[Combined endocardial and epicardial radiofrequency modified Maze procedure in the treatment of atrial fibrillation]

OBJECTIVE

To evaluate the effectiveness of the combined endocardial and epicardial saline-irrigated radiofrequency modified maze procedure for the treatment of atrial fibrillation (AF).

METHODS

During a period of 3 years, 295 patients with AF having concomitant cardiac surgery underwent the procedure. Patients underwent either the endocardial and epicardial group (n=185) or the endocardial group (n=110) radiofrequency ablation. There were 124 males, 171 females with a mean age of (52 +/- 11) year old. Mean duration of preoperative AF was 36 +/- 43 months. And about 90.8 percent valve pathology was rheumatic. Valve operation was performed in 289 patients, coronary artery bypass graft surgery in 19 patients and congenital heart disease operation in 6 patients respectively. Follow-up for the whole patients ranged from 3 to 47 months (mean 28 +/- 5 months).

RESULTS

Ten patients died postoperatively (3.4%). Four patients died of low cardiac output, five patients died of multisystem and organ failure, one patient died of cerebral hernia. There were 2 patients died of nerves system complication during follow-up. At the end of the procedure 228 patients (77.3%) were sinus rhythm, including 78 patients (70.9%) in endocardial group while 150 patients (81.1%) in endocardial and epicardial group (P<0.05). At late follow-up, 191 of 259 patients (73.7%) were in stable sinus rhythm. Sinus rhythm was present in 64 patients (66.0%) in endocardial group while 127 patients (78.4%) in endocardial and epicardial group (P<0.05). Histopathology of the endocardial group revealed foci coagulative necrosis was limited to the endocardial side. While endocardial and epicardial ablation had full-thickness alteration of atrial tissue besides ill defined borders and inflammatory cell infiltration.

CONCLUSIONS

Combined endocardial and epicardial saline-irrigated radiofrequency modified maze procedure was performed safely and efficiently. And it restored sinus rhythm better than endocardial ablation only.

Impact of left atrial size reduction and endocardial radiofrequency ablation on continuous atrial fibrillation in patients undergoing concomitant cardiac surgery: three-year results

BACKGROUND AND AIM OF THE STUDY

The study aim was to evaluate the efficacy of left atrial (LA) size reduction combined with radiofrequency (RF) ablation in the treatment of continuous atrial fibrillation (AF), by comparative analysis of the outcomes of patients undergoing RF ablation with and without LA size reduction.

METHODS

A total of 46 patients with continuous AF and cardiac disease underwent cardiac surgery and RF ablation alone (group I, n = 20) or combined with LA size reduction (group II, n = 26). Patients were followed for three years postoperatively, with evaluation of cardiac rhythm, neurological complications, LA size (by echocardiography) and atrial contractility.

RESULTS

At three years after surgery, sinus rhythm (SR) was restored in 61.1% and 70% of patients in groups I and II, respectively. Mean LA diameter was reduced from 60 +/- 15 mm to 57 +/- 5 mm in group I, and from 69 +/- 19 mm to 55 +/- 6 mm in group II. The overall three-year survival was 90% in group I, and 88.5% in group II. Three-year freedom from stroke was 88.9% and 86.2% in groups I and II, respectively. Two patients in each group received transvenous permanent pacemaker implantation. Atrial contractility was recovered in all patients with stable SR.

CONCLUSION

LA size reduction improves SR conversion rate after RF ablation for continuous AF in patients undergoing concomitant cardiac surgery.

[Surgical methods of removing indwelling endocardial electrodes in clinical practice]

The article reflects experience in surgical removal of indwelling endocardial electrodes using minithoracotomy and no cardiopulmonary bypass. A modern classification of indications to removal of indwelling endocardial electrodes is given. The results of analysis of long-term results of surgical treatment are given too.

Laser Energy Source in Surgical Atrial Fibrillation Ablation: Preclinical Experience

PURPOSE

The purpose of this study was to evaluate diffusing tip laser energy in surgical atrial fibrillation ablation using a canine model. This is the first report to describe the pathological and histological findings using a laser energy source.

DESCRIPTION

The surgical atrial fibrillation ablation procedure was performed through a left atriotomy; the pulmonary veins were encircled in 16 dogs using a diode laser (980 nm) with a diffusing tip that permits linear ablation perpendicular to the fiber direction. Lesion durations were 45 seconds with a power density of 3.8 or 4.5 W/cm. Six animals were allowed to survive 4 hours after the procedure, with the remainder sacrificed at 1 week (n = 1), 4 weeks (n = 3), and 6 weeks (n = 6). Electrophysiologic effectiveness was judged using unipolar or bipolar pacing from the pulmonary veins after attempting isolation. Hearts were harvested for histologic examination using standard trichrome staining.

EVALUATION

All animals tolerated the procedure. The animals required an average of 5.6 +/- 0.82 lesions to complete the procedure. All animals had confirmed isolation of the pulmonary veins as judged by unipolar or bipolar pacing, and this isolation persisted in those animals that were allowed to survive. Pathology revealed all lesions to be transmural with an average tissue thickness of 3.62 +/- 1.50 mm (range, 0.95 mm to 7.06 mm).

CONCLUSIONS

Diffusing tip laser technology reproducibly makes rapid, transmural, and electrophysiologically effective atrial lesions.

Surgical repair of multiple muscular ventricular septal defects: the role of re-endocardialization strategy

OBJECTIVE

Surgical repair of multiple muscular ventricular septal defects (Swiss cheese septum) is associated with important morbidity and mortality. We sought to examine factors associated with permanent heart block, early mortality, and time-related survival. Additionally, we evaluated a new approach, transatrial re-endocardialization of interventricular septum, to mitigate risk.

METHODS

One hundred sixteen patients underwent surgery for multiple muscular ventricular septal defects (1982-2005), of whom 64 (55%) had associated cardiac anomalies. Twenty-seven consecutive patients (median age 0.54 years, range 15 days-7.2 years) underwent transatrial re-endocardialization (2002-2005). Forty-four percent had Swiss cheese septum (>4 defects). Multivariable regression analysis determined risk factors for pacemaker and survival.

RESULTS

Operative mortality for the entire cohort was 9%. Risk factors for death were double-outlet right ventricle (odds ratio 44.7, P = .003), ventriculotomy (odds ratio 6.4, P = .03), and fewer multiple muscular ventricular septal defects repaired (odds ratio 4.7/defect, P = .04). Era mortalities differed: 16% for 1982 through 1990, 13% for 1990 through 1998, and 0% for 1999 through 2005, P = .006). Fourteen patients (12%) required a pacemaker. Time-related survivals at 1 and 10 years were 90% +/- 3% and 82% +/- 5%. Risk factors for death were double-outlet right ventricle (hazard ratio 8.3, P = .02) and longer bypass (hazard ratio 1.02/min, P = .02). In 27 re-endocardialization patients, a combined closure strategy to close 184 defects were applied: transatrial re-endocardialization (median 5, range 2-21), patch (median 1, range 0-4), and device (range 0-1). Post-repair ventricular function was good in 25 of 27 patients. The median number of residual defects was 1.5 (range 0-3), and median residual jet width on color Doppler was 2.3 mm (range 0-4.2 mm). One child required a pacemaker. There were no early or late deaths.

