Differential sensitivity of TREK-1, TREK-2 and TRAAK background potassium channels to the polycationic dye ruthenium red

BACKGROUND AND PURPOSE

Pharmacological separation of the background potassium currents of closely related K2P channels is a challenging problem. We previously demonstrated that ruthenium red (RR) inhibits TASK-3 (K2 P 9.1), but not TASK-1 (K2 P 3.1) channels. RR has been extensively used to distinguish between TASK currents in native cells. In the present study, we systematically investigate the RR sensitivity of a more comprehensive set of K2 P channels.

EXPERIMENTAL APPROACH

K(+) currents were measured by two-electrode voltage clamp in Xenopus oocytes and by whole-cell patch clamp in mouse dorsal root ganglion (DRG) neurons.

KEY RESULTS

RR differentiates between two closely related members of the TREK subfamily. TREK-2 (K2 P 10.1) proved to be highly sensitive to RR (IC50 = 0.2 μM), whereas TREK-1 (K2 P 2.1) was not affected by the compound. We identified aspartate 135 (D135) as the target of the inhibitor in mouse TREK-2c. D135 lines the wall of the extracellular ion pathway (EIP), a tunnel structure through the extracellular cap characteristic for K2 P channels. TREK-1 contains isoleucine in the corresponding position. The mutation of this isoleucine (I110D) rendered TREK-1 sensitive to RR. The third member of the TREK subfamily, TRAAK (K2 P 4.1) was more potently inhibited by ruthenium violet, a contaminant in some RR preparations, than by RR. DRG neurons predominantly express TREK-2 and RR-resistant TREK-1 and TRESK (K2 P 18.1) background K(+) channels. We detected the RR-sensitive leak K(+) current component in DRG neurons.

CONCLUSIONS AND IMPLICATIONS

We propose that RR may be useful for distinguishing TREK-2 (K2P 10.1) from TREK-1 (K2P 2.1) and other RR-resistant K2 P channels in native cells.

Could successful cryoballoon ablation of paroxysmal atrial fibrillation prevent progressive left atrial remodeling?

Background

Radiofrequency catheter ablation of atrial fibrillation (AF) has been proved to be effective and to prevent progressive left atrial (LA) remodeling. Cryoballoon catheter ablation (CCA), using a different energy source, was developed to simplify the ablation procedure. Our hypothesis was that successful CCA can also prevent progressive LA remodeling.

Methods

36 patients selected for their first CCA because of nonvalvular paroxysmal AF had echocardiography before and 3, 6 and 12 months after CCA. LA diameters, volumes (LAV) and LA volume index (LAVI) were evaluated. LA function was assessed by: early diastolic velocities of the mitral annulus (Aa_sept, Aa_lat), LA filling fraction (LAFF), LA emptying fraction (LAEF) and the systolic fraction of pulmonary venous flow (PVSF). Detailed left ventricular diastolic function assessment was also performed.

Results

Excluding recurrences in the first 3-month blanking period, the clinical success rate was 64%. During one-year of follow-up, recurrent atrial arrhythmia was found in 21 patients (58%). In the recurrent group at 12 months after ablation, minimal LAV (38 ± 19 to 44 ± 20 ml; p < 0.05), maximal LAV (73 ± 23 to 81 ± 24 ml; p < 0.05), LAVI (35 ± 10 to 39 ± 11 ml/m²; p = 0.01) and the maximal LA longitudinal diameter (55 ± 5 to 59 ± 6 mm; p < 0.01) had all increased. PVSF (58 ± 9 to 50 ± 10%; p = 0.01) and LAFF (36 ± 7 to 33 ± 8%; p = 0.03) had decreased. In contrast, after successful cryoballoon ablation LA size had not increased and LA function had not declined. In the recurrent group LAEF was significantly lower at baseline and at follow-up visits.

Conclusions

In patients whose paroxysmal atrial fibrillation recurred within one year after cryoballoon catheter ablation left atrial size had increased and left atrial function had declined. In contrast, successful cryoballoon catheter ablation prevented progressive left atrial remodeling.

Predictors of the outcome of thrombolytic therapy in prosthetic mitral valve thrombosis: a study of 62 events

BACKGROUND AND AIM OF THE STUDY

Treatment strategies and guidelines in the management of prosthetic valve thrombosis (PVT) remain controversial. The study aim was to assess the success and complication rate of thrombolytic therapy (TT) by comparing thrombus size, severity of symptoms, type of prosthetic valve, and time since valve implantation.

METHODS

Between April 1993 and December 2006, TT was administered for 62 thrombotic events in 55 patients with mitral PVT. Thrombus size was measured by planimetry, and its location and mobility assessed with transesophageal echocardiography (TEE). Continuous thrombolytic treatment in obstructive PVT (OPVT) was monitored using gradient measurement by transthoracic echocardiography every 2-5 h, and by visual assessment with TEE every 24 h.

