Empagliflozin inhibits increased Na influx in atrial cardiomyocytes of patients with HFpEF

AIMS

Heart failure with preserved ejection fraction (HFpEF) causes substantial morbidity and mortality. Importantly, atrial remodeling and atrial fibrillation is frequently observed in HFpEF. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have recently been shown to improve clinical outcomes in HFpEF, and post-hoc analyses suggest atrial antiarrhythmic effects. We tested if isolated human atrial cardiomyocytes from patients with HFpEF exhibit an increased Na influx, which is known to cause atrial arrhythmias, and if that is responsive to treatment with the SGTL2i empagliflozin.

METHODS AND RESULTS

Cardiomyocytes were isolated from atrial biopsies of 124 patients (82 with HFpEF) undergoing elective cardiac surgery. Na influx was measured with the Na-dye Asante Natrium Green-2 AM (ANG-2). Compared to patients without heart failure (NF), Na influx was doubled in HFpEF patients (NF vs HFpEF: 0.21±0.02 vs 0.38±0.04 mmol/L/min (N=7 vs 18); p=0.0078). Moreover, late INa (measured via whole-cell patch clamp) was significantly increased in HFpEF compared to NF. Western blot and HDAC4 pulldown assay indicated a significant increase in CaMKII expression, CaMKII autophosphorylation, CaMKII activity, and CaMKII-dependent NaV1.5 phosphorylation in HFpEF compared to NF, whereas NaV1.5 protein and mRNA abundance remained unchanged. Consistently, increased Na influx was significantly reduced by treatment with the CaMKII inhibitor autocamtide-2 related inhibitory peptide (AIP), late INa inhibitor tetrodotoxin (TTX) but also with NHE1 inhibitor cariporide. Importantly, empagliflozin abolished both increased Na influx and late INa in HFpEF. Multivariate linear regression analysis, adjusting for important clinical confounders, revealed HFpEF to be an independent predictor for changes in Na handling in atrial cardiomyocytes.

CONCLUSION

We show for the first time increased Na influx in human atrial cardiomyocytes from HFpEF patients, partly due to increased late INa and enhanced NHE1-mediated Na influx. Empagliflozin inhibits Na influx and late INa, which could contribute to antiarrhythmic effects in patients with HFpEF.

Empagliflozin inhibits increased Na influx in HFpEF cardiomyocytes and reduces arrhythmic activity in human atrial trabeculae

Background

Heart failure with preserved ejection fraction (HFpEF) is a major health problem associated with substantial morbidity and mortality. However, the underlying pathophysiological mechanisms are poorly understood, and effective treatment strategies are scarce. Importantly, SGLT2i, which have been suggested to improve cellular Na and Ca homeostasis in HFrEF, have recently been shown to also improve clinical outcomes in patients with HFpEF. Interestingly, post-hoc analyses of clinical data suggest an involvement of anti-arrhythmic effects of SGLT2i.

Purpose

We tested, if isolated human atrial cardiomyocytes from patients with HFpEF exhibit an increased Na influx that is responsive to treatment with the SGLT2i empagliflozin (Empa) and if Empa has anti-arrhythmic properties in human atrial trabeculae.

Methods

Atrial biopsies were obtained from 101 patients undergoing elective cardiac surgery. Na influx was measured as increase in [Na]i during Na/K-ATPase inhibition in isolated cardiomyocytes loaded with the Na-sensitive fluorescence dye Asante Natrium Green–2 AM (ANG-2). Western Blot and HDAC4 pulldown assay were used to investigate NaV1.5 expression/phosphorylation as well as CaMKII expression/autophosphorylation and activity. Anti-arrhythmic effects of Empa were evaluated as the reduction in premature atrial complexes (PACs), which were induced in electrically field-stimulated (1Hz) human atrial trabeculae by superfusion with isoproterenol (100 nM) and high Ca (3.5 mM).

