Molecular basis for clinical heterogeneity in inherited cardiomyopathies due to myopalladin mutations.

Abnormalities in Z-disc proteins cause hypertrophic (HCM), dilated (DCM) and/or restrictive cardiomyopathy (RCM), but disease-causing mechanisms are not fully understood. Myopalladin (MYPN) is a Z-disc protein expressed in striated muscle and functions as a structural, signaling and gene expression regulating molecule in response to muscle stress. MYPN was genetically screened in 900 patients with HCM, DCM and RCM, and disease-causing mechanisms were investigated using comparative immunohistochemical analysis of the patient myocardium and neonatal rat cardiomyocytes expressing mutant MYPN. Cardiac-restricted transgenic (Tg) mice were generated and protein-protein interactions were evaluated. Two nonsense and 13 missense MYPN variants were identified in subjects with DCM, HCM and RCM with the average cardiomyopathy prevalence of 1.66%. Functional studies were performed on two variants (Q529X and Y20C) associated with variable clinical phenotypes. Humans carrying the Y20C-MYPN variant developed HCM or DCM, whereas Q529X-MYPN was found in familial RCM. Disturbed myofibrillogenesis with disruption of α-actinin2, desmin and cardiac ankyrin repeat protein (CARP) was evident in rat cardiomyocytes expressing MYPN(Q529X). Cardiac-restricted MYPN(Y20C) Tg mice developed HCM and disrupted intercalated discs, with disturbed expression of desmin, desmoplakin, connexin43 and vinculin being evident. Failed nuclear translocation and reduced binding of Y20C-MYPN to CARP were demonstrated using in vitro and in vivo systems. MYPN mutations cause various forms of cardiomyopathy via different protein-protein interactions. Q529X-MYPN causes RCM via disturbed myofibrillogenesis, whereas Y20C-MYPN perturbs MYPN nuclear shuttling and leads to abnormal assembly of terminal Z-disc within the cardiac transitional junction and intercalated disc.

Atrial natriuretic peptide exerts protective action against angiotensin II-induced cardiac remodeling by attenuating inflammation via endothelin-1/endothelin receptor A cascade.

We aimed to investigate whether atrial natriuretic peptide (ANP) attenuates angiotensin II (Ang II)-induced myocardial remodeling and to clarify the possible molecular mechanisms involved. Thirty-five 8-week-old male Wistar-Kyoto rats were divided into control, Ang II, Ang II + ANP, and ANP groups. The Ang II and Ang II + ANP rats received 1 µg/kg/min Ang II for 14 days. The Ang II + ANP and ANP rats also received 0.1 µg/kg/min ANP intravenously. The Ang II and Ang II + ANP rats showed comparable blood pressure. Left ventricular fractional shortening and ejection fraction were lower in the Ang II rats than in controls; these indices were higher (P < 0.001) in the Ang II + ANP rats than in the Ang II rats. In the Ang II rats, the peak velocity of mitral early inflow and its ratio to atrial contraction-related peak flow velocity were lower, and the deceleration time of mitral early inflow was significantly prolonged; these changes were decreased by ANP. Percent fibrosis was higher (P < 0.001) and average myocyte diameters greater (P < 0.01) in the Ang II rats than in controls. ANP decreased both myocardial fibrosis (P < 0.01) and myocyte hypertrophy (P < 0.01). Macrophage infiltration, expression of mRNA levels of collagen types I and III, monocyte chemotactic protein-1, and a profibrotic/proinflammatory molecule, tenascin-C (TN-C) were increased in the Ang II rats; ANP significantly decreased these changes. In vitro, Ang II increased expression of TN-C and endothelin-1 (ET-1) in cardiac fibroblasts, which were reduced by ANP. ET-1 upregulated TN-C expression via endothelin type A receptor. These results suggest that ANP may protect the heart from Ang II-induced remodeling by attenuating inflammation, at least partly through endothelin 1/endothelin receptor A cascade.

Ca2+/calmodulin-dependent kinase IIdelta causes heart failure by accumulation of p53 in dilated cardiomyopathy.

