In the initial published experience [12], hospital discharge has occurred in as little as 10 days but has generally been between 14 and 20 days (median of 17 days). Patients were anticoagulated with aspirin (100 mg day⁻¹) and warfarin with a goal to achieve an international normalized ratio (INR) value of 2.5–3.0.

Given that the surgical procedure is not requiring sternotomy, prior cardiac operations [coronary artery bypass grafting (CABG), valve surgery, or Dor procedure] are not considered at higher risk compared to previously not-operated chest.

Patients were selected as on the cardiac transplant waiting list with a predicted waiting time >6 months and in the New York Heart Association (NYHA) class IIIB or IVA despite appropriate treatment with diuretics, angiotensin-converting enzyme (ACE) inhibitor, or angiotensin receptor blockade and beta blocker as tolerate, ambulatory, not inotropic dependent, and with limitations in the activities of daily living (INTERMACS classes IV–VII). Exclusion criteria included acute decompensated heart failure, acute postcardiotomy heart failure, existing thrombus in the left atrium, mechanical mitral or aortic valve, significant aortic regurgitation, severe depressed renal function (serum creatinine > 2.5 mg dl/1), elevated liver enzymes >2 times the upper limit of normal, and contraindication to anticoagulation.

Medication in the implanted patients was supposed to be appropriate for end-stage heart failure with the main differences with respect to the general MCS population that the treated patients should still be treated with beta blockers, ACE inhibitors or angiotensin receptor blockers, and less frequently treated with inotropic agents.

Acute and chronic hemodynamic effects for partial mechanical support 24 h after surgery were reported [12] as estimated pump flow was with a range of 2.3–3.5 l min/1. With this additional pump output, hemodynamic improvements assessed at 24 h following surgery included an increase of the total cardiac index (CI) (from 2.0 ±0.4 to 3.3 ±0.9 l min/1 m², p < 0.001) and the decrease of the pulmonary systolic pressure (from 55 ±15 to 53 ±14 mmHg, p = 0.34) and pulmonary diastolic pressure (from 27 ±9 to 21 ±5 mmHg, p = 0.002). At an average follow-up of 9.5 ±5.5 weeks, sustained improvements in all parameters, including clinically and statistically significant reductions in pulmonary and arterial resistances, are found.

Given the baseline characteristics for patients entering this trial, severe adverse events (SAEs) were expected and have been similar in nature to those reported for LVADs. However, at this initial point, it is encouraging that the frequency of SAEs experienced by the Synergy patients, particularly in the first 30 days following surgery, appears to occur at a significantly reduced rate to those reported for other LVADs. Reported SAEs have included bleeding requiring transfusion or return to the operating room, infections (including sepsis from any cause, driveline or pocket infections, and infections not necessarily related to the device), and strokes. Overall, including all reports for Synergy patients, SAEs during the first 30 days occurred at approximately half the rate as that reported for other MCS [8]. The Achilles’s heel of this technology was the pump thrombosis or exchange for any reason, which accounted for about a third of the events reported after the first 30 days of support.

The comparison of the CircuLite patients to those implanted with other MCS bridge-to-transplant study is very interesting. The patients had similar baseline demographic characteristics and, most surprisingly, almost identical hemodynamic profiles and end-organ function. The major difference was that these baseline hemodynamic characteristics were observed in the Synergy patients with greater use of standard heart failure therapy (i.e., more ACE inhibitor, angiotensin receptor blockade (ARB), and beta blocker use) and less inotropic support than in regular MCS population. This is consistent with the notion that development of intolerance to standard heart failure medical therapy (which usually manifests as a gradual reduction of drug dosing by the treating clinician), along with worsening symptoms, may identify patients who are approaching a stage where early intervention with a device such as the Synergy device should be considered. Early clinical experiences [13] supported the hypothesis that, when applied prior to significant end-organ dysfunction and becoming inotrope dependent, even in the elderly and more fragile population, partial support with the Synergy device can indeed provide adequatesupport and interrupt the progressive hemodynamic deterioration characteristic of severe heart failure.

The other important hypothesized feature of the Synergy device was that its lesser invasive nature (small size, no sternotomy, and no cardiopulmonary bypass) would be associated with less adverse events in the short and long term.

One more interesting finding of CircuLite use in the clinical setting regards the development of right-heart failure: interestingly, preoperative pulmonary artery systolic pressures have ranged between 26 and 90 mmHg, indicating a wide range of right ventricular function at baseline. It could be argued that, in contrast to a full-support VAD, which can abruptly increase cardiac output to 6–7 l/min and acutely overload the right ventricle, the acute increase in cardiac output resulting from the Synergy system is of the order of only 1.0–1.5 l/min. Thus, it could be that concerns about development of right- heart failure will be less with a partial-support device.

Unfortunately the CircuLite Synergy® device in the clinical setting proved to have too many device-related adverse events, and its clinical experience has been withheld to allow a full reengineering of its main components, although it was able to prove the concept that partial support is sufficient to allow improvement in hemodynamics and QoL in the INTERMACS 4–7 end-stage heart failure population, sparing the patients of major surgery and allowing even the most fragile patients to approach the MCS world.