Rationale for a direct surgical approach to control ventricular arrhythmias: relation of specific intraoperative techniques to mechanism and location of arrhythmic circuit

Activation mapping in patients with coronary artery disease with multiple ventricular tachycardia configurations: occurrence and therapeutic implications of widely separate apparent sites of origin

Catheter or intraoperative activation mapping studies, or both, were performed in 17 patients with coronary artery disease with two to four distinct configurations of ventricular tachycardia, resistant to a mean of 12.1 +/- 6.0 antiarrhythmic drug trials per patient. Mapping studies were performed to guide anticipated surgical ablation of arrhythmias. Activation map data were adequate to determine sites of origin of 30 (64%) of 47 observed tachycardia configurations. These 30 ventricular tachycardias (26 observed clinically) were mapped to 22 separate endocardial sites of origin. Sites of origin of distinct tachycardias were identical or closely adjacent (within 3 cm) in six patients and widely separate (greater than or equal to 4 cm) in eight patients (47% of the group). Activation maps were not adequate to determine sites of origin of 17 (36%) of the 47 tachycardias, including all configurations in three patients. Fifteen patients underwent surgery for control of ventricular tachycardia: aggressive, map-guided endocardial resection (mean 26.5 +/- 14.2 cm2) in 12 patients with identified sites of tachycardia origin and extensive resection of visible endocardial scar (2 patients) or encircling endocardial ventriculotomy (1 patient) in those in whom the sites of origin of all clinical tachycardias remained undetermined. Two inoperable patients were treated with amiodarone. During postoperative electrophysiologic tests (11 of 13 surgical survivors), ventricular tachyarrhythmias were initially uninducible in only 4 of 11 patients. However, in two patients only nonclinical arrhythmias (ventricular flutter) were induced. Six (21%) of 29 clinical tachycardias whose sites of origin were either not determined or not resected (right septum or papillary muscle) remained inducible in five patients. Using previously ineffective antiarrhythmic drugs, initially inducible arrhythmias became uninducible (two patients), or harder to induce than preoperatively (five patients). As a result of surgical resections alone or in combination with previously ineffective drugs (and amiodarone in two inoperable patients), there were no recurrences of ventricular tachycardia in 14 (93%) of 15 patients discharged during 19.0 +/- 14.3 months of follow-up study. Thus, activation mapping may commonly reveal separate apparent sites of origin for clinically observed, morphologically distinct, highly drug-refractory ventricular tachycardias in patients with coronary artery disease with multiple tachycardia configurations. Extensive surgical resection of identified sites of origin may be required to ablate arrhythmias in these patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Endocardial activation mapping and endocardial pace-mapping using a balloon apparatus

The relation between endocardial activation mapping and endocardial pace-mapping was evaluated in 8 dogs while they were on cardiopulmonary bypass. Pacing or recording was accomplished by using a balloon apparatus (with 32 bipolar electrodes) inserted through a left apical ventriculotomy. Ventricular tachycardia (VT) was produced by occlusion followed by reperfusion of the left anterior descending coronary artery. During each VT, activation mapping was performed and early sites determined. Pace-map correlates (sites at which endocardial pacing produced a similar QRS morphology to that of the VT) were also determined. Isochronous maps were constructed for activation mapping and pace-mapping. There was a total of 29 morphologically distinct VTs. Groups were delineated according to correlations between activation mapping and pace-mapping. In 14 episodes of VT (group 1), pace-mapping confirmed the findings of activation mapping with all early sites being pace-map correlates (total number of early sites (tES) = 19; total number of pace-map correlates (tPMC) = 88; tES same as tPMC = 19). In 9 episodes of VT (group 2), there was a partial correlation between pace-mapping and activation mapping, such that pace-mapping when used with activation mapping appeared to further delineate the region of arrhythmogenesis (tES = 31; tPMC = 59; tES same as tPMC = 14). In 6 episodes of VT (group 3), there was no correlation between pace-mapping and activation mapping (tES = 15; tPMC = 0). With the balloon apparatus, endocardial activation mapping can be performed without the need for sustained monomorphic VT, and endocardial pace-maps may be generated easily.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac electrophysiologic testing: its role in the selection of antiarrhythmic drug regimens for supraventricular and ventricular arrhythmias

Cardiac electrophysiology studies use intracardiac recording and programmed stimulation to define the mechanisms and most appropriate therapy for supraventricular and ventricular arrhythmias. Using these techniques, the majority of clinical tachycardias can be reproducibly initiated and terminated in the electrophysiology laboratory, thereby allowing the most appropriate therapy to be selected. With this approach, antiarrhythmic agents can be tested in a systematic, serialized fashion for efficacy, safety and patient tolerance. With both supraventricular and ventricular tachycardias, suppression of arrhythmia induction predicts freedom from recurrence, whereas inducibility carries a poor prognosis in clinical follow-up. Electrophysiology studies provide a safe and effective approach to the treatment of selected patients with cardiac arrhythmias.

