H. P. Krayenbühl

Validation of a new automatic system for biplane quantitative coronary arteriography

SummaryIn a collaboration between the University of Texas (software) and the University of Zürich (hardware) a compact, automatic system for biplane quantitative coronary arteriography was developed. The system is based on a 35 mm filmprojector, a slow-scan CCD-camera (image digitizing) and a computer workstation (Apollo DN 3000, image storage and processing). A new calibration procedure based on two fixed reference points in the center of the image intensifier was used (isocenter technique). Contour detection of coronary arteries was carried out in biplane projection using a geometric-densitometric edge-detection algorithm. The proximal and distal luminal areas, as well as the minimal luminal area of the stenotic vessel segment were determined.Accuracy and precision were determined from precision drilled holes in a plexiglas cube which were filled with 50%, 75% and 100% contrast medium. The diameter of the holes ranged from 0.5 to 5.0 mm. The mean difference and the standard deviation of the differences between the true and the measured diameters were 0.12 ± 0.14 mm for plane A and 0.26 ± 0.17 mm for plane B, respectively. After a second order correction the mean difference amounted to 0.02 ± 0.09 mm for plane A and 0.02 ± 0.12 mm for plane B, respectively.Intra- and interobserver variability were evaluated in 5 patients (age 60 ± 10 years) with coronary artery disease using 16 normal and 5 stenotic vessel segments (cross-sectional area ranging from 0.8 to 8.7 mm2). Two independent observers analyzed the same vessel segment twice. Intraobserver variability expressed as the standard error of estimate in percent of the mean angiographic vessel area (SEE) amounted to 2.1% for observer 1 and 4.4% for observer 2, respectively. Interobserver variability expressed as SEE was 4.1% for measurement 1 and 3.6% for measurement 2, respectively.

Right ventricular diastolic function-during exercise: Effect of ischemia☆

The effects of exercise on right ventricular diastolic function were evaluated in 14 patients who underwent supine rest and exercise right ventricular angiography. On the basis of coronary anatomy and exercise left ventricular regional wall motion analysis, these patients were classified into two groups: Group 1 (n = 7) had no or only mild coronary artery disease and Group 2 (n = 7) had significant coronary disease and exercise-induced left ventricular wall motion abnormalities suggesting ischemia. Chamber stiffness at rest was higher in Group 2 (48 x 10(-3) ml-1/m2) than in Group 1 (18 x 10(-3) ml-1/m2, p = 0.006). During exercise, right ventricular filling rate in the second half of diastole was significantly lower in Group 2 (126 versus 276 ml/m2 per s, p less than 0.03). The time constant of right ventricular pressure decay decreased significantly in both groups with exercise; however, both groups displayed a parallel upward shift of the pressure-volume curve with exercise. Because ischemia could not be demonstrated in Group 1, it is an unlikely explanation for this shift. Septal shifting was not a significant factor with exercise. Because of an increase in left ventricular end-diastolic volume with exercise and a close correlation between right and left ventricular end-diastolic pressures (r = 0.96 for Group 1 and r = 0.76 for Group 2), pericardial constraint is the most likely cause for this upward shift of the pressure-volume curve. Therefore, an increase in right ventricular end-diastolic pressure may not be a reliable indicator of ischemia during exercise because this pressure is coupled to changes in left ventricular volume and pericardial constraint.

Cutaneous and coronary flow reserve in patients with microvascular angina

Microvascular angina is characterized by exercise-induced angina in patients with normal coronary arteries and reduced coronary flow reserve. Recently, a generalized disorder of abnormal vascular reactivity in microvascular angina has been postulated. Therefore, coronary flow reserve was determined by the coronary sinus thermodilution technique and compared with the cutaneous flux ratio in 6 control subjects (group 1) and 12 patients with microvascular angina (group 2). Coronary flow reserve was calculated from maximal coronary flow after 0.5 mg/kg of dipyridamole divided by flow at rest. Cutaneous flow ratio was estimated by laser Doppler fluxmetry (right forearm) before and after 4 min of suprasystolic blood pressure occlusion. Coronary flow at rest was identical in the two groups, but after maximal vasodilation with dipyridamole, coronary flow was higher in group 1 than in group 2 (p less than 0.05). Coronary flow reserve differed significantly between the two groups (2.9 in group 1 and 1.3 in group 2; p less than 0.001). Cutaneous Doppler flux at rest was higher in group 1 than in group 2 (p less than 0.05). However, the hyperemic response was identical in both groups. It is concluded that the cutaneous flux ratio in patients with microvascular angina is not impaired. Local peripheral vasomotor tone appears to be increased in patients with microvascular angina because cutaneous flow at rest is reduced. Thus, a generalized disorder of abnormal vascular reactivity cannot be confirmed in patients with microvascular angina.

