No abstract

The electrical parameter used to define defibrillation strength is energy. Peak current, however, may more accurately reflect the field quantities (i.e., electric field strength and current density) that mediate defibrillation and therefore should be a better clinical descriptor of threshold than energy. Though transthoracic impedance is a major determinant of energy-based threshold and is sensitive to operator-dependent changes in impedance (electrode-subject interface), an ideal threshold descriptor should be invariant with respect to these changes in impedance. We therefore compared the relative invariance of energy-and current-based thresholds when transthoracic impedance was altered by one of two methods: (a) change in electrode size (protocol A) or (b) change in electrode force (protocol B). In protocol A, impedance was altered in each dog by a mean of 95%. Energy thresholds determined at both low and high impedance were 44±21 J (mean±SD) and 105±35 J, respectively, P < 0.0001. In contrast, peak current (A) thresholds were independent of transthoracic impedance, 22±5 A (low impedance) vs. 24±6 A (high impedance), P = NS. Energy and current thresholds showed a similar relationship for animals tested in protocol B. Therefore, current-based thresholds, in contrast to energy thresholds are independent of operator-dependent variables of transthoracic impedance and are invariant for a given animal. These results suggest that redefining defibrillation threshold in terms of peak current rather than energy provides a superior method of defibrillation.

Heart failure impacts a multitude of individuals each year. Treatment is based on the progression of the disease and severity of symptoms. Cardiac transplant is the gold standard treatment of advanced heart failure, although the availability of organs limits the number of transplants received each year. Postoperative care and monitoring for cardiac transplant is complex and requires specialized nurses and providers at transplant centers for successful outcomes. This article outlines cardiac transplant from preoperative care through transplant, as well as posttransplant monitoring and care including discharge. Special attention is focused on management in the intensive care unit setting and potential complications that can occur in the immediate postoperative period. Interventions for potential complications are also highlighted.

Heart failure is a progressive and fatal disease impacting millions of American each year. Divided into stages, heart failure presents with progressive symptoms requiring a wide range of medical treatments. Treatments include diet and lifestyle changes, medications, electrical therapies (defibrillator and/or cardiac resynchronization therapy), as well as mechanical circulatory support. Cardiac transplant is the gold standard treatment of heart failure, although the availability of donors limits the utility of a cardiac transplant. This article outlines heart failure treatments and the indications, contraindications, and pretransplant evaluation for a cardiac transplant. Information on the allocation of donor hearts and donor characteristics is also included for the reader.