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

A history of collaboration between electrophysiologists and arrhythmia surgeons

Introduction: The notion that medically‐refractory arrhythmias might one day be amenable to interventional therapy slowly began to appear in the early 1960's. At that time, there were no “interventional electrophysiologists” or “arrhythmia surgeons” and there was little appreciation of the relationship between anatomy and electrophysiology outside the heart's specialized conduction system. Methods: In this review, we describe the evolution of collaboration between electrophysiologists and surgeons. Results: Although accessory atrio‐ventricular (AV) connections were first identified in 1893 and the Wolff‐Parkinson‐White (WPW) syndrome was described 37 years later (1930), it was another 37 years (1967) before those anatomic AV connections were proven to be responsible for the clinical syndrome. The success of the subsequent surgical procedures for the WPW syndrome, AV node reentry tachycardia, automatic atrial tachycardias, ischemic and non‐ischemic ventricular tachycardias and atrial fibrillation over the next two decades depended on a close, sometimes daily, collaboration between electrophysiologists and surgeons. In the past two decades, that tight collaboration was largely abandoned until the recent introduction of “hybrid procedures” for the treatment of atrial fibrillation. Conclusions: A retrospective assessment of the 50 years of interventional therapy for arrhythmias clearly demonstrates the clinical benefits of a close collaboration between electrophysiologists and arrhythmia surgeons, regardless of which one is actually performing the intervention.

Mechanisms, prediction and treatment of ventricular tachyarrhythmias occurring late after myocardial infarction

Studies from the 1980s, refined in the intervening years, have examined the milieu for ventricular tachycardia (VT) and ventricular fibrillation (VF) occurring late after acute myocardial infarction (AMI). The arrhythmogenic substrate appears to be patchy areas of fibrous tissue interdigitating with viable bundles of myocardium which have distorted orientation and tortuous interconnections. These promote conduction delay in sinus rhythm. Factors found to promote induction of VT rather than VF are longer conduction delay in sinus rhythm, larger infarct size, a more ragged infarct edge and longer ventricular extrastimulus coupling intervals. Predictors of spontaneous VT and VF late after AMI include inducible VT at electrophysiological studies (EPS), delayed conduction in sinus rhythm detected as late potentials on signal-averaged surface electrocardiogram (ECG), and low left ventricular ejection fraction (LVEF). Treatments of propensity for VT or VF after AMI include insertion of a defibrillator (ICD), which has the best track record, antiarrhythmic medication (less reliable), and ablation or excision of arrhythmogenic substrate (for refractory VT and VF).

Effects of simultaneous insertion of 66 plunge needle electrodes on myocardial activation, function, and structure

Transmural recordings using plunge needle electrodes are useful in mapping ventricular tachyarrhythmia, but they interfere with activation sequences or damage the myocardium. This study evaluated the effects of insertion of 66 transmural needles on myocardial activation, structure, and function. Epicardial maps were performed at thoracotomy using a 40-electrode plaque in five mongrel dogs. Sixty-six transmural plunge needles were introduced into the anterior aspect of the septum and left ventricle. Transmural maps of unipolar electrograms were recorded every 15 minutes via 124 electrodes over a 2-hour period. Epicardial maps were repeated after the needles were removed. All recordings were performed during sinus rhythm and ventricular pacing at 300- and 200-ms cycle lengths. Gated heart pool studies were performed preoperatively and 2 weeks after thoracotomy. Programmed ventricular stimulation was performed 2 weeks after thoracotomy. In total, 15,996 electrograms were analyzed. Maximum negative dV/dt of each electrogram and the activation time at each electrode did not change significantly over the 2 hours of needle insertion. After removal of the needles, epicardial maps were unchanged compared to before needle insertion. Mean left ventricular ejection fraction 2 weeks after needle insertion was 59% versus 58% before needle insertion (P=0.9). No dogs had inducible ventricular tachycardia. Histology showed contraction bands of 0.8-mm diameter adjacent to the needle tracks but no scarring. Insertion of 66 closely spaced plunge needles did not distort epicardial or transmural maps. Multiple needles did not result in myocardial scarring, left ventricular dysfunction, or predispose to ventricular tachycardia.

Cardiac Surgery for Arrhythmias

Cardiac arrhythmia surgery was initiated in 1968 with the first successful division of an accessory AV connection for the Wolff-Parkinson-White Syndrome. Subsequent surgical procedures included the left atrial isolation procedure and the right atrial isolation procedure for automatic atrial tachycardias, discrete cryosurgery of the AV node for AV nodal reentry tachycardia, the atrial transection procedure, corridor procedure and Maze procedure for atrial fibrillation, the right ventricular disconnection procedure for arrhythmogenic right ventricular tachycardia, the encircling endocardial ventriculotomy, subendocardial resection procedure, endocardial cryoablation, the Jatene procedure, and the Dor procedure for ischemic ventricular tachycardia. Because of monumental strides in the treatment of most refractory arrhythmias by endocardial catheter techniques during the past decade, the only remaining viable surgical procedures for cardiac arrhythmias are the Maze procedure for atrial fibrillation and the Dor procedure for ischemic ventricular tachycardia. Nevertheless, the 25-30 years of intense activity in the field of cardiac arrhythmia surgery provided the essential foundation for the development of these catheter techniques and represent one of the most exciting and productive eras in the history of medicine. In one short professional career, we have witnessed the birth of arrhythmia surgery, its adolescence as an "esoteric" specialty, its prime as an enlightening yet exhausting period, and finally its waning years as a source of knowledge and wisdom on which better methods of treatment have been founded. One could hardly ask for a more rewarding experience.

