[Heart and combined heart-lung transplantation. Indications, chances and risks]

Orthotopic heart transplantation (HTX) is nowadays the worldwide accepted gold standard for the treatment of terminal heart failure. The main indications for HTX are non-ischemic dilatative (54%) and ischemic (37%) heart failure. In the acute phase after HTX the survival rate is approximately 90%. Good short and long-term results with survival rates ranging from 81% after 1 year to more than 50% after 11 years demonstrate that there is currently no real treatment alternative to HTX for treatment of end-stage heart failure. In the case of irreversible pulmonary hypertension in combination with end-stage heart failure or complex congenital heart syndromes, a combined heart and lung transplantation (HLTX) is necessary. Compared with HTX the short-term survival of HLTX is reduced, mostly for technical reasons. Improved long-term results after HTX and HLTX are a result of highly specialized transplantation units and effective immunosuppression. However, a major problem is the shortage of organ donors in Germany and the resulting long waiting times for patients with frequently occurring blood groups of up to 10 months for transplantation. The consequence of the latter is the ever increasing number of implanted cardiac assist devices in patients not only as a bridge to transplant but also as destination therapy.

A modified technique for implantation of the HeartWare™ left ventricular assist device when using bivalirudin anticoagulation in patients with acute heparin-induced thrombocytopenia

In patients with acute heparin-induced thrombocytopenia (HIT) needing urgent cardiac surgery, bivalirudin is recommended as a first-line strategy for intraoperative anticoagulation. However, due to the unique elimination process of bivalirudin, careful adjustment of the perfusion and surgical strategy is mandatory as blood stasis in the circuit or prolonged interruption of areas or compartments containing blood from the systemic circulation may result in thrombus formation. We report here a modified surgical strategy for the implantation of the HeartWare™ left ventricular assist device, which avoids prolonged disconnection of the blood-filled device from the systemic blood flow, so that bivalirudin can be safely used as anticoagulant.

Regulation of cyclic adenosine monophosphate release by selective β2-adrenergic receptor stimulation in human terminal failing myocardium before and after ventricular assist device support

BACKGROUND

Response to catecholamines is blunted in terminal heart failure due to β-receptor downregulation and uncoupling from adenylyl cyclase (AC). Improved myocardial responsiveness to catecholamines after ventricular assist device (VAD) support is associated with upregulation of β1-adrenergic receptors (β1-ARs). Little is known about the regulation of AC and β2-AR coupling after VAD; moreover β2-AR stimulation during VAD was claimed to induce myocardial recovery.

METHODS

We analyzed in VAD-supported human myocardium the regulation of AC activity upon β1-AR and selective β2-AR stimulation in 8 non-failing hearts (NF) and 17 paired samples of VAD patients. AC messenger RNA was measured by TaqMan. AC was stimulated via β2-AR using clenbuterol (β2-AR agonist) and bisoprolol (β1-AR blocker). Organ bath experiments were done with trabeculae from both ventricles. Samples were stratified according to chronic or acute heart failure history.

RESULTS

Isoprenaline-induced AC activity was downregulated (p < 0.001) pre-VAD and increased significantly (p < 0.05) after unloading (mean ± standard deviation pmole/mg/min) in NF (47.9 ± 14.9), pre-VAD (24.35 ± 13.3), and post-VAD (50.04 ± 50.25). Forskolin stimulation revealed significant (p < 0.05) upregulation of AC activity during VAD, especially in acutely failing hearts (NF, 192.1 ± 68.7; pre-VAD, 191.1 ± 60.4; post-VAD, 281.5 ± 133). However, forskolin stimulation relative to isoprenaline-induced inotropy remained reduced before and after VAD compared with NF. The selective stimulation of β2-AR did not reveal influence of VAD support on β2-AR-AC coupling. Stimulation of ventricular trabeculae by > 100 μmole/liter clenbuterol revealed negative inotropic responses.

CONCLUSIONS

VAD does not influence β2-AR coupling to AC stimulation. Elevated response to catecholamines after VAD support is influenced by β1-AR upregulation and modulation of AC activity. Restoration of β-adrenergic responsiveness was restricted to acutely failing hearts.

Heart failure while on ventricular assist device support: a true clinical entity?

Ventricular assist devices (VADs) have become an established therapeutic option for patients with end-stage heart failure. The appearance of heart failure in VAD patients seems unexpected. Nevertheless, this phenomenon is not rare. We report six cases of VAD patients with clinical presentation of heart failure at different times after implantation and describe the mechanisms involved. The aetiology of this heart failure, like its clinical presentation, varies and has yet to be identified.

Recurrent thrombosis after mechanical circulatory support

The immediate complication after implantation of mechanical circulatory support (MCS) is more often bleeding than thromboembolic events. We report an unusual case of massive thrombus formation following systemic thrombolytic therapy which happened twice after implantation of MCS. Various mechanisms may contribute to this severe complication, but attention should be paid to patients who receive MCS after systemic thrombolysis because of the secondary hypercoagulability induced by this therapy.