Akira Fujii

Transition from compensated hypertrophy to intrinsic myocardial dysfunction during development of left ventricular pressure-overload hypertrophy in conscious sheep. Systolic dysfunction precedes diastolic dysfunction.

BackgroundPatients with aortic stenosis have a period of compensated left ventricular hypertrophy but may eventually develop congestive heart failure. Previous experimental studies showed either normal myocardial contractility in mild short-term pressure overload or myocardial dysfunction with severe pressure overload. Transition from compensated left ventricular hypertrophy to myocardial dysfunction has not been experimentally demonstrated in an adult large animal. Controversial issues in pressureoverload hypertrophy include whether the left ventricular dysfunction is due to insufficient hypertrophy (afterload mismatch) or to intrinsic myocardial dysfunction and whether diastolic dysfunction precedes systolic dysfunction. Methods and ResultsWe induced left ventricular hypertrophy (41% increase in left ventricular to body weight ratio) by gradually tightening a hydraulic constrictor around the ascending aorta in 9 chronically instrumented conscious sheep. Afterload (end-systolic stress) elevation remained constant (approximately 33% greater than baseline) by adjustment of the aortic constrictor over 6 weeks, gradually increasing left ventricular pressure (from 117±6 to 163±5 mm Hg) as hypertrophy developed. Four sets (baseline, 2 weeks, 4 weeks, and 6 weeks) of serial hemodynamic studies were performed in each animal with ≪8-blockade, first with and then without aortic constriction to mechanically match loading conditions. Stepwise methoxamine infusion was performed to obtain load-independent assessment of myocardial contractility. Midwall shortening (P<.05) and shortening rate (P<.05) at mechanically matched loading conditions showed that myocardial dysfunction developed between the fourth and the sixth week. Shortening-preload-afterload (P<.05) and shortening rate-preload-afterload (P<.05) relations, loadindependent contractility indices based on the systolic myocardial stiffness concept, also revealed depressed myocardial contractility at the sixth week. Time constant of left ventricular isovolumic relaxation and diastolic myocardial stiffness constant did not change over the 6 weeks. ConclusionsTransition from normal myocardial contractility to myocardial dysfunction was demonstrated. This transition occurred even when the elevation of afterload remained constant as hypertrophy incompletely adapted to increasing left ventricular pressure. Systolic dysfunction preceded diastolic dysfunction in this model.

Electrophysiological Characteristics of Localized Reentrant Atrial Tachycardia Occurring After Catheter Ablation of Long‐Lasting Persistent Atrial Fibrillation

Background: Mapping of recurrent atrial tachycardia (AT) after extensive ablation for long‐lasting persistent atrial fibrillation (AF) is complex. We sought to describe the electrophysiological characteristics of localized reentry occurring after ablation of long‐lasting persistent AF.

Long-term outcomes after catheter ablation of ventricular tachycardia in patients with and without structural heart disease ☆

BACKGROUNDnLong-term outcomes after ventricular tachycardia (VT) ablation are sparsely described.nnnOBJECTIVESnThe purpose of this study was to describe long-term prognosis after VT ablation in patients with no structural heart disease (no SHD), ischemic cardiomyopathy (ICM), and nonischemic cardiomyopathy (NICM).nnnMETHODSnConsecutive patients (N = 695: no SHD, 98; ICM, 358; NICM, 239) ablated for sustained VT were followed for a median of 6 years. Acute procedural parameters (complete success [noninducibility of any VT]) and outcomes after multiple procedures were reported.nnnRESULTSnCompared with patients with no SHD or NICM, patients with ICM were the oldest, were more likely to be men, lowest left ventricular ejection fraction, highest drug failures, VT storms, and number of inducible VTs. Complete procedure success was highest in patients with no SHD than in patients with ICM and those with NICM (79%, 56%, 60%, respectively; P < .001). At 6 years, ventricular arrhythmia (VA)-free survival was highest in patients with no SHD (77%) than in patients with ICM (54%) and those with NICM (38%) (P < .001), and overall survival was lowest in patients with ICM (48%), followed by patients with NICM (74%) and patients with no SHD (100%) (P < .001). Age, left ventricular ejection fraction, presence of SHD, acute procedural success (noninducibility of any VT), major complications, need for nonradiofrequency ablation modalities, and VA recurrence were independently associated with all-cause mortality.nnnCONCLUSIONnLong-term follow-up after VT ablation shows excellent prognosis in the absence of SHD, highest VA recurrence, and transplantation in patients with NICM and highest mortality in patients with ICM. The extremely low mortality for those without SHD suggests that VT in this population is rarely an initial presentation of a myopathic process.

