Ventilatory and behavioural responses of the marbled sole Pseudopleuronectes yokohamae to progressive hypoxia.

This study identified ventilatory and behavioural responses in the marbled sole Pseudopleuronectes yokohamae under experimentally induced progressive decreases in dissolved oxygen (DO) levels. Ventilation frequency showed an increase with decreasing DO levels from normoxia to 2·75 mg O2 l-1 , followed by a decrease in ventilation frequency at decreased DO levels from 2·00 to 0·75 mg O2 l-1 . At DO levels below 2·00 mg l-1 , behaviours at the bottom were suppressed, whereas avoidance behaviours increased. A decrease in avoidance behaviours was observed from 1·00 to 0·75 mg O2 l-1 . Upside-down reversal and incapacitation at DO levels of 1·00-0·75 mg O2 l-1 suggested that sublethal effects on P. yokohamae were induced. The responses observed before the sublethal DO level could be interpreted as an effort to maintain oxygen uptake, reduce routine activities and facilitate avoidance. The observed DO level thresholds that induce behavioural responses, in addition to sublethal effects, indicate hypoxia-tolerance that is important for understanding the effects of hypoxia on coastal ecosystems.

Spin-chirality-driven ferroelectricity on a perfect triangular lattice antiferromagnet.

Magnetic field (B) variation of the electrical polarization P(c) (∥c) of the perfect triangular lattice antiferromagnet RbFe(MoO(4))(2) is examined up to the saturation point of the magnetization for B⊥c. P(c) is observed only in phases for which chirality is predicted in the in-plane magnetic structures. No strong anomaly is observed in P(c) at the field at which the spin modulation along the c axis, and hence the spin helicity, exhibits a discontinuity to the commensurate state. These results indicate that the ferroelectricity in this compound originates predominantly from the spin chirality, the explanation of which would require a new mechanism for magnetoferroelectricity. The obtained field-temperature phase diagram of ferroelectricity agree well with those theoretically predicted for the spin chirality of a Heisenberg spin triangular lattice antiferromagnet.

B-type natriuretic peptide levels are decreased by reducing dietary salt intake in patients with compensated heart failure with preserved ejection fraction.

BACKGROUND: Dietary salt restriction is believed to be a mainstay in the management of patients with heart failure. However, the effect of salt intake on heart failure has not been well evaluated in outpatient medical practice. AIMS: The aim of the present study was to assess the hypothesis that B-type natriuretic peptide (BNP) level, as an objective marker of heart failure, is associated with salt intake in patients with heart failure. METHODS: One hundred and thirteen consecutive patients with mild compensated heart failure (77 ± 10 years old, 51 female) were included. We estimated dietary salt intake by the concentration of sodium and creatinine in spot urine. We measured BNP at the time of urine sampling and assessed the relationship between the % changes in BNP levels (%ΔBNP) and the changes in the estimated daily salt excretion (ΔNaCl) during the follow-up period. RESULTS: The baseline median BNP level was 150 (interquartile range: 83-263) pg/mL and the estimated daily salt excretion was 162 ± 45 mmol/day. There was a positive correlation between %ΔBNP and ΔNaCl (r = 0.61, P < 0.01). Multiple regression analysis revealed that %ΔBNP was associated with ΔNaCl (P < 0.01), but not with changes in systolic blood pressure and bodyweight. CONCLUSIONS: Changes in BNP levels were associated with changes in the estimated daily salt excretion in outpatients with compensated heart failure. Salt restriction may be beneficial for the management of patients with heart failure.

105Pd NMR and NQR study of the cubic heavy fermion system Ce3Pd20Si6.

