Surgical treatment of arrhythmias

False Tendons in the Left Ventricle: Implications for Successful Ablation of Left Posterior Fascicular Tachycardias

BACKGROUND

The anatomical substrate for left posterior fascicular ventricular tachycardia (LPF-VT) is still unclear.

OBJECTIVES

The purpose of this study is to describe the endocavitary substrate of the re-entrant loop of LPF-VT.

METHODS

A total of 26 consecutive patients with LPF-VT underwent an electrophysiology study and radiofrequency ablation.

RESULTS

Intracardiac echocardiography imaging observed a 100% prevalence of false tendons (FTs) at the left posterior septal region in all patients, and 3 different types of FTs could be classified according to their location. In 22 patients, a P1 potential could be recorded via the multielectrode catheter from a FT. In 4 patients without a recorded P1 during LPF-VT, the earliest P2 potentials were recorded from a FT in 3 patients, and from a muscular connection between 2 posteromedial papillary muscles in 1 patient. Catheter ablation focused on the FTs with P1 or earliest P2 (in patients without P1) was successful in all 26 patients. After 19 ± 8.5 months of follow-up, no patients had recurrence of LPF-VT.

CONCLUSIONS

FTs provide an electroanatomical substrate for LPF-VT and a "culprit FT" may be identified as the critical structure bridging the macro-re-entrant loop. Targeting the "culprit FT" is a novel anatomical ablation strategy that results in long-term arrhythmia-free survival.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

High prevalence of false chordae tendinae in patients without left ventricular tachycardia

BACKGROUND

Left ventricular (LV) false chordae tendinae (false chords) have been implicated as a source of idiopathic left (IL) ventricular tachycardia (VT). However, it is unknown whether pretest bias contributes to an apparent association with disease. The purpose of this study was to determine the prevalence of false chords on direct inspection of the LV endocardium.

METHODS

In a prospective series, 75 hearts were examined to identify and characterize false chords, including 20 specimens examined at autopsy and 55 consecutive patients undergoing mitral valve surgery. Medical records were reviewed for history of VT, including ILVT.

RESULTS

Of 75 patients whose hearts were studied, none had a history of ILVT and only 5 had a history of any VT. False chords were present in 34 of 75 (45%) hearts, including 13 of 20 (65%) at postmortem and 21 of 55 (38%) examined at surgery (P = 0.07). The prevalence of false chords was not different among patients with (3 of 5 [60%]) versus those without (31 of 70 [44% p = 0.65]) a history of VT (P = 0.65).

CONCLUSIONS

In this prospective anatomic series, the prevalence of LV false chords on autopsy and surgical inspection was approximately 45% among patients without ILVT. Previously reported associations of false chords with ILVT likely underestimated the prevalence of false chords in a normal population.

Idiopathic Ventricular Tachycardia: Diagnosis and Management

Idiopathic ventricular tachycardia (VT) is an uncommon form of VT that is seen in patients without structural heart disease. It is commonly seen in young patients and usually has a benign course. Recent studies have delineated the mechanisms and anatomical locations of this form of VT. Recognition of various forms of idiopathic VT based on characteristic QRS morphology from the 12-lead electrocardiogram (ECG) has important prognostic and therapeutic implications. The understanding of the mechanisms of idiopathic VT has led to the use of specific antiarrhythmic drugs targeting particular arrhythmias. Recent technological advances in the field of mapping and catheter ablation have led to a suitable alternative to drug therapy with a very high cure rate. This review describes the clinical features, ECG recognition, and management of idiopathic monomorphic VT.

Ventricular arrhythmias in normal hearts

Idiopathic ventricular tachycardia (VT) is characterized by two predominant forms. The most common form originates from the right ventricular outflow tract and presents as repetitive monomorphic VT or exercise-induced VT. The tachycardia is adenosine sensitive and is thought to be because of cAMP-mediated triggered activity. The other major form of idiopathic VT is owing to verapamil-sensitive intrafascicular re-entrant tachycardia, which most often originates in the region of the left posterior fascicle. Both forms of idiopathic VT can be readily treated with radiofrequency catheter ablation.

Entrance site of the slow conduction zone of verapamil-sensitive idiopathic left ventricular tachycardia: evidence supporting macroreentry in the Purkinje system

The entrance site of the slow conduction zone was identified by entrainment study in an 18 year-old woman with verapamil-sensitive idiopathic left ventricular tachycardia. Radiofrequency catheter ablation at this site eliminated the tachycardia. The entrance site was at a mid-septal location and was more than 2 cm away from the exit site. Electrophysiologic findings suggested macroreentry in the Purkinje system as the mechanism of idiopathic left ventricular tachycardia.

