Effects of an interpolated premature ventricular contraction on the AV conduction of the subsequent premature atrial depolarization. An apparent facilitation

Nodal conduction is usually studied by tracing the H1 H2 on function of A1 A2 curves. If one interpolates a PVC before A1, there is a decrease in H1 H2. This might be explained by an A1 H1 interval lengthening (Δ A1 H1). This study was done on 14 consecutive patients in whom a PVC can be interpolated (blocked at the A-V junction). In the majority of these patients, there is a downward and a right hand shift in the curve after an interpolated PVC. On other hand, the curves representing the sum H1 H2+Δ A1 H1 on function of A1 A2 were shifted upward and to the right in 12 of the 14 patients. This indicates inhibition which manifests itself not only by an ERP increase but also by an A2 H2 increase.     

Fragmented QRS complex in patients with implantable cardioverter defibrillator—Prevalence and predisposing factors

Background

Incidence of fragmented (fQRS) and predisposing factors in patients with implantable cardioverter-defibrillator (ICD) have not yet been established.AimTo examine incidence of fQRS, associated factors as well as predictive value in identifying site of coronary artery disease (CAD).

Progression of Device-Detected Subclinical Atrial Fibrillation and the Risk of Heart Failure

Background

Long-term continuous monitoring detects short-lasting, subclinical atrial fibrillation (SCAF) in approximately one-third of older individuals with cardiovascular conditions. The relationship between SCAF, its progression, and the development of heart failure (HF) is unclear.

脂联素与缺血性脑血管病

脂联素是一种由脂肪细胞分泌的具有抗炎和抗动脉粥样硬化作用的肽类物质。现已发现,脂联素可阻止动脉粥样硬化的发生和发展。文章对脂联素在脑血管病,特别是缺血性卒中方面的最新研究做了综述,同时阐述了脂联素与其他传统血管性危险因素之间的密切关系。     

Obesity and lipoprotein cholesterol in the Framingham offspring study

This study examines the relationship between obesity and low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and very-low-density lipoprotein (VLDL) cholesterol in 4260 young adult men and women. The strongest association between obesity and LDL cholesterol was found in 20–29 yr-old males, the weakest in 40–49-yr-old males. Conversely, in women the relationship between LDL cholesterol and obesity was modest except in the oldes (40–49 yr) age group. An inverse relationship between obesity and HDL cholesterol was of similar shape and strength in all sex and age-specific groups. When the ratio of total cholesterol (TCHOL) to HDL cholesterol was compared in lean and grossly obese 20–29-yr-old males, substantial differences were found. Since other data show this index of the lipoprotein profile to be the single best indicator of CHD risk, it would appear that the atherogenic potential of obesity is greater than would be suggested by the relatively weak association between obesity and TCHOL or any single lipoprotein cholesterol. These data also suggest that the impact of obesity as a risk factor for CHD may have been underestimated. The paucity of lean males 40–49-yr-old prevents firm conclusions about the CHD risk in such a group. Indirect evidence indicates that lean 40–49-yr-old men would have a markedly more favorable lipoprotein profile and consequently a much lower risk of CHD.     

Initiation of two distinct forms of atrioventricular nodal reentrant tachycardia during programmed ventricular stimulation in man

Of 42 patients with supraventricular tachycardia related to dual atrioventricular (A-V) nodal pathway conduction, 8 had sustained tachycardia induced during programmed ventricular stimulation. The characteristics of the tachycardia in three patients suggested that the A-V nodal reentrant tachycardia used a slow pathway for anterograde conduction and a fast pathway for retrograde conduction (slow-fast form). In these patients, the retrograde effective refractory period was longer in the slow than in the fast pathway. Ventriculoatrial (V-A) conduction curves (V₁-V₂, A₁-A₂) were smooth. Ventricular premature beats, being conducted retrograde over the fast pathway, could activate the slow pathway in an anterograde direction, initiating the slow-fast form of A-V nodal reentrant tachycardia. In the remaining five patients, the tachycardia used a fast pathway for anterograde conduction and a slow pathway for retrograde conduction (fast-slow form). In these patients, the retrograde effective refractory period was longer in the fast than in the slow pathway. V-A conduction curves (V₁-V₂, A₁-A₂) could be either smooth or discontinuous if there was a sudden increase in V-A conduction time. Ventricular premature beats, conducted retrograde over the slow pathway, could activate the fast pathway in an anterograde direction, establishing a tachycardia circuit in reverse of the slow-fast form. In both groups of patients, the ventricular pacing cycle length appeared to be a crucial factor in the ability to expose functional discordance between the two A-V nodal pathways during retrograde conduction.The fast-slow form of A-V nodal reentrant tachycardia, similar to the slow-fast form, could also be induced during atrial premature stimulation in two patients. In this situation, the slow pathway having an anterograde effective refractory period longer, than that of the fast pathway was a requisite condition; anterograde A-V nodal conduction curves (A₁-A₂, H₁-H₂) were smooth. Atrial premature beats, conducted anterograde over the fast pathway, could activate the slow pathway in a retrograde direction resulting In an atrial echo or sustained fast-slow form of A-V nodal reentrant tachycardia.     