BACKGROUND: Dilated cardiomyopathy (DCM), characterized by dilatation and dysfunction of the left ventricle, is an important cause of heart failure. Many mutations in various genes, including cytoskeletal protein genes and contractile protein genes, have been identified in DCM patients, but the mechanisms of how such mutations lead to DCM remain unknown. METHODS AND RESULTS: We established the mouse model of DCM by expressing a mutated cardiac alpha-actin gene, which has been reported in patients with DCM, in the heart (mActin-Tg). mActin-Tg mice showed gradual dilatation and dysfunction of the left ventricle, resulting in death by heart failure. The number of apoptotic cardiomyocytes and protein levels of p53 were increased in the hearts of mActin-Tg mice. Overexpression of Bcl-2 or downregulation of p53 decreased the number of apoptotic cardiomyocytes and improved cardiac function. This mouse model showed a decrease in myofilament calcium sensitivity and activation of calcium/calmodulin-dependent kinase IIdelta (CaMKIIdelta). The inhibition of CaMKIIdelta prevented the increase in p53 and apoptotic cardiomyocytes and ameliorated cardiac function. CONCLUSIONS: CaMKIIdelta plays a critical role in the development of heart failure in part by accumulation of p53 and induction of cardiomyocyte apoptosis in the DCM mouse model.

Effect of efonidipine on TGF-ß1-induced cardiac fibrosis through Smad2-dependent pathway in rat cardiac fibroblasts.

Transforming growth factor beta-1 (TGF-ß1) plays a critical role in progression of cardiac fibrosis, which may involve intracellular calcium change. We examined effects of efonidipine, a dual T-type and L-type calcium channel blocker (CCB), on TGF-ß1-induced fibrotic changes in neonatal rat cardiac fibroblast. T-type and L-type calcium channel mRNAs were highly expressed in cultured cardiac fibroblasts. TGF-ß1 (5 ng/mL) significantly increased Smad2 phosphorylation and [(3)H]-leucine incorporation, which were attenuated by pretreatment with efonidipine (10 µM). Neither R(-)efonidipine (10 µM), selective T-type CCB, nor nifedipine (10 µM), selective L-type CCB, efficaciously inhibited both TGF-ß1-induced Smad2 phosphorylation and [(3)H]-leucine incorporation. However, both were markedly attenuated by combination of R(-)efonidipine and nifedipine, EDTA, or calcium-free medium. Pretreatment with Smad2 siRNA significantly attenuated [(3)H]-leucine incorporation induced by TGF-ß1. These data suggest that efonidipine elicits inhibitory effects on TGF-ß1- and Smad2-dependent protein synthesis through both T-type and L-type calcium channel-blocking actions in cardiac fibroblasts.

Survival and changes in physical ability after coronary revascularization for octa-nonagenerian patients with acute coronary syndrome.

Elderly populations are increasingly represented among patients with acute coronary syndrome (ACS), and advanced age has been identified as an important risk factor for death and adverse outcome in patients with ACS treated invasively. Although considerable data have demonstrated a prognostic benefit of early revascularization in ACS particularly in high-risk patients, elderly patients with ACS are treated invasively less often than younger patients because older age is thought to be an independent predictor of mortality after percutaneous coronary intervention (PCI) in ACS. Over the past 5 years, a total of 54 ACS patients over 85 years old were treated. The 6-month survival rate was around 50% in the non-PCI group (n = 12) and around 80% in the PCI group (n = 42) (P < 0.05). Cardiac death occurred in 6 patients in the PCI group and in 6 patients in the non-PCI group. The rates of both cardiac death and all-cause death were significantly lower in the PCI group. The change in ADL score before and 6 months after the procedure was from 1.57 to 1.59 in the PCI group and from 2.25 to 2.20 in the non-PCI group. PCI for elderly patients with ACS is safe and life saving, and does not reduce the ability to perform activities of daily living. PCI should be recommended even for octo-nonagenerians with ACS.

ATF6 is important under both pathological and physiological states in the heart.

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) evokes the ER stress response, including activating transcription factor 6 (ATF6), a key transcriptional activator to maintain cellular homeostasis. The ER stress has recently been reported to cause various diseases, but the role of ATF6 in the heart remains unknown. We clarified the role of ATF6 in the heart. The ATF6 activity was increased in the murine heart after myocardial infarction (MI). Treatment of mice with 4-(2-aminoethyl) benzenesulfonyl fluoride, an inhibitor of ATF6, further reduced cardiac function and increased the mortality rate at 14days after MI. Pharmacological inhibition of ATF6 induced dilatation of left ventricle and depression of cardiac function even in sham-operated murine hearts. The transgenic mice that expressed dominant negative mutant of ATF6 showed larger left ventricular dimension and reduced fractional shortening compared with wild-type littermates, resulting in death of heart failure at approximately 8weeks of age. In contrast, cardiac function after MI was better in transgenic mice that expressed constitutively active mutant of ATF6, compared with wild-type littermates. These results suggest that activation of the ER stress response factor ATF6 plays a critical role in not only protecting hearts under the pathological state but also maintaining cardiac function under the physiological state.

