Comparison of epicardial and endocardial linear ablation using handheld probes

BACKGROUND: The optimal technique for producing linear radiofrequency thermal lesions in myocardial tissue is unclear. We compared epicardial ablation on the beating heart with endocardial ablation after cardioplegia. METHODS: Radiofrequency lesions were produced using a multielectrode malleable handheld probe in ovine myocardium with three wall thicknesses. Detailed analysis of lesion dimensions was used to assess the effects of site of ablation, muscle thickness, and duration of ablation. RESULTS: After epicardial atrial ablation, myocardial lesions were detected in all sections without macroscopically visible epicardial fat (n = 10), but only 43% (6/14) of sections with epicardial fat. Three of 24 atrial epicardial sections (13%) and 92% (23/25) of endocardial atrial lesion sections were clearly transmural. In thicker tissues lesion depth was independent of endocardial (right ventricle: 3.9 +/- 1.1 mm, left ventricle: 3.8 +/- 0.7 mm) or epicardial (right ventricle: 3.4 +/- 0.6 mm, left ventricle: 4.3 +/- 0.9 mm) ablation site. Epicardial lesions are less deep in thinner areas of myocardium (p = 0.003). Lesions were all wider than they were deep. There was no significant increase in lesion depth with the increase in ablation duration from 1 to 2 minutes. CONCLUSIONS: Lesions were unlikely to be transmural with either technique when the wall thickness was greater than about 4 mm. Epicardial fat has an important negative effect on epicardial lesion formation. Where epicardial fat is absent epicardially produced lesions penetrate less deeply when the wall thickness is small, possibly due to endocardial cooling by circulating blood. Prolongation of the duration of ablation from 1 to 2 minutes does not significantly increase lesion depth.     

Myocardial Revascularization in Patients With Ischemic Cardiomyopathy: Functional Observations

Objective. A prospective angiographic study was undertaken to investigate, with an objective analysis, the global and regional wall response to myocardial revascularization.

Methods. Thirty-one patients (30 men and 1 woman, mean age, 61 years) with a left ventricular ejection fraction of less than 0.30 were admitted to our institution between 1992 and 1995 for two- or three-vessel coronary artery disease requiring myocardial revascularization. All patients underwent isolated coronary artery bypass grafting and were studied 3 months later with angiography. Preoperative and postoperative wall motion were analyzed using special software that computed a segmental left ventricular ejection fraction, generating a segmental score. Computerized analysis allowed us to distinguish patients with diffuse hypokinesis and a symmetric contraction pattern from patients with akinesis involving at least two segments and an asymmetric contraction pattern.

Results. There were no operative deaths and no patient required intraaortic balloon counterpulsation. One patient had postoperative enzymatic evidence of myocardial infarction. Postoperative angiography showed a graft patency rate of 84%. Global analysis showed a small but significant rise in the left ventricular ejection fraction (0.25 ± 0.51 to 0.31 ± 0.70, p < 0.001) and a fall in the left ventricular end-diastolic pressure (23.7 ± 10 to 16.5 ± 9 mm Hg, p < 0.01). Mean scores always have been lower after the operation than before it, with the best results obtained for the apex and the worst for the anterobasal segment. The group with a symmetric contraction pattern showed a trend toward a better hemodynamic response than the group with an asymmetric contraction pattern. Regression analysis revealed two important predictors of segmental functional improvement: (1) the absence of an echocardiographic scar, and (2) the presence of a collateral circulation.

Conclusions. Coronary artery bypass grafting produced a small but substantial improvement in patients with ischemic cardiomyopathy. The greater benefit occurred in patients with a symmetric contraction pattern. The absence of an echocardiographic scar and the presence of a collateral circulation predicted segmental functional improvement.     

