Right ventricular isolation procedures for nonischemic ventricular tachycardia

Surgical Ablation of Ventricular Tachycardia

Surgery for ventricular tachycardia (VT) is indicated in patients in whom pharmacotherapy or catheter ablation is ineffective or frequent VT attacks are not suppressed or with frequent activation of implantable cardioverter defibrillator. In ischemic VT, resection of fibrous endocardium combined with encircling cryothermia at the border between the infarcted and normal myocardium is performed. In surgery for VT associated with cardiomyopathy, close collaboration between the physician and surgeon is important and intraoperative mapping using electro-anatomic mapping system is helpful. In VT associated with cardiac tumors, cryothermia of the thinned subepicardial myocardium at the edge of the tumor is recommended in addition to resection of tumors.

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.

Cryosurgery for Atrial Fibrillation: Physiologic Basis for Creating Optimal Cryolesions

BACKGROUND

Although cryosurgery has been used to treat cardiac arrhythmias for nearly 5 decades, the mechanism of action and the surgical technique that produces optimal cryolesions for the treatment of atrial fibrillation are still poorly understood. This has resulted in surgical outcomes that can be improved by a better understanding the mechanisms of cryothermia ablation and the proper surgical techniques that take advantage of those mechanisms.

METHODS

The cryobiology underlying cryosurgical ablation is described, as are the nuances of cryosurgical techniques that ensure the reliable creation of contiguous, uniformly transmural atrial cryolesions. The oft-misunderstood "2-minute rule" for the application of cryothermia is clarified in detail, along with its variations that depend on target myocardial temperature.

RESULTS

The creation of optimal cryolesions depends on cryoprobe temperature, the temperature of the target myocardium, the duration of cryothermia application, and the presence or absence of a "heat sink" or "cooling sink" created by intracavitary blood circulation. Cryothermia kills myocardial cells during both the freezing and thawing phases of cryoablation cycle. The critical lethal temperature for myocardium is -30°C. The slower the target tissue thaws, the higher the percentage of cell death.

CONCLUSIONS

The availability of cryosurgical techniques has revolutionized the surgical treatment of atrial fibrillation. By utilizing modern cryosurgical devices and adhering to the technical principles described, surgeons can now perform surgical procedures for atrial fibrillation that are quicker, safer, and as effective as the standard Maze-III/IV procedure.

Assessment of ventricular contractility in fetuses with an estimated fetal weight less than the tenth centile

OBJECTIVE

To determine whether abnormal global, transverse, and longitudinal ventricular contractility of the heart in fetuses with an estimated fetal weight <10th centile is present, irrespective of Doppler studies of the umbilical artery and cerebroplacental ratio.

STUDY DESIGN

This was a retrospective study of 50 fetuses with an estimated fetal weight <10th centile that were classified based on Doppler results from the pulsatility indices of the umbilical artery and middle cerebral artery, and the calculated cerebroplacental ratio (pulsatility indices of the umbilical artery/middle cerebral artery). Right and left ventricular measurements were categorized into 3 groups: (1) global ventricular contractility (fractional area change), (2) transverse ventricular contractility (24-segment transverse fractional shortening), and (3) basal-apical longitudinal contractility (longitudinal strain, longitudinal displacement fractional shortening, and basal lateral and septal wall annular plane systolic excursion). Z scores for the above measurements were computed for fetuses with an estimated fetal weight <10th centile using the mean and standard deviation derived from normal controls. Ventricular contractility measurements were considered abnormal if their Z score values were <5th centile (z score <-1.65) or >95th centile (Z score >1.65), depending on the specific ventricular measurement.

