Deconvolution analysis in radionuclide quantitation of left-to-right cardiac shunts.

A poor bolus injection results in an unsatisfactory quantitative radionuclide angiocardiogram in as many as 20% of children with possible, left-to-right (L-R) cardiac shunts. Deconvolution analysis was applied to similar studies in experimental animals to determine whether dependence on the input bolus could be minimized. Repeated good-bolus, prolonged (greater than 2.5 sec), or multiple-peak injections were made in four normal dogs and seven dogs with surgically created atrial septal defects (ASD). QP/QS was determined using the gamma function. The mean QP/QS from ten good-bolus studies in each animal was used as the standard for comparison. In five trials in normal animals, where a prolonged or double-peak bolus led to a shunt calculation (QP/QS greater than 1.2 : 1), deconvolution resulted in QP/QS = 1.0. Deconvolution improved shunt quantitation in eight of ten trials in animals that received a prolonged bolus. The correlation between the reference QP/QS and the QP/QS calculated from uncorrected bad bolus studies was only 0.39 (p greater than 0.20). After deconvolution using a low pass filter, the correlation improved significantly (r = 0.77, p less than 0.01). The technique gave inconsistent results with multiple-peak bolus injections. Deconvolution analysis in these studies is useful in preventing normals from being classified as shunts, and in improving shunt quantitation after a prolonged bolus. Clinical testing of this technique in children with suspected L-R shunts seems warranted.

Prosthetic aortic valves. Indications for and results of reoperation.

During a 15-year period from January 1962 through December 1976, 42 patients who had undergone a previous aortic valve replacement underwent reoperation. The mean interval between operations was 4.4 years. The indications for reoperation were aortic regurgitation resulting from mechanical malfunction (12 patients), ball variance (15 patients), perivalvular leaks (five patients), prosthetic stenosis (eight patients), anemia (one patient), and recurrent emboli (one patient). The indications were characteristic of a specific valve series. The most common reoperation was aortic valve replacement (29/42), which had a 10.3% operative mortality. Poppet change (10/42) carried a 10% operative mortality and no operative deaths followed suture closure of perivalvular leaks. Eighty-eight percent of patients alive six months after reoperation were New York Heart Association functional class 1 or 2. At last follow-up, 95% of surviving patients were still functional class 1 or 2, with a mean cumulative survival of 4.7 years after reoperation. This experience demonstrates that those patients surviving long enough to undergo reoperation can expect a reasonable operative risk, long-term survival, and excellent clinical improvement.