Martin Stauch

Equilibrium (Gated) radionuclide ventriculography

Conclusions1.Radionuclide ventriculography after homogenous tracer distribution provides a reliable noninvasive method for the global and regional assessment of left ventricular function.2.The most important global parameter is the left ventricular ejection fraction, which can be measured accurately. Decrease of ejection fraction during exercise is an important feature of coronary artery disease. Maximal relaxation velocity (fast filling phase) measured from the global time-volume curve, seems to be the most sensitive global parameter of left ventricular insufficiency.3.Regional wall motion abnormalities can be assessed qualitatively from the cineventriculogram (“movie mode”) or in a quantitative manner. During stress, hypokinetic, dyskinetic, and akinetic regions are characteristic features of coronary artery disease.4.The most extensive quantitative evaluation of regional wall motion is based on the regional time-activity curve of the representative heart cycle, which can be obtained reliably. Checking the set of regional time-activity curves with respect to one parameter results in a parametric scan, which displays the distribution of the respective parameter in the left ventricular region.5.In our department, six parametric scans including distribution of amplitude and phase of the first Fourier element are obtained. These six scans describe the regional wall motion reliably and in detail. While determination of ejection fraction and qualitative assessment of regional wall motion has been widely applied, the clinical value of the parametric scans cannot be finally assessed at this time.

Color Doppler echocardiographic determination of mitral regurgitant flow from the proximal velocity profile of the flow convergence region

Flow rate across an orifice can be determined from color Doppler echocardiographic maps of the flow convergence region proximal to the orifice. Different methods have been developed in vitro. The proximal velocity profile method was prospectively evaluated in patients with mitral regurgitation. Color Doppler echocardiography was performed in 74 patients before cardiac catheterization. The increasing velocities within the flow convergence region were determined in an apical plane on the straight line from the transducer to the leak; thus the proximal velocity profile was established and plotted on a nomogram. Instantaneous regurgitant flow rate was derived from the position of the resulting curve in relation to the nomograms reference curves, which were derived from in vitro measurements. Regurgitant stroke volume was calculated as regurgitant flow rate.regurgitant velocity-time integral/regurgitant peak velocity, using additional continuous-wave Doppler. The 55 patients with angiographic regurgitation had a close association between regurgitant flow rate (0 to 600 ml/s) and angiographic grade (Spearmans rank correlation coefficient = 0.91; p < 0.0001). Regurgitant flow rate did not overlap between grades < or = 2+, 3+ and 4+. In 16 patients, regurgitant stroke volume by echocardiography correlated well with that by the angiography/Fick method (r = 0.88; SEE = 17.1 ml), with a regression line close to identity (y = 0.89x + 12.7 ml). The proximal velocity profile method enables determination of mitral regurgitant flow and estimation of regurgitant volume.

Color Doppler Determination of Regurgitant Flow: From Proximal Isovelocity Surface Areas to Proximal Velocity Profiles: An In Vitro Study

There is not yet a completely satisfactory Doppler method for determining the severity of valvular regurgitation. Recently, interest has focused on the so‐called “flow convergence region”. Color Doppler provides a longitudinal velocity profile of the flow convergence region proximal to restrictive orifices. With respect to determination of regurgitant flow rate, we studied the influence of orifice flow rate and orifice size on the proximal velocity profile. In a phantom model, flow across circular orifices was studied. The distance r(v) of discrete velocities detected proximal to the orifice was measured along the flow center line. Velocity profiles were established. (1) Proximal isovelocity surfaces: The radius r(v) also represented the central radius of the proximal isovelocity surfaces. Increases in flow resulted in larger central radii r(v). Application of the continuity equation and analysis of the resulting values yielded a radius and an orifice size dependence of the geometric isovelocity surface shape. Therefore, their surface area and flow rate could not be calculated from these axial measurements alone. (2) Proximal velocity profiles: The resulting hyperbolic velocity profile curves (x axis = velocity [v], y axis = distance [r(v)]) are shifted rightward by increases in flow. In contrast, increases in orifice size make the curve steeper, but large r(v) are not affected. This differential influence of flow rate and orifice size allows orifice size independent determination of flow rate. A nomogram is presented as one possible method for flow determination.

Left ventricular function at rest and during exercise in acute hypothyroidism.

