Extended endocardial resection for the treatment of ventricular tachycardia and ventricular fibrillation

Surgical treatment of left ventricular aneurysm in patients with prior myocardial infarction in the absence of obstructive coronary artery disease (MINOCA): a cohort study

BACKGROUND

There is a paucity of studies examining the treatment of patients with prior myocardial infarction in the absence of obstructive coronary arteries (MINOCA) and with a concomitant left ventricular aneurysm. Our study aims to illustrate the clinical characteristics and report the mid-term surgical outcomes in this distinct entity.

METHODS

Ten patients with MINOCA and left ventricular aneurysm were investigated. The MINOCA was diagnosed according to Scientific Statement from the American Heart Association. The indication for left ventricular reconstruction was as follows: clear evidence of both an aneurysmal and akinetic left ventricle with a history of myocardial infarction accompanied by heart failure symptoms, angina, or ventricular arrhythmias. Major adverse cardiovascular and cerebrovascular events (MACCE), including death, myocardial infarction, stroke was considered the primary endpoints.

RESULTS

The median follow-up for the whole study population was 64.5 months. Seven MINOCA patients developed a left ventricular aneurysm within 4 years and three MINOCA patients were found to have a concomitant left aneurysm at the first admission. Before surgery, no patients were prescribed angiotensin-converting enzyme inhibitors. Statins, dual antiplatelet therapy, and β-blockers were prescribed in 2, 5, and 5 patients, respectively. After surgery, no MACCE occurred in the follow-up. There was a significant increase in ejection fraction (EF) in the follow-up (p = 0.0009).

CONCLUSIONS

Close monitoring and standard medical treatment are required before a left ventricular aneurysm occurs in MINOCA patients. Left ventricular reconstruction remains a viable option for MINOCA patients with left ventricular aneurysms and mid-term outcomes were satisfying in this distinct entity.

The value of functional substrate mapping in ventricular tachycardia ablation

In the setting of structural heart disease, ventricular tachycardia (VT) is typically associated with a re-entrant mechanism. In patients with hemodynamically tolerated VTs, activation and entrainment mapping remain the gold standard for the identification of the critical parts of the circuit. However, this is rarely accomplished, as most VTs are not hemodynamically tolerated to permit mapping during tachycardia. Other limitations include noninducibility of arrhythmia or nonsustained VT. This has led to the development of substrate mapping techniques during sinus rhythm, eliminating the need for prolonged periods of mapping during tachycardia. Recurrence rates following VT ablation are high; therefore, new mapping techniques for substrate characterization are required. Advances in catheter technology and especially multielectrode mapping of abnormal electrograms has increased the ability to identify the mechanism of scar-related VT. Several substrate-guided approaches have been developed to overcome this, including scar homogenization and late potential mapping. Dynamic substrate changes are mainly identified within regions of myocardial scar and can be identified as local abnormal ventricular activities. Furthermore, mapping strategies incorporating ventricular extrastimulation, including from different directions and coupling intervals, have been shown to increase the accuracy of substrate mapping. The implementation of extrastimulus substrate mapping and automated annotation require less extensive ablation and would make VT ablation procedures less cumbersome and accessible to more patients.

Arrhythmic risk stratification in ischemic, non-ischemic and hypertrophic cardiomyopathy: A two-step multifactorial, electrophysiology study inclusive approach

Annual arrhythmic sudden cardiac death ranges from 0.6% to 4% in ischemic cardiomyopathy (ICM), 1% to 2% in non-ischemic cardiomyopathy (NICM), and 1% in hypertrophic cardiomyopathy (HCM). Towards a more effective arrhythmic risk stratification (ARS) we hereby present a two-step ARS with the usage of seven non-invasive risk factors: Late potentials presence (≥ 2/3 positive criteria), premature ventricular contractions (≥ 30/h), non-sustained ventricular tachycardia (≥ 1episode/24 h), abnormal heart rate turbulence (onset ≥ 0% and slope ≤ 2.5 ms) and reduced deceleration capacity (≤ 4.5 ms), abnormal T wave alternans (≥ 65μV), decreased heart rate variability (SDNN < 70ms), and prolonged QT_c interval (> 440 ms in males and > 450 ms in females) which reflect the arrhythmogenic mechanisms for the selection of the intermediate arrhythmic risk patients in the first step. In the second step, these intermediate-risk patients undergo a programmed ventricular stimulation (PVS) for the detection of inducible, truly high-risk ICM and NICM patients, who will benefit from an implantable cardioverter defibrillator. For HCM patients, we also suggest the incorporation of the PVS either for the low HCM Risk-score patients or for the patients with one traditional risk factor in order to improve the inadequate sensitivity of the former and the low specificity of the latter.

