Extensive left atrial endoatriectomy for infective endocarditis

The technique of extensive endoatriectomy of the left atrium and reconstruction with autologous pericardium for infective endocarditis is described. Endocardium of the left atrium with vegetations was completely excised from the valvular annulus to normal endocardium, and autologous pericardium was used to reinforce the endocardial defect and to allow less tension in the closure. This technique permits complete removal of infectious lesions and facilitates mitral valve replacement reinforcing the mitral annulus.

Using electrical impedance to predict catheter-endocardial contact during RF cardiac ablation

During radio-frequency (RF) cardiac catheter ablation, there is little information to estimate the contact between the catheter tip electrode and endocardium because only the metal electrode shows up under fluoroscopy. We present a method that utilizes the electrical impedance between the catheter electrode and the dispersive electrode to predict the catheter tip electrode insertion depth into the endocardium. Since the resistivity of blood differs from the resistivity of the endocardium, the impedance increases as the catheter tip lodges deeper in the endocardium. In vitro measurements yielded the impedance-depth relations at 1, 10, 100, and 500 kHz. We predict the depth by spline curve interpolation using the obtained calibration curve. This impedance method gives reasonably accurate predicted depth. We also evaluated alternative methods, such as impedance difference and impedance ratio.

Surgical implications in the current treatment of Wolff-Parkinson-White syndrome

There are currently two different surgical approaches to the abnormal pathway, Wolff-Parkinson-White (WPW) syndrome-the endocardial (ENDO) and epicardial (EPI) techniques. In recent years, ablation of accessory pathways can be achieved by catheter-induced radiofrequency (RF) current. This study was undertaken to assess our results of surgical treatment for WPW syndrome in the current era of catheter ablation. From 1985 to 1993, 51 patients (33 male and 18 female) with WPW syndrome underwent operations for ablation of accessory pathways. Associated anomalies included Ebstein's anomaly, coronary artery disease, and tricuspid atresia. Preoperatively, 6 patients underwent unsuccessful RF catheter ablation. Fifteen (29%) patients were operated with the ENDO technique and 36 (71%) with the EPI technique. There was no early death in either group. In the immediate postoperative period 40 (78%) patients were in sinus rhythm. The electrophysiological studies revealed successful ablation of the pathway in 50 (98%) patients. On complete late follow-up (mean, 36 months) all patients were back to preoperative levels of activity. Our experience indicates that excellent results can be achieved with each of these two techniques. The left free wall accessory pathways may be ablated in a more reproducible way with the ENDO approach. The concept that surgical ablation of accessory pathways may prevent further atrial fibrillation is supported by the low incidence in this series. Operations for WPW syndrome may become indicated for RF ablation failure, when additional procedures are required. In these cases the surgical skill should be available, and this is a skill that should not be lost.

Localization of the origin of arrhythmias for ablation: from Electrocardiography to advanced endocardial mapping systems

Radiofrequency catheter ablation techniques have had a dramatic impact on the treatment of a variety of cardiac arrhythmias. However, catheter ablation of complex arrhythmias, such as intra-atrial reentry, ventricular tachycardias, and atrial fibrillation, continues to pose a major challenge. This stems from limitations of fluoroscopy and conventional catheter-based mapping techniques that limit the accurate anatomic localization of complex arrhythmogenic substrates. In this article, ECG features of complex arrhythmias are reviewed, which may facilitate the planning of an ablation procedure. The physical principles of the newly available catheter-based endocardial mapping techniques and their clinical applicability for treatment of complex arrhythmias are discussed. The role of intracardiac echocardiography to facilitate mapping and ablation is reviewed.

Electrogram-guided radiofrequency catheter ablation of atrial tissue comparison with thermometry-guide ablation: comparison with thermometry-guide ablation

OBJECTIVES

To characterize a new method for radiofrequency energy titration during ablation of atrial tissue based on reduction in electrogram amplitude. To compare this method with energy titration using electrode thermometry.

BACKGROUND

Complications associated with "anatomy-based" atrial endocardial radiofrequency ablation for suppression of atrial fibrillation may be due to flawed methods of energy titration.

METHODS

The effect of radiofrequency ablation on electrogram amplitude was characterized in a porcine model. A method for energy titration guided by electrogram amplitude reduction ("electrogram-guided") was developed and validated prospectively. Focal (smooth and trabeculated endocardial areas) and linear (smooth endocardial areas) ablation was performed comparing energy titration guided by amplitude reduction with electrode thermometry.

RESULTS

Amplitude reduction during radiofrequency application was not necessarily equal among unipolar and bipolar electrograms in the ablation region; specific patterns of reduction could be discerned, based on factors such as catheter-endocardial orientation. A criterion of >90 % reduction of unipolar and/or bipolar amplitude best predicted pathologic lesion success. Electrogram-guided focal and linear lesions in smooth areas were free of lesion complications such as endocardial charring, barotrauma, or damage to contiguous extraatrial structures. However, there was a significant incidence of insufficient lesion size, principally non-transmurality, probably due to undertitration of energy. Thermometry-guided focal and linear lesions in smooth areas were uniformly transmural but frequently evidenced complications, due to overtitration of energy. Electrogram-guided focal lesions in trabeculated areas could usually not be achieved, probably due to insufficient contact of the ablation electrode with adjacent pectinate muscles. Thermometry-guided focal lesions in trabeculated areas were smaller than electrogram-guided lesions and did not evidence complications.

CONCLUSIONS

Electrogram-guided lesions in smooth endocardial areas were uncomplicated but had a significant incidence of non-transmurality. Thermometry-guided lesions were uniformly transmural but were frequently complicated.

Open-heart endocardial radiofrequency ablation: an alternative to incisions in Maze surgery

BACKGROUND

Radiofrequency (RF) ablation produces transmural atrial lesions in vitro, and may provide advantages over incisions currently used in maze surgery. This study examines the feasibility, safety, and efficacy of open-heart endocardial RF ablation.

METHODS

Eighteen sheep (42.8 +/- 4.4 kg, age < 2 years) underwent left thoracotomy with placement of pacing leads on a pulmonary vein and the left atrial dome. On cardiopulmonary bypass, lesions were made using incision and suture or a novel RF ablation device in three sites: PVC = circle excluding pulmonary veins, IAB = line across the interatrial bundle, SVC = line from the superior to the inferior vena cava. Pacing across the PVC lesion was attempted to assess the completeness of each lesion. Preselected animals (incision n = 4, RF n = 5) were recovered and pacing attempts were repeated at 1 month. After sacrifice, hearts were sectioned and measured for lesion size and completeness.

RESULTS

RF ablation lesions took less time to create (total bypass time: RF 51.8 min vs incision 106 min, P < 0.001). No evidence of thromboembolism, atrial rupture, or coronary sinus thrombosis was seen. All PVC lesions were complete as demonstrated by the inability to pace across them. Stained sections demonstrated that acutely studied incision lesions were thinner than RF lesions; however, all lesions were transmural and similar in width at 1 month.