Results

Compared to patients without heart failure (NF), Na influx was almost doubled in HFpEF patients (NF vs HFpEF: 0.21±0.02 vs 0.38±0.04 mmol/L/min (N=7 vs 18); p=0.005) (Fig. 1D, E). CaMKII expression, CaMKII autophosphorylation, CaMKII activity, and CaMKII-dependent NaV1.5 phosphorylation were significantly increased in atrial biopsies of HFpEF patients, whereas NaV1.5 protein abundance remained unchanged (Fig. 1A–C). Consistent with these results, the increased Na influx was significantly reduced by treatment with the specific CaMKII inhibitor autocamtide-2 related inhibitory peptide (AIP) and the late INa inhibitor tetrodotoxin (TTX) (Fig. 1D, E). Importantly, Empa also abolished the increased Na influx in HFpEF cardiomyocytes (Fig. 1D, E). Multivariate linear regression analysis, adjusting for clinical co-variates, revealed HFpEF to be an independent predictor of cardiomyocyte Na handling. In line with Empa-mediated inhibition of Na influx, the frequency of PACs in human atrial trabeculae was significantly reduced by Empa (Fig. 1F, G).

Conclusion

This is the first study to demonstrate increased Na influx in human cardiomyocytes from HFpEF patients potentially by an increased CaMKII-dependent NaV1.5 phosphorylation. Excitingly, treatment with Empa decreases this Na influx in HFpEF cardiomyocytes and reduces isoproterenol-induced arrhythmic activity in human atrial trabeculae, which could contribute to the cardioprotective effects of this drug in patients with HFpEF.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Else Kröner-Fresenius-Stiftung,Deutsche Forschungsgemeinschaft

Oxidative activation of CaMKII mediates arrhythmias and contractile dysfunction in an obstructive sleep apnea mouse model

Background/Introduction

Atrial arrhythmias frequently occur in patients with obstructive sleep apnea (OSA), but the underlying mechanisms remain insufficiently understood. We recently demonstrated that CaMKII-dependent pro-arrhythmic activity is increased in patients with OSA, but the mechanisms of CaMKII activation remain unknown. Interestingly, OSA can lead to increased reactive oxygen species production, which may facilitate CaMKII activation by oxidation at methionine residues 281/282.

Purpose

We tested if oxidation of CaMKII is involved in the development of arrhythmias and contractile dysfunction in vitro and in vivo in a mouse model of obstructive sleep apnea by tongue enlargement.

Methods

Experiments were performed using 41 wild-type (WT) and 25 genetically modified mice lacking oxidative CaMKII activation due to mutation of methionine 281/282 to valine (MMVV mice). Polytetrafluorethylene (PTFE, 100 μl) was injected into the tongue of 23 WT and 12 MMVV mice to induce OSA by sustained tongue enlargement as previously established. Whole body plethysmography was performed to confirm success of intervention. Echocardiography was performed at baseline and after 8 weeks to assess left-ventricular function. After 8 weeks, isolated atrial and ventricular cardiomyocytes were incubated with the Ca-sensitive dye FURA-2 AM (5 μM, 15 min) and analyzed with epifluorescence microscopy under regular electrical field stimulation (1 Hz).

Results

PTFE injection resulted in an increased frequency of inspiratory flow limitations (IFLs/h) from 27.4±5.95 to 59.6±6.22 in PTFE mice (p<0.001, fig. 1A). Interestingly, in WT PTFE mice, left ventricular ejection fraction (LVEF, in %) was reduced at 8 weeks post procedure from 57.0±1.36 to 51.5±1.85 (p=0.001, fig. 1B). Importantly, mice lacking oxidative CaMKII activation were protected from such decline in contractile function, and LVEF was higher at 8 weeks vs. WT PTFE (p<0.001, fig. 1B). Congruent with deterioration of contractility in vivo, the Ca transient amplitude after 30s pause (normalized to steady-state before pause) was decreased in ventricular cardiomyocytes of WT PTFE mice indicating increased SR Ca leak (p for interaction genotype x PTFE = 0.014, fig. 1C). In contrast to WT, the post-pause ratio was increased in MMVV PTFE mice (p=0.018, fig. 1C). In addition to contractile function, cellular arrhythmic events were analyzed as non-stimulated pro-arrhythmic events (NSEs) during steady-state electrical field stimulation at 1 Hz (fig. 1D, red arrows). NSE frequency was increased in atrial cardiomyocytes from WT PTFE mice with 0.050±0.005 compared to 0.018±0.003 s–1 in WT CTRL (p<0.001, fig. 1D). Intriguingly, MMVV mice were protected from NSEs after PTFE treatment (0.020±0.004, p<0.001 vs. WT PTFE, Fig. 1D).