RESULTS

The average gestational age at the time of the examination was 32 weeks 4 days (standard deviation 3 weeks 4 days). None of the 50 study fetuses demonstrated absent or reverse flow of the umbilical artery Doppler waveform. Eighty-eight percent (44/50) of fetuses had one or more abnormal measurements of cardiac contractility of 1 or both ventricles. Analysis of right ventricular contractility demonstrated 78% (39/50) to have 1 or more abnormal measurements, which were grouped as follows: global contractility 38% (19/50), transverse contractility 66% (33/50); and longitudinal contractility 48% (24/50). Analysis of left ventricular contractility demonstrated 1 or more abnormal measurements in 58% (29/50) that were grouped as follows: global contractility 38% (19/50); transverse contractility 40% (20/50); and longitudinal contractility 40% (20/50). Of the 50 study fetuses, 25 had normal pulsatility index of the umbilical artery and cerebroplacental ratios, 80% of whom had 1 or more abnormalities of right ventricular contractility and 56% of whom had 1 or more abnormalities of left ventricular contractility. Abnormal ventricular contractility for these fetuses was present in all 3 groups of measurements; global, transverse, and longitudinal. Those with an isolated abnormal pulsatility index of the umbilical artery (n=11) had abnormalities of transverse contractility of the right ventricular and global contractility in the left ventricle. When an isolated cerebroplacental ratio abnormality was present, the right ventricle demonstrated abnormal global, transverse, and longitudinal contractility, with the left ventricle only demonstrating abnormalities in transverse contractility. When both the pulsatility index of the umbilical artery and cerebroplacental ratio were abnormal (3/50), transverse and longitudinal contractility measurements were abnormal for both ventricles, as well as abnormal global contractility of the left ventricle.

CONCLUSIONS

High rates of abnormal ventricular contractility were present in fetuses with an estimated fetal weight <10th centile, irrespective of the Doppler findings of the pulsatility index of the umbilical artery, and/or cerebroplacental ratio. Abnormalities of ventricular contractility were more prevalent in transverse measurements than global or longitudinal measurements. Abnormal transverse contractility was more common in the right than the left ventricle. Fetuses with estimated fetal weight less than the 10th centile may be considered to undergo assessment of ventricular contractility, even when Doppler measurements of the pulsatility index of the umbilical artery, and cerebroplacental ratio are normal.

A Hybrid Maze Procedure for Long-Standing Persistent Atrial Fibrillation

BACKGROUND

Catheter ablation (CA) for long-standing persistent atrial fibrillation (LSPAF) is suboptimal, and open surgical ablation, although more successful, is too invasive to be a first-line therapy. Less invasive hybrid procedures that combine thoracoscopic surgery (TS) with CA have been only marginally more successful for LSPAF than CA alone.

METHODS

Joint hybrid procedures for LSPAF are based on the assumption that AF surgery and CA procedures can be guided by intraoperative mapping. However, intraoperative mapping is not always dependable because of the transient nature of the sustaining reentrant drivers. The best results in patients with LSPAF have been attained with the non-guided, anatomy-based surgical Maze-III and Maze-IV procedures. Likewise, a staged TS/CA hybrid procedure that creates a combination of lesions that adhere to the concept of a Maze pattern, that is, a Hybrid Maze-IV procedure, should be more effective for LSPAF.

RESULTS

Initial TS includes all lesions of the Maze-IV procedure except the mitral line, coronary sinus lesion, and one right atrial lesion. Follow-up CA at 3 months includes touching up any incomplete TS lesions, a cavotricuspid isthmus lesion, and a mitral line/coronary sinus lesion in the 10% to 15% of patients with post-TS perimitral flutter. This combination of TS and CA lesions creates a complete Maze-IV procedure.

CONCLUSIONS

It is possible to create the complete lesion pattern of a Maze-IV procedure with a staged TS/CA hybrid procedure. The success of this Hybrid Maze procedure in patients with LSPAF should be the same as that attained with an open surgical Maze-IV procedure.

Will the real ventricular architecture please stand up?

