Georg Grossmann

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.

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 assess 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.

Quantification of mitral and tricuspid regurgitation by the proximal flow convergence method using two-dimensional colour Doppler and colour Doppler M-mode: Influence of the mechanism of regurgitation

In patients with mitral (n=77: organic=49, functional=28) and tricuspid regurgitation (n=55: functional=54) quantified by angiography, the temporal variation of the proximal flow convergence region throughout systole was assessed by colour Doppler M-Mode, and peak and mean radius of the proximal isovelocity surface area for 28 cm/s blood flow velocity were measured. Additionally, the peak radius derived from two-dimensional colour Doppler was obtained. About 50% of the patients with mitral and tricuspid regurgitation showed a typical temporal variation of the flow convergence region related to the mechanism of regurgitation. The different proximal isovelocity surface area radii were similarly correlated to the angiographic grade in mitral and tricuspid regurgitation (rank correlation coefficients 0.55-0.89) and they differentiated mild to moderate (grade < or =II) from severe (grade > or =III) mitral and tricuspid regurgitation with comparable accuracy (82-96%). However, moderate mitral regurgitation due to leaflet prolapse in two patients was correctly classified by the mean M-mode radius and overestimated by both peak radii. Only half of the patients showed a typical variation of the flow convergence region related to the mechanism of regurgitation. The different proximal isovelocity surface area radii were suitable to quantify mitral and tricuspid regurgitation in most patients. However, in mitral regurgitation due to leaflet prolapse the use of the mean M-mode radius may avoid overestimation.

Direct Current Application: Easy Induction of Ventricular Fibrillation for the Determination of the Defibrillation Threshold in Patients with Implantable Cardioverter Defibrillators

For the determination of the defibrillation threshold, the induction of ventricular fibrillation is mandatory. However, in severely damaged hearts it is sometimes difficult to induce ventricular fibrillation by rapid stimulation or alternating current. Only rapid nonclinical ventricular tachycardias may result, and their cardioversion threshold may be different from the defibrillation threshold. Therefore, it was the purpose of this study to test the potential of direct current (DC) application to rapidly induce ventricular fibrillation in patients with an implanted Cardioverter defibrillator. The defibrillation threshold had to be determined in 13 patients (9 with coronary heart disease, 4 with dilative cardiomyopathy, ejection fraction 35%) during and 2 weeks after the implantation of a Cardioverter defibrillator. DC was applied 37 times by a commercially available 9‐V DC battery via a bipolar catheter for about 3 seconds. Ventricular fibrillation was induced 23 times (62%) and rapid nonclinical ventricular tachycardias were induced six times (16%). In one patient clinical ventricular tachycardia was observed. In seven instances (19%) sinus rhythm remained. In 12 of the 13 patients, ventricular fibrillation could be induced by DC. Thus, the induction of ventricular fibrillation by DC application may serve as an additional tool to induce ventricular fibrillation, determining the defibrillation threshold in implantable Cardioverter defibrillator patients.

Influence of the orifice inlet angle on the velocity profile across a flow convergence region by color Doppler in vitro.

The converging flow field proximal to a leaking valve is determined among other things by the orifice inlet angle formed by the leaflets. Thus, the inlet angle affects the determination of regurgitant flow rate by the flow convergence method. Based on the hypothesis of spheric isovelocity surfaces, others had postulated that a local velocity within the flow convergence should change inversely proportional to changes in the three‐dimensional inlet angle. This concept would allow correction of the determination of regurgitant flow for nonplanar orifice inlet angles. We tested this concept in vitro. In a flow model, the flow convergence region proximal to different orifice plates was imaged by color Doppler: funnel‐shaped, planar and tip‐shaped (inverted funnels) orifice plates, with circular orifices of 2‐ and 7‐mm diameter. Velocity profiles across the flow convergence along the flow centerline were read from the color maps. As predicted, the local velocities were inversely related to the inlet angle, but only at the 2‐mm funnel orifices, this effect was inversely proportional to the three‐dimensional inlet angle (i.e., in agreement with the mentioned concept). However, for any 7‐mm orifice and/or inlet angle of > 180°, the effect of the inlet angle was considerably less than predicted by the aforementioned concept. With increasing orifice diameter and with decreasing distance to the orifice, the effect of the orifice inlet angle was reduced. The effect of the orifice inlet angle on the flow convergence region is modulated by orifice size and the distance to the orifice. Therefore, correction of flow estimates in proportion to the three‐dimensional inlet angle will lead to considerable errors in most situations of clinical relevance, namely to massive overcorrection when analyzing velocities located close to wide orifices.

