An approach to designing multidimensional linear-phase FIR diamond subband filters having the perfect reconstruction property is presented. It is based on a transformation of variables technique and is equivalent to the generalized McClellan transformation. Methods for designing a whole class of transformation are given. The approach consists of two parts; design of the transformation and design of the 1-D filters. The use of Lagrange halfband filters to design the 1-D filters is discussed. The modification of a particular Lagrange halfband filter which gives a pair of simple 1-D filters that are almost similar to each other in their frequency characteristics but still form a perfect reconstruction pair is presented. The design technique is extended to other types of two-channel sampling lattice and subband shapes, in particular, the parallelogram and the diagonally quadrant subband cases. Several numerical design examples are presented to illustrate the flexibility of the design method.

Transfer functions may be valid for the derivation of some central aortic waveform characteristics. However, in providing neither improved reproducibility nor data on parameters not obtainable from the radial waveform, transfer function techniques may offer no additional clinical benefit. The absence of correlation between measured and TF-derived aortic AI and wide limits of agreement of other parameters should be considered if this technique is utilized in clinical practice.

Arterial transfer functions have been promoted for the derivation of central aortic waveform characteristics not usually accessible noninvasively, but possibly of prognostic significance. The utility of generalized rather than gender-specific transfer functions has not been assessed. Invasive central aortic and noninvasive radial (Millar Mikro-tip tonometer) blood pressure waveforms were recorded simultaneously in 78 subjects (61 male and 17 female). Average transfer functions were obtained for the whole group and for each gender by two methods. Reverse transformation was performed with the use of each transfer function. Measured aortic waveform parameters were compared with those derived using average, gender-appropriate, and gender-inappropriate transfer functions. Differences in central waveform characteristics were demonstrated between men and women. Derived waveform parameters were significantly different from measured values [e.g., subendocardial viability index and augmentation index (P < 0.001)]. A gender-appropriate transfer function significantly improved the derivation of some parameters, including systolic pressure and systolic and diastolic pressure time integrals (P < 0.05). Generalized arterial transfer functions may not be universally applicable across all waveform parameters of potential interest, and gender-specific transfer functions may be more appropriate.

OBJECTIVE -Optimal blood pressure control in subjects with diabetes reduces cardiovascular complications. There is theoretical benefit in the assessment of central aortic waveforms including the augmentation index, which is taken as a putative index of stiffness. Transfer functions may be used to reconstruct aortic from radial pressure waveforms; however, a single generalized transfer function may not be appropriate for all patients. We aimed to evaluate the technique in subjects with diabetes.RESEARCH DESIGN AND METHODS -Simultaneous invasive central aortic and noninvasive radial waveforms were acquired in 19 subjects with type 2 diabetes, and a diabetesspecific transfer function was derived. Similar data were acquired from 38 age-and sex-matched subjects without diabetes. Central waveforms were reconstructed using a generalized transfer function in all patients and the diabetes-specific transfer function in individuals with diabetes.RESULTS -There was no difference between groups in measured central pressures. The error in generalized transfer function-derived systolic pressure was greater in individuals with diabetes (6 Ϯ 7 mmHg) (mean Ϯ SD) than without diabetes (2 Ϯ 8 mmHg) (P Ͻ 0.05). Errors in other parameters were no different. The diabetes-specific transfer function reduced the error in derived systolic pressure to 0 Ϯ 7 mmHg in individuals with diabetes-no different than that with the generalized transfer function in individuals without diabetes. The central augmentation index reconstructed by either transfer function was unrelated to that directly measured.CONCLUSIONS -A generalized transfer function is inappropriate for the derivation of central waveforms in subjects with type 2 diabetes. Errors in subjects with diabetes might be reduced with a diabetes-specific transfer function. Diabetes Care 27:746 -751, 2004C ardiovascular disease is the major cause of mortality and morbidity in western societies (1). Diabetes, reaching epidemic proportions in some populations, is an important risk factor for cardiovascular disease, augmenting the effects of coexistent risk factors such as hypertension (1). Optimal blood pressure control in subjects with diabetes and hypertension significantly reduces risk of cardiovascular complications and death (2). Thus, potential benefit from improvements in the recognition and treatment of hypertension may be even greater for patients with diabetes than without.The central aortic pressure waveform is thought to represent the sum of a forward traveling wave, the product of cardiac contraction, and a backward traveling wave, due to wave reflection from the periphery (3). The timing, and potentially the magnitude, of wave reflection in the ascending aorta is influenced by arterial mechanical properties that change early in the course of diabetes (4,5) and may adversely affect the relationship between cardiac workload and myocardial blood supply (3). With increasing appreciation of the potential contribution of wave reflections to central aortic blood pressure and cardiovascula...

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