We report 105Pd nuclear magnetic resonance (NMR) and nuclear quadrupolar resonance (NQR) measurements on a single crystal of Ce3Pd20Si6, where antiferroquadrupolar and antiferromagnetic orders develop at low temperature. From the analysis of NQR and NMR spectra, we have determined the electric field gradient (EFG) tensors and the anisotropic Knight shift (K) components for both inequivalent Pd sites-Pd(32f) and Pd(48h). The observed EFG values are in excellent agreement with our state-of-the-art density functional theory calculations. The principal values of the quadrupolar coupling are [Formula: see text] MHz and [Formula: see text] MHz, for the Pd(32f) and Pd(48h) sites, respectively, which is large compared to the Larmor frequency defined by the gyromagnetic constant [Formula: see text] MHz/T for 105Pd. Therefore, the complete knowledge of K and the EFG tensors is crucial to establish the correspondence between NMR spectra and crystallographic sites, which is needed for a complete analysis of the magnetic structure, static spin susceptibility, and the spin-lattice relaxation rate data and a better understanding of the groundstate of Ce3Pd20Si6.

Topological transitions among skyrmion- and hedgehog-lattice states in cubic chiral magnets.

Manipulating topological spin textures is a key for exploring unprecedented emergent electromagnetic phenomena. Whereas switching control of magnetic skyrmions, e.g., the transitions between a skyrmion-lattice phase and conventional magnetic orders, is intensively studied towards development of future memory device concepts, transitions among spin textures with different topological orders remain largely unexplored. Here we develop a series of chiral magnets MnSi1-xGex, serving as a platform for transitions among skyrmion- and hedgehog-lattice states. By neutron scattering, Lorentz transmission electron microscopy and high-field transport measurements, we observe three different topological spin textures with variation of the lattice constant controlled by Si/Ge substitution: two-dimensional skyrmion lattice in x = 0-0.25 and two distinct three-dimensional hedgehog lattices in x = 0.3-0.6 and x = 0.7-1. The emergence of various topological spin states in the chemical-pressure-controlled materials suggests a new route for direct manipulation of the spin-texture topology by facile mechanical methods.

Large magneto-thermopower in MnGe with topological spin texture.

Quantum states characterized by nontrivial topology produce interesting electrodynamics and versatile electronic functionalities. One source for such remarkable phenomena is emergent electromagnetic field, which is the outcome of interplay between topological spin structures with scalar spin chirality and conduction electrons. However, it has scarcely been exploited for emergent function related to heat-electricity conversion. Here we report an unusually enhanced thermopower by application of magnetic field in MnGe hosting topological spin textures. By considering all conceivable origins through quantitative investigations of electronic structures and properties, a possible origin of large magneto-thermopower is assigned to the strong energy dependence of charge-transport lifetime caused by unconventional carrier scattering via the dynamics of emergent magnetic field. Furthermore, high-magnetic-field measurements corroborate the presence of residual magnetic fluctuations even in the nominally ferromagnetic region, leading to a subsisting behavior of field-enhanced thermopower. The present finding may pave a way for thermoelectric function of topological magnets.

Assessment of reverse use-dependent blocking actions of class III antiarrhythmic drugs by 24-hour Holter electrocardiography.

OBJECTIVES: This clinical study was designed to compare rate-dependent effects of class III agents on QT prolongation. BACKGROUND: Clinical data that compare the electrophysiologic differences among class III agents with different selectivity for potassium channels are still lacking. METHODS: QT intervals were measured over a wide range of preceding RR intervals during sinus rhythm by 24-h Holter electrocardiography before and after oral administration of four class III agents: E4031, dofetilide, MS551 and d-sotalol. Rate-dependent changes in the QT interval were assessed by the slope of the linear regression line estimating the QT-square root of RR relation. RESULTS: All agents significantly increased the mean slope: E4031 increased the mean [+/- SD] value from 0.32 +/- 0.05 to 0.42 +/- 0.13 (p < 0.01), dofetilide from 0.32 +/- 0.03 to 0.50 +/- 0.12 (p < 0.03), MS551 from 0.35 +/- 0.06 to 0.45 +/- 0.10 (p < 0.02) and d-sotalol from 0.31 +/- 0.05 to 0.33 +/- 0.04 (p < 0.05). However, in those patients given either E4031, dofetilide or MS551, the degree of QT prolongation was smaller at shorter square root of RR intervals and was better preserved at shorter square root of RR intervals by d-sotalol, with a smaller increase in slope (p < 0.02 vs. dofetilide and MS551). CONCLUSIONS: On ambulatory electrocardiography, reverse use dependence in QT prolongation was least prominent with d-sotalol among the four study drugs. In the range of physiologic heart rates, class III agents could manifest different profiles of rate dependence in their QT-prolonging effect.