CONCLUSIONS

RF ablation consistently created transmural lesions more quickly than the incision and suture method and without additional complications. Endocardial RF ablation appears to be a simple and effective alternative to surgical incisions during open-heart atrial Maze procedures.

Left ventricular hamartoma associated with ventricular tachycardia

Cardiac hamartomas are a rare type of benign tumor affecting the heart. We describe a 33-year-old patient who presented with a wide complex tachycardia. Diagnostic imaging revealed a mass in the patient's left ventricular wall, near the apex of the heart. The mass was surgically resected and appeared benign. Its pathology was that of a hamartoma of mature cardiac myocytes. Postoperative electrophysiology evaluation showed no inducible focus and the patient remains alive and asymptomatic after 2 years of follow-up.

Surgical anterior ventricular endocardial restoration (SAVER) in the dilated remodeled ventricle after anterior myocardial infarction. RESTORE group. Reconstructive Endoventricular Surgery, returning Torsion Original Radius Elliptical Shape to the LV

OBJECTIVES

The goal of this study was to evaluate the safety and efficacy of surgical anterior ventricular endocardial restoration (SAVER). The procedure excludes noncontracting segments in the dilated remodeled ventricle after anterior myocardial infarction.

BACKGROUND

Anterior infarction leads to change in ventricular shape and volume. In the absence of reperfusion, dyskinesia develops. Reperfusion by thrombolysis or angioplasty leads to akinesia. Both lead to congestive heart failure by dysfunction of the remote muscle. The akinetic heart rarely undergoes surgical repair.

METHODS

A new international group of cardiologists and surgeons from 11 centers (RESTORE group) investigated the role of SAVER in patients after anterior myocardial infarction. From January 1998 to July 1999, 439 patients underwent operation and were followed for 18 months. Early outcomes of the procedure and risk factors were investigated.

RESULTS

Concomitant procedure included coronary artery bypass grafting in 89%, mitral valve (MV) repair in 22% and MV replacement in 4%. Hospital mortality was 6.6%, and few patients required mechanical support devices such as intraaortic balloon counterpulsation (7.7%), left ventricular assist device (0.5%) or extracorporeal membrane oxygenation (1.3%). Postoperatively, ejection fraction increased from 29 +/- 10.4 to 39 +/- 12.4%, and left ventricular end systolic volume index decreased from 109 +/- 71 to 69 +/- 42 ml/m2 (p < 0.005). At 18 months, survival was 89.2%. Time related survival at 18 months was 84% in the overall group and 88% among the 421 patients who had coronary artery bypass grafting or MV repair. Freedom from readmission to hospital for congestive heart failure at 18 months was 85%. Risk factors for death at any time after the operation included older age, MV replacement and lower postoperative ejection fraction.

CONCLUSIONS

Surgical anterior ventricular endocardial restoration is a safe and effective operation in the treatment of the remodeled dilated anterior ventricle after anterior myocardial infarction.

Sequential map-guided endocardial resection for ventricular tachycardia improves outcome

OBJECTIVE

Surgery for ventricular tachycardias late after myocardial infarction is frequently associated with high mortality including sudden death, and arrhythmia recurrences. We examined our results of sequential map-guided endocardial resection at normothermia in patients with ventricular tachyarrhythmias late after myocardial infarction to assess the efficacy of this technique as well as the early and long-term outcome.

METHODS

From 1995 to 1999, 22 patients underwent normothermic sequential map-guided endocardial resection for ventricular tachyarrhythmias late after myocardial infarction. Mean age was 61.2+/-6.5 years and left ventricular ejection fraction 32.5+/-8.7%. Adjunctive procedures included endoventricular patch repair of left ventricular aneurysm in 21 patients, coronary artery bypass grafting in 15 patients, and mitral valve replacement in one patient. Inducibility of ventricular tachycardia was evaluated postoperatively and patients were treated with sotalol or defibrillator implantation.

RESULTS

The intraoperative number of inducible different ventricular tachycardia morphologies was 4.0+/-2.7. More than one mapping-resection sequence was needed in ten patients. In only one patient, sustained ventricular tachycardia was induced postoperatively, sotalol was not tolerated and a defibrillator was implanted. Five patients with inducible non-sustained ventricular tachycardia became non-inducible while on sotalol. There was one operative death (4.5%). During a median follow-up of 26 (1--62) months, there were neither cardiac deaths nor ventricular tachycardia recurrences. Two patients died from non-cardiac causes. Cumulative probability of survival at 5 years was 0.83+/-0.09.

CONCLUSIONS

Sequential map-guided endocardial resection at normothermia was associated with low operative mortality and low postoperative inducibility of sustained ventricular tachycardia. The selected therapeutic approach resulted in freedom of arrhythmia recurrence and cardiac mortality including sudden death, during long-term follow-up.

Left ventricular restoration by endoventricular circular patch plasty (EVCPP)

The Endoventricular Circular Patch Plasty technique, developed to reorganize the left ventricular cavity after post-ischemic modification, is described as it has been used since 1984. Experience of more than 900 cases demonstrates the efficiency of the technique in terms of left ventricular shape, left ventricular performances and long-term clinical results. Particular attention is focused on very large asynergia with congestive heart failure.

[Percutaneous myocardial laser revascularization (PMR)]

In patients with severe angina pectoris due to coronary artery disease, who are not candidates for either percutaneous coronary angioplasty or coronary artery bypass surgery, transmyocardial laser revascularization (TMR) often leads to improvement of clinical symptoms and increased exercise capacity. One drawback of TMR is the need for surgical thoracotomy in order to gain access to the epicardial surface of the heart. Therefore, a catheter-based system has been developed, which allows creation of laser channels into the myocardium from the left ventricular cavity. Between January 1997 and November 1999, this "percutaneous myocardial laser revascularization" (PMR) has been performed in 101 patients at the Herzzentrum Leipzig. In 63 patients, only 1 region of the heart (anterior, lateral, inferior or septal) was treated with PMR, in 38 patients 2 or 3 regions were treated in 1 session. There were 12.3 +/- 4.5 (range 4 to 22) channels/region created into the myocardium. After 3 months, the majority of patients reported significant improvement of clinical symptoms (CCS class at baseline: 3.3 +/- 0.4, after 6 months: 1.6 +/- 0.8) (p < 0.001) and an increased exercise capacity (baseline: 397 +/- 125 s, after 6 months: 540 +/- 190 s) (p < 0.05). After 2 years, the majority of patients had experienced sustained clinical benefit after PMR, the CCS class after 2 years was 1.3 +/- 0.7, exercise capacity was 500 +/- 193 s. However, thallium scintigraphy failed to show increased perfusion in the PMR treated regions. The pathophysiologic mechanisms of myocardial laser revascularization is not yet understood. Most of the laser channels are found occluded after various time intervals after intervention. Other possible mechanisms include myocardial denervation or angioneogenesis after laser revascularization, however, unequivocal evidence for these theories is not yet available. In conclusion, PMR seems to be a safe and feasible new therapeutic option for patients with refractory angina pectoris due to end-stage coronary artery disease. The first results indicate improvement of clinical symptoms and increased exercise capacity, whereas evidence of increased perfusion after laser revascularization in the laser-treated regions is still lacking.