Mechanisms of idiopathic left ventricular tachycardia

Idiopathic left ventricular tachycardia (ILVT) differs from idiopathic right ventricular outflow tract (RVOT) tachycardia with respect to mechanism and pharmacologic sensitivity. ILVT can be categorized into three subgroups. The most prevalent form, verapamil-sensitive intrafascicular tachycardia, originates in the region of left posterior fascicle of the left bundle. This tachycardia is adenosine insensitive, demonstrates entrainment, and is thought to be due to reentry. The tachycardia is most often ablated in the region of the posteroinferior interventricular septum. A second type of ILVT is a form analogous to adenosine-sensitive RVOT tachycardia. This tachycardia appears to originate from deep within the interventricular septum and exits from the left side of the septum. This form of VT also responds to verapamil and is thought to be due to cAMP-mediated triggered activity. A third form of ILVT is propranolol sensitive. It is neither or initiated or terminated by programmed stimulation, does not terminate with verapamil, and is transiently suppressed by adenosine, responses consistent with an automatic mechanism. Recognition of the heterogeneity of ILVT and its unique characteristics should facilitate appropriate diagnosis and therapy in this group of patients.

Ambulatory monitoring uncorrected for placebo overestimates long-term antihypertensive action. Systolic Hypertension in Europe (SYST-EUR) Trial Investigators

This study compares blood pressure (BP) changes during active antihypertensive treatment and placebo as assessed by conventional and ambulatory BP measurement. Older patients (> or = 60 years, n=337) with isolated systolic hypertension by conventional sphygmomanometry at the clinic were randomized to placebo or active treatment consisting of nitrendipine (10 to 40 mg/d), with the possible addition of enalapril (5 to 20 mg/d) and/or hydrochlorothiazide (12.5 to 25 mg/d). At baseline, clinic systolic/diastolic BP averaged 175/86 mm Hg and 24-hour and daytime ambulatory BPs averaged 148/80 and 154/85 mm Hg, respectively. After 13 months (median) of active treatment, clinic BP had dropped by 22.7/7.0 mm Hg and 24-hour and daytime BPs by 10.5/4.5 and 9.7/4.3 mm Hg, respectively (P<.001 for all). However, clinic (9.8/1.6 mm Hg), 24-hour (2.1/1.1 mm Hg), and daytime (2.9/1.0 mm Hg) BPs decreased also during placebo (P<.05, except for daytime diastolic BP); these decreases represented 43%/23%, 20%/24%, and 30%/23% of the corresponding BP fall during active treatment. After subtraction of placebo effects, the net BP reductions during active treatment averaged only 12.9/5.4, 8.3/3.4, and 6.8/3.2 mm Hg for clinic, 24-hour, and daytime BPs, respectively. The effect of active treatment was also subject to diurnal variation (P<.05). Changes during placebo in hourly systolic and diastolic BP means amounted to (median) 21% (range, -1% to 42%) and 25% (-3% to 72%), respectively, of the corresponding changes during active treatment. In conclusion, expressed in millimeters of mercury, the effect of antihypertensive treatment on BP is larger with conventional than with ambulatory measurement. Regardless of whether BP is measured by conventional sphygmomanometry or ambulatory monitoring, a substantial proportion of the long-term BP changes observed during active treatment may be attributed to placebo effects. Thus, ambulatory monitoring uncorrected for placebo or control observations, like conventional sphygmomanometry, overestimates BP responses in clinical trials of long duration.

Anatomic substrate for idiopathic left ventricular tachycardia

BACKGROUND

Idiopathic left ventricular tachycardia (ILVT) characterized by QRS complexes with right bundle-branch block (RBBB) morphology and left axis deviation is a distinct clinical syndrome that also demonstrates a characteristic response to verapamil and inducibility from the atrium in patients without structural heart disease. A false tendon has been described in the left ventricle in a patient with ILVT in whom surgical resection of the false tendon resulted in cure. We hypothesized that the false tendon is responsible for the genesis of similar ventricular tachycardia (VT) in others.

