Yasuteru Yamauchi

Demonstration of diastolic and presystolic Purkinje potentials as critical potentials in a macroreentry circuit of verapamil-sensitive idiopathic left ventricular tachycardia.

OBJECTIVES The purpose of this study was to determine the relation of diastolic and presystolic potentials recorded during verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) to reentry circuit. BACKGROUND Successful ablation of verapamil-sensitive ILVT at the zone of slow conduction from which the diastolic potential is recorded has been reported. However, the relationship between the diastolic potential and the reentrant circuit remains a matter of debate. METHODS Radiofrequency (RF) ablation was performed in 20 patients with verapamil-sensitive ILVT. After identifying the ventricular tachycardia (VT) exit site, we searched for the mid-diastolic potential (P1) during VT. Entrainment followed by RF current application was performed. If the mid-diastolic potential could not be detected, RF current was applied at the VT exit site showing the earliest ventricular activation with a single fused presystolic Purkinje potential (P2). RESULTS In 15 of 20 patients, both P1 and P2 were recorded during VT from midseptal region. Entrainment pacing captured P1 orthodromically and reset the VT. The interval from stimulus to P1 was prolonged as the pacing rate was increased. Radiofrequency ablation was successfully performed at this site in all 15 patients. After successful ablation, P1 appeared after the QRS complex during sinus rhythm with the identical sequence to that during VT. In the remaining five patients, the diastolic potential could not be detected, and a single fused P2 was recorded only at the VT exit site. Successful ablation was performed at this site in all five patients. CONCLUSIONS This study demonstrates that P1 and P2 are critical potentials in a circuit of verapamil-sensitive ILVT and suggests the presence of a macroreentry circuit involving the normal Purkinje system and the abnormal Purkinje tissue with decremental property and verapamil-sensitivity.

Electrocardiographic Characteristics of Left Ventricular Outflow Tract Tachycardia

Catheter ablation of idiopathic left ventricular outflow tract tachycardia (LVOT‐VT) is rare because a safe ablation technique at this site has not been described, and serious complications may occur. This study compared the QRS morphology of LVOT‐VT with that of idiopathic right ventricular outflow tract tachycardia. A comparison was made between the electrocardiographic characteristics of LVOT‐VT originating from the supravalvular region of a coronary cusp (Supra‐Ao group) with those of LVOT‐VT originating from the infravalvular endocardial region of a coronary cusp of the aortic valve within the LV (Infra‐Ao group). After precise mapping of the right ventricle, left ventricle, pulmonary artery, coronary cusps, and proximal portion of the anterior interventricular vein, there were 17 patients in whom VT was thought to be located at the LVOT by both activation and pace mapping. They were divided between a Supra‐Ao group (n = 8), and an Infra‐Ao group (n = 9). Analysis of the 12‐lead electrocardiogram (ECG) revealed an S wave in lead I in all 17 patients. A precordial R wave transition was also observed at V1 or V2 in 16 patients (94%). In 7 of 8 patients (88%) with Supra‐Ao LVOT‐VT, no S wave was observed in either V5 or V6. In contrast, an Rs pattern was observed in both V5 and V6, or in V6 only, in 100% of the patients with Infra‐Ao LVOT‐VT. A LVOT‐VT should be suspected when the ECG shows an S wave in lead I and an R/S ratio greater than 1 in lead V1 or V2, versus a coronary cusp location if there is no S wave in either lead V5 or V6.

Oxygen uptake kinetics are determined by cardiac function at onset of exercise rather than peak exercise in patients with prior myocardial infarction.

BACKGROUND Resting cardiac function does not necessarily affect exercise capacity. However, to determine whether it affects early dynamics of oxygen uptake (VO2) during exercise, we measured VO2 during a constant work rate and during incremental exercise testing in patients with a history of myocardial infarction. VO2 kinetics and exercise capacity were compared between patients with relatively high left ventricular ejection fractions (LVEF > or = 35%, group 1) and those with lower ejection fractions (LVEF < 35%, group 2). METHODS AND RESULTS Forty patients with a history of prior myocardial infarction (age, 57 +/- 10 years) were monitored during 6 minutes of moderate constant work rate testing (40 +/- 8 W) and during symptom-limited incremental exercise testing with a cycle ergometer. VO2 was calculated from respired gas analysis on a breath-by-breath basis. Cardiac output determinations were made with a computerized cadmium telluride detector every 10 seconds during exercise. The VO2 time constant during constant work rate exercise was slower in group 2 (58.0 +/- 7.6 seconds) compared with group 1 (45.8 +/- 10.5 seconds, P = .0002), indicating slower kinetics in group 2. The time constant for the rise in cardiac output during exercise was also slower in patients with lower EFs (63.0 +/- 12.8 versus 50.0 +/- 12.2 seconds). However, there were no differences in exercise capacity parameters, such as the VO2 or cardiac output at peak exercise, obtained during incremental exercise testing among the two groups. CONCLUSIONS The prolonged time constant of VO2, which is primarily determined during early parts of exercise, reflects delayed cardiac output response in patients with severely impaired LV function. The time constant of VO2 during submaximal constant work rate exercise can be used as a sensitive and discriminant measure of impaired cardiac reserve in these patients.