Endocardial and epicardial radiofrequency ablation in the treatment of atrial fibrillation with a new intra-operative device

OBJECTIVE

Atrial fibrillation has been a difficult problem to solve in many surgical patients, especially in those with mitral valve pathology. This study evaluates the results of endocardial and epicardial radiofrequency ablation with a new intra-operative device in the treatment of atrial fibrillation.

METHODS

We operated on 65 patients with atrial fibrillation, 58 of which had concomitant mitral surgery. Atrial fibrillation was chronic (over 1 year) in 46 patients (group A) and paroxysmal or recent onset in 12 (group B). Group C had lone atrial fibrillation (two), concomitant coronary artery disease (four) or a sarcoma (one). Bilateral pulmonary vein isolation with a new intra-operative device was performed through multiple dry lesions in all patients. Groups A and B had endocardial applications at 70 degrees C during 60 s and group C had epicardial applications at 75 degrees C. Three group C patients had epicardial applications off pump. Atrial wall biopsies were performed in nine patients from groups A and B.

RESULTS

There were no serious post-operative complications. At 1 month follow-up 54% of all patients were out of atrial fibrillation and 34% were in normal sinus rhythm with bilateral atrial contraction (Santa Crus Score 4). At 6 months follow-up, in spite of some crossover of patients among groups, similar results were obtained. The success of the procedure was 69% (Santa Crus scores 3 and 4) in mitral patients with a left atrial volume smaller than 200 cm(3). Preliminary data on the transmurality of the lesions is presented. The patients submitted to epicardial radiofrequency ablation (group C) have satisfactory results at 1 month (six out of seven were out of AF).

CONCLUSIONS

Both endocardial and epicardial RF applications are simple and quick to perform and do not pose an additional risk for most patients. Furthermore we believe that it is possible to perform bilateral epicardial radiofrequency ablation of the pulmonary veins without cardiopulmonary bypass. Further refinements of the technique are needed to assure transmurality of all lesions and better results.

Successful treatment of idiopathic left ventricular outflow tract tachycardia by catheter ablation or minimally invasive surgical cryoablation

Idiopathic right ventricular outflow tract tachycardia is readily amenable to radiofrequency catheter ablation. However, treatment modalities for left ventricular outflow tract tachycardia are not well defined. Out of 37 patients with idiopathic outflow tract tachycardia referred for catheter ablation, in 3 patients tachycardia originated from the left ventricular outflow tract. On the surface ECG, all left ventricular tachycardias exhibited an inferior axis with a predominant negative QRS complex in lead I. Heart rate during tachycardia ranged from 115 to 170 beats/min. During electrophysiological testing, 1 patient had inducible tachycardia on orciprenaline challenge, 1 patient had inducible tachycardia at baseline, and 1 patient had incessant tachycardia. In two patients, earliest ventricular activation was recorded from the endocardial left ventricular outflow tract at an anterolateral and an anterior site, respectively. A distinct high frequency spike preceded the QRS onset by 66/78 ms. Application of radiofrequency energy successfully eliminated tachycardia at these sites. In one patient, tachycardia originated from the epicardial left ventricular outflow tract. Mapping of the anterior interventricular vein revealed a fractionated low amplitude signal occurring 46 ms before QRS onset. After failure of catheter ablation from the corresponding endocardial site, successful minimally invasive surgical focal cryoablation of the epicardial target region was performed. During a follow-up period ranging from 7 to 12 months, all patients remained free of tachycardia. In conclusion, ventricular tachycardia arising from the left ventricular outflow tract may require endo- and epicardial mapping. Successful treatment is achieved by radiofrequency catheter ablation or minimally invasive surgical cryoablation.

High-resolution mapping and histologic examination of long radiofrequency lesions in canine atria

INTRODUCTION

Catheter ablation may prevent conduction of multiple atrial wavefronts and/or reduce the critical mass of atrial myocardium required to sustain fibrillation. The purpose of this study was to examine the effect of radiofrequency (RF) energy application on conduction in canine atria by performing high-density epicardial mapping and careful histologic examination of the ablation zone.

METHODS AND RESULTS

RF energy was applied to the right atrial endocardium in nine anesthetized mongrel dogs in an attempt to create a line of conduction block spanning the vertical length of a 504-channel epicardial mapping plaque. The mean length and width of the histologically determined ablation zone was 34 +/- 4 and 7.3 +/- 2.6 mm, respectively. No thrombus was present. Conduction block that spanned the mapping plaque in 6 of 9 animals was matched histologically by continuous transmural necrosis in five. In one, only a portion of the ablation zone was transmural; the remainder was wide but nontransmural. In 2 of 3 animals with conduction, a narrow region was present where continuous transmural necrosis was absent. In the other animal, conduction was present despite continuous transmural necrosis.

CONCLUSION

Conduction block usually occurred when continuous transmural necrosis was present, and conduction usually persisted when continuous transmural necrosis was absent. However, important exceptions were observed, including block when the ablation zone was wide but nontransmural, and conduction despite a thin line of continuous transmural necrosis.

Surgery for postinfarction ventricular tachycardia in the pre-implantable cardioverter defibrillator era: early and long term outcomes in 100 consecutive patients

OBJECTIVE

To report outcome following surgery for postinfarction ventricular tachycardia undertaken in patients before the use of implantable defibrillators.

DESIGN

A retrospective review, with uniform patient selection criteria and surgical and mapping strategy throughout. Complete follow up. Long term death notification by OPCS (Office of Population Censuses and Statistics) registration.

SETTING

Tertiary referral centre for arrhythmia management.

PATIENTS

100 consecutive postinfarction patients who underwent map guided endocardial resection at this hospital in the period 1981-91 for drug refractory ventricular tachyarrhythmias.

RESULTS

Emergency surgery was required for intractable arrhythmias in 28 patients, and 32 had surgery within eight weeks of infarction ("early"). Surgery comprised endocardial resections in all, aneurysmectomy in 57, cryoablations in 26, and antiarrhythmic ventriculotomies in 11. Twenty five patients died < 30 days after surgery, 21 of cardiac failure. This high mortality reflects the type of patients included in the series. Only 12 received antiarrhythmic drugs after surgery. Perioperative mortality was related to preoperative left ventricular function and the context of surgery. Mortality rates for elective surgery more than eight weeks after infarction, early surgery, emergency surgery, and early emergency surgery were 18%, 31%, 46%, and 50%, respectively. Actuarial survival rates at one, three, five, and 10 years after surgery were 66%, 62%, 57%, and 35%.

CONCLUSIONS

Surgery offers arrhythmia abolition at a risk proportional to the patient's preoperative risk of death from ventricular arrhythmias. The long term follow up results suggest a continuing role for surgery in selected patients even in the era of catheter ablation and implantable defibrillators.