Ventricular twisting, essential for cardiac function, is attributed to the contraction of myocardial helical fibers. The exact relationship between ventricular anatomy and function remains to be determined, but one commonly used explanatory model is the helical ventricular myocardial band (HVMB) model of Torrent‐Guasp. This model has been successful in explaining many aspects of ventricular function, (Torrent‐Guasp et al. Eur. J. Cardiothorac. Surg., 25, 376, 2004; Buckberg et al. Eur. J. Cardiothorac. Surg., 47, 587, 2015; Buckberg et al. Eur. J. Cardiothorac. Surg. 47, 778, 2015) but the model ignores important aspects of ventricular anatomy and should probably be replaced. The purpose of this review is to compare the HVMB model with a different model (nested layers). A complication when interpreting experimental observations that relate anatomy to function is that, in the myocardium, shortening does not always imply activation and lengthening does not always imply inactivation.

What Is the Heart? Anatomy, Function, Pathophysiology, and Misconceptions

Cardiac dynamics are traditionally linked to a left ventricle, right ventricle, and septum morphology, a topography that differs from the heart's five-century-old anatomic description of containing a helix and circumferential wrap architectural configuration. Torrent Guasp's helical ventricular myocardial band (HVMB) defines this anatomy and its structure, and explains why the heart's six dynamic actions of narrowing, shortening, lengthening, widening, twisting, and uncoiling happen. The described structural findings will raise questions about deductions guiding "accepted cardiac mechanics", and their functional aspects will challenge and overturn them. These suppositions include the LV, RV, and septum description, timing of mitral valve opening, isovolumic relaxation period, reasons for torsion/twisting, untwisting, reasons for longitudinal and circumferential strain, echocardiographic sub segmentation, resynchronization, RV function dynamics, diastolic dysfunction's cause, and unrecognized septum impairment. Torrent Guasp's revolutionary contributions may alter future understanding of the diagnosis and treatment of cardiac disease.

Pacing to Restore Right Ventricular Contraction After Surgical Disconnection for Arrhythmia Control in Right Ventricular Cardiomyopathy

Ventricular tachycardia in ARVC (arrhythmogenic right ventricular cardiomyopathy) is typically managed by ICD implantation, with a limited role of catheter ablation. Surgical disconnection of the right ventricular (RV) has been used to control ventricular tachycardia (VT) in ARVC, but it often led to refractory RV failure due to loss of RV contraction after surgery. We report multisite pacing to recruit the disconnected RV to prevent ventricular failure.

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.

Right ventricular exclusion surgery for arrhythmogenic right ventricular dysplasia with cardiomyopathy

IMPLICATIONS

The authors describe the management of a patient with arrhythmogenic right ventricular dysplasia treated with right ventricular exclusion surgery.

Total right ventricular exclusion procedure: an operation for isolated congestive right ventricular failure

OBJECTIVE

To prevent possible deleterious effects of right ventricular volume overload on cardiorespiratory function, we developed a total right ventricular exclusion procedure for the treatment of end-stage isolated congestive right ventricular failure.

METHODS

Since 1996, this procedure has been performed in 5 patients in New York Heart Association functional class IV: 2 adults with arrhythmogenic right ventricular dysplasia and 3 children with Ebstein anomaly. The entire right ventricular free wall was resected along the atrioventricular groove and then parallel to the interventricular septum, sparing the pulmonary valve and a skeletonized right coronary artery. The orifice of the tricuspid valve was closed with either a polytetrafluoroethylene patch or with its leaflets. The defect of the right ventricular free wall was covered with a polytetrafluoroethylene patch in the 2 patients with arrhythmogenic right ventricular dysplasia and directly closed with the remnant of the free wall in the 3 children with Ebstein anomaly. After resection of a redundant right atrial wall, coronary sinus blood flow was rerouted into the left atrium through an atrial septal defect. A total cavopulmonary connection was constructed in 4 patients and a bidirectional superior cavopulmonary anastomosis in 1 infant. The heart was controlled with a DDD pacemaker in 3 patients.

