Wall shear stress distribution at the carotid bifurcation: influence of eversion carotid endarterectomy.

OBJECTIVES: To test the feasibility of four-dimensional (4D) flow MRI to quantify the systolic wall shear stress (WSSsystole) and oscillatory shear index (OSI) in high-grade internal carotid artery (ICA) stenosis before and after endarterectomy (CEA). METHODS: Twenty patients with ≥60 % ICA stenosis were prospectively and consequently included. Four-dimensional flow MRI was used to measure individual time-resolved 3D blood flow velocities. Segmental WSSsystole and OSI were derived at eight wall segments in analysis planes positioned along the ICA, common (CCA) and external carotid artery (ECA). RESULTS: Regional WSSsystole of all patients decreased after CEA (P < 0.05). Changes were most prominent at the ICA bulb but remained unchanged in the CCA and ECA. OSI was significantly lower after CEA in the lateral vessel walls (P < 0.05). For analysis planes at the stenosis in- and outlet, a reduction of mean WSSsystole by 32 % and 52 % (P < 0.001) and OSI distal to the stenosis (40 %, P = 0.01) was found after CEA. CONCLUSIONS: Our findings show the potential of in vivo 4D flow MRI to quantify haemodynamic changes in wall shear stress even in patients with complex flow conditions.

3D blood flow characteristics in the carotid artery bifurcation assessed by flow-sensitive 4D MRI at 3T.

To determine three-dimensional (3D) blood flow patterns in the carotid bifurcation, 10 healthy volunteers and nine patients with internal carotid artery (ICA) stenosis > or =50% were examined by flow-sensitive 4D MRI at 3T. Absolute and mean blood velocities, pulsatility index (PI), and resistance index (RI) were measured in the common carotid arteries (CCAs) by duplex sonography (DS) and compared with flow-sensitive 4D MRI. Furthermore, 3D MRI blood flow patterns in the carotid bifurcation of volunteers and patients before and after recanalization were graded by two independent readers. Blood flow velocities measured by MRI were 31-39% lower than in DS. However, PI and RI differed by only 13-16%. Rating of 3D flow characteristics in the ICA revealed consistent patterns for filling and helical flow in volunteers. In patients with ICA stenosis, 3D blood flow visualization was successfully employed to detect markedly altered filling and helical flow patterns (forward-moving spiral flow) in the ICA bulb and to evaluate the effect of revascularization, which restored filling and helical flow. Our results demonstrate the feasibility of flow-sensitive 4D MRI for the quantification and 3D visualization of physiological and pathological flow patterns in the carotid artery bifurcation.

[Bypass perforation by stent implantation: complication management. A case report]. / Bypass-Perforation durch Stentimplantation: Komplikationsmanagement. Ein Fallbericht.

We describe a case-report on an perforation of an aorto-coronary venous bypass graft, a complication induced by a stent-implantation. Perforations of coronary arteries are rare, however, for interventional cardiologists well-known complications. This case report is of special interest (1) because the perforation did not occur in a coronary artery but rather in an eight year old venous bypass graft and (2) because the perforation was induced by a stent-implantation. In addition, this case report describes in great detail the management of vessel perforation: several invasive methods contributed to minimize pericardial effusion and to stabilize the patient until surgical revision could be performed.

Minimal-invasive, video-assisted vein harvesting for cardiac and vascular surgical procedures.

Harvesting of the saphenous vein is a routine procedure in coronary and peripheral vascular surgery. It is usually performed using a continuous long skin incision. Minor complications are reported in up to 24% (hematoma, wound dehiscence, infection, pain) and major problems necessitating surgical interventions (bleeding, abscess) in less than 1%. These complications lead to a prolonged hospital stay. To reduce these complications we have used a new endoscopic, video-assisted technique in 17 patients. Harvesting of the total length of the saphenous vein is possible with only one 2-3 cm long incision proximally the knee joint. We conclude that this technique is safe, may reduce the morbidity of saphenous vein harvesting and is associated with a perfect cosmetic result.

