Meiso Hayashi

Incidence and risk factors of arrhythmic events in catecholaminergic polymorphic ventricular tachycardia

Background— The pathophysiological background of catecholaminergic polymorphic ventricular tachycardia is well understood, but the clinical features of this stress-induced arrhythmic disorder, especially the incidence and risk factors of arrhythmic events, have not been fully ascertained. Methods and Results— The outcome in 101 catecholaminergic polymorphic ventricular tachycardia patients, including 50 probands, was analyzed. During a mean follow-up of 7.9 years, cardiac events defined as syncope, aborted cardiac arrest, including appropriate discharges from implantable defibrillators, or sudden cardiac death occurred in 27 patients, including 2 mutation carriers with normal exercise tests. The estimated 8-year event rate was 32% in the total population and 27% and 58% in the patients with and without &bgr;-blockers, respectively. Absence of &bgr;-blockers (hazard ratio [HR], 5.48; 95% CI, 1.80 to 16.68) and younger age at diagnosis (HR, 0.54 per decade; 95% CI, 0.33 to 0.89) were independent predictors. Fatal or near-fatal events defined as aborted cardiac arrest or sudden cardiac death occurred in 13 patients, resulting in an estimated 8-year event rate of 13%. Absence of &bgr;-blockers (HR, 5.54; 95% CI, 1.17 to 26.15) and history of aborted cardiac arrest (HR, 13.01; 95% CI, 2.48 to 68.21) were independent predictors. No difference was observed in cardiac and fatal or near-fatal event rates between probands and family members. Conclusions— Cardiac and fatal or near-fatal events were not rare in both catecholaminergic polymorphic ventricular tachycardia probands and affected family members during the long-term follow-up, even while taking &bgr;-blockers, which was associated with a lower event rate. Further studies evaluating concomitant therapies are necessary to improve outcome in these patients.

The role of stress test for predicting genetic mutations and future cardiac events in asymptomatic relatives of catecholaminergic polymorphic ventricular tachycardia probands

AIMSnCatecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmic disorder with a highly malignant clinical course. Exercise-stress test is the first-line approach to diagnose suspected individuals. We sought to elucidate the value of exercise-stress test for predicting mutations and future cardiac events in CPVT-family relatives.nnnMETHODS AND RESULTSnThe present study included 67 asymptomatic relatives (24 ± 15 years) of 17 genetically positive CPVT probands, who underwent exercise-stress test without any medication and genetic testing. Exercise-stress test, which was considered positive with the induction of ventricular tachycardia or premature ventricular contractions consisting of bigeminy or couplets, was positive in 17 relatives (25%). Genetic analysis disclosed mutations in 16 of these 17 relatives (94%) and in 16 of the 50 relatives (32%) with negative exercise-stress test; the sensitivity and specificity for a positive genotype were 50 and 97%, respectively (P< 0.001). Among 32 mutation carriers, cardiac events occurred in 7 of the 16 relatives with positive and 2 of the 16 relatives with negative exercise-stress test during the follow-up period of 9.6 ± 3.8 years, and four with positive and two with negative stress test were not on regular beta-blocker treatment at these events. In the 16 relatives with positive stress test, those on beta-blocker treatment demonstrated a trend of lower cardiac event rate (Log-rank P= 0.054).nnnCONCLUSIONnIn asymptomatic relatives of CPVT probands, exercise-stress test can be used as a simple diagnostic tool. Nevertheless, because of the low sensitivity for predicting mutations and future cardiac events in those with negative stress test, genetic analysis should be performed to improve patient management.

Ventricular Repolarization Restitution Properties in Patients Exhibiting Type 1 Brugada Electrocardiogram With and Without Inducible Ventricular Fibrillation

OBJECTIVESnThis study aimed to elucidate the contribution of the repolarization restitution property to the sustained ventricular fibrillation (VF) in Brugada syndrome.nnnBACKGROUNDnAlthough phase 2 re-entry develops as the trigger of VF, the other precipitating factors have remained unclear.nnnMETHODSnTwenty-one patients with a type 1 Brugada electrocardiogram underwent programmed electrical stimulation. Before the VF induction, single extrastimuli were delivered at 3 basic drive cycle lengths (BCLs) (400 ms, 600 ms, and 750 ms) from the right ventricular apex (RVA) and outflow tract (RVOT), and the activation recovery interval (ARI) was measured at 5-mm vicinity of the pacing site. The maximum ARI restitution slope was determined using the overlapping least-squares linear segments.nnnRESULTSnWe found that VF was inducible in 10 patients. A repeated-measure analysis of variance revealed that the slope in the RVA was steeper in patients with inducible VF than in those without but that in the RVOT was similar. The slope was steeper at longer BCLs and also steeper in the RVA than RVOT at BCLs of 600 and 750 ms. In patients with inducible VF, the percentage of patients exhibiting a slope >1 was 0%, 20%, and 75% in the RVA and 0%, 0%, and 14% in the RVOT at BCLs of 400 ms, 600 ms, and 750 ms, respectively. No patients without inducible VF had a slope >1.nnnCONCLUSIONSnThese results suggest the repolarization restitution property is a contributing factor to the propensity for VF in Brugada syndrome and, regarding this property, the RVA plays more important role than the RVOT.