Enhanced expression of the S100A8/A9 complex in acute myocardial infarction patients.

BACKGROUND: S100A8/A9 complex (S100A8/A9) is expressed in activated human neutrophils and macrophages. Enhanced expression of S100A8/A9 in atherosclerotic plaque of patients with unstable angina pectoris (UAP) has been demonstrated, but its profile in acute myocardial infarction (AMI) has not been clarified. METHODS AND RESULTS: Serum S100A8/A9 levels were serially measured in patients with AMI (n=55) and UAP (n=16) during the acute period. The expression of S100A8/A9 was examined immunohistochemically in the infarcted myocardium of 7 autopsied patients with AMI. Serum S100A8/A9 levels on the 1st day were 1,118+/-115 (SE) ng/ml in AMI patients as compared with 787+/-147 ng/ml in UAP patients. On days 3-5, serum S100A8/A9 levels in AMI patients reached a peak value and were significantly higher than the values in UAP patients (1,690+/-144 ng/ml vs 844+/-100 ng/ml; P<0.0001). In AMI patients, peak S100A8/A9 levels positively correlated with peak white blood cell and neutrophil counts, and peak creatine kinase-MB and peak C-reactive protein levels. Double immunostaining revealed that S100A8/A9 was specifically expressed in neutrophils and macrophages infiltrating the infarcted myocardium. CONCLUSIONS: S100A8/A9 is implicated in the pathophysiology of AMI and may be an additional biomarker of the local inflammatory response following AMI.

Effects of acarbose on the acceleration of postprandial hyperglycemia-induced pathological changes induced by intermittent hypoxia in lean mice.

Postprandial hyperglycemia (PPH) and intermittent hypoxia related to the sleep apnea syndrome are important predictors of cardiovascular disease. We investigated the effects of intermittent hypoxia on pathological changes in the left ventricular (LV) myocardium caused by PPH in lean mice and evaluated the influence of acarbose, an α-glucosidase inhibitor. Male C57BL/6J mice aged 8 weeks were exposed to intermittent hypoxia (8 h/day during the daytime) or kept under normoxia. PPH was induced by restriction of feeding to 1-h periods twice a day, with the restricted diet (RD) mice receiving either standard chow or chow containing 0.02% acarbose. Another group of mice were fed standard chow ad libitum (AL). Plasma glucose levels after food intake were significantly elevated in RD but not in AL mice, and glucose levels were suppressed by acarbose. Intermittent hypoxia exacerbated cardiomyocyte hypertrophy and interstitial fibrosis in the LV myocardium of RD mice. Superoxide production and expression of 4-hydroxy-2-nonenal in the LV myocardium with intermittent hypoxia were increased in RD mice, but not AL mice. In addition, expression of tumor necrosis factor α (TNF-α) mRNA was increased in hypoxic RD mice. Treatment with acarbose inhibited oxidative stress and TNF-α mRNA expression and preserved the histological architecture of the LV myocardium.

Enhanced expression of the ubiquitin-proteasome system in the myocardium from patients with dilated cardiomyopathy referred for left ventriculoplasty: an immunohistochemical study with special reference to oxidative stress.

The ubiquitin (Ub)-proteasome system (UPS) is an important proteolytic mechanism for selecting and digesting cytotoxic proteins. The aim of this study is to elucidate expression and in situ localization of the UPS in the myocardium from patients with dilated cardiomyopathy (DCM) with refractory heart failure. The expression profile of the oxidative stress-induced cytotoxic proteins was also examined. Myocardium was obtained from 26 patients with DCM at the left ventriculoplasty. Ten normal autopsied hearts served as controls. Myocardial expressions of Ub and proteasomes were studied immunohistochemically. Oxidative stresses were examined in point of localization of the oxidation-induced modifier molecules (OMM). The relationship between immunohistochemical results and clinical parameters was also evaluated. Both Ub and proteasomes were stained positive in granular structures accumulating between the myofibrils and adjacent to nuclei in cardiomyocytes. The OMMs were also positive in the same Ub-positive granular structures. The area fraction of Ub, proteasomes and OMM was significantly higher in DCM hearts than in normal controls. Significant positive correlation was observed between the area fractions of Ub and plasma levels of brain natriuretic peptide (p = 0.046) in DCM hearts. In conclusion, enhanced expression of the UPS colocalized with OMM in cardiomyocytes may be involved in the pathophysiology of DCM hearts.