METHODS AND RESULTS

We performed transthoracic (TTE) and/or transesophageal (TEE) two-dimensional echocardiograms in 15 patients undergoing catheter ablation for ILVT. There were 12 men and 3 women (mean age, 31 +/- 12 years, with average symptom duration of 11 +/- 9 years). The mean VT cycle length was 360 +/- 70 ms, and all had RBBB morphology with left axis deviation. Cardiac chamber sizes, left ventricular wall thickness, and wall motion were normal in all ILVT patients. TTE and/or TEE demonstrated a false tendon extending from the posteroinferior left ventricular free wall to the left ventricular septum in all ILVT patients. The false tendons were thick (> or = 2 mm maximal thickness) in 5 patients and thin (< 2 mm maximal thickness) in 10 patients. We compared ILVT patients with a control group of 671 consecutive patients referred for echocardiography for other reasons. The mean age for the control group was 42 years. A false tendon was seen in the left ventricle in 34 of 671 (5%). In the control group patients with a false tendon, 2 patients had a history of VT (left bundle-branch block morphology) and 1 had ventricular fibrillation. The false tendons in the control patients were also oriented transversely across the ventricular cavity but were somewhat thinner (< 2 mm maximal thickness in 32 of 34 patients). Catheter ablation with the use of radiofrequency and/or direct current applied to the posteroapical septum resulted in cure in 14 of 15 patients.

CONCLUSIONS

A false tendon extending from the posteroinferior left ventricle to the septum is a consistent finding in patients with ILVT and probably is responsible for this unique arrhythmia. The mechanism by which the false tendon precipitates tachycardia is speculative, but possibilities include conduction through the false tendon or by producing stretch in the Purkinje fiber network on the interventricular septum.

Characteristics and radiofrequency ablation therapy of intermediate septal accessory pathway

Fourteen patients (5%) with an intermediate septal accessory pathway were identified among 283 consecutive patients with the Wolff-Parkinson-White syndrome who had electrophysiologic study and radiofrequency ablation therapy. Nine were women and 5 were men (mean age 33 +/- 13 years). The resting electrocardiogram showed ventricular preexcitation in 8 patients and normal PR interval in 6. Anterograde and retrograde mapping studies revealed that the accessory pathway was para-Hisian in 11 patients and paranodal in 3. The accessory pathway was successfully ablated in 10 patients (9 para-Hisian and 1 paranodal) and damaged in 1 (para-Hisian). Treatment of 3 patients was complicated by transient atrioventricular (AV) block, of 1 by intermittent second-degree AV block, and of another by permanent complete AV block requiring implantation of a permanent pacemaker. Six patients underwent a follow-up electrophysiologic study 84 +/- 55 days after ablation; none had induction of tachycardia even after isoproterenol infusion. It is concluded that radiofrequency ablation therapy for intermediate septal accessory pathway is feasible. However, the success rate is only modest (71%), whereas complications with heart block (36%) or complete right bundle branch block (29%) are high. Thus, the procedure should be reserved for patients with life-threatening or troublesome symptomatic tachyarrhythmias.

Localization of the site of origin of postinfarction ventricular tachycardia by endocardial pace mapping. Body surface mapping compared with the 12-lead electrocardiogram

BACKGROUND

The purpose of this study was to assess the value of body surface mapping and the standard 12-lead ECG in localizing the site of origin of postinfarction ventricular tachycardia (VT) during endocardial pace mapping of the left ventricle.

METHODS AND RESULTS

Simultaneous recordings of 62-lead body surface QRS integral maps and scalar 12-lead ECG tracings were obtained in 16 patients with prior myocardial infarction during a total of 26 distinct VT configurations and during subsequent left ventricular catheter pace mapping at 9 to 24 different endocardial sites. Anatomic pacing site locations were computed by means of a biplane cineradiographic method and plotted on a polar projection of the left ventricle. The QRS integral map and the QRS complexes of the 12 standard leads of each VT morphology obtained in a particular patient were compared independently with the different paced QRS integral maps and paced QRS complexes of the 12-lead ECG generated in that same patient. The stimulus site locations of the best matching paced QRS integral map and paced QRS complexes of the 12-lead ECG were indicated on the polar projection and subsequently compared with the endocardial location of the corresponding site of VT origin identified during intraoperative (surgical ablation) or catheter activation sequence mapping (catheter ablation). The localization resolution of pace mapping was established separately for each electrocardiographic technique by computing the size of endocardial areas with similar morphological features of the QRS complex. Pace mapping advocated with body surface mapping or the 12-lead ECG enabled adequate reproduction of the VT QRS morphology in 24 of 26 VTs (92%) and 25 of 26 VTs (96%), respectively. Activation sequence mapping identified the site of origin in 12 of 26 previously observed VT configurations (46%). Ten and 11 VTs were localized by activation sequence mapping and pace mapping combined with body surface mapping or the 12-lead ECG, respectively. Pace mapping applied with body surface mapping identified the site of origin correctly (distance < or = 2 cm) in 8 of 10 compared VTs (80%); an adjacent site (distance between 2 and 4 cm) or a disparate site (distance > or = 4 cm) was identified in the remaining 2 of 10 VTs (20%). Pace mapping used with the 12-lead ECG localized the site of origin correctly in 2 of 11 VTs (18%); the site of origin was identified correctly next to an additional adjacent site in 5 of 11 VTs (55%); and an adjacent site or a disparate site was found in 1 of 11 VTs (9%) and 2 of 11 VTs (18%), respectively. The difference in localization accuracy of both electrocardiographic techniques was statistically significant (P = .02). The mean size of endocardial areas where a comparable QRS morphology was obtained during pace mapping was 6.0 +/- 4.5 cm2 with the application of body surface mapping and 15.1 +/- 12.0 cm2 with the use of the 12-lead ECG.