Cardiac Surgery for Arrhythmias

Cardiac arrhythmia surgery was initiated in 1968 with the first successful division of an accessory AV connection for the Wolff-Parkinson-White syndrome. Subsequent surgical procedures included the left atrial isolation procedure and right atrial isolation procedure for automatic atrial tachycardias, discrete cryosurgery of the AV node for AV nodal reentrant tachycardia, the atrial transection procedure, the corridor procedure, and the maze procedure for atrial fibrillation, the right ventricular disconnection procedure for arrhythmogenic right ventricular tachycardia, and the encircling endocardial ventriculotomy, subendocardial resection procedure, endocardial cryoablation, the Jatene procedure, and the Dor procedure for ischemic ventricular tachycardia. Because of monumental strides in the treatment of most refractory arrhythmias by endocardial catheter techniques during the past decade, the only remaining viable surgical procedures for cardiac arrhythmias are the maze procedure for atrial fibrillation and the Dor procedure for ischemic ventricular tachycardia. Nevertheless, the 25 to 30 years of intense activity in the field of cardiac arrhythmia surgery provided the essential foundation for the development of these catheter techniques and represent one of the most exciting and productive eras in the history of medicine. In one short professional career, we have witnessed the birth of arrhythmia surgery, its adolescence as an "esoteric" specialty, its prime as an enlightening yet exhausting period, and finally its waning years as a source of knowledge and wisdom upon which better methods of treatment have been founded. One could hardly ask for a more rewarding experience.

Effects of surgery for postinfarction ventricular tachycardia on parameters of left ventricular function

Heart failure is the leading cause of death in patients after surgery for ventricular tachycardia. This study examines the effects of antiarrhythmic surgery on 4 parameters of left ventricular (LV) function. Global ejection fraction, segmental wall motion score, homogeneity of contraction, and diastolic function were measured in 32 patients by technetium-99m radionuclide ventriculography. Ejection fraction was measured from the left anterior oblique image. Wall motion score was assessed semiquantitatively for 11 LV segments from 3 projections. Homogeneity of contraction was expressed as the SD of the LV phase analysis curve during systole from the left anterior oblique image. Diastolic function was expressed in terms of peak and mean first time derivative of the action potential (dV/dt) of the LV function curve. Subgroup analyses were performed to distinguish the effects of aneurysmectomy, coronary artery bypass grafting, and changes in angiotensin converting enzyme inhibitor therapy. Mean systolic function improved after surgery (ejection fraction 22% vs 32%, p <0001; wall motion score 20 vs 13, p <0.0001; phase analysis 18 vs 12, p <0.03). Mean diastolic function also improved (peak dV/dt 0.83 +/- 0.32 vs 1.49 +/- 0.39, p = 0.006; mean dV/dt 0.41 +/- 0.15 vs 0.76 +/- 0.27, p = 0.006). Improvements were not confined to those who had aneurysmectomy or coronary bypass grafting and were not explained by changes in vasodilator therapy. Thus, antiarrhythmic surgery does not inherently damage LV function. Significant improvements were observed in most patients. Failure to improve indicated a poor longer term prognosis.

Will C. Sealy, MD: the father of arrhythmia surgery--the story of the fisherman with a fast pulse

The development of clinical electrophysiology and arrhythmia surgery has a long and interesting history. On May 2, 1968, Dr. Will C. Sealy, with the electrophysiologists at Duke University, performed the first successful ablation of a pathway in a patient with Wolff-Parkinson-White syndrome using an epicardial approach. Thereafter, he and his colleagues developed improved endocardial techniques to ensure ablation of even multiple and complex anatomic pathways. From this work the impulse to perform these procedures spread worldwide, and a school of arrhythmia surgeons sprouted. For these and other accomplishments, Dr. Sealy clearly became the Father of Arrhythmia Surgery. The story is told herein.

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.

Identification of patients with ventricular tachycardia after myocardial infarction by high-resolution magnetocardiography and electrocardiography