The Role of Viscosity Estimation for Oil-in-gelatin Phantom in Shear Wave Based Ultrasound Elastography

Shear wave based ultrasound elastography utilizes mechanical excitation or acoustic radiation force to induce shear waves in deep tissue. The tissue response is monitored to obtain elasticity information about the tissue. During the past two decades, tissue elasticity has been extensively studied and has been used in clinical disease diagnosis. However, biological soft tissues are viscoelastic in nature. Therefore, they should be simultaneously characterized in terms of elasticity and viscosity. In this study, two shear wave-based elasticity imaging methods, shear wave dispersion ultrasound vibrometry (SDUV) and acoustic radiation force impulsive (ARFI) imaging, were compared. The discrepancy between the measurements obtained by the two methods was analyzed, and the role of viscosity was investigated. To this end, four types of gelatin phantoms containing 0%, 20%, 30% and 40% castor oil were fabricated to mimic different viscosities of soft tissue. For the SDUV method, the shear elasticity μ₁ was 3.90 ± 0.27 kPa, 4.49 ± 0.16 kPa, 2.41 ± 0.33 kPa and 1.31 ± 0.09 kPa; and the shear viscosity μ₂ was 1.82 ± 0.31 Pa•s, 2.41 ± 0.35 Pa•s, 2.65 ± 0.13 Pa•s and 2.89 ± 0.14 Pa•s for 0%, 20%, 30% and 40% oil, respectively in both cases. For the ARFI measurements, the shear elasticity μ was 7.30 ± 0.20 kPa, 8.20 ± 0.31 kPa, 7.42 ± 0.21 kPa and 5.90 ± 0.36 kPa for 0%, 20%, 30% and 40% oil, respectively. The SDUV results demonstrated that the elasticity first increased from 0% to 20% oil and then decreased for the 30% and 40% oil. The viscosity decreased consistently as the concentration of castor oil increased from 0% to 40%. The elasticity measured by ARFI showed the same trend as that of the SDUV but exceeded the results measured by SDUV. To clearly validate the impact of viscosity on the elasticity estimation, an independent measurement of the elasticity and viscosity by dynamic mechanical analysis (DMA) was conducted on these four types of gelatin phantoms and then compared with SDUV and ARFI results. The shear elasticities obtained by DMA (3.44 ± 0.31 kPa, 4.29 ± 0.13 kPa, 2.05 ± 0.29 kPa and 1.06 ± 0.18 kPa for 0%, 20%, 30% and 40% oil, respectively) were lower than those by SDUV, whereas the shear viscosities obtained by DMA (2.52 ± 0.32 Pa·s, 3.18 ± 0.12 Pa·s, 3.98 ± 0.19 Pa·s and 4.90 ± 0.20 Pa·s for 0%, 20%, 30% and 40% oil, respectively) were greater than those obtained by SDUV. However, the DMA results showed that the trend in the elasticity and viscosity data was the same as that obtained from the SDUV and ARFI. The SDUV results demonstrated that adding castor oil changed the viscoelastic properties of the phantoms and resulted in increased dispersion of the shear waves. Viscosity can provide important and independent information about the inner state of the phantoms, in addition to the elasticity. Because the ARFI method ignores the dispersion of the shear waves, namely viscosity, it may bias the estimation of the true elasticity. This study sheds further light on the significance of the viscosity measurements in shear wave based elasticity imaging methods.     

In Vivo Measures of Shear Wave Speed as a Predictor of Tendon Elasticity and Strength

The purpose of this study was to assess the potential for ultrasound shear wave elastography (SWE) to measure tissue elasticity and ultimate stress in both intact and healing tendons. The lateral gastrocnemius (Achilles) tendons of 41 New Zealand white rabbits were surgically severed and repaired with growth factor coated sutures. SWE imaging was used to measure shear wave speed (SWS) in both the medial and lateral tendons pre-surgery, and at 2 and 4 wk post-surgery. Rabbits were euthanized at 4 wk, and both medial and lateral tendons underwent mechanical testing to failure. SWS significantly (p < 0.001) decreased an average of 17% between the intact and post-surgical state across all tendons. SWS was significantly (p < 0.001) correlated with both the tendon elastic modulus (r = 0.52) and ultimate stress (r = 0.58). Thus, ultrasound SWE is a potentially promising non-invasive technology for quantitatively assessing the mechanical integrity of pre-operative and post-operative tendons.