Effects of adenosine and adenosine 5'-triphosphate on ventricular escape rhythm in the canine heart.

The effects of adenosine and adenosine 5'-triphosphate (ATP) on ventricular escape rhythms were studied in 16 closed chest dogs after electroablation of the His bundle region. All dogs exhibited complete atrioventricular (AV) block and stable ventricular escape rhythm with a mean cycle length of 1,210 +/- 80 ms and a QRS width of 91 +/- 5 ms. Physiologic AV sequential pacing was operative during experiments and was interrupted for rapid (less than or equal to 1 second) administration of either adenosine or ATP (3 mumol/kg) into the right atrium. Adenosine and ATP effectively depressed ventricular escape rhythms in a similar manner both qualitatively and quantitatively (cycle length from 1,210 +/- 80 to 1,764 +/- 132 ms and from 1,274 +/- 84 to 2,000 +/- 150 ms, respectively; each p less than 0.01). These effects were not significantly altered by either physostigmine (an acetylcholinesterase inhibitor) or atropine (a muscarinic cholinergic blocker), but were slightly attenuated by propranolol (a beta-adrenoceptor blocker). In the presence of autonomic blockade, the adenosine transport blocker dipyridamole markedly enhanced the depressant effects of adenosine and ATP. The adenosine competitive antagonist aminophylline reversed the action of dipyridamole. Thus, both adenosine and ATP depress ventricular escape rhythms in vivo, independent of the autonomic nervous system. Moreover, the effects of ATP can be accounted for in large part by its rapid breakdown to adenosine.

Autonomic and antiarrhythmic drug modulation of ST segment elevation in patients with Brugada syndrome.

OBJECTIVES: We examined the modulatory effects of autonomic nervous system and antiarrhythmic drugs on the ST segment in patients with Brugada syndrome to gain an insight into the mechanism of ST segment elevation. BACKGROUND: Right bundle branch block, ST segment elevation and ventricular tachyarrhythmias define a distinct clinical and electrocardiographic (ECG) syndrome (Brugada syndrome). However, the mechanism of ST segment elevation and the causes of this syndrome are unknown. METHODS: The study included four patients in whom structural heart or coronary artery disease was excluded by noninvasive and invasive tests. High take-off ST segment elevation of either the coved or saddle-back type in precordial leads V1, V2 and V3 was seen in all patients. Three patients experienced recurrent episodes of syncope or aborted sudden cardiac death, and the remaining patient had palpitation. Autonomic receptor stimulation and blockade and intravenous administration of antiarrhythmic drugs were performed during sinus rhythm while the 12-lead ECG was recorded. Metaiodobenzylguanidine (MIBG) scanning and Holter monitoring were also performed. RESULTS: Beta-adrenoceptor stimulation by intravenous isoproterenol consistently reduced (> or = 0.1 mV) ST segment elevation at or 80 ms after the J point in all four patients. Selective alpha-adrenoceptor stimulation by intravenous norepinephrine in the presence of propranolol or by intravenous methoxamine consistently augmented, whereas alpha-adrenoceptor blockade reduced, ST segment elevation in three patients. Intracoronary acetylcholine or intravenous edrophonium or neostigmine augmented ST segment elevation without inducing coronary spasm in three of four patients. Class IA antiarrhythmic drugs also consistently augmented (three patients), whereas class IB drugs had no effect on (two patients) ST segment elevation. No abnormality was found on MIBG imaging or heart rate variability in three patients, suggesting that autonomic dysfunction is not a primary disease process. Class IA drugs had no effect on ST segment in three control patients, suggesting that the ST segment elevation seen in patients with Brugada syndrome in response to the drugs is not a nonspecific response. CONCLUSIONS: ST segment elevation in patients with Brugada syndrome was augmented by selective stimulation of alpha-adrenoceptors or muscarinic receptors or by class IA drugs but was mitigated by beta-adrenoceptor stimulation or alpha-adrenoceptor blockade. These responses might be explained by postulating the presence of an area of early repolarization or a local "depolarized" area in the ventricle causing ST segment elevation in this syndrome. Because only a small number of patients were studied, these possibilities need further evaluation.