CONCLUSIONS

These results demonstrate that application of the 62-lead instead of the 12-lead ECG during endocardial pace mapping enhances the localization resolution of this mapping technique and enables more precise identification of the site of arrhythmogenesis in the majority of compared postinfarction VT episodes.

Effects of coronary artery bypass grafting on ventricular arrhythmias: results with electrophysiological testing and long-term follow-up

Myocardial revascularization was performed in 56 patients with coronary artery disease who presented with ventricular tachycardia (VT) (n = 39) or ventricular fibrillation (n = 17). There were 46 men and 10 women, aged 65 +/- 10 years. Three vessel (n = 42) or left main disease (n = 4) was present in 82%. Left ventricular ejection fraction averaged 36% +/- 11%. Electrophysiological studies were performed preoperatively in all patients; 50 (89%) had inducible ventricular arrhythmias. Sustained monomorphic VT was induced in 40 patients (cycle length 284 +/- 61 msec). Reproducible symptomatic nonsustained VT was induced in four patients and ventricular fibrillation in six patients, while six patients had no inducible arrhythmia. Preoperatively the patients with inducible VT failed 3.3 +/- 1.2 drug trials during electrophysiological studies. In addition to coronary bypass, 22 patients also received an automatic implantable cardioverter defibrillator (ICD), 26 patients received prophylactic ICD patches, and 1 patient had resection of a false aneurysm. There were no perioperative deaths. Postoperative electrophysiological studies were performed in all 56 surgical survivors. Ventricular tachyarrhythmia could not be induced in the six patients who had no inducible VT preoperatively and in 13 of 40 (33%) with preoperatively inducible sustained VT or in 19 of 50 (38%) patients with any previously inducible ventricular arrhythmia, thus a total of 25 patients (45%) had no inducible VT postoperatively. Of the remaining, 11 patients were treated with antiarrhythmic drugs alone, 11 had already received an ICD (combined with drugs in 7), and another 9 received the ICD postoperatively (combined with drugs in 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of left ventricular cryolesions created by liquid nitrogen and nitrous oxide

OBJECTIVES

This study was designed to compare the cryosurgical lesions produced by liquid nitrogen (-196 degrees C) and nitrous oxide (-76 degrees C).

BACKGROUND

Cryosurgical ablation is a useful method of arrhythmia surgery, but information on the dimensions of cardiac lesions produced by modifying cryoprobe temperature is limited.

METHODS

We compared the dimensions, volumes and electrophysiologic effects of cryolesions created by a liquid nitrogen cryoprobe (Group I) and a nitrous oxide cryoprobe (Group II) on the left ventricular myocardium in the beating canine heart. Exposure time was compared at 1, 2, 3 and 4 min. In each of 18 dogs, two to four lesions were created on the left ventricle and analyzed: 35 lesions created with use of the nitrous oxide cryoprobe and 30 lesions created with the liquid nitrogen cryoprobe. Lesions were measured at the time of induced death 6 weeks postoperatively and assessed by tissue staining with the Masson trichrome technique.

RESULTS

The volumes (mm3) of the cryolesions created by the liquid nitrogen cryoprobe were significantly larger (p < 0.05) than those of lesions created by nitrous oxide: 826 +/- 163 versus 493 +/- 197 at 1 min; 1,101 +/- 327 versus 666 +/- 185 at 2 min; 1,356 +/- 318 versus 787 +/- 258 at 3 min and 1,735 +/- 534 versus 923 +/- 376 at 4 min.