CONCLUSIONS

Outcome of surgical repair of multiple muscular ventricular septal defects (Swiss cheese septum) has improved. Transatrial re-endocardialization strategy enables early complete or nearly complete obliteration of multiple muscular ventricular septal defects with minimal residual lesions (shunt, ventricular dysfunction). Long cardiopulmonary bypass duration is well tolerated. The incidence of permanent heart block has improved. Early echocardiographic and clinical outcomes are promising.

Novel Robotic Catheter Remote Control System: Feasibility and Safety of Transseptal Puncture and Endocardial Catheter Navigation

OBJECTIVES

The aims of this study were to demonstrate the safety and the feasibility of the robotic catheter remote control system (CCS) in endocardial navigation in all cardiac chambers, as well as facilitation of the transseptal puncture.

BACKGROUND

CCS has been developed to facilitate control and precise positioning of catheters within the cardiovascular system.

METHODS

CCS consists of a remote catheter manipulator, a set up joint, a physician workstation, and a steerable guide catheter (SGC) and sheath. A conventional 4-mm tip catheter was inserted through the SGC to perform mapping of five predefined targets in each cardiac chamber. Seven mongrel dogs were used in this study. Intracardiac echocardiography and three-dimensional (3-D) electroanatomical mapping were integrated with CCS to facilitate catheter manipulation and to guide transseptal puncture. The time to complete the transseptal puncture and the time to complete access to the predefined targets in each cardiac chamber were measured. Gross and microscopic examinations of the accessed and ablation sites were performed to evaluate safety.

RESULTS

Transseptal puncture was performed successfully in all animals with a mean time of 7 +/- 3 minutes. Procedure times to access the five targets in the right atrium, right ventricle, left atrium, and left ventricle were 5.6 +/- 1.7, 4.6 +/- 1.5, 13.5 +/- 11.0, 7.0 +/- 2.9 minutes, respectively. There were no intracardiac damages associated with catheter manipulation noted in the excised hearts.

CONCLUSIONS

Endocardial catheter navigation and mapping using the robotic catheter remote control is safe and feasible. Moreover, the CCS could be used to perform transseptal puncture and left atrial instrumentation.

Microwave ablation for atrial fibrillation: dose-response curves in the cardioplegia-arrested and beating heart

BACKGROUND

Microwave ablation has been used to replace the traditional incisions used in the surgical treatment of atrial fibrillation. However, dose-response curves have not been established in surgically relevant models. The purpose of this study was to develop dose-response curves for the Flex 10 (Guidant, Inc) microwave device in both the acute cardioplegia-arrested heart and on the beating heart.

METHODS

Twelve domestic pigs (40 to 45 kg) were subjected to microwave ablation in either the arrested (n = 6) or beating heart (n = 6). The cardioplegia-arrested heart was maintained at 10 degrees to 15 degrees C while six atrial endocardial and seven right ventricular epicardial lesions were created in each animal. On the beating heart, six right atrial and seven ventricular epicardial lesions were created. Ablations were performed for 15, 30, 45, 60, 90, 120, and 150 seconds (65 W, 2.45 GHz). The tissue was stained with 2,3,5-triphenyl-tetrazolium chloride, and sectioned at 5-mm intervals. Lesion depth and width were determined from digital micrographs.

RESULTS

Mean atrial wall thickness was 2.8 mm (range, 1 to 8 mm). In the arrested heart, 94% of atrial lesions were transmural at 45 seconds and 100% were transmural at 90 seconds. In the beating heart, only 20% of atrial lesions were transmural despite prolonged ablation times (90 seconds). Ventricular lesion width and depth increased with duration of application, and were similar on the arrested and beating hearts.

CONCLUSIONS

Microwave ablation produces linear dose-response curves. Transmural lesions can be reliably produced on the arrested heart, but not consistently on the beating heart.

Early human experience with use of a deflectable fiberoptic endocardial visualization catheter to facilitate coronary sinus cannulation

BACKGROUND

Despite improvements in cardiac resynchronization therapy (CRT) implantation techniques, a significant minority of CRT attempts are unsuccessful. Inability to cannulate the coronary sinus (CS) because of difficult anatomy is a major reason for unsuccessful CRT implantation. Direct visualization of intracardiac structures during the implant may facilitate access into the CS. The present study describes CRT implantation with the aid of an endocardial visualization catheter (EVC).

METHODS

Fifty-eight consecutive patients (mean age 72 +/- 12 years; ejection fraction 26.2% +/- 7.0%; New York Heart Association [NYHA] class 2.9) underwent CRT implantation using a steerable fiberoptic EVC (Acumen Medical, Inc., Sunnyvale, CA).

RESULTS

The EVC was able to visualize the CS ostium in all cases. The CS was successfully cannulated in 57 (98.3%) of 58 patients. The time from vascular access to CS visualization was 6 +/- 5 minutes, and the total time to CS access was 8 +/- 6 minutes. Successful left ventricle (LV) lead implantation was accomplished in 55 (94.8%) of 58 patients. Three patients who had a previous history of failed LV lead implantation were successfully implanted using the EVC.

CONCLUSION

Fiberoptic imaging of intracardiac structures during CRT implantation may be performed rapidly in a wide range of patients with an EVC. The ability to visualize right atrial anatomy may aid CS access and LV lead implantation.

Current Strategies in the Management of Atrial Fibrillation

Treatment of atrial fibrillation (AF) has been undergoing significant changes recently. This is due partly to different mechanisms proposed for persistent and permanent AF and partly due to the introduction of energy-based techniques, providing less invasive procedures. This article aims to review the mechanisms of AF leading to the changes in clinical practice and to review the results of surgery, energy-based, and percutaneous techniques. It is difficult to compare and contrast the results of reported series in the literature due to different definitions of AF; freedom from and recurrence of it. Furthermore, in most series it is difficult to distinguish results of surgery for lone AF and AF associated with valvular heart disease and coronary artery disease.

Anatomic characterization of endocardial substrate for hemodynamically stable reentrant ventricular tachycardia: Identification of endocardial conducting channels

BACKGROUND

Detailed anatomic characterization of endocardial substrate of ventricular tachycardia (VT) is limited.

