Exercise thallium-201 imaging in complete left bundle branch block and the prevalence of septal perfusion defects.

To determine the prevalence of septal defects in a generalized referral population, the records of 93 consecutive patients with complete left bundle branch block (BBB) who underwent symptom-limited treadmill exercise testing with thallium-201 myocardial imaging over a 3-year period were reviewed. Segmental analysis of the planar thallium-201 images was performed in a blinded fashion with agreement by consensus. Computerized quantitative analysis of the images also was independently performed, and was correlated with the visual interpretations. Forty-seven patients (51%) had normal images, and 46 (49%) had defects of greater than or equal to 2 segments. In the abnormal studies, only 13 patients (14% of the total population) had septal defects, while a much higher number of patients, 33 (39%), had inferior or apical defects, or both. Coronary angiography was performed in 6 patients with septal defects: Significant narrowing of the left anterior descending coronary artery was found in 4 patients, a narrowed right coronary artery was found in 1, and normal coronary arteries were seen in the other patient. In conclusion, whereas previous studies have suggested a high percentage of false-positive septal defects in patients with left BBB, this study demonstrates a low prevalence (14%) of septal defects in a large population of unselected patients presenting for exercise thallium-201 imaging. Therefore, exercise thallium-201 imaging remains a useful procedure for evaluating patients with complete left BBB.

Impact of early post-exercise myocardial redistribution of TI-201 on SPECT imaging. Preliminary observations.

In a series of 62 male patients undergoing exercise TI-201 SPECT myocardial scintigraphy, planar 45 degrees LAO images were acquired before (2-5 minutes postinjection, P1) and after (35 minutes postinjection, P2) the initial SPECT study in order to identify those patients with redistribution during the first 30 minutes after exercise. Consensus interpretation by four readers identified early redistribution (between P1 and P2) in 11 patients (18%), rated major (change of greater than 1.5 scoring unit) in five and minor (change of 1-1.5 scoring unit) in six. Only one patient (2%) showed major early redistribution that could not be appreciated on corresponding SPECT images. In this preliminary investigation, early thallium redistribution sufficient to affect identification of significant exercise-induced ischemia on SPECT imaging was infrequent and of limited clinical importance.

Advances in ICD lead systems.

We have presented both technical and clinical data indicating that transvenous lead systems are comparable to standard epicardial ICD systems with respect to efficacy. In addition there may be a reduction in morbidity when compared with the standard epicardial implant. We have shown for the Endotak and Transvene systems that each has its own idiosyncrasies, advantages, and disadvantages. Other lead systems are too early in their clinical evaluations for such definitive statements to be made. Regarding long-term reliability, the issues of mechanical integrity of the insulation and conductor materials, as well as the stability (or otherwise) of sensing and defibrillating characteristics remains to be determined for all lead systems. Similarly, compatibility between lead systems and pulse generators made by different manufacturers cannot be assumed, but needs to be prospectively examined in rigorous clinical trials.