Continuous monitoring of myocardial acid–base status during intermittent warm blood cardioplegia

Objective: Intermittent warm blood cardioplegia (IWBC) is a well-established technique for myocardial protection during cardiac operations. According to standardized protocols, IWBC administration is currently performed every 15–20 min regardless of any individual variable and in the absence of any instrumental monitoring. We devised a new system for continuous measurement of the acid–base status of coronary sinus blood for on-line evaluation of myocardial oxygenation during IWBC. Methods: In 19 patients undergoing cardiac surgery for coronary artery bypass graft and/or valve surgery and receiving IWBC (34–37°C) by antegrade induction (3 min) and retrograde or antegrade maintenance (2 min) every 15 min, continuous monitoring of myocardial oxygenation and acid/base status was performed by means of a multiparameter PO₂, PCO₂, pH, and temperature sensor (Paratrend7 ®, Philips Medical System) inserted into the coronary sinus. Results: Mean cross-clamping time was 76±26 min; ischemic time was 13±0.2 min. pH decline was not linear, showing an initial fast decline, a point of flexus, and a progressive slow decline. After every ischemic period, the pH adaptation curve showed a complex pattern reaching step-by-step lower minimum levels (7.28±0.14 during the first ischemic period, to 7.16±0.19 during the third ischemic period – P=0.003). PO₂ decreased rapidly at 90% in 5.0±1.2 min after every reperfusion. During ischemia, PCO₂ increased steadily at 1.6±0.1 mmHg per minute, with progressively incomplete removal after successive reperfusion, and progressive increase of maximal level (42±12 mmHg during the first ischemic period, to 53±23 mmHg during the third ischemic period – P=0.05). Conclusions: Myocardial oxygen, carbon dioxide, and pH show marked changes after repeated IWBC. Myocardial ischemia is not completely reversed by standardized reperfusions, as reflected by steady deterioration of PCO₂ and pH after each reperfusion. Progressive increase of reperfusion durations or direct monitoring of myocardial oxygenation could be advisable in cases of prolonged cross-clamping time.     

Depressed Function in Remote Myocardium After Myocardial Infarction: Influence of Orotic Acid

Background. We have previously shown that infarction impairs recovery of global function after subsequent cardioplegic arrest and that therapy with orotic acid improves recovery. The aim of this study was to measure the effect of infarction on regional and global left ventricular function and to determine whether orotic acid exerts a beneficial effect exclusive of the effects of cardioplegia.

Methods. Acute myocardial infarction was produced in dogs. They then received either orotic acid or placebo (control) orally (n = 12 per group). Fractional radial shortening and systolic wall thickening were measured by two-dimensional echocardiography before and 1 and 3 days after infarction with and without β-adrenergic blockade, and in 6 dogs up to 9 days after infarction. Global function was measured under anesthesia 4 days after infarction.

Results. In control animals, fractional radial shortening in the infarct decreased from 20.6% ± 5.1% before infarction to 3.0% ± 2.2% at day 1 and to 1.9% ± 1.9% at day 3 (p < 0.01). In the border zone radial shortening declined from 21.9% ± 3.7% to 11.0% ± 2.3% at day 1 and 9.3% ± 2.8% at day 3 (p < 0.05). In the noninfarcted myocardium radial shortening also declined from 27.1% ± 1.9% before infarction to 18.3% ± 2.3% on day 1 (p < 0.05) and to 16.0% ± 2.8% on day 3 after infarction (p < 0.05) with recovery to preinfarct levels by 9 days after infarction. These findings were confirmed by measurements of systolic thickening. Before infarction β-receptor blockade decreased fractional shortening in all regions of the left ventricle, but this effect was absent on day 3 after infarction, implying that the myocardium had become less responsive to β-adrenergic stimulation. Measurements of global function 4 days after infarction showed marked depression of stroke work. There was no effect of orotic acid treatment on regional or global function.

Conclusions. Myocardial infarction causes reversible depression of resting function and β-adrenergic responsiveness in the remote and border zone areas, which is not prevented by metabolic therapy with orotic acid. This finding may explain the adverse response of the infarcted heart to cardioplegic arrest.

(Ann Thorac Surg 1996;62:1765–72)     

Hemodynamic changes with right lateral decubitus body positioning in the tilted porcine heart

Background. In beating-heart coronary surgical procedures, exposure of posterior vessels through sternotomy causes cardiac function to deteriorate. We hypothesized that turning the subject to the right lateral decubitus position before cardiac retraction improves exposure of posterior vessels and preserves cardiac pump function on displacement.