Catheter mounted coaxially moveable ablation electrode for the creation of linear transmural endocardial lesions

INTRODUCTION

Use of a novel ablation catheter for the creation of linear transmural endocardial lesions, which uses a coaxially moving ablation electrode mounted on the terminal portion of a catheter shaft and able to move axially for a distance of up to 4 cm, is reported.

METHODS AND RESULTS

The coaxially moving ablation electrode is moved by a sliding mechanism in the catheter handle. The distal portion of the catheter shaft is steerable. Bipolar or unipolar electrograms can be recorded from electrodes on the catheter tip and the coaxially moving ablation. Radiofrequency (RF) current is delivered to the coaxially moving ablation electrode with thermocouple temperature control. This ablation catheter was evaluated in five (30 to 65 kg) anesthetized pigs and introduced via the venous/arterial systems into the right and left atrium (1 lesion) (using the retrograde aortic approach). The catheter was maneuvered to bring the slide range into apposition with atrial endocardium. The coaxially moving ablation electrode was deployed to the terminal portion of the catheter's slide range and then withdrawn in 2-mm steps. RF current was delivered to the coaxially moving ablation electrode at each point (maximum temperature 70 degrees C). Postmortem examination of eight endocardial linear lesions (2.2 to 4.1 cm length) was made 1 to 3 hours after creation. Histopathologic examination confirmed transmural myocyte necrosis along the length of the lesion, that included the trabeculated right atrium.

CONCLUSION

We conclude that a catheter using a moveable electrode creates continuous linear transmural lesions and could find clinical application in the therapy of a variety of reentry tachycardia mechanisms.

Identifying patients at low risk of death from cardiac failure after operation for postinfarct ventricular tachycardia

BACKGROUND

In unselected patients, cardiac failure accounted for most deaths after antiarrhythmic operation (ER) for postinfarction ventricular tachycardia (VT). This study aimed to determine whether patients at low risk of this outcome could be predicted from a retrospective analysis of variables from 100 consecutive ER patients.

METHODS

Thirteen variables suggested by other researchers as predictive of outcome were analyzed. At the time of study, ER was the only therapy available for drug refractory VT.

RESULTS

Only emergency ER, wall motion score less than 3 and Killip classification were significantly related to death from cardiac failure. The lack of correlation between emergency ER and variables of ER timing, VT less than 24 hours of ER or VT type implies that the need for emergency ER is also related to ventricular dysfunction. Multivariate analysis identified a group at particularly low risk of death with a specificity of 95%.

CONCLUSIONS

Patients at low risk of death after ER can be identified prospectively. In the implantable cardioverter defibrillator era, elective ER is best reserved for such patients. Emergency ER may still be justified in younger patients without comorbidity who will die of VT without it.

Intracardiac echocardiographic guidance during microwave catheter ablation

The purpose of this study was to explore the potential of intracardiac echocardiography in monitoring lesion formation and assisting with the assessment of ablative lesions using microwave energy. Microwave energy is a promising modality for catheter ablation. Because microwave lesions may have considerable variability in dimension, the ability to assess them may be particularly useful. One hundred twenty-five microwave lesions were created in vitro in ovine left ventricles. Correct assessment of catheter-endocardial contact was possible in virtually all cases. Intracardiac imaging always identified correctly whether or not an ablation was performed. During ablation, gas formation was observed in all instances. Sensitivity, specificity, and predictive values for identification of ablation lesions were 88% to 92%. Although the correlations with pathology for lesion dimensions were relatively poor, intracardiac imaging had a predictive accuracy of 80% to 85% to discriminate small from large lesions. Intracardiac guidance for microwave ablation is useful for verifying tissue-electrode contact, monitoring lesion formation, and localizing lesions. It is also a useful tool for the assessment of lesion size. These attributes, combined with the ability to facilitate transseptal catheterization and to identify complications such as hemopericardium, make intracardiac echocardiography a potentially useful method for guiding microwave ablation of arrhythmic foci.

[Surgical treatment of infective endocarditis]

OBJECTIVE

To summarize the experience of surgical treatment of infective endocarditis in 28 patients.

METHOD

Open heart surgery under cardiopulmonary bypass was performed in all patients: valve replacement (24), VSD repair and tricuspid annuloplasty (3), and Bentall (1) 17 mechanical and 7 homograft valves were placed.

RESULT

Two died in hospital, 4 died from infection, 1 had periprosthetic leakage and incompetence respectively. 22 survivors showed improved heart function.

CONCLUSION

Combined medication and surgical treatment is superior to antibiotic treatment in long-term survival and convalescence. Infective reccurrence, reinfection and advanced heart failure are major risk factors after operation.

Repair of septal and posterior tricuspid leaflets in Ebstein's anomaly

BACKGROUND AND AIM

In Ebstein's anomaly, the septal and posterior tricuspid leaflets are plastered to the endocardium. We postulated that tricuspid valve function could be corrected by restoring mobility of these leaflets. (Feasibility of such repair was explored by anatomical and clinical studies.)

METHODS

Ten heart specimens with Ebstein's anomaly were examined to investigate the size of the tricuspid leaflets. We operated on four patients with Ebstein's anomaly: the plastered septal and posterior leaflets were mobilized from the endocardium, the atrialized right ventricle was longitudinally plicated, and the basal attachment of the mobilized leaflets was sutured (reattached) to the valve annulus.

RESULTS

In heart specimens, approximately 40% of the total surface of the tricuspid leaflets was comprised of the septal and posterior leaflets. Clinically, all patients operated on returned to normal functional status after surgery. The mean cardiothoracic ratio on chest X-rays decreased from 0.70 to 0.55 (after surgery). Echocardiographic tricuspid regurgitation, graded from 0 to 4, decreased from 3.5 to 1.0, and tricuspid annular diameter ratio to the normal value reduced from 1.88 to 0.66. Angiographic right ventricular ejection fraction increased from 0.36 to 0.50, and end-diastolic volume ratio to the normal value decreased from 3.65 to 1.19.

CONCLUSIONS

Repair of the septal and posterior tricuspid leaflets was found to be feasible and effective as tricuspid valvuloplasty for Ebstein's anomaly.

Bipolar radiofrequency catheter ablation creates confluent lesions at larger interelectrode spacing than does unipolar ablation from two electrodes in the porcine heart

AIMS

Radiofrequency catheter ablation of atrial flutter and fibrillation may be favoured by large, elongated lesions. We compared bipolar ablation with unipolar ablation from one or two electrodes in the porcine heart.

METHODS AND RESULTS

In vitro, confluent lesions were reliably created by a 'dielectrode' catheter (energy delivered simultaneously (in parallel) from two 4 mm electrodes spaced 1 mm apart, towards an indifferent electrode), and a 'bipolar' catheter (energy delivered (in series) between two 4 mm electrodes spaced 5 mm apart). Sixteen anaesthetized pigs were randomized to standard unipolar (4), dielectrode (6) or bipolar (6) ablation. Two radiofrequency current deliveries of 30 s duration (70 degrees C) were administered to the inferior vena cava-tricuspid valve isthmus and two to the right atrial free wall in all animals. After 4 h, the lesions were examined macroscopically and histologically. Mean (SD) endocardial lesion length x width x depth measured 7.4 (2.4) x 5.4 (2.2) x 2.8 (0.8) mm in the standard unipolar mode, 10.2 (1.4) x 6.3 (0.7) x 3.3 (1.1) mm in the dielectrode mode and 14.0 (3.6) x 6.0 (1.7) x 3.8 (1.2) mm in the bipolar mode. Thus lesion length increased significantly through the three groups (P < 0.001), while width and depth did not.