The value of time domain analysis of late fields in the high-resolution magnetocardiogram in the identification of myocardial infarction patients with ventricular tachycardia was investigated in 30 subjects: 10 patients with documented sustained ventricular tachycardia and old myocardial infarction, 10 patients with old myocardial infarction without complex ventricular arrhythmias, and 10 normal volunteers. The duration of the QRS complex in the magnetocardiogram was significantly longer in ventricular tachycardia patients compared to myocardial infarction patients (144 (SD, 33) vs 109 (SD, 8) ms; p = 0.004). The root-mean-square field of the last 60 ms of the QRS complex was smaller in ventricular tachycardia patients than in myocardial infarction patients (830 (SD, 650) vs 1,480 (SD, 730) fT, respectively; p = 0.047). Also, the duration of the low-amplitude signal less than 700 fT was longer in ventricular tachycardia patients than in myocardial infarction patients (47 (SD, 28) vs 28 (SD, 8) ms, respectively; p = 0.048). The sensitivity and specificity in identifying ventricular tachycardia patients were both 80%, and the positive and negative predictive values were 78% and 86%, respectively. High-resolution electrocardiography recorded during the same session performed slightly better: sensitivity 90%, specificity 90%, and positive and negative predictive values 90%. The signal-to-noise ratio of electrocardiogram was higher (approximately 2 x) than that of magnetocardiogram. It is concluded that the new magnetocardiographic technique seems helpful in screening patients at risk of ventricular arrhythmias after myocardial infarction. The results encourage further refinement of the technique and application in prospective studies.

Syncope

Syncope is a clinical entity of diverse cause. The historical features surrounding the syncopal event and the presence or absence of heart disease are the most important features in establishing the cause for syncope. Passive head-up tilt study provides a means of identifying many patients with vasodepressor syncope. Electrophysiologic study is important in the elucidation of syncope in patients who have syncope undefined after noninvasive evaluation. With proper use of the modalities available, few patients will have an undefined cause for syncope.

Surgical therapy for drug-refractory ventricular tachycardia: role of additional aneurysmectomy or bypass grafting

To assess whether additional aneurysmectomy and/or bypass grafting influence prognosis we studied 97 patients with recurrent sustained monomorphic ventricular tachycardia after an old myocardial infarction. All patients underwent subendocardial resection due to drug-refractory ventricular tachycardia. There were 41 patients who had resection alone, 27 patients had resection and aneurysmectomy, 13 patients had resection and bypass grafting and the remaining 16 patients had resection with both, aneurysmectomy and bypass grafting. During the mean follow-up of 40 +/- 27 months 29 patients died (30%) (total mortality), 7 patients suddenly (7%) and 20 patients from cardiac causes (20%). There were no significant differences in total mortality between patients with resection alone (32%), patients with resection and aneurysmectomy (22%), patients with resection and bypass grafting (31%) and patients who had resection, aneurysmectomy and bypass grafting (38%). In addition, no significant differences were observed in the incidence of sudden death and nonfatal recurrences between patients with resection alone: sudden death 12%, recurrences 7%; patients with resection and aneurysmectomy: sudden death 0%, recurrences 19%; patients with resection and bypass grafting: sudden death 0%, recurrences 8%; and patients with resection, aneurysmectomy and bypass grafting: sudden death 13%, recurrences 0%. Postoperatively, left ventricular function improved in 56% of patients who had resection and aneurysmectomy compared to 17% of patients with resection alone, 31% of patients with resection and bypass grafting and 19% of patients who had resection, aneurysmectomy and bypass grafting. There is a low risk of sudden death and nonfatal recurrences after subendocardial resection. An influence of additional surgical approaches (aneurysmectomy or bypass grafting) on prognosis is not visible.

Macroreentry in the infarcted human heart: the mechanism of ventricular tachycardias with a "focal" activation pattern

Endocardial mapping of electrical activity was carried out in 150 patients to guide antiarrhythmic surgery for drug-resistant ventricular tachycardia in the chronic phase of myocardial infarction. In 20 of these patients, the activation pattern of 27 distinct tachycardias was focal and diastolic potentials were recorded at three or more sites. In 26 tachycardias, the sequence of diastolic potentials progressed from the area of latest activation of one cycle toward the "origin" of the next cycle. In two patients, the heart was stimulated during tachycardia, resulting in entrainment of the tachycardia in both. Late potentials were recorded during entrainment at sites where diastolic potentials occurred during tachycardia. In 11 of the 20 patients, endocardial mapping was performed during sinus rhythm. In four of these, late potentials were observed during sinus rhythm at sites where diastolic potentials were recorded during tachycardia. In two patients without late potentials during sinus rhythm, late potentials were observed during stimulation and induced ectopic beats. The results support the concept that the mechanism of several of these tachycardias is based on reentry in a macrocircuit comprising a tract of surviving tissue traversing the infarct and the remaining healthy tissue. They also indicate that the absence of late potentials during sinus rhythm does not guarantee the absence of arrhythmogenic pathways.

Retrospective analysis of patients undergoing one- or two-stage strategies for myocardial revascularization and implantable cardioverter defibrillator implantation

Internal defibrillation leads were placed at time of coronary revascularization in 79 patients. In 34, an implantable cardioverter defibrillator (ICD) was placed simultaneously (group I). A two-stage strategy (selective implantation of the ICD in patients with postoperative spontaneous or inducible ventricular tachycardia [VT]) was followed in 45 patients (group II). Group I patients had failed more antiarrhythmic drug trials (2.9 +/- 1.6 vs 1.5 +/- 1.6; P = 0.02), including amiodarone (62% vs 20%; P less than 0.001). There were four operative deaths in each group. Postoperatively, VT was present in 27 group II patients (60%), 25 of whom received an ICD (two refused device implantation). Patients with postoperative VT had a lower left ventricular ejection fraction than those without VT (33 +/- 9 vs 47 +/- 16; P = 0.01). Actuarial survival at 1, 2, and 3 years was 88 +/- 6, 88 +/- 7, and 88 +/- 10 in group I; and 83 +/- 6, 76 +/- 7, and 76 +/- 11 in group II (NS). No patient without an ICD (based on the postoperative electrophysiological study [EPS]) died suddenly. Five patients (6%) had ICD system infection. Sudden death was largely prevented by either strategy, but relatively high rates of operative mortality and ICD system infection were observed. Prospective studies should identify patients more likely to benefit from one or another strategy.

