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The pulmonary autograft offers low rates of degeneration, endocarditis, and thromboembolism for a period lasting >20 years, particularly in the young, with reoperation mainly required for malpositioning of the autograft cusps. The capacity of the autograft to maintain viability with minimal degeneration is not matched by any other biological valve replacement.

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sumM^Y Thirty-nine consecutive patients, aged 5 to 57 years, were followed for two to 15 years with serial haemodynamic studies after removal of fixed subaortic stenosis, which was never a "membrane". Two late deaths occurred, one sudden and one in congestive failure. Of 37 survivors, 25 were asymptomatic and could be classified as good or excellent if judged by well-being. Seven were symptomatic, two having had reoperation for fixed subaortic stenosis, and four needed long-term pacing.Evaluation, including the effect of isoprenaline, showed important dynamic obstruction in 17, five of whom redeveloped fixed obstruction. Seven had congestive features without outflow gradients, and 14 had neither congestion nor outflow obstruction. Complete assessment therefore confirmed that only 14 (36%) were haemodynamically satisfactory; two of them had permanent pacing, and four had had aortic valve surgery.Fixed subaortic stenosis should be removed early, when diagnosed, and completely before secondary myocardial changes occur. Patients however "well" need regular supervision and early haemodynamic assessment. The aortic valve, whether repaired, replaced, or untouched, remains a site for infective endocarditis for life.The fixed subaortic stenosis removed at operation may not be present in that form at birth, but acquired secondary to other congenital abnormalities which remain in the patient.Fixed subaortic stenosis, which is usually classified as a congenital lesion, takes the form of a crescentic shelf or complete ring. It is often eccentric, attached to the anterior cusp of the mitral valve and/or the left coronary cusp of the aortic valve, 1 to 2 cm below the aortic valve. Surgical excision is relatively simple and should, theoretically, relieve the haemodynamic problem. However, after surgical treatment was established, it was soon noted that results were unpredictable.1-4It appeared from several different series that despite removal of the fixed part of the obstruction the cardiac muscle could continue to behave physiologically like hypertrophic cardiomyopathy57 and that there might be an overlap between the conditions. The clinical and haemodynamic state of longterm survivors after resection of fixed subaortic stenosis has now been examined with sequential studies. From these results it may be necessary to

Dr. Beranek has skillfully tailored the new material to fit into spaces where earlier material was deleted. This necessitated omission of some important older references in favor of new references, to avoid renumbering all references. Regrettable resultant deletions include references to publications by Olson, French and Steinberg, Bauer, and Fletcher, all of which have been well documented in other books, of course. The American Institute of Physics' Publication Department deserves congratulations for combining the old and new material without obvious appearance differences. Few authors could do what Dr. Beranek has done, i.e., extensively revise and modernize a book written 40 years ago on a comprehensive subject. Even fewer would do so as a labor of love for their professional society.Even those of us who have the original edition will benefit from this new edition. For younger acousticians, this book will be valuable as a storehouse of both current and historical information about acoustical measurements.

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