Conclusion

In a mouse model of obstructive sleep apnea, contractile dysfunction and pro-arrhythmic activity are modulated by oxidative CaMKII activation, which may have therapeutic implications.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft; Medical Faculty at University of Regensburg

Increased NaV1.8 expression in patients with sleep-disordered breathing induces pro-arrhythmic activity

Background

Sleep-disordered breathing (SDB) is often associated with atrial fibrillation, but detailed mechanisms remain elusive. Interestingly, late Na current (late INa) has been shown to be increased in patients with SDB, while expression of cardiac Na channel NaV1.5 and peak Na current were decreased. Indeed, recent data demonstrated that enhanced NaV1.8-dependent late INa may also induce pro-arrhythmic activity.

Purpose

We tested whether Na-V1.8 expression and subsequent NaV1.8-dependent pro-arrhythmic activity are increased in patients with SDB.

Methods

We prospectively analysed 29 right atrial appendage biopsies of patients undergoing elective coronary artery bypass grafting. SDB was assessed using polygraphy in the preoperative night and an apnoea-hypopnea index (AHI) ≥15/h defined SDB. Micro-dissected atrial trabeculae were electrically field stimulated (at 1 Hz, 5 V for 50 ms, at 37°C) to elicit regular contractions. Trabecular arrhythmias were induced using 100 nM isoproterenol at [Ca]o of 3.5 mmol/L and pro-arrhythmic activity was scored from 0 (no arrhythmias) to 5 (salve). Sarcoplasmic reticulum Ca leak was estimated by the contractility after paused stimulation (at 2 Hz, normalized to before pause). To correlate functional and expression data for each individual patient, NaV1.8 mRNA expression was quantified in each trabeculum using qPCR.

Results

NaV1.8 mRNA expression was increased in patients with SDB, leading to a significant positive correlation with the severity of SDB (i.e. AHI, p=0.02, r2=0.22, Fig. 1A). Multivariate regression analysis revealed that this association was independent from age, sex, atrial fibrillation, heart failure, diabetes mellitus, and renal function (p=0.03, r2=0.35). Accordingly, selective NaV1.8 blockade with PF-01247324 (PF, 1 μM, 30 min) significantly improved post-pause contractility of isolated trabeculae from 1.69±0.31 to 2.95±0.54 in patients with SDB (p=0.001), whereas no significant improvement was observed in patients without SDB. This resulted in significant positive correlations between the PF-dependent improvement of post-pause contractility and both AHI (p=0.047, r2=0.19) and NaV1.8 mRNA expression (p=0.03, r2=0.17). Most importantly, we also observed a significant increase in arrhythmia severity in patients with SDB of 2.21±0.52 (vs. 1.00±0.49, p=0.03) that could be significantly reduced by selective NaV1.8 inhibition with PF to 0.25±0.18 (p=0.0008, Fig. 1B). In accordance, there was a significant positive correlation between arrhythmia severity and AHI (p=0.01, r2=0.28) that was abolished in the presence of PF (interaction analysis: p=0.ehab724.33141, r2=0.46).

Conclusion

In patients with SDB, enhanced NaV1.8 expression contribute to atrial pro-arrhythmic activity independent from comorbidities. Selective NaV1.8 inhibition may have therapeutic implications for patients with SDB.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Part of the study was supported by grants from Philips Respironics (Murrysville, PA 15668) and the Medical Faculty at the University of Regensburg. Figure 1

Inhibition of cardiac potassium currents by oxidation-activated protein kinase A contributes to early afterdepolarizations in the heart