Autoantibodies against the second extracellular loop of beta1-adrenergic receptors predict ventricular tachycardia and sudden death in patients with idiopathic dilated cardiomyopathy.

OBJECTIVES: We sought to define the clinical and long-term prognostic implications of autoantibodies that act against the second extracellular loop of beta1-adrenergic receptors (ARs) in patients with idiopathic dilated cardiomyopathy (IDC). BACKGROUND: Although autoantibodies directed against various domains of beta-ARs are found in patients with IDC, only a subgroup against the second extracellular domain of beta1-ARs exerts intrinsic sympathomimetic-like actions on human beta-ARs. It is suggested that the autoantibodies take part in the pathophysiology of IDC and may affect long-term prognosis of patients with this disorder. METHODS: Sera from 104 patients with IDC were screened for autoantibodies that act against the second extracellular loop of beta1-ARs by enzyme-linked immunosorbent assay, using a synthetic peptide corresponding to the domain. Relations of the autoantibodies to clinical variables and long-term prognosis were assessed by multivariate analysis. RESULTS: Autoantibodies were detected in 40 patients (38%). Multifocal ventricular premature contractions (p < 0.01) and ventricular tachycardia (VT; p < 0.01) were more common in autoantibody-positive than in autoantibody-negative patients, although no differences in cardiac function or neurohormonal levels were demonstrated. The presence of autoantibodies (p = 0.001) and a low left ventricular ejection fraction (LVEF <30%; p = 0.02) were independent predictors of VT. Sudden death was independently predicted by the presence of autoantibodies (p = 0.03), as well as by LVEF <30% (p = 0.01), whereas total mortality was predicted only by LVEF <30% (p = 0.001). CONCLUSIONS: Autoantibodies directed against the second extracellular loop of beta1-ARs were closely related to serious ventricular arrhythmias in patients with IDC, and the presence of autoantibodies independently predicted sudden death. These autoantibodies may contribute to electrical instability in patients with IDC.

Preinfarction angina as a major predictor of left ventricular function and long-term prognosis after a first Q wave myocardial infarction.

OBJECTIVES: The purpose of this study was to assess the prognostic significance of preinfarction angina after a first Q wave myocardial infarction. Patients with anterior or inferior myocardial infarction were compared. BACKGROUND: The effect of preinfarction angina on prognosis after anterior and inferior myocardial infarction remains unclear. METHODS: A total of 291 patients with a first Q wave anterior (n = 171) or inferior (n = 120) myocardial infarction were examined to assess the effect of preinfarction angina on short- and long-term prognosis. The relation between predischarge left ventriculographic findings and preinfarction angina was also examined. RESULTS: The presence of preinfarction angina was associated with lower peak creatine kinase activity, a lower in-hospital incidence of sustained ventricular tachycardia and fibrillation and a lower incidence of pump failure and cardiac mortality in patients with either anterior or inferior infarction. Among patients with anterior infarction, preinfarction angina was associated with a lower incidence of cardiac rupture and less need for readmission for heart failure within 1 year after the onset of infarction. In this subgroup it was also associated with a higher ejection fraction, a smaller end-diastolic volume and a lower incidence of aneurysm formation noted on ventriculography during convalescence. In patients with inferior infarction, these variables did not differ significantly in the presence or absence of preinfarction angina. Multivariate analysis confirmed that the presence of preinfarction angina was an independent predictor of development of ventricular aneurysm, late phase heart failure and 1-year cardiac mortality. CONCLUSIONS: The presence of preinfarction angina has a favorable effect on infarct expansion and late phase left ventricular function, especially in patients with anterior myocardial infarction. The mechanisms responsible for this phenomenon are not known but may be secondary to limitations of infarct size through unidentified mechanisms other than collateralization (e.g., ischemic preconditioning).