Physiopathology of ventricular tachyarrhythmias

Ventricular arrhythmias may be the result of three mechanisms: abnormal automaticity, triggered activity complicating early or late after-depolarizations, and reentry by circular pathway or by reflection. These three fundamental mechanisms have been observed in the intact heart in experimental models of myocardial ischemia and digitalis intoxication. In man, the arguments in favor of a given mechanism are indirect and may be determined by their response to stimulation. It may be possible to state the following conclusions: (1) reentry is at the origin of ventricular fibrillation, certain ventricular tachycardias of bundle branch reentry and probably most chronic sustained ventricular tachycardias that are easily inducible; (2) the mechanism of certain other ventricular arrhythmias sustained remains unknown; (3) even when arrhythmias are associated with reentry, the triggering extrasystole can arise from a focal origin.

Subendocardial resection for ventricular tachycardia: predictors of surgical success

We retrospectively evaluated the first 100 patients who underwent mapping-guided subendocardial resection (SER) at our hospital for drug-refractory sustained ventricular tachycardia caused by coronary artery disease. There were 91 survivors of surgery with 200 morphologically distinct types of ventricular tachycardia. Eighty-three patients (91%) were cured of ventricular tachycardia by SER alone (60 patients or 66%) or by SER in combination with antiarrhythmic drug therapy (23 patients or 25%) (mean follow-up, 28 +/- 19 months). There were four late sudden deaths and four patients continued to have rare episodes of spontaneous ventricular tachycardia after surgery despite receiving antiarrhythmic drugs. Factors associated with failure of SER alone to cure ventricular tachycardia were presence of disparate sites of ventricular tachycardia origin (greater than 5 cm between mapped sites of origin; 64% vs 30% failure rate) and presence of multiple morphologically distinct spontaneous tachycardias (47% vs 25% failure rate). A log-linear model of multivariate analysis identified disparate sites of origin of ventricular tachycardia and the absence of a discrete left ventricular aneurysm as the only independent variables associated with failure of surgery alone. Inferior wall site of origin (41% vs 12% failure) and right bundle branch block morphology of ventricular tachycardia (20% vs 7% failure) were also significantly associated with failure of surgery to cure ventricular tachycardia. Mapping-guided SER is a highly effective mode of treatment for drug-refractory ventricular tachycardia, despite the existence of subgroups of patients with higher-than-average surgical failure rates.

Operative therapy for ventricular arrhythmia

The history of surgical attempts to control ventricular arrhythmia is reviewed and current methodology is presented in detail. The results of the various surgical approaches and future trends in the management of this troublesome condition are discussed.

Recurrent sustained ventricular tachycardia: structure and ultrastructure of subendocardial regions in which tachycardia originates

Surgical resection of the endocardium and subendocardium often abolishes chronic recurrent sustained ventricular tachycardia in patients with healed myocardial infarcts or ventricular aneurysms, presumably by interrupting the reentrant pathway. To define the morphologic characteristics of cells in the reentrant pathway, we studied the histology and ultrastructure of the endocardial resections of 23 patients who underwent this procedure. Bundles of apparently viable myocardial fibers embedded in dense fibrous tissue were identified throughout the endocardial resections from all patients. These bundles of cells were separated from one another by fibrous tissue but extended uninterrupted to the margins of the surgical resection. In 14 patients Purkinje fibers were identified beneath the thickened endocardium whereas the remaining bundles were composed of ventricular muscle. The Purkinje fibers appeared to have normal ultrastructure and ventricular cells with both normal and abnormal ultrastructures were present. The abnormal muscle cells were characterized by loss of contractile elements, aggregates of dilated sarcoplasmic reticulum, and osmiophilic dense bodies. The sarcolemma was intact and the nuclear chromatin was evenly dispersed suggesting that these cells were still viable. The abnormal structure and arrangement of the surviving cardiac fibers in the endocardium may cause the abnormal electrophysiologic function that results in ventricular tachycardia.

Intraventricular Wenckebach conduction and localized reentry in a case of right ventricular dysplasia with recurrent ventricular tachycardia

Serial electrophysiologic studies were performed in a patient with recurrent ventricular tachycardia of left bundle branch configuration whose course and noninvasive evaluation are consistent with a diagnosis of right ventricular dysplasia. The localization of slowed conduction to the right ventricular apex, the reproducible initiation and termination of tachycardia with programmed extrastimuli and the presence of continuous electrical activity during tachycardia suggest a reentrant mechanism for this arrhythmia. Antiarrhythmic drugs further prolong the already fragmented apical electrogram and result in Wenckebach conduction within the abnormal portion of the right ventricle during pacing and tachycardia. Electrophysiologic findings are remarkably similar in studies performed 32 months apart.

