Charles D. Gottlieb

Repetitive monomorphic tachycardia from the left ventricular outflow tract : Electrocardiographic patterns consistent with a left ventricular site of origin

OBJECTIVES This study sought to characterize the electrocardiographic patterns predictive of left ventricular sites of origin of repetitive monomorphic ventricular tachycardia (RMVT). BACKGROUND RMVT typically arises from the right ventricular outflow tract (RVOT) in patients without structural heart disease. The incidence of left ventricular sites of origin in this syndrome is unknown. METHODS Detailed endocardial mapping of the RVOT was performed in 33 consecutive patients with RMVT during attempted radiofrequency ablation. Left ventricular mapping was also performed if pace maps obtained from the RVOT did not reproduce the configuration of the induced tachycardia. RESULTS Pace maps identical in configuration to the induced tachycardia were obtained from the RVOT in 29 of 33 patients. Application of radiofrequency energy at sites guided by pace mapping resulted in elimination of RMVT in 24 (83%) of 29 patients. In four patients (12%), pace maps obtained from the RVOT did not match the induced tachycardia. All four patients had a QRS configuration during RMVT with precordial R wave transitions at or before lead V2. In two patients, RMVT was mapped to the mediosuperior aspect of the mitral valve annulus, near the left fibrous trigone; catheter ablation at that site was successful in both. In two patients, RMVT was mapped to the basal aspect of the superior left ventricular septum. Catheter ablation was not attempted because His bundle deflections were recorded from this site during sinus rhythm. CONCLUSIONS RMVT can arise from the outflow tract of both the right and left ventricles. RMVTs with a precordial R wave transition at or before lead V2 are consistent with a left ventricular origin.

Conduction block in the inferior vena caval-tricuspid valve isthmus : Association with outcome of radiofrequency ablation of type I atrial flutter

OBJECTIVES We sought to 1) correlate conduction block in the isthmus of the right atrium between the inferior vena cava and the tricuspid annulus with the efficacy of catheter ablation of type I atrial flutter, and 2) characterize the effects of ablative lesions on the properties of isthmus conduction. BACKGROUND There are few data on the mechanism of persistent suppression of recurrence of atrial flutter by catheter ablation. METHODS Thirty-five patients with type I atrial flutter underwent catheter mapping and ablation. Radiofrequency lesions were applied in the isthmus. Transisthmus conduction before and after the lesions was assessed during atrial pacing in sinus rhythm from the medial and lateral margins of the isthmus at cycle lengths of 600, 400 and 300 ms and the native flutter cycle length. Isthmus conduction block was defined using multipolar recording techniques. There were three treatment groups: group 1 = radiofrequency energy applied during flutter, until termination (n = 14); group 2 = radiofrequency energy applied during atrial pacing in sinus rhythm from the proximal coronary sinus at a cycle length of 600 ms, until isthmus conduction block was observed (n = 14); and group 3 = radiofrequency energy applied until an initial flutter termination, after which further energy was applied during atrial pacing in sinus rhythm until isthmus conduction block was observed (n = 7). RESULTS In group 1, after the initial flutter termination, isthmus conduction block was observed in 9 of the 14 patients. In each of these nine patients, flutter could not be reinitiated. In each of the remaining five patients, after the initial flutter termination, isthmus conduction was intact and atrial flutter could be reinitiated. Ultimately, successful ablation in each of these patients was also associated with isthmus conduction block. In groups 2 and 3, isthmus conduction block was achieved during radiofrequency energy application, and flutter could not subsequently be reinitiated. Before achieving conduction block, marked conduction slowing or intermittent block, or both, was observed in some patients. In some patients, isthmus conduction block was pacing rate dependent. In addition, recovery from conduction block was common in the laboratory and had a variable time course. At a mean follow-up interval of 10 months (range 1 to 21), the actuarial incidence of freedom from type I flutter was 80% (recurrence in three patients at 7 to 15 months). CONCLUSIONS Isthmus conduction block is associated with flutter ablation success. Conduction slowing or intermittent block, or both, in the isthmus can occur before achieving persistent block. Recovery of conduction after achieving block is common. Follow-up has revealed a low rate of flutter recurrence after achieving isthmus conduction block, whether the block was achieved in conjunction with termination of flutter.

