Cardiac Resynchronization Therapy for Improving Non-Uniform Thickening of Left Ventricular Wall: Assessment by Quantitative Gated Myocardial Perfusion SPECT.

Cardiac resynchronization therapy (CRT) improves cardiac dyssynchrony in heart failure patients with a wide QRS electrocardiogram (ECG). Assessment of left ventricular (LV) dyssynchrony using echocardiography or other imaging modalities is important to predict CRT effectiveness. In this study, we retrospectively evaluated cardiac nuclear imaging of ECG-gated myocardial perfusion single-photon emission computed tomography (SPECT) with Tc-sestamibi for CRT candidate (n = 120) with severe heart failure and wide QRS (> 120 msec) in ECG.

Different characteristics of postoperative atrial tachyarrhythmias between congenital and non-congenital heart disease.

Purpose: The chance of encountering tachyarrhythmias has been increasing in adult congenital heart disease (CHD) patients with previous open-heart surgery, along with the improvement of their longevity. However, the characteristics of these arrhythmias remain to be elucidated.

Methods: We examined the characteristics of atrial tachyarrhythmias (ATs) in 26 consecutive CHD patients (M/F 17/9) referred for catheter ablation and compared them with 16 non-CHD patients with cardiac surgery (M/F 11/5).

Characteristics of ventricular tachycardia and long-term treatment outcome in patients with dilated cardiomyopathy complicated by lamin A/C gene mutations.

Background: Dilated cardiomyopathy caused by lamin A/C gene (LMNA) mutation is complicated with atrioventricular (AV) conduction disturbances, malignant ventricular arrhythmias, and progressive severe heart failure. Radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) has been reported to be challenging due to the high recurrence rate in patients with LMNA-related cardiomyopathy. However, electrophysiological and histopathological characteristics of VT substrate remain to be fully elucidated.

Development of a novel shock wave catheter ablation system--the first feasibility study in pigs.

Introduction: Radio-frequency catheter ablation (RFCA) using Joule heat has two fundamental weaknesses: the limited depth of treatment and the risk of thrombus formation. In contrast, focused shock wave (SW) therapy could damage tissues at arbitrary depths without heat generation. Thus, we aimed to develop a SW catheter ablation (SWCA) system that could compensate for the weaknesses of RFCA therapy.

Rho-kinase activation in patients with heart failure.

Background: Heart failure (HF) is a complex clinical syndrome, resulting from structural and/or functional cardiac disease. The aim of this study was to determine whether the activity of Rho-kinase, which has been identified as an important therapeutic target of cardiovascular disease, is enhanced in HF patients.

Methods And Results: Total and phosphorylated forms of myosin binding subunit (t-MBS and p-MBS), a substrate of Rho-kinase, were measured on western blotting in circulating leukocytes, and the p-MBS/t-MBS ratio was defined as an index of systemic Rho-kinase activity.

Usefulness of the noncontact mapping system to elucidate the conduction property for the treatment of common atrial flutter.

Background: The functional role of the cavotricuspid isthmus (CTI) for common atrial flutter (cAFL) remains to be elucidated. In the present study, we examined whether the EnSite system (St. Jude Medical, St.

Delayed enhancement on cardiac magnetic resonance imaging is a poor prognostic factor in patients with cardiac sarcoidosis.

Background: Predictors of ventricular arrhythmias (VA) in patients with cardiac sarcoidosis (CS) remain unclear.

Methods And Results: We examined 61 consecutive CS patients who were admitted to our hospital from April 2002 to March 2012 with a mean follow-up period of 45 ± 31 months for the relationship between delayed enhancement on cardiac magnetic resonance imaging (DE-MRI) and VA or a composite endpoint, including VA, heart failure hospitalization, and cardiovascular mortality. Although there was no significant difference in baseline clinical characteristics between patients with VA and those without it, the former group was characterized as compared with the latter by lower left ventricular (LV) ejection fraction (p<0.

Increased incidence of tachyarrhythmias and heart failure hospitalization in patients with implanted cardiac devices after the great East Japan earthquake disaster.

Background: After the East Japan Earthquake disaster there may have been a deterioration of patients with cardiovascular diseases.

Methods And Results: We examined the data from 189 consecutive patients implanted with cardiovascular devices for the 6-month period before and after the Earthquake. In 170 patients with defibrillators, the number who experienced tachyarrhythmias increased significantly after the Earthquake (28 ± 5 vs.

