In 63 St. Jude bileaflet and 34 Bjoerk-Shiley tilting disk aortic valve prostheses, Doppler continuity areas were compared to their corresponding geometric areas defined by the opening angle of the occluders. Continuity areas correlated significantly with geometric areas in Bjoerk-Shiley (p = 0.68) and St. Jude prostheses (p = 0.86). Differences between continuity and geometric areas were greater in St. Jude than in Bjoerk-Shiley valves (0.87 +/- 0.45 cm2 vs. 0.06 +/- 0.47 cm2, p < 0.0001). Exclusion of patients with atrial fibrillation, with a postoperative interval of less than 1 year or valve sizes of 19 and 21 mm did not change the results. Thus, underestimation of geometric areas is present in the St. Jude bileaflet aortic valves, while geometric and continuity areas are not significantly different in Bjoerk-Shiley prostheses. These results are attributable to the effect of valve-type-dependent velocity profiles.

In addition to further studies using Doppler catheters to assess blood flow velocity during coronary angioplasty this study intends to evaluate the functional significance of coronary stenoses and to estimate their hemodynamic relevance prior to and after percutaneous transluminal coronary angioplasty (PTCA). Diameters of coronary artery stenoses were quantified by means of the cardiovascular angiographic analysis system (CAAS) both prior to and following successful PTCA in 37 patients. During coronary artery angioplasty a 12 M:Hz 0.018-in. Doppler-tipped guidewire was used to measure prestenotic and poststenotic parameters of coronary artery flow velocity both prior to and following PTCA. The minimal stenosis diameter was raised from 1.01 +/- 0.58 to 1.76 +/- 0.73 mm (P < 0.0001), the percent diameter stenosis decreased from 63 +/- 11 to 35 +/- 6% (P < 0.0001). Prestenotic average (APV) and maximum peak velocity (MPV), peak velocity integral (PVI), average systolic (ASPV) and diastolic (ADPV) peak velocity, systolic (SPVI) and diastolic (DPVI) peak velocity integral, and diastolic/systolic velocity ratio showed--in contrast to further studies--a considerably significant difference (P < 0.05), whereas poststenotic Doppler data (APV, MPV, PVI, ASPV, DSPV, SPVI, DPVI, DSVR) differed highly significantly (P < 0.0001) prior to and following PTCA. Prestenotic and poststenotic measurements of coronary artery flow velocity differed significantly before and after PTCA and offer the potential for estimating both the hemodynamic relevance of coronary artery stenoses and success of PTCA.

With the advent of ultrafast Magnetic Resonance Imaging (MRI), it is now possible to produce images with high temporal resolution. This gives the opportunity to record the passage of the paramagnetic contrast material Gadolinium-DTPA through the tissue of the heart muscle, yielding information on regional myocardial perfusion. We assessed the accuracy of MRI to detect and quantify reductions in coronary flow secondary to stenosis in dogs and patients. Regional blood flow was measured in dogs by left atrial injection of microspheres labeled with different radioactive isotopes. Signal intensity (SI) curves were generated in regions of interest over the myocardium and the cavum of the left ventricle. A newly developed two-compartment model based on the indicator-dilution method was used for interpretation of the SI-curves. In an optimization process the free parameters of the model equation were fitted to the measured SI-curves. The following flow parameters were determined: model parameter Q*, time to peak intensity (T), maximum signal intensity (SImax) and mean transit time (MTT) as calculated from a gamma variate fit. Absolute blood flow values were calculated for the parameters MTT and Q* assuming that the intravascular volume represents 10% of the total myocardial tissue volume. Measurements were performed on a 1.5 T Magnetom SP (Siemens AG, Erlangen) using a Turbo Flash sequence (TR = 6.5 ms, TE = 3 ms, TI = 100 ms, Flip Winkel = 9 degrees). Endsystolic images (voxel size = 1.8, 2.7, 15 mm3) were taken with an 18-cm Helmholtz surface coil in the short-axis view. A Gd-DTPA bolus (0.05 mmol/kg) was injected into the left atrium of 3 anesthetized closed-chest dogs. From the myocardial SI-curves the different parameters of myocardial perfusion were compared with flow assessed by microsphere injection over a wide range of myocardial blood flows (from 0.04 ml/min/g to 7.6 ml/min/g). A third-order polynominal fit showed a good correlation for the parameter Q* and MTT, whereas T and SImax were found to have a poor correlation. The linear regression analysis for a limited range of 2 ml/min/g was significantly underestimated by the MRT-measurements, but the parameter Q* showed the smallest amount of the divergent changes.(ABSTRACT TRUNCATED AT 400 WORDS)