RESULTS

The patients were extubated at a mean of 14 hours postoperatively (range, 1-38 hours). There were no early or late deaths. At follow-up, ranging from 8 to 57 months, the mean cardiothoracic ratio had decreased from 74% +/- 7% before the operation to 52% +/- 6% (P <.01). All patients are in functional class I. Neither of the patients with arrhythmogenic right ventricular dysplasia have had attacks of ventricular tachycardia nor are they using antiarrhythmic medication.

CONCLUSIONS

The total right ventricular exclusion procedure provides effective decompression of the lung, as well as the left ventricle, and may result in more effective volume loading of a surgically created single ventricle with increased systemic output. We believe that this new surgical option offers rescue treatment for isolated end-stage right ventricular failure in critically ill patients.

Pacing in right ventricular dysplasia after disconnection surgery

This report describes a 33-year-old patient with arrhythmogenic right ventricular (RV) dysplasia who had a dual chamber pacemaker implanted at age 23 years for drug-induced bradycardia. Pacing was continued after right ventricular free-wall disconnection (RVFWD) at age 24 years. Her pacemaker was not replaced after battery depletion 7 years later. She presented the following year in severe right-sided heart failure. Her old pacemaker generator was replaced. This was followed by rapid resolution of her clinical failure and return to a full, active, physical lifestyle. This observation suggests the potential benefit of dual chamber pacing in patients with RV dysplasia after RVFWD.

Arrhythmogenic right ventricular dysplasia/cardiomyopathy: review for the clinician

Although hypertrophic obstructive cardiomyopathy remains the most common cause of sudden cardiac death in young people, rarer causes, such as arrhythmogenic right ventricular dysplasia (ARVD), are now being increasingly recognized to lead to sudden cardiac death in the younger population. Recent advances in the understanding of the genetic inheritance, etiopathogenesis, diagnosis, and treatment options of ARVD have prompted a lot of research in this form of right ventricular cardiomyopathy. The purpose of this report is to review the etiopathogenesis, clinical manifestations, diagnosis and treatment modalities for ARVD, and recent advances in the understanding of this disease entity.

Right ventricular disarticulation procedures: the role of late potentials in the genesis of postoperative ventricular arrhythmias

Arrhythmogenic right ventricular disease may be associated with life-threatening and drug refractory ventricular arrhythmias. Right ventricular disarticulation procedures are effective antiarrhythmic surgical approaches in selected patients. This study examined the role of late potentials in the postoperative development of new ventricular arrhythmias, and showed that right ventricular isolation is effective, probably because it destroys the tissue giving rise to late potentials. Total disarticulation is associated with fewer postoperative arrhythmias than partial isolation procedures. Total disarticulation may be the surgical approach of choice in such patients.

Surgical treatment of arrhythmogenic right ventricular dysplasia: long-term outcome

Eight male patients ranging from 15 to 51 years old (mean age, 36.3 years) underwent surgical treatment of ventricular tachycardia (VT) associated with arrhythmogenic right ventricular dysplasia. One patient had an associated left ventricular aneurysm. The earliest activation site was detected for 15 lesions, and delayed potentials were recorded during sinus rhythm in all patients. On the basis of the epicardial mapping, the origins of the VT foci in the right ventricle were resected. Cryoablation on the surrounding myocardium was performed. There were no surgical deaths or postoperative fatal complications. During long-term follow-up, there has been no recurrence of VT and no congestive heart failure in the 6 patients without left ventricular involvement. The 2 patients with LV involvement died late of either congestive heart failure or development of VT originating from the left ventricle. In conclusion, a surgical approach consisting of myocardial excision and cryocoagulation offers a curative treatment of VT associated with arrhythmogenic right ventricular dysplasia and yields excellent long-term results when the VT origin is well identified in the right ventricle.

