Transvascular closure of single and multiple muscular ventricular septal defects in neonates and infants < 20 kg.

PURPOSE: While surgical closure of ventricular septal defects (VSD) is still the gold standard, we review our experience with the interventional closure of single and multiple muscular VSD in newborns and infants under 20 kg. METHOD: Between 2004 and 2012 transcatheter closure of ten Swiss cheese VSD, six single muscular and one apical VSD was attempted in 17 patients between 10 days and 7.3 years of age and with a bodyweight ranging from 2.2 to 19 kg. Seven patients had had a significant shunt after cardiac surgery, five patients a shunt induced congestive heart failure and in five patients postponement of surgery was intended. RESULTS: A total of 20 devices was successfully implanted in 15 of 17 (88%) patients, reducing the interventricular shunt and improving the haemodynamic situation in 14 patients. An acute AV-block led to immediate removal of the device in a patient of 2.2 kg. One Amplatzer muscular VSD occluder could not be delivered due to the sharp bending of the delivery sheath in 2004. Three patients died during follow-up not related to the intervention. Re-intervention was necessary in one patient with Swiss cheese VSD. CONCLUSION: Interventional closure of muscular VSD is possible in newborns and infants and presents an eligible treatment option. New occlusion systems with miniaturized introducer sheaths of 4-6 French have extended the spectrum of treatable lesions. An individual and interdisciplinary risk-benefit stratification is required to choose from surgical, interventional, or combined strategies.

Alpha1-adrenergic stress induces downregulation of Na+/Ca2+ exchanger in myocardial preparations from rabbits at physiological preload.

Alpha1-adrenergic stimulation and mechanical load are considered crucial for the expression of sarcolemmal Na+/Ca2+ exchanger (NCX1). However, the interaction between these processes is unknown. We investigated electrically stimulated (1 Hz, 1.75 mmol/L Ca2+) rabbit ventricular trabeculae at physiological preload under stimulation by the selective alpha1-agonist phenylephrine (PE, 10 micromol/L). Using quantitative real-time PCR, downregulation of mRNA to 76.5% (p<0.05) was found, while B-type natriuretic peptide (BNP) was increased to 569.5% (p<0.05) compared to control. These changes were abolished in the presence of both the alpha1-blocker prazosin (13 micromol/L) and the PKC inhibitor GF109203X (1 micromol/L). Furthermore, no changes in NCX mRNA levels under the influence of PE were found in unstretched trabeculae or in unstretched isolated rabbit myocytes (24 h), while BNP was increased in both preparations. In addition, since the alpha1-adrenergic effect could be Ca2+-dependent we tested increased extracellular Ca2+ (3.0 mmol/L) in stretched trabeculae and found downregulation of NCX1 to 75.2% (p<0.05). alpha1-stimulation decreases NCX1 mRNA in rabbit myocardium via PKC. This is critically load-dependent and may be mediated by changes in [Ca2+]. In hypertrophy and heart failure, distinct phenotypes with respect to NCX1 expression may result from the interaction between mechanical load and alpha1-adrenergic stimulation.

High intracellular Na+ preserves myocardial function at low heart rates in isolated myocardium from failing hearts.

We investigated the hypothesis that increased intracellular [Na+]i in heart failure contributes to preservation of SR Ca2+ load which may become particularly evident at slow heart rates. [Na+]i in SBFI-loaded myocytes from rabbits with pacing-induced heart failure (PHF) was significantly higher at each frequency as compared to Sham-operated animals. Furthermore, PHF rabbits demonstrated reduced SR Ca2+-ATPase protein levels (-37%, p < 0.04) but unchanged Na+/Ca2+ exchanger protein levels. At 0.25 Hz, isometric force was similar in cardiac trabeculae from PHF rabbits as compared to control (PHF, 3.6+/-1.3; Sham, 4.4+/-0.6 mN/mm2). Rapid cooling contractures (RCCs) were unchanged indicating preserved SR Ca2+ load at this frequency. In Sham, isometric twitch force increased with rising frequencies to 29.0+/-2.8 mN/mm2 at 3.0 Hz (p < 0.05) as compared to 0.25 Hz. RCCs showed a parallel increase by 186+/-47% (p < 0.01). In PHF, frequency-dependent increase in force (15.8+/-4.7 mN/mm2 at 3.0 Hz) and RCCs (increase by 70+/-40%) were significantly blunted. Thus, in PHF in rabbits SR Ca2+ load is preserved at low frequencies despite decreased SR Ca2+-ATPase expression. This may result from [Na+]i-dependent changes in Na+/Ca2+ exchanger activity.