion of two contiguous nucleotide sequences. The upstream sequence extends 25 bases in length, is initiated by a donor splice site within exon 8, and terminates at the end of the exon. The downstream sequence consists of nine bases that compose exon 9. When the upstream sequence (hSK1(-)(25b)) or both sequences (hSK1(-)(34b)) are deleted, truncated proteins are encoded in which the terminal 118 amino acids are absent. The binding of calmodulin to these variants is diminished, particularly in the absence of Ca2+ ions. The first 20 amino acids of the segment deleted from hSK1(-)(25b) and hSK1(-)(34b) contain a 1-8-14 Ca2+ calmodulin binding motif, and synthetic oligopeptides based on this region bind calmodulin better in the presence than absence of Ca2+ ions. When the downstream sequence (hSK1(-)(9b)) alone is deleted, only the three amino acids A452, Q453, and K454 are removed, and calmodulin binding is not reduced. On the basis of the relative abundance of mRNA encoding each of the four isoforms, the full-length variant appears to account for most hSK1 in the human hippocampus, while hSK1(-)(34b) predominates in reticulocytes, and hSK1(-)(9b) is especially abundant in human erythroleukemia cells in culture. We conclude that the binding of calmodulin by hSK1 can be modulated through alternative splicing.

Discrete subvalvular aortic stenosis in adults

Discrete subvalvular aortic stenosis is a relatively rare condition in adults. It is often diagnosed during first decade of life especially in association with other congenital malformations. Isolated form of discrete subvalvular aortic stenosis may however silently progress from innocent murmurs of childhood and adolescence to symptomatic left ventricular outflow tract obstruction in adults. Certain overt and subtle morphological abnormalities may underlie the initial expression as well as high recurrence rates after surgical resection of sub aortic membrane. Though surgical resection is the only treatment available, debate on the surgical technique and appropriate timing of surgery continues. Close followup with serial echocardiographic examinations in patients detected to have functional murmurs during childhood may be helpful in early detection of subvalvular aortic stertosis.

Discrete subvalvular aortic stenosis

Discrete Subaortic Stenosis is one of the many lesions responsible for left ventricular outflow tract (LVOT) obstruction. It may present as in an isolated from as membranous or fibromuscular ring below the aortic valve or in association with other congenital anamolies such as VSD, PDA, coarctation of aorta, hypoplastic aortic annulus, double chamber right ventricle among others. The condition is rarely diagnosed antenataly or in infancy but often manifests in the first decade of life with features of progressive LVOT obstruction, LV hypertrophy and dysfunction aortic regurgitation due to damage to the aortic cusps because of the jet from the subaortic narrowing which may also render the aortic valve prone to infective endocarditis. Interaction of genetic predisposition and morphologically deformed long and narrow LVOT cause rheological abnormalities and increased shear stress in the region of subaortic stenosis and seem to be the main etiological factor alongwith poorly defined role of more extensive but subtle changes in the LV endocardium. Condition can be easily diagnosed by cross-sectional and Doppler echocardiography and confirmed by demonstrating a pressure gradient below aortic valve on cardiac catheterisation and LV angiography. Surgical membranectomy alongwith myotomy or myomectomy remain the mainstay of treatment but long term results are not satisfactory as there is a high rate of recurrences requiring reoperations. A close follow up with serial echocardiographic examinations is very helpful in early detection of subaortic obstruction in patients who have so called functional murmurs in the childhood.

Calpain inhibition prevents sinusoidal endothelial cell apoptosis in the cold ischemic rat liver

BACKGROUND

Cold preservation of the liver followed by reperfusion results in sinusoidal endothelial cell (SEC) apoptosis. Calpain-like activity is dramatically increased during reperfusion and inhibition of calpains results in lower graft injury and longer survival. Recently, calpains have been implicated in inducing apoptosis. Our aim was to determine the effect of calpain inhibition on SEC apoptosis.

METHODS

Livers were stored in the University of Wisconsin solution for 24 hr (survival conditions) and 40 hr (nonsurvival conditions) and ex vivo reperfused for 1 hr at 37 degrees C. Calpain-like activity was inhibited in some experiments using an i.p. injection of a selective inhibitor 2 hr before explantation. Apoptosis was quantified using the terminal deoxynucleotidyl trans. ferase-mediated dUTP nick end-labeling assay. Cross-inhibition by the inhibitor was determined for caspases 1 and 3.

RESULTS

Apoptosis of exclusively the SEC was a key feature of reperfusion injury after both storage periods in University of Wisconsin solution after 1 hr normothermic reperfusion. Inhibition of calpain activity with Cbz-Val-Phe methyl ester resulted in a 50% reduction of apoptotic SEC in the 40-hr preserved liver, and an almost complete abrogation of SEC apoptosis after 24 hr preservation. Only minimal cross-inhibition of caspases was determined at high concentrations in vitro by the calpain inhibitor.

CONCLUSION

Apoptosis of exclusively SEC is a key feature of reperfusion injury partially mediated through calpain-dependent processes. Calpain inhibition reduces the number of apoptotic SEC. Based on these data and our previous work, calpain inhibition may prove to be useful in clinical transplantation.

Paired ventricular pacing: an alternative therapy for postoperative junctional ectopic tachycardia in congenital heart disease

Junctional ectopic tachycardia (JET) is one of the most life-threatening postoperative arrhythmias in children with congenital heart disease, and medical management is difficult. Paired ventricular pacing (PVP) may provide a safe alternative mode of management. We evaluated the safety and efficacy of PVP for the management of postoperative JET in patients with congenital heart disease. A retrospective collection of data was done from 1981-1995. PVP was successfully tried in five postoperative patients (age range: 37 days to 22 years, median: 10 months). Onset of JET was 3-60 hours (mean +/- SD, 19 +/- 23 hours) postoperatively. The maximal JET rate was 261 +/- 39 beats/min. PVP was used as the first line of management in three patients and was successful in all patients. It resulted in an instantaneous increase in blood pressure from 66 +/- 9 to 94 +/- 15 mmHg (42% increase) and was required for 12 +/- 14 hours (range 2-36 hours). No complications were noted. Therefore, in our experience, this is a safe alternative modality for the control of postoperative JET.