Suppression of inflammation in rat autoimmune myocarditis by S100A8/A9 through modulation of the proinflammatory cytokine network.

AIMS: S100A8/A9 is expressed in activated monocytes/macrophages and assumed to be heavily involved in the pathogenesis of acute inflammation. Although several studies have asserted that S100A8/A9 has a proinflammatory function, the exact biological function of S100A8/A9 is yet to be described. We examined the anti-inflammatory effects of S100A8/A9 on experimental autoimmune myocarditis (EAM) in rats. METHODS AND RESULTS: Experimental autoimmune myocarditis was induced in Lewis rats by immunization with porcine cardiac myosin. The recombinant (R-) S100A8/A9 was injected intraperitoneally into EAM rats. R-S100A8/A9 attenuated the severity of myocarditis, as evidenced by echocardiographic and histological findings. In addition, we found that not only the mRNA expression of proinflammatory cytokines [interleukin (IL)-1beta, IL-6, and tumour necrosis factor (TNF)-alpha] in the myocardium, but also their serum concentrations were suppressed in EAM rats treated with R-S100A8/A9. Nuclear factor-kappa B expression in inflammatory cells was also suppressed in the treated rats. To elucidate the mechanistic function of S100A8/A9 on proinflammatory cytokines in vivo, we used an ELISA on the supernatant of homogenized heart tissue treated with R-S100A8/A9. The findings revealed high-affinity binding of R-S100A8/A9 with IL-1beta, IL-6, and TNF-alpha in the myocardium, suggesting the trapping of proinflammatory cytokines by R-S100A8/A9. CONCLUSION: S100A8/A9 attenuates EAM through modulation of the proinflammatory cytokine network.

Olmesartan ameliorates myocardial function independent of blood pressure control in patients with mild-to-moderate hypertension.

Angiotensin II receptor blockers (ARBs) are suggested to be protective against myocardial hypertrophy and fibrosis, although such beneficial effects remain to be elucidated in the human heart. The aim of the present study was to examine the effect of a novel ARB, olmesartan, on myocardial function of the left ventricle in patients with mildto-moderate hypertension. We investigated 10 patients (6 men and 4 women, 62 +/- 7 years of age) who were stable with a single regimen of amlodipine, which was switched to olmesartan. Before and 8 months after changing medications, patients underwent echocardiographic examination and blood sampling, including measurement of the plasma high-sensitivity C-reactive protein (hsCRP) level. Peak velocities at the mitral annulus were determined by tissue Doppler imaging and used as measures of myocardial function. Olmesartan did not significantly alter blood pressure (BP) (systolic BP, 122 +/- 12 to 121 +/- 8 mmHg, P = 0.9; diastolic BP, 79 +/- 6 to 75 +/- 4 mmHg, P = 0.06) or parameters of global left ventricular systolic and diastolic function. Tissue Doppler imaging, however, revealed significant increases in the systolic (8.2 +/- 1.3 to 8.9 +/- 1.1 cm/s, P < 0.01) and early diastolic (6.7 +/- 0.9 to 7.6 +/- 1.0 cm/s, P = 0.02) velocities at the mitral annulus. This was associated with decreases in the left ventricular mass index (83 +/- 15 to 73 +/- 19 g/m2, P = 0.09) and hsCRP (683 +/- 555 to 655 +/- 450 ng/ml, P = 0.07). In conclusion, olmesartan improves myocardial function independent of BP reduction in hypertensive patients. Attenuated inflammatory changes as well as myocardial hypertrophy may play an important role.