Importance of the pacing mode in the initiation of ventricular tachyarrhythmia in a canine model of chronic myocardial infarction.

The use of unipolar anodal or bipolar pacing, as compared with unipolar cathodal pacing, purportedly increases the likelihood of inducing inadvertent ventricular fibrillation in susceptible patients. In this study, the ability to initiate sustained ventricular tachycardia or fibrillation with unipolar cathodal, unipolar anodal and bipolar pacing modes was compared using programmed ventricular stimulation at 82 subendocardial periinfarction sites in 11 dogs with chronic myocardial infarction. The late diastolic excitability threshold was significantly higher and the ventricular refractory period was significantly shorter (p less than 0.001) with anodal pacing (mean 0.62 mA, 156 ms, respectively) than with pacing in either the cathodal (0.12 mA, 174 ms) or the bipolar (0.13 mA, 173 ms) mode. At a current intensity twice that of the excitability threshold, the introduction of one or two extrastimuli induced ventricular tachycardia and ventricular fibrillation comparably among the three pacing modes. However, when three extrastimuli were used, ventricular fibrillation was induced with anodal pacing twice as frequently (50 [61%] of 82 sites) as with either of the other two pacing modes (each 23 [28%] of 82 sites, p less than 0.001), whereas the induction of ventricular tachycardia remained comparable with anodal pacing (15 [18%] of 82 sites) and cathodal and bipolar pacing (each 14 [17%] of 82 sites). Furthermore, a similarly high incidence of inducibility of ventricular fibrillation was observed with both cathodal pacing (56 [68%] of 82 sites) and bipolar pacing (40 [49%] of 82 sites) when an increased current equal to twice the anodal excitability threshold (1.23 mA) was used.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of refractory periods and conduction velocity during atrial fibrillation using atrial capture in dogs: direct assessment of the wavelength and its modulation by a sodium channel blocker, pilsicainide.

OBJECTIVES: The purposes of this study were to measure the atrial refractory period and the conduction velocity (CV) during atrial fibrillation (AF) and to explore the antiarrhythmic mechanism of a sodium channel blocker, pilsicainide, during AF. BACKGROUND: Sodium channel blockers not only decrease the CV, but also prolong the atrial refractory period, particularly during rapid excitation. Because these effects on the wavelength are counteractive and rate dependent, it is critical to measure these parameters during AF. METHODS: In eight dogs, after AF was induced under vagal stimulation, a single extra-stimulus was repeatedly introduced from the left atrium and its capture was statistically determined for each coupling interval. The local CV was also measured during constant capture of the fibrillating atrium by rapid pacing. The same procedure was repeated after pilsicainide administration. RESULTS: Pilsicainide significantly increased the mode of AF intervals from 81 +/- 10 to 107 +/- 16 ms (p < 0.01). While the CV was decreased from 0.9 +/- 0.1 to 0.7 +/- 0.1 m/s (p < 0.02), the effective refractory period during AF was increased from 69 +/- 11 ms to 99 +/- 17 ms (p < 0.01). As a result, the wavelength was significantly increased by pilsicainide from 6.6 +/- 0.9 to 7.6 +/- 1.2 cm (p < 0.05). CONCLUSIONS: During AF, whereas the sodium channel blocker pilsicainide decreases CV, it lengthens the wavelength by increasing the refractory period, an action that is likely to contribute to the drug's ability to terminate the arrhythmia. The direct measurement of refractoriness and CV during AF may provide new insights into the determinations of the arrhythmia and antiarrhythmic drug action.