OBJECTIVES

The purpose of this study was to determine the endocardial dimensions and local electrogram voltage characteristics of the reentrant circuit. VT-related conducting channels corresponding to zones of slow conduction may be identified.

METHODS

Electroanatomic mapping was performed in 26 patients with uniform VT. Entrainment mapping was performed in 53 VTs, of which 19 entrance, 37 isthmus, 48 exit, and 32 outer loop sites were identified. The color display of voltage maps was adjusted to identify conducting channels associated with VT circuits. A conducting channel was defined as a path of multiple orthodromically activated sites within the VT circuit that demonstrated an electrogram amplitude higher than that of surrounding areas as evidenced by voltage color differences.

RESULTS

Forty-seven (84%) of 56 entrance or isthmus sites were located within dense scar (<0.5 mV). Nearly all exits (92%) were located in abnormal endocardium (<1.5 mV), with more than half (54%) located in the border zone (0.5-1.5 mV). VT-related conducting channels was identified in 18 of 32 VTs with detailed mapping (average length 32 +/- 22 mm). The voltage threshold in the conducting channels ranges from 0.1 to 0.7 mV (mean 0.33 +/- 0.15 mV).

CONCLUSION

(1) Most entrance and isthmus sites of hemodynamically stable VT are located in dense scar, whereas exits are located in the border zone. (2) VT-related conducting channels may be identified by careful voltage threshold adjustment. These findings have important implications regarding strategies for substrate-based VT ablation.

Value of high-density endocardial and epicardial mapping for catheter ablation of hemodynamically unstable ventricular tachycardia

BACKGROUND

Percutaneous epicardial mapping has been used for ablation of recurrent ventricular tachycardia (VT).

OBJECTIVES

The purpose of this study was to use a combined epicardial and endocardial mapping strategy to delineate the myocardial substrate for recurrent VT in both ischemic (n = 12) and nonischemic cardiomyopathy (n = 8), and to define the role of epicardial ablation.

METHODS

Electroanatomic mapping was performed in 20 patients. High-density voltage maps were obtained by acquiring both endocardial and epicardial electrograms. Electrograms derived from six patients with structurally normal hearts were used as controls. A total of 26 VTs were targeted in the 20 patients.

RESULTS

Most VTs (23/26 [88.5%]) were hemodynamically unstable. In patients with ischemic cardiomyopathy, the extent of endocardial scar was greater than epicardial scar. A definable pattern of scar could not be demonstrated in nonischemic cardiomyopathy. Pathologic examination of explanted hearts in two patients with nonischemic cardiomyopathy demonstrated that low-voltage areas were not always predictive of scarred myocardium. A substrate-based approach was used for catheter ablation. Catheter ablation was performed on the endocardium in all patients; additional epicardial delivery of radiofrequency energy was required in 8 (40%) of 20 patients for successful ablation. During follow-up (12 +/- 4 months), 15 (75%) of 20 patients have been arrhythmia-free.

CONCLUSION

Patients with ischemic cardiomyopathy tend to have a larger endocardial than epicardial scar. Use of epicardial and endocardial electroanatomic mapping to define the full extent of myocardial scars allows successful catheter ablation in patients with hemodynamically unstable VTs.

[Totally endocardial surgical ablation of atrial fibrillation combined with mitral valve surgery. Our experience with the Cardioablate pen]

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia found in mitral valve (MV) disease, occurring in 30 to 85% of patients. Since 1999, AF has been ablated using monopolar epicardial-endocardial radiofrequency. In this study, we describe our own endocardial experience of using the Cardioablate monopolar radiofrequency irrigated pen for the ablation of AF in patients undergoing MV surgery and an analysis of the short and mid-term results.

METHODS

From August 2002 to February 2004, a monopolar radiofrequency pen was used to ablate AF in 29 patients undergoing MV replacement or repair (24 females, 82.7%). Preoperative AF was paroxysmal in 27.6% of the patients, persistent in 13.8%, and permanent in 58.6%. The mean left atrial diameter was 65.8 +/- 11.4 mm (range 40-92 mm). In all the patients the ablation lines were created under conditions of extracorporeal circulation and aortic cross-clamping and carried out according to the Alfieri's set. The left atrial appendage was resected or excluded. Endocardial ablation increased the duration of the operation by a mean time of 14.8 +/- 2.7 min with an average time of 7.3 +/- 1.4 min for radiofrequency application.

RESULTS

All patients left the operating room with ginus rhythm (SR) or with atrioventricular pacing. Perioperative AF was common, affecting 51.7% of patients. Six patients required electrical cardioversion. Both early postoperative death (2 patients, 6.8%) and complications were not procedure-related. At discharge, all patients were in SR. The mean follow-up was 14.8 +/- 5.2 months (range 7-25 months). Only 3 patients (11.1%) lost SR within the first 6 months of follow-up but it was recovered in all cases through the use of electrical cardioversion (2 patients) or antiarrhythmic drugs.

CONCLUSIONS

The totally endocardial monopolar radiofrequency pen facilitates a quick and safe AF ablation in patients with MV disease. Its only theoric limitation concerns the transmurality of the lesions. Perioperative AF is common and should be treated aggressively. By 6 months postoperatively, 100% of patients are free of AF or atrial flutter with recovery of normal atrial contraction. More patients and longer follow-up are necessary to document the long-term results of this simple procedure.

Overview: Ventricular Restoration—A Surgical Approach to Reverse Ventricular Remodeling

Congestive heart failure is most often caused by scar from coronary occlusion. The transition from occluded vessel to scar to dilation results in a remodeled ventricle that changes shape from ellipse to sphere. This shape change following an index event is called remodeling and a surgical approach for restoration (bring back to normal) will be described that uses the patient's own tissue, rather than employing heart replacement by mechanical devices or transplantation. The surgical restoration approach was taken by the RESTORE group that comprises an international medical and surgical team that will report (a) the remodeling infrastructure, role of compensatory remote muscle, and factors underlying surgical restoration decisions, (b) structural basis for ventricular geometric changes and surgical background for restoration, (c) individual rebuilding experience in 1150 patients over 20 years from one center, (d) integrated 5 year results from the RESTORE team in 1198 patients, (e) electrical aspects of restoration in 382 patients with only one AICD used, (f) how restoration improves mechanical synchrony without electrical devices, (g) geometric reasons for secondary mitral insufficiency and impact of adding mitral repair during SVR procedures, and (h) importance of defining site specific scar in no ischemic disease to identify a similar trigger lesion in non ischemic cardiomyopathy. The importance of a team approach by the RESTORE group may set the benchmark for collaborative world wide groups, and thereby depart from traditional focal approaches by individual disciplines.