Reactive oxygen species (ROS) have been shown to prolong cardiac action potential duration resulting in afterdepolarizations, the cellular basis of triggered arrhythmias. As previously shown, protein kinase A type I (PKA I) is readily activated by oxidation of its regulatory subunits. However, the relevance of this mechanism of activation for cardiac pathophysiology is still elusive. In this study, we investigated the effects of oxidation-activated PKA I on cardiac electrophysiology. Ventricular cardiomyocytes were isolated from redox-dead PKA-RI Cys17Ser knock-in (KI) and wild-type (WT) mice and exposed to H₂O₂ (200 µmol/L) or vehicle (Veh) solution. In WT myocytes, exposure to H₂O₂ significantly increased oxidation of the regulatory subunit I (RI) and thus its dimerization (threefold increase in PKA RI dimer). Whole cell current clamp and voltage clamp were used to measure cardiac action potentials (APs), transient outward potassium current (I_to) and inward rectifying potassium current (I_K1), respectively. In WT myocytes, H₂O₂ exposure significantly prolonged AP duration due to significantly decreased I_to and I_K1 resulting in frequent early afterdepolarizations (EADs). Preincubation with the PKA-specific inhibitor Rp-8-Br-cAMPS (10 µmol/L) completely abolished the H₂O₂-dependent decrease in I_to and I_K1 in WT myocytes. Intriguingly, H₂O₂ exposure did not prolong AP duration, nor did it decrease I_to, and only slightly enhanced EAD frequency in KI myocytes. Treatment of WT and KI cardiomyocytes with the late I_Na inhibitor TTX (1 µmol/L) completely abolished EAD formation. Our results suggest that redox-activated PKA may be important for H₂O₂-dependent arrhythmias and could be important for the development of specific antiarrhythmic drugs.NEW & NOTEWORTHY Oxidation-activated PKA type I inhibits transient outward potassium current (I_to) and inward rectifying potassium current (I_K1) and contributes to ROS-induced APD prolongation as well as generation of early afterdepolarizations in murine ventricular cardiomyocytes.

Abnormal P-waves found in patients with sleep-disordered breathing are associated with triggered pro-arrhythmic activity

Background

Sleep-disordered breathing (SDB) is frequently associated with atrial arrhythmias, but diagnostic markers that predict the propensity for atrial arrhythmias are missing. Abnormal P-wave terminal force in lead V1 (PTFV1) has been associated with atrial structural/electrical remodeling and arrhythmias.

Purpose

Here we investigate the association of triggered pro-arrhythmic activity with abnormal PTFV1 in human right atrial appendage biopsies of patients without and with SDB.

Methods

30 patients undergoing elective coronary artery bypass grafting were screened for SDB by polygraphy. An apnoea-hypopnea index (AHI) of ≥15/h defined SDB. PTFV1 was measured as product of negative P-wave amplitude and duration in lead V1 and was defined as abnormal if >4000 ms*μV. Ca/Calmodulin-dependent protein kinase II (CaMKII) activity was measured in human right atrial appendage biopsies by a specific HDAC4 pull-down assay. Premature atrial contractions (PACs) were triggered by exposure to 100 nM isoproterenol (at 3.5 mM [Ca]o) in human atrial trabeculae. PACs severity was classified by a score from 0 points (no arrhythmias) to 5 points (salve). In addition, atrial fibrosis was quantified by Masson's trichrome stain in cryo-sectioned atrial tissue. Multivariate linear regression analyses were performed accounting for age, sex, BMI, existing AF, heart failure, diabetes, and creatinine.

Results

Interestingly, the AHI was independently associated with the magnitude of PTFV1 (fig. A+B, B=57.47±21.03, R2=0.48, P=0.01). Importantly, patients with an abnormal PTFV1 had a significantly increased CaMKII activity (fig. C, P=0.04) and showed significantly more severe triggered PACs (fig. D, P=0.02). Moreover, the magnitude of PTFV1 correlated significantly and independently with PAC severity (fig. D, B=0.0005±0.0002, R2=0.50, P=0.03). Consistently, these arrhythmias could be significantly reduced by acute CaMKII inhibition (5 μM KN93, P<0.01), which abolished the correlation between PTFV1 and PAC severity (P=N.S.). Surprisingly, atrial fibrosis was significantly decreased in patients with an abnormal PTFV1 (fig. E, P=0.02), suggesting that abnormal PTFV1 is a marker of proarrhythmic atrial electrical remodeling of functional cardiomyocytes but not of fibrotic tissue.

Conclusion

The severity of sleep-disordered breathing (AHI) is independently associated with an abnormal PTFV1. Intriguingly, this abnormality is associated with an increased CaMKII activity and with CaMKII-dependent arrhythmias, suggesting PTFV1 to be a potential tool to evaluate the pro-arrhythmic risk of patients with SDB.

Figure 1

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Part of this study was funded by Philips Respironics.

P4521C-reactive protein as a predictor for diastolic dysfunction in patients with sleep-disordered breathing

Background

Sleep-disordered breathing (SDB) is often associated with left ventricular diastolic dysfunction, but the mechanisms are poorly understood. SDB may increase systemic inflammation that could induce myocardial fibrosis leading to diastolic dysfunction.