RESULTS

All patients with non-obstructive PVT (NOPVT) were in NYHA class I or II. Among 52 patients with OPVT, eight were in NYHA class I or II, and 44 in NYHA class III-IV (p < 0.0001). The thrombus area (measured with TEE) before thrombolysis was < 0.8 cm2 in 24 cases, > or = 0.8 cm2 in 21 cases, and could not be measured in 17 events. Thrombolysis was successful in 45 events (73%) including all NOPVT. In 13 events (21%) the transvalvular gradient decreased but was not normalized. Thrombolysis failed in four events (6%). Complications of thrombolysis were present in 11 events (18%), and four patients died. There was no significant difference in the outcome of TT regarding the type of artificial valve, NYHA class or thrombus size. In cases of successful thrombolysis, the time since surgery was significantly shorter than in cases of partially successful or failed thrombolysis.

CONCLUSIONS

Based on previous data and the present findings, thrombolysis can be considered as first-line treatment in all patients with PVT, independent of the valve type, NYHA functional class, and thrombus size.

An adult case of Kawasaki disease with multiplex coronary aneurysms and myocardial infarction: the role of transesophageal echocardiography

Kawasaki disease (mucocutaneous lymph node syndrome) is an acute inflammatory disease that primarily affects infants and young children. In spite of proper therapy, coronary aneurysms develop in 10 to 25% of cases. Adult diagnosis of coronary aneurysm, presumably caused by Kawasaki disease, is rare. A 37-year-old male patient with previous inferior wall myocardial infarction (MI) was admitted with an acute anterior wall MI. Coronary angiography, performed 2 weeks after successful thrombolytic therapy, showed right coronary artery occlusion and multiplex (left main, left anterior descending, left circumflex, right coronary artery) giant coronary aneurysms. Transthoracic echocardiography was unable to detect the aneurysms. Transesophageal echocardiography (TEE) visualized a large left main coronary aneurysm with an occlusive thrombus and measured low flow velocity (0.2 m/s) in the proximal left anterior descending artery. At 4 weeks control, TEE showed marked regression of the thrombus, and it was not detectable after 6 months of oral anticoagulation with acenocumarol (International Normalized Ratio: 3-3.5) and standard postinfarction therapy. After 2 years of follow-up, the patient has no symptoms, and myocardial ischemia could not be provoked by stress tests [treadmill, dipyridamole single-photon emission computed tomography (SPECT)]. We conclude that, for diagnosis and follow-up of adult Kawasaki disease, transesophageal echocardiography is indicated. The importance and efficacy of long-term anticoagulant treatment should be emphasized in this disease.

Contrast echocardiography in the diagnosis of myocardial stunning

The identification of viable myocardium within dysfunctional myocardium has important clinical implications. By using a microvascular tracer, myocardial contrast echocardiography may have the potential for prediction of myocardial viability in the acute and subacute phases of myocardial infarction. In the case presented, the normal myocardial perfusion observed after intravenous injection of the contrast agent, combined with severe wall motion abnormality following prolonged chest pain, suggested myocardial stunning. This was confirmed by normal coronary angiography and by restoration of normal left ventricular function at 1-month follow-up echocardiography.

Intracardiac calcification is a marker of generalized atherosclerosis

Aortic valve calcification (AVC) and carotid artery calcification (CAC) are considered to be markers of generalized atherosclerosis. However, the role of intracardiac calcification (ICC) (valvular and perivalvular calcification) is unclear. The objective of this retrospective study was to analyze the relationship between ICC and CAC, risk factors, and clinical atherosclerotic disease. Risk factors included age, sex, diabetes mellitus, hypercholesterolemia, and hypertension; clinical atherosclerosis comprised stroke, coronary artery disease, and peripheral artery disease. Between January 1, 2001, and January 1, 2004, all consecutive patients were enrolled into the study who underwent both carotid ultrasonography and transthoracic echocardiography examinations within 2 months. Patients with renal failure, substantial aortic stenosis, and carotid artery occlusion were excluded. There were 320 patients (104 men; mean +/- SEM age, 66.6 +/- 0.76 years). Positive results on carotid ultrasonography are defined as any CAC. Patients were categorized as having mild, moderate, or severe CAC. Positive results on transthoracic echocardiography were defined as any ICC; AVC was defined as mitral anulus calcification (MAC) or both. Intracardiac calcification was found in 181 patients, AVC in 51 patients, MAC in 48 patients, and calcification of both structures in 82 patients. Using multiple logistic regression analysis, ICC (odds ratio, 1.9), age (10-year periods) (odds ratio, 2.0), and the presence of peripheral artery disease (odds ratio, 1.7) were independent predictors of CAC. Carotid ultrasonography results were positive in 227 patients. For CAC, the sensitivities of AVC, MAC, both, and any ICC were 52.4%, 52.0%, 33.5%, and 71.2%, respectively, and the specificities were 84.9%, 87.1%, 92.5%, and 78.5%, respectively. The extension of ICC as 0, 1 location (AVC or MAC) , or 2 locations (AVC and MAC) was associated with the severity of CAC (P < .001, tau = 0.42). There was no difference between patients with AVC vs patients with MAC in the presence of different stages of CAC (P = .62). Intracardiac calcification (MAC or AVC) is an independent predictor of CAC as a marker of atherosclerosis, although the lack of ICC does not rule out atherosclerosis. Intracardiac calcification is related to CAC, with high specificity. The extension of ICC is related to the severity of atherosclerosis. Based on our results, antiatherothrombotic therapy should be considered in patients with ICC even before obtaining a positive carotid ultrasonography result.