Role of Scar and Border Zone Geometry on the Genesis and Maintenance of Re-Entrant Ventricular Tachycardia in Patients With Previous Myocardial Infarction

In patients with healed myocardial infarction, the left ventricular ejection fraction is characterized by low sensitivity and specificity in the prediction of future malignant arrhythmias. Thus, there is the need for new parameters in daily practice to perform arrhythmic risk stratification. The aim of this study is to identify some features of proarrhythmic geometric configurations of scars and border zones (BZ), by means of numerical simulations based on left ventricular models derived from post myocardial infarction patients. Two patients with similar clinical characteristics were included in this study. Both patients exhibited left ventricular scars characterized by subendo- and subepicardial BZ and a transmural BZ isthmus. The scar of patient #1 was significantly larger than that of patient #2, whereas the transmural BZ isthmus and the subdendo- and subepicardial BZs of patient #2 were thicker than those of patient #1. Patient #1 was positive at electrophysiologic testing, whereas patient #2 was negative. Based on the cardiac magnetic resonance (CMR) data, we developed a geometric model of the left ventricles of the two patients, taking into account the position, extent, and topological features of scars and BZ. The numerical simulations were based on the anisotropic monodomain model of electrocardiology. In the model of patient #1, sustained ventricular tachycardia (VT) was inducible by an S2 stimulus delivered at any of the six stimulation sites considered, while in the model of patient #2 we were not able to induce sustained VT. In the model of patient #1, making the subendo- and subepicardial BZs as thick as those of patient #2 did not affect the inducibility and maintenance of VT. On the other hand, in the model of patient #2, making the subendo- and subepicardial BZs as thin as those of patient #1 yielded sustained VT. In conclusion, the results show that the numerical simulations have an effective predictive capability in discriminating patients at high arrhythmic risk. The extent of the infarct scar and the presence of transmural BZ isthmuses and thin subendo- and subepicardial BZs promote sustained VT.

The challenge of optimising ablation lesions in catheter ablation of ventricular tachycardia

Radiofrequency catheter ablation has become an established treatment for ventricular tachycardia. The exponential increase in procedures has provided further insights into mechanisms causing arrhythmias and identification of ablation targets with the development of new mapping strategies. Since the definition of criteria to identify myocardial dense scar, borderzone and normal myocardium, and the description of isolated late potentials, local abnormal ventricular activity and decrementing evoked potential mapping, substrate-guided ablation has progressively become the method of choice to guide procedures. Accordingly, a wide range of ablation strategies have been developed from scar homogenization to scar dechanneling or core isolation using increasingly complex and precise tools such as multipolar or omnipolar mapping catheters. Despite these advances long-term success rates for VT ablation have remained static and lower in nonischemic than ischemic heart disease because of the more patchy distribution of myocardial scar. Ablation aims to deliver an irreversible loss of cellular excitability by myocardial heating to a temperatures exceeding 50°C. Many indicators of ablation efficacy have been developed such as contact force, impedance drop, force-time integral and ablation index, mostly validated in atrial fibrillation ablation. In ventricular procedures there is limited data and ablation lesion parameters have been scarcely investigated. Since VT arrhythmia recurrence can be related to inadequate RF lesion formation, it seems reasonable to establish robust markers of ablation efficacy.

Updating the Risk Stratification for Sudden Cardiac Death in Cardiomyopathies: The Evolving Role of Cardiac Magnetic Resonance Imaging. An Approach for the Electrophysiologist

The prevention of sudden cardiac death (SCD) in cardiomyopathies (CM) remains a challenge. The current guidelines still favor the implantation of devices for the primary prevention of SCD only in patients with severely reduced left ventricular ejection fraction (LVEF) and heart failure (HF) symptoms. The implantation of an implantable cardioverter-defibrillator (ICD) is a protective barrier against arrhythmic events in CMs, but the benefit does not outweigh the cost in low risk patients. The identification of high risk patients is the key to an individualized prevention strategy. Cardiac magnetic resonance (CMR) provides reliable and reproducible information about biventricular function and tissue characterization. Furthermore, late gadolinium enhancement (LGE) quantification and pattern of distribution, as well as abnormal T1 mapping and extracellular volume (ECV), representing indices of diffuse fibrosis, can enhance our ability to detect high risk patients. CMR can also complement electro-anatomical mapping (EAM), a technique already applied in the risk evaluation and in the ventricular arrhythmias ablation therapy of CM patients, providing a more accurate assessment of fibrosis and arrhythmic corridors. As a result, CMR provides a new insight into the pathological substrate of CM. CMR may help identify high risk CM patients and, combined with EAM, can provide an integrated evaluation of scar and arrhythmic corridors in the ablative therapy of ventricular arrhythmias.

Open chest epicardial and transapical endocardial substrate ablation for ventricular tachycardia with left ventricular aneurysm in a porcine model

BACKGROUND

Endo-epicardial radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) as a first-line strategy has been shown to improve outcomes. This study sought to evaluate the feasibility and validity of open-chest epicardial and transapical endocardial substrate ablation for VT with left ventricular aneurysm (LVA) applying to routine cardiac surgery.

METHODS

Porcine models of LVA with VT were developed and were divided into a study group (RFCA from the epicardium via direct-view and endocardium via transapical access) and a control group (endocardial RFCA via retrograde transaortic access). Substrate-based mapping and ablation targeting abnormal potentials were performed under thoracotomy. Outcomes, including procedural success and acute freedom from VT, were analysed.

RESULTS

Twenty-four of 35 (68.57%) acute myocardial infarction (AMI) pigs developed LVA with VT in a 6-week survival period and were randomly divided into a study group (n=12) and a control group (n=12). All animals in the study group successfully underwent endocardial mapping and ablation by transapical access. The scar size of the endocardium and the left ventricular chamber volume were similar in the two groups. Acute freedom from VT in the study group was remarkably superior to that in the control group (88.33% vs. 58.33%, p=0.04).