Purpose

Systemic inflammation and diastolic dysfunction were analysed in patients with SDB.

Methods

295 patients undergoing coronary artery bypass grafting were included in the prospective observational trial CONSIDER-AF (NCT02877745). They were screened for SDB in the preoperative night and an apnoea-hypopnea index (AHI) of ≥15/h defined SDB. Preoperative echocardiography was used to measure the ratio of early (E) and late (A) diastolic transmitral flows (E/A), early diastolic mitral annular velocity (E'), the ratio E/E', LA volume index, and tricuspid regurgitation velocity. Left ventricular diastolic dysfunction was graded I-IV according to current guidelines. Patients with ventricular ejection fraction of less than 45% were excluded. We used serum C-reactive protein (CRP) as a marker for systemic inflammation, resulting in a full data set for 170 patients.

Results

In patients with SDB, serum CRP levels were 3.036 mg/L higher than in control patients (95% confidence interval: −0.393–6.466, P=0.082). Intriguingly, the severity of SDB (AHI) correlated significantly with the CRP levels (coefficient B: 0.13±0.06, P=0.021). CRP also correlated with the severity of diastolic dysfunction (coefficient B: 0.010±0.004, P=0.009). Importantly, multivariable linear regression analysis accounting for the potential confounders age, sex, body-mass index, existing atrial fibrillation, diabetes, AHI, and creatinine indicated that CRP was an independent predictor for the severity of diastolic dysfunction (coefficient B: 0.009±0.004, P=0.016). Interestingly, the latter effect was still present considering just patients with SDB (coefficient B: 0.013±0.005, P=0.015, N=72), but was completely abolished in patients without SDB (coefficient B: 0.001±0.007, P=0.912, N=98), indicating a potential SDB-dependence.

Conclusion

Systemic inflammation (CRP) is associated with the severity of SDB (AHI). Interestingly, only in SDB patients CRP predicts significantly and independently the severity of diastolic dysfunction. Consequently, anti-inflammatory therapeutic strategies could be beneficial for patients with SDB and diastolic dysfunction.

Acknowledgement/Funding

This study was supported by Philips Respironics and the Medical Faculty of the University of Regensburg.

P3508A novel mouse model of sleep-disordered breathing is associated with contractile dysfunction and CaMKII overexpression

Background

Patients with sleep-disordered breathing (SDB) develop arrhythmias and contractile dysfunction, but the mechanisms are poorly understood, possibly due to the lack of mouse models that mimic airway obstruction in spontaneously sleeping mice. Interestingly, New Zealand obese mice have been shown to develop airway obstruction with inspiratory flow limitation resulting in apneas, but these mice also develop diabetes.

Purpose

We developed a novel mouse model of increased airway obstruction in spontaneously sleeping lean mice and investigated the impact on sleep-related apneas and contractile function.

Methods and results

Male C57BL6 mice at 8–12 weeks of age were subjected to polytetrafluoroethylene (PTFE) injection (100 μl) into the tongue. This resulted in an increased tongue volume and reduced pharyngeal luminal diameter. Conscious mice behave normal and there was no difference in body weight between PTFE injected mice and untreated littermates (control). Whole body plethysmography was used to monitor spontaneous breathing for 8h in a quiet environment. Interestingly, compared to control, mice with PTFE injection showed a significantly increased frequency of apneas (lasting >1s, fig. A, * indicated P<0.05, t-test). Echocardiographic analysis revealed that ejection fraction was significantly reduced in PTFE-treated mice 8 weeks after surgery (vs. control, fig. B). In accordance, the developed force of isolated papillary muscles from hearts of PTFE mice was significantly reduced compared to control (fig. C). Ca/calmodulin-dependent protein kinase II (CaMKII) has been implicated in the development of heart failure. Intriguingly, compared to control, CaMKII expression was significantly increased in ventricular heart homogenates of PTFE-treated mice (fig. D). Moreover, the magnitude of CaMKII overexpression correlated significantly with the frequency of apneas (fig. E). Papillary muscle post-pause contractions can be used as measure of diastolic sarcoplasmic reticulum (SR) Ca leak, which is known to be enhanced by CaMKII. Compared to control, post-pause contraction amplitude was significantly smaller in PTFE-treated mice, indicating an increased SR Ca leak (fig. F).