["Myxoma syndrome"--a "benign" disease with "malignant" course]. / "Myxoma-Syndrom"--eine "benigne" Erkrankung mit "malignem" Krankheitsverlauf.

We are reporting on a 36 year-old woman who presented with recurrent cardiac myxomas over a period of nine years. Two of the tumors typically originated in the left atrium and one in the right atrium. Tumor embolization was the presenting symptom twice, leading to reversible cerebral ischemia and minor pulmonary embolism, respectively. The third tumor remained asymptomatic and was detected during routine echocardiographic examination. Based on a positive family history of cardiac tumors, a facially pronounced hyperpigmentation of the skin and the presence of a thyroid adenoma, the diagnosis of a "myxoma syndrome" was established. Patients with "myxoma syndrome" are generally younger than their counterparts with "sporadic myxoma" (mean age at diagnosis 25 vs. 56 years) and have a high frequency of unusual skin freckling (68%). Familial clustering of cardiac myxomas is also frequent (25%). The tumors may be located in any of the cardiac chambers (87% in the atrias, 13% in the ventricles, 50% at multiple sites simultaneously) and have relatively high (18%) 5-year recurrence rate after surgical excision. Since the clinical signs of cardiac tumors are non-specific, diagnosis essentially relies on cardiac imaging by echocardiography, computer tomography, or angiography. The superiority of transesophageal echocardiography is emphasized in this report.

Alpha 2C-adrenoceptor-modulated release of noradrenaline in human right atrium.

1. The aim of the present study was to characterize the presynaptic alpha 2-autoreceptors in human right atrium in terms of the alpha 2A-D system. Segments of atrial appendages were preincubated with [3H]-noradrenaline and then superfused in the presence of cocaine and stimulated electrically. pEC30% values of eight alpha-adrenoceptor antagonists with discriminatory power were determined. pEC30% is the negative logarithm of the antagonist concentration that increased the stimulation-induced overflow of tritium by 30%. For four antagonists, the dissociation constant KD was determined, in addition to pEC30%, against the overflow-inhibiting effect of 5-bromo-6-(2-imidazolin-2-ylamino)-quinoxaline (UK 14,304) under autoinhibition-free conditions. 2. pEC30% and KD values yielded identical rank orders of antagonist affinity (rauwolscine > WB 4101 > phentolamine > prazosin) suggesting that both released noradrenaline and the exogenous agonist UK 14,304 activated the same receptor to inhibit release. 3. The eight antagonist pEC30% values obtained in right atrium correlated significantly with their pEC30% values, reported in the literature, at the presynaptic alpha 2C-autoreceptors in human kidney (r = 0.817; slope of the regression line 1.03). No significant correlation was obtained between pEC30% values at atrial autoreceptors and pKD values at previously characterized alpha 2A-autoreceptors in rabbit and alpha 2D-autoreceptors in rat, mouse and guinea-pig tissues. 4. Comparison of antagonist pEC30% values with their pKD values at native alpha 2 binding sites in cells or tissues that express a single subtype only, and with pKD values at alpha 2 binding sites in membranes of COS cells transfected with human alpha 2 subtype genes confirms the alpha 2C character of the atrial autoreceptors: significant correlations were obtained exclusively with the alpha 2C binding sites. 5. Ratios of KD values were computed for alpha 2-autoreceptors in human right atrium and for binding sites in COS cells transfected with human alpha 2 subtype genes. The autoreceptor ratios corresponded well with the respective ratios for the alpha 2C binding sites (maximal three fold deviation) but were, in part, markedly different from ratios calculated for alpha 2A and alpha 2B binding sites (up to 166 fold deviation). This outcome supports the alpha 2C designation of the autoreceptors. 6. In conclusion, the presynaptic alpha 2-autoreceptors in human right atrium are alpha 2C. In this they agree with the previously characterized alpha 2-autoreceptors in human kidney. The alpha 2C classification possibly separates, in general, human alpha 2-autoreceptors from those in lagomorph (rabbit) and rodent (rat, mouse, guinea pig) species that have been proposed to be predominantly alpha 2A or alpha 2D.