The effect of hypothyroidism on left ventricular function at rest and during exercise was studied in nine patients without demonstrable cardiovascular disease who had had total thyroidectomy and ablative radioiodine treatment for thyroid cancer. Radionuclide ventriculography and simultaneous right heart catheterisation were performed while the patients were hypothyroid two weeks after stopping triiodothyronine treatment (to permit routine screening for metastases) and while they were euthyroid on thyroxine replacement treatment. When the patients were hypothyroid, cardiac output, stroke volume, and end diastolic volume at rest were all lower and peripheral resistance was higher than when they were euthyroid. Pulmonary capillary wedge pressure, right atrial pressure, heart rate, left ventricular ejection fraction, and the systolic pressure:volume relation of the left ventricle, which was used as an estimate of the contractile state, were not significantly different when the patients were hypothyroid or euthyroid. During exercise, heart rate, cardiac output, end diastolic volume, and stroke volume were higher when the patients were euthyroid than when they were hypothyroid. Again, pulmonary capillary wedge pressure, ejection fraction, and the systolic pressure:volume relation were similar in both thyroid states. The data suggest that the alterations in cardiac performance seen in short term hypothyroidism are primarily related to changes in loading conditions and exercise heart rate; they do not suggest that acute thyroid hormone deficiency has a major effect on the contractile properties of the myocardium.

Transcutaneous Oxygen Tension and Doppler Ankle Pressure During Upper and Lower Body Exercise in Patients with Peripheral Arterial Occlusive Disease

The effects of upper and lower body exercise on blood supply to the lower extremi ties were investigated in patients with peripheral arterial occlusive disease (PAOD) by measurements of transcutaneous oxygen tension (tcPO2) and Doppler ankle pressure (DAP). Twenty patients with PAOD (PAOD group) and 10 subjects without PAOD (control group) performed treadmill test (TT), recumbent cycle ergometry (CE), and rowing ergometry (RE) with a fixed seat. The tcPO2 was registered on the calf and DAP was measured at the end of each step of CE and RE. The walking distance in TT of the control group was not limited (> 1000 m), whereas that of the PAOD group was 161 m in median. In the control group there was no significant difference of performance between CE (125 ±33 W) and RE (111 ±24 W), whereas in the PAOD group, performance was lower in CE (72 ±31 W) than in RE (102 ±28 W) (P <0.01). DAP of controls increased during both CE (136 to 165 mmHg) and RE (170 to 213 mmHg), whereas the DAP of the PAOD group decreased during CE (from 85 to 44 mmHg) and remained relatively constant during RE (113 to 101 mmHg). In controls, tcPO2 did not distinctly change during TT (70 to 66 mmHg) and increased during CE (58 to 73 mmHg) and RE (69 to 82 mmHg), whereas in the PAOD group, tcPO2 decreased during TT (66 to 33 mmHg) and CE (50 to 22 mmHg) and remained almost unchanged in RE (64 to 60 mmHg). A hyperbolic relationship was found between tcPO 2 and DAP. In conclusion, during upper body exercise, blood supply to the lower extremities in patients with PAOD was not affected, whereas lower body exercise led to exhaustion of the functional reserve of blood supply. Because of a hyperbolic relationship between tcPO 2 and DAP, tcPO2 remained relatively constant if blood supply was sufficient, but in disturbed blood supply a small change of DAP was accompanied by a great change of tcPO2. Therefore, in critical ischemia the change of tcPO2 was more sensitive than that of DAP.

QTU-ABNORMALITIES, SINUS BRADYCARDIA AND ADAMS-STOKES ATTACKS DUE TO VENTRICULAR TACHYARRHYTHMIA

Tachyarrhythmic Adams‐Stokes attacks, provoked by physical and emotional stress, are reported in a 10‐year‐old girl with sinus brady‐cardia at rest, prominent U waves, a normal resting QT‐interval but QT‐prolongation on exercise. Two brothers, the father and the paternal grandmother have a slight QT‐prolongation but no attacks. In the proband, physical exercise and small doses of a beta‐adrenergic stimulator reliably cause ventricular bigemini and/or runs of multifocal ventricular extra‐systoles while increase in heart rate by Atropine and atrial pacing does not. The ventricular arrhythmia is improved by beta‐receptor blocking agents. It is proposed that in this and other patients with abnormal repolarization the ventricular myocardium is unduely sensitive to sympathetic stimuli, resulting in ventricular tachyarrhythmia.

Interobserver and intermethod variation in evaluation of regional wall motion of the left ventricle

AbstractTo determine the variation in the repeated evaluation of quantitative regional wall motion of the left ventricle (LV) from right anterior oblique (RAO) silhouettes, an intra- and inter-observer test was performed in 17 patients without wall motion abnormalities, using nine different methods of regional wall motion (RWM) analysis. The results were:1.Around the cardiac apex and near the valve plane there are regions where the subjective contour delineation yields regional mean discrepancies up to 4–5 mm (2–3 mm, respectively, near the valves); while in the other regions the mean discrepancies are usually smaller than 1 mm.2.Absolute regional contour discrepancies, calculated in mm, show only small differences in the various methods applied for RWM analysis.3.If these discrepancies instead are calculated as relative changes (in relative percent) of hemiaxial or segmental shortening or area diminution, the method applied is of great significance, since the length of the axes can vary considerably from method to method.4.From all methods applied for RWM analysis, that of Mathes [10] (radial method) had the smallest average discrepancy. These results suggest, that the LV silhouette may be best defined in the anterior and inferior wall area, while in other regions subjective impressions of contour tracing may produce a considerable variation, which can be further enhanced by the method applied for RWM analysis. Methods that employ relatively large axes of as similar as possible length are therefore preferred.