CONCLUSIONS

Decreasing the temperature of the cryoprobe by using liquid nitrogen increases the volume of the lesions. Programmed electrical stimulation before and 6 weeks after cryoablation indicated no arrhythmogenicity.

Usefulness of predischarge electrophysiologic study in predicting late outcome after surgical ablation of the accessory pathway in the Wolff-Parkinson-White syndrome

A predischarge electrophysiologic study was performed in 113 patients with the Wolff-Parkinson-White (WPW) syndrome who had undergone surgical ablation of the accessory pathway. The study was performed 5 to 20 (mean 10 +/- 3) days after surgery. There were 82 male and 31 female patients (aged 4 to 58 years, mean 36 +/- 13). Sixty-one patients (54%) had manifest, 52 (46%) had concealed and 12 (11%) had multiple accessory pathways. All but 1 patient had atrioventricular reentrant tachycardia incorporating single or multiple accessory pathways during the control electrophysiologic study. The accessory pathways were located in the left ventricular free wall in 60% of cases, right ventricular free wall in 22%, posteroseptum in 13%, and anteroseptum in 5%. The predischarge electrophysiologic study showed that the accessory pathway was capable of anterograde and retrograde conductions in 4 patients (all with manifest WPW syndrome). Four patients showed induction of supraventricular tachycardia, including 2 with atrioventricular reentrant tachycardia, and 2 with atrioventricular nodal reentrant tachycardia. Recurrence of supraventricular tachycardia was noted in 5 patients during a follow-up of 28 +/- 26 months. Of these 5 patients, 2 had inducible and 3 had no inducible supraventricular tachycardia during the predischarge electrophysiologic study.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of accessory pathways in Wolff-Parkinson-White syndrome by high-resolution magnetocardiographic mapping

Fifteen patients with Wolff-Parkinson-White syndrome were studied with standard 12-lead electrocardiogram, invasive electrophysiologic study, and high-resolution magnetocardiographic (MCG) mapping. In addition, intraoperative epicardial mapping was performed in seven surgically treated patients. The MCG characteristics of ventricular preexcitation for different locations of the atrioventricular accessory pathways were described in terms of morphology and field patterns. Three mathematical source models in semi-infinite conducting space were used for localization computations: the current dipole model, the truncated current multipole model and the magnetic dipole model. Finally, the localization results of MCG and invasive mappings and electrocardiograms were compared. The mean three-dimensional distance between the localization results obtained from MCG maps and electrophysiologic study was 3.9 cm for the magnetic dipole model, 4.8 cm for the truncated current multipole model, and 7.3 cm for the current dipole model. The corresponding distances in the seven intraoperatively mapped cases were 2.3 cm for the magnetic dipole model, 5.2 cm for the truncated current multipole model, and 6.3 cm for the current dipole model. In conclusion, noninvasive MCG mapping may significantly contribute to the invasive catheter mapping for optimal preoperative localization of preexcitation site and atrioventricular accessory pathways in Wolff-Parkinson-White syndrome.

Nd: YAG Laser-Photocoagulation: Acute Electrophysiological, Hemodynamic, and Morphological Effects in Large Irradiated Areas

Laser-photocoagulation (LPC) of arrhythmogenic myocardium has been reported to successfully ablate ventricular tachycardia. The purpose of this study was to investigate the acute hemodynamic and electrophysiological effect of continuous laser energy (Nd:YAG, 1060 nm) applied via a 0.4-mm quartz fiberoptic on the epicardial surface of the heart in nine dogs. A total of 51 +/- 2.3 pulses was delivered in each animal to induce homogeneous tissue necrosis. Applied energy was 12.3 +/- 2.7 J/mm2, irradiated surface measured 12.6 +/- 3.0 cm2, lesion depth was 6.3 +/- 1.2 mm (range: 5.0-8.1 mm), lesion volume was 8.1 +/- 2.8 cm3 (6.8% of left ventricular [LV] mass). After LPC, epicardial stimulation threshold significantly rose from 1.0 +/- 0.3 to 10.2 +/- 4.9 mA in the border zone to nontreated tissue and from 0.9 +/- 0.4 to 32 +/- 15.7 mA in the center of the lesions. Loss of epicardial activation in the irradiated areas could be demonstrated by epicardial mapping. Ventricular extrasystoles during LPC were seen in all dogs, ventricular tachycardia in seven, and ventricular fibrillation in two dogs. After LPC, cardiac output and LV dP/dtmax significantly decreased by 14.2% and 11.2%. LPC induced predictable homogeneous tissue edema, eosinophilic staining, contraction band necrosis, and sharp demarcated hemorrhagic border zones with a sharp electrical border zone to nontreated tissue and loss of epicardial activation. During LPC, various arrhythmogenic effects could be observed. However, no persistent arrhythmic activity developed after LPC. The results confirm the feasibility of epicardial LPC of the myocardium. Although not rested in this study, LPC of arrhythmogenic tissue may also be feasible as a treatment modality of ventricular tachycardia.