[B-type natriuretic hormone--diagnostic and prognostic cardiovascular biomarker]

Brain natriuretic hormone and N-terminal-probrain natriuretic hormone are equally important cardiovascular biomarkers. Moderately increased brain natriuretic hormone level is a reliable predictor of preclinical, asymptomatic left ventricular dysfunction. Low brain natriuretic hormone levels are extensively used to rule out acute heart failure. Increased brain natriuretic hormone is associated to age, left ventricular hypertrophy, left atrial volume, atrial fibrillation, myocardial ischemia, renal failure, pulmonary hypertension, acute pulmonary embolism and progressive aortic stenosis. In chronic heart failure only high brain natriuretic hormone values support the diagnosis. High brain natriuretic hormone level, however, is an important overall cardiovascular prognostic biomarker. In the near future brain natriuretic hormone appears to be an interesting new therapeutic modality.

Unique presentation of hypereosinophilic syndrome: recurrent mitral prosthetic valve thrombosis without endomyocardial disease

Hypereosinophilic syndrome (HES) is defined as a prolonged, unexplained peripheral eosinophilia in a patient presenting with end-organ damage. The heart is frequently involved, resulting in eosinophilic endomyocardial disease, which is characterized by mural thrombus formation and endocardial fibrosis. Thromboembolic complications in HES are mediated by material released from eosinophilic granules. Herein is reported the case of a patient who presented, 15 years after valve replacement with a mechanical prosthesis, with clinical signs of recurrent prosthetic valve thrombosis that was caused by missed hypereosinophilia. The unique feature of the case was that the mitral prosthetic valve obstruction was the result of an eosinophilic thrombus, though no tissue infiltration or inflammation had been detected by random biopsy of the left ventricular myocardium. After nine years of effective treatment of HES there were no cardiac or extracardiac complications.

[The effect of chemo-radiotherapy on the remission and survival in patients with limited stage small cell lung cancer]

INTRODUCTION

The combined modality treatment used in case of limited stage small cell lung cancer assures the longest disease-free and average survival meanwhile maintaining an acceptable quality of life.

OBJECT

The authors examined whether the combined modality treatment in case of limited-stage small cell lung cancer affects the remission positively or not: they presumed that the therapeutic response, early partial or complete clinical and oncological remission develops earlier than in patients treated with chemotherapy. The authors' other presumption was that the early therapeutic response could be the guarantee of the longest possible disease-free and average survival.

PATIENTS AND METHOD

Small cell lung cancer (SCLC) was proved in 72 patients (23 women, 49 men, average 53 year-olds) with histological and/or cytological examination. Having examined which stage the patients were in, they proved to be in the limited stage. The patients were divided into two groups at random: cytotoxic chemotherapy containing cisplatin + etoposide was used in 36 cases, meanwhile in the other 36 cases the chemotherapy was completed with early concurrent thoracic radiotherapy.

RESULTS

The therapeutic response happened earlier (early remission) in case of patients treated with chemo-radiotherapy than with chemotherapy treatment (average 10.4-12.6 weeks, SD = 1.22-1.99). The result of the "log rank" test showing the difference between the two groups is strongly significant in favor of the chemo-radiotherapy group (p = 0.0001). In patients with early remission receiving chemo-radiotherapy, the thoracic recidives and metastasis developed later (average 74.8 weeks, SD = 44.95), furthermore the average survival also proved to be longer (93.9 weeks, SD = 57.09). The average time until the development of tumor recidives and metastasis in patients belonging to the chemotherapy group was 44.5 weeks (SD = 30.23), and the average survival was 67.4 weeks (SD = 32.77). The result of the "log rank" test proved significant advantage for the chemo-radiotherapy group both for disease-free survival (p = 0.0010) and average survival (p = 0.0079 ). Another positive effect of chemo-radiotherapy was that less thoracic recidives and central nervous system metastasis could be diagnosed. Examination of treatment toxicity showed that one has to count primarily with esophagitis and pneumonitis related to the radiotherapy in patients receiving chemo-radiotherapy.