Surgery for control of recurrent life-threatening ventricular tachyarrhythmias within 2 months of myocardial infarction

Twenty-seven patients (mean age 57 +/- 7 years) underwent surgery for control of recurrent drug-refractory ventricular tachyarrhythmias (uniform ventricular tachycardia alone in 9 patients, ventricular tachycardia and ventricular fibrillation in 15 and ventricular fibrillation alone in 3) within 2 months of acute myocardial infarction. The mean number of major arrhythmic episodes per patient was 15 (range 2 to 200) and of drug failures 4 +/- 2. Left ventricular function was severely impaired in the majority (ejection fraction 29%; range 14% to 47%) and 18 patients (66%) had a left ventricular aneurysm. Endocardial resection guided by a combination of endocardial activation mapping during tachycardia and fragmentation mapping during sinus rhythm was performed in all patients. All electrically abnormal left ventricular endocardium was excised. Eight patients (29.6%) died within 30 days of surgery. Death was not related to age, time of surgery after infarction, ventricular function, bypass time or type of arrhythmia. Patients requiring emergency surgery had a higher early postoperative mortality rate than did those undergoing planned surgery (43% versus 15%). During a follow-up period of 32 +/- 20 months, there have been no arrhythmic deaths and only three patients (16%) have required antiarrhythmic drug therapy. When required in the early weeks after infarction, surgery for ventricular arrhythmias offers a high cure rate at a risk related to the patient's preoperative arrhythmia frequency, which in turn relates to the risk of arrhythmic death.

Ventricular tachycardia in the infarcted, Langendorff-perfused human heart: role of the arrangement of surviving cardiac fibers

Electrophysiologic and histologic studies were performed on Langendorff-perfused human hearts from patients who underwent heart transplantation because of extensive infarction. In nine hearts, 15 sustained ventricular tachycardias could be induced by programmed stimulation. In all hearts, mapping of epicardial and endocardial electrical activity during tachycardia was carried out. Histologic examination of the infarcted area between the site of latest activation of one cycle and the site of earliest activation of the next cycle revealed zones of viable myocardial tissue. In two hearts in which the time gap between latest and earliest activation was small, surviving myocardial tissue constituted a continuous tract that traversed the infarct. In three other hearts in which the time gap was large, surviving tissue consisted of parallel bundles that coursed separately over a few hundred micrometers, then merged into a single bundle and finally branched again. The direction of the fibers within the bundles was perpendicular to the direction of the activation front in that area. A similar type of inhomogeneous anisotrophy and activation delay was found in an infarcted papillary muscle removed from one of the explanted hearts and studied in a tissue bath during basic stimulation. Histologic examination of this preparation revealed that the delay was caused by a zigzag route of activation over branching and merging bundles of surviving myocytes separated by connective tissue.

Electrophysiological and anatomic differences between canine hearts with inducible ventricular tachycardia and fibrillation associated with chronic myocardial infarction

This study examined electrophysiological and anatomic differences between dogs with ventricular tachycardia (VT) and fibrillation (VF) inducible by programmed ventricular stimulation 7-21 days after left anterior descending coronary artery ligation. Of 106 dogs studied, 40 had inducible VT, 19 had inducible VF, and 47 had no inducible arrhythmias. Differences between these three groups of animals were examined with cardiac mapping (to determine ventricular activation time in sinus rhythm) and post-mortem pathology (to measure infarct size and to reconstruct the anatomy at the infarct edge). Animals with inducible VT had longer maximal epicardial activation time (127 +/- 8 msec) than did animals with inducible VF (91 +/- 8 msec, p less than 0.05) or animals with no inducible arrhythmias (75 +/- 2 msec, p less than 0.001). Delayed epicardial activation occurred in 90% of animals with VT, 42% of animals with VF, and in only 6% of animals with no inducible arrhythmias. Endocardial and myocardial activation times were similar for the VT and VF groups. Infarct size was 18 +/- 2% of the ventricles for the VT group, much higher than for the VF group (11 +/- 2%, p less than 0.001) or for the group with no inducible arrhythmias (9 +/- 1%, p less than 0.001). The maximum diameter of viable muscle bundles interdigitating with scar tissue at the infarct edge was much larger in animals with VT (2.4 +/- 0.2 mm) than in animals with VF (1.8 +/- 0.2 mm, p less than 0.05) or animals with no inducible arrhythmias (1.7 +/- 0.1 mm, p less than 0.01). Thus, when compared with animals with inducible VF, animals with inducible VT had longer epicardial activation time, larger infarct size and viable muscle bundles of larger diameter at the infarct edge.

