Post-operative cardiac function generally is monitored by electrocardiography, invasive measurement of blood pressure, and determination of hemodynamic variables, such as pulmonary pressures and cardiac output with a Swan-Ganz catheter. In recent years, transesophageal echocardiography has been introduced into clinical use, but it is not a popular method of monitoring for various reasons, including the difficulty of application to unconscious post-operative patients. Since 1991, we have been developing a small implantable echocardiography probe. This probe was tested in 15 patients who underwent open heart surgery for severe left ventricular hypofunction, and its clinical utility was demonstrated. No deaths occurred in this series. The implantable echocardiography probe allowed post-operative cardiac function to be monitored in real-time. The ejection fraction, the cardiac output, the status of valves after valvuloplasty, the presence of cardiac tamponade, and other variables could be assessed. The echocardiography probe can be positioned at any site where specific information is desired during surgery. It can be inserted as easily as a pericardial drain tube and is removed in the same manner when no longer necessary. This probe has the potential to be useful for monitoring patients on assisted circulation after cardiac surgery.

Assisted Circulation↗

PubMedDate not supplied

Feasibility study of vascular-endoscopic valvuloplasty. Using a laser and flexible endoscope.

Percutaneous balloon valvuloplasty is generally accepted, but post procedural complications limit its efficacy and reduce long-term success. To eliminate these risks, the authors explored the feasibility of cardioscopy guided percutaneous laser valvuloplasty in an experimental setting. The combined working model consisted of a separate balloon tipped thin fiber optic endoscope, laser balloon catheter, and a Nd-YAG laser transmitter. A porcine pulmonary valve was used as our in vivo target of laser ablation in a beating heart. Under general anesthesia, the endoscopic catheter is delivered into the pulmonary valve area through either the internal jugular or femoral vein under fluoroscopy. Positioning the pulmonary apparatus coaxial to the endoscopic visual field by manipulation of the catheter allowed for targeting and ablation of the commissure of the pulmonary valve under endoscopic view through the balloon filled with saline solution. The ablation energy was 15-30 W, 0.5-1.0 sec, and 2,000-3,000 J total. The animal was then killed and histopathologic study of the ablated area was done. The commissure of the pulmonary valve was smoothly ablated in 4 cases, and the entire ablation procedure was successfully witnessed through endoscopy. The authors encountered some difficulty in laser targeting, limitations to the endoscopic field of vision, and difficulty in holding the position of the apparatus in the beating heart. These are the barriers to overcome for future clinical application of this procedure. However, these results indicate the clear possibility of future use of cardioscopy guided percutaneous laser valvuloplasty in a clinical setting.

Animals↗

PubMedDate not supplied

A single skeletal muscle powered ventricle that assists both systemic and pulmonary circulations.

Extraaortic counterpulsation using skeletal muscle powered ventricles (SMPVs) has been studied mainly for the purpose of assisting the systemic circulation. The purpose of this study was to investigate the possibility of assisting both the systemic and pulmonary circulations using a single SMPV. An SMPV that counterpulses the systemic circulation is placed beside the right atrium (RA) or the right ventricle (RV), the former after procedures such as a Fontan operation, and the latter in cases of biventricular failure. Because the SMPV dilates passively during cardiac systole, it is designed to press the RA or the RV directly from outside. This study is a preliminary report, and only the ability of a specially constructed SMPV to dilate was assessed. Using seven dogs with heart failure, the SMPV dilated with an internal pressure of 88 mmHg and 1.0 cm, while the volume inside increased by 10.8 ml. From these results, it is suggested that the SMPV has enough dilating power to press the RA or to assist the RV while counterpulsing the systemic circulation.

Animals↗

PubMedDate not supplied

A new endo aortic occlusion balloon for limited access cardiac surgery: development and clinical evaluation.

In recent years, minimally invasive cardiac surgery (MICS), or limited access cardiac surgery, has been presented as a promising operative procedure. We developed a new balloon device that is inserted directly into the ascending aorta to stop the heart during limited access cardiac surgery. The balloon has a three lumen structure: balloon lumen port, cardioplegia/vent lumen port, and aortic root lumen port. This direct EAC balloon catheter, designed to be inserted directly into the ascending aorta, is different from the Heartport system. The Heartport EAC balloon catheter is inserted into the aorta via an artery in the lower limb, making lower limb arterial disease a key concern. Our Direct Endo Aortic Clamp (EAC) balloon overcomes this problem. The device was clinically used in seven cardiac cases. All patients were discharged within 5 postoperative days, confirming the utility of the device.

Aorta↗

PubMedDate not supplied

A durable, non power consumptive, simple seal for rotary blood pumps.

One of the key technologic requirements for rotary blood pumps is the sealing of the motor shaft. A mechanical seal, a journal bearing, magnetic coupling, and magnetic suspension have been developed, but they have drawbacks such as wear, thrombus formation, and power consumption. A magnetic fluid seal was developed for an axial flow pump. A magnetic fluid seal is durable, simple, and non power consumptive. Long-term experiments and finite element modeling (FEM) analyses confirmed these advantages. The seal body was composed of a Ned-Fe magnet and two pole pieces; the seal was formed by injecting ferrofluid into the gap (50 microm) between the pole pieces and the motor shaft. To contain the ferrofluid in the seal and to minimize the possibility of ferrofluid making contact with blood, a shield with a small cavity was attached to the pole piece. While submerged in blood, the sealing pressure of the seal was measured and found to be 188 mm Hg with ferrofluid LS-40 (saturated magnetization, 24.3 kA/m) at a motor speed of 10,000 rpm and 225 mm Hg under static conditions. The magnetic fluid seals performed perfectly at a pressure of 100 mm Hg for 594 + days in a static condition, and 51, 39+, and 34+ days at a motor speed of 8,000 rpm. FEM analyses indicated a theoretical sealing pressure of 260 mm Hg. The state of the magnetic fluid in the seal in water was observed with a microscope. Neither splashing of magnetic fluid nor mixing of the magnetic fluid and water was observed. The specially designed magnetic fluid seal for keeping liquids out is useful for axial flow blood pumps. The magnetic fluid seal was incorporated into an intracardiac axial flow pump.

Heart-Assist Devices↗