Methods. Eight 80-kg open-chest pigs were instrumented with catheter-tip manometers. After a stepwise 60-degree turn to the right lateral decubitus position of the body, the heart was retracted anteriorly to 90 degrees with a suction stabilizer.

Results. Right lateral body positioning caused an approximately 45-degree right deviation of the apex, thereby exposing the left atrial groove. Stroke volume, mean arterial pressure, right atrial pressure, and right ventricular end-diastolic pressure increased to 106% ± 5% (mean ± standard error of the mean, p = 0.31), 106% ± 3% (p = 0.01), 129% ± 8% (p = 0.001), and 171% ± 14% (p = 0.002), respectively, compared with control values. In contrast, left atrial pressure decreased to 73% ± 6% (p = 0.007), whereas left ventricular preload remained unchanged (110% ± 8%, p = 0.26). Additional anterior displacement to 90 degrees fully exposed the posterior vessels, and stroke volume decreased to 90% ± 3% (p = 0.01) and mean arterial pressure to 93% ± 5% (p = 0.07) at the expense of further increased right ventricular preload (256% ± 28%, p < 0.001).

Conclusions. By placing the subject in the right lateral decubitus position, exposure through sternotomy of posterior vessels in the beating porcine heart was facilitated while mean arterial pressure was maintained.     

Temporary decompression of the right ventricle to assess the right ventricle-dependent coronary circulation in pulmonary atresia with intact ventricular septum

We repaired a case of pulmonary atresia with intact ventricular septum in which the blood supply to the left anterior descending coronary artery depended on the right ventricle. At the time of a bidirectional Glenn operation, total cardiopulmonary bypass with venous drainage from the right atrium was performed in order to evaluate the safety of right ventricular decompression required for a planned Fontan operation. We confirmed the dependence of the coronary perfusion on the right ventricle by demonstrating transient depression of the ST segment in the epicardial electrocardiogram during temporary decompression of the right ventricle. To prevent ischemic myocardial damage, we then performed an extracardiac Fontan operation with a temporary venous shunt and without cardiopulmonary bypass.     

The effects of therapeutic sulfide on myocardial apoptosis in response to ischemia–reperfusion injury

Objective: Ischemia–reperfusion (I/R) injury, often encountered clinically, results in myocardial apoptosis and necrosis. Hydrogen sulfide (H₂S) is produced endogenously in response to ischemia and thought to be cardioprotective, although its mechanism of action is not fully known. This study investigates cardioprotection provided by exogenous H₂S, generated as sodium sulfide on apoptosis following myocardial I/R injury. Methods: The mid-LAD coronary artery in Yorkshire swine (n = 12) was occluded for 60 min, followed by reperfusion for 120 min. Controls (n = 6) received placebo, and treatment animals (n = 6) received sulfide 10 min prior to and throughout reperfusion. Hemodynamic, global, and regional functional measurements were obtained. Evans blue/TTC staining identified the area-at-risk (AAR) and infarction. Serum CK-MB, troponin I, and FABP were assayed. Tissue expression of bcl-2, bad, apoptosis-inducing-factor (AIF), total and cleaved caspase-3, and total and cleaved PARP were assessed. PAR and TUNEL staining were performed to assess apoptotic cell counts and poly-ADP ribosylation, respectively. Results: Pre-I/R hemodynamics were similar between groups. Post-I/R, mean arterial pressure (mmHg) was reduced by 30.2 ± 4.3 in controls vs 8.2 ± 6.9 in treatment animals (p = 0.01). +LV dP/dt (mmHg/s) was reduced by 1308 ± 435 in controls vs 403 ± 283 in treatment animals (p = 0.001). Infarct size (% of AAR) in controls was 47.4 ± 6.2% vs 20.1 ± 3.3% in the treated group (p = 0.003). In treated animals, CK-MB and FABP were lower by 47.0% (p = 0.10) and 45.1% (p = 0.01), respectively. AIF, caspase-3, and PARP expression was similar between groups, whereas cleaved caspase-3 and cleaved PARP was lower in treated animals (p = 0.04). PAR staining was significantly reduced in sulfide treated groups (p = 0.04). TUNEL staining demonstrated significantly fewer apoptotic cells in sulfide treated animals (p = 0.02). Conclusions: Sodium sulfide is efficacious in reducing apoptosis in response to I/R injury. Along with its known effects on reducing necrosis, sulfide's effects on apoptosis may partially contribute to providing myocardial protection. Exogenous sulfide may have therapeutic utility in clinical settings in which I/R injury is encountered.     