Das enddiastolische Volumen der linken Kammer beim Menschen, bestimmt mit der Thermodilutionsmethode

Unte r den verschiedenen Mechanismen, welche die systolische FSrderleistung des Herzens regulicren, spielt die enddiastolische Faserl/inge eine wesentliche Rolle (FRA~cK-ST,~LI~osehes Gesetz). Da am in tak ten Herzen das enddiastolische K a m m e r v o l u m e n ein MaB ffir die enddiastolische :Faserls darstellt , k o m m t der Bes t immung des enddiastolisehen Volumens als kard iodynamische RegulationsgrSBe eine besondere Bedeutung zu. I n der vorl iegendcn Arbei t werden die Resul tate yon Bes t immungen des enddiastolischen Volumens l inker K a m m e r n eines grSl~eren Kollektivs yon Personen mi t normaler und pathologischer H/~modynamik mitgeteil t und dic Beziehungen des enddiastolischen Volumens zu andern Herzparametern im t t inbl iek auf die Beur~eilung der Myokardfunkt ion besprochen.

Über einige Korrelationen zwischen Systolenlänge und hämodynamischen Parametern beim Hund

ZusammenfassungAn Hand von 77 Kontrollwerten bei 42 Hunden wurde versucht, die elektromechanische Systole in Beziehung zu andern Herzparametern zu setzen. Dabei erwies sich die Frequenznormierung durch Bildung des Quotienten

Effect of isradipine on left ventricular relaxation and diastolic filling.

\frac{{Q - II}}{{Frequenz}}

Quantitative coronary arteriography at rest and during exercise

, die auf dem direkten linearen Verhältnis zwischenQ-II und Frequenz basiert, als sehr nützlich. Dieser Quotient ist direkt korreliert zum Schlagvolumenindex, zur Schlagarbeit und zum reziproken Wert des Austreibungswiderstandes. Er ersetzt bei den Kontrollfällen und wie bisherige Untersuchungen ergeben haben auch in einem große Teil von verschiedenen Belastungen das enddiastolische Volumen in der zur Umschreibung und Abgrenzung einer Herzinsuffizienz entscheidenden Korrelation enddiastolisches Volumen zu Austreibungswiderstand.

Accuracy of Digital Subtraction Angiocardiography for the Assessment of Global and Regional Left Ventricular Function at Rest and during Exercise

Abstract The hemodynamic response to angiotensin infusion in intact dogs was investigated with the thermodilution method developed in this clinic. End-diastolic volume (EDV), stroke volume (SV) and cardiac output (CO) were determined with this method, and calculations were made of the end-systolic volume (ESV), SV/EDV ratio, stroke work and power, mean ejection rate, circumference shortening, the total wall tension and the time derivative of intraventricular pressure generation (dP/dt) of the left ventricle. The moderate elevation of the mean systolic pressure (MSP) of the left ventricle (38.5 mm. Hg) was observed with the infusion rate of 0.49 μg./kg. min.; no significant change in CO, SV index (per kilogram body weight) and heart rate was seen in this range, but EDV index, ESV index, stroke work and power increased significantly. Post-infusion hypotension and tachycardia were also recorded. At the rate of 0.87 μg./kg./min., MSP was raised by 80 mm. Hg, SV index, stroke work and power all increased significantly, brady-cardia occurred, but CO, EDV index and ESV index did not change markedly. An average of 6.4 mg./kg. of Nethalide, a beta-adrenergic blocker, produced significant increases in EDV index and length of systole and significant decreases in heart rate, dP/dt and mean power. In response to angiotensin infusion under the blockade, increases in MSP, dP/dt, stroke work and power were shown to be somewhat less, but EDV index and ESV index increased proportionately with the rate of infusion. The correlation between EDV index and ESV index and the correlation between the total tension of the left ventricle at the end of systole and either EDV index or ESV index was good in all experiments studied. Stroke power and work increased roughly parallel to EDV index, and with the beta blockade a depressed function curve was observed. Complexity of the cardiovascular control mechanism and importance of the sympathetic innervation were briefly discussed.