A sodium channel blocker, pilsicainide, produces atrial post-repolarization refractoriness through the reduction of sodium channel availability.

Atrial fibrillation (AF) is the most common tachyarrhythmia. Shortening of atrial action potential duration (APD) and effective refractory period (ERP) is one of the crucial factors in the occurrence and maintenance of AF. ERP is usually shorter than APD, but ERP can be prolonged beyond action potential repolarization in some situations.

Acceleration of Ca2+ waves in monocrotaline-induced right ventricular hypertrophy in the rat.

Background: Triggered arrhythmias arise from delayed afterdepolarizations (DADs), with Ca(2+) waves playing an important role in their formation. In ventricular hypertrophy, however, it remains unclear how Ca(2+) waves change their propagation features and affect arrhythmogenesis. We addressed this important issue in a rat model of hypertrophy.

The role of echocardiography in predicting responders to cardiac resynchronization therapy.

Background: This multicenter prospective cohort study aimed to identify both ability of echocardiographic parameters to detect cardiac resynchronization therapy (CRT) volume responders and relation of these parameters with clinical outcomes.

Methods And Results: CRT responder was defined as ≥ 15% reduction of left ventricular (LV) end-systolic volume at 6 months. Seven echocardiographic dyssynchrony parameters were evaluated.

Contribution of Na+/Ca2+ exchange current to the formation of delayed afterdepolarizations in intact rat ventricular muscle.

Aim: To evaluate the role of the Na+-Ca2+ exchange current in the induction of arrhythmias during Ca2+ waves, we investigated the relationship between Ca2+ waves and delayed afterdepolarizations (DADs) and further investigated the effect of KB-R7943, an Na+-Ca2+ exchange inhibitor, on such relationship in multicellular muscle.

Methods: Force, sarcomere length, membrane potential, and [Ca2+]i dynamics were measured in 32 ventricular trabeculae from rat hearts. After the induction of Ca2+ waves by trains of electrical stimuli (400, 500, or 600 ms intervals) for 7.

Importance of dual induction tests for coronary vasospasm and ventricular fibrillation in patients surviving out-of-hospital cardiac arrest.

Background: The pathogenesis of out-of-hospital cardiac arrest (OHCA) without organic heart disease has not been fully investigated.

Methods And Results: Induction tests were performed in 12 consecutive patients with OHCA for both coronary vasospasm with intracoronary acetylcholine and ventricular fibrillation (VF) with programmed stimulation at 1 month after the event. All patients were positive for 1 of the tests: coronary vasospasm alone in 3, VF alone in 2, and both in 7.

Spatial non-uniformity of excitation-contraction coupling can enhance arrhythmogenic-delayed afterdepolarizations in rat cardiac muscle.

Aims: We examined whether non-uniform muscle contraction affects delayed afterdepolarizations (DADs) by dissociating Ca(2+) from myofilaments within the border zone (BZ) between contracting and stretched regions.

Methods And Results: Force, sarcomere length (SL), membrane potential, and [Ca(2+)](i) dynamics were measured in 31 ventricular trabeculae from rat hearts. Non-uniform muscle contraction was produced by exposing a restricted region of muscle to a jet of solution containing 20 mmol/L 2,3-butanedione monoxime (BDM).

Electrophysiological properties of the right atrial septum in patients with atrial tachyarrhythmias.

Common-type atrial flutter (AFL) is a type of atrial tachyarrhythmia with counterclockwise rotation around the tricuspid annulus within the right atrium (RA). It was recently reported that the electrogram voltage reduction observed in the RA was involved in the development of AFL. However, the relationship between the low voltage areas and conduction velocity during AFL has not been fully described.

Sarcomere mechanics in uniform and non-uniform cardiac muscle: a link between pump function and arrhythmias.

Starling's Law and the well-known end-systolic pressure-volume relationship (ESPVR) of the left ventricle reflect the effect of sarcomere length (SL) on stress (sigma) development and shortening by myocytes in the uniform ventricle. We show here that tetanic contractions of rat cardiac trabeculae exhibit a sigma-SL relationship at saturating [Ca2+] that depends on sarcomere geometry in a manner similar to skeletal sarcomeres and the existence of opposing forces in cardiac muscle shortened below slack length. The sigma-SL-[Ca2+]free relationships (sigma-SL-CaR) at submaximal [Ca2+] in intact and skinned trabeculae were similar, albeit that the sensitivity for Ca2+ of intact muscle was higher.

