Contemporary management and research directions in advanced heart failure: where are we going?

Novel role of transient receptor potential vanilloid 2 in the regulation of cardiac performance

Transient receptor potential cation channels have been implicated in the regulation of cardiovascular function, but only recently has our laboratory described the vanilloid-2 subtype (TRPV2) in the cardiomyocyte, though its exact mechanism of action has not yet been established. This study tests the hypothesis that TRPV2 plays an important role in regulating myocyte contractility under physiological conditions. Therefore, we measured cardiac and vascular function in wild-type and TRPV2(-/-) mice in vitro and in vivo and found that TRPV2 deletion resulted in a decrease in basal systolic and diastolic function without affecting loading conditions or vascular tone. TRPV2 stimulation with probenecid, a relatively selective TRPV2 agonist, caused an increase in both inotropy and lusitropy in wild-type mice that was blunted in TRPV2(-/-) mice. We examined the mechanism of TRPV2 inotropy/lusitropy in isolated myocytes and found that it modulates Ca(2+) transients and sarcoplasmic reticulum Ca(2+) loading. We show that the activity of this channel is necessary for normal cardiac function and that there is increased contractility in response to agonism of TRPV2 with probenecid.

[The chronic critically ill patient from the cardiologist's perspective]

In recent years the prognosis and survival of chronic and acute heart failure (HF) patients has been steadily improving; however, many patients develop advanced chronic HF which is characterized by worsening of symptoms, unplanned hospital admission due to acute decompensation, development of complications, such as life-threatening arrhythmia and shorter life span. Optimal medical therapy is supplemented by interventional cardiology, cardiovascular implantable electronic devices (CIEDs), minimally invasive valve replacement or repair, circulatory mechanical support and heart transplantation. Medical indications and informed consent are essential prerequisites for successfully implementing treatment goals. For patients who are incapable of decisions a legally defined surrogate decision-maker has the same right to refuse or request the withdrawal of treatment as the patient would have if the patient had decision-making capability. As the use of circulatory mechanical support becomes increasingly more prevalent, ethical issues are likely to arise at an increasing rate, as will social and legal ramifications. The concept of turning off an implanted device as death nears is challenging because of ethical and technical concerns. The same holds true for CIEDs. A palliative care approach is applicable to heart failure patients and is particularly relevant to those with advanced disease. Palliative care should be integrated as part of a team approach to comprehensive HF care and should not be reserved for those who are expected to die within days or weeks.

Calcium cycling proteins and heart failure: mechanisms and therapeutics

Ca2+-dependent signaling is highly regulated in cardiomyocytes and determines the force of cardiac muscle contraction. Ca2+ cycling refers to the release and reuptake of intracellular Ca2+ that drives muscle contraction and relaxation. In failing hearts, Ca2+ cycling is profoundly altered, resulting in impaired contractility and fatal cardiac arrhythmias. The key defects in Ca2+ cycling occur at the level of the sarcoplasmic reticulum (SR), a Ca2+ storage organelle in muscle. Defects in the regulation of Ca2+ cycling proteins including the ryanodine receptor 2, cardiac (RyR2)/Ca2+ release channel macromolecular complexes and the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a)/phospholamban complex contribute to heart failure. RyR2s are oxidized, nitrosylated, and PKA hyperphosphorylated, resulting in "leaky" channels in failing hearts. These leaky RyR2s contribute to depletion of Ca2+ from the SR, and the leaking Ca2+ depolarizes cardiomyocytes and triggers fatal arrhythmias. SERCA2a is downregulated and phospholamban is hypophosphorylated in failing hearts, resulting in impaired SR Ca2+ reuptake that conspires with leaky RyR2 to deplete SR Ca2+. Two new therapeutic strategies for heart failure (HF) are now being tested in clinical trials: (a) fixing the leak in RyR2 channels with a novel class of Ca2+-release channel stabilizers called Rycals and (b) increasing expression of SERCA2a to improve SR Ca2+ reuptake with viral-mediated gene therapy. There are many potential opportunities for additional mechanism-based therapeutics involving the machinery that regulates Ca2+ cycling in the heart.