Role of concealed and supernormal conductions during atrial fibrillation in the preexcitation syndrome

The hypothesis that retrograde concealed and anterograde supernormal conductions over the accessory pathway are determinants of anterograde accessory pathway conduction during atrial fibrillation (AF) was prospectively tested. For 17 patients during AF, 90 +/- 13 (mean +/- standard deviation) consecutive beats were analyzed for morphology and VV interval preceding each QRS complex. In 15 patients with both preexcited and normal QRS complexes, after normal complexes, the cycle length preceding the first preexcited QRS complex was 389 +/- 69 ms, which was longer than the average cycle length of consecutive preexcited complexes (325 +/- 55 ms; p = 0.001). The mean difference was 61 +/- 53 ms. After preexcited QRS complexes, the cycle length preceding the first normal QRS complex averaged 423 +/- 65 ms, which was significantly longer than the average cycle length of 345 +/- 47 ms between consecutively conducted normal QRS complexes (p less than 0.001). The mean difference was 86 +/- 45 ms. These findings suggest retrograde concealed conduction of normally conducted QRS complexes to the accessory pathway can affect anterograde conduction over the accessory pathway, and vice versa. In 2 patients with multiple accessory pathways, 1 accessory pathway conducted only after short preceding cycle lengths (355 to 360 and 181 to 185 ms), which was consistent with supernormal conduction. In conclusion, retrograde concealed conduction to the accessory pathway conduction are factors that, in part, determine accessory and anterograde supernormal accessory pathway conduction are factors that, in part, determine accessory pathway conduction during AF.

Surgical treatment of the Wolff-Parkinson-White syndrome by epicardial electrical ablation

A new operation to eliminate accessory pathways--epicardial electrical ablation--is described. In a group of 201 patients without concomitant disease, the mortality rate was 0.5% and the overall efficacy of the operation for free wall accessory pathways, 98%. A retrospective clinical study of 44 unselected patients was performed to examine how safe epicardial electrical ablation is. The criteria for intraoperative effectiveness were disappearance of both the delta wave and retrograde conduction and inability to induce tachycardia. In the postoperative and follow-up periods, the following were reviewed: electrocardiograms; Holter monitor recordings (24 to 26 hours); release of the myocardial-specific isoenzyme of creatine kinase; intracardiac hemodynamics and myocardial contractility (radionuclide methods); selective coronary arteriograms and ventriculograms; mean work capacity (bicycle ergometer); diagnostic transesophageal electrical stimulation; and histology of the area of ablation. The main conclusion of this study is that epicardial electrical ablation is a highly efficient and safe operation for surgical elimination of parietal accessory pathways in patients with Wolff-Parkinson-White syndrome. Its advantages are its technical simplicity and the opportunity to review results immediately during the operation.

Modification of atrioventricular node transmission properties by intraoperative neodymium-YAG laser photocoagulation in dogs

The purpose of this study was to test the feasibility of neodymium-yttrium-aluminum-garnet (Nd-YAG) laser photocoagulation of the atrioventricular (AV) node to control the ventricular rate during rapid atrial rhythms without creating AV block. In 12 dogs on normothermic cardiopulmonary bypass, short laser pulses were delivered to an area between the coronary sinus orifice and the site of the most proximally recorded His deflection until second degree AV block occurred at a paced atrial rate of 200 beats/min. Long-term effects on AV node function were followed up for 3 months. Three animals developed chronic high grade AV block. In nine animals with preserved 1:1 conduction, the mean (+/- SEM) critical atrial cycle length resulting in AV node Wenckebach periodicity increased from 183 +/- 6 to 261 +/- 24 ms (+43%), the mean RR interval during induced atrial fibrillation increased from 248 +/- 14 to 330 +/- 27 ms (+32%) and the shortest RR interval during atrial fibrillation increased from 215 +/- 11 to 275 +/- 20 ms (+28%). Laser effects were not reversed by isoproterenol infusion. Histologic examination of the irradiated area showed fibrotic changes in the AV node and fatty metamorphosis. This study suggests that 1) graded Nd-YAG laser photocoagulation of the AV node region in dogs results in long-term modification of anterograde AV node transmission properties; 2) 1:1 conduction during sinus rhythm usually remains preserved, but ventricular rate during rapid atrial rhythms is chronically reduced; and 3) progression to high grade AV block occurs in a minority of animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Daily bedside electrophysiological testing following surgery for the WPW syndrome