CONCLUSION

Both dielectrode and bipolar ablation were feasible in porcine right atrial ablation, and created longer lesions than the standard unipolar mode. By allowing a larger interelectrode distance, bipolar ablation created the longest lesions and may be favourable when linear lesions are necessary.

[Clinical expression of papillary fibroelastoma. Apropos of a case]

The authors review the literature of the clinical features of papillary fibroelastomas in the light of a new case. These benign tumours of the endocardium may be distinguished from Lambl's vegetations by their site and size. Some workers suggest that they correspond to giant Lambl's vegetation and could be a form of "aging" of the valvular endocardium. Nevertheless, Lambl's vegetations are always present after 10 years of age but the papillary fibroelastoma is rarely detected by echocardiography and there have been few case reports. They are essentially cardiac valve tumours (73% of valvular tumours) and may give rise to serious clinical symptoms, sudden death by migration or coronary obstruction, systemic embolism, especially from left heart lesions. However, they can be situated at any point of the endocardium. The diagnosis of a valvular or an endocardial tumour is based on echocardiography which, though not always accurate, gives a better aetiological diagnosis. In cases of symptomatic tumours, surgery (usually simple ablation) is indicated with a low operative risk and cure of symptoms. Tumours discovered by chance pose very difficult problems of management and may lead to diagnostic or preventive surgery.

Transcatheter endomyocardial laser revascularization: a feasibility test

By means of a special catheter system, a total of 76 endomyocardial laser channels were percutaneously produced in a controllable manner at selected sites in 6 beating canine hearts. Acute patency of channels (length = 4-11 mm, diameter = 0.5-1.2 mm) was documented angioscopically and histologically. This minimally invasive method might be useful for revascularising certain patients with ischemic heart disease without resorting to open-chest surgery.

Improvement of left ventricular function and cardiovascular neural control after endoventriculoplasty and myocardial revascularization

OBJECTIVE

To investigate the effects of endoventriculoplasty (EVP) and myocardial revascularization on left ventricular function and on sympathovagal balance modulating sinus node and vasomotor activity, we studied patients with left anterior, septal or anteroseptal ventricular aneurysm, before and after surgery. It has been demonstrated that, compared to the standard aneurismectomy, EVP associated with coronary grafting has a lower operative mortality and improves ventricular function, clinical status and prognosis.

METHODS

We collected pre- and post-operative echocardiographic and angiographic data to determine morphological and hemodynamic changes. The pre- and post-operative neural cardiovascular control was assessed by power spectrum analysis of heart rate and systolic arterial pressure (SAP) variabilities during rest and tilt.

RESULTS

As expected, post-operative ventricular function improved significantly: ejection fraction increased from 33 +/- 2 to 46 +/- 3% (p < 0.01) when assessed by echocardiography and from 40 +/- 4 to 55 +/- 5% (p < 0.01) when assessed by angiography; left ventricular end-diastolic pressure fell from 22 +/- 3 to 13 +/- 2 mmHg (p < 0.05). Pre-operatively sympathovagal balance responsiveness was blunted: tilt test did not induce, in respect to resting values, any significant change in low frequency (LFRR) and high frequency (HFRR) components of RR variability (in normalized units, n.u.) and in LFSAP. Post-operatively, tilt induced significant changes in LFRR and HFRR (in n.u.), in LF/HF ratio and LFSAP in respect to resting values. The pre- and post-operative percent differences--delta%--, from rest to tilt, of LFRR, HFRR, LF/HF and LFSAP were also significantly different (p < 0.01, p < 0.05, p < 0.05, p < 0.05). In addition, we compared data obtained from survivors and non-survivors (6 out of 19 patients died within 4 months because of heart failure). Non-survivors were characterized by significantly lower RR variance (184 +/- 80 vs. 1193 +/- 309 ms2 at rest, 196 +/- 87 vs. 546 +/- 104 ms2 during tilt, p < 0.05) and lower LFRR (15 +/- 7 vs. 61 +/- 6 at rest, 23 +/- 10 vs. 58 +/- 6 during tilt, in n.u., p < 0.01).

CONCLUSIONS

(1) The improvement of ventricular function induced by EVP and myocardial revascularization is accompanied by a restored capability to oscillate of cardiovascular neural regulatory mechanisms; (2) the drastic reduction of variance and LF component from RR variability seems to be associated with an ominous outcome.

Superior-septal approach for transmitral mapping and cryoablation of ventricular tachycardia

A superior-septal approach was used for mapping and cryoablation of the left ventricular endocardium over the mitral annulus in a patient with ventricular tachycardia associated with an inferior myocardial infarction without a ventricular aneurysm. This approach provides an excellent view of the mitral valve, and allows safe, adequate mapping and cryoablation of the left ventricular endocardium without the necessity of a ventriculotomy.

Guidance of radiofrequency endocardial ablation with real-time three-dimensional magnetic navigation system

BACKGROUND

Ablation therapy for certain arrhythmias requires the formation of complex lesions based on electrical and anatomic mapping. We tested the accuracy and reproducibility of a nonfluoroscopic mapping and navigation (NFM) system to guide delivery of radiofrequency (RF) energy in the right atrium (RA) of swine.

METHODS AND RESULTS

The NFM system uses an ultralow magnetic field to measure the real-time three-dimensional (3D) location of the tip of the locatable catheter. While in stable contact with the endocardium, between 30 and 40 consecutive tip locations were sampled and used for the 3D reconstruction of the RA geometry. The location of the catheter tip was presented in real time, superimposed over the RA geometry. We selected a point on the 3D reconstruction and delivered RF energy to that site via the tip of the locatable catheter. The catheter was then completely withdrawn and renavigated twice to the same point, at which RF energy was delivered again. At autopsy, the distance between the centers of the three ablation points (mean+/-SEM) was 2.3+/-0.5 mm (n=27). Similarly, we used the NFM system to guide the generation of linear lesions. The measured length of the linear lesions on the NFM 3D view was close to the actual lesion length measured at autopsy (correlation coefficient, .96; P=.002; n=6). Furthermore, the location, shape, and continuity of the linear lesions corresponded to the autopsy findings.

CONCLUSIONS

We conclude that the NFM system can guide the application of RF energy without the use of fluoroscopy in a highly accurate and reproducible manner.

Posttraumatic left ventricular pseudoaneurysm due to intramyocardial dissecting hematoma

A left ventricular aneurysm can develop in patients sustaining blunt chest injury. This condition has been attributed to myocardial contusion or to a direct vascular lesion leading to myocardial necrosis. We report the case of a pseudoaneurysm resulting from myocardial dissection beginning from a small tear in the endocardial wall. Successful surgical exclusion of the pseudoaneurysm by endoaneurysmal patch closure of the communications between the aneurysm and the left ventricular cavity is described.