Figure 1

Conclusion

PTFE injection in mice results in an increased frequency of spontaneous apneas. PTFE-treated mice develop mild contractile dysfunction, which is accompanied by CaMKII overexpression. This novel mouse model offers great opportunities for investigation of sleep-related breathing disorders.

Acknowledgement/Funding

This study was supported by the Medical Faculty of the University of Regensburg (ReForM programme).

P3832Dantrolene reduces CaMKII-mediated arrhythmogenesis

Rationale

In atrial and ventricular rhythm disorders, an increased diastolic sarcoplasmatic reticulum (SR) calcium leak can induce a depolarizing transient inward current, serving as a trigger for cellular arrhythmias. Dantrolene has been shown to also stabilize the cardiac ryanodine receptor. However, the detailed mechanism of the mode of action remains unknown. This study aims to investigate the effects of dantrolene on calcium/calmodulin-dependent kinase II (CaMKII) mediated arrhythmogenesis.

Methods and results

Right atrial cardiomyocytes (CM) were isolated from patients with atrial fibrillation. To investigate SR Ca2+ leak, measurements of diastolic SR Ca2+ sparks were performed by confocal microscopy using Fluo-4 AM. Dantrolene (10 μmol/l) potently reduced Ca2+-spark-frequency (CaSpF) by 90±26% (p<0.05, n=21 cells dantrolene vs. 19 cells control) leading to a reduction of the calculated diastolic SR-Ca2+-leak by 91±31% (p<0.05, n=21 vs. 19). Interestingly, CaMKII-inhibition using Autocamtide-2-Related Inhibitory Peptide (AIP) did not further reduced SR Ca2+ leak compared to dantrolene alone in human cardiomyocytes. This observation may suggest (secondary) inhibitory effects of dantrolene on CaMKII. To elucidate the role of CaMKII in dantrolene-mediated antiarrhythmic effects, we investigated atrial CM from mice overexpressing CaMKII (TG) and respective wildtype controls (WT). CaSpF and SR Ca2+ leak were reduced by dantrolene in both TG and WT mice (p<0.005, TG: dantrolene vs. vehicle n=132 vs 127 cells (9 mice); WT: dantrolene vs. vehicle n=61 vs 61 cells (5 mice)). However, proarrhythmogenic Ca2+ waves were only significantly reduced by dantrolene in TG mice (p<0.05, TG: dantrolene vs. vehicle 10.8% vs. 26.2%, n=154 vs 164 cells). Correspondingly, the incidence of delayed afterdepolarizations (DADs) in TG cells was significantly diminished by dantrolene (p<0.05, TG: dantrolene vs. vehicle 1/14 vs. 9/15 cells, n=5 mice). In contrast, DADs were not reduced by dantrolene in WT cells without increased CaMKII activity (p=n.s., WT: dantrolene vs vehicle 3/16 vs 2/13 cells, n=5 mice). In preliminary in vivo experiments, intraperitoneal injection of 40 mg/kg body weight dantrolene reduced the inducibility of arrhythmias by ventricular burst stimulation in CaMKII TG mice compared to vehicle (dantrolene 0/2 mice vs. vehicle 2/2 mice, p<0.05 Chi-Square).

Conclusion

Dantrolene beneficially altered Ca2+ homeostasis in human AF CM and murine CM. Dantrolene seems to exert its antiarrhythmic potential in a CaMKII-dependent manner. Thus, dantrolene as an already clinically approved compound might be a potential antiarrhythmic drug that merits clinical investigation.

Acknowledgement/Funding

Deutsche Forschungsgemeinschaft (MA 1981/5-1 and 7-1 to LSM). Marga und Walter Boll-Stiftung (SS).

Immediate fullweightbearing after tarsometatarsal arthrodesis for hallux valgus correction--Does it increase the complication rate?

BACKGROUND

The arthrodesis of the first tarsometatarsal joint has a high correction potential in the treatment of hallux valgus deformity. Compared to distal correction procedures, a pseudarthrosis rate of 12-20% is quoted, however. In a prospective study the results of two different treatment procedures after correction arthrodesis were compared.