With the advent of ultrafast Magnetic Resonance Imaging (MRI), it is now possible to produce images with high temporal resolution. This gives the opportunity to record the passage of the paramagnetic contrast material Gadolinium-DTPA through the tissue of the heart muscle, yielding information on regional myocardial perfusion. We assessed the accuracy of MRI to detect and quantify reductions in coronary flow secondary to stenosis in dogs and patients. Regional blood flow was measured in dogs by left atrial injection of microspheres labeled with different radioactive isotopes. Signal intensity (SI) curves were generated in regions of interest over the myocardium and the cavum of the left ventricle. A newly developed two-compartment model based on the indicator-dilution method was used for interpretation of the SI-curves. In an optimization process the free parameters of the model equation were fitted to the measured SI-curves. The following flow parameters were determined: model parameter Q*, time to peak intensity (T), maximum signal intensity (SImax) and mean transit time (MTT) as calculated from a gamma variate fit. Absolute blood flow values were calculated for the parameters MTT and Q* assuming that the intravascular volume represents 10% of the total myocardial tissue volume. Measurements were performed on a 1.5 T Magnetom SP (Siemens AG, Erlangen) using a Turbo Flash sequence (TR = 6.5 ms, TE = 3 ms, TI = 100 ms, Flip Winkel = 9 degrees). Endsystolic images (voxel size = 1.8, 2.7, 15 mm3) were taken with an 18-cm Helmholtz surface coil in the short-axis view. A Gd-DTPA bolus (0.05 mmol/kg) was injected into the left atrium of 3 anesthetized closed-chest dogs. From the myocardial SI-curves the different parameters of myocardial perfusion were compared with flow assessed by microsphere injection over a wide range of myocardial blood flows (from 0.04 ml/min/g to 7.6 ml/min/g). A third-order polynominal fit showed a good correlation for the parameter Q* and MTT, whereas T and SImax were found to have a poor correlation. The linear regression analysis for a limited range of < 2 ml/min/g showed a superior estimation of myocardial perfusion for the parameter Q* than MTT. Blood flow > 2 ml/min/g was significantly underestimated by the MRT-measurements, but the parameter Q* showed the smallest amount of the divergent changes.(ABSTRACT TRUNCATED AT 400 WORDS)

With the advent of ultrafast Magnetic Resonance Imaging (MRI), it is now possible to produce images with high temporal resolution. This gives the opportunity to record the passage of the paramagnetic contrast material Gadolinium-DTPA through the tissue of the heart muscle, yielding information on regional myocardial perfusion. We assessed the accuracy of MRI to detect and quantify reductions in coronary flow secondary to stenosis in dogs and patients. Regional blood flow was measured in dogs by left atrial injection of microspheres labeled with different radioactive isotopes. Signal intensity (SI) curves were generated in regions of interest over the myocardium and the cavum of the left ventricle. A newly developed two-compartment model based on the indicator-dilution method was used for interpretation of the SI-curves. In an optimization process the free parameters of the model equation were fitted to the measured SI-curves. The following flow parameters were determined: model parameter Q*, time to peak intensity (T), maximum signal intensity (SImax) and mean transit time (MPT) as calculated from a gamma variate fit. Absolute blood flow values were calculated for the parameters MTT and Q* assuming that the intravascular volume represents 10 % of the total myocardial tissue volume. Measurements were performed on a 1.5 T Magnetom SP (Siemens AG, Erlangen) using a Turbo Flash sequence (TR = 6.5 ms, TE = 3 ms, TI = 100 ms, Flip Winkel = 9 degrees). Endsystolic images (voxel size = 1.8, 2.7, 15 mm(3)) were taken with an 18-cm Helmholtz surface coil in the short-axis view. A Gd-DTPA bolus (0.05 mmol/kg) was injected into the left atrium of 3 anesthetized closed-chest dogs. From the myocardial SI-curves the different parameters of myocardial perfusion were compared with flow assessed by microsphere injection over a wide range of myocardial blood flows (from 0.04 ml/min/g to 7.6 ml/min/g). A third-order polynominal fit showed a good correlation for the parameter Q* and MTT, whereas T and SImax were found to have a poor correlation. The linear regression analysis for a limited range of < 2 ml/min/g showed a superior estimation of myocardial perfusion for the parameter Q* than MTT. Blood flow > 2 ml/min/g was significantly underestimated by the MRT-measurements, but the parameter Q* showed the smallest amount of the divergent changes. In our study of 10 healthy human subjects and 10 patients the Gd-DTPA bolus was delivered through an intravenous catheter placed in the right subclavian vein. Patients with a significant proximal coronary artery stenosis identified by selective coronary angiography were found to have significantly lower blood flow values in regional myocardium with wall motion impairment compared to the non-diseased myocardium. It is concluded that ultrafast MRI can measure myocardial blood flow over a limited but clinically relevant range of flows as defined as slightly above normal to ischemic.