Endocardial mapping of ventricular tachycardia in the intact human ventricle: evidence for reentrant mechanisms

A balloon array of 112 electrodes was used to obtain simultaneous recordings of endocardial electrograms during intraoperative mapping studies of ventricular tachycardia. Introduction of the balloon through a left atriotomy and across the mitral valve allowed endocardial activation maps to be obtained in the intact left ventricle. Of 20 patients with coronary artery disease studied in this way, suggestive evidence of endocardial reentry was found in 6. Three separate reentrant mechanisms were observed. In two patients, a single broad wave front of continuous recirculating activation reminiscent of a vortex was initiated by the formation of a functional arc of block in response to premature stimuli. In five patients, premature stimuli again produced a functional arc of block, which was circumvented by two opposing wave fronts that united on the distal side. Retrograde penetration by a narrow isthmus of slow conduction through the block initiated the tachycardia, whose activation sequence was consistent with figure eight reentry. In one patient, premature stimuli produced a region of delayed potentials. Critical timing of these resulted in microreentry in an adjacent circumscribed site, which formed the site of origin of the ensuing tachycardia. The microreentrant signals were not detected by standard unipolar recordings, but were seen on simultaneously recorded high gain electrograms. In 14 patients, although mapping identified a site of origin, the activation patterns showed either radial spread or incomplete circles. Detection of reentrant mechanisms during intraoperative mapping required high density electrode arrays and refined high gain recordings. An intact ventricle may facilitate intraoperative initiation of tachycardia.

Differences between patients with ventricular tachycardia and ventricular fibrillation as assessed by signal-averaged electrocardiogram, radionuclide ventriculography and cardiac mapping

This study examined 65 patients with ventricular tachycardia or fibrillation late after myocardial infarction to determine whether they differed with respect to duration of ventricular activation in sinus rhythm and left ventricular ejection fraction. Patients with spontaneous ventricular tachycardia had a longer ventricular activation time in sinus rhythm than did patients with spontaneous ventricular fibrillation. This difference was detected with the signal-averaged electrocardiogram (ECG) (tachycardia 181 +/- 33 ms, fibrillation 152 +/- 23 ms, p less than 0.001) and at epicardial mapping (tachycardia 210 +/- 17 ms, fibrillation 192 +/- 17 ms, p less than 0.02). Left ventricular ejection fraction was lower in patients with spontaneous ventricular tachycardia (0.22 +/- 0.09) than in patients with spontaneous ventricular fibrillation (0.27 +/- 0.09) (p less than 0.05). The patients with both spontaneous and inducible ventricular fibrillation had a shorter ventricular activation time on the signal-averaged ECG (129 +/- 17 ms) and a higher ejection fraction (0.36 +/- 0.05) than did either patients with spontaneous ventricular fibrillation and inducible ventricular tachycardia (158 +/- 21 ms and 0.25 +/- 0.08, respectively, each p less than 0.01) or patients with both spontaneous and inducible ventricular tachycardia (181 +/- 33 ms and 0.22 +/- 0.09, respectively, each p less than 0.001). Of the patients with inducible ventricular tachycardia, presentation with tachycardia rather than fibrillation was associated with a longer ventricular activation time on the signal-averaged ECG (181 +/- 33 versus 158 +/- 21 ms, p less than 0.02) and a longer cycle length of inducible ventricular tachycardia (290 +/- 61 versus 259 +/- 44 ms, p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular fibrillation survivors in whom tachyarrhythmia cannot be induced: outcome related to selected therapy

Eight-five patients were studied to determine the prognosis of the ventricular tachyarrhythmias at the time of electrophysiologic study. Twenty-five patients (29%) were not inducible when we used a stimulation protocol consisting of up to four extrastimuli delivered at two right ventricular sites. Patients with no inducible arrhythmias were younger (53 vs 59 yrs; p = .06) and had higher ejection fractions (.49 vs .34; p less than .04) than the inducible ventricular fibrillation survivors. Sex, cardiac diagnosis, time from event to electrophysiologic study, and antiarrhythmic therapy at the time of event did not discriminate between those with and those without inducible ventricular tachyarrhythmias. Survival free of recurrent sudden death or ventricular tachycardia was .86 +/- .05 and .95 +/- .05 for patients with and without inducible tachyarrhythmias, respectively (p = .22). Nine of 25 (36%) patients with no inducible arrhythmias developed inducible ventricular tachyarrhythmias when testing was repeated with an antiarrhythmic drug. Ventricular fibrillation survivors not inducible at the time of programmed ventricular stimulation (using a stimulation protocol consisting of four extrastimuli delivered at two right ventricular sites) seem to have a good prognosis. Many "noninducible" patients develop inducible tachyarrhythmias when placed on antiarrhythmic therapy. Because it is possible that these drugs are proarrhythmic, empiric antiarrhythmic therapy should be avoided in these patients.