A simple technique is described that allows daily bedside evaluation of the results of surgery for the Wolff-Parkinson-White (WPW) syndrome, using standard postoperative myocardial wires, a single-channel ECG machine, and a temporary pacer capable of rapid stimulation. Rate incremental atrial and ventricular ramp pacing was performed daily in 40 postoperative WPW patients. This technique, together with underdrive pacing in some individuals permits quick assessment of anterograde and retrograde conduction. Two surgical failures were identified in early postoperative days, and promptly returned to the operating room for successful reoperation. No additional failures were identified at formal predischarge electrophysiological testing or following discharge. The technique permits reassurance on a daily basis to apparent successes and early identification in the event of failure, permitting prompt intervention.

Surgical therapy for drug-refractory ventricular tachycardia: results with mapping-guided subendocardial resection

Surgical therapy with mapping-guided subendocardial resection was used in 30 patients with drug-refractory ventricular tachycardia. Results of preoperative, intraoperative and postoperative electrophysiologic evaluation and long-term clinical follow-up are reported. Left ventricular aneurysm was located in the inferior wall in 8 patients and in the anterior wall in 22. Left ventricular mapping was performed in 15 patients preoperatively and in all 30 patients intraoperatively. Subendocardial resection was supplemented with cryoablation in 26 patients and with laser photocoagulation in 4. Coronary bypass surgery was performed in 27 patients. The surgical mortality rate was 10%; the three deaths were due to cardiogenic shock, pneumonia and sepsis, respectively. At postoperative electrophysiologic study, ventricular tachycardia was inducible in 8 (30%) of 27 patients. Previously ineffective antiarrhythmic drugs were effective in preventing the induction of ventricular tachycardia in four of these eight patients. Two of the remaining four patients received an automatic implantable cardioverterdefibrillator; the other two were treated with amiodarone. At a mean follow-up period of 18 +/- 17 months (range 1 to 52), there has been one sudden death and one nonfatal recurrence of ventricular tachycardia in the 18 patients without inducible arrhythmias postoperatively. Among the eight patients with inducible ventricular tachycardia after subendocardial resection, there has been one nonfatal ventricular tachycardia recurrence. Thus, among the 27 patients surviving surgery, 17 (63%) were cured with surgery alone, and another 7 (26%) had their ventricular tachycardia controlled with drugs (n = 5) or the defibrillator (n = 2). Inability to completely map the tachycardia, a clinical history of cardiac arrest requiring resuscitation and the presence of myocardial infarction within 2 months predicted postoperative arrhythmia inducibility and recurrence.

Management strategies for surgical treatment of dysrhythmias in infants and children

To elucidate the role of surgery in the management of refractory pediatric dysrhythmias, the investigators' 1987 experience with this therapy was reviewed. Sixteen patients (8 male, 8 female) had surgery. Age ranged from 3 months to 21 years (mean 7.7 years) with 2 being younger than 1 year of age. Eight patients had Wolff-Parkinson-White syndrome with supraventricular tachycardia (SVT), 6 had SVT alone and 2 had ventricular tachycardia. Patient symptoms fell into 3 distinct categories. Nine patients had frequent non-life-threatening tachycardia episodes despite aggressive medical management, 4 patients had life-threatening symptoms either related to frequent tachycardia episodes or due to side effects of drugs and 3 patients had minimal tachycardia symptoms but were judged to be at risk for sudden death. The mechanisms of the tachycardias included reentrant SVT using an accessory atrioventricular connection in 9, the permanent form of junctional reciprocating tachycardia in 2, atrioventricular node reentrant SVT in 2, atrial ectopic focus in 1 and ventricular ectopic foci in 2. Ablation techniques involved either surgical dissection or cryoablation of the arrhythmogenic substrates. There was no surgical mortality and follow-up shows 15 of 16 patients to have had no recurrence of symptomatic tachycardia without any therapy. Based on this experience, management strategies for surgical control of recalcitrant pediatric dysrhythmias are proposed. Surgery for infant dysrhythmias should be performed only for life-threatening symptoms. Beyond the first year of life, after failing 2 medications, surgical options for SVT should be considered. For patients with ventricular tachycardia, aggressive medical management with class II, IC and III agents should be attempted before surgical therapy.