Endothelial cell and hepatocyte deaths occur by apoptosis after ischemia-reperfusion injury in the rat liver

BACKGROUND

Ischemic injury of the liver is generally considered to result in necrosis, but it has recently been recognized that mediators of apoptosis are activated during ischemia/reperfusion. This study was designed to characterize the extent and the type of cells within the liver that undergo apoptosis at different periods of ischemia and reperfusion.

METHODS

Male Wistar rats were subjected to 30 or 60 min of normothermic ischemia. Liver sections were evaluated at the end of ischemia and at 1, 6, 24, and 72 hr after reperfusion. Apoptosis was determined by DNA fragmentation as evaluated by laddering on gel electrophoresis, in situ staining for apoptotic cells using TdT-mediated dUTP-digoxigenin nick-end labeling (TUNEL), and morphology on electron microscopy.

RESULTS

In situ staining of liver biopsy specimens using TUNEL showed significant apoptosis after reperfusion. Sinusoidal endothelial cells (SEC) showed evidence of apoptosis earlier than hepatocytes. For example, at 1 hr of reperfusion after 60 min of ischemia, 22+/-4% of the SEC stained TUNEL positive compared with 2+/-1% of the hepatocytes (P<0.001). With a longer duration of ischemia, a greater number of SEC and hepatocytes became TUNEL positive. An increase in TUNEL-positive cells was also noted with an increasing duration of reperfusion. The presence of apoptotic SEC and hepatocytes was supported by DNA laddering on gel electrophoresis and cell morphology on electron microscopy. Several Kupffer cells were seen containing apoptotic bodies but did not show evidence of apoptosis. Only rare hepatocytes showed features of necrosis after 60 min of ischemia and 6 hr of reperfusion.

CONCLUSION

These results suggest that apoptosis of endothelial cells followed by hepatocytes is an important mechanism of cell death after ischemia/reperfusion injury in the liver.

Controlled ventilation enhances catheter stability during radiofrequency ablation

Variations in the amplitude of the atrial and ventricular depolarization waves of the intracardiac electrogram occur during different phases of respiration. Therefore, we tested whether controlled ventilation would reduce ablation attempts and increase the rate of success in patients undergoing radiofrequency ablation with general anesthesia. Thirty-eight children were divided into two groups: (1) controlled and (2) noncontrolled or cyclic ventilation. In the controlled ventilation group, the mapping electrogram was recorded during sustained inspiration, sustained expiration, and cyclic ventilation. Ablation was done in the phase of ventilation that had the least variability in atrial and ventricular amplitudes. Seventeen patients in the controlled ventilation group had tracings adequate for review. In eight patients, ablation was done during sustained inspiration with the percentage change of atrial and ventricular amplitudes (15% +/- 16% and 13% +/- 16%, respectively) being < that during sustained expiration (38% +/- 27%, P = 0.04 and 20% +/- 21%) or during cyclic ventilation (57% +/- 27%, P < 0.01 and 54% +/- 26%, P = 0.003). In nine patients, ablation was done during sustained expiration with the percentage change of atrial and ventricular amplitudes (5% +/- 5% and 5% +/- 2%) being less than that during sustained inspiration (21% +/- 14%, P = 0.01 and 11% +/- 6%, P = 0.01) or during cyclic ventilation (68% +/- 23%, P < 0.001 and 48 +/- 26%, P = 0.001). We achieved success with each patient in both groups, but the number of ablation attempts were less in the controlled ventilation group 1 (3 +/- 2), as compared to the cyclic ventilation group 2 (8 +/- 8; P < 0.02). We concluded that controlled ventilation reduced the number of ablation attempts and facilitated the ablation procedure.

Calpain mediates ischemic injury of the liver through modulation of apoptosis and necrosis

BACKGROUND & AIMS

Calpain proteases have been implicated in cell death by necrosis and more recently by apoptosis. Experiments were designed to determine the role of calpain proteases in ischemic rat liver injury by measurement of cytosolic calpain activity after different periods of ischemia-reperfusion and by evaluation of the effects of calpain inhibition on tissue injury and animal survival.

METHODS

Calpain activity was measured in the cytosol using Suc-Leu-Leu-Val-Try-7 amino-4 methyl coumarin, a specific fluorogenic substrate, and Cbz-Leu-Leu-Tyr-CHN2, a specific inhibitor.

RESULTS

Calpain activity increased significantly with the duration of ischemia-reperfusion and was inhibited more than 80% by the inhibitor. Calpain inhibition resulted in a significant decrease in transaminase release and tissue necrosis and converted nonsurvival ischemic conditions to survival conditions. When the in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick-end labeling assay for apoptosis was used, 35% +/- 6% of nonparenchymal cells and 16% +/- 3% of hepatocytes stained positively after 60 minutes of ischemia and 6 hours of reperfusion. In contrast, animals pretreated with the calpain inhibitor showed minimal evidence of apoptosis. This was further substantiated by gel electrophoresis assay for DNA fragmentation and by electron-microscopic evaluation.

CONCLUSIONS

These data suggest that calpain proteases play a pivotal role in warm ischemia-reperfusion injury of the rat liver through modulation of apoptosis and necrosis.