Cardiac Autonomic Dysfunction in the Early Phase after Left Ventricular Assist Device Implant: Implications for Surgery and Follow-Up?

Improving Diuretic Response in Heart Failure by Implementing a Patient-Tailored Variability and Chronotherapy-Guided Algorithm

Heart failure is a major public health problem, which is associated with significant mortality, morbidity, and healthcare expenditures. A substantial amount of the morbidity is attributed to volume overload, for which loop diuretics are a mandatory treatment. However, the variability in response to diuretics and development of diuretic resistance adversely affect the clinical outcomes. Morevoer, there exists a marked intra- and inter-patient variability in response to diuretics that affects the clinical course and related adverse outcomes. In the present article, we review the mechanisms underlying the development of diuretic resistance. The role of the autonomic nervous system and chronobiology in the pathogenesis of congestive heart failure and response to therapy are also discussed. Establishing a novel model for overcoming diuretic resistance is presented based on a patient-tailored variability and chronotherapy-guided machine learning algorithm that comprises clinical, laboratory, and sensor-derived inputs, including inputs from pulmonary artery measurements. Inter- and intra-patient signatures of variabilities, alterations of biological clock, and autonomic nervous system responses are embedded into the algorithm; thus, it may enable a tailored dose regimen in a continuous manner that accommodates the highly dynamic complex system.

Loss of Pulsatility: Another Cause of Syncope in Patients with Left Ventricular Assist Devices

We report a case of a 55-year-old man who presented with recurrent syncope 15 months after HeartWare left ventricular assist device (LVAD) implantation and was found to have diminished LVAD flow and pulsatility on tilt table testing leading to severe orthostatic hypotension (OH). The prevalence of OH is common, but autonomic dysfunction leading to OH has not been well described in patients with chronic LVAD support. The diagnosis of OH in this setting is challenging due to the decreased pulsatility in the flow generated by LVADs, and tilt table testing can be useful in the evaluation of OH in these patients.

Circadian variation of motor current observed in fixed rotation speed continuous-flow left ventricular assist device support

The algorithm for the physiological control provided by left ventricular assist devices (LVADs) has been controversial. In particular, little is known about the physiological control algorithm (such as for achieving physiological circadian rhythms) in continuous-flow LVADs. To investigate the existence of circadian variation, we retrospectively evaluated the LVAD flow-correlated motor current of patients supported by continuous-flow LVADs. The motor current and the pump speed were collected from the external controller every 10 min after device implantation, and the data were divided for every 30-day period, which began on midnight on the first post-operative day. The subjects were 18 patients (mean age 37.7, mean body surface area 1.71 m(2) at the time of operation) with dilated cardiomyopathy or dilated phase of hypertrophic cardiomyopathy. As of August 1, 2013, the patients' median support duration was 889 days. The mean calculated dominant period of motor current variation was 24.0 h and the mean amplitude was 11.7 mA for the entire duration. The amplitude of the motor current circadian variation tended to be increased until around the fifth month. The motor current had a tendency to be relatively low during the night time and high during the day time. A significant difference was found between the night-time and day-time mean motor current for the entire duration (p < 0.05). In conclusion, the circadian variation of the motor current could be observed over long term in patients with fixed rotation speed continuous-flow LVAD support.