Heart Failure Following Anterior Myocardial Infarction: An Indication for Ventricular Restoration, a Surgical Method to Reverse Post-Infarction Remodeling

Anterior myocardial infarction produces abrupt left ventricular (LV) dysynergy and global systolic dysfunction. Rapid intense neurohumoral activation, infarct expansion, and early ventricular chamber dilatation all contribute to restoring a normal stroke volume despite a persistently depressed ejection fraction. Continued neurohumoral activation provokes late remodeling of the remote non-infarcted myocardium, characterized by an abnormal progressively increasing LV volume/mass ratio that leads to further LV remodeling. Heart failure is a progressive disorder of LV remodeling. Heart failure from post-infarction remodeling is unique because of the persistent non-functioning scar that self- perpetuates abnormal loading conditions and neurohumoral activation. Medical therapy attenuates remodeling and improves survival but does not change the size of the scar. Surgical ventricular restoration to exclude the non-functioning infarct from the ventricular cavity decreases ventricular volumes, increases global ejection fraction, attenuates neurohumoral activation and yields an excellent 5-year survival. Combined medical and surgical therapy is recommended in this patient population.

Surgical Ventricular Restoration: The RESTORE Group Experience

Congestive heart failure may be caused by late left ventricular (LV) dilation following anterior infarction. Early reperfusion prevents transmural necrosis, and makes the infarcted segment akinetic rather than dyskinetic. Surgical ventricular restoration (SVR) reduces LV volume and creates a more elliptical chamber by excluding scar in either akinetic or dyskinetic segments. The international RESTORE group applied SVR in a registry of 1198 post-infarction patients between 1998 and 2003. Early and late outcomes were examined and risk factors identified.Concomitant procedures included coronary artery bypass grafting in 95%, mitral valve repair in 22%, and mitral valve replacement in 1%. Overall 30-day mortality after SVR was 5.3% (8.7% with mitral repair vs. 4.0% without repair, p < .001) Perioperative mechanical support was uncommon (< 9%). Global systolic function improved postoperatively, as ejection fraction increased from 29.6 +/- 11.0% to 39.5 +/- 12.3% (p < .001) and left ventricular end systolic volume index decreased from 80.4 +/- 51.4 ml/m(2) to 56.6 +/- 34.3 ml/m(2) (p < .001). Overall 5-year survival was 68.6 +/- 2.8%, Logistic regression analysis identified EF < or = 30%, LVESVI > o = 80 ml/m(2), advanced NYHA functional class, and age > or =75 years as risk factors for death. Five-year freedom from hospital readmission for CHF was 78%. Preoperatively, 67% of patients were class III or IV, and postoperatively 85% were class I or II.SVR improves ventricular function and is highly effective therapy in the treatment of ischemic cardiomyopathy with excellent 5-year outcome.

Endoventricular Patch Reconstruction of Ischemic Failing Ventricle. A Single Center with 20 years Experience. Advantages of Magnetic Resonance Imaging Assessment

The left ventricular reconstruction (LVR) with endoventricular circular patch plasty (EVCPP) was reported in 1984 as a surgical method to rebuild left ventricular aneurysm or asynergy after myocardial infarction. Scarred LV wall can be dyskinetic or akinetic according to the type of infarction (transmural or not), and the progressive dilatation of LV (remodeling) depends on the size of the asynergic scar. Assessment of this extension and of LV volume and performances, is easy and reliable by magnetic resonance (CMR). The surgical technique is based on the insertion inside the ventricle on contractile myocardium, of a circular patch restoring curvature and physiological volume, and allowing exclusion of asynergic non resectable regions. The ventricular reconstruction method also has other components that include coronary revascularization (almost always), mitral repair (if needed) and endocardectomy when spontaneous or inducible ventricular tachycardia (VT) are present. The experience of the authors (> 1100 cases) and results obtained by other Centers, allows proposal of this technique as a way to treat the ischemic failing ventricle.

Direct imaging of transvenous radiofrequency cardiac ablation using a steerable fiberoptic infrared endoscope

BACKGROUND

Direct imaging through blood has been achieved in vivo using fiberoptics and infrared wavelength technology.

OBJECTIVES

The purpose of this study was to determine the feasibility of using a percutaneous, steerable, fiberoptic infrared endoscope to identify and characterize the electrode-tissue interface during transvenous cardiac ablation.

METHODS

Infrared endoscopy was performed during 24 catheter ablation attempts in 10 mongrel dogs. Infrared imaging was performed through a transparent dome located at the tip of a 7Fr steerable endoscope using an imaging wavelength of 1,620 nm. Radiofrequency ablation was performed using a 4-mm-tip electrode catheter. Attempts were made to identify the electrode-endocardial interface at each ablation site and to characterize any signal changes during ablation.

RESULTS

The electrode-tissue interface could be identified at 19 of the 24 ablation sites. Changes at the electrode-tissue interface were observed during ablation at 14 sites, which included a gradual increase in the tissue signal intensity at 12 sites. Small lucencies near the ablation electrode were observed at six sites. There was no interference during energy delivery. Endocardial features identified by endoscopy correlated with the postmortem appearance.

CONCLUSION

Direct imaging of intracardiac structures and the electrode-tissue interface can be achieved through blood during transvenous catheter ablation with infrared endoscopy using a steerable, fiberoptic, infrared endoscopic catheter. Ablation lesion formation can be seen as a gradual increase in signal intensity. Fiberoptic infrared endoscopy appears to be a promising new tool for guiding catheter ablation.

Ventricular Structure and Surgical History

The Reviews report will establish guidelines that underlie why the "restoration concept" may develop a paradigm shift in thinking, by addressing the geometric underpinnings of heart failure and their evolution. This presentation will (a) show that the underlying structure of the failing dilated heart involves a cardiac architectural change from the normal elliptical shape toward a dilated spherical form, (b) define the anatomic framework of this shape change, (c) convey the functional characteristics of heart function that result from this architectural underpinning, (d) describe the pattern of CHF development, (e) indicate imaging measurement guidelines to follow as heart form adversely changes from ellipse to sphere, (f) identify how such architectural changes alter prognosis, and (g) develop a historical evolution of surgical approaches to alter form to improve function to create the background for subsequent RESTORE team reports of current restoration to treat CHF and its complications.