Comparison of whole-Body Thallium Imaging with Transcutaneous PO2 in Studying Regional Blood Supply in Patients with Peripheral Arterial Occlusive Disease

Quantitatively estimating functional reserve of blood supply to the legs in patients with peripheral arterial occlusive disease (PAOD) remains a clinical issue. This study was designed to investigate the regional blood supply to the legs in PAOD patients during exercise by use of thallium 201 (201Tl) whole-body imaging in comparison with transcu taneous PO2 (tcPO2) measurement. Thirty-three patients with PAOD and 10 subjects without PAOD (control) performed an incremental cycle ergometry (CE), while tcPO2 was continuously registered on the involved calf. In the last minute of exercise, 2 mCi of 201Tl was injected intravenously and the 201Tl whole-body images were taken immediately (stress) and four hours (redistrib ution) following stress with a dual-head camera system. Regional blood supply (RBS) (%) was calculated from the geometric mean counts of the region of interest divided by the total counts of the whole body. The performance of PAOD patients was reduced in doing CE, and tcPO2 fell distinctly in PAOD patients (from 51 to 19 mmHg) whereas it increased in controls (from 57 to 67 mmHg). The RBS in PAOD patients was obviously reduced in comparison with that of controls. While in controls the RBS of the calf (3.1%) at stress did not differ from that at redistribution (3.4%), in PAOD patients the redistribution RBS (2.8%) increased as compared with that of stress (1.5%). There was a hyperbolic relationship between stress RBS of the calf and the velocity of tcPO2 fall in PAOD patients during exercise test (velocity of tcPO2 fall = -0.032 + 0.39/RBS, r2 = 0.54, P < 0.05). In conclusion, the RBS determined by 201Tl whole-body imaging is comparable to the tcPO 2 measurement in differentiating patients with PAOD from subjects without PAOD during exercise. Regional 201Tl uptake reflects regional blood supply in PAOD patients. There is a hyperbolic relationship between the RBS derived from 201Tl whole-body imaging and tcPO2 in PAOD patients during exercise, implying that in a critical ischemia the lower the RBS is, the more steeply the tcPO2 decreases.

Left ventricular function and wall thickness in long‐term insulin‐dependent diabetes mellitus: an echocardiographic study

Abstract. Left ventricular function and wall thickness were evaluated in 111 type I diabetic subjects (mean age 25.5 ± 9 years, mean duration of diabetes 13.4 ± 6.2 years), using 2‐D‐derived M‐mode echocardiography. Patients were carefully selected for the absence of major coronary risk factors or manifest cardiac disorders, and compared with 91 age‐ and sex‐matched control subjects. Fractional shortening and the maximal velocity of circumferential fibre shortening did not differ significantly between the two groups. Furthermore, no differences were found in the diastolic functional parameter of velocity of circumferential fibre extension. Posterior wall thickness was significantly increased in the diabetic patients compared to the controls (9.5 ± 1.8 mm vs. 8.4 ± 1.3 mm, P < 0.01). As the thickness of the interventricular septum was also moderately increased (9.2 ± 2.2 mm vs. 8.9 ± 1.7 mm, NS), these findings provide evidence for an early structural change of the myocardium in young diabetic patients without clinically relevant functional consequences.

Limitations of radionuclide ventriculography in the non-invasive diagnosis of coronary artery disease. A correlation with right heart haemodynamic values during exercise.

A consecutive series of 56 patients with chest pain but no evidence of previous myocardial infarction was prospectively studied by radionuclide ventriculography to determine the value of global and regional radionuclide indices in detecting coronary artery disease. The results were correlated with the clinical judgment of chest pain, the results of the exercise electrocardiogram, and the right heart haemodynamic measurements during exercise. As a result of the criteria for entry, the study group was representative of the population seen in such a clinical setting. Only 25% of patients had coronary artery disease. The predictive power of radionuclide ventriculography was limited. The conventionally used criterion that normal subjects have an increase in left ventricular ejection fraction of at least 5% with exercise provided only 78% sensitivity and 57% specificity. Fourier analysis and visual interpretation of radionuclide studies wrongly diagnosed three out of 10 patients with extensive disease requiring surgery. These results suggest that radionuclide ventriculography is of limited value in the non-invasive diagnosis of coronary artery disease.