Long-term results of bilateral internal thoracic artery grafting

Background. Little is known about the long-term results of the uniform group of patients who had bilateral internal thoracic artery (ITA) grafting with the method of left ITA-to-left anterior descending coronary artery and right ITA-to-circumflex artery.

Methods. Late follow-up study was performed in the first consecutive 203 patients (mean age, 62.6 ± 9.1 years) who underwent isolated coronary artery bypass grafting with the left ITA anastomosed to the left anterior descending coronary artery and the right ITA to major branches of the circumflex artery. The patients were grouped according to the patency of ITA grafts demonstrated by early postoperative angiography (Both patent (BP) group, 168 patients: both ITAs showed complete patency; Not patent (NP) group, 23 patients: at least one ITA was dysfunctional).

Results. Actuarial 7-year survival in all patients was 89.3% ± 3.1%. The cumulative probability of event-free survival for cardiac death, myocardial infarction, intervention, and angina at 7 years was 96.6% ± 1.8%, 98.0% ± 1.5%, 86.7% ± 3.2%, and 90.7% ± 2.9%, respectively. NP group had more myocardial infarction and angina than the BP group, but was not statistically significant. Because of failed grafts at the early angiography, intervention was performed more frequently in NP group (p < 0.01).

Conclusions. Our results of actuarial 7-year survival and the cumulative probability of event-free survival were at least comparable to the results of other similar studies using bilateral ITA. The freedom from angina appeared to be better than in the previous study. Overall our study supports the continued use of this method of ITA grafting.     

Effects of Cardiomyoplasty on Right Ventricular Filling During Volume Loading

Background. Although cardiomyoplasty (CMP) is thought to improve ventricular systolic function, its effects on ventricular diastolic function are not clear. Especially the effects on right ventricular diastolic filling have not been fully investigated. Because pericardial influences are more pronounced in the right ventricle than in the left ventricle, CMP with its external constraint may substantially impair right ventricular diastolic filling.

Methods. Fourteen purebred adult beagles were used in this study. Seven underwent left posterior CMP, and 7 underwent a sham operation with a pericardiotomy and served as controls. Four weeks later, the hemodynamic effects of CMP were evaluated by heart catheterization before and after volume loading (central venous infusion of 10 mg/kg of 4.5% albumin solution for 5 minutes).

Results. In the CMP group, mean right atrial pressure and right ventricular end-diastolic pressure increased significantly from 3.1 ± 1.2 mm Hg to 6.1 ± 2.0 mm Hg (p < 0.001) and from 4.0 ± 1.8 mm Hg to 9.6 ± 2.5 mm Hg (p < 0.001), respectively. Volume loading in the control group did not significantly increase either variable. Right ventricular end-diastolic volume and stroke volume did not change significantly (from 53 ± 9.3 mL to 60 ± 9.0 mL and from 20 ± 2.3 mL to 21 ± 3.2 mL, respectively) in the CMP group. In the control group, however, right ventricular end-diastolic volume and stroke volume increased significantly from 45 ± 7.7 mL to 63 ± 14 mL (p < 0.05) and from 18 ± 4.3 mL to 22 ± 4.2 mL (p < 0.05), respectively.

Conclusions. These results suggest that CMP may reduce right ventricular compliance and restrict right ventricular diastolic filling in response to rapid volume loading because of its external constraint.     