Mechanisms of Death in the CABG Patch Trial A Randomized Trial of Implantable Cardiac Defibrillator Prophylaxis in Patients at High Risk of Death After Coronary Artery Bypass Graft Surgery

BACKGROUND The CABG Patch trial compared prophylactic implantable cardiac-defibrillator (ICD) implantation with no antiarrhythmic therapy in coronary bypass surgery patients who had a left ventricular ejection fraction <0.36 and an abnormal signal-averaged ECG. There were 102 deaths among the 446 ICD group patients and 96 deaths among the 454 control group patients, a hazard ratio of 1.07 (P=0.63). The mechanisms of death were classified, and hypotheses were tested about the effects of ICD therapy on arrhythmic and nonarrhythmic cardiac deaths in the CABG Patch Trial and the Multicenter Automatic Defibrillator Implantation Trial (MADIT). METHODS AND RESULTS The 198 deaths in the trial were reviewed by an independent Events Committee and classified by the method of Hinkle and Thaler. Only 54 deaths (27%) occurred out of hospital; 145 deaths (73%) were witnessed. Seventy-nine (82%) of the 96 deaths in the control group and 76 (75%) of the 102 deaths in the ICD group were due to cardiac causes. Cumulative arrhythmic mortality at 42 months was 6.9% in the control group and 4.0% in the ICD group (P=0. 057). Cumulative nonarrhythmic cardiac mortality at 42 months was 12. 4% in the control group and 13.0% in the ICD group (P=0.275). Death due to pump failure was significantly associated with death >1 hour from the onset of symptoms, dyspnea within 7 days of death, and overt heart failure within 7 days of death. CONCLUSIONS In the CABG Patch Trial, ICD therapy reduced arrhythmic death 45% without significant effect on nonarrhythmic deaths. Because 71% of the deaths were nonarrhythmic, total mortality was not significantly reduced.

Relation of the intraoperative defibrillation threshold to successful postoperative defibrillation with an automatic implantable cardioverter defibrillator

To determine the relation between the intraoperative defibrillation threshold and successful postoperative termination of induced ventricular fibrillation (VF) with the automatic implantable cardioverter defibrillator (AICD), 33 patients who underwent AICD implantation were studied. The defibrillation threshold, determined after at least 10 seconds of VF, was 5 J in 2, 10 J in 6, 15 J in 10, 20 J in 10 and 25 J in 5 patients. The AICD energy rating on the first discharge was 28 +/- 1.8 J. Defibrillation of induced VF was demonstrated postoperatively in 29 of 33 (88%) patients. The AICD terminated VF postoperatively in all 18 patients with a defibrillation threshold less than or equal to 15 J. Only 11 of the 15 (73%) patients with a defibrillation threshold greater than or equal to 20 J (p less than 0.04) had VF terminated postoperatively. In all 4 patients in whom the AICD failed to terminate induced VF, the energy difference between the AICD rating and the defibrillation threshold was less than or equal to 10 J. Among the 14 patients with a difference of less than or equal to 10 J between the AICD energy rating and the defibrillation threshold, there were no significant differences between the 4 patients with and the 10 without successful VF termination with respect to the duration of VF induced postoperatively or the AICD lead system. In summary, failure to terminate VF with the AICD is not uncommon (27%) when the defibrillation threshold approaches the energy delivering capacity of the AICD.(ABSTRACT TRUNCATED AT 250 WORDS)

Narrowing of the Superior Vena Cava-Right Atrium Junction During Radiofrequency Catheter Ablation for Inappropriate Sinus Tachycardia: Analysis With Intracardiac Echocardiography