Changes in ventricular activation time on the signal-averaged electrocardiogram in the first year after acute myocardial infarction

Repeat signal-averaged electrocardiograms were used in 40 patients to document changes in ventricular activation time and delayed potentials in the first 12 months after acute myocardial infarction. Beta-blocking and antiarrhythmic drug use was stopped for 1 week before each recording. Patients with reinfarction during follow-up were excluded. Signal-averaged electrocardiograms were first performed 1 to 4 weeks after infarction. They were repeated at 6 and 12 months in 31 patients in whom spontaneous ventricular tachycardia (VT) did not develop and were repeated after VT in the other 9 patients. Of the 9 patients in whom VT developed, all had delayed potentials at initial study and 8 (89%) still had delayed potentials at restudy after VT. In the VT patients, mean ventricular activation time was similar before and after VT (178 ms and 174 ms, respectively). In the 11 patients who had delayed potentials initially and in whom VT did not develop, the proportion with delayed potentials was 55% (6 of 11) at 6 months and did not change (55%) at 12 months. Mean ventricular activation time in these patients was 164 ms at initial study, decreasing to 147 ms at 6 months (p less than 0.05) and 148 ms at 12 months. In 20 patients with no delayed potentials initially, none had delayed potentials at 6 months and only 2 (10%) had delayed potentials detectable at 12 months. Mean ventricular activation time in these patients increased slightly, from 120 ms at initial study to 128 ms at 12 months (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of excision of ventricular myocardium on delayed potentials detected by the signal-averaged electrocardiogram in patients with ventricular tachycardia

The ability of surgical excision of electrically abnormal ventricular myocardium to either abolish delayed potentials or modify their timing was investigated in 21 patients with spontaneous ventricular tachycardia (VT) late after myocardial infarction. This study also examined whether modification of delayed potentials after surgery was associated with loss of ability to induce VT or improvement in left ventricular function. Signal averaging of the electrocardiogram (ECG), programmed stimulation and radionuclide ventriculography were performed preoperatively and were repeated 10 to 14 days postoperatively. At preoperative investigation, all patients had delayed potentials on the signal-averaged ECG and inducible VT at programmed stimulation. In 7 patients (33%), delayed potentials were abolished by surgery, exceeding the baseline variability of 8.5% for detection of delayed potentials. VT was no longer inducible postoperatively in 16 patients (76%), including the 7 in whom delayed potentials were no longer detectable. In the patients in whom VT was no longer inducible, mean ventricular activation time decreased from 178 ms preoperatively to 151 ms postoperatively (standard error of the mean difference = 6 ms, p less than 0.001). In the 5 patients with inducible VT postoperatively, no significant change in mean ventricular activation time was seen, 181 vs 171 ms (standard error of mean difference = 9 ms). Reductions in ventricular activation time were not associated with an improvement in left ventricular ejection fraction unless aneurysmectomy was performed in addition to excision of electrically abnormal myocardium. Thus, the signal-averaged ECG may have a role in assessing the efficacy of antiarrhythmic surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between signal-averaged electrocardiogram and programmed stimulation in patients with and without spontaneous ventricular tachyarrhythmias

This study examined the incidence of delayed ventricular activation on signal-averaged electrocardiograms and the incidence of inducible sustained ventricular tachycardia (VT) at programmed stimulation (1 or 2 extrastimuli) in patients with and patients without spontaneous ventricular tachyarrhythmias. The correlation between delayed ventricular activation and inducible VT was investigated in 371 patients with acute myocardial infarction (AMI). In 32 patients with no ventricular disease and no spontaneous arrhythmias (group I), ventricular activation time averaged 115 +/- 2 ms, compared with 166 +/- 3 ms (p less than 0.001) for 65 patients with spontaneous ventricular tachyarrhythmias late after AMI (group II). In AMI patients with no spontaneous arrhythmias, ventricular activation time averaged 133 +/- 2 ms for 306 patients studied 1 to 4 weeks after AMI (group III) and 130 +/- 2 ms for 67 patients studied 3 to 12 months after AMI (group IV). The values for group III and group IV patients were each significantly higher than for group I (p less than 0.001), but lower than that for group II (p less than 0.001). The incidence of delayed ventricular activation was 89% for group II, 26% for group III and 18% for group IV. Sustained VT was not inducible in group I patients, but was inducible in 78% of group II (p less than 0.001 vs group I) and 20% of group III (p less than 0.05 vs group I; p less than 0.001 vs group II) (group IV was not studied).(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic significance of ventricular tachycardia and fibrillation induced at programmed stimulation and delayed potentials detected on the signal-averaged electrocardiograms of survivors of acute myocardial infarction

The relative prognostic significance of ventricular tachycardia and ventricular fibrillation inducible at programmed stimulation within 1 month of acute myocardial infarction was compared in a prospective study of 403 clinically well survivors of transmural infarction who were 65 years old or younger. The prognostic significance of delayed potentials on the signal-averaged electrocardiogram was also examined in a subset of 306 patients without bundle branch block. Among the study patients, 20% had inducible ventricular tachycardia, 14% had inducible ventricular fibrillation, and 66% had no inducible arrhythmias. The 2 year probability of remaining free from cardiac death or nonfatal ventricular tachycardia or fibrillation was 0.73 for those with inducible ventricular tachycardia, 0.93 for those with inducible ventricular fibrillation, and 0.92 for those with no inducible arrhythmias. The cycle length of inducible ventricular tachycardia was 230 msec or more in 70% of the patients with inducible tachycardia who died. Of the patients studied by signal-averaged electrocardiography, 26% had delayed potentials. At 2 years, the probability of remaining free from cardiac death or nonfatal ventricular tachycardia or fibrillation was 0.73 for patients with delayed potentials and 0.95 for patients with no delayed potentials. There was a significant correlation (p less than .001) between the presence of delayed potentials and the ability to induce ventricular tachycardia. In conclusion, in survivors of recent infarction who have not had spontaneous ventricular tachycardia or fibrillation, inducible tachycardia (but not inducible fibrillation) at programmed stimulation predicts a significant risk of death or spontaneous tachycardia or fibrillation. A similar risk is found for patients with delayed potentials on the signal-averaged electrocardiogram.