[Warfarin or acenocoumarol is better in the anticoagulant treatment of chronic atrial fibrillation?]

A SPORTIF-III substudy.

BACKGROUND

Warfarin has been considered to provide more stable anticoagulant effect than acenocoumarol due to its longer half-life.

OBJECTIVE

The aim of this SPORTIF-III substudy was to compare acenocoumarol (A) with warfarin (W) in the same group of 74 patients, with chronic atrial fibrillation who started with W and then changed to A.

METHODS

We compared prospectively a 3 months period on W with a 3 months period on A.

RESULTS

The mean number of INR measurements per patient was 5.7 +/- 1.2 and 5.4 +/- 1.6 resp (NS). The mean percentage of INR-s in the therapeutic range of 2-3 was 49 +/- 22.6% for W and 56 +/- 26.8% for A (p < 0.05), the percentage of subtherapeutic values were not different, the supratherapeutic values however occurred more frequently on W (28 +/- 20%) than on A (19 +/- 19%), p < 0,001. There was a good correlation between A and W doses (r = 0.65, p < 0.001), the mean W dose was 5.03 +/- 1.99 mg, the mean A dose was 2.5 +/- 1.3 mg, the W/A dose ratio was computed to be 2.18 +/- 0.78.

CONCLUSIONS

1. anticoagulation effect stability was superior for A compared to W; 2. W/A dose ratio was 2.18.

Infective endocarditis resulting in rupture of sinus of valsalva with a rupture site communicating with both the right atrium and right ventricle

This report describes a patient with a rupture of the noncoronary sinus of Valsalva caused by erosion of its wall by a large right atrial vegetation not attached to the tricuspid valve without aortic valve involvement. The rupture site was located right posterior to the tricuspid septal leaflet and communicated both with the right atrium and the right ventricular inflow tract, resulting in a significant left-to-right shunt leading to severe right heart failure and shock. The diagnosis was made by transthoracic and transesophageal echocardiography. To our knowledge no similar case has been reported in the literature.

Cardiac actinomycosis in a patient presenting with acute cardiac tamponade and a mass mimicking pericardial tumour

A case of pericardial actinomycosis mimicking a pericardial tumour is reported. After the appearance of non-specific subpleural pulmonary nodules, a 48 year old woman presented with fever and clinical signs of pericardial tamponade. Subxiphoid pericardiotomy yielded a culture negative fluid and inflammatory reactive histopathology in the pericardial biopsy specimen. Because of suspected infection cefamandole was administered for 10 days and the patient became afebrile. The pericardial effusion recurred with no clinical signs two weeks later. Steroid medication resulted in rapid regression of the pericardial effusion. Subsequent echocardiography controls showed a tumour-like pericardial mass, confirmed by cardiac magnetic imaging. Surgical exploration led to the final histological diagnosis of actinomycosis. After high dose and long term penicillin G treatment the patient recovered fully with no recurrence during two years' follow up.

[Use of anticoagulant therapy in non-valvular atrial fibrillation. Analysis of a Hungarian cohort]

In nonvalvular atrial fibrillation stroke prevention by anticoagulation is clearly recommended by evidence based medicine. Underusage of coumarin treatment however is a general problem. The aim of this study was the analysis of prehospital and hospital practice of anticoagulant therapy in a Hungarian cohort. 106 consecutive patients hospitalized in a Budapest medical department with chronic non-valvular atrial fibrillation were included. Mean age was 76 years, the percentage of males was 30%. High stroke risk factors were found in all patients, at least two of them in 72%. 70% of patients were 75 years old or more. Thus anticoagulant treatment was indicated in all patients, however at admission only 30% were anticoagulated, moreover therapeutic range was achieved in only 28% of them. At discharge in 77% of all patients and in 82% without contraindications coumarin treatment could be started, practically independently of age.

CONCLUSIONS

In the Hungarian prehospital practice anticoagulant treatment of nonvalvular atrial fibrillation is underused and inefficient, but excellent rates even in international comparison can be achieved by adequate medical approach even in the elderly.

Left main coronary artery ostial stenosis: the role of transoesophageal echocardiography

Transoesophageal echocardiography (TEE) using colour flow Doppler and intracoronary flow velocity measurements by pulsed Doppler may be helpful in detecting coronary artery disease. We present a case of a middle-aged man in whom left main ostial stenosis was detected by TEE after two non-diagnostic coronary angiographies. The main message of our case is that TEE was performed and was diagnostic after two non-diagnostic coronary angiographies. If ischaemia is confirmed TEE should be performed in cases of negative coronary angiographies to rule out left main ostial stenosis.