CONCLUSIONS

Combined, direct epicardial and transapical endocardial substrate mapping and ablation appeared to be feasible and effective for treating VT with LVA under thoracotomy.

Recommendations for the use of electrophysiological study: Update 2018

The field of cardiac electrophysiology has greatly developed during the past decades. Consequently, the use of electrophysiological studies (EPSs) in clinical practice has also significantly augmented, with a progressively increasing number of certified electrophysiology centers and specialists. Since Zipes et al published the Guidelines for Clinical Intracardiac Electrophysiology and Catheter Ablation Procedures in 1995, no official document summarizing current EPS indications has been published. The current paper focuses on summarizing all relevant data of the role of EPS in patients with different types of cardiac pathologies and provides up-to-date recommendations on this topic. For this purpose, the PubMed database was screened for relevant articles in English up to December 2018 and ESC and ACC/AHA Clinical Practice Guidelines, and EHRA/HRS/APHRS position statements related to the current topic were analyzed. Current recommendations for the use of EPS in clinical practice are discussed and presented in 17 distinct cardiac pathologies. A short rationale, evidence, and indications are provided for each cardiac disease/group of diseases. In conclusion, because of its capability to establish a diagnosis in patients with a variety of cardiac pathologies, the EPS remains a useful tool in the evaluation of patients with cardiac arrhythmias and conduction disorders and is capable of establishing indications for cardiac device implantation and guide catheter ablation procedures.

Surgical linear ablation for ventricular tachycardia with postinfarction ventricular aneurysm

BACKGROUND

Left ventricular aneurysm (LVA) might be an arrhythmogenic substrate. Endocardiectomy and cryoablation for ventricular tachycardia (VT) with LVA can cause extensive myocardial damage. We aimed to evaluate the feasibility of surgical radial linear ablation for VT with LVA guided by electrophysiological mapping.

MATERIALS AND METHODS

Porcine models of VT with LVA were developed. Endocardial and epicardial substrate mapping during sinus rhythm were performed under thoracotomy. Surgical radial linear ablation was achieved by a bipolar radiofrequency ablation device. Outcomes, including procedural success and acute freedom of VT, were analyzed.

RESULTS

Fifteen of 20 pigs developed LVA in a 6-wk survival period. A total of 28 sustained monomorphic VTs were initiated in 13 of 15 pigs (86.67%). The number of potential points captured from the endocardium and epicardium were 319 ± 45 and 358 ± 52 per animal, respectively. The ablative targets containing abnormal potentials were located largely on the border zone of LVA. Eight linear lesions from core to border zone of LVA were achieved per animal in a radial and even manner continuously, and ablation was repeated three times to transect border zone. The acute freedom of VT was 84.62%, P < 0.05.

CONCLUSIONS

Surgical linear endo-epicardial ablation seemed to be feasible in a porcine model with VT and LVA.

Analytic Reviews: Electrophysiologic Testing in the Intensive Care Unit

The role of electrophysiologic concepts and procedures in managing patients with potentially life-threatening ar rhythmias in the intensive care unit is discussed. These patients may be survivors of sudden cardiac arrest or myocardial infarction or may be admitted for syncope or sustained or nonsustained ventricular tachycardia. The value of electrophysiologic testing is discussed in terms of the distinction between wide QRS complex tachycardias that are supraventricular or ventricular in origin and those in which preexcitation syndromes may be important. Drug-induced ventricular arrhythmias are discussed, with specific emphasis on torsades de pointes. Finally, the use of His bundle recordings in pa tients with atrioventricular conduction disturbances is discussed. The methodology of electrophysiologic test ing, including stimulation protocols and interpretation of results, is described.

Surgery for ventricular tachycardia in patients undergoing surgical ventricular restoration: The Karolinska approach

This article presents a review on the efficacy of surgical ventricular restoration and direct surgery for ventricular tachycardia in patients with left ventricular aneurysm or dilated ischemic cardiomyopathy. The procedure includes a non-electrophysiologically guided subtotal endocardiectomy and cryoablation in addition to endoventricular patch plasty of the left ventricle. Coronary artery bypass surgery and mitral valve repair are performed concomitantly as needed. In our experience, this procedure yielded a 90% success rate in terms of freedom from spontaneous ventricular tachycardia, with an early mortality rate of 3.8%. A practical guide to the pre- and postoperative management of these patients is provided.

Surgery for ventricular tachycardia in patients undergoing surgical ventricular restoration

This article is a presentation of direct surgery for ventricular tachycardia in patients undergoing surgical ventricular restoration. The procedure includes a non-electrophysiologically guided subtotal endocardiectomy and cryoablation in addition to endoventricular patch plasty of the left ventricle. Coronary artery bypass surgery and mitral valve repair are performed concomitantly as needed. In our experience, this procedure yielded a 90% success rate in terms of freedom from spontaneous ventricular tachycardia, with an early mortality rate of 3.8%. Perioperative considerations and a short overview of the literature are presented.

Relationship Between Successful Ablation Sites and the Scar Border Zone Defined by Substrate Mapping for Ventricular Tachycardia Post-Myocardial Infarction

INTRODUCTION

It is unknown if identification of scar border zones by electroanatomical mapping correlates with successful ablation sites determined from mapping during ventricular tachycardia (VT) post-myocardial infarction (MI). We sought to assess the relationship between successful ablation sites of hemodynamically stable post-MI VTs determined by mapping during VT with the scar border zone defined in sinus rhythm.