High take-off left inferior pulmonary vein as an obstacle in creating a conduction block at the lateral mitral isthmus.

AIMSnCreation of complete linear lesions in the lateral mitral isthmus (LMI) by catheter ablation for treating atrial fibrillation remains technically challenging. We aimed to clarify whether a high take-off left inferior pulmonary vein (LIPV) can hamper the creation of a complete block at the LMI.nnnMETHODS AND RESULTSnWe included 81 consecutive patients who underwent linear ablation at the LMI and cardiac computed tomography (CT) before ablation. We defined a high take-off LIPV when the level of the lower edge of the LIPV ostium was higher than that of the top of mitral annulus on CT. The clinical backgrounds, parameters, and long-term follow-up were then compared between the success (successful creation of a complete LMI block) and failure groups. A complete LMI block was obtained in 60/81 (76%) patients. In the failure group, a high take-off LIPV was noted more commonly and the LMI tended to be longer than the success group. Multivariate analysis revealed that a high take-off LIPV was an independent predictor of failure to achieve a complete LMI block. The sinus rhythm maintenance rate was not different between the success and failure groups.nnnCONCLUSIONnA high take-off LIPV hampered the creation of complete linear lesions in the LMI.

Conduction through the lateral mitral isthmus: Block or pseudoblock?

The lateral mitral isthmus (LMI) between the mitral annulus and the left inferior pulmonary vein is one of the crucial targets for left atrial compartmentalization by catheter ablation, known to improve the sinus maintenance rate after ablation.1,2 A 63-year-old male patient was admitted to our hospital for catheter ablation treatment of persistent atrial fibrillation that had lasted for 6 months. After the four pulmonary veins were electrically disconnected, the linear ablation targeting the left atrial roof and the LMI was performed using an irrigated-tip catheter, which included radiofrequency (RF) application inside the coronary sinus (CS) from the distal to proximal portion. RF application time inside the CS was 321 seconds with the power set at 25 W. Finally, external electrical cardioversion was deployed to terminate persisting atrial fibrillation. After sinus rhythm was resumed, constant pacing from left atrial appendage (LAA) was applied with cycle length of 600 ms to validate the conduction block through the LMI, as shown in Figure 1. Was the conduction block of LMI completed?

Short-long-short sequence caused by ventricular safety pacing inducing ventricular tachycardia in a patient with a dual-chamber implantable cardioverter defibrillator.

Ventricular safety pacing (VSP) is an algorithm used to prevent crosstalk inhibition and ventricular capture during the vulnerable period. We report a 78-year-old man with implantable dual-chamber defibrillator, in whom clusters of ventricular tachycardias (VTs) were provoked by the VSP. During rapid DDDR pacing, the delivery of the VSP after every other atrial-paced beat resulted in short-long-short ventricular sequences and induced VTs. An atrial-based lower rate timing, long atrioventricular pacing interval, and automatic gain control also accounted for this arrhythmogenic ventricular sequence. The VSP and the subsequent VT were eliminated by decreasing the pacing rate.

Electrocardiographic characteristics in the patients with a persistent left superior vena cava

A persistent left superior vena cava (PLSVC) is a congenital venous abnormality and is usually asymptomatic and does not cause hemodynamic disturbances. Therefore, it is difficult to identify it by routine examinations in clinical practice. This study aimed to elucidate the electrocardiographic characteristics for the prediction of a PLSVC. Twelve patients (9 males, 56.2u2009±u200918.3xa0years) who were diagnosed with a PLSVC were enrolled. The electrocardiographic parameters, including the P-wave duration, axis, and morphology of the P waves, were automatically measured and compared to 150 controls (77 males, 57.3u2009±u200914.6xa0years). There were no significant differences in the P-wave duration. Negative or positive/negative P waves in lead III predicted a PLSVC with a sensitivity of 100% and specificity of 81%. The P-wave axis in PLSVC exhibited a significant leftward deviation as compared to the controls (14.8u2009±u200921.1 vs. 54.0u2009±u200917.4°, pu2009<u20090.001). A receiver operating characteristic curve analysis of the P-wave axis for predicting a PLSVC exhibited an area under curve of 0.93 [CI 95% (0.87–0.98), pu2009<u20090.001), and identified a P-wave axis of less than 37.5° to have a 92% sensitivity and 83% specificity in predicting a PLSVC. A negative or positive/negative P-wave morphology in lead III was a useful finding for suggesting the presence of a PLSVC.