Surgical treatment of cardiac dysrhythmias in infants and children

A variety of cardiac rhythm disturbances that occur in infants and children may be refractory to medical or catheter ablation therapy, or both, and thus require surgical ablation. These dysrhythmias include Wolff-Parkinson-White syndrome, atrial automatic tachycardia, atrioventricular node reentry tachycardia, and ventricular tachycardia. The surgical technique originally used in adults may be equally well applied in infants and small children. In the interval from July 1, 1984, through December 31, 1993, a total of 130 infants and children (< or = 16 years old) underwent surgical treatment for various forms of dysrhythmias (96 with Wolff-Parkinson-White syndrome, 8 with atrioventricular node reentry, 11 with atrial automatic tachycardia, and 15 with ventricular tachycardia). The success rate for completely abolishing these arrhythmias has been 92% for the Wolff-Parkinson-White syndrome, 100% for atrioventricular node reentry, and 64% for atrial automatic tachycardia. In infants younger than 2 years, the success rate for the surgical treatment of ventricular tachycardia is 100%, but the long-term success in older children has been poor. One patient sustained a severe intraoperative neurologic event that resulted in her death (operative mortality, 0.7%). Ventricular function returned to normal in all patients in whom it was abnormal preoperatively. These data suggest that the surgical treatment of these dysrhythmias remains a viable alternative in those patients whose dysrhythmias are refractory to medical therapy, those in whom catheter ablation has been unsuccessful, or those in whom both situations apply.

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.

Surgery for ventricular tachycardia associated with right ventricular dysplasia: disarticulation of right ventricle in 9 of 10 cases

Ten patients (nine men, one woman; mean age 39 years) with arrhythmogenic right ventricular dysplasia underwent surgery to control life-threatening drug refractory ventricular arrhythmias. All had ventricular tachycardia causing syncope and six had a history of cardiac arrest. In all a minimum of three antiarrhythmic drugs (mean five) had been ineffective. At operation, the right ventricle was grossly diseased in all patients. Ventricular tachycardias were induced and mapped intraoperatively in all patients. The surgical plan was to ablate the arrhythmogenic focus if it was less than 4 cm2; one patient was so managed. Of the remaining nine, four underwent partial (approximately 40% of the right ventricular free wall) and five underwent total right ventricular disarticulation. All survived the operation and are alive at a mean follow-up interval of 24 months (range 5 to 67). Two patients developed new sustained ventricular tachycardias. These were well tolerated and, unlike the original arrhythmias, were easily controlled by drug treatment. All patients who underwent right ventricular disarticulation manifested signs of right heart failure in the early postoperative period, but these lessened progressively with the development of systolic septal movement into the right ventricular cavity. All 10 patients are in New York Heart Association class I or II at last review. In selected patients with arrhythmogenic right ventricular dysplasia, surgery offers a curative treatment for ventricular tachycardia and should be considered for patients whose arrhythmias are life-threatening and refractory to drug treatment.

Hemodynamic importance of systolic ventricular interaction, augmented right atrial contractility and atrioventricular synchrony in acute right ventricular dysfunction

To delineate the determinants of right ventricular performance with acute right ventricular dysfunction, surgical electrical isolation of the right ventricular free wall was produced in 13 dogs. During atrioventricular (AV) pacing, hemodynamic and wall motion measurements were normal. When not paced, the right ventricular free wall became asystolic, resulting in a depressed and bifid right ventricular systolic pressure (33 +/- 5 to 18 +/- 4 mm Hg) and decreased left ventricular systolic pressure (100 +/- 18 to 80 +/- 18 mm Hg) and stroke volume (14 +/- 4 to 10.3 +/- 3.5 ml) (all p less than 0.05). Ultrasound demonstrated right ventricular free wall dyskinesia, increased right ventricular end-diastolic size (155 +/- 13% of control), but decreased left ventricular size (69 +/- 11% of control) (both p less than 0.05). Right atrial pressure increased (5.8 +/- 2.5 to 7.6 +/- 2.8 mm Hg, p less than 0.05) with an augmented A wave and blunted Y descent, indicating pandiastolic right ventricular dysfunction. The septum demonstrated reversed curvature in diastole and bulged paradoxically into the right ventricle during early systole, generating the initial peak of right ventricular pressure and reducing its volume. Later, posterior septal motion coincided with maximal left ventricular pressure and the second peak of the right ventricular waveform. Left ventricular pacing alone led to further decreases in right ventricular systolic pressure and size, left ventricular systolic pressure and stroke volume. The previously augmented A wave was replaced by a prominent V wave. Therefore, when contractility of its free wall is acutely depressed, right ventricular performance is dependent on left ventricular-septal contractile contributions transmitted by the septum.(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular pressure effects on right ventricular pressure and volume outflow