METHODS AND RESULTS

Forty-six patients presenting with hemodynamically stable, mappable monomorphic VT post-MI and who had at least one such VT successfully ablated were prospectively included in the study. In each patient, VT was ablated by targeting regions during VT that exhibited early activation, +/- isolated mid-diastolic potentials, and concealed entrainment suggesting a critical isthmus site. Prior to ablation, a detailed sinus-rhythm CARTO voltage map of the left ventricle was obtained. A voltage <0.5 mV defined dense scar. Successful VT ablation sites were registered on the sinus voltage map to assess their relationship to the scar border zone. Of the 86 VTs, 68% were successfully ablated at sites in the endocardial border zone. The remaining VTs had ablation sites within the scar in (18%), in normal myocardium (4%), and on the epicardial surface (10%). There were no significant differences in VT recurrence amongst the different groups.

CONCLUSION

Successful ablation sites of hemodynamically stable, monomorphic VTs post-MI are often located in the scar border zone as defined by substrate voltage mapping. However, in a sizable minority, ablation sites are located within endocardial scar, epicardially, and even in normal myocardium.

Long-Term Outcomes After Cryoablation for Ventricular Tachycardia During Surgical Treatment of Anterior Ventricular Aneurysms

Intraoperative map-guided procedures have been widely advocated as the best surgical strategy for the treatment of ventricular tachycardia (VT), though favorable results have been reported with subendocardial resection without mapping. This study examined the very long-term results of encircling cryoablation without mapping during surgery for anterior left ventricular aneurysm complicated by VT. Between 1985 and 2003, this procedure was performed in 52 patients, 7 of whom (13.7%) were operated within 1 month of anterior myocardial infarction. Their mean age was 64.4 +/- 8.3 years and mean left ventricular ejection fraction was 31.7%+/- 9.5%. The overall hospital mortality was 1.9%. At 14 years, 86% of patients (95% CI: 75.4-96.6) were free from VT or sudden death. An implantable defibrillator was implanted in five patients (9.6%) during follow-up. The 14-year overall survival was 51.4% (95% CI: 33.8-72.4), and two patients (3.8%) underwent cardiac transplantation during follow-up. The main cause of late death was congestive heart failure in eight patients (40.0%). Favorable long-term results can be achieved with encircling cryoablation without mapping in patients undergoing surgery for anterior left ventricular aneurysm complicated by VT.

Management of postinfarct ventricular tachycardias

The clinical profile of patients with postinfarct VT has changed in the past two decades. Along with these changes, existing treatments have improved, and entirely new therapeutic approaches have been developed. The expanded range of treatment options has made postinfarct VT a less imposing clinical problem than it once was. Emerging therapies promise to make an even greater beneficial impact. The challenge in treating patients with postinfarct VT has changed from merely keeping patients alive to keeping up with innovations in therapy that can provide them with a better quantity and quality of life.

Linear ablation lesions for control of unmappable ventricular tachycardia in patients with ischemic and nonischemic cardiomyopathy

BACKGROUND

Conventional activation mapping is difficult without inducible, stable ventricular tachycardia (VT).

METHODS AND RESULTS

We evaluated 16 patients with drug refractory, unimorphic, unmappable VT. Nine patients had ischemic and 7 had nonischemic cardiomyopathy. All patients had implantable defibrillators and had experienced 6 to 55 VT episodes during the month before treatment. Patients underwent bipolar catheter mapping during baseline rhythm. The amount of endocardium with an abnormal electrogram amplitude was estimated using fluoroscopy in 3 patients and a magnetic mapping system (CARTO) in 13 patients. For the magnetic mapping, normal endocardium was defined by an amplitude >1.5 mV; this measurement was based on sinus rhythm maps in 6 patients who did not have structural heart disease. Radiofrequency point lesions extended linearly from the "dense scar," which had a voltage amplitude <0.5 mV, to anatomic boundaries or normal endocardium. To limit radiofrequency applications, 12-lead ECG during VT and pacemapping guided placement of linear lesions. No new antiarrhythmic drug therapy was added. The amount of endocardium demonstrating an abnormal electrogram amplitude ranged from 25 to 127 cm(2). A total of 8 to 87 radiofrequency lesions (mean, 55) produced a median of 4 linear lesions that had an average length of 3.9 cm (range, 1.4 to 9. 4 cm). Twelve patients (75%) have been free of VT during 3 to 36 months of follow-up (median, 8 months); 4 patients had VT episodes at 1, 3, 9, and 13 months, respectively. Only one of these patient had frequent VT.

CONCLUSIONS

Radiofrequency linear endocardial lesions extending from the dense scar to the normal myocardium or anatomic boundary seem effective in controlling unmappable VT.

Sodium pentobarbital reduces transmural dispersion of repolarization and prevents torsades de Pointes in models of acquired and congenital long QT syndrome

INTRODUCTION

Sodium pentobarbital is widely used for anesthesia in experimental studies as well as in clinics, and it is known to prevent the development of torsades de pointes (TdP) in in vivo models of the long QT syndrome (LQTS).

