Honeycomb-structured metasurfaces for the adaptive nesting of endothelial cells under hemodynamic loads

The thrombogenicity of artificial materials comprising ventricular assist devices (VADs) limits their long-term integration in the human body.

Importance of preoperative liver function as a predictor of survival in patients supported with Thoratec ventricular assist devices as a bridge to transplantation

Patient selection is crucial for the success of ventricular assist devices as a bridge to heart transplantation.

PURPOSE

The objective of this study was to identify preoperative markers for survival and end-organ recovery in patients having a ventricular assist device.

METHODS

A retrospective study was performed on 32 severely ill patients with end-stage cardiac failure being mechanically bridged to heart transplantation with the Thoratec Ventricular Assist Device System (Thoratec Laboratories Corporation, Pleasanton, Calif) in a single center between 1984 and 1995. The preoperative cardiac index averaged 1.6 L/min per square meter with a pulmonary capillary wedge pressure of 29 mm Hg. Because of a high incidence of hepatic or renal dysfunction, or both (total bilirubin: 3.5 +/- 6.2 mg/dL; creatinine: 2.0 +/- 1.3 mg/dL), biventricular support was used in most patients (28/32). A total of 30 preoperative and 4 perioperative variables were evaluated for their association with survival and liver recovery.

RESULTS

Nineteen patients (59.4%) survived to transplantation and 13 died. All 19 patients undergoing transplantation were discharged alive with a 1-year survival of 94.4%. All patients without liver recovery died of multiorgan failure. Direct and indirect bilirubin measurements were the only significant predictors for survival to discharge (P = .036, .045); all other factors failed to show significance. As direct bilirubin levels increased (normal range, 3 times normal, and >3 times normal), patient survival decreased (82 %, 56%, and 33 %, respectively). In addition, bilirubin and liver enzyme levels before insertion of the assist device were significantly associated with liver recovery during support with the device.

CONCLUSION

In our patient population with ventricular assist devices, liver function is the most predictive factor of patient survival in bridging to transplantation.

Circulatory support with shock due to acute myocardial infarction

Cardiogenic shock after acute myocardial infarction develops according to the amount of lost myocardium, function of remote myocardium, and the phenomenon of infarct expansion. Patients treated with mechanical support alone, without additional measures, have a mortality rate of 80%, the same as patients treated medically. Emergency angioplasty and emergency coronary artery bypass grafting can reduce mortality in certain subsets of patients to 40%. Patients with more severe shock and secondary organ dysfunction may be treated with mechanical bridging to transplantation with survival rates varying between 45% and 76%. Percutaneous support systems may be used to resuscitate a patient or to temporize, allowing time to perform diagnostic studies to determine if the patient is suitable for revascularization or heart transplantation. Intravenous enoximone may improve cardiac function as well and thus allow better decision making for further therapy.

Wearable air supply for pneumatic artificial hearts and ventricular assist devices

An experimental wearable air supply for pneumatic artificial hearts and ventricular assist devices has been built and tested. The unit eliminates the need for tethering to a large, stationery driver. The miniaturized air supply is designed for ambulatory patients with implanted pulsatile pneumatic total artificial hearts (TAH) or pneumatic left-ventricular assist devices (LVAD), to permit mobility in clinical and home settings. The device has major short-term utility as a supply for pneumatic TAH or VAD bridges in patients awaiting heart transplants. The system design for the wearable driver includes a novel, fast rotary compressor, driven by a brushless direct current (DC) motor to supply air to the ventricle through an electromagnetically actuated directional valve, all controlled by a microcomputer. Stroke volume from 0 to 200 cc; pulse rate from 60 to 160 bpm, and duty cycle from 33% to 50% are selected on a keyboard, and the selected or measured parameters can be shown on a liquid crystal display. For control of delivery from a single ventricular assist device, stroke volume is controlled by variation of compressor speed. In the wearable air supply for a TAH, a single compressor drives both ventricles alternately through a double-acting directional valve. Air volume delivered to the left ventricle is adjusted by variation of compressor speed, and air volume to the right ventricle by variation of ejection time. The effect on blood flow rate of the lower impedance to the right ventricle is compensated by provision of a two-stage compressor, in which a single stage drives the right ventricle, and both stages connected in parallel drive the left ventricle. The overall dimensions of the prototype air supply for driving either a TAH or LVAD are 4.5 by 7.8 by 4.5 inches, including an emergency battery with a duration of 15 to 30 min depending on load. The weight is presently 5.5 lb, but this will be reduced in a production design and for a dedicated LVAD air supply. The size and weight of a separately worn, rechargeable battery pack depend on the load and desired duration of operation.