Massive destruction of the right ventricular free wall has been shown to cause only mild hemodynamic alterations. Further, the derivative of right ventricular (RV) pressure (P) is broad or double peaked, with one peak occurring coincidentally with peak left ventricular (LV) dP/dt. Both observations suggest a direct LV assistance to RV function. Since the ventricles contract nearly simultaneously, the relative contribution of LV to RV pump function has been difficult to determine. This LV assistance was quantified in six canine experiments using a unique electrically isolated RV preparation. While on total cardiopulmonary bypass, the RV free wall was electrically isolated from the remainder of the heart. This preparation allowed for wide variations in the timing interval between RV and LV contractions. Double-peaked waveforms for RVP and pulmonary flow (RVF) occurred over a wide range (0 to 300 ms) of pacing intervals between the RV and LV. One derivative peak always followed RV contraction for RVP and RVF (r = 0.971 +/- .011, P less than 0.01: r = 0.972 +/- .012, p less than 0.01; respectively). The second derivative peak was unrelated to the RA-RV pacing interval (r = 0.297 +/- .191, P greater than 0.5 RVP; 4 = 0.237 +/- .278, P greater than 0.5 RVF), but corresponded to the maximal LVP rise. Additionally, the magnitude of the two derivative peaks was similar when the ventricles contracted synchronously. When RV contraction preceded or followed LV contraction, the derivative peak associated with LV contraction was significantly greater (P less than 0.05, range 2.1 +/- 0.6 to 6.7 +/- 1.6 for RVP; P less than 0.05 range 1.9 +/- 0.4 to 6.7 +/- 1.5 for RVF) than the derivative associated with RV contraction. These data demonstrate a normally present, large LV assistance to RV contraction and may help to explain the RV response to myocardial infarction.

Effect of the right ventricular isolation procedure on ventricular vulnerability to fibrillation

A certain critical mass of myocardium is believed to be necessary to initiate ventricular fibrillation. The right ventricular isolation procedure, employed clinically to confine ventricular tachyarrhythmias to the right ventricle, decreases the ventricular mass available for fibrillation by isolating the ventricles from each other. The effect of this procedure on ventricular fibrillation thresholds is unknown. Left and right ventricular fibrillation thresholds were measured before and after right ventricular isolation in 10 adult mongrel dogs utilizing a single 5 ms stimulus of increasing current strength applied to the epicardium during the vulnerable period. There were no significant differences in heart rate, aortic blood pressure, left atrial pressure, temperature, arterial blood gases or regional myocardial blood flow between the study periods. In 9 of the 10 dogs, the isolated right ventricle could not sustain ventricular fibrillation despite the utilization of stimulus strengths of up to 80 mA. In the 10th dog, the right ventricular fibrillation threshold increased 150%, from 20 to 50 mA. The left ventricular fibrillation threshold markedly increased in every dog, with an average increase from 23 +/- 2 to 40 +/- 4 mA (p less than 0.0005). To determine whether time, cardiopulmonary bypass or the right ventricular incision could cause similar changes in ventricular fibrillation threshold, five different dogs underwent the entire experimental protocol except for incomplete isolation of the right ventricle. There were no significant changes in ventricular fibrillation thresholds in these dogs. Thus, in the canine model, right ventricular isolation can prevent the occurrence of sustained fibrillation in the isolated right ventricle and can significantly increase the left ventricular fibrillation threshold.