Value of rilmenidine therapy and its combination with perindopril on blood pressure and left ventricular hypertrophy in patients with essential hypertension (VERITAS)

OBJECTIVES

The primary objective was to assess the effects of rilmenidine monotherapy and in combination with perindopril on blood pressure (BP) in patients assessed with grade 1 or 2 essential hypertension. The study also examined the effects of 2-year rilmenidine monotherapy on left ventricular hypertrophy (LVH) and on diastolic function of the left ventricle, along with the effects of rilmenidine on left ventricular mass index in hypertensive patients with no LVH, and the relationship between BP reduction and any change in LVH.

RESEARCH DESIGN AND METHODS

Mild-to-moderate hypertensive patients (n = 500) were enrolled in a multicentre 2-year open study and treated with rilmenidine (1-2 mg per day) monotherapy or rilmenidine plus perindopril (2, 4 or 8 mg per day) if control of hypertension was not achieved with rilmenidine monotherapy within 12 weeks. Blood pressure was recorded at regular intervals by the investigators and LVH measured by centralised single-blind echocardiographic reading.

RESULTS

Rilmenidine monotherapy (average dose 1.42 mg) produced a significant decrease in BP from the baseline of 163 +/- 10/100 +/- 5 mmHg to 134 +/- 10/86 +/- 7 mmHg at 1 year and to 136 +/- 10/84 +/- 7 mmHg at 2 years (p < 0.001 for both). In 188 patients with LVH, the left ventricular mass index was significantly reduced from 161.4 +/- 30.5 to 131.3 +/- 26.5 at 1 year and to 134.1 +/- 26.0 g/m(2) at 2 years (p < 0.001 for both). Addition of perindopril to those patients whose BP was not normalised by rilmenidine monotherapy after 12 weeks further decreased BP significantly from 150 +/- 13/93 +/- 8 mmHg to 142 +/- 14/89 +/- 7 mmHg at the end of the 2nd year.

CONCLUSIONS

Long-term rilmenidine monotherapy was shown to be efficient in controlling BP and in reducing LVH. The addition of perindopril to rilmenidine monotherapy proved to be effective and well tolerated in those patients who did not respond to rilmenidine alone.

[Isolated left ventricular noncompaction--first description in a Hungarian patient]

The case of a young female patient is presented in whom the typical diagnostic features of isolated ventricular noncompaction were recognized by two-dimensional echocardiography after 11 year follow-up. This rare cardiomyopathy is characterized by prominent trabeculations of the apex and the distal lateral wall of the left ventricle, systolic dysfunction, restrictive dysfunction, functional mitral and tricuspid insufficiency. Literature review reveals the underlying abnormality of the myocardial embryogenesis with a delayed presentation in adulthood and variable clinical manifestations ranging from long asymptomatic periods to malignant courses including sudden death, transplantation and decreased survival.

[Tissue Doppler echocardiography: a new technique to assess diastolic function]

Diastolic dysfunction and elevated filling pressure have important role in heart failure. Traditional Doppler echocardiography (DE) however is of limited value in the measurement of these variables. The objective of this study was the evaluation of a new technique, the pulsed tissue Doppler echocardiography of the lateral mitral anulus (PTDI) in diastolic function. 96 consecutive patients were included into the study who were in sinus rhythm, mitral valve disease was excluded and ejection fraction was either > or = 50% (50 patients) or < or = 40% (46 patients). DE technique was used to measure mitral E, A velocity, deceleration time (DT). Myocardial early diastolic (Ea), late diastolic (Aa) velocities were measured at the lateral mitral anulus by PTDI, and E/A, Ea/Aa, E/Ea ratios were calculated. Based on accepted DE criteria of diastolic dysfunction there were 19 normal subjects, 18 patients had abnormal relaxation, 8 had pseudonormalization pattern and 12 had restrictive dysfunction, the rest of patients did not fulfill these criteria.

RESULTS

PDTI indicated an association of diastolic dysfunction to systolic dysfunction, which could not be shown by DE. Myocardial Ea velocity was age-dependent only in patients with good systolic function, and it was less than 15 cm/s in all types of diastolic dysfunction. E/Ea ratio over 8 indicated elevated filling pressure, but it was related to E/A ratio only in cases of good systolic function. Importantly one third of cases could be classified into diastolic dysfunction patterns only using tissue Doppler.

CONCLUSIONS

Myocardial diastolic velocities can be easily measured by pulsed tissue Doppler technique at the lateral mitral anulus. Decreased early diastolic tissue velocity indicates diastolic dysfunction independently of its type, and it is generally associated to systolic dysfunction, independently of age. Pseudonormalization is defined as the combination of normal mitral inflow and decreased tissue diastolic velocity.

The role of thrombolysis in the management of left-sided prosthetic valve thrombosis: a study of 85 cases diagnosed by transesophageal echocardiography

BACKGROUND AND AIM OF THE STUDY

Treatment strategies of prosthetic valve thrombosis (PVT) are controversial. The aim of this study was to compare the efficacy and safety of thrombolysis, surgery and heparin therapy in patients with either obstructive or non-obstructive PVT.

