Ventricular chambers

Both ventricular outlets are verified using a fine pointed probe from each ventricular chamber into the respective aortic arch or pulmonary trunk. 

FIGURE 44.8 Typical prototype designs of total artificial hearts (a) pneumatically powered TAH. The right and left ventricular chambers, inflow and outflow valves, as well as the connector for the pneumatic line are visible in the photograph (b) electrically powered TAH. Shown are the external battery pack, transcutaneous energy transmission system (TETS) primary and secondary coils, implanted electronics, energy converter and the blood pumps, compliance chamber and the subcutaneous access port. (Courtesy of G. Rosenberg, Pennsylvania State University.)... 

SAGAWA I also disagree with Dr. Feigl. I don t see any reason why the word elastance should be used strictly as a passive property. Even the so-called passive property of muscle is quite active. It is very difficult to draw a sharp line between passive and active muscle. In addition, in engineering, the suffix ance is not used to represent a material property. Instead it represents a systems property. For example, the elastance of the balloon at a given volume is not a measure of the elasticity of the balloon material. Instead, the term elasticity, or modulus of volume elasticity, is used to describe the material property. So I think it s right to use the term elastance for the ventricular chamber regardless of its state of activation. 

Most of the finite element analysis hitherto conducted only consider uniform chamber pressure loading of the ventricles the shear and turbulent effects of the blood flow in the ventricular chambers are not dealt with. As far as the boundary conditions are concerned, isolated left ventricles and connected left and right ventricles have mostly been treated as radially deformable at the sites of the cardiac valves. 

RITMAN You mentioned that you fixed the base in space. Certainly all our information in the intact dog seems to indicate that the apex stays fixed. If that is the case, then the myocardium might, in a manner of speech, be pulled over the blood, as a sleeve might be, so you don t really have to postulate a pressure gradient within the ventricular chamber for the blood to move out into the aorta. 

Figure 6. Accuracy of DSR based estimates of ventricular chambers compared with direct water displacement of the plastic casts of the chambers. Data from (Hoffman and Ritman, submitted 1984a).

The thresholds of right and left ventricular pacing leads can be difficult to assess in ICDs that do not have separate programmability for each output. This is because the morphology change of the QRS complex on a single surface ECG rhythm strip can be very subtle when capture is lost in a ventricular chamber. Also, since many of the patients for which a CRT device has been implanted have a native left bundle branch block (LBBB) pattern on their surface ECG, the RV capture and native QRS complexes can look remarkably similar. 

One of the keys to understanding ventricular capture thresholds in CRT ICDs is to first appreciate how a QRS complex should appear on a surface EGG when one, both or neither ventricular chamber is captured with pacing. One could potentially utilize a 12-lead EGG for this analysis. This can be impractical. Surface lead I by itself, however, may be very useful for capture determination. The predominant QRS deflection during native LBBB or right ventricular pacing (i.e. pacing-induced LBBB) in lead I typically is a wide positive complex of generous amplitude. 

Little WC, Ohno M, Kitzman DW, Thomas JD, and Cheng CP. Determination of left ventricular chamber stiffness from the time for deceleration of early left ventricular filling. Circulation 1995 92 1933-9. 

Muscles, bone, and tendons in the human body are examples of natural organic materials that exhibit piezoelectric effects. For example, one of the authors (Gerdeen) has a medical defect called super ventricular tacardia (SVT), wherein an electric short between the left ventricular chamber and the sinus node in the heart causes au irregular heartbeat. He takes medicine to block this short. Some people have the opposite problem. They have artificial pacemakers installed with electrodes contacting the heart muscles to regulate the heart rate. Normally the human body regulates the heart beats with its own pacemaker when it is in a healthy condition. 

---