Sarcomere mechanics in uniform and nonuniform cardiac muscle: a link between pump function and arrhythmias.

Starling's law and the end-systolic pressure-volume relationship (ESPVR) reflect the effect of sarcomere length (SL) on the development of stress (sigma) and shortening by myocytes in the uniform ventricle. We show here that tetanic contractions of rat cardiac trabeculae exhibit a sigma-SL relationship at saturating [Ca2+] that depends on sarcomere geometry in a manner similar to that of skeletal sarcomeres and the existence of opposing forces in cardiac muscle shortened below slack length. The sigma-SL -[Ca2+](free) relationships (sigma-SL-Ca relationships) at submaximal [Ca2+] in intact and skinned trabeculae were similar, although the sensitivity for Ca2+ of intact muscle was higher.

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.

Methods And Results: Based on the mapping site and successful ablation in 45 consecutive patients with LVOT-VTs, we classified them into VTs of AMC (n = 3), MA (n = 8), ASC (n = 32), and epicardial (n = 2) origins.

High-density materials do not always induce artifacts on PET/CT: what is responsible for the difference?

Objective: PET/CT often show increased uptake at sites of high-density materials. However, some materials seldom demonstrate increased uptake on PET/CT, such as the materials used in hip prostheses. We hypothesized that the motion of materials may be crucial for such artifacts.

Role of sarcomere mechanics and Ca2+ overload in Ca2+ waves and arrhythmias in rat cardiac muscle.

Ca(2+) release from the sarcoplasmic reticulum (SR) depends on the sarcoplasmic reticulum (SR) Ca(2+) load and the cytosolic Ca(2+) level. Arrhythmogenic Ca(2+) waves underlying triggered propagated contractions arise from Ca(2+) overloaded regions near damaged areas in the cardiac muscle. Ca(2+) waves can also be induced in undamaged muscle, in regions with nonuniform excitation-contraction (EC) coupling by the cycle of stretch and release in the border zone between the damaged and intact regions.

Reduced inotropic effect of nifekalant in failing hearts in rats.

Class III antiarrhythmic agents have been widely used to suppress ventricular tachyarrhythmias in patients with heart failure because they have been shown to have positive inotropic effects as well. However, it remains to be examined whether those agents also exert positive inotropic effects in failing hearts. We addressed this important issue in a rat model of heart failure.

Arrhythmogenic Ca(2+) release from cardiac myofilaments.

We investigated the initiation of Ca(2+)waves underlying triggered propagated contractions (TPCs) occurring in rat cardiac trabeculae under conditions that simulate the functional non-uniformity caused by mechanical or ischemic local damage of the myocardium. A mechanical discontinuity along the trabeculae was created by exposing the preparation to a small constant flow jet of solution with a composition that reduces excitation-contraction coupling in myocytes within that segment. Force was measured and sarcomere length as well as [Ca(2+)](i) were measured regionally.

Spatial nonuniformity of contraction causes arrhythmogenic Ca2+ waves in rat cardiac muscle.

Landesberg and Sideman's four state model of the cardiac cross-bridge (XB) hypothesizes a feedback of force development to Ca(2+) binding by troponin C (TnC). We have further modeled this behavior and observed that the force (F)-Ca(2+) relationship as well as the F-sarcomere length (SL) relationship and the time course of F and Ca(2+) transients in cardiac muscle can be reproduced faithfully by a single effect of F on deformation of the TnC-Ca complex and, thereby, on the dissociation rate of Ca(2+). Furthermore, this feedback predicts that rapid decline of F in the activated sarcomere causes release of Ca(2+) from TnC-Ca(2+), which is sufficient to initiate arrhythmogenic Ca(2+) release from the sarcoplasmic reticulum (SR).

Spatial nonuniformity of excitation-contraction coupling causes arrhythmogenic Ca2+ waves in rat cardiac muscle.

Ca2+ waves underlying triggered propagated contractions (TPCs) are initiated in damaged regions in cardiac muscle and cause arrhythmias. We studied Ca2+ waves underlying TPCs in rat cardiac trabeculae under experimental conditions that simulate the functional nonuniformity caused by local mechanical or ischemic local damage of myocardium. A mechanical discontinuity along the trabeculae was created by exposing the preparation to a small jet of solution with a composition that reduces excitation-contraction coupling (ECC) in myocytes within that segment.