PubMed · 5741828
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M Greenspan, J D Cohn, L R Del Guercio. 1968. Ventricular function in pulmonary embolism shock.. https://doi.org/10.1016/s0003-4975(10)65973-5
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BACKGROUND: The time constant of ventricular relaxation (tau) is a quantitative measure of diastolic performance requiring intraventricular pressure recording. This study validates in humans an equation relating tau to left ventricular pressure at peak -dP/dt (P0), pressure at mitral valve opening (PMV), and isovolumic relaxation time (IVRTinv). The clinically obtainable parameters peak systolic blood pressure (Ps), mean left atrial pressure (PLA), and Doppler-derived IVRT (IVRTDopp) are then substituted into this equation to obtain tau Dopp noninvasively. METHODS AND RESULTS: High-fidelity left atrial and left ventricular pressure recordings with simultaneous Doppler by transesophageal echocardiography were obtained from 11 patients during cardiac surgery. Direct curve fitting to the left ventricular pressure trace by Levenberg-Marquardt regression assuming a zero asymptote generated tau LM, the "gold standard" against which tau calc (IVRT inv/[ln(P0)-ln(PMV)]) and tau Dopp [IVRTDopp/[ln(Ps)-ln(PLA)]] were compared. For 123 cycles analyzed in 18 hemodynamic states, mean tau LM was 53.8 +/- 12.9 ms. tau calc (51.5 +/- 11 ms) correlated closely with this standard (r = .87, SEE = 5.5 ms). Noninvasive tau Dopp (43.8 +/- 11 ms) underestimated tau LM but exhibited close linear correlation (n = 88, r = .75, SEE = 7.5 ms). Substituting PLA = 10 mm Hg into the equation yielded tau 10 (48.7 +/- 15 ms), which also closely correlated with the standard (r = .62, SEE = 11.6 ms). CONCLUSIONS: The previously obtained analytical expression relating IVRT, invasive pressures, and tau is valid in humans. Furthermore, a more clinically obtainable, noninvasive method of obtaining tau also closely predicts this important measure of diastolic function.
Various dietary assessment instruments were used in the Multiple Risk Factor Intervention Trial (MRFIT), either to assist with the special intervention program or to assess trial outcomes. For the latter purpose, the 24-h recall was the main method and was selected with the understanding that the single recall collected at baseline and at most annual visits--considered by itself--would be useful mainly for assessing groups rather than individuals. Major components of the data collection and analysis system developed for the 24-h recall included central training and certification of nutritionists, a central nutrient coding system, and a food grouping system to assist interventionists in using recall data for counseling. Several additional nutritional assessment methods were used for men in the special intervention group only to assist them in attaining the dietary goals. These goals consisted chiefly of reduced intake of saturated fat and cholesterol and a modest increase in intake of polyunsaturated fat; total fat intake was also decreased, primarily for control of energy intake. Short-term success at attainment of these nutritional goals was evaluated by means of 3-d food records collected before the intervention and after the initial 10-wk intensive intervention period. The MRFIT nutrient goals, which became more vigorous at certain points in the trial, were translated into food patterns. Adherence to these food patterns was also assessed by scoring of 3-d records and by subjective evaluation by nutritionists throughout the trial. Methods of collecting other trial data are also described in this chapter.
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