Intraaortic Balloon Counterpulsation Improves Right Ventricular Failure Resulting From Pressure Overload

Background. Right ventricular (RV) dysfunction is common after heart transplantation, and myocardial ischemia is considered to be a significant contributor. We studied whether intraaortic balloon counterpulsation would improve cardiac function using a model of acute RV pressure overload.

Methods. In 10 anesthetized sheep, RV failure was induced using a pulmonary artery constrictor. Baseline measurements included mean systemic blood pressure, RV peak systolic pressure, cardiac index, and RV ejection fraction. Myocardial and organ perfusion were measured using radioactive microspheres.

Results. After pulmonary artery constriction, there was an increase in RV peak systolic pressure (32 ± 2 to 60 ± 3 mm Hg; p < 0.01) and a decrease in mean systemic blood pressure (68 ± 4 to 49 ± 2 mm Hg; p < 0.01), RV ejection fraction (0.51 ± 0.04 to 0.16 ± 0.02; p < 0.01), and cardiac index (2.48 ± 0.04 to 1.02 ± 0.11; p < 0.01). Blood flow to the RV did not change significantly, but there was a significant reduction in blood flow to the left ventricle. The initiation of intraaortic balloon counterpulsation (1:1) using a 40-mL intraaortic balloon inserted through the left femoral artery resulted in an increase in mean systemic blood pressure (49 ± 2 to 61 ± 3 mm Hg; p < 0.01), cardiac index (1.02 ± 0.11 to 1.45 ± 0.14; p < 0.05), RV ejection fraction (0.16 ± 0.02 to 0.23 ± 0.02; p < 0.01), and blood flow to the left ventricle.

Conclusions. In a model of right heart failure, the institution of intraaortic balloon counterpulsation caused a significant improvement in cardiac function. Although RV ischemia was not demonstrated, the augmentation of left coronary artery blood flow by intraaortic balloon counterpulsation and subsequent improvement in left ventricular function suggest that left ventricular ischemia contributes to RV dysfunction, presumably through a ventricular interdependence mechanism. Therefore, study of the safety and efficacy of intraaortic balloon counterpulsation in the management of patients with acute right heart dysfunction is warranted.     

Distribution of myocardial blood flow after left coronary occlusion

Myocardial blood flow (MBF) in eight anatomically similar canine left ventricles was determined by injection of radioactive microspheres during baseline conditions and immediately after sequential occlusion of the left anterior descending (LAD) and circumflex coronary arteries (LCF). The left ventricle was divided into: posterior, lateral, anterior, and septal zones, apex and base, and endocardial epicardial layers for mapping of left ventricular MBF by gamma counting. Areas with significant flow reduction showed a reversal of the ENDO/EPI ratio to <1 from the normal ratio of 1.2–1.3. After LAD occlusion the anterior wall received more collateral flow from the LCF than did the posterior wall from the LAD after LCF occlusion. After occlusion of LCF, MBF to the posterior wall and the basal portion of the lateral wall were most severely reduced; after the occlusion of LAD only the apical portion of the anterior wall showed marked MBF reduction. The interventricular septum received considerable heterogenous flow when either the LCF or LAD was occluded.     

Right ventricle-to-pulmonary artery shunt and modified Blalock–Taussig shunt in preparation to hemi-Fontan procedure in children with hypoplastic left heart syndrome

Objective: The advantageous effect of right ventricle-to-pulmonary artery shunt (RV–PA) on the early postoperative hemodynamics in the Norwood procedure for hypoplastic left heart syndrome (HLHS) is well known. Numerous controversies still exist with respect to the late consequences of this new palliation method in preparation for the second stage procedure. Methods: Between September 1997 and September 2004, a consecutive series of 78 children with HLHS from a single institution underwent the hemi-Fontan procedure: Group 1 (n=27) after Blalock–Taussig shunt (BT), and Group 2 (n=51) after RV–PA. Hemodynamic, echocardiographic and clinical perioperative data were analyzed. Results: There were no significant differences in the age and operative weight (Group 1: 6.9±1.04 months, 6.22±0.99 kg; Group 2: 6.57±1.12 months, 6.36±0.86 kg). Children after RV–PA were characterized by a significantly higher preoperative hematocrit value (P=0.014), lower aortic and superior vena cava oxygen blood saturation (P<0.001, P=0.024), severe right ventricle hypertrophy more rarely diagnosed in echocardiography (P<0.004), lower Qp:Qs ratio (P=0.011), larger right (P=0.001) and left (P=0.006) pulmonary artery index and a shorter intensive care unit stay after the hemi-Fontan procedure (P=0.004). Conclusions: The Norwood procedure with the RV–PA shunt provides satisfactory late hemodynamics and improves the development of the pulmonary arteries. Children with hypoplastic left heart syndrome subjected to this new method of palliation are good candidates for the hemi-Fontan procedure.     