Aortic regurgitant flow by color Doppler measurement of the local velocity 7 mm above the leak orifice - Part 2: comparison with cardiac catheterization

Eine In-vitro-Studie zur Flußkonvergenz-Methode bei Aorteninsuffizienz hatte gezeigt, daß der Regurgitationsfluß aus der lokalen Geschwindigkeit v(7 mm) 7 mm oberhalb des Leckostiums abgeleitet werden kann. In dieser klinischen Studie wurde dieser Zusammenhang an Patienten erprobt. Bei 67 Patienten mit Aorteninsuffizienz wurde die Flußkonvergenz-Region mit dem Farbdoppler dargestellt. Analog zu der o. g. In-vitro-Studie wurden Geschwindigkeitsprofile der Beschleunigung durch die Flußkonvergenz aus den Farbkarten extrahiert. Die Profile wurden mit einer multiplikativen Regression gefittet. Auf der Regressionskurve wurde die v(7 mm) abgelesen und daraus der Regurgitationsfluß Q errechnet gemäß dem in vitro gefundenen Zusammenhang (Q = v(7 mm)· cm2/0,28). Es fand sich ein enger Zusammenhang zum angiographischen Schweregrad. Das aus Q errechnete Regurgitationsvolumen pro Schlag korrelierte signifikant mit den Werten der Angio-Fick-Methode (r = 0,897, SEE = 19,9 ml, y = 0,88x + 5,9 ml). Somit läßt sich auch bei Patienten aus der lokalen Geschwindigkeit 7 mm oberhalb des Leckostiums direkt der Aorten-Regurgitationsfluß bestimmen. Aims: An in vitro study of the flow convergence region in aortic regurgitation has shown that regurgitant flow rate can be derived from the local velocity v(7 mm) at 7 mm distance above the leak orifice. This clinical study was performed to test this method in patients. Methods and results: In 67 patients with aortic regurgitation, the flow convergence region was imaged by color Doppler. By analogy with the afore mentioned in vitro study, velocity profiles of the acceleration across the flow convergence region were read from the color maps. The profiles were fitted by using a multiplicative regression model. The v(7 mm) was read from the regression curve, and instantaneous regurgitant flow Q was derived from the v(7 mm) with the equation developed in vitro (Q = v(7 mm)· cm2/0,28). Q showed a close association with the angiographic grade. Q-derived regurgitant stroke volume correlated significantly with invasive measurements by the angio-Fick method (r = 0,897, SEE = 19,9 ml, y = 0,88x + 5,9 ml). Conclusions: Within the color Doppler flow convergence region of aortic regurgitation, the local velocity at 7 mm distance to the leak reflects regurgitant flow rate.

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 inpracticable 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 PRF 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 distanced=2–4 through 8–11 mm to the orifice, the low setup atd=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.

Quantification of mitral regurgitation by colour flow Doppler imaging--value of the 'proximal isovelocity surface area' method.

In this study 97 patients with mitral regurgitation (age 62 +/- 11 years, 55 men, 42 women) quantified by angiography were studied using colour flow Doppler imaging of isovelocity surface areas in the flow convergence region proximal to the regurgitant orifice. The radii of the proximal isovelocity surface areas for the flow velocities of 28 and 41 cm/s were measured. A flow convergence region was imaged in 100% (96%) of the patients with Grade I/II or more and in 92% (64%) of the patients with Grade I mitral regurgitation for a flow velocity of 28 (41) cm/s. The radii of the proximal isovelocity surface areas correlated significantly with the angiographic grade in patients with sinus rhythm as well as atrial fibrillation. A correct differentiation of Grade I to II from Grade III to IV mitral regurgitation was provided in more than 90% of all patients for both flow velocities investigated. Assuming hemispheric proximal isovelocity surface areas, in 11 patients the regurgitant volumes from echocardiography (range: 2.6-241 (0.9-198) ml for a flow velocity = 28 (41) cm/s) correlated with, but considerably overestimated the values from cardiac catheterization (range: 1.4-72.5 ml) with r = 0.79 (0.82) (P < 0.01) and SEE = 57.9 (42.4) ml for a flow velocity of 28 (41) cm/s. It was concluded that colour flow Doppler imaging of the flow convergence region enables the diagnosis of mitral regurgitation and the differentiation between Grade I to II and Grade III to IV mitral regurgitation, but may be of little value in estimating the regurgitant volume, assuming a hemispheric symmetry of the proximal flow convergence region.

Cryoablation of an anteroseptal accessory pathway

Dr. Georg Grossmann ()) · Dr. Patrick Stiller Prof. Dr. Vinzenz Hombach · Dr. Sascha Stiller Abteilung für Kardiologie Medizinische Klinik der Universität Ulm Robert-Koch-Straße 8 89081 Ulm, Germany Tel.: 0731/500-24434 Fax: 0731/500-24490 E-Mail: georg.grossmann@uniklinik-ulm.de Sirs: Radiofrequency ablation, performed near the AV node or the His bundle, carries a risk of AV nodal damage requiring a permanent pacemaker [6, 8, 11]. Cryoablation has emerged during the last years as an alternative technique to radiofrequency ablation for the treatment of patients with AV nodal reentrant tachycardia and Wolff-Parkinson-White (WPW) syndrome [2, 5, 10]. In cases of ablation near the AV node, cryotherapy may be advantageous as its hypothermic effect allows testing of the functional effects at the potential ablation site (including the effect on AV nodal/His bundle conduction) during cryomapping. Cryomapping is a mode by which the tip of the catheter is gently cooled down to –30 C, thereby avoiding the creation of a large permanent lesion [3, 4, 10]. After successful testing at appropriate sites, permanent lesions are created by further cooling of the catheter tip temperature to –75 C or colder and administering freezing for 4 minutes. We report the case of a young female patient with an anteroseptal accessory pathway in whom cryomapping was critical in helping us determine where to place the successful permanent lesion. Case report