The effect of chemical ablation of the endocardium on ventricular fibrillation threshold

The purpose of this study was to examine the effects of ablation of the superficial endocardium and Purkinje network on left ventricular fibrillation threshold. Lugol's solution was applied through small ventriculotomies to the left and right ventricular endocardium of 10 dogs on cardiopulmonary bypass. Two control groups of five animals each underwent either endocardial application of saline or epicardial application of Lugol's solution. Ventricular fibrillation threshold was measured before and after each intervention by the single-stimulus technique. Application of Lugol's solution to the endocardium resulted in a 102 +/- 15% increase in ventricular fibrillation threshold from a control value of 26 +/- 2 to 53 +/- 6 mA (p less than .005). In two animals, ventricular fibrillation could not be initiated postoperatively. In the control groups, there were no significant changes in ventricular fibrillation threshold. Histologic examination revealed that Lugol's solution obliterated less than 0.5 mm of superficial endocardium while sparing the adjacent myocardium. Electrophysiologic and rheologic data confirmed the discrete nature of the chemical injury. Thus ablation of the superficial ventricular endocardium with Lugol's solution results in a profound increase in the ventricular fibrillation threshold with only minimal tissue destruction.

Electrophysiologic sequelae of chronic myocardial infarction: local refractoriness and electrographic characteristics of the left ventricle

Ventricular tachycardia (VT) has been shown to arise from ischemically damaged left ventricular myocardium, which possesses heterogeneity of refractoriness and activation. Catheter techniques were used to study left ventricular refractoriness using the strength-interval relation and activation by local electrographic characteristics in 8 patients with and 6 patients without previous myocardial infarction (MI). Noninfarcted myocardium in patients with and without previous MI was similar overall with respect to refractoriness and excitability, whereas local electrographic duration in MI patients was longer (66 +/- 2 vs 52 +/- 3 ms, p less than 0.005) and amplitude lower (3.9 +/- 2.1 vs 6.1 +/- 2.0 mV, p less than 0.05). Comparisons of infarcted and noninfarcted regions in MI patients revealed an increased threshold of excitability at infarct sites (e.g., 1.9 +/- 1.0 vs 0.7 +/- 0.4 mA, p less than 0.05) and prolongation of refractory periods (375 +/- 118 vs 275 +/- 13 ms, p less than 0.05) at the lowest level of stimulating current. Shortening of refractory period as a result of change in pacing cycle length was not affected by infarction. The local electrographic duration (95 +/- 17 ms) was significantly longer in infarcted regions than at noninfarcted sites (p less than 0.005), but the electrographic amplitude (3.4 +/- 3.0 mV) differed significantly only in noninfarct patients. It is concluded that considerable electrophysiologic disparity exists between infarcted and noninfarcted myocardium. Whether or not arrhythmogenic tissue possesses unique alterations in electrophysiologic characteristics remains to be established.

Surgical ablation of ventricular tachycardia: improved results with a map-directed regional approach

To determine whether a regional approach to surgery for ventricular tachycardia would improve on the results of previously reported methods of endocardial resection, an analysis was performed of our surgical experience over a 5 year period. Of 46 consecutive patients operated on for recurrent sustained ventricular tachycardia or ventricular fibrillation, 39 patients with ischemic heart disease underwent subendocardial resection and/or cryoablation. The mean age of the patients was 61 +/- 8 (SD) years, the mean left ventricular ejection fraction was 32 +/- 11%, and the mean number of ineffective antiarrhythmic drugs was 3.8 +/- 1.2 per patient. In 35 of 39 patients in whom mapping data were obtainable, 56 (86%) tachycardias had earliest sites of activation in the left ventricle and nine (14%) had earliest sites in the right ventricle. Ten patients had 14 tachycardias (21%) mapped to areas outside visible dense scar. Of these 35 patients, 10 underwent localized subendocardial resection and 25 underwent a regional procedure in which all areas activated before the surface QRS during ventricular tachycardia were excised and/or cryoablated. In the operative survivors of electrophysiologically guided surgery, three of eight (38%) patients with the localized and one of 24 (4%) patients who underwent the regional procedure had recurrence of ventricular tachycardia during a follow-up period of 1 to 59 (mean 22 +/- 17) months (p = .04). The favorable outcome of regional surgery was not influenced by the presence of multiple morphologies in 54%, disparate sites of origin in 29%, or inferior wall foci in 46% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Indications for different modes of surgical therapy in medically refractory ventricular arrhythmias

