Influence of gelsolin deficiency on excitation contraction coupling in adult murine cardiomyocytes.

Ion channels involved in cardiac excitation-contraction coupling are linked to the cytoskeleton. Therefore changes in the cytoskeletal actin filaments may influence cardiac membrane currents and electro-mechanical coupling. Depolymerization of actin filaments by gelsolin (gsn) is involved in the organisation of the cytoskeleton by leading to a lower polymerization state. Gsn is activated by Ca(2+) and inhibited by phosphoinositol-bisphosphate (PIP2). Furthermore, gsn has been linked to pathological conditions with reduced contractility like heart failure, amyloidosis and apoptosis. Thus, we hypothesize, that gsn deficiency may change electromechanical properties of freshly isolated ventricular cardiomyocytes. We recorded L-type Ca(2+) current (ICa,L) in whole-cell patch clamp mode in freshly isolated ventricular cardiomyocytes from gsn deficient ((-/-)) and control (gsn(+/+)) mice. Sarcomere shortening was monitored in field-stimulated myocytes from 0.5 Hz to 10 Hz by video microscopy. Shortening-frequency relation, post-rest potentiation and ß-adrenergic stimulation were investigated. ICa,L was increased in gsn(-/-) vs. gsn(+/+) myocytes. Sarcomere shortening amplitude and velocity were enhanced in gsn(-/-) vs. gsn(+/+) at all frequencies. Shortening-frequency relationship showed a biphasic pattern with decay in shortening amplitude between 0.5 and 2 Hz and an increase at higher frequencies in both genotypes. Post-rest characteristics revealed a frequency-dependent decay of post-rest potentiation in gsn(+/+) while it remained stable in gsn(-/-). In gsn(-/-) a reduced response to ß-adrenergic stimulation was observed. Resting sarcomere length was shorter in gsn(-/-) but neither increasing frequency nor ß-adrenergic stimulation induced further decay in any of the genotypes. In summary, gsn deficiency had a profound effect on excitiation-contraction properties and improved systolic function while not affecting diastolic function in unloaded isolated cardiomyocytes. Therefore, gsn mediated effects on contractility may play a role in patients with heart failure and cancer, where gsn levels are known to be elevated.

High prevalence of peripheral arterial disease in patients with obstructive sleep apnoea.

INTRODUCTION: Obstructive sleep apnoea (OSA) merits increasing attention as cardiovascular risk factor. Whereas carotid and coronary artery disease have been associated with OSA, occurrence of peripheral arterial disease (PAD) in OSA remains undefined. METHODS: We screened 100 patients with suspected OSA for PAD. After polysomnography, each patient underwent standardized angiological testing including ankle-brachial index (ABI), central pulse wave velocity, pulse wave index and duplex sonography. RESULTS: Among total study population, PAD prevalence accounted for 88%, of those 68% had asymptomatic plaques and 20% were symptomatic Fontaine ≥ IIa. In confirmed OSA, prevalence raised up to 98%. Except for smoking habits, distribution of established risk factors did not differ between OSA groups (patients without, mild, intermediate and severe OSA). Presence of plaque, Fontaine PAD stages and intermittent claudication exhibited significant gain with increasing AHI. A logistic regression model revealed that age (OR = 1.199, 95% CI [1.066; 1.348]) and the logarithmically transformed AHI (OR = 5.426, 95% CI [1.068; 27.567]) had the strongest influence on plaque presence. Central pulse wave velocity as marker of arterial stiffness was positively correlated with AHI. CONCLUSION: OSA is associated with a high prevalence of PAD. This implies substantial diseasés under-recognition and a presumable atherogenic role of OSA in the pathogenesis of PAD. However, vasoprotective impact of OSA treatment remains to be determined.

Prevalence and clinical relevance of the morphological substrate of ventricular arrhythmias in patients without known cardiac conditions detected by cardiovascular MR.

OBJECTIVE: Cardiac MR (CMR) identifies the substrate of ventricular arrhythmia (VA) in cardiomyopathies and coronary heart disease. However, little is known about the value of CMR in patients with VA without previously known cardiac disorders. METHODS: 76 patients with VA (Lown ≥2) without known cardiac disease after regular diagnostic work-up were studied with CMR, and findings were correlated with electrocardiogram (ECG) and electrophysiological stimulation (EPS). Structural abnormalities matching the VA origin as defined by ECG and/or EPS, or a CMR-detected cardiac condition known to cause arrhythmia were defined as VA substrate. CMR findings were defined as clinically relevant, if resulting in a new diagnosis, change of treatment or additional diagnostic procedure. RESULTS: 44/76 patients demonstrated pathological CMR findings. In 24/76 patients, the pathology was detected by CMR and not by echocardiography. CMR-based diagnoses of cardiac disease were established in 20/76 patients, and all were morphological substrates for VA. In seven patients, the location of the CMR finding (scar) directly matched the VA origin. CMR findings resulted in a change of treatment in 21 patients and/or additional diagnostics in 8 patients. CONCLUSION: Undetected cardiac conditions are frequent causes of VA. This is the first study demonstrating the value of CMR for detection of morphological substrate and/or underlying cardiac disorders in VA patients without known cardiac disease. ADVANCES IN KNOWLEDGE: The high incidence of clinically relevant CMR findings which were not detected during initial diagnostic work-up strongly supports the use of CMR to screen VA patients for underlying heart disease.

Method-related effects of adenovirus-mediated LacZ and SERCA1 gene transfer on contractile behavior of cultured failing human cardiomyocytes.

INTRODUCTION: Adenovirus-mediated gene transfer into cardiomyocytes has emerged as an interesting tool to study functional effects of single proteins. However, the functional consequences of cell isolation, cell culture per se and adenovirus-mediated transfer of the LacZ or SERCA1 gene in failing human cardiomyocytes warrant further investigation. METHODS: Primary cell culture was performed without or after adenovirus-mediated gene transfer of LacZ or SERCA1. Functional behavior of myocytes was assessed under basal conditions (field stimulation, 0.5 Hz, 37 degrees C), and during inotropic stimulation with isoproterenol (ISO; 10(-9)-10(-5) M), [Ca(2+)](o) (1.5-15 mM) or increasing stimulation rates (0.25-2.5 Hz). Results were compared to trabeculae from the same hearts. RESULTS: Freshly isolated myocytes showed full inotropic competence as compared to multicellular preparations. The response to stimulation with ISO and [Ca(2+)](o), as well as changes in stimulation rate resulted in a maximal increase in fractional cell shortening (FS) to 215+/-24% and 291+/-34%, and a frequency-dependent decline in FS to 46+/-5% of the basal value, respectively. After 48 h of cell culture, basal FS did not change significantly compared to fresh cells but both time to peak shortening and time to 50% relengthening were prolonged. After culture, the concentration-response curve for ISO was significantly shifted to the left (EC(50) 5.16 x 10(-8) vs. 1.12 x 10(-8) M, p<0.05). LacZ gene transfer caused efficient beta-Gal expression without affecting the inotropic responses to ISO or stimulation rate but impaired the contractile amplitude. SERCA1 gene transfer increased FS by 68% vs. LacZ and accelerated relengthening kinetics (+dL/dt 93+/-13 vs. 61+/-8 mum/s, p<0.05 vs. LacZ). DISCUSSION: Contractile responses of isolated human myocytes are comparable to multicellular preparations. The use of primary cell culture and adenovirus infection with CMV-promoter-mediated LacZ expression per se modulates contractile behavior in failing human myocytes. SERCA1 expression markedly improves contractile function. The method-related changes in contractile behavior observed here need to be taken into account in further studies.