The diagnosis of PVS is challenging because of nonspecific symptoms and the need for dedicated pulmonary vein imaging. There is no difference in acute success by type of initial intervention; however, stenting significantly reduces the risk of subsequent pulmonary vein restenosis in comparison with BA.

Given the central position of the focal adhesion complex, both physically in coupling integrins to the interstitium and biochemically in providing an upstream site for anabolic signal generation, we asked whether the recruitment of non-receptor tyrosine kinases to the cytoskeleton might be a mechanism whereby cellular loading could activate growth regulatory signals responsible for cardiac hypertrophy. Analysis revealed cytoskeletal association of c-Src, FAK, and ␤3-integrin, but no Fyn, in the pressure-overloaded right ventricle. This association was seen as early as 4 h after right ventricular pressure overloading, increased through 48 h, and reverted to normal in 1 week. Cytoskeletal binding of nonreceptor tyrosine kinases was synchronous with tyrosine phosphorylation of several cytoskeletal proteins, including c-Src. Examination of cytoskeleton-bound cSrc revealed that a significant portion of the tyrosine phosphorylation was not at the Tyr-527 site and therefore presumably was at the Tyr-416 site. Thus, these studies strongly suggest that non-receptor tyrosine kinases, in particular c-Src, may play a critical role in hypertrophic growth regulation by their association with cytoskeletal structures, possibly via load activation of integrin-mediated signaling.

Cardiac hypertrophy is characterized by both remodeling of the extracellular matrix (ECM) and hypertrophic growth of the cardiocytes. Here we show increased expression and cytoskeletal association of the ECM proteins fibronectin and vitronectin in pressureoverloaded feline myocardium. These changes are accompanied by cytoskeletal binding and phosphorylation of focal adhesion kinase (FAK) at Tyr-397 and Tyr-925, c-Src at Tyr-416, recruitment of the adapter proteins p130Cas , Shc, and Nck, and activation of the extracellular-regulated kinases ERK1/2. A synthetic peptide containing the Arg-Gly-Asp (RGD) motif of fibronectin and vitronectin was used to stimulate adult feline cardiomyocytes cultured on laminin or within a type-I collagen matrix. Whereas cardiocytes under both conditions showed RGD-stimulated ERK1/2 activation, only collagen-embedded cells exhibited cytoskeletal assembly of FAK, c-Src, Nck, and Shc. In RGD-stimulated collagenembedded cells, FAK was phosphorylated only at Tyr-397 and c-Src association occurred without Tyr-416 phosphorylation and p130Cas association. Therefore, cSrc activation is not required for its cytoskeletal binding but may be important for additional phosphorylation of FAK. Overall, our study suggests that multiple signaling pathways originate in pressure-overloaded heart following integrin engagement with ECM proteins, including focal complex formation and ERK1/2 activation, and many of these pathways can be activated in cardiomyocytes via RGD-stimulated integrin activation.Cardiovascular diseases such as hypertension, valvular defects, and myocardial infarction are often associated with the development of cardiac hypertrophy. This hypertrophy occurs in response to an increased mechanical (hemodynamic) load on the heart in the form of pressure or volume overload, which is characteristic of hypertension and valvular defects, or to a decrease in functional heart tissue as seen in myocardial infarction. The initial hypertrophic response of the heart is compensatory but frequently deteriorates into heart failure and increased morbidity/mortality (1, 2). This transition from compensation to failure occurs when further hypertrophy of the heart cannot normalize wall stress and maintain contractile function in the face of its hemodynamic load. Although mechanical load appears to directly regulate mass and associated phenotypic changes at the level of the cardiocyte (for a review see Ref.3), the mechanisms that couple load to the hypertrophic growth initiation and to the transition into heart failure have yet to be delineated. Whereas several key players including G-proteins (4), calcineurin (5, 6), mitogen-activated protein kinase (MAPK) 1 family members, namely, extracellular-regulated kinases (ERK1/2) (7) and p38 MAPK (8), as well as protein kinase C (9) and p70/85 S6 kinase (10, 11) have been implicated in the pathways that connect load to hypertrophic growth, the complexity of interaction between signaling pathways make deciphering them a difficult task in hypertrophic research.In an...

Increased microtubule density, for which microtubule stabilization is one potential mechanism, causes contractile dysfunction in cardiac hypertrophy. After microtubule assembly, α-tubulin undergoes two, likely sequential, time-dependent posttranslational changes: reversible carboxy-terminal detyrosination (Tyr-tubulin ↔ Glu-tubulin) and then irreversible deglutamination (Glu-tubulin → Δ2-tubulin), such that Glu- and Δ2-tubulin are markers for long-lived, stable microtubules. Therefore, we generated antibodies for Tyr-, Glu-, and Δ2-tubulin and used them for staining of right and left ventricular cardiocytes from control cats and cats with right ventricular hypertrophy. Tyr- tubulin microtubule staining was equal in right and left ventricular cardiocytes of control cats, but Glu-tubulin and Δ2-tubulin staining were insignificant, i.e., the microtubules were labile. However, Glu- and Δ2-tubulin were conspicuous in microtubules of right ventricular cardiocytes from pressure overloaded cats, i.e., the microtubules were stable. This finding was confirmed in terms of increased microtubule drug and cold stability in the hypertrophied cells. In further studies, we found an increase in a microtubule binding protein, microtubule-associated protein 4, on both mRNA and protein levels in pressure-hypertrophied myocardium. Thus, microtubule stabilization, likely facilitated by binding of a microtubule-associated protein, may be a mechanism for the increased microtubule density characteristic of pressure overload cardiac hypertrophy.

The mechanism by which ft blockade improves left ventricular dysfunction in various cardiomyopathies has been ascribed to improved contractile function of the myocardium or to improved ,8-adrenergic responsiveness. In this study we tested two hypotheses: (a) that chronic 13 blockade would improve the left ventricular dysfunction which develops in mitral regurgitation, and (b) that an important mechanism of this effect would be improved innate contractile function of the myocardium.Two groups of six dogs with chronic severe mitral regurgitation were studied. After 3 mo both groups had developed similar and significant left ventricular dysfunction. One group was then graduallyfl-blocked while the second group continued to be observed without further intervention. In the group that remained unblocked, contractile function remained depressed.However, in the group that received chronic ,f blockade, contractile function improved substantially.The contractility of cardiocytes isolated from the unblocked hearts and then studied in the absence of1f receptor stimulation was extremely depressed. However, contractility of cardiocytes isolated from the ,8-blocked ventricles was virtually normal. Consistent with these data, myofibrillar density was much higher, 55±4% in the f-blocked group vs. 39±2% (P < 0.01) in the unblocked group; thus, there were more contractile elements to generate force in the f-blocked group.We conclude that chronic ft blockade improves left ventricular function in chronic experimental mitral regurgitation. This improvement was associated with an improvement in the innate contractile function of isolated cardiocytes, which in turn is associated with an increase in the number of contractile elements. (J. Clin. Invest. 1994. 93:2639-2648.) Key words: mitral valve insufficiency * adrenergic fi receptor blockaders * ventricular function * left heart failure * congestive hypertrophy