Prophylactic automatic implantable cardioverter-defibrillator patches in patients at high risk for postoperative ventricular tachyarrhythmias

The strategy of placing prophylactic patches for the automatic implantable cardioverter-defibrillator (AICD) without the AICD was employed in 34 patients with coronary artery disease at risk for postoperative ventricular tachycardia undergoing coronary bypass graft surgery (12 patients) or subendocardial resection (22 patients). Patients were selected on the basis of the presence of preoperative sustained ventricular tachycardia (25 patients) or ventricular fibrillation (9 patients) and absence of control of the arrhythmia with 3.6 +/- 1.3 antiarrhythmic drugs by programmed stimulation. Patients having subendocardial resection were also selected on the basis of multiple configurations of ventricular tachycardia, inability to map the tachycardia or posterior wall aneurysm. The surgical mortality rate was 12%, with two deaths after coronary bypass graft surgery and two deaths after subendocardial resection. The AICD patches were removed in 1 of the 34 patients a few hours after surgery because of left atrial laceration and bleeding. Among 10 patients surviving coronary bypass surgery alone, ventricular arrhythmia was not inducible in 6 and in 4 it remained inducible postoperatively. One of the four patients with inducible arrhythmia had the AICD implanted with use of local anesthesia; the other three were treated with drugs. Among 20 patients surviving subendocardial resection, ventricular arrhythmia was noninducible in 15 and remained inducible in 5. Three of these five patients had an AICD implanted; the other two were treated with drugs. At 12 +/- 7 month follow-up, there were no late deaths.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonpharmacologic treatment of supraventricular tachycardia

During the last 2 decades, more than 1,000 patients have undergone surgical division of an accessory pathway; many refinements in epicardial mapping and surgical techniques have been made. In institutions where the procedure is routinely performed, the rate of successful accessory pathway interruption now approaches 98%. Concomitant risk of complete heart block among patients with posteroseptal pathways has declined to less than 5%. Among patients with other organic heart disease, myocardial preservation techniques result in mortality rates within 1 to 2%; among those with significant cardiac abnormalities, the mortality rate is 4 to 6%. Two techniques are generally used to ablate an accessory pathway: the endocardial and the epicardial. The aim of both approaches is to identify the site of the accessory pathway and disarticulate the atrioventricular groove or expose and ablate the atrioventricular junction to interrupt accessory pathway conduction. Although each technique has its advantages, the choice of technique is far less important than the skill of the surgeon and clinical electrophysiologist performing the procedure. Newer surgical techniques include application of external epicardial shocks in the area of the accessory pathway and use of a cryosurgical probe in the sinus to ablate accessory pathways. Whereas our current thought is that surgery should be limited to those adults who fail to respond to pharmacologic therapy, advances in atrial endocardial and epicardial mapping, as well as surgical techniques, may expand the role of surgery in the treatment of ectopic atrial tachycardia.

Surgical management of children and young adults with the Wolff-Parkinson-White syndrome

The Wolff-Parkinson-White syndrome, as originally described, includes palpitations, tachycardia, and an abnormal electrocardiogram (short PR interval and wide QRS complex). The clinical manifestations are dependent upon a reentrant tachycardia supported by an accessory connection bridging the atrioventricular junction and frequently appear during the first two decades of life. Palpitations are the usual symptoms; less frequently, severe symptoms, such as syncope and sudden death, may result from very rapid atrioventricular conduction across the accessory connection during atrial fibrillation. We report the surgical management of 30 young patients with this syndrome, including 6 with life-threatening tachycardia. Surgical interruption of the accessory connection(s) was curative in 90% (27/30) of the patients; life-threatening symptoms were eliminated in the other three. Based on the limited knowledge of the natural history of the Wolff-Parkinson-White syndrome, the individual patient symptoms, and the electrophysiologic properties of each patient's accessory pathway(s), an algorithm is presented outlining the treatment options. This experience strongly suggests that surgical treatment of the Wolff-Parkinson-White syndrome is safe, effective, and possibly the preferred treatment for this disorder in selected young symptomatic patients.