Anatomic-electrophysiologic basis for the surgical treatment of refractory ischemic ventricular tachycardia

Recently developed surgical procedures for the treatment of refractory ischemic ventricular tachycardia have significantly improved the prognosis of patients experiencing these life-threatening arrhythmias. Ventricular tachyarrhythmias associated with ischemic heart disease most commonly originate from the ischemic border zone of myocardial infarctions, where the non-uniformity of tissue injury is most prominent. The inhomogeneity in tissue injury results in desynchronization of electrical wavefront propagation through the ischemic myocardium, thus providing the milieu necessary for the development of micro-reentrant circuits that give rise to the ventricular tachyarrhythmias. Preoperative and intraoperative electrophysiologic mapping techniques are capable of characterizing and localizing such arrhythmogenic myocardium sufficiently to direct the surgeon in his operative approach to the treatment of the arrhythmia. Surgical options include the encircling endocardial ventriculotomy, the endocardial resection procedure, endocardial cryoablation, and combinations or modifications of these three basic procedures. The use of these procedures has made the previously employed indirect surgical procedures obsolete for the treatment of refractory ischemic ventricular tachyarrhythmias.

Ventricular cryosurgery: short-term effects on intramural electrophysiology

The acute effects of cryothermia on regional electrophysiology were examined in order to devise a means of localizing and monitoring the intramural progression of ventricular cryolesions during a two-minute period of cryothermia application. Intramural unipolar electrograms were recorded from multipoint plunge electrodes placed in the left ventricle in 15 dogs. Epicardial, intramural, and endocardial applications of cryothermia were then employed, and changes in the unipolar peak-to-peak amplitude (UPPA) of electrograms were recorded. The location and depth of the ultimate permanent cryolesion could be predicted by noting locations of those electrograms demonstrating a decrease in the UPPA to less than 30% of the control values. Such electrophysiological monitoring of the region of myocardium undergoing cryothermic ablation provides a means of limiting the ultimate cryolesion to the desired location and depth within the ventricular wall. This allows precise placement of cryolesions in specific areas of the left ventricle for the treatment of ventricular tachyarrhythmias by selectively ablating arrhythmogenic ventricular myocardium without inducing injury in surrounding nonarrhythmogenic myocardium.

Analysis of interectopic activation patterns during sustained ventricular tachycardia

We analyzed the patterns of interectopic continuous electrical activity recorded within interectopic intervals of sustained ventricular tachycardias. These arrhythmias were induced in dogs that were studied 4 days after left anterior descending coronary artery occlusion. Standard ECG leads and electrograms from the His bundle and left ventricular epicardium, both infarct and normal zone, were recorded. In 19 of 24 dogs with transmural myocardial infarction, one to three ventricular paced beats induced sustained ventricular tachycardia, characterized by continuous electrical activity between the initiating and spontaneous ectopic beat and between successive ectopic beats recorded from the epicardium over the infarct zone but not from the normal epicardium. Continuous activity consisted of discrete potentials that were reproduced in each cardiac cycle, suggesting slow conduction within a reentrant circuit. The interectopic activity was divided into three distinct temporal periods, delineated by potentials occurring at the initial portion, the mid-interectopic portion and terminal portion or exit of the slow conduction segment of the presumed reentrant circuit. In some cases, sustained ventricular tachycardia was induced only if an appropriate initial potential was engaged. Spontaneous termination of the sustained ventricular tachycardia was associated with Wenckebach-like block of conduction in the initial or exit potential. Ventricular pacing caused alteration of the interectopic patterns and resulted in cessation of the arrhythmia. Procainamide produced dose-dependent slowing of the ectopic rate due to depression of conduction in the mid-interectopic portion of the continuous electric activity. Inducibility of the sustained ventricular tachycardia was inhibited by decremental conduction in this compartment of the presumed reentry circuit. The present study uses a preparation showing sustained ventricular tachycardia that is stable and regular. Functional analysis of the various portions of the continuous electrical activity during sustained tachycardias allows further insight into the mechanisms of initiation and termination of sustained ventricular tachycardias. The ability to localize the effect of antiarrhythmic drugs on specific portions of a possible reentrant circuit may provide important correlative data for the analysis and interpretation of detailed epicardial mapping studies.

Clinical electrophysiology--a decade of progress

During the past 14 years there have been major advances in the field of clinical electrophysiology. This progress is a result of a more extensive use of intracardiac electrode catheters with recordings from multiple sites in the right and left cardiac chambers, the introduction of programmed electrical stimulation techniques and the use of antiarrhythmic drugs for diagnostic and therapeutic purposes during acute electrophysiologic testing. This article examines the pioneering studies and the subsequent developments in the field of clinical electrophysiology. The specific topics that are reviewed include the sinus node and atrium, atrioventricular conduction, supraventricular tachycardia and ventricular tachycardia. The therapeutic implications of each topic are also discussed. Clinical electrophysiology in its initial stages was a descriptive technique, but has since become an important diagnostic and therapeutic tool. However, electrophysiologic testing is an intensive process, requiring specialized training and a substantial commitment of human and physical resources.