METHODS

In 17 cases the patients were mobilised with a short arthrodeses shoe with floor contact (NWB group) and in 17 cases in a short arthrodeses shoe with immediate fullweightbearing (FWB group). Clinical and radiological evaluation was done preoperatively, six weeks and one year postoperatively, including visual analogue pain scale and AOFAS score pre- and one year postoperatively.

RESULTS

There was no increased complication rate in the group with FWB group. The patients in the FWB group were significantly earlier fit for work.

CONCLUSION

Immediate fullweightbearing after TMT I arthrodesis using a plantar plate should be established as a standard posttreatment.

[Orthopaedic Treatment for Patients with Myelomeningocele]

BACKGROUND

Due to prenatal diagnostic and folic acid prophylaxis less children with myelomeningocele are now being born. But they become older and need increasingly more orthopaedic care. The orthopaedic care is aimed at the improvement or the preservation of function.

METHOD

In this review the current knowledge from the literature and our approach are presented. This is done in the context of the functional aspects within certain periods of life. Treatment Concept: In the first two years of life, the mobility of MMC children is supported by physiotherapy and orthoses irrespective of the level of the lesion. Afterwards, the optimal orthoses are chosen depending on the muscle power, emerging bone deformities, associated CNS malformation, shunt revisions, obesity and limitations in perception as well as the child's motivation. At school age, it is paramount to encourage independence. Orthotic treatment should be continued as long as the children benefit from it. Orthopaedic operations serve the orthosis fitting and the avoidance of pressure sores. Pathological fractures are common. They should be rapidly recognised in order to avoid further bony deformities.

CONCLUSION

The aim of any orthopaedic treatment consists of the avoidance of musculoskeletal deformities in order to support the patient's self employment.

[Ankle arthrodesis with an posterolateral approach using a polyaxial angle stable Talarlock® plate]

OBJECTIVE

Safe arthrodesis of the ankle as well as load carrying capacity free of pain.

INDICATION

Painful arthritis of the ankle joint occurring idiopathic or posttraumatic, resulting from rheumatoid arthritis or neuromuscular diseases. Extensive bony defects in varus or valgus ankle deformities and after failed prosthesis. Complex hindfoot deformities in neurological disease, paralysis and instabilities. Joint destruction after infection.

CONTRAINDICATIONS

Active osteitis, extensive skin ulcers in the approach area, periphery artery occlusive disease.

SURGICAL TECHNIQUE

Posterolateral skin incision. Sparing cartilage resection. Penetrating sclerosis zones. Reorientating anatomic positioning of the talus thereby correcting axis deformities. Talarlock(®) plate positioning and tibiotalar arthrodesis.

POSTOPERATIVE MANAGEMENT

Full weight bearing in an arthodesis boot for 6 weeks. After bone grafting partial weight bearing (20 kg) in an arthrodesis boot for 8 weeks. Full weight bearing after 10weeks.

RESULTS

Ten patients were operated on using this procedure. The follow-up time was 1 year. There were no complications requiring further surgical procedures. Ankle fusion and a good clinical outcome could be achieved in all cases.

Comparative study of Lapidus bunionectomy using different osteosynthesis methods

The treatment of hallux valgus in patients with pathology of the first tarsometatarsal (TMT I) joint by fusion is an established procedure. Multiple osteosynthesis methods for the fixation of the TMT I joint are available. In comparison to the distal procedures the Lapidus bunionectomy is associated with a pseudarthrosis rate of up to 12% [9-11]. We present results after TMT-I arthrodesis using an interfragmentary screw and a plantar plate compared with an interfragmentary screw and a dorsomedial locking plate. Clinical and radiological examinations were performed preoperatively, six weeks and one year postoperatively. The AOFAS (American Orthopaedic Foot and Ankle Society) score and Visual Analogue Pain Scale (VAS) were evaluated preoperatively and 12 months after surgery. We observed a significantly increased rate of undesirable effects in mediodorsal plate positioning.

Is it feasible to rely on intraoperative X ray in correcting hallux valgus?

BACKGROUND

The aim of the study was to prove whether the intraoperatively taken fluoroscopy pictures compared to the X rays taken 8 weeks and 3 months postoperatively picture the achieved correction reliably.