The treatment of refractory ischemic ventricular tachycardia by endoventricular patch plasty reconstruction of the left ventricle

Although the endoventricular patch plasty technique was originally developed to improve the functional status of the left ventricle following resection of an aneurysm, it became apparent early on in our experience that the technique also cured most cases of ventricular tachycardia associated with these aneurysms. As a result, we began to include as a part of our preoperative work-up an electrophysiology study in which we attempted to induce ventricular tachycardia even if it had not occurred spontaneously. Using our standard surgical approach, plus the use of cryotherapy, we have now operated on 106 patients with either spontaneous or inducible ventricular tachycardia preoperatively in association with ventricular dyskinesia or akinesia. The operative mortality in this series of patients was 7.5%. Postoperatively, ventricular tachycardia could not be induced in 92% of the survivors and only 2 patients have had episodes of spontaneous ventricular tachycardia. Because this technique does not require any intraoperative electrophysiological mapping, we believe this to be an excellent surgical approach for patients with refractory ischemic ventricular tachycardia.

Cine-MRI-aided endomyocardectomy in idiopathic hypereosinophilic syndrome

The idiopathic hypereosinophilic syndrome is a leukoproliferative disorder marked by a predilection to damage specific organs, including the heart. This report describes a patient with extensive endocardial fibrosis accompanying this syndrome. Right ventricular endomyocardectomy with preservation of the tricuspid valve was performed. The procedure was aided by cine-magnetic resonance imaging for preoperative assessment and follow-up of surgical results.

Atrial flutter: lessons from surgical interventions (musing on atrial flutter mechanism)

We report our experience with seven patients who underwent direct surgical ablation of problematic common flutter. Intraoperative mapping was obtained in four patients. Surgical techniques varied over time. A circular incision of the right atrium was performed in the first patient. Two patients had epicardial cryoablation of the isthmus between the inferior vena cava and the tricuspid valve annulus. Four patients had extensive endocardial cryoablation of the isthmus. There were no immediate postoperative complications. One patient had atrial fibrillation 2 months postoperatively and underwent a corridor operation 1 year later. The other six patients are free of arrhythmias without antiarrhythmic drugs. Surgical ablation confirmed that the common form of atrial flutter is associated with a right atrial macroreentrant circuit. One of our intraoperative endocardial maps suggested that variant reentrant circuits can be associated with variant forms of flutter.

Transcatheter subendocardial infusion. A novel technique for mapping and ablation of ventricular myocardium

BACKGROUND

Catheter ablation with radiofrequency energy is feasible in a limited subset of patients with ventricular tachycardia. The purpose of this study was to evaluate a technique for mapping and ablation of ventricular myocardium with the use of transcatheter subendocardial infusion.

METHODS AND RESULTS

A needle-tipped deflectable electrode catheter was used to deliver reagents to endocardial target sites. This was equipped with two central lumens to allow sequential administration of mapping and ablation injectants with minimal admixture. The mapping injectant consisted of a mixture of lidocaine, iohexal, and glycerin; the ablation injectant contained ethanol, iohexal, and glycerin. Infusion of the mapping injectant (1 cm3 over 3 or 5 seconds, n = 14) produced a stain on fluoroscopy and increased local capture threshold by 61%. No lesions resulted from mapping infusions. Infusion of the ethanol-containing injectant (n = 48) produced discrete lesions, with a mean volume ranging from 0.6 to 1.5 cm3. There was a direct relationship between infusion volume, infusion duration, and resultant lesion volume. Fibrosis in a region of healed myocardial infarction did not impair diffusion of the injectant or affect lesion dimensions. Microscopic analysis of chronic lesions showed a sharply demarcated border zone between fibrotic and normal myocardium.

CONCLUSIONS

Transcatheter subendocardial infusion can be used to reversibly impair local excitability and mark an injection site fluoroscopically. Subendocardial injection of ethanol can predictably ablate a large volume of ventricular myocardium. Additional study of this system in an arrhythmia model will help to define its potential for mapping and ablation of hypotensive ventricular tachycardia.

In vitro quantification of radiofrequency ablation lesion size using intracardiac echocardiography in dogs

The results of this study demonstrate that real-time ultrasonic evaluation of radiofrequency lesion creation and lesion size is feasible.

Incidence of ICD lead related complications during long-term follow-up: comparison of epicardial and endocardial electrode systems

The aim of this study was to evaluate the long-term stability of epicardial and endocardial lead systems for third-generation cardioverter defibrillators (ICDs) and to assess the usefulness of diagnostic tools. One hundred forty patients with 61 epicardial (43.6%) and 79 nonthoracotomy systems (56.4%) were followed for 25 +/- 19 months. A total of 18 (12.9%) lead related complications were documented. Complications of epicardial systems were detected in 10 patients (16.4%) during a follow-up time of 36 +/- 8 months: crinkling of patch electrodes in 6 patients (9.8%), insulation breakage of sensing electrodes in 2 patients (3.3%), and adapter defect in 2 patients (3.3%). Eight of the patients (10.1%) with transvenous-subcutaneous systems had lead related complications during a 13 +/- 6 months follow-up: fracture of the subcutaneous patch lead in 2 patients (2.5%), dislodgement of the right ventricular lead in 2 patients (2.5%), dislodgement of the superior vena cava lead in 2 patients (2.5%), insulation breakage of sensing electrodes in 1 patient (1.3%), and connector defect in 1 patient (1.3%). There was no significant difference in the incidence of lead related complications between epicardial and endocardial systems (P > 0.05). Fractures, dislodgements, and crinklings were documented within the first 8 +/- 5 months by regular chest X ray. Defects of insulation, adapter, or connector were detected 22 +/- 10 months after implantation and were associated with delivery of multiple inappropriate ICD therapies. An operative lead revision was indicated for 4 epicardial (6.6%) and 6 endocardial (7.6%) lead systems.

CONCLUSIONS

Endocardial lead systems offer a similar long-term stability as compared to epicardial lead systems. Chest X ray is the most useful tool to detect lead fracture, dislodgment, and patch crinkling. Marker recordings or real-time electrograms have not been helpful in this series to identify patients with suspected lead defects prior to the experience of inappropriate ICD discharges.