Electrocardiographic Characteristics of the Variants of Idiopathic Left Ventricular Outflow Tract Ventricular Tachyarrhythmias

Background: Despite similar QRS morphology, idiopathic repetitive monomorphic ventricular tachyarrhythmias (VTs) of left ventricular outflow tract (LVOT) are known to have the variants of different adjacent origins, including the aorto‐mitral continuity (AMC), anterior site around the mitral annulus (MA), aortic sinus cusps (ASC), and epicardium. However, the electrocardiographic characteristics of those variants previously have not been evaluated fully.

Enhancement of J–ST-Segment Elevation by the Glucose and Insulin Test in Brugada Syndrome

NOGAMI, A., et al.: Enhancement of J–ST‐Segment Elevation by the Glucose and Insulin Test in Brugada Syndrome. The effects of glucose and insulin on J–ST‐segment elevation were evaluated in seven men (mean age 45 ± 10 years) with Brugada syndrome. Six patients had been reanimated from VF and one patient had experienced syncope. The effects of intravenous (1) pilsicainide 50 mg, (2) glucose 50 g, and (3) glucose 50 g plus regular insulin 10 IU on the precordial ECG leads were examined. Pilsicainide significantly enhanced J‐ST elevation in all patients and induced VF in 1 patient. A significant accentuation of the abnormal J‐ST configuration was observed in all patients at a mean of 51 ± 40 minutes after glucose and insulin infusion. Changes in blood glucose and serum potassium concentration were 111 ± 158 mg/dL and −0.30 ± 0.48 mEq/L , respectively. These changes were not directly related to the ECG changes. Glucose infusion without insulin caused a subtle increase in J‐ST elevation. In conclusion, the administration of glucose and insulin safely unmasked or accentuation the J–ST‐segment elevation in Brugada syndrome. Blood glucose and insulin concentrations may be factors modulating the circadian or day‐to‐day ECG variations in this syndrome. (PACE 2003; 26[Pt. II]:332–337)

Superior vena cava as initiator of atrial fibrillation: factors related to its arrhythmogenicity.

BACKGROUND The superior vena cava (SVC) is an important focus of atrial fibrillation (AF) for which SVC isolation is effective. However, SVC isolation may cause serious complications, and indications for SVC isolation combined with pulmonary vein (PV) isolation are unclear. OBJECTIVE The purpose of this study was to identify structural and electrophysiologic differences that might exist between the SVC of patients with and those without SVC triggering of AF. METHODS This study included paroxysmal (n = 46) and persistent (n = 14) AF patients without structural heart disease who underwent circumferential antral PV isolation. Patients with AF of SVC origin were assigned to the SVC group (n = 12); the remaining patients were assigned to the control group (n = 48). The area where SVC potentials were recorded was defined as the SVC sleeve. The length of the SVC sleeve and the maximum amplitude of the SVC potential were measured. RESULTS SVC group patients had a longer SVC sleeve (34.7 +/- 4.4 mm vs 16.5 +/- 11.4 mm, P <.0001) than did control group patients. Maximum amplitude of the SVC potential was greater in SVC group patients than in control group patients (1.50 +/- 0.43 mV vs 0.98 +/- 0.60 mV, P = .03). SVC sleeve length >30 mm and maximum amplitude of SVC potential >1.0 mV strongly predicted an SVC focus of AF (100% sensitivity, 94% specificity). Fifty of 60 patients became AF-free without antiarrhythmic drugs after undergoing circumferential antral PV isolation and/or SVC isolation. CONCLUSION The results of this study suggest that in patients with long SVC sleeve (>30 mm) and large SVC potential (>1.0 mV), arrhythmogenic triggers of AF reside in the SVC.

