Influence of pulse repetition frequency and high pass filter on color Doppler maps of converging flow in vitro.

Assessment of regurgitant flow by the flow convergence method is based on reading absolute velocities from color Doppler maps. Velocity overestimation by high pass filtering above 100 Hz has been reported. An extremely low filter, however, is impracticable in patients. A ratio of pulse repetition frequency (PRF)/filter of 10/1 usually results in good quality color maps as judged visually. We studied in vitro the influence of RPF and filter on the absolute velocities within color maps of the flow convergence, keeping PRF/filter at 10/1. The color maps were also compared with computerized flow simulations. Flow across different orifice plates was scanned using two different setups for each flow condition: low velocity setup (PRF 600-2500 Hz, filter 50-300 Hz) and high (PRF 1500-6000 Hz, filter 200-600 Hz). From the color maps, velocity profile curves were read along the flow center line across the flow convergence. The high velocity setup provided artefact-free color maps at a distance d = 2-4 through 8-11 mm to the orifice, the low setup at d = 6-8 through 18 mm. Within the overlapping range (d = 6-8 through 8-11 mm), the resulting curves showed no significant differences in local velocity, with a slight trend towards higher velocities with the high velocity setup (2.2-2.9%). The simulations agreed well with color Doppler except for slightly lower values at d > 10-12 mm. Changes in PRF and filter have no significant influence on the absolute velocities displayed within color maps as long as PRF/filter is kept close to 10/1.

[Color Doppler echocardiography of the flow convergence region in vitro: effect of the orifice shape on proximal velocity profile]. / Farbdoppler-Echokardiographie der Flusskonvergenzregion in vitro: Einfluss der Lochform auf das proximale Geschwindigkeitsprofil.

The flow convergence method serves to determine flow across orifices (like valve leaks) by color Doppler. Both the PISA method (proximal isovelocity surface areas) and the PVP method (proximal velocity profile) were developed in vitro at circular orifice plates. Therefore, we studied the influence of a non-circular orifice shape on the color map of the flow convergence. Steady flow across orifices of the following shapes was imaged by color Doppler: Oval (6 x 2 mm), slit (12 x 1.5 mm), three-star (diameter 100, area 30 mm2), circular twin-orifice (two circular orifices diameter 2 mm at 10 mm distance from each other) and oval twin-orifice (two ovals 6 x 2 mm at 10 mm distance). As reference we imaged circular orifices with a similar opening area. The alias method was used to locate discrete velocities within the color map, and the proximal velocity profile along the flow center line was analyzed (mean of 24 subsequent images). The local velocity was plotted (y-axis) against its distance to the orifice (x-axis) providing proximal velocity profile curves. The more the orifice shape differed from circular, the more the proximal velocity profile was shifted downward: The profile proximal to the oval was not different from the reference profile proximal to the circular orifice. The profile proximal to the slit was considerably slowed, and proximal to the three-star was even slightly slower (local velocity -12 %, -23 % and -29 % at 14, 8 and 5 mm distance to the orifice). If the circular reference orifice corresponded to total flow across the twin-orifice, the proximal velocity profile of the latter was also shifted markedly downward (-20 %, -18 % and -23 % at 14, 8 and 5 mm distance to the circular twin-orifice). However, if the reference profile corresponded to flow across only one opening of the twin-orifice, the proximal velocity profile of the latter was shifted considerably upwards (+60 %, +71 % and +50 % at 14, 8, and 5 mm distance). Deviation of the orifice shape from circular leads to lower local velocities within the flow convergence; thus neglecting this orifice shape would result in underestimation of flow by the flow convergence method. However, presence of parallel neighboring flow increases the local velocities; neglecting this effect would lead to corresponding overestimation of flow.

Reduction of exercise-induced myocardial perfusion defects by isosorbide-5-nitrate: assessment using quantitative Tc-99m-MIBI-SPECT.