Surgical ablation for idiopathic ventricular tachycardia

A 33-year-old man with a right-bundle branch, left-axis deviation ventricular tachycardia was medically treated unsuccessfully. Surgical mapping and ablation was performed with a successful surgical result. A discussion of surgical results for this problem is provided.

Surgical treatment of dysrhythmias in infants and children

The recognition of medically refractory dysrhythmias in children has necessitated the use of more invasive nonpharmacologic therapies. The role of ablative surgery in the management of pediatric rhythm disturbances is presented.

Nonischemic sustained ventricular tachycardia: clinical outcome in 12 patients with arrhythmogenic right ventricular dysplasia

The clinical course and long-term follow-up of 12 patients with arrhythmogenic right ventricular dysplasia causing ventricular tachycardia are presented. No patient had a history of congestive heart failure and the cardiothoracic ratio measured less than or equal to 0.5 in all patients. All 12 patients were symptomatic during ventricular tachycardia; syncope occurred in 4. Exercise-related symptoms were present in 8 (73%) of 11 patients. The mean right ventricular ejection fraction was 31% (range 20% to 54%), and the mean left ventricular ejection fraction was 68% (range 44% to 88%). Signal averaging of the rest electrocardiogram (ECG) revealed late potentials in five of eight patients. During programmed electrical stimulation, sustained or nonsustained ventricular tachycardia showing a left bundle branch block configuration was induced in all patients. One patient underwent right ventricular disconnection and died 1 week after operation of low cardiac output failure. The remaining 11 patients were all treated medically and are alive at a mean follow-up time of 7.9 years after the onset of symptoms. Recurrence of symptomatic and documented sustained monomorphic ventricular tachycardia occurred in eight patients and could not be predicted by results of long-term ECG monitoring, treadmill exercise testing or programmed stimulation. In conclusion, despite recurrence of ventricular tachycardia, patients with arrhythmogenic right ventricular dysplasia have a favorable outcome when treated medically. Noninvasive studies (imaging techniques, ambulatory ECG monitoring and exercise testing) provide data that may be sufficient in diagnosing arrhythmogenic right ventricular dysplasia.

Right ventricular free wall isolation: effects on regional myocardial blood flow

The right ventricular isolation procedure was developed to treat medically refractory, nonischemic right ventricular tachycardia. The effect of this procedure on regional myocardial blood flow to the isolated right ventricle was evaluated in 10 adult mongrel dogs. There were no significant changes in aortic pressure, right ventricular systolic or diastolic pressure, or cardiac index following right ventricular isolation when the left ventricle and right ventricular free wall were synchronously paced. Myocardial blood flow to the isolated right ventricle was unchanged following the procedure (0.85 +/- 0.07 ml/min/gm to 0.87 +/- 0.08 ml/min/gm; p = not significant). Analysis of regional flow revealed that only a thin rim of right ventricular tissue near the ventriculotomy showed a significant decrease in blood flow (1.10 +/- 0.1 ml/min/gm to 0.29 +/- 0.04 ml/min/gm; p less than 0.05). Thus, this procedure leaves intact the blood supply to the great percentage of the right ventricular free wall. This finding supports the concept that the right ventricular isolation procedure is effective in isolating abnormal electrical activity without compromising regional myocardial blood flow.

Hemodynamic consequences of right ventricular isolation: the contribution of the right ventricular free wall to cardiac performance