Systematic Treatment Approach to Ventricular Tachycardia in Cardiac Sarcoidosis

Background—Fatal arrhythmia is commonly observed in cardiac sarcoidosis, but clinical effects of a systematic treatment approach are still uncertain. This study sought to describe both clinical and electrophysiological characteristics and outcomes of systematic treatment approach to ventricular tachycardia (VT) associated with cardiac sarcoidosis. Methods and Results—We enrolled 37 consecutive patients (11 men; age, 56±11 years) with a diagnosis of sustained VT associated with cardiac sarcoidosis. Clinical effects of a systematic treatment approach including medical therapy (both steroid and antiarrhythmic agents), in association with radiofrequency catheter ablation, were evaluated. All patients received antiarrhythmic agents, and 34 received steroid therapy. During a 39-month follow-up, 23 (62%) patients were free from any VT episodes with medical therapy. Multivariable Cox regression analyses revealed that the absence of gallium-67 myocardial uptake was an independent predictor for VT recurrence (hazard ratio, 7.51; 95% confidence interval, 1.65–34.26; P<0.01). Fourteen patients who experienced VT recurrences even while on drug therapy underwent radiofrequency catheter ablation. Electrophysiological study revealed that the mechanisms of VTs could be classified into 2 subgroups: Purkinje-related or scar-related VT. The QRS duration of VT was narrower in Purkinje-related than in scar-related VTs (157±23 versus 183±22 ms; P<0.05). After a 33-month follow-up subsequent to the radiofrequency catheter ablation, 6 of 14 patients experienced VT recurrence. The number of VTs sustained during electrophysiological study was higher in the patients with VT recurrence than in those without (3.7±1.4 versus 1.9±0.8; P<0.01). Conclusions—A systematic treatment approach to cardiac sarcoidosis with VT successfully suppressed VT recurrences in the majority of patients studied.

Catheter Ablation of Ventricular Tachycardia in Patients with Right Ventricular Dysplasia: Identification of Target Sites by Entrainment Mapping Techniques

Objective: To identify target sites for radiofrequency ablation of ventricular tachycardia (VT) by entrainment mapping techniques in patients with arrhythmogenic right ventricular dysplasia. Methods: Entrainment mapping and radiofrequency ablation of eight VTs was performed in seven patients. Radiofrequency ablation was applied at 31 reentry circuits sites that were classified based on findings during entrainment. Results: By entrainment criteria the 31 sites were classified as: exit sites (n = 12), proximal sites (n = 6), and outer loop sites (n = 13). Radiofrequency current application terminated VT at 7 of 31 sites: 2 of 12 exit sites (17%), 4 of 6 proximal sites (67%), and 1 of 13 outer loop sites (8%). Conclusion: Radiofrequency ablation terminated VTs most often at sites proximal to the exit as opposed to outer loop sites and exit sites (P = 0.05). The critical isthmus for ablation of VT in right ventricular dysplasia often may be distant to the exit.

Discrete Prepotential as an Indicator of Successful Ablation in Patients With Coronary Cusp Ventricular Arrhythmia

Background— Although coronary cusp (CC) ventricular arrhythmia (VA) can be treated by catheter ablation, reliable indicators of successful ablation sites have not been fully identified. Methods and Results— This study comprised 392 patients undergoing radiofrequency catheter ablation for outflow tract-VA at 3 institutions from January 2007 to August 2012. The successful ablation site was on the left CC or right CC in 35 (8.9%) of the 392 patients. In 9 (26%) of these 35 patients, a discrete prepotential was recognized, 5 of whom had left CC-VAs and 4 of whom had right CC-VAs. Radiofrequency catheter ablation was successful at the site of the prepotential in all 9 of these patients. The duration of the isoelectric line between the end of the discrete prepotential and the onset of the ventricular electrogram was 27±13 ms. The time from onset of the discrete prepotential at the successful ablation site on the CC to the QRS onset (activation time) was 69±20 ms (range, 50–98 ms). Pace mapping was graded as excellent at the successful ablation site in only 1 patient. No discrete prepotential was recorded in any successful right outflow tract-VA ablation case in this study. Conclusions— A discrete prepotential was seen in 9 (26%) of 35 patients with CC-VA. In left and right CC-VA, the site of a discrete prepotential with ≥50 ms activation time may indicate a successful ablation site.

Discrete Pre-Potential as an Indicator of Successful Ablation in Patients with Coronary Cusp Ventricular Arrhythmia

Background— Although coronary cusp (CC) ventricular arrhythmia (VA) can be treated by catheter ablation, reliable indicators of successful ablation sites have not been fully identified. Methods and Results— This study comprised 392 patients undergoing radiofrequency catheter ablation for outflow tract-VA at 3 institutions from January 2007 to August 2012. The successful ablation site was on the left CC or right CC in 35 (8.9%) of the 392 patients. In 9 (26%) of these 35 patients, a discrete prepotential was recognized, 5 of whom had left CC-VAs and 4 of whom had right CC-VAs. Radiofrequency catheter ablation was successful at the site of the prepotential in all 9 of these patients. The duration of the isoelectric line between the end of the discrete prepotential and the onset of the ventricular electrogram was 27±13 ms. The time from onset of the discrete prepotential at the successful ablation site on the CC to the QRS onset (activation time) was 69±20 ms (range, 50–98 ms). Pace mapping was graded as excellent at the successful ablation site in only 1 patient. No discrete prepotential was recorded in any successful right outflow tract-VA ablation case in this study. Conclusions— A discrete prepotential was seen in 9 (26%) of 35 patients with CC-VA. In left and right CC-VA, the site of a discrete prepotential with ≥50 ms activation time may indicate a successful ablation site.