Value of the proximal flow convergence method for quantification of the regurgitant volume in mitral regurgitation

In der vorliegenden Untersuchung sollte der Stellenwert der proximalen Flusskonvergenzmethode zur Bestimmung des Regurgitationsvolumens der Mitralklappeninsuffizienz in Abhängigkeit von der Ursache der Insuffizienz, der Flusskonvergenzdarstellung und der Anwendung verschiedener Korrekturalgorithmen untersucht werden. Das Regurgitationsvolumen wurde bei 45 Patienten (Alter 61±13 Jahre) mit organischer (n=19) oder funktioneller (n=26) Mitralklappeninsuffizienz durch Messung der proximalen Flusskonvergenzradien bei Aliasinggeschwindigkeiten zwischen 14 und 64 cm/s im 2D-Farbdoppler bestimmt. Dabei wurden verschiedene Berechnungsalgorithmen wie eine geometrische Korrektur bei wandadhärenter Flusskonvergenzzone und ein vereinfachter Algorithmus, der als einzigen Messparameter den Flusskonvergenzradius benötigt, angewandt. Der Flusskonvergenzradius im M-Mode-Farbdoppler wurde bei einer Aliasinggeschwindigkeit von 28 cm/s dargestellt. Als Referenzmethode diente die quantitative Dopplerechokardiographie. Bei organischer Mitralklappeninsuffizienz ergaben sich Korrelationskoeffizienten/ mittlere Differenzen zwischen der Flusskonvergenzmethode und der Referenzmethode von 0,25–0,43/46–111 ml vor und 0,58–0,67/15–17 ml nach geometrischer Korrektur für die untersuchten Aliasinggeschwindigkeiten. Im M-Mode-Farbdoppler fanden sich Werte von 0,68/85 ml. Die entsprechenden Werte bei funktioneller Insuffizienz lagen bei 0,74–0,88/–5–8 ml vor und 0,74–0,88/–7–5 ml nach geometrischer Korrektur im 2D-Farbdoppler und bei 0,88/–1 ml im M-Mode-Farbdoppler. Der vereinfachte Algorithmus ergab Regurgitationsvolumina, die den unkorrigierten Werten entsprachen. Das Regurgitationsvolumen wurde bei Patienten mit organischer Mitralklappeninsuffizienz durch die Methode der proximalen Flusskonvergenz unabhängig von einer Korrektur und der Darstellung überschätzt, was den Stellenwert der Methode bei diesen Patienten erheblich einschränkte. Eine ausreichend zuverlässige Bestimmung des Regurgitationsvolumens war dagegen bei funktioneller Mitralklappeninsuffizienz möglich. Dabei konnte ein einfacher Berechnungsalgorithmus für das Regurgitationsvolumen verwendet werden. The purpose of this study was to evaluate whether the underlying mechanism of mitral regurgitation influences the reliability of the proximal flow con- vergence method to assess the regurgitant volume. Furthermore, the mode of imaging the flow convergence region and different correction algorithms for calculation of the regurgitant volume were compared. Regurgitant volume was assessed in 45 patients (age 61±13 years) with organic (n=19) and functional (n=26) mitral regurgitation by the proximal flow convergence method for aliasing velocities between 14 and 64 cm/s using two-dimensional color Doppler imaging. Different correction and calculation algorithms were compared. In addition, regurgitant volume was determined using color Doppler M-mode for an aliasing velocity of 28 cm/s. The quantitative Doppler method was used as reference. In organic mitral regurgitation correlation coefficients (mean differences) between the proximal flow convergence method and the reference method were 0.25–0.43/ 0.58–0.67 (46–111 ml/15–17 ml) before/after geometric correction of the regurgitant volume for the aliasing velocities investigated. The correlation coefficient (mean difference) using color Doppler M-mode imaging was 0.68 (85 ml). The corresponding values in functional mitral regurgitation were 0.74–0.88/0.74–0.88 (–5–8 ml/–7–5 ml) for two-dimensional color Doppler and 0.88 (–1 ml) for M-mode imaging. The regurgitant volume was overestimated by the proximal flow convergence method in organic mitral regurgitation irrespective of the application of different correction algorithms or the use of color Doppler M-mode. A sufficiently reliable determination of the regurgitant volume by the proximal flow convergence method was possible in functional mitral regurgitation. In that case a simplified calculation of the regurgitant volume based on the proximal flow convergence method was feasible.