A novel approach to calculation of mean mitral valve gradient by Doppler echocardiography.

The Doppler-derived mean mitral valve gradient (DeltaP(M)) based on the simplified Bernoulli equation requires computerized integration of the Doppler signal and evaluation by a technician with the use of special equipment. We have noted empirically that the DeltaP(M) can be derived by the equation DeltaP(M) = (P(P) - P(T)) / 3 + P(T). Peak (P(P)) and trough (P(T)) pressures are derived from the simplified Bernoulli equation (P = 4V(2)). This equation can be used by the experienced observer to calculate the mean mitral valve gradient without specialized equipment. The purpose of this study is to validate the above empirically derived equation in patients with mitral stenosis. We retrospectively reviewed 41 consecutive studies done at our institution from October 1, 1997, through September 30, 1998, in which mean mitral valve gradient was assessed. Each study was reviewed and the DeltaP(M), P(P), and P(T) were measured for 3 beats by using the software package on an HP Sonos 2500. DeltaP(M) was also calculated with our formula. A linear regression model was used to compare the results of the measured versus the calculated DeltaP(M). The following sub-categories were also evaluated: transthoracic studies (TTE), transesophageal studies (TEE), native valve gradients (NV), prosthetic valve gradients (PV), sinus rhythm (SR), and atrial fibrillation (AF). The results of the regression analysis of the entire population of mean versus calculated DeltaP(M) are n = 41, r = 0.99, P <.001, and standard error of the estimate (SEE) = 0.67. The regression results for the subgroups are as follows: TTE: n = 30, r = 0.99, P <.001, SEE = 0.51; TEE: n = 11, r = 0.99, P <.001, SEE = 59; NV: n = 26, r = 0.99, P <.001, SEE = 0.59; PV: n = 15, r = 0.98, P <.001, SEE = 0.84; SR: n = 23, r = 0.99, P <.001, SEE = 0.58; and AF: n = 18, r = 0.98, P <.001, SEE = 0.82. In conclusion, the simple formula that we have derived is an accurate method for calculation of mean mitral valve gradient, and it is accurate over multiple subgroups. Furthermore, the formula allows visual verification of mean mitral gradient without specialized software.

Low predictive value of positive Osler manoeuvre for diagnosing pseudohypertension.

Pseudohypertension is a condition where indirectly determined BP (e.g. via sphygmomanometry) significantly overestimates actual intraarterial pressure. A patient who has a palpable, although pulseless, radial artery while the blood pressure cuff is inflated above systolic pressure, has a positive 'Osler sign'. This 'Osler manoeuvre' has been reported to predict the presence of pseudohypertension. To evaluate its importance in diagnosing pseudohypertension, 19 hypertensive patients deemed Osler-positive by at least two observers were studied. BP was determined indirectly using a stethoscope and mercury sphygmomanometer. Intraarterial pressure was determined by a brachial artery catheter-transducer-monitoring system. For both pressure-measurement techniques and each patient, six readings were averaged to give a single systolic and diastolic value. Mean arterial pressure was calculated as diastolic pressure plus one-third the pulse pressure. Pseudohypertension was defined as a sphygmomanometric mean pressure that exceeded intraarterial mean pressure by > or = 10 mmHg. In this group of 19 Osler-positive patients, stethoscope-sphygmomanometry underestimated systolic and overestimated diastolic intraarterial pressure. For mean pressure, sphygmomanometry was > or = 10 mmHg higher than intraarterial in two patients and > or = 10 mmHg lower than intraarterial in three patients. Thus, while two patients had pseudohypertension, three could be considered to have pseudohypotension, defined as a condition where indirect blood pressure significantly underestimates intraarterial pressure. Accordingly, a positive Osler manoeuvre did not reliably predict the presence of pseudohypertension in this population.

The effect of food matrix on carbohydrate utilization during moderate exercise.

The effect of food matrix on carbohydrate utilization during moderate exercise. Med. Sci. Sports Exerc., Vol. 24, No. 3, pp. 320-326, 1992. To determine the effect of food type and form on the rate of assimilation and utilization of a meal given before exercise, five physically active adult males walked for 4 h on a 10% uphill graded treadmill at 40% VO2max. After a 12-h fast, and 30 min before exercise, subjects ingested 70 g of liquid glucose (G), a refined "hot cereal" (R), a refined "hot cereal" with water-soluble fiber (R/F), an oat bar (O), or placebo (P). Meals R/F, R, and O had significantly lower (P less than 0.05) peak plasma glucose responses than meal G (0.8, 0.9, 1.0, and 2.4 mmol.l-1, respectively). Meals R, O, and R/F had significantly lower (P less than 0.01) peak insulin responses than meal G (135, 150, 190, and 340 pmol.l-1, respectively). All meals except P contained an extrinsic tracer of 200 mg UL-13C-glucose. Mean (+/- SD) total recovery of the administered dose of 13C for all meals was 81 +/- 2%. Both O (34 +/- 4% dose.h-1) and R/F (30 +/- 3% dose.h-1) had significantly lower peak recoveries than did meal G (41 +/- 5% dose.h-1). Meal R/F had a significantly lower (P less than 0.05) rate of exogenous glucose oxidation than meal G during the first hour of exercise. These data suggest that meal R/F slows the rate of assimilation and utilization of exogenous glucose, but does not alter the cumulative 4-h utilization.

Renal and hemodynamic effects of intravenous fenoldopam versus nitroprusside in severe hypertension.

The renal and hemodynamic effects of intravenously administered fenoldopam mesylate, a novel dopamine-1 receptor agonist, were compared with those of sodium nitroprusside in 28 patients (18 male; 26 black, two white; average age, 49 +/- 3 years) with an average blood pressure of 219/137 mm Hg, most of whom presented with acute target organ damage. Fenoldopam and nitroprusside lowered blood pressure safely to an average pressure of 176/105 mm Hg; highly significant dose-response relations were found for the 13 patients receiving fenoldopam and the 15 receiving nitroprusside. Volume and sodium, potassium, and creatinine concentrations were measured in freely voided urine specimens both before and during intravenous therapy. In the fenoldopam-treated patients, there were significant increases in urinary flow (92 +/- 21 to 168 +/- 37 ml/hr, p less than 0.003), sodium excretion (227 +/- 73 to 335 +/- 90 mu eq/min, p less than 0.001), and creatinine clearance (70 +/- 11 to 93 +/- 13 ml/hr, p less than 0.003). In the nitroprusside-treated group, however, all these parameters decreased, but not significantly. For direct comparison of the two agents, the increments in urinary flow rate (+76 +/- 20 vs. -16 +/- 15 ml/hr, fenoldopam vs. nitroprusside), sodium excretion (+109 +/- 28 vs. -39 +/- 28 mu eq/min), and creatinine clearance (+23 +/- 6 vs. -11 +/- 7 ml/min) were significantly greater (p less than 0.001 for each) in the fenoldopam-treated group. Significant differences were also obtained when these parameters were calculated as percentage increase over baseline. Fenoldopam and nitroprusside are effective therapies for severe, accelerated, or malignant hypertension, but fenoldopam had additional salutary renal effects in these patients.