Extracellular potassium ion dynamics and ventricular arrhythmias in the canine heart.

The relation between extracellular potassium ion activity [( K+]o) and ventricular tachyarrhythmias was studied in an open chest canine model with the use of two protocols. In Protocol I, potassium chloride was administered into the proximal left anterior descending coronary artery at a rate of 0.125 mEq/min for either 20 min or until [K+]o = 20 mEq/liter, whichever came first. In Protocol II, the proximal left anterior descending coronary artery was occluded in one step and was reperfused 20 min later. Fifteen dogs were subjected to Protocol I, nine of which were also subjected to Protocol II. In the latter group, a recovery period of greater than or equal to 1 h separated the two protocols. Local K+ and intramyocardial activities were recorded with use of bifunctional ion-sensitive plunge electrodes at multiple sites located in the region of the left ventricle perfused by the left anterior descending artery and at one site outside of this region. The following variables were recorded and analyzed: Lead II electrocardiogram, heart rate, systemic arterial blood pressure, local [K+]o and its time derivative (dK+/dt), local electrograms and ventricular arrhythmias. Maximal [K+]o and dK+/dt were 23 +/- 3 mEq/liter and 9 +/- 1 mEq/liter per min in Protocol I and 14 +/- 1 mEq/liter and 3 +/- 1 mEq/liter per min in Protocol II, respectively. In both protocols, the occurrence of ventricular arrhythmias correlated with [K+]o (p less than 0.02) as well as with dK+/dt (p less than 0.05). Ventricular arrhythmias were more frequent and more severe in Protocol II than in Protocol I (p less than 0.05). Therefore, whereas K+ dynamics were more pronounced in Protocol I, ventricular arrhythmias were more severe in Protocol II. This occurrence was apparently due, at least in part, to less heterogeneous changes in K+ gradients during constant K+ infusion. It was concluded that, in addition to the magnitude of [K+]o, the rate of change of this variable (that is, dK+/dt) apparently plays an important role in the genesis of ischemic ventricular arrhythmias.

Evaluation of scaffolding effects of five different types of stents by intravascular ultrasound analysis.

The acute elastic recoil of 5 types of stents immediately after deployment by intravascular ultrasound and quantitative coronary angiography measurements was analyzed. Successfully implanted stents were: Palmaz-Schatz in 104 lesions, Gianturco-Roubin in 65, Wiktor in 45, gfx in 22, and Multi-Link stents in 22. Before and after stenting, the cross section of the smallest luminal area and vessel area was measured with intravascular ultrasound. The postdilatation balloon area was calculated by quantitative coronary angiography. Percent recoil was calculated as: [1-(preluminal area)/balloon area)] x 100. The ratio of balloon area-to-vessel area was also compared. Although preluminal areas in Gianturco-Roubin and Palmaz-Schatz stents were similar (2.4 +/- 0.1 vs 2.5 +/- 0.1 mm2, p = NS), postluminal area in the Gianturco-Roubin was significantly smaller than the area in the Palmaz-Schatz (6.3 +/- 0.2 vs 8.3 +/- 0.3 mm2, p <0.05). Although both the balloon area/vessel area (0.68 +/- 0.05, 0.80 +/- 0.08 vs 0.83 +/- 0.02, p <0.05) and the preluminal area (2.1 +/- 0.4, 1.6 +/- 0.2 vs 2.5 +/- 0.1 mm2, p <0.05) were smaller in gfx and Multi-Link than in the Palmaz-Schatz, postluminal area was comparable to the area in the Palmaz-Schatz (7.8 +/- 0.4, 7.4 +/- 0.4 vs 8.3 +/- 0.3 mm2, p = NS). Percent recoil in the Gianturco-Roubin was poorest among these 5 groups. More favorable initial gain can be obtained with Palmaz-Schatz, Wiktor, gfx, and Multi-Link stents than with the Gianturco-Roubin stent.