Surgical approach to anterior septal accessory pathways in 20 patients with the Wolff-Parkinson-White syndrome

Right anterior septal accessory pathways in the Wolff-Parkinson-White syndrome are generally defined by electrophysiological criteria, the most important being that earliest retrograde atrial activation during AV reciprocating tachycardia occurs at the anterior medial segment of the tricuspid annulus (His bundle catheter). The purpose of our study is to describe intraoperative mapping in 20 patients with anterior septal accessory pathways, and to assess if intraoperative mapping contributes to the operative approach. At surgery, all patients had identical early ventricular activation during pre-excitation at the infundibulum. However, two groups could be identified on the basis of retrograde atrial epicardial activation during AV reciprocating tachycardia or right ventricular pacing. Group 1 comprised 16 patients with earliest activation at the interatrial septum adjacent to the His bundle. Epicardial dissection failed to affect accessory pathway conduction. The accessory pathway was only ablated when a discrete endocardial approach to the atrial septum was used. Group 2 comprised 4 patients with early atrial activation "paraseptally" in the right coronary fossa. These accessory pathways were ablated by an epicardial approach without using cardiopulmonary bypass. We conclude that right anterior septal accessory pathways as defined by electrophysiological criteria can be divided into two groups on the basis of the atrial activation sequence: (1) right septal accessory pathways in the septal para-Hissian region and (2) right anterior 'paraseptal' accessory pathways. This classification is of practical importance because the latter can be ablated using an epicardial approach without the need for cardiopulmonary bypass or atriotomy.     

微创外科心脏同步化技术临床应用及文献复习

目的 介绍并探讨微创外科心外膜电极技术同步化治疗缺血性心肌病心力衰竭的效果.方法 2007年7月1例诊断缺血心肌病心力衰竭而无法进行再血管化治疗病人,经心电图和组织多普勒技术明确诊断心衰伴心脏不同步运动.先在全麻双腔气管插管超声引导下左锁骨下静脉穿刺放置右心房和右心室心内膜电极.然后利用胸腔镜和心外膜电极技术,于术中组织多普勒食管监测下测试左心室侧壁不同位置,寻找同步化效果最理想的位置,并使用无损伤缝线固定左心室心外膜电极.围术期监测心脏结构、功能和同步化效果.结果 病人术中电极放置顺利,术后顺利拔除气管插管,无并发症.术后临床症状改善顺利出院.左心室最大收缩延迟时间由术前396 ms缩短为100 ms,左心室不同步指数(TS-SD)由术前的133 ms降为22ms,心室间机械延迟(IVMD)由术前65 ms降为20 ms.左心室射血分数由术前0.37升到0.46.结论 应用微创外科心外膜电极技术完成缺血性心肌病心力衰竭同步化治疗安全可行,能获得良好的同步化效果.     