Markedly increased intracellular lipid droplets and disruption of intercellular junctions in biopsied myocardium from a patient with arrhythmogenic right ventricular cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by the progressive replacement of myocardial cells by fat and fibrous tissue. Here we describe the histopathological features of biopsied myocardium from a patient with ARVC. A large amount of adipose tissue was present in the biopsy specimen, and a group of myocardial cells were isolated as an island-like region in the adipose tissue. Electron microscopic examination of cardiomyocytes revealed a large number of intracellular lipid droplets, including some extremely large droplets. Disruptions of the plasma membrane and dissociation of intercellular junctions were associated with discharge of intracellular lipid droplets into the interstitial space. The high accumulation of intracellular lipid droplets may be involved in the pathogenesis of ARVC and may have played an important role in myocardial cell death and progressive replacement of cardiomyocytes by fatty tissue in the current case.

Depressed myocardial contractile reserve in patients with obstructive sleep apnea assessed by tissue Doppler imaging with dobutamine stress echocardiography.

BACKGROUND: Hypoxia has been suggested to affect myocardial contractile function in patients with obstructive sleep apnea (OSA). We sought to determine whether myocardial contractile reserve (MCR), as evaluated by echocardiographic tissue Doppler imaging with dobutamine stress (TDDS), might be depressed in OSA patients. METHODS: Thirty patients with suspected OSA (25 men and 5 women; mean age, 51 +/- 11 years [+/- SD]) underwent overnight polysomnography and TDDS. Peak myocardial systolic velocity (Sm) and peak myocardial early diastolic velocity (Em) in the 12 myocardial segments of the left ventricular (LV) walls were averaged, and the mean Sm and Em during TDDS were compared between patients with apnea-hypopnea index (AHI) <15/h (group 1, n = 13) and those with AHI >/= 15/h (group 2, n = 17). MCR was calculated as the difference between the resting and peak Sm during TDDS. RESULTS: In both groups, Sm increased dose dependently during TDDS. However, the relative increase in Sm was significantly lower in group 2, resulting in a lower value of MCR (5.5 +/- 1.2 cm/s vs 7.4 +/- 1.3 cm/s, p < 0.001). The Em was lower in group 2 compared with group 1 throughout TDDS. MCR was correlated significantly with AHI (r = - 0.67, p < 0.0001), resting Em (r = 0.53, p < 0.005), and body mass index (r = - 0.46, p < 0.05) independent of the LV mass index. CONCLUSIONS: OSA can affect MCR, implying an etiologic contribution from repetitive hypoxic events. TDDS could identify subtle abnormalities of OSA-related cardiac involvement.

Angiotensin II receptor blocker reduces oxidative stress and attenuates hypoxia-induced left ventricular remodeling in apolipoprotein E-knockout mice.

Elevated superoxide formation in cardiac extracts of apolipoprotein E-knockout (apoE-KO) mice has been reported. In addition, we previously reported that hypoxia increased oxidative stress in the aortas of apoE-KO mice, although we did not examine the effect of hypoxia on the heart. The aim of this study was to investigate the effect of chronic hypoxia on the left ventricular (LV) remodeling in apoE-KO mice treated with or without an angiotensin II receptor blocker. Male apoE-KO mice (n=83) and wild-type mice (n=34) at 15 weeks of age were kept under hypoxic conditions (oxygen, 10.0+/-0.5%) and treated with olmesartan (3 mg/kg/day) or vehicle for 3 weeks. Although LV pressure was not changed, hypoxia caused hypertrophy of cardiomyocytes and increased interstitial fibrosis in the LV myocardium. Furthermore, nuclear factor-kappaB (NF-kappaB) and matrix metalloproteinase (MMP)-9 activities were increased in apoE-KO mice exposed to chronic hypoxia. Olmesartan effectively suppressed the 4-hydroxy-2-nonenal protein expression and NF-kappaB and MMP-9 activities, and preserved the fine structure of the LV myocardium without affecting the LV pressure. In conclusion, olmesartan reduced oxidative stress, and attenuated the hypoxia-induced LV remodeling, in part through the inhibition of NF-kappaB and MMP-9 activities, in apoE-KO mice.

Core protein of hepatitis C virus induces cardiomyopathy.

Hepatitis C virus (HCV) has been reported to be associated with cardiomyopathy. However, the mechanism of cardiomyopathy in chronic HCV infection is still unclear. Therefore, we investigate the development of cardiomyopathy in mice transgenic for the HCV-core gene. After the age of 12 months, mice developed cardiomyopathy that appeared as left ventricular dilatation, and systolic and diastolic dysfunction assessed by Doppler echocardiography. Histologically, hypertrophy of cardiomyocytes, cardiac fibrosis, disarray and scarcity of myofibrils, vacuolization and deformity of nuclei, myofibrillar lysis, streaming of Z-bands, and an increased number of bizarre-shaped mitochondria were found in HCV-core transgenic mice. These histological changes are just consistent with cardiomyopathy. In conclusion, the HCV-core protein directly plays an important role in the development of cardiomyopathy.

