Takehiko Matsushita

Postextrasystolic transient contractile alternans in canine hearts.

SummaryWe found that postextrasystolic potentiated contractility after a spontaneous extrasystole most frequently decayed as a transient alternans over several beats in excised, cross-circulated, atrially paced canine hearts. This type of heart preparation, which we have been using consistently in mechanoenergetic studies, had normal coronary blood perfusion pressure as well as flow and mechanoenergetic performance. Spontaneous atrial and ventricular extrasystoles occurred occasionally in every heart. Arrhythmic changes in left ventricular (LV) pressure at a fixed volume reflected corresponding changes in contractility. We analyzed nearly 3,600 cases of postextrasystolic potentiation in 68 hearts; 84% decayed as transient alternans, 6% decayed exponentially, and 10% belonged to neither type. We found that a postextrasystolic compensatory pause always preceded the transient alternans after either an atrial or ventricular extrasystole at any constant atrial pacing rate (85–188 beats/min). The decay was either exponential or nonalternating when the pause did not exist after an atrial extrasystole during occasional pacing failure. Therefore, the compensatory pause after either an atrial or ventricular extrasystole seems essential for the postextrasystolic transient alternans of LV contractility in the type of canine heart preparation we have been using.

Effect of Right Ventricular Apex Pacing on the Tei Index and Brain Natriuretic Peptide in Patients with a Dual‐Chamber Pacemaker

Background: Asynchronous electrical activation induced by right ventricular apex (RVA) pacing can cause various abnormalities in left ventricular (LV) function, particularly in the context of severe LV dysfunction or structural heart disease. However, the effect of RVA pacing in patients with normal LV and right ventricular (RV) function has not been fully elucidated. The aim of this study was to characterize the effects of RVA pacing on LV and RV function by assessing isovolumic contraction time and isovolumic relaxation time divided by ejection time (Tei index) and by assessing changes in plasma brain natriuretic peptide (BNP).

Relationship between clinical outcomes and unintentional pulmonary vein isolation during substrate ablation of atrial fibrillation guided solely by complex fractionated atrial electrogram mapping

BACKGROUND Controversy exists as to whether atrial fibrillation (AF) ablation guided solely by complex fractionated atrial electrogram (CFAE) has a good outcome despite not requiring pulmonary vein isolation (PVI). OBJECTIVES The purpose of this study was to evaluate the effectiveness of AF ablation guided solely by targeting CFAE areas, and to determine whether its clinical efficacy has any relationship with unintentionally isolating the PV. METHODS We studied 100 consecutive patients (ages 59 ± 11 years; 54 with paroxysmal, 35 persistent, and 11 long-standing persistent AF), who underwent CFAE-ablation. PV potential (PVP) was recorded before and after ablation. After excluding 39 patients in whom sinus rhythm could not be maintained before ablation by internal cardioversion and/or who had a history of PVI(s), PVPs were analyzed. RESULTS AF was terminated during ablation in 98% of paroxysmal, 80% of persistent, and 55% of long-standing persistent AF patients. Nifekalant (0.3-0.6 mg/kg) was administered in 30%, 57%, and 83%, respectively. The common areas of CFAE around the PVs were anterior to the right PVs, posterior to the left PVs, and at the ridge of the left atrial appendage. Among 215 PVs in 61 patients (42 paroxysmal, 19 persistent), only 17 PVs (8%) were unintentionally isolated. The atrial potential to PVP was prolonged (>30 ms) in 13% of PVs. After at least 12 months of follow-up (23 ± 5 months), 65% of paroxysmal (11% with drug), 54% of persistent (37% with drug), and 45% of long-standing (60% with drug) AF patients were free from atrial arrhythmia after one session. CONCLUSIONS CFAE-ablation terminates AF without isolating PVs in a high percentage of patients, and yields excellent clinical outcomes.