Surgical isolation of the right ventricular free wall was performed in 10 dogs to evaluate both the hemodynamic effects of the procedure and the postoperative contribution of right ventricular free wall contraction to overall cardiac performance. Following the procedure, there was no significant differences in peak right ventricular systolic pressure, right atrial pressure, right ventricular stroke volume, or cardiac index. Cardiac index remained at preoperative levels over a wide range of filling pressures. However, there was a significant decrease in right ventricular stroke work (6.0 +/- 1.3 gm-m/m2 to 5.1 +/- 0.5 gm-m/m2; p less than 0.05). Pacing the isolated right ventricular free wall resulted in marked hemodynamic improvement compared with an electrically silent right ventricular free wall. Cardiac index increased from 1.7 +/- 0.2 L/min/m2 to 2.6 +/- 0.2 L/min/m2 (p less than 0.0005), and right ventricular stroke work went from 3.0 +/- 0.6 gm-m/m2 to 6.4 +/- 0.9 gm-m/m2 (p less than 0.0005). Right ventricular performance was also significantly related to the timing of right ventricular free wall contraction. Thus, the right ventricular free wall played an important role in the maintenance of normal cardiac hemodynamics.

Results of electrical fulguration in arrhythmogenic right ventricular disease

Eleven patients with sustained ventricular tachycardia (VT) refractory to antiarrhythmic drugs due to right ventricular disease shown by angiography underwent fulguration. Seven patients always had VT with the same morphology, and 4 had clinical VT with 2 or 3 different QRS waveforms. Five patients underwent a single fulguration and the other 6 underwent from 2 to 5 procedures; 2 to 14 shocks (mean 6) of 150 to 250 J were used. No serious complications occurred. At 31.5 +/- 9 months of follow-up, the arrhythmia was controlled in 8 patients, with continuation of previously ineffective antiarrhythmic drug therapy in 6 of 8. The number of VT episodes the year before and after fulguration was 0.5 +/- 0.7 vs 3.5 +/- 1.7 (p less than 0.001). There was no statistically significant difference between the success rate and the degree of prematurity of the onset of the local electrogram during VT: -36 +/- 31 ms for successes and -38 +/- 13 ms for failures. In 7 patients with monomorphic VT, there were 6 successes and 1 failure, and in 4 patients with several morphologies of VT, there were 2 successes and 2 failures (1 due to the appearance of a "new" VT). Thus, electrical fulguration of VT in patients with right ventricular disease is safe and most often effective, particularly in patients with monomorphic VT, when combined with antiarrhythmic drugs. In these patients, the usually recommended endocardial mapping criteria for the determination of the optimal fulguration site were not predictive of outcome. Further studies are necessary to better define the optimal site for fulguration.

Surgical treatment of arrhythmias

Surgical treatment of arrhythmias is often more expeditious and more cost-effective in the long run than pharmacologic therapy. In the past, surgical treatment of arrhythmias has been reserved for patients with disabling paroxysmal or incessant tachycardia refractory to medical management, severe life-threatening arrhythmia or aborted episodes of sudden death. However, tachyarrhythmias that are refractory to pharmacologic therapy because of drug inefficacy, noncompliance or limiting side effects are not uncommon. Although nonpharmacologic treatment of arrhythmias carries with it a one-time period of higher risk (i.e., when the patient undergoes surgery), it is curative and often preferable to the uncertainty and possibly higher cumulative risk associated with medical management.

Electrophysiologic effects of surgical isolation of the right ventricle

Surgical isolation of the entire right ventricular free-wall was performed in ten dogs to evaluate the effects of the procedure on a variety of electrophysiologic measurements. Complete surgical isolation of the right ventricle was confirmed by determining that right ventricular electrical activity was not conducted to the remainder of the heart and that electrical activity in the atria or left ventricle did not conduct to the right ventricle. Right ventricular isolation caused no change in right ventricular or left ventricular pacing thresholds, in effective refractory periods of the right ventricle or left ventricle, or in right ventricular free-wall conduction time. Moreover, the normal conduction time from the right atrium to the left ventricle was 139 +/- 5 msec (mean +/- standard error) preoperatively and 135 +/- 5 msec postoperatively (p is not significant), showing that atrial-to-left ventricular synchrony was unaltered by isolation of the right ventricle. However, following isolation, the right ventricle could not be electrically fibrillated in 9 of 10 animals, a finding that may have important implications in the future development of surgical procedures to control chronic, life-threatening ventricular tachyarrhythmias.