Two dimensional echocardiographic analysis of wall motion abnormalities during handgrip exercise in patients with coronary artery disease.

Studies were made of the feasibility and value of two dimensional echocardiography in detecting left ventricular asynergy during handgrip exercise in 45 patients with suspected coronary artery disease. Resting echocardiography revealed normal wall motion in 32 patients, and in 17 of these handgrip exercise induced abnormal wall motion. All 17 patients had significant stenoses in the coronary arteries. However, only 65 percent of patients with coronary artery disease whose resting two dimensional echocardiogram revealed normal wall motion showed abnormal wall motion during handgrip exercise. The left ventricular wall visualized in the short axis plane was divided into 5 segments, and a total of 225 segments were analyzed. Of 49 segments with exercise-induced asynergy, 46 (94 percent) reflected significant stenosis in the perfusing coronary artery. In particular, 16 (89 percent) of 18 segments with exercise-induced akinesia reflected stenosis of greater than 90 percent. Resting or exercise two dimensional echocardiography (or both) was able to diagnose multivessel disease with a predictability of 92 percent. It is concluded that two dimensional echocardiography combined with handgrip exercise has high specificity in detecting coronary artery disease and would be useful for predicting severely stenotic or multivessel coronary arterial lesions.

Effect on short-term prognosis and left ventricular function of angina pectoris prior to first Q-wave anterior wall acute myocardial infarction.

The prognostic significance of angina pectoris before the development of first Q-wave anterior wall acute myocardial infarction (AMI) was assessed in 153 patients. A total of 100 patients in this study had angina before Q-wave AMI, whereas 53 patients had no antecedent symptoms of angina. The presence of angina before AMI was associated with a lower incidence of complications including sustained ventricular tachycardia or fibrillation (7% vs 25%, p = 0.0022), pump failure (24% vs 47%, p = 0.0035), cardiac rupture (1% vs 17%, p = 0.0001), and a lower in-hospital mortality rate (11% vs 28%, p = 0.0067). The peak creatine phosphokinase activity was lower in patients with than without antecedent angina (1,727 +/- 1,238 vs 2,675 +/- 2,569 IU/liter, respectively, p = 0.023). There was no difference in the prevalence of multivessel coronary artery disease or the presence of collateral circulation between the 2 groups. Left ventriculography revealed a higher left ventricular ejection fraction (54 +/- 13% vs 46 +/- 11%, p = 0.034) and smaller left ventricular end-diastolic volumes (75 +/- 15 vs 86 +/- 18 ml/m2, p = 0.017) in patients with than without antecedent angina. These findings suggest that the presence of angina before AMI may be associated with a protective effect on left ventricular function during anterior wall AMI. Although the precise mechanisms underlying the beneficial effects are unknown, they may be related to the development of collateral channels or ischemic preconditioning.

Ventricular arrhythmias in heart failure.

In the management of patients with chronic heart failure, our attention is shifting from just improving left ventricular function and abolishing ventricular arrhythmias to improving personal longevity. Importantly, sudden cardiac death is a pattern of death in as many as a half of patients with chronic heart failure. Arrhythmias are common in this disorder, but may possibly be a marker of diseased heart rather than a predictor of sudden cardiac death. The mechanisms and triggers of rapid ventricular tachycardia or fibrillation responsible for sudden cardiac death have not been well established. At present, it is important to be reminded that pharmacologic augmentation of cardiac contractility or suppression of asymptomatic ventricular arrhythmias is not an effective approach to preventing sudden cardiac death, but may even be deleterious. Three groups of drugs that have shown efficacy in preventing sudden cardiac death in patients with chronic heart failure are amiodarone, beta-blockers, and angiotensin-converting enzyme (ACE) inhibitors. Although how these drugs improve prognosis of heart failure are not clear at present, myocardial protection by these agents appears to be most important.