Gender difference of atorvastatin's vasoprotective effect in balloon-injured rat carotid arteries.

The effect of estrogen on neointimal formation in injured rat arteries has been reported to be a sexual dimorphic effect. Recently, it has been reported that 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) exhibit vasoprotective effects, which are independent of their cholesterol-lowering effects. In this study, we examined the gender differences of atorvastatin's effect on neointimal formation in balloon-injured rat arteries. Male and female Sprague Dawley rats underwent gonadectomy and balloon injury of the carotid artery. Ovariectomized female, as well as intact and castrated male, rats exhibited marked neointimal formation. Treatment with atorvastatin significantly reduced neointimal formation at day 14 (14 days after injury) and NADPH oxidase-dependent superoxide production at day 2 in ovariectomy, but not in intact and castrated males. In ovariectomized rats, 7 days of atorvastatin treatment from days -3 to 3 but not from days 7 to 14 suppressed neointimal formation at day 14. In this study, we showed that atorvastatin's effect on neointimal formation was female-specific and was more marked in ovariectomized female rats. NADPH oxidase-dependent superoxide production may be involved in the mechanism of the sexual dimorphic response seen in response to atorvastatin treatment. Furthermore, the results suggest the importance of treatment in the early phase after vascular injury.

Vascular endothelial growth factor-expressing mesenchymal stem cell transplantation for the treatment of acute myocardial infarction.

OBJECTIVE: Vascular endothelial growth factor (VEGF) plays an important role in inducing angiogenesis. Mesenchymal stem cells (MSCs) may have potential for differentiation to several types of cells, including myocytes. We hypothesized that transplantation of VEGF-expressing MSCs could effectively treat acute myocardial infarction (MI) by providing enhanced cardioprotection, followed by angiogenic effects in salvaging ischemic myocardium. METHODS AND RESULTS: The human VEGF165 gene was transfected to cultured MSCs of Lewis rats using an adenoviral vector. Six million VEGF-transfected and LacZ-transfected MSCs (VEGF group), LacZ-transfected MSCs (control group), or serum-free medium only (medium group) were injected into syngeneic rat hearts 1 hour after left coronary artery occlusion. At 1 week after MI, MSCs were detected by X-gal staining in infarcted region. High expression of VEGF was immunostained in the VEGF group. At 28 days after MI, infarct size, left ventricular dimensions, ejection fraction, E wave/A wave ratio and capillary density of the infarcted region were most improved in the VEGF group, compared with the medium group. Immunohistochemically, alpha-smooth muscle actin-positive cells were most increased in the VEGF group. CONCLUSIONS: This combined strategy of cell transplantation with gene therapy could be a useful therapy for the treatment of acute MI.

Usefulness of tissue Doppler imaging for demonstrating altered septal contraction sequence during dual-chamber pacing in obstructive hypertrophic cardiomyopathy.

Dual-chamber pacing reduces left ventricular (LV) outflow obstruction in patients with obstructive hypertrophic cardiomyopathy (HC), the mechanism of which lies in pacing-induced paradoxic septal motion. This study was conducted to test the hypothesis that tissue Doppler imaging (TDI) could demonstrate changes in the septal contraction sequence during dual-chamber pacing in patients with HC. TDI was performed in 16 patients (5 women; mean age 63+/-11 years) who underwent dual-chamber pacing for 7.6+/-2.1 year. With and without pacing, the time to peak systolic myocardial velocity was measured from the basal, mid, and distal segments in the 4 different LV walls. Without pacing, there was almost no longitudinal segmental asynchrony. During pacing, however, marked longitudinal segmental asynchrony appeared, especially in the anteroseptal wall (from p=NS to p<0.01 by analysis of variance) and the ventricular septum (from p<0.05 to p<0.01), with the time to peak velocity extremely prolonged at the distal segments. This was associated with a modest but significant decrease in the LV pressure gradient (from 20+/-8 to 14+/-7 mm Hg, p<0.01). In patients with obstructive HC, altered septal contraction sequence accounts for the reduced LV outflow obstruction during dual-chamber pacing, which was clearly demonstrated by TDI.