METHOD

In a prospective study, the pre- and postoperative standing foot X rays as well as the intraoperatively taken fluoroscopy pictures of 31 patients were analysed. The intermetatarsal angle (IMA) and the hallux valgus angle (HVA) were measured. In all cases, a tarso-metatarsal joint I arthrodesis combined with a distal soft tissue release was performed. The mean age was 54 (17-73) years.

RESULTS

There was no significant difference between the measured angles in intraoperative fluoroscopy and standing X rays postoperatively taken.

CONCLUSIONS

Despite the consideration that fluoroscopic pictures lack the loading criteria, we found reliable results in IMA and HVA.

Posteroplantar release for congenital clubfoot in children younger than 1 year

One hundred thirty-three resistant congenital clubfeet in 93 patients between 3 and 10 months of age were operated on using a standardized posteroplantar release. Clinical and radiographic assessments were done with a mean followup of 7 years 4 months (range, 3-12 years). Using the McKay score, 79.7% of the surgically treated clubfeet were classified as having a good or excellent result. Three patients had relapse of their clubfoot that required additional surgery. Seventeen feet in 15 patients had residual forefoot adduction at the time of followup. The radiographs showed that the early posteroplantar release led to sufficient hindfoot correction in all but the three patients who had relapse of the clubfoot. With this standardized surgical treatment, satisfactory results can be achieved in most patients younger than 1 year with congenital clubfoot. However, in patients with persistent talonavicular subluxation after conservative treatment, an additional talonavicular release combined with the posteroplantar release is recommended.

Clinical, endocrinological and radiography features in a child with McCune-Albright syndrome and pituitary adenoma

McCune-Albright syndrome is a rare syndrome presenting with polyostotic dysplasia, cafe-au-lait spots and multiple endocrinopathies that is very often combined with precocious puberty. We examined the clinical, endocrinological and radiological features in a boy with McCune-Albright syndrome and pituitary adenoma. X-rays, magnetic resonance (MRI) scan, whole body scintigraphy, single photon emission computer tomography (SPECT) and 3D-reconstruction from bone SPECT was performed to evaluate clinical improvement after treatment with sandostatin and pamidronic acid. After a six-month period of treatment with sandostatin and pamidronate, bone scintigraphy revealed significantly reduced activity. Treatment with bromocriptine and methimazole led to normalization of prolactin and thyroid hormone levels. Mobility of the patient improved. A significant improvement as a result of treatment with sandostatin and pamidronic acid was found in this patient with generalized fibrous dysplasia. So far, this condition has been treated with pamidronate only in adults, but severely affected children also benefit from this treatment regimen.

Substitution of tibial bony defects with allogeneic and autogeneic cancellous bone: encouraging preliminary results in 18 knee replacements

Eighteen knee replacements in 15 patients with severe gonarthritis or loosening of total knee arthroplasty (TKA) requiring bone grafting for bony deficiencies were studied before and after operation. The average follow-up was 2.4 years. Fifteen knees showed satisfactory clinical and radiographic results of the integration of the bone grafts. The Hospital for Special Surgery knee score improved from an average of 39 points preoperatively to 83 points at the most recent follow-up examination. Two of 3 knees with loosening of the tibial component required revision. These results are encouraging. Success depends as much on rigid fixation of the grafted bone and protected weight-bearing as on rigid, micromotion-preventing fixation of the tibial component.

Biomechanical and densitometric bone properties after callus distraction in sheep

Assessment of biomechanical stability of diaphyseal bone lengthened by callus distraction is an unsolved problem. A middiaphyseal corticotomy was performed in the left tibia of 24 sheep. After 7 days, callus distraction was begun at a rate of 0.5 mm every 12 hours for 30 days using a standard unilateral fixator system. Animals were euthanized 4, 8, or 12 weeks after the end of distraction. The lengthened tibia and the contralateral control tibia from each animal were evaluated by radiographic, densitometric (dual energy xray absorptiometry, quantitative computed tomography), and biomechanical (axial compression testing, torsion testing to failure) methods. The bone mineral density and maximum torque for the lengthened tibia were significantly greater in the 8-week group than in the 4-week group. However, the values in the 12-week group were significantly smaller than in the 8-week group. In the lengthened tibias, there was a correlation between the maximum torque and the bone mineral density, and between the maximum torque and the bone density. Bone density measurements are useful prognosticators for the safe removal of external fixators after leg lengthening procedures. By using these methods, clinical fractures after leg lengthening could be avoided in the future.