METHODS AND RESULTS

This study examines the effects of pentobarbital on transmural dispersion of repolarization (TDR) and induction of TdP in arterially perfused canine left ventricular wedge preparations in which transmembrane action potentials were simultaneously recorded from epicardial, M, and endocardial regions using floating glass microelectrodes together with a transmural ECG. d-Sotalol and ATX-II were used to mimic the LQT2 and LQT3 forms of congenital LQTS. Both d-sotalol (100 micromol/L, n = 6) and ATX-II (20 nmol/L, n = 6) preferentially prolonged the action potential duration (APD90) of the M cell, thus increasing in the QT interval and TDR, and leading to the development of spontaneous and stimulation-induced TdP. In the absence and presence of d-sotalol, pentobarbital (10, 20, and 50 microg/mL) prolonged the APD90 of epicardial and endocardial cells, and, to a lesser extent, that of the M cell, thus prolonging the QT interval but reducing TDR. In the ATX-II model, the effects of pentobarbital on the QT interval and APD90 were biphasic: 10 microg/mL pentobarbital further prolonged APD90 of epicardial and endocardial cells more than that of the M cell; 20 to 50 microg/mL pentobarbital abbreviated the APD90 of epicardial and endocardial cells less than that of the M cell, thus abbreviating the QT interval and markedly reducing TDR. Twenty to 50 microg/mL pentobarbital totally suppressed spontaneous as well as stimulation-induced TdP in both models

CONCLUSION

Our data indicate that pentobarbital reduces TDR in control and under conditions of congenital and acquired LQTS, and suggest that this mechanism may contribute to the ability of the anesthetic to prevent the development of spontaneous as well as stimulation-induced TdP under conditions mimicking LQT2, LQT3, and acquired (drug-induced) forms of the LQTS. The data also serve to illustrate that there are circumstances under which QT prolongation may not be arrhythmogenic.

Long-term results of visually guided left ventricular reconstruction as single therapy to treat ventricular tachycardia associated with postinfarction anteroseptal aneurysm

INTRODUCTION

Postinfarction ventricular tachycardia (VT), anteroseptal aneurysm, and ventricular dysfunction are commonly associated and predict a poor long-term prognosis. Surgical left ventricular reconstruction, which includes double plication of the anterior and septal wall, can improve ventricular function. This article analyzes the long-term efficacy of such a procedure to control recurrence of VT in a group of 50 consecutive patients.

METHODS AND RESULTS

The study group consisted of 50 consecutive patients operated on between December 1986 and December 1994. The group comprised 44 men and 6 women. The mean age was 56+/-11 years. All patients had spontaneous VT following an anterior myocardial infarction. Twenty-five patients had two or more episodes of VT (eight presented as cardiac arrest, nine as syncope). Coronary artery disease was limited to the left anterior descending artery in 27 patients. An anteroseptal aneurysm was present in 49 patients. All patients had VT induced by programmed ventricular stimulation before surgery, and left ventricular reconstruction was performed without intraoperative mapping in all cases. Total mortality, VT recurrence, and sudden death rate were the endpoints of the study. In-hospital mortality was 8%. Postoperative left ventricular ejection fraction improved from 0.38 to 0.50 (P<0.05). Only two patients had postoperative inducible VT. Overall survival, VT recurrence rate, and sudden death rate were 73%, 12%, and 10%, respectively, after a median follow-up period of 6.25 years (0 to 8 years).

CONCLUSION

Visually guided left ventricular reconstruction with septal and anterior wall plicature can be utilized effectively to treat recurrent VT associated with postinfarction anteroseptal aneurysm.

Large encircling cryoablation without mapping for ventricular tachycardia after anterior myocardial infarction: long-term outcome

OBJECTIVE

Map-guided procedures have been the accepted standard for ventricular tachycardia surgery. However, promising results of visually guided resections without mapping have been reported. The goal of this study was to evaluate the efficacy of large encircling cryoablation without mapping for ventricular tachycardia after anterior myocardial infarction.

METHODS

Between 1985 and 1996, this procedure, along with aneurysmectomy, was performed on 38 patients for malignant ventricular tachycardia. The mean interval between the operation and myocardial infarction was 59.2 months; 7 patients (18.4%) were operated on within 1 month of myocardial infarction. The mean patient age was 62.1 +/-7.3 years and the mean left ventricular ejection fraction was 29.0% +/-7.2%.

RESULTS

Hospital mortality was 2.6% (1 patient). The electrical success rate based on postoperative electrophysiologic studies was 94.5%. Overall electrical success rate was 89.1%. Freedom from ventricular tachycardia was 77% (95% CI 61%-94%) at both 5 and 7 years. Freedom from sudden cardiac death was 91% (95% CI 80%-100%) at both 5 and 7 years, with overall actuarial survivals at 5 and 7 years of 63% (95% CI 47%-80%) and 42% (95% CI 22%-63%), respectively. The main cause of late death was congestive heart failure in 62.6% of these patients.

CONCLUSIONS

One can achieve good results without intraoperative mapping in the treatment of patients with ventricular tachycardia after anterior myocardial infarction by using large encircling cryoablation.

Ventricular arrhythmia following successful myocardial revascularization: incidence, predictors and prevention

OBJECTIVES

We estimated the risk of sudden cardiac death (SCD), from a spontaneous episode of ventricular arrhythmia (VT/VF), after a successful surgical myocardial revascularization (coronary artery bypass grafting; CABG) procedure. Predictors of these events were identified, and long term benefits of the prophylactic regimes, that were used to control these events, were evaluated.