Postinfarction ventricular septal rupture: repair by endocardial patch with infarct exclusion

A novel operative technique for postinfarction ventricular septal defect has been used in 44 consecutive patients. The operation consists of excluding rather than excising the infarcted septum and ventricular walls. This is accomplished by performance of a left ventriculotomy through the infarcted muscle and securing a glutaraldehyde-fixed bovine pericardium patch to the endocardium of the left ventricle all around the infarcted myocardium. The ventriculotomy is simply closed over the pericardial patch. There were 21 men and 23 women whose mean age was 69 +/- 7 years. Twenty-nine patients were in cardiogenic shock at the time of operation. All patients had Doppler echocardiography and coronary angiography before operation. All but two patients were operated on during the acute phase of the myocardial infarction. There were six operative deaths. Postoperative complications included renal failure in 10 patients and respiratory failure in 18. Severe right ventricular dysfunction was the only independent predictor of operative mortality. Patients have been followed up for a mean of 40 +/- 34 months. There have been six late deaths and three of these were because of cardiac problems. The actuarial survival at 6 years was 66% +/- 7%. Only one patient had a small residual ventricular septal defect. Late postoperative assessment of ventricular function by echocardiography revealed that most patients had normal or mild impairment of right ventricular function and mild or moderate impairment of left ventricular function. Repair of acute postinfarction ventricular septal defect by endocardial patch with infarct exclusion of the left ventricule probably avoids additional damage to the right ventricle, remodels the acutely infarcted left ventricle, and enhances survival.

A comparative study of radiofrequency ablation in unipolar and bipolar fashion

In this study we compared the effects of radiofrequency (RF) energy applied to the swine endocardium in a unipolar fashion and in a bipolar one with two different interelectrode distances (5 mm, 10 mm). RF energy (500 kHz) delivered to the swine endocardium was divided into eight categories: 100 J, 101-200 J, 201-300 J, 301-400 J, 401-500 J, 501-600 J, 601-1000 J, and > 1000 J. The results showed that when RF energy was applied in a bipolar fashion, the lesions involved the catheter/tissue interface and partly the interelectrode spacing, while in a unipolar fashion. They were found in the catheter/tissue interface only. At any energy level, there were no statistically significant differences in lesion depths among all the three fashions, and the lesion surface areas produced by the bipolar fashion (with 5 mm or 10 mm interelectrode spacing) were all greater than those by the unipolar fashion (P < 0.05). When the delivered energy was under 500 joules, a greater lesion surface area was found in 5 mm bipolar fashion than in 10mm bipolar fashion (P < 0.05), while energy exceeded 500 joules, the differences in the lesion surface areas were no longer significant between these two bipolar fashions.

Effect of subendocardial resection on sinus rhythm endocardial electrogram abnormalities

BACKGROUND

Patients with sustained ventricular tachycardia after acute myocardial infarction frequently have characteristic abnormalities of left ventricular endocardial electrical activity, including fractionated (prolonged, multicomponent, low-amplitude), split (having discrete widely separated deflections), and late (extending after the end of the QRS complex) electrograms. The exact cause and source of these electrograms are not clear.

METHODS AND RESULTS

In this study, endocardial electrograms from 18 patients were recorded with a 20-electrode array from the same area immediately before and immediately after resection of subendocardial tissue at the time of surgery for ventricular tachycardia. Electrograms could be compared before and after resection from 298 of 360 (83%) of the electrodes. Before resection, split electrograms were present in 130 (44%) and late components in 81 (27%) of the recordings. Recordings made after resection showed fewer abnormalities, including complete absence of split electrograms as well as all previously recorded late components (P < .02). Mean electrogram amplitude increased from 0.5 +/- 0.8 to 1.0 +/- 1.6 mV (P < .0001) because of removal of the attenuating effect of endocardial scar; mean duration decreased from 112 +/- 38 to 65 +/- 27 ms (P < .0001) mainly because of loss of late and split components. Overall electrogram contour was very similar aside from these changes.

CONCLUSIONS

These data show that (1) some of the signal recorded on the endocardial surface is derived from deeper tissue layers and (2) split and late electrogram components appear to be generated by cells in the superficial endocardial layers, since they are eradicated by removal of this tissue. These findings correspond well with previous histological studies of resection specimens that show bundles of surviving muscle cells separated by layers of dense scar that act as an insulator.

Deringing procedure for congenital pulmonary vein stenosis

We operated on a 14-year-old boy who had an echocardiographic diagnosis of ventricular septal defect. At surgery we found, in addition, an anomalous and obstructive intraventricular muscle bundle. Detection of a continuous thrill over the right pulmonary veins, prior to cardiopulmonary bypass, led to exploration of the left atrium. The ostia of the right superior and inferior pulmonary veins were impeded by circumferential membranous rings of endocardium with central stenotic openings. Excision of these annular rings relieved the obstruction. The left lung was drained by a long intrapericardial common venous channel that entered the left atrium through a stenotic ostium; excision of an annular ridge of endocardium restored normal flow. The patient remains asymptomatic after 23 months. The case is reported for the new deringing technique and the rarity of successful correction of congenital pulmonary vein stenosis.

Intraoperative mapping is not necessary for VT surgery

Surgical ablation of ventricular tachycardia is generally guided by the results of pre- and intraoperative cardiac mapping. However, in certain situations intraoperative cardiac mapping may not be possible and, therefore, surgery has to be based on information obtained preoperatively. This raises the question whether intraoperative mapping is necessary for the success of this approach. We describe our experience with encircling endocardial cryoablation for ischemic VT and examine the contribution of intraoperative mapping for this procedure. Thirty-three patients with inducible VT refractory to medical therapy and a well defined anatomic scar were considered for surgery. All patients underwent baseline electrophysiology study and intraoperative mapping was attempted during normothermic cardiopulmonary bypass. In 14 patients, VT was inducible intraoperatively (Group 1) and surgical ablation was guided by this information, whereas in 19 patients, VT could not be mapped for various reasons (Group 2). Reasons for failure to obtain intraoperative map included noninducibility (3), nonsustained VT (8), polymorphic VT (4), VF (3), and incessant VT with hemodynamic collapse and cardiac arrest (1). The two groups did not differ with respect to age, location of myocardial infarction, or preoperative left ventricular ejection fraction. The operative procedures were similar in the two groups with respect to aortic cross clamp time, cardiopulmonary bypass time, number of cryoablation lesions, concomitant revascularization, aneurysmectomy, and ICD implantation. Encircling endocardial cryoablation was performed in 32 patients and one patient underwent partial right ventricular free wall disconnection (RV infarct). Thirteen patients underwent concomitant coronary artery bypass grafting (5 in Group 1 and 8 in group 2). One patient had prophylactic ICD patches (Group 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Encircling endocardial cryoablation for ventricular tachycardia after myocardial infarction: experience with 33 patients

Encircling endocardial cryoablation, consisting of circumferential cryoablation of the infarct scar, can be curative in selected patients with ventricular tachycardia (VT). We describe our experience with and long-term outcome in 33 patients undergoing this procedure. The interval between myocardial infarction and the onset of tachycardia varied from 2 weeks to 22 years (mean 38 +/- 63 months and median 3 months). All patients had a left ventricular aneurysm (anterior in 20, posterior in 12, and lateral in 1) and significant coronary artery disease. Fourteen patients had clinical evidence of heart failure preoperatively. Twenty-eight patients had sustained monomorphic VT (incessant in 3); 3 had polymorphic or nonsustained tachycardia; 2 had primary ventricular fibrillation; and 1 had associated Wolff-Parkinson-White syndrome. Surgery was undertaken after failed drug therapy and consideration of left ventricular anatomy and function. At surgery, 32 patients had encircling endocardial cryoablation, and 1 patient had partial right ventricular free-wall disconnection (right ventricular infarct). Thirteen patients underwent concomitant coronary artery bypass grafting. An implantable cardioverter defibrillator (ICD) was implanted in 2 patients and prophylactic ICD patches in 1. One patient died postoperatively; 3 had recurrent VT perioperatively; 1 was treated with amiodarone; and 2 had ICD implantation. During long-term follow-up (mean 5 years), all patients who were free of tachycardia at discharge remained alive and free of arrhythmias or syncope. The patient receiving amiodarone sustained a cardiac arrest subsequently and received an ICD implant. One patient with an ICD continued to receive appropriate shocks frequently and died 2 years after surgery. Nine patients had congestive heart failure postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