A cooled intraesophageal balloon to prevent thermal injury during endocardial surgical radiofrequency ablation of the left atrium: a finite element study

Recent clinical studies on intraoperative monopolar radiofrequency ablation of atrial fibrillation have reported some cases of injury to the esophagus. The aim of this study was to perform computer simulations using three-dimensional finite element models in order to investigate the feasibility of a cooled intraesophageal balloon appropriately placed to prevent injury. The models included atrial tissue and a fragment of esophagus and lung linked by connective tissue. The lesion depth in the esophagus was assessed using a 50 degrees C isotherm and expressed as a percentage of thickness of the esophageal wall. The results are as follows: (1) chilling the esophagus by means of a cooled balloon placed in the lumen minimizes the lesion in the esophageal wall compared to the cases in which no balloon is used (a collapsed esophagus) and with a non-cooled balloon; (2) the temperature of the cooling fluid has a more significant effect on the minimization of the lesion than the rate of cooling (the thermal transfer coefficient for forced convection); and (3) pre-cooling periods previous to RF ablation do not represent a significant improvement. Finally, the results also suggest that the use of a cooled balloon could affect the transmurality of the atrial lesion, especially in the cases where the atrium is of considerable thickness.

Comparison of Volume Study by Left Ventriculography and Gated SPECT in Endoventricular Circular Patchplasty

Although quantitative gated SPECT (QGS) is widely used for left ventricular (LV) volume study, its accuracy is not established for those who have a large myocardial infarction scar or who had endoventricular circular patch plasty (EVCPP). Therefore, we compared LV volumes and LVEF calculated by QGS and those calculated by left ventriculography (LVG) before and after EVCPP. Sixteen patients (13 men and 3 women, mean age 67 +/- 9.5 years) were treated with EVCPP for postinfarction LV dyskinetic and/or akinetic scar. All patients were evaluated with both QGS and LVG before and after surgery. QGS was performed using eight frames per cardiac cycle, 1 hour after 740 MBq (99 m)Tc-tetrofosimin was administered. LVG images were acquired at a frame rate of 30 frames per second in the right anterior oblique 30-degree projection. We compared LV end-diastolic volume (LVEDV), LV end-systolic volume (LVESV), and LV ejection fraction (LVEF) between QGS and LVG. There was an excellent linear correlation between QGS and LVG in LVEDV (preoperative; r = 0.87, postoperative; r = 0.94), LVESV (preoperative; r = 0.95, postoperative; r = 0.89), and LVEF (preoperative; r = 0.73, postoperative; r = 0.81) before and after EVCPP. However, both preoperative LV volumes and postoperative LVEF calculated from QGS gave a smaller value than those calculated from LVG. Postoperative volume data by QGS was much close to LVG. The present study indicated that volume study by QGS is very useful to evaluate the LV function after EVCPP. However, we should pay attention to those facts.

[Dor operation for left ventricular aneurysm with sustained ventricular tachycardia]

A 60-year-old woman was admitted to our hospital because of syncope attack due to sustained ventricular tachycardia (VT). She was treated medically after cardiopulmonary resuscitation. Coronary arteriography revealed a 99% stenosis of right coronary artery (posterior descending artery: # 4 PD), a 90% stenosis of left descending artery (# 6) and left akinetic aneurysm was demonstrated. The patient successfully underwent Dor operation with endocardial cryoablation. The postoperative course was uneventful and the recurrence of VT was never recognized clinically.

Preliminary results with the microwave-modified maze III procedure for the treatment of chronic atrial fibrillation

Between February 2003 and January 2004 a microwave-modified Maze III procedure was performed as an associated procedure in nine patients in chronic atrial fibrillation undergoing surgery for heart valve disease. Clinical follow-up was carried out in all survivors, and an echocardiographic assessment done in all those in sinus rhythm, during the first week of February 2004. There were six women and three men with a mean age of 60 +/- 9.4 years. Their rhythm at the end of surgery was sinus in 2 patients, nodal in 4, and complete AV block in 3. One patient died in hospital and there patients had no other complications related to the procedure. By the time of hospital discharge, four patients were in sinus rhythm and four were in atrial fibrillation. After a mean follow-up of 5.2 +/- 3.3 months there were no late deaths, 5 patients were in sinus rhythm, 1 required a permanent pacemaker in DDDR mode for persistent sinus bradycardia, and 2 remained in atrial fibrillation. Echocardiographic assessment, performed at a mean of 4.9 +/- 2.5 months after surgery in all patients in sinus rhythm or with a pacemaker, demonstrated biatrial contraction in five patients. The Cox-Maze III procedure can be performed safely and with good results using microwave energy instead of the conventional "cut and sew" technique.

Sensor Guided Ablation Procedure of Left Atrial Endocardium

In this paper, we present a sensor guided ablation procedure of highly motile left atrium. It uses a system which automatically registers the 4D heart model with the position sensor on the catheter, and visualizes the heart model and the position of the catheter together in real time. With this system clinicians can easily map the motile left atrium shape and see where the catheter is inside it, therefore greatly improve the efficiency of the ablation operation.

Prognostic value of endocardial electromechanical mapping in patients with left ventricular dysfunction undergoing percutaneous coronary intervention

Endocardial electromechanical mapping (EEM) has been proposed as a method for myocardial viability assessment. However, the impact of EEM data on clinical outcome has not been studied before. We sought to assess the prognostic value of EEM in patients with left ventricular (LV) dysfunction undergoing percutaneous coronary intervention (PCI). Seventy-five patients with coronary artery disease and LV dysfunction (angiographic LV ejection fraction [EF] 49 +/- 15%) underwent LV EEM for myocardial viability assessment before coronary revascularization. EEM parameters included mean unipolar electrographic amplitude, mean local shortening, LV volumes, LVEF, number of regions with electrographic amplitudes <7.5 mV, number of electromechanical mismatch, and match regions. Cardiac death, nonfatal myocardial infarction, nonfatal stroke, and acute heart failure requiring hospitalization were defined as clinical events. During a follow-up of 3.6 +/- 1.8 years, 20 clinical events occurred. Event-free survival after coronary revascularization was significantly better in patients with a mean unipolar electrographic amplitude of >/=9.5 mV than in patients with a mean unipolar electrographic amplitude of <9.5 mV (88% vs 57%; p <0.005). Cox regression analysis revealed angiographic LVEF, mean electrographic amplitude, number of regions with electrographic amplitudes <7.5 mV, number of electromechanical match regions, and EEM EF as univariate predictors of clinical events. In a multivariate analysis, angiographic LVEF <40% (hazard ratio 4.78, p <0.005) and mean electrographic amplitude <9.5 mV (hazard ratio 2.92, p <0.05) were independent predictors of clinical events. Thus, EEM provides prognostic information in patients with LV dysfunction undergoing coronary revascularization.

In Vivo Measurement of Swine Endocardial Convective Heat Transfer Coefficient

We measured the endocardial convective heat transfer coefficient h at 22 locations in the cardiac chambers of 15 pigs in vivo. A thin-film Pt catheter tip sensor in a Wheatstone-bridge circuit, similar to a hot wire/film anemometer, measured h. Using fluoroscopy, we could precisely locate the steerable catheter sensor tip and sensor orientation in pigs' cardiac chambers. With flows, h varies from 2500 to 9500 W/m2 x K. With zero flow, h is approximately 2400 W/m2 x K. These values of h can be used for the finite element method modeling of radiofrequency cardiac catheter ablation.