METHODS

We selected 8642 consecutive patients, who had undergone an isolated and first time CABG procedure, between 1/3/1980 and 1/3/1995. A standard hazard function model (1) was used for statistical analysis. Efficacy of the prophylactic regimes, was examined in a group of 350 high risk patients, with a preoperative left ventricular ejection fraction 30% or less, who were recently operated since 1/1/1988. Electrophysiologic (EP) guided prophylaxis was used in 92 (26%) patients, who had survived a documented episode of SCD, and remaining 258 patients were maintained on antiarrhythmic medication on an empirical basis. A sequential EP evaluation was performed, when indicated.

RESULTS

During an early phase of hazard, which mainly lasted for up to 3 months after CABG, incremental risk factors were preoperative LVEF 30% or less (P = 0.0007) and preoperative episodes of VT/VF (P = 0.04). This phase was followed by a constant phase with a low risk of the events, which merged into a slowly rising late phase after 6 years. EP guided prophylaxis, reduced the risk of SCD in high risk patients (P = 0.03). A sequential EP evaluation, helped to detect the problems of drug resistance and a cross over from non-sustained to sustained runs of VT/VF.

CONCLUSIONS

Despite a successful CABG surgery, risk of VT/VF persists. A routine EP evaluation before and after a CABG procedure is recommended in all patients with a poor left ventricular function.

Can catheter ablation in cardiac arrest survivors prevent ventricular fibrillation recurrence?

Ventricular tachyarrhythmias are the most common cause for sudden cardiac death. The success of catheter ablation for supraventricular tachycardias led to the supposition that ablation could also be used in the treatment of ventricular tachycardias. Despite the promising results in bundle branch reentry and some forms of idiopathic ventricular tachycardia, the success rate in patients with coronary artery disease is still low. There is hope that new approaches to reliably localize the critical region of the tachycardia and new ablation techniques to create larger areas of injury may lead to a wider application of ablation therapy in the treatment of ventricular tachycardia. Survivors of cardiac arrest typically have more rapid and unstable arrhythmias than patients with sustained ventricular tachycardia, and these rapid arrhythmias frequently degenerate into ventricular fibrillation. The instability of the arrhythmia makes it impossible to localize the arrhythmia origin with current mapping techniques. Experimental and clinical data, however, suggest that these arrhythmias also frequently start from a localized area of electrical activation. With developments in mapping techniques and energy delivery, catheter ablation may soon become a feasible therapeutic approach in some patients with unstable arrhythmias. The article discusses the prerequisites for this approach and suggests the patients who may be appropriate candidates for this technique.

Arrhythmogenic ventricular aneurysms unrelated to coronary artery disease

Malignant ventricular tachycardia occurs most frequently in patients with coronary artery disease who have had a previous myocardial infarction and in whom a ventricular aneurysm subsequently develops in the scarred section of myocardium. Ventricular tachycardia in the presence of normal coronary arteries and a left ventricular aneurysm is unusual and can be refractory to medical therapy. We retrospectively reviewed our experience of 10 patients treated at our institution from 1983 to 1993. Age ranged from 22 to 76 years, and all patients presented with sustained ventricular tachycardia. All patients underwent complete electrophysiologic testing. Cardiac catheterization was performed in 9 patients, and each had normal coronary artery anatomy without evidence of significant fixed lesions. A left ventricular aneurysm, diagnosed by either echocardiography, thoracic cine computed tomography or magnetic resonance imaging, or ventricular angiography was present in all patients. Ventricular tachycardia could not be suppressed pharmacologically in 7 of 10 patients using multiple agents including procainamide, quinidine, flecanide, tocainide, propaferone, and amiodarone. Six patients were treated surgically by intraoperative electrophysiologic mapping, endocardial resection of foci, and left ventricular aneurysmectomy. An implantable cardiac defibrillation device was implanted in 2 patients. One patient died on the second postoperative day after simultaneous mapping -guided aneurysmectomy and implantable cardioverter defibrillator placement. There was one late postoperative death. All other surgically treated patients had postoperative electrophysiologic studies demonstrating no inducible ventricular tachycardia, and these patients remain without antiarrhythmic therapy in follow-up extending from 29 to 86 months (mean, 56 months).(ABSTRACT TRUNCATED AT 250 WORDS)

Anterior septal coronary artery infarction in the canine: a model of ventricular tachycardia with a subendocardial origin. Ablation and activation sequence mapping

BACKGROUND

In humans, chronic ventricular tachycardia (VT) is usually associated with myocardial infarcts that involve the interventricular septum. In an effort to more closely mimic the anatomic substrate that gives rise to chronic VT in humans, we developed a canine model of VT in which the anterior septal coronary artery was ligated. The site of earliest activation, the subsequent activation sequence, and the mechanism of VT associated with the resultant ventricular septal infarct was then evaluated to determine if this model accurately reflected the characteristics of human VT.