Substrate-Based Ablation Versus Ablation Guided by Activation and Entrainment Mapping for Ventricular Tachycardia: A Systematic Review and Meta-Analysis.

Substrate‐based ablation for scar‐related ventricular tachycardia (VT) has gained prominence: however, there is limited data comparing it to ablation guided predominantly by activation and entrainment mapping of inducible and hemodynamically tolerated VTs. We compared the acute procedural efficacy and outcomes of predominantly substrate‐based ablation versus ablation guided predominantly by activation and entrainment mapping.

Beyond the Storm: Comparison of Clinical Factors, Arrhythmogenic Substrate, and Catheter Ablation Outcomes in Structural Heart Disease Patients With versus Those Without a History of Ventricular Tachycardia Storm

Catheter ablation can be lifesaving in ventricular tachycardia (VT) storm, but the underlying substrate in patients with storm is not well characterized. We sought to compare the clinical factors, substrate, and outcomes differences in patients with sustained monomorphic VT who present for catheter ablation with VT storm versus those with a nonstorm presentation.

Impact of Lowering Irrigation Flow Rate on Atrial Lesion Formation in Thin Atrial Tissue: Preliminary Observations From Experimental and Clinical Studies

OBJECTIVESnThe authors sought to investigate the effect of low irrigation flow rate on lesion characteristics and ablation outcomes in a clinicopathological study.nnnBACKGROUNDnIrrigated ablation produces deeper lesions compared with nonirrigated ablation, which may not be desirable in the thin-walled posterior left atrium (LA), where collateral esophageal injury is possible.nnnMETHODSnLesions were placed on the smooth posterior right atrium in 20 swine and posterior LA in 60 patients at a maximum power of 20 to 25 W with either: 1) power-controlled ablation at an irrigation flow rate of 17 ml/min (high-flow group 10 swine; n = 40) or 2) temperature-controlled ablation at an irrigation flow rate of 2 ml/min (low-flow groupxa010 swine; n = 20). Safety and efficacy was also compared in 326 patients undergoing AF ablation using high-flow (nxa0= 160) or low-flow settings (nxa0= 166) for posterior LA ablation.nnnRESULTSnLow-flow, compared with high-flow, lesions in swine had a higher incidence of lesions with: impedance fallxa0≥10 Ω, loss of pace capture, electrograms characteristic of transmural lesions, and visible lesions on anatomic inspection (pxa0< 0.05 for all). Low-flow lesions had a maximal diameter at the endocardial surface, whereas high-flow lesions had a maximal diameter at the epicardial surface. In humans, impedance, pace capture, and transmurality dataxa0also strongly favored low-flow lesions. There was no difference in acute pulmonary vein isolation, complications, orxa012-month arrhythmia-free survival between the groups.nnnCONCLUSIONSnLow-flow irrigated ablation provides favorable lesion characteristics for posterior LA ablation withoutxa0increasing the risk of adverse events.

Significance of Inducible Nonsustained Ventricular Tachycardias After Catheter Ablation for Ventricular Tachycardia in Ischemic Cardiomyopathy

Background Noninducibility of sustained monomorphic ventricular tachycardia (SMVT) postablation does not insure absence of later recurrence in patients with ischemic cardiomyopathy. This study aims to determine the relation between inducible nonsustained VT postablation and VT recurrences. Methods and Results One hundred sixty-five consecutive patients (156 male; age 68±9 years) underwent ablation for SMVT because of ischemic cardiomyopathy; 44 patients who did not have induction testing or in whom only ventricular fibrillation was induced after ablation were excluded. In 38 patients (23%), SMVT was inducible (group C). Of the 83 patients without inducible SMVT after ablation, nonsustained VT defined as ≥5 beats lasting for <30 s, was induced in 34 patients (group B, 21%), whereas the remaining 49 patients had no VT induced by the induction test (group A, 30%). Over a median follow-up of 18.7 months, freedom from recurrent VT at 24 months was 60% in group A, 45% in group B (P=0.017 versus group A), and 38% in group C (P=0.005 versus group A). In patients without inducible SMVT, inducible nonsustained VT and left ventricular ejection fraction was independently associated with VT recurrence (hazard ratio, 3.66 and 1.07; 95% CI, 1.3–11.1 and 1.01–1.14). Conclusions Inducible nonsustained VT postablation suggests the continued presence of functional arrhythmia substrate. Further trials are needed to assess whether additional ablation would improve outcome in this group.