METHODS

Between 1993 and 2000, 85 episodes of PVT were found (82 in the mitral position, three in the aortic) in 59 patients (22 males, 37 females; mean age 53 years; range: 28-80 years) by multiplane transesophageal echocardiography (TEE). Obstructive PVT was defined as restricted leaflet (occluder) motion with increased gradient, even if thrombus was not seen by TEE; non-obstructive PVT was considered as normal leaflet motion, irrespective of the gradients. Thrombolysis was given in 43 episodes (streptokinase, n = 37) by standard dosage protocols, surgery was performed in 20, and i.v. heparin was used in 22. Recurrence rate was calculated in 26 survivors of successful thrombolysis based on six months to six years follow up. Treatment with thrombolysis and heparin was monitored using TEE.

RESULTS

There were 54 cases of obstructive PVT and 31 cases of non-obstructive PVT. Anticoagulation was inadequate in 82% of cases. Thrombolysis was completely successful in 37 cases (86% success rate); in 27 of 32 patients with obstructive PVT (in both cases of aortic location), and in 10 of 11 non-obstructive PVT. Heparin was successful in only nine of 18 non-obstructive PVT, and in none of four obstructive cases. Nine patients died, all with obstructive PVT, and all but one were in NYHA class IV; two were treated by thrombolysis (5% mortality), six by surgery (30% mortality) and one with heparin (5% mortality). Complications of thrombolysis included two strokes and two transient ischemic attack episodes (9%), and bleeding in one case (2%). There were six complications due to heparin treatment: newly developed obstruction in five patients and stroke in one patient. Recurrence was diagnosed in eight episodes in six patients with obstructive PVT after successful thrombolysis (22%); rethrombolysis was successful in four of five cases.

CONCLUSION

Thrombolysis was shown to be superior to surgery in obstructive PVT, especially in NYHA class IV patients. Severe complications of thrombolysis were noted only in the critically ill. As heparin treatment appeared ineffective and unsafe for the treatment of PVT, thrombolysis appeared to be the optimal therapeutic choice in this condition.

Hippocampal rhythm generation: gamma-related theta-frequency resonance in CA3 interneurons

During different behavioral states different population activities are present in the hippocampal formation. These activities are not independent: sharp waves often occur together with high-frequency ripples, and gamma-frequency activity is usually superimposed on theta oscillations. There is both experimental and theoretical evidence supporting the notion that gamma oscillation is generated intrahippocampally, but there is no generally accepted view about the origin of theta waves. Precise timing of population bursts of pyramidal cells may be due to a synchronized external drive. Membrane potential oscillations recorded in the septum are unlikely to fulfill this purpose because they are not coherent enough. We investigated the prospects of an intrahippocampal mechanism supplying pyramidal cells with theta frequency periodic inhibition, by studying a model of a network of hippocampal inhibitory interneurons. As shown previously, interneulrons are capable of generating synchronized gamnma-requency action potential oscillations. Exciting the neurons by periodic current injection, the system could either be entrained in an oscillation with the frequency of the inducing current or exhibit in-phase periodic changes at the frequency of single cell (and network) activity. Simulations that used spatially inhomogeneous stimulus currents showed antiphase frequency changes across cells, which resulted in a periodic decrease in the synchrony of the network. As this periodic change in synchrony occurred in the theta frequency range, our network should be able to exhibit the theta-frequency weakening of inhibition of pyramidal cells, thus offering a possible mechanism for intrahippocampal theta generation.

[Evaluation of myocardial perfusion using intravenous contrast echocardiography]

The aim of the study was to assess the accuracy of rest myocardial contrast echocardiography (MCE) in detecting perfusion abnormalities after intravenous contrast administration in chronic coronary artery disease. In 21 patients (mean age 49 years) contrast agent was injected intravenously. ATL HDI 5000 ultrasound machine was used. Triggering every fifth cardiac cycle in end-systole apical 2-chamber, 3-chamber and 4-chamber views were used. All patients underwent thallium scintigraphy on the same day and coronary angiography was performed within 24 hours. Second harmonic imaging and power Doppler were used in assessing presence or absence of perfusion, localization and extent of perfusion defects, and their relation with wall motion. In the first group all the 13 patients after myocardial infarction had akinetic segments on echocardiography in accordance with the coronary occlusion detected by coronary angiography. In the second group none of the 8 patients without previous myocardial infarction had wall motion abnormality. Group I: dividing the left ventricle into 16 segments out of 208 segments 44 were akinetic. Perfusion defect was detected by MCE in 29 segments. In 12 segments with wall motion abnormality the normal myocardial perfusion was consistent with viable myocardium, 2 inferior akinetic segments could not be evaluated due to contrast attenuation and in one inferior segment MCE in contrast to the thallium scintigraphy showed no perfusion defect. Group II: good contrast effect was detected in all 128 segments except one inferior segment in which there was a fixed perfusion defect also by thallium scintigraphy and coronary angiography revealed occluded right coronary artery. In conclusion MCE and second harmonic triggered imaging is comparable with thallium scintigraphy in detecting fixed perfusion abnormalities. MCE may contribute to the detection of viable myocardium.