METHODS AND RESULTS

Seventeen dogs underwent occlusion-reperfusion ventricular septal infarcts. Four to 7 days later, electrophysiological studies were performed. VT was initiated by programmed electrical stimulation and terminated by pacing at a cycle length of 50% to 75% of the VT cycle length. Electrophysiological studies were performed using a 256-channel mapping system. A total of 15 VT morphologies were mapped in 9 animals. Fourteen of 15 morphologies had septal subendocardial sites of earliest activation and 1 had a septal midwall site of earliest activation. VT ablation was performed using a nitrous oxide cryoprobe and confirmed the site of earliest activation by subsequently rendering VT noninducible. Electrophysiological studies demonstrated four distinct VT activation sequences: (1) circular reentrant (n = 7), (2) concentric spread (n = 5), (3) figure-of-eight (n = 2), and (4) septal midwall (n = 1).

CONCLUSIONS

This canine model of ventricular septal infarction produces VTs with sites of earliest activation and activation sequences similar to those in humans. A reentrant mechanism as the basis of these arrhythmias is supported by the following observations: (1) all VT was initiated and terminated with programmed electrical stimulation; (2) VT activation sequences were consistent with reentry; and (3) precise interruption of the sequence terminated the VT and rendered it noninducible.

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)

Direct operation versus ICD therapy for ischemic ventricular tachycardia

Now that the implantable cardioverter defibrillator is available as a therapeutic option for the management of ventricular tachycardia (VT), some argue that there no longer should be a role for direct surgical intervention for this malignant arrhythmia. Rebuttal of this argument is difficult for the following reasons: (1) there are many patients who are candidates for implantable cardioverter defibrillator therapy but not for direct VT operation, and thus direct comparisons of the two therapies is difficult; (2) implantable cardioverter defibrillator therapy by definition is palliative, but a VT operation is curative in most instances; (3) in many electrophysiologic triage algorithms, implantation of a cardioverter defibrillator and VT operation are employed as alternative, not competitive, therapies, again making direct comparisons difficult; and (4) probably most importantly, there are misconceptions in the literature regarding the risks and benefits of direct VT surgical procedures as they are currently performed. In this brief review, we examine the currently available data on both sides of this argument.

Reflections on definitive surgical treatment of postinfarction ventricular tachycardia

The past 15 years have witnessed a substantial commitment to the understanding and surgical cure of postinfarction ventricular tachycardia, and the results of treatment have steadily improved. However, outside influences have had a negative impact on the use of this modality. With the widespread availability of implantable defibrillators, this has become an attractive alternative therapy to the sometimes difficult definitive surgical treatment. Meanwhile, early thrombolytic therapy for the management of evolving myocardial infarctions has been found to create a postinfarction electrical substrate that does not appear to be arrhythmogenic. As a result, clinical efforts to develop and refine definitive ventricular tachycardia surgical treatments have all but ceased. The intent of this article is to review the events that took place in this apparently transient era.

From fisherman to fibrillation: an unbroken line of progress

The modern era of cardiac arrhythmia surgery was initiated by Dr Will C. Sealy in May 1968, when he performed the first successful surgical division of an accessory pathway for the treatment of the Wolff-Parkinson-White syndrome. During the subsequent 25 years, arrhythmia operations evolved through a series of innovative surgical procedures capable of curing essentially all refractory clinical arrhythmias. The lessons learned during the development of these surgical procedures ultimately led to the refinement and eventual success of less invasive catheter techniques that have now replaced most of these surgical techniques. The surgical experience gained during these years also made possible the current surgical procedure that is used to treat the most complex, and the most common, of all cardiac arrhythmias, atrial fibrillation. Few areas of any specialty are as clearly defined as the unbroken line of progress that extends from Dr Sealy's first procedure in 1968 to the successful surgical treatment of atrial fibrillation in 1994.

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.

Future developments in implantable cardioverter defibrillators: the optimal device

Despite recent therapeutic advances, SCD remains the leading cause of mortality in industralized nations. The most frequent cause of SCD is ventricular tachyarrhythmias in the setting of advanced structural heart disease due to chronic coronary heart disease or idiopathic dilated cardiomyopathy. Although high-risk groups can be prospectively identified, attempts at primary prevention have been largely unsuccessful. Effective treatment strategies for SCD survivors include antiarrhythmic drug therapy guided by programmed stimulation, endocardial resection, and ICDs. Device therapy has proven extremely effective in preventing recurrent sudden death from ventricular tachyarrhythmias. Widespread application of ICD therapy, perhaps even to include members of high-risk populations that have not experienced cardiac arrest, will depend on many factors including the demonstration that device therapy improves total mortality, not just arrhythmia-related mortality, reduction in cost, and improvements in the devices themselves. Some of the important characteristics of the optimal ICD of the future are nonthoracotomy lead placement; subpectoral generator placement; multiprogrammable, tiered therapy; improved diagnostic specificity, whether based on electrogram or hemodynamic-sensing algorithms; improved integration of brady- and tachy-sensing systems; and enhanced electrogram storage capability with trans-telephonic retrieval of electrogram recordings. The creation of this ideal ICD will obviously require continued technological advances; however, given the tremendous improvements realized over the first three generations of ICD systems, optimism for the future seems warranted.

Regional wall motion analysis predicts survival and functional outcome after subendocardial resection in patients with prior anterior myocardial infarction

BACKGROUND

Subendocardial resection is an established surgical technique for the treatment of ventricular tachycardia associated with prior myocardial infarction. Preoperative factors predictive of survival and functional outcome after surgery have not been completely characterized. We hypothesized that a quantitative assessment of regional wall motion would be a sensitive predictor of both survival and functional outcome after subendocardial resection. This was retrospectively tested in a group of 80 patients with prior anterior myocardial infarction who had undergone subendocardial resection for sustained ventricular tachycardia at out institution.