Fifty-one adult patients were referred for surgical treatment during the time period from July 1980 to November 1985. The average age was 59 +/- 6 years (19-70 years). All patients had symptomatic ventricular tachycardia that was refractory to standard or experimental drug therapy. On the basis of patient condition, site of arrhythmia, ventricular function, and extent of coronary disease, 21 patients were classed as good risk (GR) while 30 patients were thought to represent a poor surgical risk (PR). Thirty-two patients (15 GR, 17 PR) underwent electrophysiologic guided endocardial resection of arrhythmic foci. The hospital mortality was 12% (4/32), and two additional patients died late. All deaths were in poor risk patients. Recurrent arrhythmia was the primary cause of death in only one patient. Nineteen patients have required automatic internal cardioverter defibrillation (AICD) or chronic burst pacing (BP) with an implantable radiofrequency stimulator, with no operative mortality. AICD implantation was chosen for 13 drug refractory patients who were either poor surgical risk and/or had a tachycardia rate above 130 beats/minute with multiple scars or a multifocal tachycardia. Six additional patients who had tachycardia less than 130 beats/minute and whose arrhythmia could be safely terminated with BP had radiofrequency stimulator implantation. The one late death in this group was in a medically noncompliant patient. On the basis of this experience, we feel that map-guided endocardial resection should be offered to all good risk patients with a single scar and unifocal tachycardia who are refractory to medical treatment. This operation should be considered in all patients who have frequent, life-threatening attacks of tachycardia of any sort on maximum drug therapy. The remainder can be well managed with an AICD if their tachycardia rate is greater than 130 beats/minute or with BP using a radiofrequency stimulator.

Sympathectomy in the treatment of angina and arrhythmias

Sympathectomy has been used as treatment for several different cardiac conditions. These include classic angina pectoris, Prinzmetal's angina, paroxysmal atrial tachycardia, ventricular tachycardia, and long QT syndrome. To understand the rationale of such treatment, the innervation of the human heart is reviewed with discussion of the cardiac plexus and coronary innervation. Results in published studies are summarized and discussed.

Nonarrhythmogenicity of therapeutic cryothermic lesions of the myocardium

There is increasing interest in the application of surgical methods to the treatment of refractory ventricular tachyarrhythmias (VT). Cryothermic ablation is one of the more promising techniques. However, there is clinical concern that a cryothermic lesion may lead to later arrhythmias. Previous studies have shown that dogs with nonhomogeneous, transmural infarctions are susceptible to VT initiation using programmed electrical stimulation (PES). The purpose of this study was to compare the incidence of inducing VT in dogs with transepicardial cryothermic myocardial damage (Group A) versus dogs with nonhomogeneous transmural infarctions resulting from 2-hr occlusion of the left anterior descending coronary artery (LAD) and subsequent reperfusion (Group B). Twelve dogs in each group were studied 10-14 days later using PES with unipolar cathodal ventricular pacing and two ventricular extrastimuli. Initiation of VT was attempted from at least six normal intramyocardial sites in each dog along the distribution of the LAD and in close proximity (less than or equal to 1 cm) to areas of chronically cryoablated damaged tissue. All dogs survived the initial procedure. VT was not inducible in any dog in Group A. Histological as well as electrophysiological evaluation, including determination of regional excitability thresholds and refractory periods employing strength-interval curves, revealed that all of the Group A dogs had homogeneous transmural infarcts with variable subendocardial sparing. In conclusion (1) cryothermal injury produces homogeneous damage; and (2) the lesion produced is not arrhythmogenic at 7-14 days.

Long-term follow-up of survivors of prehospital sudden cardiac death treated with coronary bypass surgery

Although coronary artery bypass surgery is beneficial to patients with severe coronary artery disease, its role in preventing the recurrence of prehospital cardiac arrest in patients is not clear. In this article, we report on the long-term follow-up of 49 survivors of prehospital coronary arrest who had coronary artery bypass surgery. Prior to their prehospital cardiac arrest, 14% of the patients had a history of unstable angina. Coronary angiograms obtained after prehospital cardiac arrest showed that 71% of the patients had three-vessel coronary artery disease and 6% had single-vessel disease. The mean left ventricular ejection fraction was 45%. There were four postoperative deaths; three were caused by pump failure, and one was caused by refractory ventricular arrhythmias. After a maximum follow-up period of 102 months (mean of 55.4 months), there were seven cardiac deaths; five of the patients died of recurrent ventricular fibrillation, and two patients' deaths were related to refractory heart failure. Actuarial analyses of the 49 patients showed that the probability of survival at 6 months, 1 year, 2 years, 3 years, and 5 years was 92%, 92%, 89%, 82%, and 72%, respectively. After surgery, 35 of the 45 patients who were discharged from the hospital were asymptomatic, and 23 of the 32 patients who were employed when their prehospital cardiac arrest occurred returned to their employment. We concluded that coronary artery bypass surgery is beneficial to certain survivors of prehospital sudden death. After surgery, most patients are asymptomatic and capable of returning to their employment and the recurrence of prehospital sudden death is low.