OBJECTIVES The study explored the potential for tissue swelling and venous occlusion during radiofrequency (RF) catheter ablation procedures using intracardiac echocardiography (ICE). BACKGROUND Transient superior vena cava occlusion has been reported following catheter ablation procedures for inappropriate sinus tachycardia (IST). Presumably, venous occlusion could occur owing to thrombus formation or tissue swelling with resultant narrowing of the superior vena cava-right atrial (SVC-RA) junction. METHODS Intracardiac echocardiography (9 MHz) was used to guide ablation catheter position and for continuous monitoring during RF application in 13 ablation procedures in 10 patients with IST. The SVC-RA junction was measured prior to and following ablation. Successful ablation was marked by abrupt reduction in the sinus rate and a change to a superiorly directed p-wave axis. RESULTS Eleven of 13 procedures were successful, requiring 29 +/- 20 RF lesions. Prior to the delivery of RF lesions, the SVC-RA junction measured 16.4 +/- 2.9 mm. With RF delivery, local and circumferential swelling was observed, causing progressive reduction in the diameter of the SVC-RA junction to 12.6 +/- 3.3 mm (24% reduction, p = 0.0001). A reduction in SVC-RA orifice diameter of > or = 30% compared to baseline was observed in five patients. CONCLUSIONS The delivery of multiple RF ablation lesions, often necessary for cure of IST, can cause considerable atrial swelling and resultant narrowing of the SVC-RA junction. Smaller venous structures, such as the coronary sinus and the pulmonary veins, would also be expected to be vulnerable to this complication. Thus, ICE imaging may be helpful in preventing excessive tissue swelling leading to venous occlusion during catheter ablation procedures.

Postoperative lead-related complications in patients with nonthoracotomy defibrillation lead systems

OBJECTIVES This study sought to document postoperative complications attributable to nonthoracotomy defibrillation lead systems in a large cohort. BACKGROUND The incidence of postoperative complications specifically associated with nonthoracotomy defibrillation lead systems is unknown. METHODS Postoperative lead-related complications were evaluated in 170 patients with a nonthoracotomy defibrillation lead system who were followed up for a mean (+/- SD) of 17 +/- 12 months. Each system incorporated one or more intravascular leads. In 117 patients (69%), the system incorporated a subcutaneous defibrillation patch. All implantations were performed in an operating room by cardiothoracic surgeons. Defibrillation thresholds were measured at implantation, before hospital discharge (mean 3 +/- 2 days) and at 4 to 18 weeks after implantation. Patients were evaluated every 2 to 3 months after implantation or as indicated by clinical exigency. RESULTS Twenty-seven patients (15.9%) were diagnosed with a lead-related complication that either extended the initial hospital period or led to a second hospital admission. Complications included endocardial lead or subcutaneous defibrillation patch dislodgment in eight patients (4.7%), which was diagnosed between 2 and 345 days after implantation; endocardial or subcutaneous patch lead fracture in six (3.5%), which was diagnosed between 53 and 600 days after implantation; subcutaneous patch mesh fracture in one, which was diagnosed at 150 days after implantation; subclavian vein thrombosis in three (1.8%), which was diagnosed at 2 to 50 days after implantation; and unacceptably elevated defibrillation threshold (within 5 J of maximal device output) in nine (5.3%), which was documented at one of the two postimplantation evaluations in eight patients or at the time of failure to terminate a spontaneous ventricular tachycardia in one. Seventeen of the 27 patients required reoperation for correction of their complication. In addition, system infection requiring complete explantation occurred in seven other patients (4.1%) at an interval from implantation ranging from 14 to 120 days. CONCLUSIONS Postoperative complications related to a nonthoracotomy defibrillation lead system were common and frequently required reoperation for correction. The rate of system explantation due to infection was also significant. Postoperative defibrillation testing and vigilant outpatient follow-up evaluation are necessary to ensure normal lead function.

Intracardiac echocardiography (9 MHz) in humans: methods, imaging views and clinical utility

