Kenjiro Kambara

Intermittent Oversensing due to Internal Insulation Damage of Temperature Sensing Rate Responsive Pacemaker Lead in Subclavian Venipuncture Method

A 49‐year‐old male patient developed sensing failure (oversensing) 6 months after the implantation of a temperature sensing rate responsive pacemaker by the subclavian venipuncture method. Intermittent oversensing appeared in the sitting position, but did not appear in the supine position. Temperature telemetry showed an excessive fluctuation of the temperature data points while sitting and while doing a treadmill exercise test. Internal insulation damage was found approximately 33 cm from the distal tip of the expianted lead. The electrical resistance between one thermistor coil and the pacing coil changed from 9 kiloohms to 40 ohms when moderate pressure was applied to the outside lead in the fault area. This electrical shunt resulted from internal insulation damage that resulted from compression of the pacemaker lead between the first rib and the clavicle.

Correction for apparent prolongation of mean transit time resulting from response time in a thermodilution system

A method of correcting an apparent prolongation in the measured transit time (MTT) resulting from the response time of the thermodilution system was investigated. The mean response times (MRTs) were measured for five commercially available thermistor-tipped catheters by recording their step function response curves. Using a flow loop model filled with saline through a mixing chamber, pairs of thermodilution curves were recorded simultaneously with pairs of catheters, and the influence of MRT on MTT was studied for the constant flow rates of 1-6 L/min. The difference in MRTs between a pair of thermodilution systems correlated with the difference in MTTs between a corresponding pair of thermodilution curves, yielding an equation. It was concluded that the apparent prolongation of MTT due to response time can be eliminated by subtracting the MRT from the measured MTT.<<ETX>>

Usefulness of the Pulmonary Vein Flow Velocity-Time Profile as an Estimate of Left Atrial Storage Fraction

During ventricular systole, the left atrium (LA) stores a certain amount of ventricular stroke volume; this is defined as an LA storage volume. From cineangiocardiograms, an LA storage fraction is obtained as the ratio of the LA storage volume to left ventric ular stroke volume. From the pulmonary vein (PV) flow velocity-time profile, the LA storage fraction may be estimated as a ratio of the PV flow velocity-time integral during systole (Sa) to a sum of that during systole and diastole (Sa+Da), namely, Sa/(Sa+Da), provided that the PV cross-sectional area remains relatively unchanged during one cardiac cycle and that the PV flow velocity-time profile is similar in any of the PVs draining to the LA. To evaluate usefulness of Doppler echocardiographic method of estimating the LA storage fraction, the authors measured the LA storage fraction from the left upper PV flow velocity-time profile by transesophageal Doppler echocardiography and compared it with the LA storage fraction from conventional cineangiocardiographic volumes. (continued on next page) Subjects were 23 patients with a variety of cardiac diseases in normal sinus rhythm, ranging from eighteen to seventy-four years of age. The LA storage fraction was 0.58 ±0.12 (mean ±SD) from cineangiocardiography and 0.64 ±0.08 from Doppler echocar diography. Although the LA storage fraction from Doppler echocardiography was signif icantly larger than that from cineangiocardiography (P < 0.01), the correlation was good (r=0.643). The authors conclude that the left upper PV flow velocity-time profile appears to provide a better correlation with that by cineangiography and may be used as a reliable quantitative estimate of the LA storage fraction.