Intramyocardial microdepot injection increases the efficacy of skeletal myoblast transplantation

Objective: Recent progress in the field of cellular cardiomyoplasty has opened new prospects for the treatment of ischemic heart disease and currently moves from bench to bedside. The aim of the present study was to develop a novel cell delivery technique, reducing target tissue damage and improving cell dispersion and engraftment. Methods: In 30 male Fischer F344 rats an infarction of the left ventricle was generated by ligation of the left anterior descendent artery. Seven days after infarction, either 15 microdepots of 10 μl myoblast cell suspension (microdepot group) or culture medium (control group) were injected into the infarcted region using an automatic pressure injection device, or three depots of 50 μl myoblast cell suspension (macrodepot group) were injected using the standard surgical technique. Echocardiography was performed in all rats before and 6 weeks after cell injection. In all groups the perioperative mortality was below 20%. Six weeks after cell transplantation, a significant improvement of ejection fraction was seen in both myoblast treated groups compared to controls (macrodepot, microdepot, control; 53.7±11.9, 70.7±2.0, 39.1±6.4; P=0.026, P<0.001). The microdepot group showed a more decent improvement than the macrodepot group (70.7±2.0 vs. 53.7±11.9, P=0.013). In both treated groups, grafted myoblasts differentiated into multinucleated myotubes within host myocardium, however, the engraftment pattern was different and angiogenesis was enhanced in the microdepot group. Conclusions: Intramyocardial multisite pressure injection allows the safe and reliable transplantation of several myoblast microdepots into an infarcted myocardium and improves the efficacy of myoblast transplantation compared to the standard technique.     

The evolution of the surgical methods for interruption of right free wall Kent bundles

In 17 patients with right free wall accessory pathways of conduction of the Kent type, three different operations were used that evolved as the surgical experience increased. Localization was by intraoperative electrophysiological methods in 16 patients and by preoperative study in 1. The types of operation were an epicardial ventricular approach in 2 patients, an endocardial atrial approach in 14, and an epicardial approach without atriotomy using cryothermic ablation in 1. The most important surgical principle was extensive separation of the coronary sulcus fat from the atrium, annulus fibrosus, and ventricle. All pathways were interrupted, although 1 patient had to have a second operation. There were no deaths or serious complications. The success of operation in Patient 1 in our series of 17 patients with right free wall pathways proved that Kent bundles cause the arrhythmia in Wolff-Parkinson-White syndrome. It is concluded that the principles on which are based the surgical treatment of arrhythmias due to right free wall Kent bundles are well established and that in selected patients, the operation may be done without cardiopulmonary bypass.     

Mesenchymal stem cell implantation in a swine myocardial infarct model: engraftment and functional effects

Background. A novel therapeutic option for the treatment of acute myocardial infarction involves the use of mesenchymal stem cells (MSCs). The purpose of this study was to investigate whether implantation of autologous MSCs results in sustained engraftment, myogenic differentiation, and improved cardiac function in a swine myocardial infarct model.

Methods. MSCs were isolated and expanded from bone marrow aspirates of 14 domestic swine. A 60-minute left anterior descending artery occlusion was used to produce anterior wall infarction. Piezoelectric crystals were placed within the ischemic region for measurement of regional wall thickness and contractile function. Two weeks later animals autologous, Di-I–labeled MSCs (6 × 10⁷) were implanted into the infarct by direct injection. Hemodynamic and functional measurements were obtained weekly until the time of sacrifice. Immunohistochemistry was used to assess MSC engraftment and myogenic differentiation.

Results. Microscopic analysis showed robust engraftment of MSCs in all treated animals. Expression of muscle-specific proteins was seen as early as 2 weeks and could be identified in all animals at sacrifice. The degree of contractile dysfunction was significantly attenuated at 4 weeks in animals implanted with MSCs (5.4% ± 2.2% versus −3.37% ± 2.7% in control). In addition, the extent of wall thinning after myocardial infarction was markedly reduced in treated animals.

Conclusions. Mesenchymal stem cells are capable of engraftment in host myocardium, demonstrate expression of muscle specific proteins, and may attenuate contractile dysfunction and pathologic thinning in this model of left ventricular wall infarction. MSC cardiomyoplasty may have significant clinical potential in attenuating the pathology associated with myocardial infarction.     