A new low-frequency (9 MHz, 9 Fr) catheter-based ultrasound (US) transducer has been designed that allows greater depth of cardiac imaging. To demonstrate the imaging capability and clinical utility, intracardiac echocardiography (ICE) using this lower frequency catheter was performed in 56 patients undergoing invasive electrophysiological procedures. Cardiac imaging and monitoring were performed with the catheter transducer placed in the superior vena cava (SVC), right atrium (RA) and/or right ventricle (RV). In all patients, ICE identified distinct endocardial structures with excellent resolution and detail, including the crista terminalis, RA appendage, caval and coronary sinus orifices, fossa ovalis, pulmonary vein orifices, ascending aorta and its root, pulmonary artery, RV and all cardiac valves. The left atrium and ventricle were imaged with the transducer at the limbus fossa ovalis of the interatrial septum and in the RV, respectively. ICE was important in identifying known or unanticipated aberrant anatomy in 11 patients (variant Eustachian valve, atrial septal aneurysm and defect, lipomatous hypertrophy, Ebsteins anomaly, ventricular septal defect, tetralogy of Fallot, transposition of the great arteries, disrupted chordae tendinae and pericardial effusion) or in detecting procedure-related abnormalities (narrowing of SVC-RA junction orifice or pulmonary venous lumen, atrial thrombus, interatrial communication). In patients with inappropriate sinus tachycardia, ICE was the primary ablation catheter-guidance technique for sinus node modification. With ICE monitoring, the evolution of lesion morphology with the three imaging features including swelling, dimpling and crater formation was observed. In all patients, ICE was contributory to the mapping and ablation process by guiding catheters to anatomically distinct sites and/or assessing stability of the electrode-endocardial contact. ICE was also used to successfully guide atrial septal puncture (n = 9) or RA basket catheter placement (n = 4). Thus, ICE with a new 9-MHz catheter-based transducer has better imaging capability with a greater depth. Normal and abnormal cardiac anatomy can be readily identified. ICE proved useful during electrophysiological mapping and ablation procedures for guiding interatrial septal puncture, assessing placement and contact of mapping and ablation catheters, monitoring ablation lesion morphological changes, and instantly diagnosing cardiac complications.

Utility of the 12-lead electrocardiogram in localizing the origin of right ventricular outflow tract tachycardia

The purpose of this investigation was to develop an algorithm on the basis of the QRS morphology observed on the 12-lead ECG that would rapidly locate the site of origin of the monomorphic ventricular tachycardia arising from the septal portion of the RVOT. Radiofrequency catheter ablation guided by pace-mapping techniques has proven effective in eliminating the ventricular tachycardia originating from the RVOT in the absence of structural heart disease. A method that would rapidly identify the portion of the RVOT septum toward which more detailed pace-mapping should be directed before catheter ablation would be useful in decreasing procedure time and radiation exposure and potentially facilitating a successful ablation procedure. The RVOT septum was divided into nine sites. In 11 patients, bipolar pacing was performed at each of the nine designated sites to mimic ventricular tachycardia. A standard 12-lead surface ECG was recorded during pacing. The QRS morphology in the limb leads was characterized and the site of the R-wave transition was determined in the precordial leads. A QS in lead a VR and a monophasic R wave in leads II, III, aVF, and V6 were noted in each patient at all paced sites. In lead I, pacing at the three posterior septal sites always resulted in an R wave. Pacing at the three anterior sites produced a dominant Q wave (either QS or Qr) at 17 (52%) of 33 sites or a qR complex at 16 (48%) of 33 sites.(ABSTRACT TRUNCATED AT 250 WORDS)

ICD Data Storage: Value in Arrhythmia Management

Sophisticated diagnos tic information is provided by the latest generation of implantable defibriliators. The success of therapy and the type of therapy successful in terminating ventricular arrhythmias is provided by interrogating the ICD device. In addition, R to R interval information can be retrieved. In selected devices, either locai bipolar electrograms from the rate sensing leads or wide bipolar electrograms from the energy delivering leads provide visual confirmation of the presence of ventricular tachyarrhythmic events loading to ther apy. The value and limilations of this sophisticated diagnostic information in providing insight into the electrical events triggering therapy and the events triggering ventricular arrhythmias are discussed.

Rapid Ventricular Pacing in a Pacemaker Patient Undergoing Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) generates potent electromagnetic forces in the form of a static, gradient, or pulsed radiofrequency magnetic field that can result in pacemaker malfunction. This report documents a case of rapid cardiac pacing during MRI in a patient with a dual chamber pacemaker. Although the mechanism of rapid cardiac pacing is unclear, it was directly related to radiofrequency pulsing. We postulated that the lead acts as an antenna for radiofrequency energy that interacts with the pacemakers output circuit, thus, causing cardiac pacing at a cycle length representing a multiple of the repetition time; or perhaps rapid pacing is related to induced currents generated between the MRI unit and the pacing lead.