BACKGROUND: Although nitrates were introduced more than 100 years ago and have been used for the treatment of angina pectoris, there are still some open questions concerning the mechanism of their action on myocardial ischemia. There are also insufficient data regarding the influence of any anti-ischemic medication on the results of myocardial perfusion scintigraphy. METHODS: To assess the influence of a mononitrate, 30 patients with stable angina pectoris, coronary stenosis > or = 70% and normal left ventricular function were examined using quantitative Tc-99m-MIBI exercise-single photon emission computed tomography (SPECT). On the same day, 5 h after a randomized double-blind dose of 60 mg sustained-release isosorbide-5-nitrate or placebo, SPECT was repeated with identical stress protocol. The results were analyzed using a semi-automatic polar coordinate program that allows definition of areas with significant decreased blood flow expressed as a percentage of standard vessel area. RESULTS: In the vessel areas with the largest perfusion defects, the mean defect size decreased after isosorbide-5-nitrate from 38.2 +/- 31.0% to 29.1 +/- 33.8% (reduction by 24%; P < 0.05) and increased from 35.2 +/- 27.6% to 36.6 +/- 27.4% after placebo (increase by 4%; P = NS). The difference between defect size changes was also significant (P < 0.05). CONCLUSION: Acute administration of sustained-release isosorbide-5-nitrate significantly reduces the size of exercise-induced perfusion defects as assessed using quantitative Tc-99m-MIBI-SPECT.

Cardiac toxicity of bone marrow transplantation: predictive value of cardiologic evaluation before transplant.

PURPOSE: This study analyses the risk of cardiac complications and its individual predictability in bone marrow transplantation (BMT). PATIENTS AND METHODS: One hundred seventy patients undergoing allogeneic (n = 150) or autologous (n = 20) BMT were evaluated by physical examination, history, rest and exercise ECG, chest x-ray, two-dimensional echocardiography, and radionuclide ventriculography (RNV) before BMT, and monitored for 3 months thereafter. RESULTS: Following BMT, cardiac toxicity occurred in eight patients (4.7%). Three patients (1.8%) developed life-threatening toxicity (pericardial effusion and left ventricular failure, n = 2; sudden cardiac arrest, n = 1). Thirty-eight patients (22%) had pathologic findings before BMT. In 22 patients, left ventricular ejection fraction (EF) determined by RNV was reduced to less than 55%. This was the only abnormality in 17 patients and was generally mild, with a lowest EF of 42%. There was no correlation between overall results of cardiologic evaluation before BMT and cardiac toxicity. Cardiotoxic events occurred more frequently in patients with a reduced EF (P < .05). However, this was restricted to minor cardiac events. Life-threatening cardiac toxicity was not significantly increased in patients with pathologic results before BMT. Moreover, none of the patients with an EF less than 50% developed cardiac toxicity. CONCLUSION: Life-threatening cardiac toxicity is rare after BMT, occurring in less than 2% of all patients. Although the occurrence of cardiac toxicity is correlated with a reduction of EF before BMT, life-threatening cardiac toxicity cannot be predicted in individual patients.

Doppler echocardiographic evaluation of left ventricular diastolic function in acute hypothyroidism.

OBJECTIVE: Left ventricular diastolic dysfunction is an important cause of symptomatic heart failure. Previous studies suggest that thyroid dysfunction affects left ventricular diastolic function but the underlying mechanisms remain controversial. The study was undertaken to asses the influence of acute hypothyroidism on left ventricular diastolic function and to elucidate possible underlying mechanisms by means of Doppler echocardiography in a group of athyreotic patients, whose thyroid state depended only on external thyroid hormone supply and could therefore easily be controlled. PATIENTS: Eleven patients (5 men, 6 women, aged 20-55 years), who had had total thyroidectomy, were investigated during mild hyperthyroidism and during acute hypothyroidism. Additionally, 11 healthy control subjects aged 25-51 years were included in the study. DESIGN: M-mode echocardiography of the left ventricle and pulsed-wave Doppler echocardiography of the transmitral flow velocity pattern were carried out. RESULTS: Acute hypothyroidism produced a decrease of left ventricular end-diastolic diameter from 48 +/- 5 to 46 +/- 5 mm (mean +/- SD P < 0.05), of peak velocity of early diastolic filling from 0.52 +/- 0.10 to 0.42 +/- 0.05 m/s (P < 0.05), of peak velocity of late diastolic filling from 0.42 +/- 0.10 to 0.36 +/- 0.09 m/s (P < 0.05), and a decreased time-velocity integral of early diastolic filling (6.2 +/- 1.8 vs 5.1 +/- 0.7 cm, P < 0.05). The other M-mode and Doppler echocardiographic parameters did not differ between the hyperthyroid and the hypothyroid states. CONCLUSIONS: The observed changes of the trans-mitral flow velocity pattern during acute hypothyroidism can be attributed to a reduction of pre-load. There is no direct evidence that acute hypothyroidism affects the intrinsic diastolic properties of the left ventricle.