The role of infection in the development of non-valvular atrial fibrillation: Up-regulation of Toll-like receptor 2 expression levels on monocytes

Many studies have suggested that inflammation may participate in the pathogenesis of non-valvular atrial fibrillation (AF). However, it has been unknown by exposure to what the inflammation is caused. Recently, we reported that Toll-like receptor 2 (TLR2) level on monocytes was significantly up-regulated in viral and bacterial infections, but not in non-infectious inflammatory states. Our purpose was to test the hypothesis that expression of TLR2 levels may be up-regulated in patients with non-valvular AF. A total of 48 consecutive patients with non-valvular AF who were hospitalized for catheter ablation were enrolled in this study. TLR2 levels were assayed by using flow-cytometric analysis and compared with volunteers in sinus rhythm (control group, n = 24). Additionally, C-reactive protein (CRP) and interleukin-6 (IL-6) levels were assayed, and the left atrial volume indexes (LAVI) in the non-valvular AF group were measured. The results demonstrated that TLR2 levels in the non-valvular AF group were significantly higher than in the control group (median, 4682 vs. 3866 sites/cell; P < 0.01). Moreover, non-valvular AF patients had significantly higher IL-6 levels than controls. However, there was no significant difference in CRP levels between the two groups. It was observed in 44 AF patients, in whom pulmonary vein isolation was confirmed to be successful, that the LAVI significantly diminished 1 month after ablation (median, 33.6 vs. 29.5 ml/m²; P < 0.001), but not the TLR2 and IL-6 levels. Our results implied that an infectious inflammation may participate in the pathogenesis of non-valvular AF.

Unidirectional Conduction Block at Cavotricuspid Isthmus Created by Radiofrequency Catheter Ablation in Patients With Typical Atrial Flutter

Unidirectional Block at Cavotricuspid Isthmus. Introduction: Although unidirectional conduction block at the cavotricuspid isthmus can be created by radiofrequency ablation for atrial flutter, its underlying mechanism has not been elucidated.

Limited predictive value of inducible sustained ventricular tachycardia for future occurrence of spontaneous ventricular tachycardia in patients with coronary artery disease and relatively preserved cardiac function.

To evaluate the significance of inducible sustained ventricular tachycardia (VT) in patients with coronary artery disease and relatively preserved cardiac function, 33 patients who met the following criteria were studied; documented nonsustained VT but no history of life-threatening arrhythmia, inducible sustained VT at electrophysiologic study, and implantation of a cardioverter-defibrillator. Eighteen patients developed clinical sustained VT within 2 years. By univariate analysis, left ventricular ejection fraction (EF) and the cycle length of induced VT were associated with clinical VT occurrence. By multivariate analysis, however, EF was the only independent predictor. Among 23 patients with EF <or=40%, 16 patients developed clinical sustained VT compared to 2 of 10 patients with EF >40% (P <.01). In coronary artery disease patients with relatively preserved EF, the incidence of clinical VT is considerably low even though sustained VT is inducible. Inducible VT is therefore not appropriate for risk stratification in this patient population.

Relationship between hyperglycemia and coronary vascular resistance in non-diabetic patients

BACKGROUND Hyperglycemia upon hospital admission in patients with acute myocardial infarction is associated with the no-reflow phenomenon after successful reperfusion, and increased mortality. However, the mechanism underlying this phenomenon remains unclear. Therefore, the aim of this study was to characterize coronary hemodynamics in a homogenous group of non-diabetic patients without coronary artery disease. METHODS AND RESULTS A total of 104 consecutive non-diabetic patients (mean age, 62+/-14 years) without coronary artery disease underwent Doppler flow study of the left anterior descending coronary artery. Vascular reactivity was examined by intra-coronary administration of papaverine, acetylcholine (Ach), and nitroglycerin using a Doppler guidewire. Coronary vascular resistance (CVR) was calculated as the mean arterial pressure divided by coronary blood flow (CBF). Baseline CVR was shown as CVR at control and minimal CVR was shown as CVR with papaverine administration. Fasting plasma glucose (FPG) level had a significant, positive correlation with baseline CVR and minimal CVR (r=0.24, p<0.02 and r=0.21, p<0.05, respectively). Hemoglobin A1c (HbA1c) also had a significant, positive correlation with baseline CVR and minimal CVR (r=0.31, p<0.01 and r=0.32, p<0.01, respectively). The percent change in CBF induced by Ach was inversely correlated with HbA1c but not with FPG (r=0.22, p<0.05 and r=0.06, p=0.57, respectively). By contrast, neither FPG nor HbA1c had significant correlation with coronary flow reserve to papaverine. CONCLUSION These data demonstrate that elevated glucose levels are associated with increases in baseline and minimal coronary vascular resistance. These changes may contribute to unfavorable coronary hemodynamics in non-diabetic patients without coronary heart disease.