Effect of nitric oxide synthase inhibition on renal circulation and excretory function in anaesthetized rats

The effects of nitric oxide synthase (NOS) inhibition (effected using L-NAME, 14 mg (kg body mass (BM))(-1), administered intravenously) on systemic and renal circulation and renal excretory function has been investigated in anaesthetized Wistar rats subjected to one of two different degrees of isotonic extracellular (EC) volume expansion (40 and 60 ml x kg(-1) (240 min)(-1)). The administration of L-NAME resulted in an increase in mean arterial blood pressure and total peripheral vascular resistance (TPR), and a significant reduction in cardiac output (CO) and the kidney fraction of CO in both experimental groups. The total renal blood flow (RBF) dropped from 557 + 43.4 to 149 +/- 13.1 ml x min(-1) (100 g BM)(-1) and from 592 +/- 45.9 to 191 +/- 16.3 ml x min(-1) (100 g BM)(-1) in the 40 and 60 ml x kg(-1) (240 min)(-1) experimental volume expansion groups, respectively. A redistribution of the intrarenal circulation from the medulla of the kidney toward the cortex may have occurred. The NOS inhibition induced a significant decrease in the glomerular filtration rate (GFR; from 1.18 +/- 0.10 to 0.53 +/- 0.08 ml x min(-1) (100 g BM)(-1) and from 1.26 +/- 0.07 to 0.73 +/- 0.08 ml x min(-1) (100 g BM)(-1) in the 40 and 60 ml x kg(-1) (240 min)(-1) experimental volume expansion groups, respectively), and the filtration fraction increased. The urine excretion dropped in parallel with the GFR, while the reduction in sodium and potassium excretion was more marked than that of the GFR, raising the possibility of a direct effect on the kidney tubules. The difference in EC volume expansion (the calculated increases in the EC volume in the last 90 min were 1.30 and 5.44% in the two time control groups and 3.66 and 7.45% in the two L-NAME-treated groups) did not induce any significant modification of the L-NAME effect.

Measurement of left ventricular volumes and ejection fraction after intravenous contrast agent administration using standard echocardiographic equipment

The enhancement of endocardial border delineation using second harmonic imaging and contrast administration improves the measurement of ventricular volumes. In the majority of existing echocardiographic equipment, however, harmonic imaging is not yet available. The aim of this study was to assess the feasibility of the measurement of left ventricular volumes and ejection fraction after intravenous administration of the contrast agent Levovist using standard echocardiographic equipment and fundamental imaging modality. In 10 patients with good-quality two-dimensional echo imaging, 4 g (400 mg/mL concentration) of Levovist was injected intravenously. Hewlett-Packard Sonos 2000 ultrasound equipment without second harmonic imaging capability was used. To avoid the destruction of microbubbles, the echo machine was set to produce only one end-systolic and one end-diastolic frame in each cardiac cycle (dual triggering). Native and contrast imaging measurements of left ventricular volumes and ejection fractions calculated by modified Simpson's rule were compared in the fundamental mode. Intraobserver and interobserver variability values were assessed. End-diastolic volumes in native continuous and triggered mode and by contrast echo were 126 +/- 48, 121 +/- 46, and 130 +/- 50 mL, respectively (NS), whereas end-systolic volumes were 79 +/- 48, 76 +/- 45, and 79 +/- 46 mL, respectively (NS). Calculated ejection fraction using the three different imaging modalities were 0.41 +/- 0.16, 0.41 +/- 0.16, and 0.42 +/- 0.16 (NS). The intraobserver and interobserver reproducibility values were excellent in triggered mode. Standard echocardiographic equipment with fundamental imaging modality in the triggered mode is suitable for the measurement of left ventricular volumes after intravenous Levovist administration. In clinically difficult patients, contrast echocardiography in triggered mode may be applied even if echocardiographic equipment does not have harmonic imaging possibility.

[Ventricular septal defect in osteogenesis imperfecta]

A 20-year-old man with osteogenesis imperfecta type one and membranous ventricular septal defect is presented. The association of these two connective tissue abnormalities is rare. It is the first reported case in Hungary.