Systolic ventricular function in acute hypothyroidism: a study using Doppler echocardiography.

The influence of thyroid state on left ventricular systolic function was studied in 11 patients (5 men, 6 women, aged 20-55 years) without cardiac disease, who had undergone total thyroidectomy and radioiodine treatment for thyroid cancer before. Pulsed-wave Doppler echocardiographic measuring of aortic blood flow and two-dimensional/time-motion (2D/M-mode) echocardiography were performed on two occasions once while the patients were mildly hyperthyroid on thyroxine replacement therapy and once when they were hypothyroid. During hypothyroidism left ventricular end-diastolic diameter decreased from 48 +/- 5 mm to 46 +/- 5 mm (p < 0.05). The diameter of the aortic ring, the left ventricular end-systolic diameter, the thickness of the interventricular septum and posterior wall, and fractional shortening did not differ significantly between the two studies. The following parameter of aortic blood flow changed significantly when passing from the hyperthyroid to the hypothyroid state: peak velocity (0.86 +/- 0.15 m/s versus 0.72 +/- 0.15 m/s, p < 0.01); mean velocity (0.49 +/- 0.08 m/s versus 0.44 +/- 0.08 m/s, p < 0.01); time- velocity integral (14.1 +/- 3.0 cm versus 12.3 +/- 3.1 cm, p < 0.05); stroke volume (43.0 +/- 9.7 ml versus 35.2 +/- 8.2 ml, p < 0.05); and preejection period (124 +/- 23 ms versus 147 +/- 21 ms, p < 0.01). Peak acceleration, mean acceleration, acceleration time and left ventricular ejection time did not change when the thyroid state was altered. It is concluded that left ventricular contractile function was not affected by acute hypothyroidism.(ABSTRACT TRUNCATED AT 250 WORDS)

Diastolic ventricular function in type 1 diabetic patients: a study using Doppler echocardiography.

The transmitral flow velocity pattern of 28 Type 1 diabetic patients and 39 age-matched healthy control subjects was studied for determination of left ventricular diastolic function. No patient had systemic hypertension, congestive heart failure, or ischaemic heart disease by clinical or electrocardiographic criteria. Echocardiographic measures of systolic ventricular function were within normal range in all subjects. The ratio of early to late transmitral peak flow velocity (ve/va) was significantly decreased in the diabetic patients (1.3 +/- 0.1 (+/- SE) vs 1.6 +/- 0.1, p less than 0.05), while other Doppler derived variables did not show any significant difference. No correlation of ve/va with duration of diabetes was found (r = -0.27), but it correlated with age in both groups (both r = -0.40, p less than 0.05). Furthermore, a significant correlation was found between ve/va and heart rate (r = -0.55 for diabetic patients, p less than 0.01; r = -0.58 for control subjects, p less than 0.01). After matching for heart rate (24 diabetic patients and 24 control subjects) no significant decrease of ve/va was observed in the diabetic group.

Emergency resuscitation in children. The role of intraosseous infusion.

Intraosseous infusion is a temporary procedure for use in pediatric emergencies when intravenous access is difficult. Multiple drugs and fluids can be safely administered through the intraosseous route. Dosage and rate of infusion are essentially the same as with intravenous infusion.