A computer simulation of radio-frequency ablation of the endocardium

A computer simulation of radio-frequency (RF) ablation of the endocardium is performed. The objective is to quantify some of the parameters affecting lesion growth, and to obtain theoretical data which can be used as a guide to maximize the lesions obtained with the procedure. The model under consideration consists of a block of heart tissue with the catheter electrode making contact at a right angle on one side (endocardium) and a large grounded electrode on the other side. An RF electrical current flows between the electrodes, heating the tissue. The simulations provide information on the time evolution of the tissue temperature, lesion dimension and tissue resistance. A first set of calculations is based on an applied RF voltage that maintains the maximum tissue temperature at 100 degrees C. The results reveal that: 1) the lesions achievable by RF ablation are considerably larger than those obtained with a hot-tip catheter of the same size; 2) increasing the electrode radius enlarges the lesion because of an associated increase in contact surface area; 3) an increase in electrode length also enlarges the lesion because of the larger convective losses to the blood flow; 4) a large difference in temperature may exist between the electrode and the tissue because of the cooling effect of the blood flow; and 5) the lesions grow as long as power is applied. Other simulations in which the RF voltage is constant show that the lesions can be enlarged by lowering the applied voltage while increasing the duration. Agreement and discrepancies between the simulations and reported experimental results are identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Transatrial lead placement for endocardial pacing in children

Transvenous placement of endocardial leads in children may be difficult due to restrictions and complications of vascular access. We have placed endocardial leads from a transatrial approach in 5 children with various cardiac malformations. The usual surgical approach involved an anterolateral thoracotomy and, under fluoroscopic guidance, passage of the lead tip directly through the right atrial wall and across the tricuspid valve to the apex of the right ventricle. At a mean follow-up time of 23.2 months (range, 12.0 to 27.9 months), all patients have low thresholds for myocardial capture, and there have been no complications. We conclude that placement of endocardial leads by a transatrial approach provides an excellent alternative to an epicardial system in children destined for lifelong pacing.

The long-term outcome of visually directed subendocardial resection in patients without inducible or mappable ventricular tachycardia at the time of surgery

INTRODUCTION

In prior studies, 20% to 40% of patients undergoing subendocardial resection (SER) for ventricular tachycardia (VT) could not be mapped intraoperatively because the VT was either noninducible or nonmappable following the ventriculotomy. The optimal surgical approach to such patients is not known.

METHODS AND RESULTS

In this study, we retrospectively compared the long-term survival and functional outcome of 29 patients with VT and prior myocardial infarction who were either noninducible or nonmappable intraoperatively and underwent a visually directed extended SER. These results were then compared to 85 patients who had inducible VT intraoperatively and underwent a map-guided sequential SER. The two patient groups had different clinical characteristics. The visually directed cohort was more likely to be male, experienced fewer VT episodes before surgery, and underwent fewer antiarrhythmic drug trials prior to resection. In addition, the visually directed group had slower VT induced at a preoperative electrophysiologic study and was less likely to present to the operating room in shock or incessant VT than the map-guided group. The postoperative VT clinical recurrence or inducibility rate was 14% in both the visually directed and map-guided groups. The long-term actuarial survival at 1, 3, and 5 years was 93%, 86%, and 75%, respectively, in the visually directed group, compared to 77%, 58%, and 58%, respectively, in the map-guided group (P = 0.06). There were no documented nonfatal recurrences of VT in either group. At 24 months following surgery, 77% of patients who had a visually directed SER were in New York Heart Association Functional Class I or II, compared to 46% of patients who underwent a map-guided SER (P < 0.05).

CONCLUSION

In patients with VT and prior myocardial infarction, the inability to induce or map the VT in the operating room does not preclude a favorable long-term outcome if a visually directed extended SER technique is used.

Results of nonguided subtotal endocardiectomy associated with left ventricular reconstruction in patients with ischemic ventricular arrhythmias

We analyzed the effects of nonguided endocardiectomy in patients with ischemic ventricular arrhythmias who underwent reconstructive operations for postinfarction left ventricular aneurysm. A total of 106 patients among 287 consecutive patients had spontaneous or inducible ventricular tachycardia (49 spontaneous and 57 inducible). Cryotherapy was done in 67 patients and coronary revascularization was done in 98%. Patients underwent complete hemodynamic study including programmed ventricular stimulation before and early after operation. Thirty-seven patients underwent hemodynamic evaluation after 1 year. The hospital mortality rate was 7.5%. At early and late studies the mean ejection fraction was significantly increased. Ventricular tachycardia was no longer inducible in 92% of patients after operation; only two patients had spontaneous ventricular tachycardia early after operation. At late study 10.8% of patients had inducible ventricular tachycardia and no spontaneous ventricular tachycardia was documented. All surviving patients had clinical follow-up (mean 21.3 months, range 2 to 64 months). There were eight late deaths and no episodes of ventricular tachycardia or syncope that necessitated hospitalization. In conclusion, nonguided, extended endocardiectomy associated with left ventricular reconstruction is safe and effective in curing ischemic spontaneous and inducible ventricular tachycardia.

Intraoperative laser photocoagulation of ventricular tachycardia

Mapping-guided laser photocoagulation was used as an intraoperative technique to treat ventricular tachycardia (VT) in patients with ischemic heart disease. Laser irradiation was delivered during VT to sites identified with local diastolic activation or, if VT was not inducible, to sites identified with delayed potentials during sinus rhythm. The group consisted of 12 male and two female patients who ranged in age from 41 to 74 years (mean, 59.9 years). All of the patients had experienced myocardial infarction before surgery; in eight cases myocardial infarction was associated with an anterior wall aneurysm, and in one case it was associated with a posterior wall aneurysm. Identified sites for laser irradiation were restricted to the endocardium in only four patients, whereas six patients showed endocardial and epicardial foci and four of them without circumscript aneurysm were subjected only to epicardial laser photocoagulation. Resection of an aneurysm was performed in nine patients, and additional bypass grafting (one to four grafts) has been performed in 10 patients. There were two perioperative deaths. Laser photocoagulation has proved to be an efficacious method for the surgical treatment of VT. It gives access to epicardial sites and, in particular, allows limited surgery in patients with restricted left ventricular function and no circumscript aneurysm.