[Short- and long-term changes in left ventricular function after surgical correction of mitral regurgitation]

After surgical treatment of mitral regurgitation (MR) left ventricular dysfunction (LVD) can appear, which is an important predictive factor of long-term morbidity and mortality. The aim of our retrospective study was the assessment of left ventricular function (LVF) with M-mode echo measurement in the early and late postoperative period. Between 01. 01. 1992. and 31. 12. 1996. 70 patients with MR (29 men, 41 women, mean age 53.8 years) had at least three M-mode echoes: before surgery (I.), after surgery within 1 year (II.) and after the first postoperative year (mean 2.4 years) (III.). The patients were divided into subgroups: a) prosthetic valve replacement (MB) 58 patients, valvuloplasty (PL) 12 patients, b) coronary bypass grafting (C) 12 patients, no coronary disease (NC) 58 patients, c) chordal rupture (R) 24 patients, other etiology (NR) 46 patients. The evaluation of LVF was based on the ejection fraction (EF) calculated from the end-diastolic (Dd) and end-systolic (Ds) diameters on M-mode echo. Statistical analysis was made by paired and unpaired t test and with correlation analysis. The Dd decreased in the whole group (T) and in all subgroups in the II. and III. measurements compared to the I. (T: 58.9 vs. 52.6 vs. 53.2 mm; p < 0.0001, p < 0.0001). The Ds did not change in any group. In all groups except C the EF decreased at the II. measurement compared to the I. values (T: 57.7 vs. 47.8%, p < 0.0001; MB: 56.6 vs. 46.6%, p < 0.0001; PL: 62.8 vs. 53.8%, p = 0.05; NC: 59.6 vs. 48.3%, p < 0.0001; R: 61.5 vs. 50.4%, p < 0.0003; NR: 55.6 vs. 46.5% p = 0.0002), and it remained significantly lower in the III. measurement as well. At the III. measurement the EF was below 55% in all groups. In the groups T, MB, NC, NR the EF increased at the III. measurement compared to the II. (W: 47.8 vs. 51.3%, p = 0.002; PVR: 46.6 vs. 51.4%, p = 0.001; NC: 48.3 vs. 52.8%, p = 0.005; NR: 46.5 vs. 49.9%, p = 0.05). In the group C the I., II., III. EF values were not significantly different. There were 33 patients with preoperative EF more than 60%. In this group the EF decreased at the II. measurement, but the III. measurement showed normalization of the EF (67.03 vs. 52.58 vs. 59.27%, p < 0.0001, p < 0.01). There was no strong correlation between the preoperative EF, Ds and early or late postoperative EF (r = 0.54, r = -0.58; r = 0.62, r = -0.56). In patients operated for MR the postoperative EF is diminished independently on the preoperative EF, the operative technique or etiology. Left ventricular dysfunction concealed by the volume overload is unmasked by the decreased EF in the early postoperative period. LVD is partly reversible in the majority of the cases, however complete reversibility takes place only in cases with preoperative EF over 60%. Hence the operation of MR in patients with EF less than 60% is considered to be too late for the reversibility of LVD.

Single cell and population activities in cortical-like systems

Dynamics of single cells and large cell populations are the subject of investigation by using differently detailed models. Multicompartmental modeling techniques are used to systematically investigate the location-dependent effects of GABA-ergic inhibition on the firing patterns of hippocampal pyramidal cells. Appearance of stochastic resonance in a model of mitral and granule cells of the olfactory bulb is demonstrated by using a single-compartmental model approach. Spatial propagation of synchronized activities in hippocampal slices are studied by a model of large neural populations.

[Intravenous adenosine infusion in the assessment of coronary flow reserve in hypertension. Transesophageal Doppler echocardiographic study]

In hypertensive patients with normal coronary angiography typical chest pain may be caused by microvascular coronary artery disease. This can be confirmed by decreased coronary flow reserve (CFR). Adenosine test with transesophageal echocardiography was chosen for the measurement of CFR. There are only few reports in the literature which utilized this test. The purpose of this study was primarily to further elucidate some technical aspects and to evaluate CFR in hypertensive patients with angina, positive stress test and normal coronary angiography. Out of 12 such consecutive patients the adenosine test was successful in 11. Adenosine was given in 140 mcg/kg/min dose as a 5 minute continuous infusion. Mean coronary flow velocity (Vm), CFR, baseline coronary flow resistance (CVR) and maximal coronary dilation (CRR) in the left anterior descending artery were measured and calculated by multiplane transesophageal Doppler echocardiography. There was a 43% increase of heart rate and a 7% decrease of systolic blood pressure. Baseline Vm was 36 +/- 16 cm/s, CFR 2.4 +/- 0.4, baseline CVR was 2.8 +/- 1.0 mmHg/s/an, CRR was 2.4 +/- 0.4. Left main coronary dimension did not change. There was no important side effect. While baseline Vm was similar to normal values in the literature, CFR and CRR were decreased compared to normals. There was no correlation between baseline Vm or heart rate and CFR but a direct correlation was found between baseline CVR and CRR (r = 0.54). Peak effect of adenosine was achieved at 3-5 minutes.

CONCLUSIONS

Adenosine-TEE infusion test is a safe and easy to perform technique to assess CFR in hypertensive patients. In hypertensive patients with documented ischemia and normal coronary angiography the coronary flow reserve is decreased.