Histopathologic factors conducive to experimental ventricular tachycardia.

Ventricular tachyarrhythmia is the leading cause of sudden cardiac death. Determination of the substrates conducive to the initiation of this arrhythmia remains an important clinical goal. The purpose of this study was to correlate histopathologic findings, specifically: pattern (heterogeneous versus homogeneous infarct morphology), distribution (viable epicardial and/or endocardial rim), and infarct size, with susceptibility to the initiation of sustained ventricular tachycardia employing programmed electrical stimulation in two canine models of experimental myocardial infarction. Twenty-one adult dogs were randomly divided into two groups: 12 dogs underwent two-stage, 2-hour occlusion of the proximal left anterior descending coronary artery and nine animals underwent permanent, complete occlusion of the left anterior descending coronary artery with latex embolization. With programmed ventricular pacing with two premature ventricular extrastimuli, initiation of ventricular tachycardia was attempted, open chest, two weeks after infarction. Electrophysiologic evaluation of the infarct type correlated significantly with the histologic morphology of the infarction (p less than 0.001). The presence of a viable epicardial rim was an extremely important variable for ability to induce sustained ventricular tachycardia (p = 0.04). The presence of an endocardial rim was not significant (p = 1.0). Infarct size alone was only marginally related to ventricular tachycardia inducibility (p = 0.08). Nonuniform infarcts were more conducive to the initiation of sustained ventricular tachycardia than were homogeneous infarcts (p = 0.025). The presence of a large, nonuniform infarct correlated best with inducibility (p = 0.0002). Thus in these experimental models, specific infarct morphologies correlate significantly with susceptibility to inducible sustained ventricular tachyarrhythmias.

Repeat intervention for in-stent restenosis: re-expansion of the initial stent is a predictor of recurrence of restenosis.

BACKGROUND: In-stent restenosis has become a significant clinical problem as use of stents has increased. The optimal strategy for dealing with in-stent restenosis needs to be evaluated. OBJECTIVE: To compare the acute and late results of interventions for in-stent restenosis according to the device used, and to analyze the clinical and procedural variables of the lesions treated and identify the determinants of recurrence of restenosis and target lesion revascularization (TLR). METHODS: Procedural and late outcomes for 58 lesions in 50 patients who underwent repeat intervention for in-stent restenosis were analyzed. The results of interventions according to the device employed were compared. The predictors of recurrence of restenosis and TLR within 6 months were analyzed. The ratio of balloon diameter in repeat intervention to minimal lumen diameter after initial stenting (MLD0) was used as an index of re-expansion of stents. Serial intravascular ultrasound imaging was performed before and after repeat intervention for 33 lesions, and re-expansion of the initial stent was evaluated. RESULTS: Repeat intervention was successful in treating all lesions. Angiographic follow-up was possible for 49 lesions (84%). The overall incidences of recurrence of restenosis and TLR were 40.1 and 27.6%, respectively. Despite the immediate results having been good, the late results of stenting for in-stent restenosis were not favorable. Diffuse-type in-stent restenosis, early in-stent restenosis, and balloon diameter:MLD0 ratio > 1.25 are independent predictors of poor late results. Intravascular ultrasound findings have shown that expansion of the initial stent leads to recurrence of restenosis and TLR. CONCLUSIONS: Re-expansion of the initial stent can cause further vascular injury and there is a risk of recurrence of restenosis. Alternative therapeutic strategies that work without dilating the initial stent may be necessary for treating lesions with high risk of recurrence of restenosis.