A Technique for Diagnosis of Accessory Pathway Using the H-H and A-A Intervals of the First Entrained Cycle During Ventricular Overdrive Pacing

Although advancement of succeeding atrial activation by a ventricular extrastimulus (VES) on His refractoriness during supraventricular tachycardia (SVT) has been used as evidence of an accessory pathway (AP), the sensitivity of this method is suboptimal. This study was designed to compare the His-His (H-H) and atrial-atrial (A-A) intervals of the first entrained cycle during ventricular overdrive pacing (VOD) for the diagnosis of AP, in comparison to the conventional VES method. In 55 patients with SVT, a VES was elicited on His refractoriness during SVT. VOD was subsequently performed at cycle lengths 30 to 40 ms shorter than SVT cycle lengths. When the A-A interval became equal to the pacing cycle length after some beats of VOD, the cycle was considered the first entrained cycle and the H-H interval preceding the A-A interval was measured. VES advanced the next atrial activation in 16 patients (52%) with an AP, but in no patient without an AP. The H-H interval of the first entrained cycle was longer than the pacing cycle length by > or =15 ms in all patients with an AP, but was equal to the pacing cycle length in all patients without an AP. The criterion of H-H greater than A-A by > or =15 ms for the first entrained cycle provided higher diagnostic yield for AP compared with the VES method(100% vs 52%, p <0.001). In conclusion, this new criterion reliably diagnoses the presence of an AP in patients with SVT, with higher sensitivity compared with the VES method.

Define the mechanism of the tachycardia and explain the results of para-Hisian pacing.

A 71-year-old man presented to the emergency room with palpitations. ECG showed a narrow QRS complex tachycardia at a rate of 180/min. The prior history and physical examination were unremarkable, and stress echocardiographic study was normal. During sinus rhythm, AH and HV intervals were 108 and 53 ms, respectively. Programmed atrial stimulation revealed anterograde dual AV nodal physiology. No tachycardia was induced with up to two atrial extrastimuli. During programmed ventricular stimulation, decremental VA conduction was observed with the earliest atrial activation site at the His-bundle recording site. A narrow QRS tachycardia with earliest atrial activation at the His recording site was reproducibly induced by both ventricular overdrive pacing

Importance of Using Standard Rather Than Torso Surface Electrocardiographic Leads for Pacemapping at the Right Ventricular Outflow Tract

MATSUSHITA, T., et al.: Importance of Using Standard Rather Than Torso Surface Electrocardiographic Leads for Pacemapping at the Right Ventricular Outflow Tract. Although pacemapping has been used to localize the origin of ventricular tachycardia, the effect of changes in the position of ECG electrodes during ventricular pacing remains unknown. To clarify the relationship between the position of ECG limb electrodes and QRS configuration during pacemapping at the right ventricular outflow tract (RVOT), RVOT pacing was performed on 12 patients at eight pacing sites located in the anterior, septal, lateral, and posterior portions each in the high and low RVOT. Standard and torso ECGs were recorded simultaneously during each pacing protocol, and the QRS axis and amplitude were compared between the two ECGs. Differences between sites in the horizontal plane and in the longitudinal direction were also compared. The QRS axis on the torso ECG was significantly more rightward than that on the standard ECG at all eight pacing sites (72.1 ± 17.4 vs 64.0 ± 21.9 degrees). The magnitude of differences in the QRS axis and amplitude between the anterior and other sites at the same height was significantly greater in the standard ECG in all locations and in 7 of 18 comparable leads, respectively. The magnitude of differences between high and low sites was significantly greater in the standard ECG in three of four locations and in 5 of 12 comparable leads, respectively. In conclusion, the torso ECG is less sensitive to changes in pacing site at the RVOT than the standard ECG. The torso ECG is, therefore, not proper for pacemapping in attempts to ablate ventricular tachycardia arising from the RVOT.