Radionuclide study of mid-term left ventricular function after endoventricular circular patch plasty

OBJECTIVE

Although the early result of endoventricular circular patch plasty (EVCPP) has been reported, few are seen about the long-term results. We studied left ventricular (LV) function in the early and mid-term periods after EVCPP with electrocardiographic-gated single photon emission computed tomography (Gated SPECT).

METHODS

Consecutive 14 patients with LV asynergy after myocardial infarction, who had the EVCPP procedure, were studied by Gated SPECT. Mean age of patients was 67+/-10 years. Gated SPECT images were obtained and LV end-diastolic volume index (EDVI), LV end-systolic volume index (ESVI) and ejection fraction (EF) were studied with QGS(+) program. Gated SPECT study was performed before surgery, early (23 days) and mid-term periods (32 months) after surgery.

RESULTS

EDVI changed significantly from preoperative value to early postoperative value (107+/-39 to 72+/-37 ml/m(2), P < 0.01). There was no significant difference between early and mid-term postoperative values. ESVI also changed significantly from preoperative value to early postoperative value, and from early value to mid-term postoperative value (78+/-37 to 51+/-34 to 47+/-35 ml/m(2), P < 0.05, respectively). EF increased significantly from preoperative value to early postoperative value, and from early value to mid-term postoperative value (30+/-10 to 35+/-13 to 45+/-18%, P < 0.05, respectively).

CONCLUSIONS

Direct influence of EVCPP brought significant improvement of LV function in early period. Further decrease of ESVI and increase of EF were noticed from early period to mid-term period. This result suggest that the effect of EVCPP sustains long and yields reverse LV remodeling.

Endocardial radiofrequency ablation of septal hypertrophy

Transcoronary alcohol ablation of septal hypertrophy (TASH) is a therapeutic catheter based option and an alternative to surgery in the treatment of patients with hypertrophic obstructive cardiomyopathy. However, the anatomic variability of the vascularisation of the obstructing septal bulge may limit the therapeutic efficacy. Thus, we examined an endocardial approach as an alternative. Based on the effects of radiofrequency energy in the treatment of cardiac arrhythmias this is the first report about the use of this modality. It refers to a 45-year-old patient with severe HOCM. The energy was applied by using a cooled-tip ablation catheter at the right side of the ventricular septum. The site corresponded to the obstructing area of the left ventricle. The following changes could be observed: a reduction of the intraventricular pressure gradient during the therapeutic session, a gradient reduction at cycle exercise as assessed by Doppler echocardiography 7 days after intervention, a subaortic septal hypokinesia, an enlargement of the left ventricular outflow tract, a reduction of the septal thickness and an increase in the exercise capacity using the 6-minute walk test. These changes are in accordance with the results after TASH and surgical treatment. The new modality might extend the possibilities in the catheter-based treatment of patients with severe HOCM.

Alternative Energy Sources for Surgical Atrial Ablation

As less complex modifications of the Maze procedure have been developed, a number of energy sources have been introduced to facilitate the creation of electrically isolating lesions within the atria. These include cryoablation, radiofrequency, microwave, laser, and focused ultrasound. Although each of these sources works slightly differently, the goal of all thermal sources is to heat tissue to a temperature (50 degrees C) above which irreversible electrical isolation occurs. These sources have been utilized both endocardially in arrested heart procedures as well as epicardially in the beating heart setting. There are several obstacles to the use of these sources epicardially, mostly related to the heat sink effect of endocardial blood. Several recent modifications have been introduced that will hopefully increase the efficacy of these sources in beating heart applications.

Combined Epicardial-Endocardial Approach to Ablation of Inappropriate Sinus Tachycardia

A combined epicardial-endocardial approach to ablation of inappropriate sinus tachycardia in a highly symptomatic patient who failed to respond to medical therapy and endocardial ablation is described. The anatomy and physiology of the sinus node is discussed, providing a basis for performing this procedure. This case provides an additional therapeutic option for a condition that often is difficult to manage.

Left Ventricular Endocardial Lead Placement Using a Modified Transseptal Approach

Coronary sinus cannulation and placement of left ventricular (LV) leads can be difficult. Occasionally alternative approaches are required. We report the first case of a modified transseptal LV endocardial lead placement via the left axillary vein for cardiac resynchronization.

Catheter ablation to suppress atrial fibrillation: evolution of technique at a single center

BACKGROUND

Catheter ablation of atrial fibrillation is a rapidly evolving art. There is currently no consensus as to optimal methodology. We report a sequential experience, during which three distinct ablation techniques were utilized.

METHODS

A cohort of 112 patients in whom atrial fibrillation onset was precipitated by ectopy arising solely from myocardium investing the pulmonary veins underwent catheter ablation using one of three techniques: focal (Group A); individual vein encircling (Group B); vestibule encircling (Group C). In each group, non-fluoroscopic guidance of the mapping and ablation process was provided by the tandem use of CARTO and intracardiac echocardiography.

RESULTS

In all groups, endocardial topography was complex, and ablation electrode-endocardial contact was often unstable. Maximal electrode temperatures were low, despite frequent echocardiographic evidence of myocardial boiling. A significant progression in the number of radiofrequency energy applications between groups A and C was observed. Although acute suppression of atrial fibrillation inducibility was observed uniformly, chronic suppression rates were significantly different: Group A = 47%; Group B; 69%; Group C = 87%.

CONCLUSIONS

In this non-concurrent cohort, the rate of chronic suppression of atrial fibrillation correlated with the amount of myocardium ablated or electrically isolated. Prospective data will be required to further evaluate whether "more is better."

Surgical techniques for emergent repair of post-infarction ventricular septal defect: compare endocardial patch and infarct exclusion method with traditional method

BACKGROUND

The traditional surgical repair of post-infarction ventricular septal defect (VSD) includes excision of necrotic myocardium and approximation of the remaining of healthy ventricular wall and septal portion. The exclusion method emphasizes no excision of infarcted myocardium, preservation of the left ventricular geometry and exclusion of infarction area. We discuss our experiences in 13 patients and compared the results obtained from 2 different surgical methods.

METHODS

From July 1996 to December 2001, 13 patients with post-infarction VSD received emergent repair. Seven patients were repaired in the traditional way and the other 6 with infarct exclusion method. There were 9 men and 4 women, ranging in age from 57 to 79. In the traditional group, all 7 patients were classified as NYHA IV and supported by intra-aortic balloon counter-pulsation (IABP) and 4 patients were for synchronous coronary bypass grafting. Patients using exclusion method were the 1 classified as NYHA III and 5 as IV with cardiogenic shock and supported by IABP. Coronary bypass grafting was performed concomitantly in 2 patients.