Prognostic Impact of the Timing of Recurrence of Infarct-Related Ventricular Tachycardia after Catheter Ablation

Background—Recurrence of ventricular tachycardia (VT) after ablation in patients with previous myocardial infarction is associated with adverse prognosis. However, the impact of the timing of VT recurrence on outcomes is unclear. Methods and Results—We analyzed data from a multicenter collaborative database of patients who underwent catheter ablation for infarct-related VT. Multivariable Cox regression analyses investigated the effect of the timing of VT recurrence on the composite outcome of death or heart transplantation using VT recurrence as a time-varying covariate. A total of 1412 patients were included (92% men; age: 66.7±10.7 years), and 605 patients (42.8%) had a recurrence after median 116 days (188 [31.1%] within 1 month, 239 [39.5%] between 1 and 12 months, and 178 [29.4%] after 12 months). At median follow-up of 670 days, 375 patients (26.6%) experienced death or heart transplantation. The median time from recurrence to death or heart transplantation was 65 and 198.5 days in patients with recurrence ⩽30 days and >30 days post ablation, respectively. The adjusted hazard ratio (95% confidence interval) for the effect of VT recurrence occurring immediately post ablation on death or heart transplantation was 3.45 (2.33–5.11) in reference to no recurrence. However, the magnitude of this effect decreased statistically significantly (P<0.001) as recurrence occurred later in the follow-up period. The respective risk estimates for VT recurrence at 30 days, 6 months, 1 year, and 2 years were 3.36 (2.29–4.93), 2.94 (2.09–4.14), 2.50 (1.85–3.37), and 1.81 (1.37–2.40). Conclusions—VT recurrence post ablation is associated with a mortality risk that is highest soon after the ablation and decreases gradually thereafter.

Catheter Ablation of Atypical Atrioventricular Nodal Reentrant Tachycardia.

Background: Because of its low prevalence, data on atypical atrioventricular nodal reentrant tachycardia (AVNRT) are scarce, and the optimal ablation method has not been established. Our study aimed at assessing the efficacy and safety of conventional slow pathway ablation, as applied for typical cases, in atypical AVNRT. Methods: We studied 2079 patients with AVNRT subjected to slow pathway ablation. In 113 patients, mean age 48.5±18.1 years, 68 female, atypical AVNRT or coexistent atypical and typical AVNRT without other concomitant arrhythmia was diagnosed. Ablation data and outcomes were compared with a group of age- and sex-matched control patients with typical AVNRT. Results: Fluoroscopy and radiofrequency current delivery times were not different in the atypical and typical groups, 20.3±12.2 versus 20.8±12.9 minutes (P=0.730) and 5.9±5.0 versus 5.5±4.5 minutes (P=0.650), respectively. Slow pathway ablation was accomplished from the right septum in 110 patients, and from the left septum in 3 patients, in the atypical group. There was no need for additional ablation lesions at other anatomic sites, and no cases of atrioventricular block were encountered. Recurrence rates of the arrhythmia were 5.6% in the atypical (6/108 patients) and 1.8% in the typical (2/111 patients) groups in the next 3 months following ablation (P=0.167). Conclusions: Conventional ablation at the anatomic area of the slow pathway is the therapy of choice for symptomatic AVNRT, regardless of whether the typical or atypical form is present.

Right ventricular scar-related ventricular tachycardia in nonischemic cardiomyopathy: Electrophysiological characteristics, mapping, and ablation of underlying heart disease

Right ventricular (RV)‐scar related ventricular tachycardia (VT) is often due to arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) or cardiac sarcoidosis (CS), but some patients whose clinical course has not been described do not fulfill diagnostic criteria for these diseases. We sought to characterize the electrophysiologic substrate and catheter ablation outcomes of such patients, termed RV cardiomyopathy of unknown source (RCUS).