Selected ventriculoplasty for idiopathic dilated cardiomyopathy with advanced congestive heart failure: midterm results and risk analysis

Background: To treat advanced heart failure due to idiopathic dilated cardiomyopathy, surgical ventricular restoration with mitral reconstruction was conducted and evaluated. Methods: In 95 patients (81 men, mean age: 54 years), New York Heart Association class III/IV was 44/51, and 33 patients (36%) were inotropic dependent preoperatively. Mitral regurgitation (≥2+) was noted in all patients. All patients underwent left ventriculoplasty (septal anterior ventricular exclusion in 38, partial left ventriculectomy in 57) and mitral reconstruction (repair 53, replacement 42). Fifty-two patients (55%) had concomitant tricuspid repair. Intra-aortic balloon pumping and left ventricular assist device was used in 24 patients and two patients, respectively. Results: Hospital mortality was 11.6% (11 of 95), with 6.6% (5 of 76) in elective and 31.6% (6 of 19) in emergency operations. The ejection fraction and cardiac index increased from 22.3 ± 6.3% to 27.2 ± 8.0% and from 2.3 ± 0.5 ml/m²/min to 2.8 ± 0.5 ml/m²/min, respectively (p < 0.001). The endodiastolic volume index, endosystolic volume index and diastolic dimension decreased from 232.9 ± 56.1 ml/m² to 160.0 ± 49.8 ml/m², from 178.9 ± 46.7 ml/m² to 113.8 ± 44.7 ml/m² and from 82.0 ± 9.0 mm to 68.9 ± 11.6 mm, respectively (p < 0.001). Late death occurred in 27 patients with 22 cardiac deaths. The mean NYHA class was 1.7 among the survivors. One-, 3- and 5-year survival rates were 72.8%, 61.4% and 50.5%, respectively. In the 62 patients who were non-inotropic dependent preoperatively, 1-, 3-, and 5-year survival rates (81.8%, 73.7% and 62.9%) were significantly better than the inotropic-dependent group (55.3%, 37.3% and 28.0%). Patients with mitral annuloplasty showed a significantly higher 5-year survival rate than patients with mitral valve replacement (59.6% vs 43.6%) in univariate analysis. By application of the exclusion site selection method, the two different ventriculoplasty procedures did not show significant difference in survival rates. Multivariate analysis showed that preoperative inotropes and old age were significant predictors for postoperative mortality. Conclusion: The selected ventriculoplasty in combination with mitral annuloplasty is a useful option for patients with an extremely dilated left ventricle in idiopathic dilated cardiomyopathy. Surgery should be considered before inotropic dependency occurs when prior medical treatment has failed.     

Sevoflurane preserves endocardial blood flow during coronary ligation in dogs: comparison with adenosine

Background : Sevoflurane has been reported to attenuate ischaemia-induced changes of myocardial metabolism, but the mechanism is still unclear. We examined the effect of sevoflurane on regional myocardial blood flow (RMBF) in the ischaemic area and compared the flow with that in the presence of adenosine.
Method : Twenty-seven mongrel dogs were anaesthetized with fentanyl infused at the rate of 1μg.kg^-1.min^-1 throughout the experiment. Then they were divided into 4 groups; 0, 1, 2 MAC sevoflurane groups and adenosine group. Adenosine was infused into the left ventricle at a rate of 14.5 mg.kg^-1.h^-1. The left anterior descending coronary artery (LAD) was ligated for 3 min. RMBF in the endo- and epicardial layers were measured using coloured microspheres.
Results : Sevoflurane decreased both systolic and diastolic blood pressures and LV dp/dt max. Adenosine increased heart rate and coronary flow. The endocardial blood flow in 2 MAC sevoflurane was almost the same as that in the 0 MAC group. Adenosine significantly increased the myocardial blood flow. During 3-min ischaemia, endocardial blood flow in the ischaemic area under 2 MAC sevoflurane was essentially the same as those in 0 MAC and adenosine groups, though myocardial work in 2 MAC sevoflurane was lower compared with that of the other groups.
Conclusion : Preservation of endocardial blood flow related to the myocardial work during ischaemia occurred during 2 MAC sevoflurane. The decrease in LV dp/dt max induced by 2 MAC sevoflurane is one of the factors responsible for the preservation of the endocardial blood flow during ischaemia.