RESULTS

Five patients died within 30 days after the surgery. Four patients (mortality rate = 57.1%) had reconstruction in traditional way and 1 (mortality rate = 16.6%) in exclusion way. The complication rate was higher in the traditional group (= 100%, n = 7, p = 0.005). In the traditional group, 1 patient received heart transplantation due to persistent severe pump failure and recovered well. Two received tracheostomy due to respiratory failure and 1 died 2 months later. In the group of exclusion method, 1 patient suffered recurrent VSD 2 days after the first surgery and died due to ventricular arrhythmia.

CONCLUSIONS

The surgical mortality caused by acute post-infarction VSD has decreased with endocardial patch and infarction exclusion method. Rapid diagnosis, appropriate preoperative management and delicate surgical repair improve the overall results and help to attain long-term survival.

Counter intuitive relations between in vivo RF lesion size, power, and tip temperature

BACKGROUND

Radiofrequency (RF) lesion size in vitro is positively correlated with applied power and catheter tip temperature. However, the relation between RF lesion size, power, and tip temperature in vivo remains unclear. We hypothesized that due to flow, anatomy and tip contact effects in vivo, increased tip temperature would be inversely related to applied power and RF lesion size.

METHODS

RF lesions were created on the endocardium of 16 pigs using 5, 6, and 7 Fr catheters. The ablation generator was set to achieve a temperature of 70 degrees C. RF lesions were created in different regions of the heart so as to encompass a wide range of blood flow and catheter movement conditions. RF lesions were measured acutely (DIMEN, mm) and correlated with average power applied (POWER, W), and average tip temperature (TEMP, degrees C). The POWER and TEMP relation was also examined.

RESULT

For TEMPs below 55 degrees C, the power output from the generator was typically maximized at 50 W. At TEMPs above 55 degrees C, POWER decreased exponentially with increasing TEMP (POWER = 50 - exp(-((41-TEMP)/7)), r = 0.98, p < 0.05). Further, DIMEN tended to be inversely related to TEMP (Slope: -0.07 +/- 0.04, r = -0.15, p = 0.07); but, was positively related to POWER (Slope: 0.04 +/- 0.02, r = 0.23, p < 0.05). These relations varied by tip size and estimated local blood flow characteristics.

CONCLUSION

In vivo, variable tissue contact and flow yield DIMEN-POWER-TEMP relations opposite to those found in vitro. These counterintuitive results suggest that maximum in vivo RF lesion size is achieved when power is maximized at tip temperatures between 50 and 60 degrees C.

Endocardial cryotherapy as a novel strategy of improving myocardial perfusion in a patient with severe coronary artery disease

Patients with intractable angina pectoris due to end-stage coronary artery disease who are not amenable to conventional revascularization provide a therapeutic challenge. We describe the first published case of a young patient with intractable coronary artery disease that was successfully treated by endocardial cryotherapy.

Endocardial mapping of right ventricular outflow tract tachycardia using noncontact activation mapping

INTRODUCTION

Activation mapping and pace mapping identify successful ablation sites for catheter ablation of right ventricular outflow tract (RVOT) tachycardia. These methods are limited in patients with nonsustained tachycardia or isolated ventricular ectopic beats. We investigated the feasibility of using noncontact mapping to guide the ablation of RVOT arrhythmias.

METHODS AND RESULTS

Nine patients with RVOT tachycardia and three patients with ectopic beats were studied using noncontact mapping. A multielectrode array catheter was introduced into the RVOT and tachycardia was analyzed using a virtual geometry. The earliest endocardial activation estimated by virtual electrograms was displayed on an isopotential color map and measured 33 +/- 13 msec before onset of QRS. Virtual unipolar electrograms at this site demonstrated QS morphology. Guided by a locator signal, ablation was performed with a mean of 6.9 +/- 2.2 radiofrequency deliveries. Acute success was achieved in all patients. During follow-up, one patient had a recurrence of RVOT tachycardia. Compared with patients (n = 21) who underwent catheter ablation using a conventional approach, a higher success rate was achieved by noncontact mapping. Procedure time was significantly longer in the noncontact mapping group. Fluoroscopy time was not significantly different in the two groups.

CONCLUSION

Noncontact mapping can be used as a reliable tool to identify the site of earliest endocardial activation and to guide the ablation procedure in patients with RVOT tachycardia and in patients with ectopic beats originating from the RVOT.

Intra-atrial temperatures in radiofrequency endocardial ablation: histologic evaluation of lesions

BACKGROUND

Because of the limited information on the effects of ablation in human tissues, we studied intra-atrial temperatures during endocardial radiofrequency applications. We correlated the intra-tissue temperatures with the tissue thickness and with the histologic appearance of the lesions.

METHODS

Radiofrequency currents were delivered to human atrial tissue, simulating conditions in endocardial ablation during surgery at set temperature of 70 degrees and 80 degrees C, and intra-tissue temperatures were measured with thermocouples. Radiofrequency applications at 70 degrees C were performed in patients undergoing mitral valve surgery and biopsy specimens were obtained. Samples from in vitro studies and from patients were assessed histologically.

RESULTS

The subepicardial temperatures were usually over 60 degrees C in applications in vitro at 70 degrees C and over 70 degrees C in applications at 80 degrees C. Values were higher when the interior of the tissue was warmer than its surface as a result of consecutive radiofrequency applications over the same area. Histologic examination of 12 in vitro samples showed that 10 had transmural lesions. Five of 10 samples from patients with mitral valve surgery had lesions confined to the endocardium, 3 had damaged variable portions of the myocardium, and 2 had transmural lesions.

CONCLUSIONS

Although it is possible to obtain transmural lesions in vitro and in vivo with endocardial applications at 70 degrees C, it is significantly more difficult to achieve transmural lesions in patients with mitral valve disease than in normal atrial tissue in vitro. Consecutive applications can raise the intra-tissue temperatures to values significantly higher than those used for application. Our findings suggest that the composition of the endocardium and of the myocardium is a major determinant in lesion formation.

An instrument to measure the heat convection coefficient on the endocardial surface

This work describes the fundamentals and calibration procedure of an instrument for in vivo evaluation of the heat convection coefficient between the endocardium and the circulating blood flow. The instrument is to be used immediately before radio-frequency cardiac ablation is performed. Thus, this instrument provides researchers with a valuable parameter to predict lesion size to be achieved by the procedure. The probe is a thermistor mounted in a Swan-Ganz catheter, and it is driven by a constant-temperature anemometer circuit. A 1D model of the sensor behaviour in a convective medium, the calibration procedure and the apparatus are explained in detail. Finally, a performance analysis of the instrument in the range of 200-3500 W m(-2) K(-1) shows that the average absolute error of full scale is 7.4%.