The angiographic assessment of left ventricular volume (LV) and ejection fraction (EF) by means of the area-length method (ALM) is based upon geometric assumptions, which might lead to erroneous results. With the development of digital subtraction angiocardiography in real-time, densitometric procedures of calculating left ventricular parameters can be used on-line. This study examines both reliability and accuracy of a densitometric technique for evaluating LV and EF in comparison to the single-plane ALM. Contrast images of heart casts and left ventricular angiograms of 54 patients suffering from different cardiac diseases were obtained by the image acquisition and processing system Polytron 1000 VR (Siemens AG, Erlangen, FRG). Digital images of both heart casts and patients were evaluated densitometrically and geometrically by two independent observers. In the phantom study the densitometric method exhibited a significantly (p < 0.01) better agreement with the true values than the ALM. The evaluation of left ventricular angiograms in patients comparing densitometry with the ALM demonstrated a relatively high residual deviation (enddiastolic volume Syx = +/- 27 ml, endsystolic volume Syx = +/- 19.4 ml). This is mainly due to systematic, method-related errors of densitometry and the morphometric technique. The intra- and interobserver variability in calculating EF showed a significantly (p < 0.05) smaller residual deviation for densitometry than for ALM; no significant differences were found for the calculation of LV. In conclusion, we demonstrated that the presented densitometric technique offers an objective and simple means of determining LV and EF with comparable reliability and validity to the area-length method.

Flow-encoded MRI sequences nowadays allow a quantitative evaluation of blood flow in any slice position. For the first time there is the possibility of determining quantitatively the volumes of both left ventricular ejection and regurgitation over the aortic valve in a non-invasive ways, thus obtaining the regurgitation fraction as a reliable measure for the evaluation of aortic valvular insufficiencies. The quantitative assessment of aortic valvular insufficiencies was carried out by MRI and compared with the diagnosis by means of Doppler ultrasound and in some cases by cardiac catheter also. The new MRI method is characterized by a good correlation with the clinical grading of aortic valvular insufficiencies. It should be possible to develop a new non-invasive standard for quantifying aortic valvular insufficiencies.

Presynaptic as well as postsynaptic adrenergic regulation abnormalities are reported in symptomatic patients with mitral valve prolapse. This study was undertaken to evaluate presynaptic sympathetic supply by m-[123I]iodobenzylguanidine scintigraphy in 17 preselected patients with mitral valve prolapse and symptoms suggestive of hyperadrenergic dysautonomia as compared to normal scintigraphic findings. Mitral valve prolapse was echocardiographically proven within the left parasternal long axis view. Percentual activity of m-[123I]iodobenzylguanidine in 33 sectors of all oblique slices along the short axis was calculated relative to the maximal uptake, set at 100%. In general, no significant differences of mean values of sectoral quantitative uptake of m-[123I]iodobenzylguanidine were detectable between patients and the control group. Only in two sectors of the basal anterolateral region P values < 0.01 were present. Thus, using m-[123I]iodobenzylguanidine scintigraphy as marker of cardiac adrenergic supply, no evidence of altered presynaptic hyperadrenergic supply was present in patients with mitral valve prolapse. These findings suggest postsynaptic regulation abnormalities to be preponderant in this condition.

By Doppler echocardiography, the performance of heart valve prostheses is assessed with the aid of maximal transprosthetic velocities, which, however, may not be representative for the full spatial velocity profile in the vicinity of mechanical valve substitutes due to flow separation by the open occluder. The purpose of this study was to determine characteristics of velocity profiles downstream of a normally functioning Björk-Shiley prosthesis. In a pulsatile flow apparatus, different flow rates of 6.3 and 8.4 l/min were delivered. Using a spatially and temporally resolving ultrasonic Doppler method, velocity profiles 20 and 30 mm distal from the prosthesis were registered and displayed in a three-dimensional grid. The spatial velocity profile was found to deviate substantially from a flat profile at these transducer positions at the two flow conditions. Distal to the minor orifice, velocities measured only 70 and 80% of those downstream of the major orifice. In between, a region of relatively slow moving flow was present. The shape of the profiles remained essentially unchanged during acceleration and deceleration of flow. Thus, spatially resolved velocity profiles downstream of mechanical prostheses can be registered by an ultrasonic Doppler device. These findings may be useful for the detection of beginning malfunction both in the experimental and the clinical setting.