The future of mechanical circulatory support

Surface modification of a titanium alloy with a phospholipid polymer prepared by a plasma-induced grafting technique to improve surface thromboresistance

To improve the thromboresistance of a titanium alloy (TiAl(6)V(4)) surface which is currently utilized in several ventricular assist devices (VADs), a plasma-induced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) was carried out and poly(MPC) (PMPC) chains were covalently attached onto a TiAl(6)V(4) surface by a plasma induced technique. Cleaned TiAl(6)V(4) surfaces were pretreated with H(2)O-vapor-plasma and silanated with 3-methacryloylpropyltrimethoxysilane (MPS). Next, a plasma-induced graft polymerization with MPC was performed after the surfaces were pretreated with Ar plasma. Surface compositions were verified by X-ray photoelectron spectroscopy (XPS). In vitro blood biocompatibility was evaluated by contacting the modified surfaces with ovine blood under continuous mixing. Bulk phase platelet activation was quantified by flow cytometric analysis, and surfaces were observed with scanning electron microscopy after blood contact. XPS data demonstrated successful modification of the TiAl(6)V(4) surfaces with PMPC as evidenced by increased N and P on modified surfaces. Platelet deposition was markedly reduced on the PMPC grafted surfaces and platelet activation in blood that contacted the PMPC-grafted samples was significantly reduced relative to the unmodified TiAl(6)V(4) and polystyrene control surfaces. Durability studies under continuously mixed water suggested no change in surface modification over a 1-month period. This modification strategy shows promise for further investigation as a means to reduce the thromboembolic risk associated with the metallic blood-contacting surfaces of VADs and other cardiovascular devices under development.

Systemic arterial waveform analysis and assessment of blood flow during extracorporeal circulation

BACKGROUND

The pressure recording analytical method (PRAM) is a method for real-time beat-to-beat quantification of peripheral blood flow based on the analysis of arterial waveform morphology. Since PRAM can be implemented in any conditions of flow, whether physiological or artificial, we assessed its accuracy in patients undergoing cardiac surgery during extracorporeal circulation (ECC), using the roller-pump device as the reference gold standard.

METHODS

We prospectively studied 32 patients undergoing elective coronary surgery. Flow values obtained by PRAM from the radial artery were compared with simultaneous values by thermodilution in physiological conditions of flow and with the roller-pump device readings during ECC.

RESULTS

Before and after ECC, the overall estimates of flow measured by PRAM closely agreed with thermodilution (mean difference 0.07 +/- 0.40 L/min). During ECC, PRAM estimates of flow also closely correlated with simultaneous pump readings (mean difference 0.11 +/- 0.33 L/min). At time of weaning from ECC, two patterns of hemodynamic adaptation were documented by PRAM following resumption of cardiac contraction: in most patients (n =26; 80%), cardiac output (CO) was stable (reduction < or = 10% compared to the steady ECC phase); six patients (20%) showed a fall in CO exceeding 10% and up to 38%.

CONCLUSIONS

PRAM provided accurate, continuous quantification of peripheral blood flow during each phase of cardiac surgery, including ECC, and allowed early recognition of patients with low CO during weaning from the pump.

Medical devices of the chest

Chest devices are encountered on a daily basis by almost all radiologists. A multitude of extrathoracic materials, from intravenous catheters to oxygen tubing and electrocardiographic leads, frequently overlie the chest, neck, and abdomen. Chest tubes, central venous catheters, endotracheal tubes, and feeding tubes are very common. Cardiac surgery involves the use of many sophisticated devices and procedures, ranging from valve replacement to repair of complex congenital anomalies. Coronary artery bypass surgery is no longer considered unusual, and in many large medical centers, ventricular assist devices and total artificial hearts are frequently encountered. Breast implants are visible at standard chest radiography, and many ancillary devices not intended for treatment of cardiac or thoracic diseases are visible on chest radiographs. New devices are constantly being introduced, but most of them are variations on a previous theme. Knowing the specific name of a device is not important. It is important to recognize the presence of a device and to have an understanding of its function, as well as to recognize the complications associated with its use.