Successful management of osteal perforation of left anterior descending artery with coated stent

Coronary perforation is a rare complication of percutaneous coronary intervention. We report a case of left anterior descending artery osteal perforation that led to acute cardiac tamponade during excimer laser angioplasty. Perforation was successfully covered with a PTFE-coated stent with preserved distal coronary flow.

Two cases using "epi-endocardial patch repair" for postinfarction left ventricular rupture

The treatment points of left ventricular (LV) free wall rupture after acute myocardial infarction (MI), so far, are to prevent a deterioration of LV function after MI and to prevent a recurrence or extension of the dissection of the infarcted/necrotic myocardium to stop bleeding. We report two cases of LV rupture after myocardial infarction that underwent epicardial patch repair using deep epicardial sutures reaching LV subendocardial area ("epi-endocardial patch" repair). The procedure was done under beating condition with cardiopulmonary bypass in the first case and with preoperatively percutaneous cardiopulmonary support system (PCPS) in the second case to prevent a deterioration of LV function. Hemostasis was effective and complete, and extension of the intramuscular dissection was well blocked. The patients recovered LV function soon. The epi-endocardial sutures can be placed safely without inducing new ischemia, and the method might be possible with beating condition.

Idiopathic monomorphic ventricular tachycardia originating from the left aortic sinus cusp in children: endocardial mapping and radiofrequency catheter ablation

BACKGROUND

Idiopathic repetitive monomorphic ventricular tachycardia with an inferior axis and left bundle branch block pattern typically originates from the superior right ventricular outflow tract. When indicated, radiofrequency catheter ablation is usually safe and effective. However, a left ventricular origin has been described recently in adult patients in whom ablation attempts in the right ventricular outflow tract were unsuccessful. Experience in pediatric patients is limited.

PATIENTS AND METHODS

Since 1998, 13 young patients suffering from symptomatic ventricular tachycardia episodes with an inferior axis and left bundle branch block pattern underwent an electrophysiological study and radiofrequency catheter ablation. In 2 patients, age 13 and 15 years, no endocardial local electrograms preceding the surface ECG QRS complex could be recorded within the right ventricular outflow tract during ventricular ectopy. Detailed mapping within the left ventricular outflow tract and in the aortic root revealed local electrograms 25 and 53 ms earlier than the QRS complex and a 11/12 and 12/12 lead match during pacing inferior and anterior to the ostium of the left main coronary artery in the left aortic sinus cusp. Earliest activation was recorded 10 and 12 mm away from the coronary artery ostium identified angiographically. In each of the patients, one single radiofrequency current application (60 degrees C, 30 W, duration 30 and 60 s, respectively) resulted in complete cessation of ventricular ectopy. Subsequent selective injection into the left coronary artery did not reveal any abnormalities. During follow-up (2 and 34 months) off any antiarrhythmic drugs, both of the patients are in continuous normal sinus rhythm.

CONCLUSION

In young patients with symptomatic idiopathic ventricular tachycardia originating from the left aortic sinus cusp, radiofrequency catheter ablation was safe and effective.

Mechanical compliance of the endocardium

Radio-frequency (RF) ablation is an accepted treatment for cardiac arrhythmias related to abnormal focal cardiac substrate. The penetration depth of the electrode into the endocardium affects lesion size, a critical determinant of success of RF ablation. We measured the relation between the mechanical compliance and the penetration depth of RF ablation catheter electrode at frequently ablated areas of the endocardium and examined the influence of time after death on mechanical properties of the tissue. We measured force versus time for eight insertion depths of the catheter electrode into full-thickness endocardial samples derived from the mitral valve annulus, the left ventricular free wall and the tricuspid valve annulus. We varied the time after death at 15, 40 min, 3, 8, and 18 h and repeated our measurements. At 15 min after death, the first 0.5mm penetration depth caused the fastest relaxation at 55 s. Force decay decreased dramatically at 15 min after death as the penetration depth increased from 0.5 to 4mm. We used the force data sampled at 60s after insertion to approximate the elasticity. We observed the relations between the force versus the insertion depth. The force increased by a factor of 5 for the mitral valve annulus and 8 for the left free wall from 15 min to 18 h. We derived coefficients of a second-order polynomial equation relating the force data to insertion depth with R(2)>0.99.

Endocardial mapping of electrophysiologically abnormal substrates and cardiac arrhythmias using a noncontact nonexpandable catheter

INTRODUCTION

In previous studies, we established methodology for reconstructing endocardial potential maps, electrograms, and isochrones from a noncontact intracavitary catheter during a single beat. Recently, we evaluated this approach using a 9-French (3-mm) spiral catheter in a normal heart preparation. Here we extend the approach to hearts with structural disease and examine its ability to detect and characterize abnormal electrophysiologic (EP) substrates and to map ventricular arrhythmias on a beat-by-beat basis.

METHODS AND RESULTS

Reconstruction of endocardial potentials from cavity potentials measured with 82 electrodes mounted on a 9-French spiral catheter was performed in an isolated canine left ventricle (LV). Endocardial potentials were recorded with 91 intramural needles, providing a gold standard for evaluating the noncontact reconstruction. Studies were performed in a normal LV (control) and the same LV 3 hours after left anterior descending coronary artery occlusion and ethanol injection to create an infarct. Abnormal EP characteristics over the infarct were faithfully reconstructed, including (1) low potentials and electrogram derivatives; (2) fractionated electrograms; (3) small deflections on electrograms reflecting local activation; and (4) slow discontinuous conduction transverse to fibers. During arrhythmia, beat-to-beat dynamic shifts of initiation site and activation pattern were captured by the reconstruction.

CONCLUSION

Noncontact, nonexpendable catheter mapping can locate and characterize abnormal EP substrates and can capture the endocardial sequence of an arrhythmia during a single beat.

Microwave ablation for surgical treatment of atrial fibrillation

Microwave energy is a relatively new energy modality that is being used for surgical atrial ablation as a treatment of atrial fibrillation. Microwave energy works by dielectric heating and has a favorable thermal profile that permits both rapid endocardial and epicardial ablation. The device is also extremely flexible and can be easily adapted to minimally invasive applications. The device has been used in over 600 patients with a success ranging from 70% to 90% and without any device-related complications. Many of these patients have had their ablations performed from the epicardium on the beating heart without the aid of cardiopulmonary bypass. Microwave atrial ablation is likely to become an important part of the surgical armamentarium, particularly for those performing minimally invasive approaches to cure atrial fibrillation.