METHODS AND RESULTS

Centerline chord motion analysis was used to derive a wall motion score from the preoperative contrast right anterior oblique ventriculogram. Multivariate analysis revealed wall motion score to be a significant independent predictor of both long-term survival (p < 0.01) and New York Heart Association (NYHA) functional class I or II status at 6 months (p < 0.01) and at 24 months (p < 0.001) after surgery. Patients with a wall motion score of > 16%, compared with patients with a wall motion score of < or = 16%, had a better 5-year actuarial survival (74% versus 45%, p = 0.02) and were more likely to be NYHA class I or II at 6 months (87% versus 58%, p < 0.01) and at 24 months (82% versus 34%, p < 0.0001) after subendocardial resection.

CONCLUSIONS

A wall motion score derived from centerline chord motion analysis is a sensitive predictor of survival and functional outcome after subendocardial resection. Patients with a wall motion score of > 16% have an excellent prognosis after subendocardial resection. In contrast, patients with a wall motion score of < or = 16% have a poorer outcome and should be considered candidates only if other forms of therapy have failed or are unavailable.

Effect of ventriculotomy on postinfarction ventricular tachycardia in a canine model

The antiarrhythmic efficacy of ventriculotomy without further resection or ablation was evaluated in 15 dogs with reliably inducible ventricular tachycardia after experimental myocardial infarction. The dogs were placed on cardiopulmonary bypass and assigned to one of two treatment groups: (1) cardiopulmonary bypass only (control) - 5 dogs, (2) ventriculotomy through the infarct scar - 10 dogs. The effects on induction of ventricular tachycardia were evaluated 2 and 4 weeks postoperatively and infarct histology was examined at the termination of the experiment. All of the control dogs maintained inducible ventricular tachycardia postoperatively. In contrast, ventriculotomy abolished arrhythmia induction in 6 of 10 dogs (p < 0.05). Ventriculotomy resulted in destruction of the surviving subepicardial myocardium overlying the infarct, which is a feature of arrhythmogenic areas in this model of postinfarction ventricular tachycardia. In conclusion, inducibility of ventricular tachycardia in this canine model of myocardial infarction is unaffected by thoracotomy and cardiopulmonary bypass, and is therefore well suited to investigation of surgical antiarrhythmic interventions. Ventriculotomy results in subepicardial scarring and is significantly antiarrhythmic. This effect should be taken into account when evaluating any adjunctive procedure in this model.

Predictors of surgical mortality and long-term results of endocardial resection for drug-refractory ventricular tachycardia

The results of surgical therapy performed in 51 consecutive patients with ventricular tachycardia were reviewed to determine short- and long-term predictors of success of such therapy in preventing recurrences of life-threatening ventricular arrhythmias. Of 41 patients (80%) who survived surgery, 40 had postoperative programmed stimulation and, of these patients, 78% (n = 31) had no inducible ventricular tachycardia on no antiarrhythmic therapy. This group had a very low incidence of arrhythmia recurrence, with only one nonfatal episode of ventricular tachycardia after a mean follow-up of 41 +/- 30 months. In contrast, two of the nine patients (22%) who had inducible arrhythmias postoperatively had cardiac arrest (p = 0.12). Multivariate analysis identified two significant predictors of perioperative mortality in our patients: increased duration of cardiopulmonary bypass time and increased baseline pulmonary capillary wedge pressure. It is concluded that (1) patients who do not have inducible ventricular tachycardia after arrhythmia surgery have a very low incidence of recurrent arrhythmia and (2) prolonged time of cardiopulmonary bypass and increased pulmonary capillary wedge pressure are predictive of perioperative mortality.

Long-term surgical results in sudden death syndrome associated with cardiac dysfunction after myocardial infarction

To evaluate the surgical results in patients with inducible ventricular tachyarrhythmias due to coronary disease and left ventricular dysfunction, the authors reviewed their experience in 170 patients who had survived one or more cardiac arrests after myocardial infarction and were unresponsive to drug therapy based on electrophysiologic studies (EPS). There were nine operative deaths (5%). Based on intraoperative EPS, surgical remodeling of left ventricular dysfunction (aneurysm resection, infarct debulking, and septal reinforcement) with map-guided cryoablation and coronary artery bypass graft was performed in 34 patients (group A), and left ventricular remodeling and coronary artery bypass graft without guided endocardial resection was performed in 25 patients (group B). Forty-three patients (group C) had coronary artery bypass graft with implantation of an automatic implantable cardioverter defibrillator (AICD). Group D (68 patients) received AICD only. After operation, based on EPS results, four patients in group A (12%) and three patients in Group B (15%) required AICD implantation. Overall survival at 6 years was 65%, 48%, 85%, and 58% in patient groups A, B, C, and D, respectively (p = not significant). During follow-up in group A patients, none died suddenly and none needed AICD. In group B, two patients required AICD 3 and 5 years later, and five patients died suddenly. The incidence of sudden death was 2.3%/patient/year and 3.5%/patient/year after AICD implantation (groups C and D). At 6 years, cardiac-event-free survival was 80% and 70% for groups A and B and 38% and 24% for groups C and D, respectively (p less than 0.001). Patients receiving map-guided ablative procedures had significantly improved cardiac-event-free survival rates.