[Limitation of Doppler echocardiography in evaluation of aortic valve prostheses]]. / Limitation der Doppler-Echokardiographie in der Beurteilung von Aortenklappenprothesen.

Doppler echocardiography has been widely used as a noninvasive method to evaluate valvular heart diseases. However, the diagnostic impact of Doppler echocardiography in the evaluation of prosthetic valves is discussed controversially. Reasons are, on one hand, the high variabilities of transvalvular gradients observed for normal prosthetic devices and, on the other hand, results of experimental in vitro studies demonstrating an impressive discrepancy between Doppler-echocardiographic and invasive measurements of the transvalvular gradients in prosthetic valves. In a prospective study, we evaluated 11 out of 335 patients after aortic valve replacement who demonstrated an elevated transvalvular gradient over the prosthetic valve. Eight patients had a St. Jude medical prosthesis (19-23 mm), two patients had a Medtronic Hall prosthesis, and one patient a Björk-Shiley prosthesis. The maximal instantaneous gradient measured by Doppler-echocardiography was 74 +/- 15 mmHg, the mean gradient was 47 +/- 12 mmHg. The prosthetic orifice area calculated by the continuity equation using the left ventricular outflow tract diameter was 0.86 +/- 0.25 cm2, and that calculated by using the prosthetic ring diameter was 0.98 +/- 0.23 cm2. None of the patients had a severe aortic valve regurgitation. All patients were clinically asymptomatic. Transesophageal echocardiography and x-ray showed a normal prosthetic function. Angiographic examination performed in seven patients showed a peak-to-peak gradient of 26 +/- 9 mmHg, and demonstrated a marked discrepancy between Doppler-echocardiographic and invasive results. These results confirm the clinical limitations of Doppler echocardiography to distinguish between normal and disturbed prosthetic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Cystic adventitial degeneration as a cause of dynamic stenosis of the popliteal artery: a case report.

Cystic adventitial degeneration, which is generally localized in the popliteal artery, leads to a dynamic, exercise-dependent flow inhibition. The cysts of the adventitia, which increase in size with exercise, cause an increasing degree of stenosis which can be completely reversed after a longer period if rest. Angiographic presentation may therefore be misleading. Functional examination with Doppler sonography is able to identify the obstruction in such cases. Resection of the involved vessel and restoration of flow by interposition of a vein graft is the therapy of first choice.

Thermographic evaluation of myocardial temperature during infusion of cold cardioplegia.

Delay in myocardial cooling during an infusion of cold cardioplegic solution may occur in patients with coronary artery disease. Forty patients with significant stenosis of the left anterior descending coronary artery (LAD) were divided into 3 groups according to the extent of the LAD stenosis. Group A consisted of 12 patients with 70% stenosis. Group B included 23 patients with 90% stenosis, and in group C there were 5 patients with LAD occlusion. Myocardial temperature was measured with a thermocamera during infusion of 2000 ml 8 to 10 degrees C cold Bretschneider's cardioplegic solution and compared to 10 other patients without coronary artery disease undergoing mitral valve replacement (group D). In group A the myocardium cooled to 15 degrees C after 4 1/2 minutes and to 12 degrees C after 10 minutes. In group B the myocardial temperature was 15 degrees C after 5 minutes and 12 degrees C after 10 minutes. In group C the temperature reached 18 degrees C after 5 minutes and 14 degrees C after 10 minutes. In group D the myocardial temperature was 12 degrees C after 3 minutes and 10 degrees C after 7 minutes. This study shows far better myocardial cooling rates in patients with unobstructed coronary arteries.